# Forced Air: Nat Gas Furnace or Hydronic Air Handler



## WhatRnsdownhill (Jan 13, 2016)

go with the hydronic coil in the air handler..best option all way around..


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## Bud9051 (Nov 11, 2015)

Just completing the process of selecting a boiler for an existing home in Maine that is a 2200 ft² ranch with a 1250 ft² basement. Part of the ranch has 400 ft² of slab with radiant heat. Well built home, but not as well insulated as spray foam, and we struggled to get a boiler small enough to not be an elephant. With what you list as radiant off of the boiler, it will have a huge amount of excess capacity. If we ignore most of the basement and use 25 btu per ft² you would need 55,000 total. You are talking two heating units, way overkill.

Is your mechanical designer going to do a Manual J calculation and is he the one selling the two systems?? If you note a hint of caution there it was intentional.

Is this new construction or remodel of an existing building, what stype and age?

Bud


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## Vanner (Oct 11, 2015)

So far we have just been talking about options. He is doing full set of 'computerized' calcs. I assume that will be a good analysis. 

He's taken in a lot of information so I'll know shortly. 

I've seen a few people with gas forced and combi boiler for radiant and DHW. Some have argued that gas and boiler give you heat should one go. 


Van G


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## supers05 (May 23, 2015)

Backup is always nice, but I'd go with the hydronic coil. You already have the boiler. (I assume that your engineer has already calculated that you have the excess capacity) The more parts you have, the more that can break and cost in repairs. 

PS. For your comparisons: I'm also near Toronto, with a 900ish sq. Ft detached home, at least 60 years old. Original insulation/plaster/brick, decade old windows. Almost never use the second stage of the 40kbtu 2 stage furnace, recently installed. (even at the recent -26*C and strong winds)

Cheers!


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## Vanner (Oct 11, 2015)

Interesting. We are adding onto a 1950's semi which is double double brick wall with cavity. Addition will be about 60% of the total space. 


Van G


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## Bud9051 (Nov 11, 2015)

If you have a gas boiler now, what size is it?
I audited one well insulated home that had radiant heat in the basement and the owner was one who liked to track his heat use. He said his radiant floor in the basement almost never came on. His is an open unfinished basement (insulation on outside of foundation) so the boiler gives off more than enough heat for down there.

Bud


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## Vanner (Oct 11, 2015)

No system in place right now. It will be all new system and well insulated including under the slab before we pour. 


Van G


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## user_12345a (Nov 23, 2014)

Air handler is the best choice if you're getting it anyhow.

You can also get an indirect hot water tank and skip the water heater. Pro is that it's more efficient most of the time, especially with a condensing boiler. Con is that it may not be very efficient to have a 80 to 100 000 btu boiler come on in short cycling during the summer to keep water hot. Increases wear too, having to fire the boiler year round.

Do not let your designer treat the tight, high r-value spray foamed house as a regular house. The heat loss will be very low for the square footage, could even be under 40 000 btu/hr. A/c will be less than 1 ton per 1000 sq ft. This is under the assumption that the original double brick structure will be insulated as well. *You're splitting hairs, spending extra money on spray foam for the addition if the original house is to remain leaky and uninsulated.*

Look into a HRV.


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## Vanner (Oct 11, 2015)

Spray foam on all exterior walls and flat roof, blow in loose in the existing attic, and insulate/vapour before new slabs poured. 

Will discuss this with him tomorrow and post the calc when I have them. 

Going with LifeBreath HRV, likely a simplified setup as existing framing is 2x8 timber. Would be bulk heads everywhere. 


Van G


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## beenthere (Oct 11, 2008)

Whether to use the boiler or a separate gas furnace, depends on what type of boiler you are looking at. A high efficiency condensing boiler use on a hydronic coil will need to go above 140°F when the hydronic coil is heating. Unless you really over size the coil. 

The efficiency of the boiler drops as you increase water temp. So you need to decide what you want to trade off on. High efficiency. Or convenience(1 zone will always work as long as you have gas and electric) and cost of 2 systems.

Next, on a spray foam house. You will need mechanical ventilation. So how are you addressing that. Most add it into the duct work. With a hydrocoil, you would also want an antifreeze stat in case the boiler failed, so you don't freeze the hydrocoil and burst it.


PS: If I wnet with a hydrocoil, I would want a heat pump instead of straight A/C in case the boiler failed.


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## Vanner (Oct 11, 2015)

Setting up call with mech designer but his initial reply:

The gas furnace will have better features and will give you a second heat source in case the boiler goes down. The hydronic air handler will be cheaper to buy and will run off the boiler's hot water so we would need to upsize the boiler to be able to handle the extra load. The airhandler will not have the extra features of multi stage or modulating fan.


Van G


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## Bud9051 (Nov 11, 2015)

Hi Van
I'm beginning to question the capability of your mech guy.
"Radiant is only in basement slab, main floor mudroom, and 2 upstairs bathrooms." That is a very small load unless you are heating other areas and even if that, he says up size the boiler to handle the hydronic air handler.

Not making sense here. Installing a second heating system just to have back-up would be an expensive approach.

I'll wait to hear what his final heat loss numbers and what he is recommending for equipment.

Bud


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## Vanner (Oct 11, 2015)

Concerning! 

Seems like a straight shooting guy. He was more money than the other 2 designers. 

Basement is 1123 sqft inside dimensions less areas that won't use it like mech room, stair foot print. 

Add another 180 sqft for the other rooms. 


Van G


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## beenthere (Oct 11, 2008)

You can get an air handler with a VS blower. Wired right, you can have it move a lower CFM when its mild outside. And a higher CFM when its real cold outside.

What size boiler is he intending to use if you get a furnace. What will be the total sq foot of hated space?


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## user_12345a (Nov 23, 2014)

Will the boiler be heating the dhw?

You can get a water heater designed for heating and kill two birds with one stone. Would be cheaper than getting a boiler and water heater, or boiler with direct tank.

Truth be told the hydro-air won't be as energy efficient as a gas furnace. 

Even with a condensing boiler, it needs a low water temperature to actually run in the 90%+ range. The warmer the return water the less efficient the boiler becomes.

With furnaces the return air temp is room temperature, so the secondary heat exchanger's heat transfer to better on a furnace vs boiler. Exhaust from a high efficiency furnace can be cooler than the returning water to a boiler, especially with the air handler running at a low fan speed.


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## beenthere (Oct 11, 2008)

user_12345a said:


> Truth be told the hydro-air won't be as energy efficient as a gas furnace.
> 
> Even with a condensing boiler, it needs a low water temperature to actually run in the 90%+ range. The warmer the return water the less efficient the boiler becomes.


Heat pump with hydrocoil is more efficient then a gas furnace.


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## user_12345a (Nov 23, 2014)

Run a heatpump in Ontario most of the winter and it'll burn a hole in your wallet.

Efficient? Maybe. Cost effective? No.


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## user_12345a (Nov 23, 2014)

...also central air style heatpumps are rare in Toronto. Which means finding a tech to work on one could be a challenge. The lack of capacity below freezing, high electricity costs make them unattractive.

In areas with no natural gas or cheap electricity, the heatpump is worth considering.


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## beenthere (Oct 11, 2008)

user_12345a said:


> Run a heatpump in Ontario most of the winter and it'll burn a hole in your wallet.
> 
> Efficient? Maybe. Cost effective? No.


I thought Ontario had TOU billing. If so. Then a heat pump used off peak would be very cost effective.


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## user_12345a (Nov 23, 2014)

Here are the prices:

*Off peak*
8.3 ¢/kWh
CURRENT PRICE
*MID-PEAK*
12.8 ¢/kWh

*ON-PEAK*
17.5 ¢/kWh

Add another 3-6 cents per kwh, for all the other charges, add tax.


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## beenthere (Oct 11, 2008)

user_12345a said:


> Here are the prices:
> 
> *Off peak*
> 8.3 ¢/kWh
> ...


At 12.3(off peak with 4 cents added to it) cents per KWH, for off peak. Straight electric resistance heat would cost $36.04 per 1,000,000 BTUs of delivered heat. A heat pump at an average COP of 2, would cost $ 18.02, and at an average COP of 2.5 it would cost $14.42

I didn't break it down for the milder temps like when its 40 degrees outside, and the heat pump is at a COP of 3 and higher.

So whats the natural gas rate there.


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## user_12345a (Nov 23, 2014)

https://www.enbridgegas.com/homes/a...l-gas-rates/purchasing-gas-from-enbridge.aspx

1 m3 = maybe 35 500 BTU or so here if I remember right.


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## beenthere (Oct 11, 2008)

At a COP of 3.2. Its about the same(if I converted everything right). Depending on how much gas is used, as the delivery to you rate decreases with an increase in gas usage.


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## Bud9051 (Nov 11, 2015)

Van, still looking for the design specifications.
As for the heat required for the basement it is figured on the heat loss to the outside and the floor to soil below amounts to very little, unless there is water flowing below the slab. The majority of the loss is through the exposed concrete at the top. Assuming that area is insulated and air sealed its total heat load is very low, certainly not enough to justify a second heating unit.

Bud


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## supers05 (May 23, 2015)

beenthere said:


> At a COP of 3.2. Its about the same(if I converted everything right). Depending on how much gas is used, as the delivery to you rate decreases with an increase in gas usage.


Actual Electricity is about half the price is the bill here. My calculations are closer to a break even COP of 3.9 or so. A heat pump on a water loop is actually fairly efficient and is much more popular in Toronto then user thinks. (yes, and more then enough technicians to have competition for fractional up to 10 ton water source heat pumps. I've probably fixed several hundred by now) It's common for offices towers and hotels. The boilers can run a supply in the 80-85*F range, with the heat pumps achieving well into the higher COP levels. Very efficient in the shoulder seasons. Air source heat pumps aren't too bad, as long as you don't use resistance backup heat. (those bills get high) 

Cheers!


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## Vanner (Oct 11, 2015)

Bud, I'll have calcs mid next week.

Heat pump setup expensive? Watched a few overviews of the system and seems like a lot of things to go wrong.

Had another chat with designer (who is open to designing whatever system I ultimately want) but felt a good modulating gas furnace is less expensive to purchase and operate if you compare it to same quality/features of a hydronic air handler setup like Lennox or Viessmann.

Electricity is expensive right now but we'll all have access to greatly reduced electricity in the next 5 yrs as solar, storage, and micro grid exchanges become the norm.


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## user_12345a (Nov 23, 2014)

> Had another chat with designer (who is open to designing whatever system I ultimately want) but felt a good modulating gas furnace is less expensive to purchase and operate if you compare it to same quality/features of a hydronic air handler setup like Lennox or Viessmann.


 To get the full benefit of most mod furnaces, you need a expensive specialized communicating t-stat. Be sure your designer specs it out, otherwise you won't get what you're paying for.

The auto-modulate algorithm on the board doesn't know what temperature the house is, if the temp is going up or down; only if there's a demand for heat or not. 

 Most if not all just keep on ramping up until the call for heat ends, then the furnace shuts off. 

The entire idea is to get the heat output to track heat loss. A lot of them time it will only need to run at the minimum firing rate.


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## Vanner (Oct 11, 2015)

Have access to Ecobee3 thermo through a friend. Was looking to use this as it integrates well with the SmartThings system. 


Van G


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## user_12345a (Nov 23, 2014)

A high end non-communicating t-stat can stage a furnace, but the manufacturer's communicating one is needed to get output to track heat loss.

Ecobee won't do it.

York is the only manufacturer I know of which produces a mod furnace that does a good job on even a single stage t-stat.

I think trane, rheem, maybe a couple of others (not goodman or lennox, that's for sure) can do decently with a regular 2-stage stat, dropping down to 40% on a call for first stage and slowly ramping up when there's a call for both stages. 

The key is the ability to modulate down -> many of them just keep on modulating up until the demand for heat is finished. Total waste of money IMO.


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## supers05 (May 23, 2015)

I have the ecobee with a 2 stage. I usually don't recommend modulating to my customers, unless they request it specifically. There's more parts to go wrong, and most parts are more expensive and less available locally. I tend to sell 2 stage gas heating. (Unless it's a very large job that requires more) The parts are always available, relatively cheaply. (I let others be the guinea pigs) 

We've installed a few hydronic air handlers. Most of them because there wasn't space for multiple exhaust vents, and little floor space. Instant HW boiler was used for those. (usually navian modulating. Not much to check or fix, it's just replacing extensive parts on those when things stop working) The rest were because the hot water was already available. 


The radiant floors are really nice, but the heat transfer is fairly slow. (especially when the floor temp is kept at bare foot comfortable levels) Very smooth and comfortable heating source. The catch is that the boiler would be cycling quite often unless it's fairly small or you put a larger load on it. This is why I'd recommend the hydronic coil. You'll get most of the efficiency out of it, and it would be comfortable. Use an outdoor reset controller to control the temp of the loop, it'll be much more efficient during the shoulder seasons. (Your domestic hot water can be heated this way too, if that tickles your fancy) 


Cheers!


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## Vanner (Oct 11, 2015)

Mech room is drawn to be 7'x7' w/ just under 8' ceiling. 

No problem to get a few vents out a near wall away from operable windows. 

What is the outdoor reset controller?

How would I pull DHW from this as well?


Van G


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## user_12345a (Nov 23, 2014)

> What is the outdoor reset controller?


 It's a device that adjusts the water temperature as the outdoor temperature changes.

Normally the aqua-stat in the boiler is set to the required temp for the most extreme conditions.

Makes the boiler more efficient by reducing the water temperature in mild weather; get better heat transfer that way. 

The benefit of a hot water reset may not be so great if you get a mid efficiency boiler since there's a minimum water temp needed to prevent damage. (it won't be below 140f, that's for sure)

If you get a condensing boiler, there's no minimum to my limited knowledge. The lower the return water temp the more "condensing" happens.

At high return water temperatures the condensing boiler doesn't save much compared to a conventional one. Without the reset the condensing boiler is a waste of money:


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## supers05 (May 23, 2015)

The outdoor reset controller is included in some upper end boilers, and is available as a separate unit. It is a special "thermostat" that controls the temperature of the water based on the temperature of outside. The colder outside is, the hotter the water. This allows for cooler water during warmer periods, making things more comfortable, preventing overshooting the temperature in the rooms, and allowing the boiler to condense. 


For connecting hot water, would depend on the boiler/tank on the actual connections. Boilers like the navian high end line have 2 pairs of connections. One for instant hot water, and the other for hydronic heat. Other types only have 1 pair, so you have to run the boiler temp up to heat the DHW. It then uses the tank has a large thermal mass to prevent short cycling as it heats the house during low demand periods. Typically this world use a heat exchanger to separate the boiler and the DHW tank. (The tank water should always be above 125*F for health reasons) Another method, is to only use a condensing hot water tank, and with a heat exchanger, pull heat out of it, zones call for it. (this doesn't need the outdoor reset controller as much, but the tank temp may have to be above 140-150*F during the winter) 

Cheers!


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## user_12345a (Nov 23, 2014)

> (this doesn't need the outdoor reset controller as much, but the tank temp may have to be above 140-150*F during the winter)


 Won't be very efficient at that temp, eh?


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## Vanner (Oct 11, 2015)

Confused as hell. Clearly there is more than 1 way to skin this cat. 

Hope to have calc's up mid week. 


Van G


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## supers05 (May 23, 2015)

Vanner said:


> Confused as hell. Clearly there is more than 1 way to skin this cat.
> 
> Hope to have calc's up mid week.
> 
> ...


Yes lots of options. They all work. 

At 140*F water temp, your still condensing, just not as much as 60*f (standard for HHV). So instead of 97% it'll be closer to 92-94%.

Ref, and some interesting reading: https://en.wikipedia.org/wiki/Condensing_boiler?wprov=sfla1

Cheers!


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## Vanner (Oct 11, 2015)

Good read. Thanks for the link. So the question is can a condensing boiler be used for radiant, forced air, and DHW and still keep the return water at optimal temps? Even in shoulder months or summer?


Van G


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## user_12345a (Nov 23, 2014)

Limited by the needs of the use that needs the hottest water I would think.

Get all the heat from one boiler and if the boiler breaks, you have nothing. 

You're looking at thousands of dollars more to have a unconventional setup with some in floor heat, condensing boiler. More to go wrong.


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## beenthere (Oct 11, 2008)

Vanner said:


> Good read. Thanks for the link. So the question is can a condensing boiler be used for radiant, forced air, and DHW and still keep the return water at optimal temps? Even in shoulder months or summer?
> 
> 
> Van G


Weil McLain Ultras are still 92% efficient at temps above 120, and below 160.

So yes, you can use a high efficiency boiler for all 3 uses.


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## supers05 (May 23, 2015)

It's hard to see, as the picture didn't come out like I wanted... 

The cpvc stacks on the right are fully condensing, with a return between 120*f to 140*f. It's DHW, so it can be lower, but the storage tank is big enough to prevent it. Measured burner efficiency at least 95%

The Stainless Steel stacks in the back left are near condensing boilers with secondary heat exchangers. Return between 85*F - 150*F depending on the outdoor temperature. (outdoor reset) When it's warm outside, (40*f today) the loop was about 117*f. When it's cold outside, (0*f or below) The loop will be around 180*f. When outside is above 60*f the boilers turn off completely, regardless of loop temp. This heats air handler coils to a few hundred suites. Measured burner efficiency between 87-97%

The Stainless Steel stacks in the front left are similar near condensing, but without secondaries. They shouldn't ever condense during normal operation. The loop temp is kept constant for pool/whirlpool/pool fresh air heating, more DHW indirect heating (via a few heat exchangers), building fresh air heating (very large water coils in air handlers that you can drive a van into), and select coil heaters and baseboards. (common and mechanical areas). We call this the primary loop. It's heated even in the summer. The thermal mass of the DHW tanks prevent short cycling, and very carefully sizing the boilers to the lowest demand. (20% of a single boiler) Measured burner efficiency of around 86-87%. (The originals were all around 60-65%, so it's still a significant improvement) 

They are all networked to work in teams, but that's not so important for your house, unless you use a 2 boiler system for a bit of redundancy. If you do, sizing will be critical, and fully modulating is recommended. (Camus, and Lochinvar, Navian, and a few others have nice built in controls that allow for networking and outdoor reset. Even on their smallest boilers) 


A simple 2 stage furnace, or single stage condensing hot water tank will do the job too. They will be easier to troubleshoot, both professionally and on here, if you go DIY. The parts can be easier to find. (We have a Camus, and another supplier locally that stock everything for Navian and Camus. So not really anything different. Lockinvar is difficult to get parts here.) However, The reliability and expected life of the units are virtually identical. (The install makes or breaks it) 

Cheers!


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## Vanner (Oct 11, 2015)

Wow, my first mechanical pr0n! Thanks for laying out different systems. Where is that bldg?

Install of mechanical system is not something I would tackle myself. Too important. I'll do the pex runs in the floors and maybe lend a hand installing/sealing ducts. Doing all this legwork upfront so we end up with a good system to make our home comfortable for the long term and aide me in finding a good installer.


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## supers05 (May 23, 2015)

Close to Toronto. That's Lake Ontario in the background. It was a beautiful day today. 

Cheers!


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## Vanner (Oct 11, 2015)

Quick thought, if doing a simplified HRV, how is fresh air cycled when forced air system isn't being used? Can the HRV call the upon the blower for circulation?


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## user_12345a (Nov 23, 2014)

Sure, the hrv could be interlocked to run the fan.

Overall it's a foolish way to install an hrv, increases electricity use for ventilation drastically.

You'll be better off taking stale air directly from the house rather than return; can run the hrv without the furnace fan that way.


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## Vanner (Oct 11, 2015)

To be effective, HRV needs load calc and dedicated ducting?

Just not sure how I can make that ducting disappear into framing. 

Does it have to be in the mechanical room? Or could it be upstairs in closet?


Van G


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## supers05 (May 23, 2015)

Many people run their indoor fan often anyways to prevent stratification and stale air. It's not a terrible idea to use the furnace for the HRV in these cases. They interlock the HRV to the fan, so that when a normal "circulate" command from the stat is present, the HRV runs. 

However, taking air from any other place in the house would be slightly more effective if you don't plan on anyways using the fan. Quite a few houses here (including new builds) just use exhaust fans for this purpose. For better or for worse. It's just as effective, but causes a higher negative pressure in the house. This is only noticeable to gas burning equipment using only an exhaust. (High efficiency appliances are more immune to this then natural draft ones) 

Cheers!


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## Vanner (Oct 11, 2015)

I thought that made sense, use the blower on the furnace for circulation - it will be in use 8 months of the year?

Water Closets, bathrooms, and Nat Gas range will all have exhaust fans (we cook more than most). How do we design for these exhaust only parts?

The months that the furnace blower isn't being used (May, June, Sept, Oct?) the windows are likely to be open. Is that the right way to think about it?


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## Bud9051 (Nov 11, 2015)

Varner, without reading the entire thread, quick scan, I haven't see the results of the heat loss. Part of that heat loss will be the anticipated natural air exchange which, I doubt will be low enough to necessitate the HRV.

Some quick numbers. Your home with basement is 3,300. Allowing 8' per floor that's 26,400 cubic feet of volume. A very optimistic air sealing effort for an existing home would achieve 0.2 ACH natural. That's 0.2 x 26,400 ft³ or 5,280 ft³ per hour. Divide by 60 and we have 88 CFM. Now, that air flow isn't happening all of the time and when the wind is blowing or it's cold outside that number is a lot higher. 88 is the average over a long period of time. A blower door test after the renovations are complete would tell us what you ended up with, but 0.2 would be a really tight house.

Point her is, you will have a natural air exchange and all you need to consider is increasing that slightly. If you go for the HRV, target exhausting bad air from bad areas, under sinks, bathrooms, laundry areas, and maybe the basement. Return the fresh air to the living spaces where people can enjoy it.

But, where are those heat loss numbers . Did I miss them?

Bud


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## Vanner (Oct 11, 2015)

Numbers are delayed until Friday. Fingers crossed!

So a dedicated HRV could be located outside the mechanical room?


Van G


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## user_12345a (Nov 23, 2014)

Can put HRV where you want.

Simplest would be in the mechanical room, taking air from the area above, dumping fresh air into the return air duct or drop.

If you want to get fancy, you could pull stale air from a bathroom and have the hrv controlled by a push button.

There are many ways to control an HRV depending on the brand; best and simplest is a humidistat style control from the manufacturer which just cycles it on and off to control moisture. An additional control can be used to switch it on as needed if the air seems stale. If you run the unit continuously even on low speed, the house will be over-ventilated. Even with heat recovery, air exchange is a net energy looser so - don't control the air exchange unit properly and it will cost you more than cracking a window open.


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## user_12345a (Nov 23, 2014)

> Varner, without reading the entire thread, quick scan, I haven't see the results of the heat loss. Part of that heat loss will be the anticipated natural air exchange which, I doubt will be low enough to necessitate the HRV.


 A spray foamed house will need an HRV.
---------------------------------------
I don't think the added heat loss of the hrv is very critical for sizing, because when it's -25c or whatever, the hrv shouldn't be running anyhow. Temperature difference between inside and out drives the stack effect. 

The furnace will have a safety factor be default, and probably a large one; even with a 40 000 btu heat loss for example, a lot of designers will be tempted to go with a 60000+ btu/hr furnace in a 2200*+ sq ft house out of fear of complaints or getting sued. Personally I would get the smallest furnace which would maintain setpoint in extreme conditions to maximize comfort, but the guys in this business will look after their own interests. 

*In case the guy(s) doing stuff in the west claim I'm full of crap quoting heat loss numbers like that, Toronto much much warmer, plus a spray foamed house will have abnormally low heat loss.

You're protected a bit from gross oversizing because the load calcs are needed to get the permits. If you were doing a straight change-out with no permits, you would be at much greater risk of falling victim to "clown salesman" rule of thumb sizing.


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## user_12345a (Nov 23, 2014)

*In case the guy(s) doing stuff in the west claim I'm full of crap quoting heat loss numbers like that, Toronto is much warmer, plus a spray foamed house will have abnormally low heat loss. I've done calcs before plus have a feel what real heat loss is based on runtime. Contractors putting 75, 80, 90k+ 95% furnaces in insulated 2000 sq ft houses are nuts.


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## supers05 (May 23, 2015)

Relax, the vast majority of those that have "oversized" furnaces are quite happy with them. When people are happy, you get paid well, period. If putting in 40,000 btu furnaces made those same people happy, they would have been put in. Remember most of it is about perception. A heat pump is still heating even with a supply of 85*F, even when people complain of cold drafts. If it takes a furnace all day to recover from a weekend setback, they aren't happy either. Personally, for my house, I use a 40,000, and I'm happy with it. However, I know it's limitations, and save in gas. Is it more efficient to size tightly? Yes. Is it more comfortable? Mostly, but perceptions are unique. Does it deteriorate lifespan much? Not significantly, since most units last well past 10 years. (Unless the ductwork is undersized too) 

OP: Usually the normal stack effect and exhaust fans and normal movement of people are enough to keep it ventilated. The engineer will give you the finer details though, since every case is different. 

Cheers!


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## user_12345a (Nov 23, 2014)

HRV can be added later if needed, if space is there and rough in (like wire for the control) is put in before hand.

It's costly to put in, at least around two grand.


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## Vanner (Oct 11, 2015)

Have calc's for Forced Air and Radiant.

How should I share?

Couldn't get PDF small enough to upload (20 pages/1.38 MB) so can do them in a series of images (ex below)

OR

Another idea to share the PDF (dropbox, Google Drive)?

OR

Just PM and I can email.


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## user_12345a (Nov 23, 2014)

You can split the PDFs if you have a pdf writer installed; re-print as pdf, do half the document at a time.

Dropbox is also good if you can do it publicly and post a link. If memory serves, there's a public folder part.


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## Vanner (Oct 11, 2015)

user_12345a said:


> You can split the PDFs if you have a pdf writer installed; re-print as pdf, do half the document at a time.
> 
> Dropbox is also good if you can do it publicly and post a link. If memory serves, there's a public folder part.


Limited to 100KB/PDF


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## user_12345a (Nov 23, 2014)

You've got pm.


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## user_12345a (Nov 23, 2014)

Got it.

So they didn't include the hrv in the calcs.

The only thing that bothers me is the 4.55 ACH for a spray foamed house. 

Spray foamed homes are tight -> very tight. 4.55 ach is what a 1980s or early to mid 90s house would get during a blower door test.

Have a more realistic value of 3 and that knocks a few thousand btus/hr off the heat loss.


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## user_12345a (Nov 23, 2014)

With respect to the original question now that I've seen the calcs:

44k loss and 27k gain...

I think it's a terrible idea to go with a boiler and furnace. Even the smallest boiler will be short cycling like crazy for the small amount of radiant that you'll have.

Either do a condensing boiler which provides heat for everything, or no boiler. I don't like the idea of losing all forms of heat if one unit breaks down. ..if the unit happens to be a rare condensing boiler, it will be harder to find someone to fix it - will cost more.

If I was in your shoes, I would just go with a traditional forced air system that can heat the entire house.

Furnaces tend to come in around 40,60,80k +/- btu etc . If your designer doesn't want to cut it fine, look at 2-stage 60k, controlled by a 2-stage thermostat -> Can have the extra capacity if needed but get very comfortable, quiet heat of a properly sized unit most of the time. Best of both worlds.



Do radiant as an add-on which you don't depend on; tank water heater designed for heating as well will handle that easily. With the tank short cycling won't be much of a problem since there would be a buffer.


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## Vanner (Oct 11, 2015)

Here are some of the Forced Air Heat/Loss calc's. Can't get a bunch of the PDF's below 100 KB.


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## Vanner (Oct 11, 2015)

Some more. PM if you want me to send the full PDF to you.


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## Vanner (Oct 11, 2015)

Last few of the ones that I'm able to u/l.


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## Vanner (Oct 11, 2015)

ACH being that high, would this be related to the large amount of glazing?

Also, R-2.9 seems low for modern double pane window. 


Van G


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## beenthere (Oct 11, 2008)

ACH natual is how leaky the house is.


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## user_12345a (Nov 23, 2014)

> ACH being that high, would this be related to the large amount of glazing?


 No. ACH must be estimated before construction takes place; if you putting a new hvac system into an existing house, not doing an addition + spray foam leakage could be estimated using a blower door.

ACH from the blower door test is used to calculate ACH natural, which is still only a ballpark figure. They take ACH with the house at a certain pressure (think it's -50 Pascal's) , then divide by an n-factor.

The load calc is far from 100% accurate and garbage in = garbage out. 

---------------------------------------------
"Also, R-2.9 seems low for modern double pane window."

Even the best windows have low R-values relative to walls.

Double pane standard is R1.8 to R-2, low-e is closer to R3. You can possibly spend a lot more money and get triple glazed, R4+. The law of diminishing returns applies though. 

To determine if the value is correct, you would have to get the U and solar heat gain coefficient values from the window manufacturer.


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## Vanner (Oct 11, 2015)

Working through duct layouts to minimize bulkheads in basement. 

Any issue with running 6" tall x 24" wide trunk on ceiling and taking runs off the top and into the joists?


Van G


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## user_12345a (Nov 23, 2014)

> Any issue with running 6" tall x 24" wide trunk on ceiling and taking runs off the top and into the joists?


Ask your designer.

The shorter the trunk, the wider it must be.

You can't just have a design with 8" pipe and drop it down to 6".

The designer has the friction rate and gets the width based on a fixed height. There are paper ductilators but most probably have the software do it.


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## Vanner (Oct 11, 2015)

Designer is working things out, I'm just trying to figure out if shorter/wider ducts work as well, or does the added surface area cause issues with noise, heat loss, friction....


Van G


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## user_12345a (Nov 23, 2014)

A 8 x 24 duct at 0.1" per 100 ft will flow 1175 cfm. The friction rate is simply for the sake of this example, you would have to ask your designer.

If you wanted a 6" high duct, it would have to be 35.5" to flow the same amount of air. The bulkhead would become very wide - not necessarily much better.

The friction rate, or pressure drop is set in stone for a given trunk. *The dimensions are variable; start changing the dimensions of an existing design and you'll end up with a very poorly performing system.*

Mechanical stuff must be designed; there are no good rules of thumb. With plumbing, electrical, have it done to code and you're good to go for the most part. On the other hand, a code approved system in new construction could perform horribly. 

*my biased opinion:*
Good interior design is done at the expense of function, especially hvac. It used to be that basements were utility/storage areas, then people started finishing 'em with drop ceilings. Now it's gone too far, making basements like any other part of the house - makes access to anything a pain in the neck.


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## beenthere (Oct 11, 2008)

The wider the duct, the further from the edge the take off has to be placed. As air doesn't travel in the corner of the duct very well. 

I'd stay with a boiler for the forced air. Probably an 80,000 BTU mod/con boiler. Let it do the heating and domestic hot water. An 80,000 mod/con should be able to modulate down to 16,000 BTU input. Also provide a good volume of domestic hot water using an indirect water heater.


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## Vanner (Oct 11, 2015)

Another interesting thought while reading about pool equipment - heat exchanger's for your pool (NTI makes one). Run from our mech room to pool pump should be about 60'.

Would the pool heating take the place of the radiant floor and forced air load during the summer months? Sets the system up to be on for longer periods with lower input temp to get max efficiency out of the boiler?

DHW remains relatively constant through the whole year.

Would the Viessmann 200 series boilers (4 loops) do everything I need without additional controllers

Down the road we can mix solar into the game if everything is based on hydronic.


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## supers05 (May 23, 2015)

That one will work just fine. Personally I've seen these work, and they are excellent machines too. Navien NCB-E Combi-boiler. For you, I'd think that the 150 size is right, but the 180 won't hurt either. (150 is 60MBTU heating, with the 180 being 80)

The pool side of it is an option, but do you have a heater now? They can be quite large in capacity. It depends on how quick do you want to heat the pool, The size and the lowest air temp you're wanting to run it at. A quick search will pop up heaters at above 200,000 btu. (not exactly a slap on option) 

Cheers!

PS. A good pool heater explanation: 
http://www.poolcenter.com/heatersWhatSize

Pool heater calculator:
http://www.jandy.com/en/calculators/pool-heater-sizing


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## Vanner (Oct 11, 2015)

Yeah, the pool heat exchange seemed unrealistic. 

Got a quick price on the Viessmann 200 boiler - holy hell they are $$$. 

Navies and Trinity good product?


Van G


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## supers05 (May 23, 2015)

Seen a few trinity's installed but never worked on one. They seem to hold their own. They both offer combi versions. (built in indirect DHW exchanger) 

Cheers!


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## user_12345a (Nov 23, 2014)

> Got a quick price on the Viessmann 200 boiler - holy hell they are $$$.


Look at repair costs too; there's no point of getting a modulating boiler to save money on utilities if certain repairs cost nearly $1000.


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## Vanner (Oct 11, 2015)

Cleaning the cob webs off this one. We just poured our floors this past weekend with 5 loops laid into Amvic Ampex panels. Purchased a Watts 10 loop manifold so we're considering adding radiant to the kitchen/living room (open great room sort of thing). Floor space once you subtract cabinets and island is 370 sqft. 

Is it effective to run the loop(s) under the subfloor using the radiant aluminum tracks? Using a channeled board on top of current subfloor + flooring would be a nightmare on flooring transitions.

We've decided to use the NTI VMax Plus as the sole heat source (radiant, forced air, dhw).


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## user_12345a (Nov 23, 2014)

thanks for the followup.

so, hydro-air coil?

are u putting a/c in?


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## Vanner (Oct 11, 2015)

Yes, hydro air coil and a/c coil. Mech Designer spec 2.5 tonnes for cooling. 

Air handler being looked at are Life Breath and ADP

I should also add that we are considering dropping the HRV since we cook, shower, and go outside a lot! Will be using batts instead of spray foam on addition due to cost (still get R24) but spraying existing walls plus headers and problem spots.


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## supers05 (May 23, 2015)

I just laid down that stuff just 2 weeks ago for another customer. Interesting stuff. I didn't do the pour though. I wouldn't drop the HRV since you do go outside often. It means that you like the outdoors and don't like the stuffiness of the indoors. (I keep my windows open as much as possible, but as you know in our climate that's only a possibility a few months of the year some times. This year there is no fall....or spring) 

Cheers!


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## beenthere (Oct 11, 2008)

How big/how many CFM is the exhaust fan for the kitchen.


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## user_12345a (Nov 23, 2014)

> I should also add that we are considering dropping the HRV since we cook, shower, and go outside a lot! Will be using batts instead of spray foam on addition due to cost (still get R24) but spraying existing walls plus headers and problem spots.


You can pipe an HRV so that it pulls all the air from the bathroom where the most showering takes place.

You can get a push-button switch in the bathroom.

for the kitchen exhaust fan make sure they use a 6" pipe.

a 4" will cripple most range-hoods.


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## Vanner (Oct 11, 2015)

beenthere said:


> How big/how many CFM is the exhaust fan for the kitchen.




Vent-a-Hood specs 600 cfm.


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## Vanner (Oct 11, 2015)

user_12345a said:


> You can pipe an HRV so that it pulls all the air from the bathroom where the most showering takes place.
> 
> You can get a push-button switch in the bathroom.
> 
> ...




Range Vent is 8" exhaust pipe. Real industrial strength action. Cooking Meth should be a breeze.

Currently have HRV as simplified on drawings. Difficult to get ductwork to all bathrooms and kitchen. 

Each bathroom has a 50-80 cfm vent to outside.


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## user_12345a (Nov 23, 2014)

You don't need a duct to every bathroom.

A 6" pipe to the master bath would work. the other bathrooms would have exhaust fans.

This reduces hrv run-time to control moisture. It also recovers a lot of heat produced by showering.

I've seen a couple of hrvs installed by the builder where the stale air is taken from the return and the fresh air supplied to the return.

*This is the stupidest way to install an hrv*; the furnace fan has to be run to ventilate, otherwise the air just short-circuits through the return air duct.

Do not get an hrv installed like that; insist that the stale air gets pulled directly from a room. Preferably one where a lot of moisture is produced -> ie bathroom where showering takes place.

With good exhaust fans and no spray foam in walls, you can get away without an hrv.

You'll have to run the exhaust fans for extended times to get a good effect. Like 30 minutes for a 10 minute shower - timers work good for this.

when you take an older house and tighten it up, the need for mechanical ventilation becomes apparent.

in the first year you'll have excess moisture; in fact you may need a dehumidifier in the basement as concrete the dries out.


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## Vanner (Oct 11, 2015)

Would love to post PDF of mech plans but there isn't an easy way to once file exceeds 100 KB.

Any suggestions?

Dropbox link for files?


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## beenthere (Oct 11, 2008)

Vanner said:


> Vent-a-Hood specs 600 cfm.


Code requires 600 CFM exhaust and greater be interlocked with a make up air fan.

However, you probably won't get close to 600 CFM of exhaust from your fan. But you will need make up air. Where will that come from.


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## beenthere (Oct 11, 2008)

user_12345a said:


> You don't need a duct to every bathroom.
> 
> A 6" pipe to the master bath would work. the other bathrooms would have exhaust fans.
> 
> ...


Unfortunately, an HRV in the summer won't help to keep humidity low in many areas. As the outdoor air will have too much moisture in it. The OP may be better off with a ventilating whole house dehumidifier.


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## supers05 (May 23, 2015)

Vanner said:


> Would love to post PDF of mech plans but there isn't an easy way to once file exceeds 100 KB.
> 
> Any suggestions?
> 
> Dropbox link for files?


Any file sharing site would work. Google Drive and dropbox have given me problems in the past with larger file sets as to trigger some kind of bandwidth quota limit. (it seems to be time based them) A small file should be OK. 

Cheers!


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## supers05 (May 23, 2015)

user_12345a said:


> .
> ...
> With good exhaust fans and no spray foam in walls, you can get away without an hrv.
> 
> ...


Can you reach acceptable HUMIDITY levels this way, yes, of course. It's been done for years. I was talking about the "freshnesh factor." Some people just like fresh air. Air in proportions that are found outside, along with the associated smells. 

(If you want to get a bit more scientific about it, you're looking to keep CO2 and O2 levels in check. Fairly easy in a resi house, but like I've said not the only aspect) 

Cheers!


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## user_12345a (Nov 23, 2014)

humidity is a pretty good indicator of occupancy and air exchange. natural air exchange also increases when it's cold, humidity goes down from the low dew point outside as well so it's good for that.

wouldn't want hrv running when it's -25.

can always put extra controls on an hrv as u know -> ie push button, ventilation on demand if it's not "fresh" enough.

the controls that run the hrv at a constant low speed and kick up to high if the humidity is high over-ventilate homes.

Set up an hrv to run like that, interlock it into the furnace fan, have stale air taken from the return and it will cost a heck of a lot more than opening a window for time to time.

If it's not set up or operated correctly there's no point of getting one.


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## supers05 (May 23, 2015)

user_12345a said:


> humidity is a pretty good indicator of occupancy and air exchange. natural air exchange also increases when it's cold, humidity goes down from the low dew point outside as well so it's good for that.
> 
> wouldn't want hrv running when it's -25.
> 
> ...


There we go. Giving the user some control back. ..... 

It's not ideal with going into the return / supply at all, but it's cheaper to install. Builder wants cheaper. Customer wants cheaper. Wheels go round. Education is expensive and time consuming. 

Cheers!


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## Vanner (Oct 11, 2015)

Alright, going to use dropbox for calc's and drawings:
HVAC Drawings
HVAC Calcs

I'll clean up the Radiant drawings as I've got a few questions about adding an underfloor loop to the main room.

Building is 17x28 (existing) and 23x23 (addition), inside dimensions from finished framing.

If I did run 6" duct from main bathroom to HRV, would it then connect to return air? Is that the only room I would pull from? How many CFM a day?

Interested in your feedback - let's hack my home!


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## user_12345a (Nov 23, 2014)

The stale air pipe gets connected to the hrv.

The stale air gets passed through the heat recovery core and exhausted.

Fresh air passes through the other side of the unit's core and gets put into the return.

*This way you can ventilate without running the furnace fan.*

If the hrv draws it's air from the return, you will incur a large expense running the furnace fan for ventilation unless your air handler has an ecm motor.

It's cheaper up front to do it like that but after a year or less you'll break even. You may save $100 to $200, but a psc fan motor can cost $25o to $350 per year running constantly on low speed.

Pulling stale air from any room other than the return will do the trick. The longer the pipe, the more it will cost you.

Pulling it from the kitchen (you'll still need a range hood) or bathroom is deal. 

It makes the unit more efficient; ie having to run less to remove the stale/polluted air. The moisture, bad smells are most concentrated in kitchens and bathrooms.


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## user_12345a (Nov 23, 2014)

The HRV btw is optional.

If it's a huge expense, it can wait. 

You can have the stale air pipe put from a kitchen/bathroom and wait on the hrv.

You can occupy the house and see if you need the extra ventilation or not.

I think you're looking at 2 grand for an hrv. Nothing compared to a nice kitchen, but all the little things add up quick.



supers05 said:


> There we go. Giving the user some control back. .....
> 
> It's not ideal with going into the return / supply at all, but it's cheaper to install. Builder wants cheaper. Customer wants cheaper. Wheels go round. Education is expensive and time consuming.
> 
> Cheers!


i like to see decisions made based on total cost of ownership, not upfront cost or payback.

What's the net cost of ownership over 5 year? 10 years? 20 years? 

often the shortcut has a higher cost of ownership.


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## Vanner (Oct 11, 2015)

Here's the Radiant Drawings

Basement loops were laid and poured. I ended up with a 10 circuit manifold so I'm thinking about adding under floor to the main living area (kitchen/living). I might be able to get it done with a single 300' loop. Wondering if the under floor fins are effective?


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## Vanner (Oct 11, 2015)

user_12345a said:


> The HRV btw is optional.
> 
> If it's a huge expense, it can wait.
> 
> ...


HRV isn't a budget breaker and I would want to do it right from the get go.

Main bathroom is on top of kitchen essentially so hitting both would be fairly easy. 6" from each room or could I create a trunk? How would the HRV be called/programmed to run?


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## user_12345a (Nov 23, 2014)

For the HRV connection I would just use one pipe to one room.

Don't over-do it, the cfm isn't very high and you won't get good exhaust performance from the bathroom if you split it with the kitchen.

Choose one room.

Use exhaust fans in the other rooms.
-------------------

Looking at the plans now.

Four things stand out....

1. Your designer is putting 4x10 registers everywhere.

Yet you have some vents in smaller rooms near or below 30 cfm.

The velocity from the registers is going to be very low.

*There are specific guidelines for sizing registers for proper "throw" and mixing. Someone else could fill u in if you're interested -> the pros would know more about the guidelines.*

You do need reasonable velocity to push the air up and have it mix with the room air, especially for air conditioning.

I would probably want 3x10 on anything below 50 cfm or so. Just my uneducated guess.

To sum this up...

If the registers are sized too small you will get excessive noise and draft.

Too big and the air doesn't come out with much force, doesn't mix properly, rises up in heat mode or stays near the floor in cooling mode.

2. The hrv simplified connection. Don't let them get away with that for the reasons stated above.

3. The high water temperature.

Your 94% boiler isn't going to be 94% running at 160f supply, roughly 130f return. (i calculated using this ->http://www.advantageengineering.com...Outlet=160&Submit=Submit&BTU=70,000&Tons=5.83)

Make sure they put an outdoor reset to lower the boiler temperature as it gets warmer outside.

You may only need the boiler at 110f in mild weather.

If this causes issues with heating water at the same time, get a separate water heater.

Any savings from using the boiler to heat water, will be whiped out by having to set the water temp to 140 to 160+ all the time.

Condensing boilers don't condense much at high return water temperatures

4. I haven't looked at this air handler model, but ask them if the fan speed can be stage.

In heating mode you can get less noise and better comfort by having the fan run at a much lower speed most of the time for heating mode.

A two-stage thermostat can be used; when it energizes the second stage the fan speed increases and *the system gives the full BTU output.

Having the system adapt itself to the outdoor temperature by doing #3 and #4 improves efficiency and comfort.

*


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## user_12345a (Nov 23, 2014)

other comments:

it says that all runs are 5" unless otherwise specified but i don't see them specified.

140 000 BTU/hr is a heck of a lot for a 60 000 btu output air handler and heating water/infloor.

Typical water heater has a 40 000 btu input. 

If this boiler isn't modulating it will short-cycle.


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## Vanner (Oct 11, 2015)

user_12345a said:


> other comments:
> 
> it says that all runs are 5" unless otherwise specified but i don't see them specified.
> 
> ...


S21 is 6" (shown on ground floor).

Can't comment on the boiler specs as I'm learning - which is why I'm here lain:


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## user_12345a (Nov 23, 2014)

Boilers aren't something I know that much about either, but BTUs are BTUs.

Your house would normally have a 60 000 btu input furnace putting out 95% of that with a 40 000 or less btu tank putting out 80% of that.

140 000 btu really sounds like an overkill. 

A boiler that's too big or run at too high of a temperature won't be efficient at all.

**

Where does it say 6"? I don't see it.

Something to thing about with respect to vent sizing...

The cfms is all over the place.

If you get a 5" pipe in almost every room, you will have to heavily rely and balancing dampers.

Vents needing 30 cfm or less will need to be dampered down a lot.

Vents needing 75 cfm (i saw 1 or two) will have difficulty getting proper airflow with the damper wide open.


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## beenthere (Oct 11, 2008)

A VM153P can mod down to only 15,400 input, so its not a bad match, to do both home heating and your domestic. Should be in lower modulation most of the times its operating/running.

The 4x10 registers may or may not be good for all of your rooms, depends on brand and model# of register.


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## user_12345a (Nov 23, 2014)

> A VM153P can mod down to only 15,400 input,


modulating, eh?

get a really good manufacturer's parts/labour warranty if available. after the warranty, get a service plan.

This system is going to have much higher maintenance costs than a regular furnace and water heater.


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## beenthere (Oct 11, 2008)

user_12345a said:


> This system is going to have much higher maintenance costs than a regular furnace and water heater.


Not really. Modcons have been out a very long time now. And the tech has become fairly reliable. Many modcons receive no annual maintenance, and have no more break downs then a non condensing boiler. 

Average car hasn't used a carburetor in a long long time. But when fuel injection first started to come out as a standard. Lots of people were saying how much maintenance they were going to need, and how expensive it would be to keep them running. 

So do you drive a vehicle that is still carbed, or does it have fuel injection. If FI, do you have to replace your injectors every year or 2, or your ECM every year or 2. Or is it pretty reliable.


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## Vanner (Oct 11, 2015)

I'm not against looking at different configs but we're really after comfort. 

One of the things that concerns me is the DHW supply beyond 15 mins? Could you run two showers (large rain head) and dishwasher at the same time?


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## user_12345a (Nov 23, 2014)

You should be fine with a storage tank.

If you have concerns, get a larger storage tank.

The recovery from a boiler 150 000 btu/hr boiler should be greater than a conventional water heater.

You can ask your designer what the gallons per minute will be for the pump serving the water heater. You can also ask about the configuration, like if the cold water gets directly heated by the boiler before entering the tank or if the tank has separate water connections for the boiler.

There are formulas used to calculate BTU delivered vs gallons per minute and temperature rise.

u can calculate recovery

Hopefully this boiler has a separate domestic loop and the water for heating will be separate.

I wouldn't want the two combined.

You'll need 120f for domestic hot water (up to 140f if someone in the house has a compromised immune system) and probably 100 to 180f for the hydronic coil, not sure about the in-floor heat.


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## supers05 (May 23, 2015)

user_12345a said:


> You should be fine with a storage tank.
> 
> If you have concerns, get a larger storage tank.
> 
> ...


In Ontario, water at the tap in any resistance cannot exceed 50*C (122*F). (plumbing code) Storage tanks must exceed 130*F (My memory is a bit foggy on the code requirement for that one) I'm not a plumber, we just run into that one often enough. 


Personally, I'd go with a combi boiler that can do instant hot water, or 2 separate systems. This way, the system can be optimized better. (The combi units, like the navien have all the necessary Controls built in)

The tank that I use is condensing, but not modulating. Off the shelf parts, cheap to fix, and I can have non stop showers. (I'd have to recheck it's actual recovery rate, but they pseudo-rated it at 1.5x non-stop continuous showers.) I love it, but it wasn't cheap.

I haven't looked at the plans yet, sorry. We are backlogged. 

The infloor heat will require a tempering valve, so that the floor can't get too hot. The air coil will have to get hotter during periods of higher demand. Allowing the loop temp to reset like this will allow for dramatically reduced gas usage. 

The 2 speed idea with a 2 stage stat is a good idea. Especially for comfort. With the lowest fan setting, you'll barely have heating, but you won't ever get a cold draft from the vents like other systems. It'll always be warm-hot during heating 

Cheers!


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## supers05 (May 23, 2015)

Finally skimmed through it. Was a little skeptical until I saw the 14x6 going up to the second floor. I'll get out my ductulator when I'm not dropping over tired, but it's more promising then building grade already. 

Cheers!


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## beenthere (Oct 11, 2008)

Vanner said:


> I'm not against looking at different configs but we're really after comfort.
> 
> One of the things that concerns me is the DHW supply beyond 15 mins? Could you run two showers (large rain head) and dishwasher at the same time?


That NTI is 141,000 BTUs output. So thats 211 gallons an hour(3.53GPM) recovery at an 80°F temp rise. So with a 80 gallon storage tank/indirect, should not have a problem taking a 10 minute 10 gallon a minute shower and running the dish washer at the same time(based on 40°F incoming water temp, and 120°F storage tank temp).

How much water will the shower heads flow a minute.


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## Vanner (Oct 11, 2015)

beenthere said:


> That NTI is 141,000 BTUs output. So thats 211 gallons an hour(3.53GPM) recovery at an 80°F temp rise. So with a 80 gallon storage tank/indirect, should not have a problem taking a 10 minute 10 gallon a minute shower and running the dish washer at the same time(based on 40°F incoming water temp, and 120°F storage tank temp).
> 
> How much water will the shower heads flow a minute.




Shower heads vary from 2.5 gpm down to 1.2 gpm (hand shower). Rain heads in the ceiling, hand shower on the wall. 

Not worried about dishwasher running at the same time but two showers going at the same time in the morning likely.


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## beenthere (Oct 11, 2008)

I'd probably want a 100 gal storage.


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## supers05 (May 23, 2015)

I've been reviewing your docs. It's too bad that they don't have an indirect combi version that's a bit smaller then the tx151c. The lowest it modulates to is 18Mbtu. If it was lower, I'd say to get 2, so that you could have redundancy and the storage tank would be more of a buffer tank. (they can "cascade", or communicate. They end up working as one boiler) If you did that, one of them would almost always cycle off as your heat loss is only 45Mbtu... 

At any rate, the tx151c will put out 3.4gpm at a 80*f rise. (close to our winter temp) (3.4 as per their brochure)

So....with 2 showers running at 2.5gpm in the dead of winter you'll be losing 1.6gpm worth of heat. 20 min is 32gal. It's not quite so simple. The tank is actually getting colder during this process, so you have to start with a hotter tank. (using a tempering valve helps here) Your drawings guy specified the 40, but if you have room for a larger tank it won't hurt. 

http://www.tanklesshotwaterguide.ca...mperature-and-tankless-flow-rates-in-ontario/

Cheers!


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## Vanner (Oct 11, 2015)

Navien NCB-150E a better fit for use in cascade setup? Spec says it goes down to 12Mbtu. 

I've got room on wall or floor for larger tank. 80 or 100 Gallons?


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## beenthere (Oct 11, 2008)

Single 150,000 BTU boiler, 100 gals.


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## Vanner (Oct 11, 2015)

Talked to NTI Tech and he thought using their S120 g tank along with either a single V153 or dual V110. Could also use the Trinity TX or TFT line depending on budget.


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## supers05 (May 23, 2015)

Vanner said:


> Talked to NTI Tech and he thought using their S120 g tank along with either a single V153 or dual V110. Could also use the Trinity TX or TFT line depending on budget.


How dedicated are you to any of this setup? As in the combi modulating boiler? I like redundancy. It cost more to buy, and maintain but it's never a crunch when something fails, just reduced capacity. Budget is always a very important aspect of every system, usually the most important.

What is your preferences? 
Energy savings? 
Low maintenance? 
Low cost? 
You only really get to pick one. Some setups strike a good balance between between low maintenance and higher efficiency. Not the highest efficiency, but decent. 

Cheers!


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## Vanner (Oct 11, 2015)

Low maintenance with high efficiency works for me. That, and a system that doesn't sacrifice comfort/function.


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## Vanner (Oct 11, 2015)

Ducting question: TJI's at 16" OC, is there a way to run 5" lines across them (set in the webbing)?


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## Vanner (Oct 11, 2015)

Another thought, if I were to take on the task of cutting 5' pipes down to 2.5' so I could pass up and between the webbing (6-7" holes in webbing) - would it drastically increase the turbulence in the run (friction)?


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## beenthere (Oct 11, 2008)

Not drastically.


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## Vanner (Oct 11, 2015)

Got things cleared up with duct runs living in TJI. Apparently the first duct guy was a splash lazy. 

Back to equipment choices!

Couple routes I'm debating:

NTI VM153 Combi Boiler
AMTS BVRM Air Handler
NTI 120 Gal Storage Tank

Or

NTI GF200
Storage Tank?
Dedicated boiler or hydronic

OR

York YP9C Furnace
NTI TX for Hydronic and DHW
120 Gal Storage Tank

Lifebreath HRV and WeatherKing AC for all options.


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## beenthere (Oct 11, 2008)

Vanner said:


> Got things cleared up with duct runs living in TJI. Apparently the first duct guy was a splash lazy.
> 
> Back to equipment choices!
> 
> ...


You want a boiler that can mod down as close as possible to the demand of the smallest load on it. While still being able to meet the largest load.

The 200 would probably short cycle too much/often.


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## supers05 (May 23, 2015)

beenthere said:


> You want a boiler that can mod down as close as possible to the demand of the smallest load on it. While still being able to meet the largest load.
> 
> The 200 would probably short cycle too much/often.


Indeed I agree. 

Cheers!


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## Vanner (Oct 11, 2015)

Quick update: I ended up going with a York 2 Stage 60k BTU gas furnace for the forced air side of heat:
Furnace: tm9v060b12mp11c
Condenser unit: ycg30b21s
Coil: cf42b

Now trying to figure out what is a good solution for DHW (10 GPM for 15 mins highest demand) and the radiant (5 loops, 1 zone, 14k BTU). 

Are the John Woods or Bradford White units with a radiant heat loop/coil a good choice? 75- 100 G Tank.


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## user_12345a (Nov 23, 2014)

How much radiant will you have? is it in floor or rads? 

In-floor is lower temp so i'm not sure if you can use the same tank for domestic hot water, or if there's a coil or domestic water gets used for heating.

the tankless units and regular boilers would have separate loops.

Standard natural draft and power vent tanks, even those designed for heating aren't overly efficient, not more than 70%.

If money is no object get a condensing tank, you can get into the high 80s or low 90s with that.

You or your designer have to make sure the tank has enough btu output to be used for the amount of radiant you have installed.

A 30 to 40 000 btu input water heater won't cut it for heating.


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## Vanner (Oct 11, 2015)

Radiant loops are in slab which is insulated properly. Calc's show 14k BTU needed at 95 degrees and 3 GPM. 

I've seen setups using DHW tank with a separate heat coil (closed loop).


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## supers05 (May 23, 2015)

user_12345a said:


> How much radiant will you have? is it in floor or rads?
> 
> In-floor is lower temp so i'm not sure if you can use the same tank for domestic hot water, or if there's a coil or domestic water gets used for heating.
> 
> ...


He's referring to a 100kbtu condensing tank. 75gal. 

Cheers!


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## beenthere (Oct 11, 2008)

Vanner said:


> Radiant loops are in slab which is insulated properly. Calc's show 14k BTU needed at 95 degrees and 3 GPM.
> 
> I've seen setups using DHW tank with a separate heat coil (closed loop).


While a standard water heater would cover your radiant loop. Your 10GPM for 15 minutes highest demand, means you need a combination of a large storage and a large BTU burner.

If you use a 75 gallon tank, and get all 75 gallons of hot water out of it, you would still need to heat up 75 gallons of water in that 15 minute time period. Which would require a burner output of 174,720 BTUs an hour(2,912 BTU output a minute). To meet your highest demand. Based on a 70°F temp rise.


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## supers05 (May 23, 2015)

beenthere said:


> While a standard water heater would cover your radiant loop. Your 10GPM for 15 minutes highest demand, means you need a combination of a large storage and a large BTU burner.
> 
> If you use a 75 gallon tank, and get all 75 gallons of hot water out of it, you would still need to heat up 75 gallons of water in that 15 minute time period. Which would require a burner output of 174,720 BTUs an hour(2,912 BTU output a minute). To meet your highest demand. Based on a 70°F temp rise.


That JW is rated at 128GPH recovery at 90*f. Might be low for 10 GPM. 

The JWSH100-199 has a recovery rate of 256GPH. But it has left the realm of simple. It's fully modulating (down shot burner) with powered anode rods. 

Edit: 10GPM is quite a bit of water..... 

Cheers!


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## Vanner (Oct 11, 2015)

Perhaps 10 GPM is aggressive, that's 2 showers using both heads in each at the same time. Maybe worst case is more like 5-7.5 GPM.


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## user_12345a (Nov 23, 2014)

efficient shower heads can have a 2gpm rating.

10 is a lot.


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## Vanner (Oct 11, 2015)

Shower head and handle in each, both at 2.5 gpm. 10 gpm is based on both showers going with all 4 heads at once.


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## beenthere (Oct 11, 2008)

A 75 gallon tank with a burner output of 43,680 BTUs, would allow you a 15 minute shower at 5GPM. And then take 1 hour to recover the entire 75 gallons in the tank from 50 to 120.

Of course, if you run your water heater at say 140°F, and use a tempering valve, that will reduce the amount of hot water you draw from it. And allow you to run a dish washer immediately after the shower was done.

A 100 gal tank would work much better though. With 75,000 BTU input, 80% or condensing.


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## supers05 (May 23, 2015)

beenthere said:


> A 75 gallon tank with a burner output of 43,680 BTUs, would allow you a 15 minute shower at 5GPM. And then take 1 hour to recover the entire 75 gallons in the tank from 50 to 120.
> 
> Of course, if you run your water heater at say 140°F, and use a tempering valve, that will reduce the amount of hot water you draw from it. And allow you to run a dish washer immediately after the shower was done.
> 
> A 100 gal tank would work much better though. With 75,000 BTU input, 80% or condensing.


The 6G75100NPDVH02 is a 75gal, 100k btu direct vent condensing tank. 96% efficient. Rated recovery rate of 128 GPH at 90*f rise

By my numbers, that allows for roughly 5.5-6.5 gpm for 15min depending on incoming water temp and tank temp. 40min complete recovery time. At 2gpm and less, this becomes basically a endless hot water supply. 

To may wish to consider one of these. It'll offset the cold water input, especially during the winter months. (or so I'm told. I've never used one.) 
http://www.renewability.com/power_pipe/how_works.html
HD and others carry them. 


Cheers!


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## user_12345a (Nov 23, 2014)

Do these combo water heaters have a way to supply a lower temp for heating or is it all at the same temperature?

that's really important to look at. you don't want 110F+ floors.


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## supers05 (May 23, 2015)

user_12345a said:


> Do these combo water heaters have a way to supply a lower temp for heating or is it all at the same temperature?
> 
> that's really important to look at. you don't want 110F+ floors.


You would use mixing valves. They are quite common. They are actually law on the hot water supply side anyways in Ontario. 

Cheers!


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