# Double or Triple pane?



## BlueBSH (Oct 29, 2009)

So I am replacing the first 4 of my 13 windows this year.. the rest next year.

I am using basically the same windows that were in there before, white vinyl new construction windows. the previous owners didn't flash the windows or caulk them or anything so they where very drafty and have pretty much failed at every point they can...


My plan now is to get the siding off around the windows, and install them to AAMA Method B flashing I think it is. with butyl tape (flashing tape about 8" wide) to get a good seal and caulk under the nailing fin to help seal it even more..

Well this leads me to which windows to get...

I got quotes for double and triple pane windows.

The triple pane windows came in at a whole $150 more for the 4.

Catch is they use slightly thinner glass... the double pane windows have a thicker glass.

The triple pane windows have two Low E coatings on the two interior panes, the double has only one low e coating on the interior pane.

Is triple worth it? I'm looking for sound deading and heat retention obviously.

The window frames are foam filled vinyl (which is an upgrade from the current hollow ones).

The windows are from Soft Lite it's their pro series windows if anyone has any experience with that brand, my old windows were Gorell (which softlite bought out)


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## Windows on Wash (Aug 30, 2011)

From the standpoint of sound attenuation, Triple doesn't help and might hurt in some cases. 

From the standpoint of heat retention, they are much better.


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## dd57chevy (Jun 21, 2015)

I'd have to agree W on W . My experience has been noise penetration comes through lack of perimeter sealant or improper sash fit . 

Not sure what Softlite claims , I _THINK_ triple pane units produce 20-30% better U ratings . My take , & this is JMO , but I've never been impressed by triple pane _vinyl_ frame windows I've worked on . The glass units always seem too heavy for the frames & hdwe........Unless you have _big _windows , most use single strength glass for both double _&_ triple pane units . 

The truth is , the average vinyl window produces 1/3rd of the insulation of the surrounding walls . If you're starting from scratch , there are _other_ ways to boost it up . _Proper installation , _insulated accordian shades , lined drapes , storm windows , etc .


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## Yodaman (Mar 9, 2015)

IMO - triple pane for your climate zone is a little overkill. If you are building this house to live out the rest of your golden years and don't mind spending the extra money then buy them. If you are accustomed to drafty poorly installed windows, then you will be really happy with a good quality _properly_ installed double pane


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## BlueBSH (Oct 29, 2009)

what about safety? would having thicker glass or having more panes of glass be better? Three of these windows are going in 2nd story bedrooms...

I know if you hit anything hard enough it will break, but I'm looking at the how much does it take to go through point of view...

the double pane window is "double thick" glass.. I saw a same cut away piece at the local showroom, the glass is almost twice as thick as the normal glass panes gorell used and almost twice as thick as the triple pane glass...

the windows are all metal re-enforced frames also... so it's not like it's just vinyl like the old gorell ones were
they said the thicker glass meets Florida hurricane standards (I'm in Pennsylvania, so not expecting a hurricane anytime soon) but would this help with safety?


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## dd57chevy (Jun 21, 2015)

Not sure exactly where you see a safety risk . Kids rough-housing & sticking an elbow through one ?


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## BlueBSH (Oct 29, 2009)

I mean like going through one! :laughing:

was just wondering what would stop you more, 3 thinner panes or two thicker ones.


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## Yodaman (Mar 9, 2015)

Two or three panes of glass is not a deterrent for someone wanting in your home. Tempered glass maybe. A more useful tool to justify the extra cost would be to run a manual J calc using each type window and know exactly what you are paying for and what the ROI is.


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## Windows on Wash (Aug 30, 2011)

Few points for clarification here.


Regular annealed glass (whether single strength or double strength) will provide you no break in prevention over the other. Are they harder to break than an old single pane wood window, sure. Are they any sort of theft deterrent, no.
As mentioned, you can opt for tempered glass or better yet would be laminated glass. Tempered glass is great but if the crook knows what he is up against, he can break it quite simply and have a much more hospitable hole to crawl through without injuring himself.

Triple pane is not overkill for PA and especially with the recent shift in weather patterns.
As long as you are okay with the darker glass, you should opt for the most efficient window that you can get that falls within you budget.
Depending on the cost of the upgrade, it may be worth the additional investment. If they are charging some astronomical rate, far less worth it and the ROIs become quite protracted at that point.

Noise can be a concern and inside of the standard replacement options, you can opt for laminated glass and get a bit better performance as well the break in deterrent as well.
What the delta in performance between double pane and triple pane will depend entirely on the glass coating, manufacturer, and options.
The impact of a more efficient window on the entirety of the wall performance is quite undervalued. 



Example:


Figure on a 2x4 wall with some 1" foam (XPS) continuous on the exterior. If we assume that the net clear wall (factoring in framing but not windows) is 80%, that would give you loaded R-Value in that wall of about R-14.6.


If you figure on that average R-Value (wall section with framing) is about R-14.6, the difference between a double pane window at U-Factor of 0.29 and a triple pane with a U-Factor of 0.18 is pretty significant. 



Lets assume that the walls are 70% of the walls and windows are 30%.



Wall A (double pane window) will have an average (windows, framing, insulation) R-Value of: *7.4*


Wall B (triple pane window) has an R-Value of: *9.8*


That's a total wall R-Value difference of: *33%*


The total exterior walls on the home with the triple pane are a 1/3rd more insulated.


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## Yodaman (Mar 9, 2015)

WOW, I respect your opinions on the topic. Although I am still a bit of skeptic on the ROI of the triple. I would be curious to see the actual manual J calc and how that translates to a actual reduction of btu's and cost savings. I think 30% window coverage is a little high but probably not too far off. My own window coverage is closer to 10 to 15%


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## Windows on Wash (Aug 30, 2011)

We tend to run a bit more glass in these parts and you need to take out the attic side gables when you are looking at square footage of impact. 

Every home is different though. 

Again...ROI depends entirely on what the upgrade is going to run you in this case. As important at U-Factor, but often under discussed, is air infiltration rates. 

The example above is just to demonstrate the impact of going with a higher performance glass package and its effect on the total wall. 

If we use your example of 15%, the difference is *R-9.8* vs. *R-11.7* and a delta of *20%*


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## ddawg16 (Aug 15, 2011)

Here is one of many links on the subject

http://www.fibertec.com/double-vs-triple-pane-windows/


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## Yodaman (Mar 9, 2015)

Windows on Wash said:


> We tend to run a bit more glass in these parts and you need to take out the attic side gables when you are looking at square footage of impact.
> 
> Every home is different though.
> 
> ...


Telling someone that their avg wall R value will increase 20 to 30% sounds like a impressive number. Telling someone their avg wall R value will increase from 9.8 to 11.7 sounds less impressive. But neither number tells the important information regarding ROI. Too many variables. As I earlier mentioned I would be curious to see the actual manual J data to see the benefit and determine ROI. 

And even ROI is subjective to the buyer. 5 to 10 years, I would be interested, 15 and up I am balking at. Just my opinion. :thumbsup:


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## Windows on Wash (Aug 30, 2011)

ddawg16 said:


> Here is one of many links on the subject
> 
> http://www.fibertec.com/double-vs-triple-pane-windows/


Bunch of questionable information in that link and somewhat odd for a reputable company like Fibertec to post up. 


Double pane is not less durable than triple pane and the potential for seal failure if triple pane is, as a result of double the sealed chambers, twice as high. Perhaps they are making the argument that the increased risk of condensation could be a durability risk and condensation is far more likely to form in a Canadian climate with double pane.
Triple pane is not "safer" than double pane. If anything, its more easy to break the glass. Again, not sure what their angle is here.
What about heavy weight (i.e. more glass weight) makes for a more durable window?



Yodaman said:


> Telling someone that their avg wall R value will increase 20 to 30% sounds like a impressive number. Telling someone their avg wall R value will increase from 9.8 to 11.7 sounds less impressive. But neither number tells the important information regarding ROI. Too many variables. As I earlier mentioned I would be curious to see the actual manual J data to see the benefit and determine ROI.
> 
> And even ROI is subjective to the buyer. 5 to 10 years, I would be interested, 15 and up I am balking at. Just my opinion. :thumbsup:


The thing about windows is that the more you can shorten the delta between a well performing wall and a weak point window, the better the wall will perform. 

Energy, just like water, will follow the path of least resistance and that is why the relationship between window weak spots and wall R-Value average is not a linear relationship. 

All the ROI are completely dependent on the additional investment for triple pane. Again, if the upgrade cost is reasonable, you should (if you live in a heating degree day dominated climate) opt for triple pane when you can. 

You are incurring a majority of the expense for the window replacement in the labor, window construction, overhead, etc., etc., etc.

If you can get a better performing window for a bit more, its much easier to justify that additional expense of an upgrade than it is to justify the expense of a complete window replacement on its own. 

There are aspects of this that aren't being accounted for either when it comes to comfort and room performance. 

Often times, customer will have rooms that are just uncomfortable and the HVAC can't keep up in a given area (rooms with a bunch of windows and under-served or unbalanced HVAC). Going from a double to a triple in those rooms can often compensate for the lack of supply side BTUs and make that room usable again for clients. 

Give a client a portion of their home back that they didn't previously want to be in...and you have a happy client. 

Again...I agree with you on the ROI, but without knowing what the investment delta is, you can make those calculations. 

Let me know if you can run the Manual J and I will give you some recent projects.


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## Yodaman (Mar 9, 2015)

Windows on Wash said:


> Bunch of questionable information in that link and somewhat odd for a reputable company like Fibertec to post up.


To me it seemed like a sales pitch, which I would expect from a MFG.



Windows on Wash said:


> The thing about windows is that the more you can shorten the delta between a well performing wall and a weak point window, the better the wall will perform.
> 
> Energy, just like water, will follow the path of least resistance and that is why the relationship between window weak spots and wall R-Value average is not a linear relationship.
> 
> ...


I tend to agree mostly with what you said. But still am curious of the numbers. I do not have the manual J software but have used on-line calculators in the past. Think I will find one, plug in the data from my own house and compare with double and triple pane glass. I post up the results when done


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## BlueBSH (Oct 29, 2009)

thanks for the info and opinions. Just another question, here's the specs of the windows I'm looking at, not 100% how you interpret the numbers. R Value I understand but when it comes to windows I haven't gotten down the meaning of the letters yet..

U-Factor: 0.18
Solar heat gain Coefficient 0.26
Visible Transmittance 0.42
Condensation Resistance: 72
Air leakage .07 CFM at 25 MPH

U Factor I think I understand the least, Lower the number the better right? is this kind of a relationship to heat transfer?

Solar Heat gain, now this one to me sounds like the amount of solar energy that gets through?

Visible transmittance, I assume the amount of light that passes through?

Condensation resistance, this one seems self explanatory

and air leakage seems self explanatory...

do these numbers seem pretty good for a triple pane window?


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## Windows on Wash (Aug 30, 2011)

Those numbers are solid. 

Air number isn't great but the rest are good.


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## BlueBSH (Oct 29, 2009)

0.07 CFM isn't great? What's a good one averaging at? I'm just curious as to what is out there to compare

my old windows are rated at 0.30 when new, so it's already at least 4x tighter then the old ones.. I'm sure the old ones are no where near that now though, probably many times leaker now with failing weather stripping *lol*


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## Windows on Wash (Aug 30, 2011)

That's probably not fair on my part. Under 0.10 is good. Sub-0.05 is that much better. Several windows out there report 0.02 and below.


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## Yodaman (Mar 9, 2015)

I ran the manual J on my own house to compare how the double and triple pane glass would affect heat loss.

I used the first floor only at 1000 sq ft, my glass to solid wall ratio was 13%.
Design temps were -4 outside, 70 inside


With double pane the total heat loss was 50,575 BTU
With triple pane the total heat loss was 50,025 BTU

550 BTU per hr, or about 1% reduction in whole house heatloss,

obviously not a complete picture, but gives you an idea


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## Windows on Wash (Aug 30, 2011)

What were you using for U-Factor in the two windows?

Can you re-run it but just changing the average wall R-Value?


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## Yodaman (Mar 9, 2015)

Windows on Wash said:


> What were you using for U-Factor in the two windows?
> 
> Can you re-run it but just changing the average wall R-Value?



the on line program uses canned selection parameters to choose from,
the best fit choices for windows were double pane vs triple pane with low E and argon, so we really didn't compare a apples to apples double vs triple.
The triple with gas would have a advantage.

Since its a on line calculator there is no way to save the data, so changing parameters now would require complete re-entry.

Here is the link if interested http://www.loadcalc.net/index.php

But with only the BTU/hr delta given as a result, there is no way to extrapolate even remotely accurate heating or cooling savings since it only is using design temp of -4. Which of course will not be on most days. 
A better approach might be to use avg winter cold temps as the low design input. And then take the delta per hr and multiply by the number of heating hours and days in the year. And to be fair the same technique should be used for cooling days.

With a annual btu savings the cost of energy could be calculated


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## BlueBSH (Oct 29, 2009)

well I think I decided to just go triple now. I've been working on this house for a while now and gutted a 2nd floor room that was hot and humid in the summer with the AC on (AC was new in 2013, had manual J and manual D's done, previous owners had a 5 TON AC an a 125k BTU/h furnace and needed replaced... new one is a 3 TON AC and a 60K BTU/h furnace after the calculations)

well that didn't help so I gutted that room to the studs, took out the fiberglass which was R-19 fiber, (2x6 walls) replaced it with R-22 Roxul, did a continuous vapor barrier sealed anywhere the air could infiltrate, sealed around the current old windows as part of the test and put air tight double sided tape and shrink rap sheet over the window to take out any air infiltration (the stuff you use for winterizing windows), re-drywalled it and this summer the room next door right (same sq ft, same design, same number of windows, vents and air returns) right now is 82 degrees.. the room I redid as a test is now is 69 degrees. the room is actually 3 degrees cooler then the 1st floor!

(roxuled all the walls in the room 2x6 exterior 2x4 interior, not just the exterior, mainly for sound proofing since its a bedroom, but it helps a lot with heat obviously also)

Just goes to show what poor building can do to heat gain and loss.... so figure might as well do the triple now and see what it does.


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## Windows on Wash (Aug 30, 2011)

Yodaman said:


> the on line program uses canned selection parameters to choose from,
> the best fit choices for windows were double pane vs triple pane with low E and argon, so we really didn't compare a apples to apples double vs triple.
> The triple with gas would have a advantage.
> 
> ...


The fact that the information is canned and therefore limited, might explain some of that. 

I would love to see the tweaks applied and see what shakes out.


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## Yodaman (Mar 9, 2015)

WOW- this article supports both our arguments. While I am skeptical of the ROI and value of the extra pane, you promote the periphery benefits of comfort.

http://www.norbord.com/na/blog/are-triple-pane-windows-a-good-investment


been looking for another calculator more suited to window ROI - not finding much


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## Windows on Wash (Aug 30, 2011)

Thanks.

I will take a look.

Again, I haven't argued for ROI without knowing the delta. You need to know what the cost differential is before you can tackle the ROI question. 

Once you have incurred the cost of the window, the labor, and standard double pane...the ROI should be based on the upgrade cost. Most window replacements are a result of a lack of functionality and not the energy equation side of it.


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## ron45 (Feb 25, 2014)

The only way to do this is to have two identical huts side by side, identical in every way possible. Even then wind direction could play a major roll in difference.


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## Yodaman (Mar 9, 2015)

Another look and another angle,

If we look the heat loss Delta on a single window, comparing only double to triple glass windows and using the listed
U Factor, it might look like this,

(formula pulled from this site http://www.pexuniverse.com/content/calculate-heat-loss)

BTUH of Surface Heatloss = U factor x sqft x Delta T 
Where delta T is inside temp - design temp (using 70 degree inside and 20 degree out side) based on my average 
winter cold temp.

Window size 3' x 5',

Double Pane with Low E and Argon - .29 UF x 15sqft x 50T = 217.5 BTUH

Triple pane (from OP's spec) - .18UF x 15sqft x 50T = 135 BTUH

So we have a 82.5 BTUH Delta on a single window,

82.5 BTUH x 24 hrs/day = 1980 BTU/day
1980 BTU x 180 heating days(estimate) = 356,400 BTU per heating yr

356,400 btu / .95 (NG HE furnace) = 375,158 expended BTU/year

375,158 btu / 1032 caloric energy value of our local NG = 363 cu ft NG

from my Feb 2015 heating bill, looks like I paid $97.69 for 90ccf of NG,
So $1.085 per ccf of gas,

Annual projected savings from heating only, would be $1.085/100 x 363 cuft = $3.94 per year savings comparing
2 pane UF .29 to 3 pane .18 UF

The $3.94 per year represents the value of the saved energy upgrading one 3' x 5' window from double to triple pane glass. Of course
it does not include energy saved from cooling, but in the north east the significance is diminished.

I am sure there are more accurate ways to calculate this , so anyone, feel free to correct. 
And since the OP has already made a decision to purchase the triple, this exercise is really just for curiosity :whistling2:


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## Windows on Wash (Aug 30, 2011)

Yoda,

That's probably not that far off. I am going to check with my one friend that is glazing engineer. 

Couple of things worthy of note:


You are using natural gas as the calculation
This is the most efficient and cost effective way to heat your home of the traditional methods
Re-do this calculation with electricity, LP, Heating oil, or Kerosene and that number will at least double

Natural gas numbers are lower than they have been in 15 years in many cases.
If you re-run the numbers with anything other than natural gas, you are saving closer to $10-15 per window on the heating season (no calcs for cooling as you pointed out). 



If you are incurring the expense of a window replacement and the upgrade to triple pane is $70, that could be as few as 4-5 years (on heating alone) on a window that should last 20+. Figure in the cooling savings and you could be in the 3-4 range. 



Not terrible math at that point. Again...depends on the cost of the upgrade.


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## Yodaman (Mar 9, 2015)

WOW, spoke with my window dealer today regarding a 2 to 3 pane upgrade price. He came in with a $110 upgrade price with a .21 U Value. So in this case with out even re-running the BTU delta the ROI to upgrade is closer to 28 years, (assuming NG and 95% HE furnace). If running a 80% NG furnace the ROI is cut in half to 14 years.

50% of the country does with heat with NG. So these numbers are relevant to the lions share of population. 

I will concede your point regarding "buy the best window you can afford". Hey, why not. It will add to the comfort level. And your home is almost always a good place to invest. 

But after going through this exercise, My original opinion is still mostly unchanged. Although "overkill" is probably the wrong word to use.
I think I would just caution that upgrading to a triple may or may not make a lot of sense. And if a smooth talking salesman wants to up sell us on a triple by emphasizing the massive amount of extra energy its going save, we'll know different.

Thanks for sharing your expertise on the topic :thumbup:


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## oberon (Apr 29, 2006)

I wonder how many people who are building or remodeling a home when asked about spending an additional $1500 for upgrading kitchen counters or upgrading floor coverings, or even upgrading window treatments, ask "what's my ROI"? Generally speaking, I suspect that the ROI isn't very good for any of those upgrades.

Just a thought.


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## Yodaman (Mar 9, 2015)

oberon said:


> I wonder how many people who are building or remodeling a home when asked about spending an additional $1500 for upgrading kitchen counters or upgrading floor coverings, or even upgrading window treatments, ask "what's my ROI"? Generally speaking, I suspect that the ROI isn't very good for any of those upgrades.
> 
> Just a thought.



Well, since most think ROI is some sort of pasta, I would guess not very many! But there is a small contingency who make their living within the housing industry that do actually care how the dollars are spent and the value added. And sometimes the only way to know is to crunch the numbers.:thumbsup:


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## Windows on Wash (Aug 30, 2011)

Yodaman said:


> WOW, spoke with my window dealer today regarding a 2 to 3 pane upgrade price. He came in with a $110 upgrade price with a .21 U Value. So in this case with out even re-running the BTU delta the ROI to upgrade is closer to 28 years, (assuming NG and 95% HE furnace). If running a 80% NG furnace the ROI is cut in half to 14 years.
> 
> 50% of the country does with heat with NG. So these numbers are relevant to the lions share of population.
> 
> ...


I re-ran you numbers with the triple pane unit that we most often use (U-Factor 0.15) and heated the home with electricity (for contrast). 

Savings delta of $19.91 per year. 

Not a bad number now. Lets assume that we pay for the triple pane upgrade at your number ($110), now we are at 5.50 years. That is a nice ROI if you ask me and, as you stated before, does not account for any summertime (cooling season) savings. 

Your previous calculations are assuming a few things that I think are in question:


The cost of natural gas will stay this low over the duration
You are heating with natural gas. As you pointed out, only 50% do.
That heat flow is linear
Energy will take the path of least resistance. If there is an R-19 wall and R-4 window, which direction do you think most of the energy in the room will be moving.
Your numbers on heat flow are counting only transfer if I am not mistaken. No accounting for convection and conduction.

I will have to crunch some old numbers on my end of things but I think this at least serves as a contrast point to your numbers and what are probably the low side of the equation. 



I have sincerely appreciate this thread as well and your contributions. 



This only serves to drive the education and forward thinking on this stuff. Good to see that happening!!!


:thumbsup::thumbsup::thumbsup::thumbsup:


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## Yodaman (Mar 9, 2015)

Windows on Wash said:


> I re-ran you numbers with the triple pane unit that we most often use (U-Factor 0.15) and heated the home with electricity (for contrast).
> 
> Savings delta of $19.91 per year.
> 
> Not a bad number now. Lets assume that we pay for the triple pane upgrade at your number ($110), now we are at 5.50 years. That is a nice ROI if you ask me and, as you stated before, does not account for any summertime (cooling season) savings.


I agree, anything in the 5 year range should be attractive to most. Although anyone thinking of upgrading their windows that is using electric to heat with should consider the possibility of another fuel source. Coal or wood would cut heating cost by 60%. Propane or oil would probably cut it in half.




Windows on Wash said:


> Energy will take the path of least resistance. If there is an R-19 wall and R-4 window, which direction do you think most of the energy in the room will be moving.


Agreed, the laws of thermo-dynamics dictate that heat always moves to cold. Combine that with old leaky windows and your heat is literally flying out the window.



Windows on Wash said:


> Your numbers on heat flow are counting only transfer if I am not mistaken. No accounting for convection and conduction.


Of the three types of heat transfer, conductive, convection and radiation,
it is conductive heat transfer that we have been calculating. It may be possible to calculate convective transfer by using air leakage ratings and radiation transfer by using solar heat gain coefficients. Although I would think if these numbers were significant that they would be included with the manual J calculators.


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## Windows on Wash (Aug 30, 2011)

I wouldn't count on coal or would being along for much longer given the direction of the EPA admission standards. There are some applications were combustion just isn't an option. We also see quite a few multifamily applications that are run purely on electric.

Very much agreed.

At the end of the day conduction is the only way the energy is really moving to outside, however, convection and radiation are driving the train.


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## Yodaman (Mar 9, 2015)

Yes the coal industry is being crushed before our eyes. And the electric rates will be rising because of it.

I think electric might work in apartments because each unit might only have 1 or 2 out side walls. So the delta T on a few walls may be zero.

I have a 2 unit, upper/lower where the upper is electric and the lower is gas. The upper heating rates are reasonable because of the lower heat rising. Not fair, but that is the way it is.


This site by Penn State explains the the 3 heat transfer methods clearly for anyone interested.

https://www.e-education.psu.edu/egee102/node/2053


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