# Improve attic ventilation?



## Scuba_Dave (Jan 16, 2009)

Where are you located ?


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## Greenmaze (Jul 18, 2010)

Scuba_Dave said:


> Where are you located ?


In the Kansas City area.


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## Yoyizit (Jul 11, 2008)

Above 30 Air Changes per Hour seems like the point of diminishing returns for attic ventilation and some recommend as little as 5 ACH.
I'd make before-and-after temp. measurements in the attic to see what you're up against. Take the average of several readings.

Your insolation is not too bad.
http://www.solarpanelsplus.com/solar-insolation-levels/


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## xxPaulCPxx (Dec 2, 2006)

It seems that builders have long ago forgotten a basic physical reality: Things that are less dense rise... like hot air.

I've never met the original poster before, nor been to it's home. But I will now reach out with my incredible mind and tell you astounding details about it's house!

Ready to be amazed?

1. The stairway from the first floor to the second floor is completely open.

2. The thermostat for the home is located in an out of the way spot on the first floor.

3. In the summer, the upstairs it too hot while the downstairs can sometimes seem too cool... in the winter the same is true.

Cold air is like water. It will flow down and pool at the lowest level of the house it can. Same for hot air, but upside down - it will pool in the highest parts of the house. 

While your attic might be hot, it is Unconditioned space... let it be hot. You only care about the floor of the attic where you insulate. All you really need to do is seriously insulate the attic floor, but that will only keep the heat from going down into the second floor. It does nothing for the heat already IN the house from traveling and pooling on the second floor.

A couple of strategies for you:

1. Get a programmable thermostat that has a function allowing you to run the fan alone at periodic intervals independent of temperature. Say 5 or 10 minutes of fan every hour. This will keep the hot and cold air mixing.

2. Put a door at the top or bottom of your stairway. This will keep your hot/cold pools separated into two different zones. Grand open stairways were great tools for moving air in the days before closed windows and HVAC. Now they are an architectural relic that only serves to look pretty and make us feel miserable.

3. Move your thermostat into an area that more closely resembles a living space. If there is one room downstairs that is hot when the upstairs is hot, that is where you want the thermostat.


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## Greenmaze (Jul 18, 2010)

Hot air rises and cool air sinks. I can't believe I've gone several decades without realizing that. You would think that someone who takes it upon themselves to do their own house repairs and even seeks out the best way of doing so would have come across that basic principle of physics by now.

I realize there are other things I need to do and can do inside the house. My focus right now (and the purpose of my original post) is attic ventilation.


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## Proby (Jul 17, 2010)

I think air infiltration is the worst thing here. If you go around your attic with a tube of caulk and can of spray foam, you can do a lot to keep the hot air from coming into your house. Every pipe or wire that comes thru the top plate needs to be sealed around. Every electrical box in the ceiling needs a layer of spray foam over it like a cocoon. When I replace ceiling fans I can't tell you how much air I get blow in my face from the canopy, it comes right thru all those little holes in the electrical box and into the house, dust and insects too. Any high hat needs to be replaced with an airtight IC rated model.

Having the living area of the house sealed off from the attic is the main issue. After that, a layer of good insulation will be enough. I do a lot of electrical work in attics, it will be 130 degrees up there yet I pull up a measly piece of R-19 insulation and the metal electrical box will be cool to the touch, most of the heat is going *UP*, not down into the house. Having good ventilation might help your home a bit, but not THAT much. It will help your roof quite a bit, tho. You also need some ventilation to keep the moisture at bay.


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## Tom Struble (Dec 29, 2008)

suggestions to what? you seem to have more than required venting,your gonna fix the intake vents you screwed up,your not going on the roof,your gonna make an insulated cover for the leaky fan one day...i think your doing fine:whistling2:


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## Greenmaze (Jul 18, 2010)

Proby said:


> I think air infiltration is the worst thing here. If you go around your attic with a tube of caulk and can of spray foam, you can do a lot to keep the hot air from coming into your house. Every pipe or wire that comes thru the top plate needs to be sealed around. Every electrical box in the ceiling needs a layer of spray foam over it like a cocoon. When I replace ceiling fans I can't tell you how much air I get blow in my face from the canopy, it comes right thru all those little holes in the electrical box and into the house, dust and insects too. Any high hat needs to be replaced with an airtight IC rated model.


I spent many weekends last fall doing this very thing. Every crevice and hole I could find got filled with caulk or foam. I even replaced all my old recessed lighting fixtures with new ICAT fixtures. I did all of this in preparation of adding insulation, but I still haven't gotten around to it.

Looks like getting the extra insulation in needs to be my primary goal.


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## Gary in WA (Mar 11, 2009)

"On the same side of the house as the louvers there are four 8x16 undereave vents." ------- So all intake are on *one side *of a *gable* house? What intake is on the other side? 

Be safe, Gary


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## Greenmaze (Jul 18, 2010)

GBR in WA said:


> "On the same side of the house as the louvers there are four 8x16 undereave vents." ------- So all intake are on *one side *of a *gable* house? What intake is on the other side?
> 
> Be safe, Gary


Yes, all on one side. No intake on the other side, at least none that I can see on the undereave.


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## Yoyizit (Jul 11, 2008)

Greenmaze said:


> all on one side. No intake on the other side, at least none that I can see on the undereave.


So only a part of your attic sees moving air.


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## Gary in WA (Mar 11, 2009)

And you do know when figuring the NFVA to divide by *300 WITH* a vapor barrier installed between ceiling/insulation, otherwise use *150.*...... And that is with* plastic*, not a *vapor retarder* paper on the insulation: http://www.airvent.com/homeowner/products/intakeSoffit-specs.shtml

http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11810

http://www.advancedenergy.org/build...entilation/Attic Ventilation Case Studies.pdf

Be safe, Gary


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## DAdams982 (Jul 6, 2010)

Proby said:


> I think air infiltration is the worst thing here. If you go around your attic with a tube of caulk and can of spray foam, you can do a lot to keep the hot air from coming into your house. Every pipe or wire that comes thru the top plate needs to be sealed around. Every electrical box in the ceiling needs a layer of spray foam over it like a cocoon. When I replace ceiling fans I can't tell you how much air I get blow in my face from the canopy, it comes right thru all those little holes in the electrical box and into the house, dust and insects too. Any high hat needs to be replaced with an airtight IC rated model.
> 
> Having the living area of the house sealed off from the attic is the main issue. After that, a layer of good insulation will be enough. I do a lot of electrical work in attics, it will be 130 degrees up there yet I pull up a measly piece of R-19 insulation and the metal electrical box will be cool to the touch, most of the heat is going *UP*, not down into the house. Having good ventilation might help your home a bit, but not THAT much. It will help your roof quite a bit, tho. You also need some ventilation to keep the moisture at bay.


So there is no consequence to taking a can of Great Stuff and just burying an electrical box (Light receptacle) from inside the attic. Besides if you do have to do work on that can or change it the pain of removing the foam.


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## Proby (Jul 17, 2010)

DAdams982 said:


> So there is no consequence to taking a can of Great Stuff and just burying an electrical box (Light receptacle) from inside the attic. Besides if you do have to do work on that can or change it the pain of removing the foam.


No, I did not say to spray foam a can (high hat), I said to buy air tight IC rated high hats. 

As for an electrical box, if you need to work on it, you do it from inside the house.

If you ever need to remove that box or change around the electric in some way, the spray foam will be the least of your problems.


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## DAdams982 (Jul 6, 2010)

Proby said:


> No, I did not say to spray foam a can (high hat), I said to buy air tight IC rated high hats.
> 
> As for an electrical box, if you need to work on it, you do it from inside the house.
> 
> If you ever need to remove that box or change around the electric in some way, the spray foam will be the least of your problems.


Are these only for recessed lighting? Or how about regular lighting, the box above the ceiling... do I replace those?

I have an electrician friend, but want to tell him what I am looking for when I ask for his help to work on the power. 

Can you give me a link to what you are talking about?

Thanks for the information.


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## Proby (Jul 17, 2010)

DAdams982 said:


> Are these only for recessed lighting?


 Recessed lighting is commonly called a high hat, sometimes called a Can. If you have recessed lighting installed in the top floor of your house (the ceiling between your attic and living space), those lights should be IC rated and air tight. They cost about $8-12 and are easy to replace since you have attic access.


> Or how about regular lighting, the box above the ceiling... do I replace those?


 No, there is no need to replace the box, nor hire an electrician. Any electrical box that is mounted in the ceiling of the top floor of the house and has a fixture hanging from it (fan, globe light, chandelier, etc.) should be covered with spray foam from the attic side. Just go up in the attic, find the box, and cover the top of it with foam making sure the foam covers it completely all the way around. As I said, you want a cocoon over the whole box.

While you're up there, use the spray foam and a tube of caulk to fill in any cable or pipe penetration into the attic.

Be aware, if you have any plans of having electrical work done, it's best to do it before you go sealing these boxes. However, it's not that big of a deal to do electrical work after you seal everything up, so don't worry.


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## DAdams982 (Jul 6, 2010)

Proby said:


> Recessed lighting is commonly called a high hat, sometimes called a Can. If you have recessed lighting installed in the top floor of your house (the ceiling between your attic and living space), those lights should be IC rated and air tight. They cost about $8-12 and are easy to replace since you have attic access.
> No, there is no need to replace the box, nor hire an electrician. Any electrical box that is mounted in the ceiling of the top floor of the house and has a fixture hanging from it (fan, globe light, chandelier, etc.) should be covered with spray foam from the attic side. Just go up in the attic, find the box, and cover the top of it with foam making sure the foam covers it completely all the way around. As I said, you want a cocoon over the whole box.
> 
> While you're up there, use the spray foam and a tube of caulk to fill in any cable or pipe penetration into the attic.
> ...


Exactly what I was looking for... I only have two recessed cans in my place, installed less than 2 months ago prior to buying the house. I would assume they used the IC rated cans since they are brand new.


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## Proby (Jul 17, 2010)

DAdams982 said:


> Exactly what I was looking for... I only have two recessed cans in my place, installed less than 2 months ago prior to buying the house. I would assume they used the IC rated cans since they are brand new.


If they are in the ceiling between the attic and living space, I would assume so as well, or at least I would hope. IC rated means that you can put insulation right up against the fixtures in the attic, that's important.


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## Gary in WA (Mar 11, 2009)

"Yes, all on one side. No intake on the other side, at least none that I can see on the undereave." ------ Is there room to install intake vents on the dead air side? Either continuous or roof mounted? 

Sorry your post was hi-jacked......

Be safe, Gary


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## Greenmaze (Jul 18, 2010)

GBR in WA said:


> Is there room to install intake vents on the dead air side? Either continuous or roof mounted?


Yes there is. I'm now planning to install 8ft undereave soffit strips.

In an earlier post you made you included a link to a document that concluded powered exhaust vents may do more harm than good because they can draw conditioned air out of the house. If I've already sealed everything I could get to in the attic, and if I install enough intake ventilation, will this minimize the chance that an exhaust fan would draw conditioned air from the house?

Thanks


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## Proby (Jul 17, 2010)

Greenmaze said:


> Yes there is. I'm now planning to install 8ft undereave soffit strips.
> 
> In an earlier post you made you included a link to a document that concluded powered exhaust vents may do more harm than good because they can draw conditioned air out of the house. If I've already sealed everything I could get to in the attic, and if I install enough intake ventilation, will this minimize the chance that an exhaust fan would draw conditioned air from the house?
> 
> Thanks


Yes, your attic should be sealed to the point in which an exhaust fan will be pulling very little (if any) conditioned air from the house. 

But an attic exhaust fan still might not be helping very much. A fan is going to use electricity, it might use $15 of power per month. The fan will cool off the attic, but the cooler attic might only lead to a savings of $10 in air conditioning usage. Those numbers are just examples, but in many cases, it is true.

If your attic is properly passively ventilated, sealed off from the house, and insulated from the house- an attic exhaust fan might actually cost you more money.


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## igneous1 (May 6, 2010)

I agree w/Paul in that a programmable t-stat would be better. Moving it to a wall that will get some of the conditioned air. If the stat is in an 'out-of-the-way' spot, there will be no air getting to it to close the loop--that's why your downstairs is always cold. If you don't have a separate upstairs unit, that area will always be hotter. I'm a big fan of radiant barrier foil, which I installed a couple yrs. ago in our attic. Big difference, as it keeps the hot air out --which keeps ductwork and conditioned air cooler.


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## Proby (Jul 17, 2010)

igneous1 said:


> If you don't have a separate upstairs unit, that area will always be hotter.


 Is there any way to balance the system to get more air flow upstairs to try and compensate?




> I'm a big fan of radiant barrier foil, which I installed a couple yrs. ago in our attic. Big difference, as it keeps the hot air out --which keeps ductwork and conditioned air cooler.


Has the effectiveness wore off since installation? I've read that as a layer of dust accumulates the effectiveness is greatly reduced.


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## igneous1 (May 6, 2010)

Only way to get more air upstairs is possibly closing off some downstairs registers, but many say this does more harm than good. If you could install levers that close off the duct where it comes off the main duct line in the attic, that would work better. Shutting off registers in rooms will just divert to next closest vents/rooms. Another idea may be decreasing duct size downstairs, but that's a difficult option, if not impossible. Of course, using ceiling fans upstairs will help. Is your AC tonnage adequate?
May need to get a new unit installed.

No, the attic foil is great. I really don't think dust has any effect on it, and probably is BS you'll hear from the RB spray-on guys. If you look at the site, http://www.atticfoil.com you'll see it's tacked up on the studs--leaving a 3 to 4" gap that traps the hot air and move it upwards. You must have adequate vents to remove this heat (ie. SOFFITS and ridge/turbines/powered fans/etc.) That's the best way to install it. The easiest way is just to lay it over the insulation, but your attic and ductwork still gets really hot.
This is what I'd do if I were you. Keeping the heat OUT in the first place is much easier than overworking your AC unit every summer. I don't run our AC's during the day, I have them set to go off when we leave for work.
But when we got home at 5pm or so, our house is never over 80*. Then the air kicks on and cools it down in an hr. or 2.


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## Gary in WA (Mar 11, 2009)

"I'm now planning to install 8ft undereave soffit strips." ----- the* best location *of continuous vents is close to the fascia for optimum air pressure without rain or snow: Page *# 616:* http://books.google.com/books?id=Z8...#v=onepage&q=soffit vent installation&f=false

The power fan exhaust vents could easily cause mold growth: http://www.ronhungarter.com/black_mold.html

Hard on the AC unit: http://www.advancedenergy.org/build...entilation/Attic Ventilation Case Studies.pdf

Not just any ridge vent: http://www.oikos.com/esb/30/atticvent.html

“the chance that an exhaust fan would draw conditioned air from the house?” ---- Do you have a plastic vapor barrier installed at ceiling/attic joint? OR a vapor barrier primer paint rated at 0.05 permeability on the whole ceiling?: http://www.panhandleinsulation.com/buildingmaterials.html

Be safe, Gary


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## xxPaulCPxx (Dec 2, 2006)

igneous1 said:


> Only way to get more air upstairs is possibly closing off some downstairs registers, but many say this does more harm than good. If you could install levers that close off the duct where it comes off the main duct line in the attic, that would work better. Shutting off registers in rooms will just divert to next closest vents/rooms.


Our last house in Illinois was a colonial with AC. Big problems keeping the upstairs cool. I purchased magnetic vent covers that blocked most air flow in the downstairs vents so all the cold air would have to start out UPstairs before it could cool the downstairs. That made a real difference in balancing the system out. I reversed it in the winter for hot air flow.

I had one floor vent in the bathroom that must have been the first vent off the HVAC system. When I blocked the downstairs vents, and the blower kicked on, it would literally BLOW the vent out of the floor! I had to obstruct that vent channel just so I could keep the vent on the floor!


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## Dale Chomechko (Mar 11, 2008)

Hot air goes up. if you open your doors & blinds it doesn't matter how much insulation you have. Window glass (double glazed with argon gas) is only about R4.
If you have a real problem upstairs with heat there are several ways to cool off the rooms.
First one (& my kids used to laugh at me but all do it now)
keep the cutains drawn during the heat of the day, as it cools off pick an upstairs window & put a fan in it blowing out at high speed.
Close your downstairs doors & windows
Open your upstairs windows in the rooms you want to cool off
Close the doors in those rooms to within about 2 inches(you may need to put something in the door to stop the air from closing it)
The fan draws the cooler air through the window and the door but because of the restriction of air to 2 inches, air is drawn from the ceiling as well as the floor
Takes about 1/2 hr to cool off a room.
Second- yes a 2 speed fan works but you need a return air on the ceiling or close to it otherwise your just blowing hot air around.
Third- opening skylights are a great way to remove the heat
Forth-Most people don't realize how good cedar shakes are at insulating from the heat before it enters your attic
Hope one of these solutions work for you
Dale Chomechko
DC Roofing Inc


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## xxPaulCPxx (Dec 2, 2006)

Fine Home Building magazine just had an article this month about "Stack Effect", good reading, though I'm not sure I buy into all the items presented.


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