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Old 07-19-2010, 10:33 AM   #16
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Improve attic ventilation?


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Originally Posted by Proby View Post
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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Old 07-19-2010, 11:25 AM   #17
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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.
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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.

Last edited by Proby; 07-19-2010 at 11:27 AM.
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Old 07-19-2010, 11:52 AM   #18
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Improve attic ventilation?


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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.

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.
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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Old 07-19-2010, 12:00 PM   #19
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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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Old 07-20-2010, 05:58 PM   #20
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Improve attic ventilation?


"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......

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Old 07-21-2010, 09:52 AM   #21
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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?

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Old 07-21-2010, 09:59 AM   #22
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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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Old 07-21-2010, 12:37 PM   #23
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Improve attic ventilation?


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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Old 07-21-2010, 12:40 PM   #24
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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?


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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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Old 07-21-2010, 01:07 PM   #25
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Improve attic ventilation?


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.

Last edited by igneous1; 07-21-2010 at 01:12 PM.
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Old 07-21-2010, 01:47 PM   #26
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Improve attic ventilation?


"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=Z8a...lation&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/buildi...%20Studies.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/b...materials.html

Be safe, Gary
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Old 07-21-2010, 05:46 PM   #27
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Originally Posted by igneous1 View Post
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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Old 07-22-2010, 02:32 AM   #28
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Improve attic ventilation?


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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Old 07-22-2010, 03:16 AM   #29
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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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