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Spray foam in part of attic (seperate from rest of attic)

Posted by athensmomof3 (My Page) on
Tue, Nov 13, 12 at 11:10

We decided against spray foam in our entire (large) house. Given our climate, the calculators put the cost/benefit payback at over 100 years. So far, I am happy with this choice except our playroom (over the garage with kneewalls and clipped corners on ceiling (so no cellulose possible) was significantly hotter than the rest of the upstairs this summer (unusually hot with temps over 100 for days on end).

This attic is separate from the rest of the attic (has its own access point). Does it make sense to foam only this area? Not sure of the exact square footage but it is over a 3 car garage.

Of course, lowering energy bills would be great but making the playroom more comfortable is also a priority. Rest of upstairs is very comfortable.


Follow-Up Postings:

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RE: Spray foam in part of attic (seperate from rest of attic)

We are planning to spray foam the garage ceiling/game room floor. We have heard that this will help considerably.


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RE: Spray foam in part of attic (seperate from rest of attic)

Hi athensmom
Is your playroom insulated and drywalled now? or is it unfinished studs? If its already finished with some type of insulation I'm not sure how you add foam now. you can add cellulose via holes in drywall.
If its unfinished then any insulation drywall etc will make it more comfortable.
One thing you may have to consider is the adequacy of your HVAC to push the appropriate AC to the room.
We had this issue with another house with my daughters room over the garage. We added insulation but didnt help much until we had vents reworked and upstairs heat pump changed. Heat pump was on one end of house and BR on another. Vents were inadequate.


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RE: Spray foam in part of attic (seperate from rest of attic)

My guess is your heat is coming from the garage. In spaces over the garage, all sides need to be insulated and sealed to a similar value. It makes little sense to put r39 in the rafters and r19 in the floor for example. Hot air is rising in your garage, going through your floor and radiating into the space.


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RE: Spray foam in part of attic (seperate from rest of attic)

We have r30 in the floor of the garage but it is still hot - and yes it is finished. I *think* we have the same on the ceiling but am not sure. It is not easy to access (have to climb up through hole in storage room) to check. That may be the major problem. Our ceilings throughout the rest of the house have r49 blown in cellulose but no way to do that in there. It is not vaulted but has a 10' ceiling so we have knee walls and slanted ceilings on the edges. The slanty ceilings meant no cellulose so they used batts.

It is not common to insulate garage walls in our climate, so they are not insulated - although I wish I had them throw some batts in the walls just for a little extra insurance.

I sent my builder multiple emails about insulating the knee walls with foam board (or something - can't remember details now but it was a recommendation I found to insulate them), but I don't know that it was done, or done properly. Too late to insulate them now without ripping out sheetrock . . .

Just wondered if foaming the attic rafters might help.


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Also

Wish we would have thought to spray foam the ceiling/floor of the garage . . .

We did have an issue of an underperforming a/c unit up there for most of the summer (freon leak which has been found and fixed), so perhaps that was part of it.


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RE: Spray foam in part of attic (seperate from rest of attic)

Athens - I have a bedroom above the garage (central NC) and it is not one degree hotter than anything else. We have an uninsulated garage - rarely below 55 in the winter - usually lives at 60 when the low is 35. We have batts and conventional insulation - although we have r-40 in the attic when code is r-30. The garage gets hot in the summer with 2 unshaded west windows but it is never noticed in the room above (I presume but can't remember that we have r-30 in the garage ceiling).

I do have radiant barrier in the attic.

I did insulate the knee walls after the build with 1 inch of rigid foam - while it makes sense it is still a 10 year payback in our climate. This makes sense if you are having comfort issues.

My point is that you shouldn't necessarily blame the room temp problems on insulation. But things you can work on are air leakage points - primarily can lights. Everything can be sealed as well as possible from below. Cans are always a problem and if you have them in a cathedral type ceiling there is always a loss or gain there and there is nothing you can do about it.

You should be able to fix most of your issue with ductwork tweaking and air leakage tweaking.

My hottest room in my house is the one with unshaded west windows despite them being low-e windows.


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RE: Spray foam in part of attic (seperate from rest of attic)

We do have can lights in that room - lots of them. We don't have them anywhere else upstairs except a hallway. Perhaps that is the problem. I really wonder about the sufficiency of the insulation in that room since it is the only place we don't have blown in cellulose. . .

Is it helpful to air seal the cans by pulling off the housing and caulking? That is something I can handle assuming I am tall enough with a 6' ladder;). I am quite sure there is no air sealing from above due to the batts. The hallway may be better sealed because it has cellulose around the cans.

Do you think the radiant barrier is worth having? Keep in mind that my husband is *not* a DIYer and I am cheap so I am but I really can't see me doing that ;). . .

Once we got the a/c fixed, the bills went way down but I don't know if it helped the room temp or not since it was past the high heat season.

Unfortunately no way to insulate the knee walls now because most are sheetrocked in with no access (we do have access from one in the storage room at the back but that only gets us to the first dormer/window seat.


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RE: Spray foam in part of attic (seperate from rest of attic)

no way to insulate the knee walls now

So you make one! Just cut out a section of drywall over three studs, remove one stud and there you go. You can then leave an access panel or replace the stud then re-drywall after gluing on EPS or XPS on the attic side of the drywall.


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RE: Spray foam in part of attic (seperate from rest of attic)

worthy - I have thought about it. Just want to be sure it is worth it. We have 3 rowdy boys and 3 to 5 Nerf hoops given any time in the room so we will be repainting sooner rather than rather . . . The house shakes with all the b'ball up there plus I am already marking places to patch :). No one without as many boys as I have gets it but we have to repaint various places yearly to keep them "respectable" ;)


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RE: Spray foam in part of attic (seperate from rest of attic)

There are gaskets you can get for cans and you can caulk the penetration with the trim off also. I'd do that first and see if it helps.

The knee walls are a problem but I bet the cans are the real issue.

Radiant barrier is not worth a retrofit usually. During new construction, the OSB with barrier is just a small upcharge. I think it was like $200 for our house and so it is worth it.

I have a friend who had a similar house to mine built but with no extra insulation etc. He is having a similar problem as yours and he has gotten several quotes including foaming the rafters. His plans include finishing the attic someday (why I don't know since he has a finished basement and is over 6k) so he is thinking of foaming the rafters. I encouraged him to get his cans sealed - sorry I don't know what he did and summer is over anyway...

It frustrates me to no end when I hear this story over and over. Comfort issues that are really failures of sealing and insulation. GCs are so oblivious to energy costs but the comfort issues should come back and bite them.

Cans into an attic are just always an issue. They are so rarely handled ideally especially in the South. But you can get a lot of mileage from the gaskets and caulking the edge when you take the trim off. I bet you can fix 50% of your problem. You can certainly reduce air movement 80% but you can never have the space taken up by the can to be any better than r-2 that lowers your r-30 by a significant amount.

If you can get above the can (and I am guessing you can't), then you can seal 100% and insulate some.

The knee walls are an issue for 2 reasons which you probably already know. They often around here are a r-13 batt with no enclosure. Batts work pretty poorly when not enclosed in a space. Also r-13 wall against a 140 degree attic is pretty bad when you are trying to maintain less than 80 inside. The rigid foam encloses the batt, deals with the thermal bridging at the stud and adds another r-4 to the wall. It probably cuts the heat gain by 50% by a combo of all these benefits. It really should be code. The 4x8 sheets cost $12 or so.


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Yowza!

Reading about air tight cans (which I would have specified in the playroom had I known better) and found this little gem:

"How much of an impact do recessed cans have
on the total air leakage picture of a house?
It is estimated that one conventional (IC or non-
IC) fixture can be responsible for the loss of
between $5 and $30 per year worth of energy
and can dump about one-third of a gallon of
water daily into a cold attic."


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RE: Spray foam in part of attic (seperate from rest of attic)

'We do have can lights in that room - lots of them. We don't have them anywhere else upstairs except a hallway. Perhaps that is the problem. I really wonder about the sufficiency of the insulation in that room since it is the only place we don't have blown in cellulose. . . '

Air tightness of the cans aside, the lights themselves may be dumping a bunch of heat into the environment.

Home Depot sells a re-branded CREE LED (linked below) which introduces much less heat (and uses less electricity) than a halogen or incandescent. As a side benefit, there is minimal airspace between the light and the drywall and minimal air leakage, so perhaps a double win.

Here is a link that might be useful: CREE LED


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RE: Spray foam in part of attic (seperate from rest of attic)

Athens - after raising three rowdy boys I know about shaking houses and having to repaint often! We found the can lights do increase the room temperature. We purchasespd a blend of hallogen and LED bulbs for various lighting schemes. We have been in our home almost 3 months. The halogen are still working, but we have had a problem with one LED burning out. I will hold judgment and say it was a bad bulb. The price of the bulbs is staggering and we need short-neck ones that cost more. I hope you get resolution soon.


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RE: Spray foam in part of attic (seperate from rest of attic)

Good point - LEDs will help with heat a lot when you have a lot of cans. My kitchen went from 600 watts to 100 which is a decent amount of extra heat. Crees are just one option but they may help seal a little.

motherof3 - I have a vacation rental with leds in ceiling fans and haven't had an issue yet (despite the fact they aren't approved for it). LEDs should be nearly forever - I'd say it was a bad bulb.


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RE: Spray foam in part of attic (seperate from rest of attic)

Athens I brought up your issue with my HVAC guy today as he was installing my range venting and he said "common problem that I find has more to do with ducting-HVAC than insulation." If the insulation passed inspection for the building I would look at ductwork first then AC "
Just thought you'd like a second opinion.


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RE: Spray foam in part of attic (seperate from rest of attic)

We're putting in a bunch of can lights. Can I assume that the air leakage problem would just be with those on the second floor or in an area with the roof/attic directly above? In other words, do I need to worry about this for the can lights in the first floor family room that has another floor (bedroom) above?


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RE: Spray foam in part of attic (seperate from rest of attic)

I don't know the answer to your question but wanted to add another thought to it - does it matter if you have batt insulation between floors? We have can lights all over the basement as well and then they put batts in between the floor trusses. . . . Does that stop some of the airflow? Obviously I can't get to the tops of those cans to insulate the top.


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RE: Spray foam in part of attic (seperate from rest of attic)

Leaking between floors is such a minor problem that you shouldn't even worry about it. I finished my basement with 12 cans and didn't give it a second thought. There are batts between the floors just because it wasn't finished right away although our builder always does that even if he finishes it right away.

Batts stop close to zero air flow.

Even if you didn't heat the basement, there are 2 levels of solid material blocking air flow - the drywall ceiling and the floor above (with subfloor), so the holes that cans create are only on one layer. Sure it would matter but nothing like an attic.


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RE: Spray foam in part of attic (seperate from rest of attic)

Great - so I won't worry about the kitchen and the basement :). Playroom is the big one and the hallway to the playroom . . .


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