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Adding Foam Board Insulation to Inside of Exterior Wall


BigRedDog's Avatar
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01-06-10, 11:43 AM   #1  
Adding Foam Board Insulation to Inside of Exterior Wall

I live in northern Utah very near the Idaho border (6,291 heating degree days and 72 cooling degree days). Please help me come up with the best solution to my two-part project:
1.I want to add insulation to an existing 2x4 exterior wall. The outside is of my mid-60's house is mostly brick, but there is one portion with stone veneer and wood siding. On this portion, I've pulled the gypsum board off the inside. There is only 1-1/2 inches of fiberglass batt insulation with a foil face (facing the inside). I'm thinking of finishing the wall like this (from the inside): -inch gypsum board, 1 inch of rigid foam insulation on the studs (I've been looking at 1 inch Foamular 250, which is available locally for $13 per 4x8 sheet), R13 or R15 fiberglass batt and foil facing with the facing stapled on the surface of the studs and then taped. For now, I'll leave the existing inch sheathing and stone veneer on the outside of the studs. Is the rigid foam board and the foil faced fiberglass the best way to go? I'm assuming the Foamular is a vapor retarder and that I still need a vapor barrier, correct or not?
2.In the future, I will probably remove the stone veneer and wood siding on this section of the house. Can I then add 1 more inch of foam board before I add new siding? In other words can I have foam board on the inside and ouside of the exterior wall?

I've already added insulation in the attic between and over the bottom of the roof trusses. The windows have been replaced with new, low-E, argon filled, vinyl framed windows. I have a high efficiency gas furnace and central air conditioning.

 
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Bud9051's Avatar
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01-06-10, 12:43 PM   #2  
I'll add a couple of links to put you to sleep tonight, but you are basically ok. Generally the VB goes on the warm side of the insulation and must be in contact with the air barrier. Sometimes the VB and AB are one in the same, but don't have to be as long as they are together.

Waste a case of caulking or some can foam while the walls are open to seal all holes you can find. Fire rated where holes pass up or down through the house. Investigate mineral batts, or wool batts, they have been in use in Europe and Canada for years and are starting to show up here. Much denser and will reduce convective air losses much better. The flyer I have in hand and plan to try is "Roxul", but there are others. Here's the reading.
http://www.efficiencyvermont.com/ste...ide_062507.pdf
Energy Savers: Vapor Barriers or Vapor Diffusion Retarders

Bud

 
BigRedDog's Avatar
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01-19-10, 12:25 PM   #3  
Your Opinions on Another Alternative

There is a cellulose insulation manufacturer in the valley where I live. They are a distributor for the Par/Pak vapor retarder and will rent me the blower to do dense pack cellulose in my walls. An 8-foot wide roll of the Par/Pak reinforced poly retarder is $170. (Roll is longer than I need now, but I'll use it as I work around the house). The machine rental is $20 for a weekend. The cellulose is $6 per bale. I only need 3 bales for the current project at 3.5 pounds per cubic foot. Other than the vapor retarder and the cellulose, all I'd need to buy or rent is a roofing stapler/tacker for the 3/4 X 1 staples to hold the barrier. I can buy a manual stapler for about $60. Don't know on the rental.

Is cellulose insulation worth the extra trouble/expense in the wall I mentioned in the earlier post? Does it really seal air movement better than fiberglass?

Thanks in advance for any advice.

Clifford


Last edited by BigRedDog; 01-19-10 at 12:43 PM.
 
Tolyn Ironhand's Avatar
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01-19-10, 12:48 PM   #4  
A hammer stapler is only about $25 Arrow HT50 Heavy Duty Hammer Tacker - HT50P at The Home Depot

Cellulose does do a better job than bats because it fills in all the nooks and crannies. Unless your very good at cutting, you will always have gaps with rigid foam.


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BigRedDog's Avatar
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01-19-10, 01:26 PM   #5  
Thanks and question about stapler

Thanks for the information about cellulose insulation.

I would rather buy the stapler you found for less money at Home Depot. I was told I need 1 x 3/4 inch staples, which require the more expensive Arrow HT-65 stapler.

Will the HT-50 stapler and the 1/2 inch staples do the job for me?

Thanks again!

 
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01-19-10, 02:07 PM   #6  
Not sure what Par/Pak reinforced poly is but if it is just a 6mil poly I would think a 1/2 staple would work just fine.

EDIT: Ok I found a site here: http://www.parpac.com/brochure_p3.html that I think is what you are describing. It appears that they are using a air stapler and really pulling the poly tight. I'm thinking you might need a wider crown on the stapler to do this. You might want to follow the manufactures suggestions.

Looks like it really fills the void though!


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