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Existing wall insulation


mikecsti's Avatar
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10-15-14, 07:37 AM   #1  
Existing wall insulation

Finally got to taking down my drywall in my my bedroom. My house was built 1961.
I thought the walls where 2x6 but there only 2x4 with 2 layers of 1/4" fiber board 1/4" old school foam board with alum. siding. some bays did not even have insulation and others that did the batts where not installed right. They never stapled the paper to the studs, so the drywall was crazy dirty from all the air movement in the wall. I live in cold zone update NY. I know R valves are more for code but how can I get the tightest and most efficient wall with only a 2x4 and doing so on the interior of the house? Seeing what I saw I mite just take one room a part at a time and reinsulated. I'm thinking caulk all holes and joints and seams then put in roxul batts that would give we a r15. would like double reflective and double bubble foil be good or like 1/2 of super tuff-r foam board?

The foil I would need a 1/4" air gap between it and the drywall. I'm not really keen on the idea of putting an air gap in the wall. It says by installing it this way will give me a r3.

The 1/2" foam board, do I need an air gap or can i put the drywall right to it? I know the tuff-r has foil paper on it so it acts like a vapor barrier so I would not need to add one. the 1/2" of foam is and r 3.3 they say.

By doing this all over my house would i see a big saving or not really? I would think with all the air movement in my walls right now I would see saving but not shore how much.

thanks

 
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10-15-14, 10:14 AM   #2  
Your current (previous) insulation averaged a dismal R-5 (educated guess) so installing r-15 is a major improvement. Adding r-3.3 additional will save you $15 per year (that's a wild guess). The point is one of diminishing returns.

In a hot climate the reflective foil surfaces have some benefits, but your cold climate they save almost nothing.

Next to r-value, air sealing is very high on the list. That dirty fiberglass you found is an indication of air leakage and heat loss. Go crazy with the sealing before the insulation goes in and then check the rest of the house, link attached.

Your Roxul will come without a paper or foil facing, friction fit. Be neat and cover it with a sheet of plastic on the inside. Then tape all seams and holes from the stapler (when you missed). The plastic is a vapor barrier while your drywall is your air barrier. Seal around any electrical boxes or wiring penetrations as well.
Bud

http://www.efficiencyvermont.com/ste...ide_062507.pdf

 
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10-16-14, 10:19 AM   #3  
Well I was thinking of the tuff-r too because as we know a 2x4 dose not insulate so I was thinking if I put the tuff up the whole wall studs and all will be sealed and 3.3.

Yep, plus in the winter the walls/dry wall is cold, and on all the exterior walls there is hot water base board. So I know I have major air leaks in the wall.

Thanks for the link, My attic is sealed and ready to go. Took care of that first.

Yep I know, yes I use great stuff around all outlet boxes and behind. Not shore on the r of that stuff but in a 2x4 I have about 1 1/2" in the back that I'm filling with the great stuff.

Dose it make sense to get one of the spray foam kits like green foam? There like R 7 per inch. The the wall would be more like r21 sealed.

Not shore if it worth the money to do it though. I mean this is a small room I'm doing first so with roxul batts, caulk, great stuff, I'm looking at like $100, plus two tuff-r for 40. It's about 64sqft the face of the wall. If I get the green foam I'm looking at the 200 kit and that's 390, plus shipping. It's four times the price!!

plus drywall, mud and so on.

 
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10-16-14, 10:53 AM   #4  
I associate the spray foam kits with larger projects. They aren't something where you can use 1/4 and the rest later, at least my experience. I even have the gun for the can foam, but find the throw away cans to be less expensive, unless it is a big project.

Studs aren't without some r-value (R-1.25 per inch) but a layer of foam over them is good. But the foil will not add much. A radiant barrier works when there is a significant difference in temperature, but a well insulated wall, that foil surface will be almost the same temp as the drywall. But if it makes you happy I won't say just make the insulation thicker. Oops, I said it.

Foam gets its r-value from air or whatever gas is used inside all of those bubbles. The material that forms the bubbles actually conducts heat, but it is very thin. Therefore, the great stuff will probably be about r3 or r-4 per inch, a lot of stuff and not as many bubbles. But don't get too hung up on counting the "r's". The performance of an air sealed wall vs a leaky one is huge. Add in that r-20 and you will be happy. A regular r-19 wall will typically have a surface temperature about 2 below the inside room temp when the outside is at 32.

"I mean this is a small room I'm doing first so with roxul batts, caulk, great stuff, I'm looking at like $100, plus two tuff-r for 40." You will be happy.

Bud

 
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10-17-14, 06:17 AM   #5  
Yep I know the, the 200 kit was just good for that room with 3 1/2" of foam.

I know I keep looking at r valves here.

So I'm going to use the roxul and the 1/2" of tuff-r on the wall I think that would be the most coast to saving to do for my house.

So my questions, what's the best way to install the tuff-r, screws or caulk/glow they make for it or both?

Can I put the drywall right up to the tuff with no air space?

The tuff-r has foil on both sides of it so If I install it and caulk around the edges and tap the joints with there tape for the tuff is that my vapor barrier or do I still need to add the plastic also?

 
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10-17-14, 06:38 AM   #6  
Taped the tuff-r will be your vapor barrier, no plastic needed. I wouldn't bother with a space between the drywall and the foil.

Screw and glue the tuff-r. The screws will hold it in place until the glue dries.

Bud

 
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10-18-14, 08:10 PM   #7  
Ok thanks for all the help and info.

 
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