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kirkclean · 01-15-2011, 10:21 PM

We are building a house and are ready to insulate. Our friend who is a contractor will have a whole lot of r-30 they will be removing from a commercial building that we can have for free. We live in the valley in N.CA and it does get hot, but not very cold. These are my questions:
1. We need r-38 in the ceiling. We have a large attic that will stay unconditioned for now and need to insulate below this area. We have 12" trusses with with the entire floor of the attic sheeted. Can I double up the r-30 even though it will squish it and leave now space for a flow above the insulation?
2. We have 2x6 walls. Can we squish the r-30 into the walls?
Thanks for any help at all.
Kirk.

**kok328** · 01-16-2011, 06:56 AM

compressing insulation reduces it's effectiveness and rating.
So for example; if r38 is 14", compressing it to 12" it will no longer be r38.

eokhuijzen · 01-16-2011, 05:24 PM

Advice that could save you thousands? DONT SKIMP ON THE RIGHT INSULLATION! This could actually lessen the years of your roof! I just put on a new roof. They have a new type of roof that is more efficient and vents from the top. But this meant I needed new insullation.....a certain type to go with the roof. My roofer and best friend said it becomes not a matter of cold or hot but that if I do not use the right insullation for my type of roof that my roof will only last 3 - 5 years. I speant $8,000 on my roof (it was so bad the wood even had to be replaced) and that was through a friend! Others quoted me $15-$20,000! It would not be worth it to go cheap on it. If you need 38 USE 38. It will save you money in the long run.

joecaption · 01-16-2011, 09:35 PM

What is theis "special" insulation you keep talking about. Most new roofs are all vented out the peak of the roof with a ridge vent and just reguler insualtion is used in the attics.
Recommended Levels of Insulation : ENERGY STAR

kirkclean · 01-17-2011, 10:09 PM

No I do not want to skimp. I am wondering if this offer can be equal to or better than r-38 in ceiling or r-19 in the walls.

BrianKiernan · 02-09-2011, 06:43 PM

Bad Bad Bad Idea. Compressing insulation in the walls would greatly diminish the effectiveness of the insulation.

Also doubling the insulation in the ceiling would create a double vapor barrier which would trap moisture and create mold.

I also believe that the building inspector would fail that inspection.

kirkclean · 02-10-2011, 01:51 AM

It ended up being all r-38 that was in perfect condition. So, no problems at all. We then just put r-19 in the walls. There was so much insulation though, that we actually tore the r-38 into 3 pieces and then put that in the interior walls for sound insulation.
Thanks.