Insulation in Attic

[msmity29]

I am having a home built in the far west burbs of Chicago and the builder uses batt insulation in the attic with more insulation blown over the top. These two combined make-up a R-38 value. I have read that R-49 is recommended in our area. Should I inquire into upgrading or maybe possibly blow in more myself? Will the extra insulation make that dramatic of a difference? Thanks!

[giddonah]

I was working in a house that only had what looked like 7" batts in the attic floor. I added a full layer of 6.5" more to the whole attic, and the first night the owner said she woke up in the morning sweating (after turning the furnace off for the night before bed, as usual). She now just runs the furnace a little in the morning and night, and then shuts it off.

I don't have an objective answer, just sharing an experience.

[Vector]

Wonder why the batts at all? Just blowing in the full R-38 would seem to be faster and cheaper, and still get you R-38. But whatever they want to do...

R-38 is ~16" of fiberglass. More is, of course, better in this case, but there's also a point of diminishing returns, which depends on your house, your budget, etc. R-38 is code here in MN too, but we went with R-44 in the attic. Any more and we would have had nothing but insulation in the attic (the attic is only about 5' high, and once you put in 2' of insulation, you're now 4' from the wall on a 6/12 pitch, so any more we added would only insulate the very center of the house).

[msmity29]

I know most of the builders in the area advertise R-30 so I'm assuming code is that.

[David]

Code = Minimum acceptable. I used to live in chicago, and you definitely want the R38. R49 may not be worth it. Inquire about the cost and report back.

FYI - In most cases, it'll be cheaper for builder to have the sub install more than it would be for you to hire the sub yourself. Ditto for DIY, usually cheaper for builder to take care of it than you. Don't be afraid to call around yourself and get quotes, but I don't think you'll get it done cheaper than the builder. That's just the way insulation pricing works.

[CThomp]

John Manville makes an R-38 makes an insulation that is 10.25" thick. You can get it at Home Depot. It's their closed cell "comfort therm" insulation. I plan on putting this in my attic when I get to that point. I'll probably put a radiant barrier up there as well. I've only got like 4:12 pitch so I don't have much room either. Put I can actually slide that comfort therm stuff into place.

[msmity29]

Sounds like R-38 maybe sufficient. I will have to see how much extra the builder would charge though. Thanks for all the advice!

[David]

Sounds like R-38 maybe sufficient. I will have to see how much extra the builder would charge though. Thanks for all the advice!

Just don't get tunnel vision here. Insulation is a component of the building's performance. Just like the windows, HVAC system, etc. They are all links in the chain. To get the strongest chain, you need the weakest link to be as strong as possible.

I've seen your posts on windows, this one on insulation, and I think you have a couple of others. But there are still many more things we need to know to give you the best advice. Even if you could load it to the hilt with insulation to R60 or R80 for just $2,000, it does NOT mean it would be $2,000 well spent, though some would probably disagree with me.

For instance, using OVE techniques is still uncommon, though it can save money and help provide a more insulated home. Using passive solar heating can help reduce utility bills, too. Maybe geothermal would benefit you. Using tight seals around the drywall on exterrior walls (part of the Airtight Drywall Approach) helps keep air movement to a minimum - reducing bills, too. Do they perform a blower door test (tests air leakage)?Will your builder have the HVAC sub perform a load calculation? WHERE DO YOU LIVE? That's just the tip of the iceberg. ;-)