What type of insulation for the house?

[mclear]

My contractor has giving me three options for insulation in the new home. We have 2x6 framing:

1) 1" of Closed Cell foam and then fiberglass batting (about $14,000)

2) Open cell foam sprayed only. Sprayed in the roof rafters but not between the attic and 2nd floor. Insulating contractor says this creates an environment where the attic is only 10 degrees different than the house (colder in winter, warmer in summer) (About $20,000)

3) Closed celled foam entirely (still waiting on quotes)

we are currently trying to get more quotes for the open cell foam.


Any thoughts?

[parnelli]

I don't know where the house is, but I vote closed cell plus fiberglass unless the quotes for all closed cell come in at something you can afford.

Open cell isn't going to retard vapor and the all closed cell would be preferred but typically pricey.

[pelligrini]

Insulating the roof is an appealing option. I'm seeing it done more and more often.

Closed cell has better insulating properties, and it does form a vapor barrier. It's also the most expensive.

I'm still not totally sold on an entirely sealed envelope (vapor barrier). You'll need to control humidity inside the house and should provide some sort of fresh air intake for the HVAC. I've seen many different positions on it from various manufacturers and building systems. If things are installed improperly a lot of factors can come together and cause problems, sometimes major; sick house, raining in walls & attics (condensation problems). I've seen more cases of condensation problems when weather barriers (Tyvek) and vapor barriers are used in the same wall and in the wrong places. When particular temperature and humidity variances occur water can get trapped in the wall & house.

[parnelli]

I'm still not totally sold on an entirely sealed envelope (vapor barrier). You'll need to control humidity inside the house and should provide some sort of fresh air intake for the HVAC. I've seen many different positions on it from various manufacturers and building systems. If things are installed improperly a lot of factors can come together and cause problems, sometimes major; sick house, raining in walls & attics (condensation problems). I've seen more cases of condensation problems when weather barriers (Tyvek) and vapor barriers are used in the same wall and in the wrong places. When particular temperature and humidity variances occur water can get trapped in the wall & house.

Absolutely. The days of throwing poly on the wall without thinking and trapping moisture appear to be ending. You've got to always be thinking- when this gets wet/moisture- where's it going to dry to? Inside or outside. Having stuff trapped with no direction to dry to is inviting trouble

[mclear]

I'm in northern NJ. I do have concerns regarding the moisture trapping of the closed cell foam.

[pelligrini]

It's just not closed cell that can be the problem, it can happen with about any insulation method given the right (or improper) circumstances & installation methods.

Methods also vary per region. Around here we're more concerned with cooling days. The conditioned envelope is usually cooler than the outside.

[jackellis]

We used blown-in fiberglass. So far, our heating bills are very modest (~125/month during the coldest months). I don't recommend open cell foam. Closed cell foam is pretty expensive, though it does the best job of preventing air infiltration. If your house ends up being really tight, you will need a source of fresh air and a heat exchanger.

Build tight and insulate well. If energy prices spike, as they do from time to time, you can still afford to be comfortable, and low energy bills should be a great selling point.

[AZDude]

I built my home about 3 years ago with open cell foam insulation. I love it!! I went with the open cell because of the breathability. I was told that the closed cell is mostly for rooftops - exterior applications.

I have a full thermal envelope - caulked bottom plate, foam in walls, and foam up the top chord of the trusses - underside of the roof. If you use regular shingles, this might void the warranty. I have 2x6 walls full of foam and about 8" thick in the attic. I do heat & cool the attic so that I do not have any moisture problems. All of my ducts are in a conditioned attic, not the normal 150 degree attic (Arizona), which is a huge plus! I have a few thermometers at various spots in the attic to monitor temp, which it is never more than 5 degrees different than inside the house even when it is 115 outside here in the AZ desert. I do have fresh air intakes. With the house being sealed I was able to downsize the HVAC system a little bit. I have double the sqft of my previous house, but more than triple the volume and my bills have been at most 14% higher with most months being about the same. The foam insulation paired with good quality windows are definitely worth the money. I do think I got a really good price on my insulation, which helped in the decision.

[toolguy1000]

I'm in northern NJ. I do have concerns regarding the moisture trapping of the closed cell foam.

i'm east of you in westchester cty, ny. just curious...is your architect leed certified and if yes, what does he recommend?

[dbhost]

Not sure about Joisey, but down bout these parts, I would go with closed cell. I am not crazy about the idea of insulating the bottom side of the roof though. I would want a radiant barrier there, and insulation between attic and ceiling...

[Monyet]

Not to add to the confusion but I've found many useful articles about proper construction practices here:

www.buildingscience.com (I'm sure others on the board have seen this)

I've attached an article about cellulose insulation (just one of many about insulation), there's many more to read up on about other subjects.
Yes I do realize it's not listed as one of your choices, and I don't mean to muck up the conversation, just offering another perspective.

edit:
can't upload a pdf file:

Here's the link:
http://www.buildingscience.com/docum...dont-be-dense/

[jackellis]

All of my ducts are in a conditioned attic, not the normal 150 degree attic (Arizona), which is a huge plus! I have a few thermometers at various spots in the attic to monitor temp, which it is never more than 5 degrees different than inside the house even when it is 115 outside here in the AZ desert.

Keeping the attic cool is critical because it's hot air trapped in the attic that heats up your house more than it is the outside air. Because cedar shakes breathe a bit, our home in the Bay Area was more comfortable before we replaced the roof with composition shingles even though we added ventilation.

I wish I'd known more about the "cool roof" coatings that reflect UV because that would have helped. It might also you to install allow insulation under the roof deck without compromising the useful life of the shingles.