Ideas for an Affordable and High-Performance Insulation Package
Hello GBA Community,
I am building a house. Because of the increase in building costs I am going to be my own general contractor (I am very organized and very much a DIY kind of person).
But, I did want to farm out the insulation to a subcontractor. I had some nice conversations with a local insulation contractor. He seemed smart and concerned about the environment. He uses a “thermo-foil” type method. He sounded like a can do kind of guy. Even knowing that my house budget was tight, he never even hinted that this might cost a lot of money.
My central Idaho mountain house is basically a 2,200 sq ft footprint single level ranch style with flat ceilings (trussed roof). The garage is detached and is a small 3 car (but I was not going to insulate or drywall that just yet). He included the garage in his bid. And the total bid for a well insulated house? $45,000. He offered a lower option at a whopping $37,000. It took me a while to get off the floor to write this post 🙂
Is this what it costs? If we intend on saving the planet, how can we only offer great insulation to the wealthy? That is about as hypocritical as it gets.
So, now I am looking at doing the insulation ourselves. My assessment is this:
r-30 faced fiberglass batts in the walls. 2×6
a double layer of fiberglass rolls in the attics (to get to at least r-60) The truss heel height is 16″ .
maybe spray foam in the soffit venting baffles (but I have to look online to see if this is DIY).
Insulate the crawl with foam board????
Any of you practical minded insulation folks out there…I would really appreciate a “recipe” of what to place to get close to the same energy conservation that the wealthy can buy. I am willing to spend more for efficiency. But that bid breaks the bank.
Thanks in advance.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Blackfeet,
It's hard to say whether or not that price is good or bad without more information. If he was layering up 8" cork boards on the exterior for instance then that price is a bargain.
I googled 'thermo-foil' and saw lots of radiant barrier/foil -bubble-wrap. If that is what he was propsing then I would run, not walk, away.
Insulation doesn't have to cost much. Cellulose and loose fill fiberglass are normally very economical. Insulation costs constituted about 4% ($15k) of my home's total cost to build. Our walls are R-45, ceiling R-85, sub-slab R-24.
Hello Rick and thanks for your response. Would you mind sharing with all of us how you got the R 45 in your walls. That’s amazing! May as well tell us about the ceiling as well.
curious as to why u advised for him to run if thermofoil meant radiant barrier type stuff, cuz i thought they are good. does polyiso alumiflash fit into this category? pls enlighten; tnx
I agree with what Rick says. I'm not familiar with a "thermo-foil" system; at first I thought you meant foil-faced polyiso foam, which is among the "greener" foams but not really environmentally friendly unless you get it recycled. If your contractor is suggesting a bubble wrap product they should not be trusted.
If you search this site you will find dozens of articles and thousands of Q+As about insulation. Every project is unique so it's hard to recommend a single approach.
Blackfeet, if you're into DIY then don't sub out insulation--this is one of the easiest ways to save a bunch of money. Sounds like your design also lends itself to simple and inexpensive DIY. With your trusses you'll be able to self-install loose-fill cellulose with only one helper and a rental machine--this is the green standard for attics, bar none. Fiberglass batts in the wall is a reasonable approach; if you can at all swing it go for continuous exterior foam, but don't die on that hill if it's too complicated for you. A crawlspace is easy to "encapsulate" with rigid foam if you do it at the time of construction. You really don't need any spray foam at all in this build; the only place it is remotely justifiable is in the rim joist. And DIYing the insulation means you'll be able to monitor airsealing of the sheathing, which is arguably far more important than the insulation.
You can probably go with blown cellulose in the attic. Blown insulation, assuming you’re doing the usual “insulate the attic floor” thing, is about the best bang for the buck insulation method and material you can do. Box stores usually include a blower rental at no cost with a large enough insulation purchase (and you’re sure to be buying enough for that if you’re doing a new house). I would absolutely go this route if at all possible.
I prefer mineral wool for the walls, but it’s not cheap. Fiberglass can perform well if you take your time to do a good job. The denser batts (R15 instead of R11 for a 2x4 size cavity, for example) are better than the usual density stuff but usually requires a special order. I’d check on pricing for that though and special order it if the cost premium isn’t too bad. The higher density fiberglass behaves closer to mineral wool in terms of holding its shape, and that makes it easier to get a good fit when installing the batts.
Spray foam should be reserved for niche areas like unvented cathedral ceilings and sometimes rim joists. If you’re going to be using exterior rigid foam, and I highly recommend using it if you can, then you can often avoid the need for spray foam in the rim joist area too. Using reclaimed or factory second rigid foam can save you some more
Money too.
BE SURE to do a good job of AIR SEALING while everything is open!!! That can’t be stressed enough. Get a foam gun for canned foam, and some urethane caulk, and go to town before closing things up. You gain a lot of performance at relatively low cost from air sealing, and since almost all of the cost for that is in labor, you save a lot with DIY here. With the house open, air sealing isn’t very difficult to do. There are lots of articles here on GBA about how to do it. Be sure to get the foam gun too, it both makes things much easier, but it also lets you use the canned foam more efficiently because the gun can be turned off and reused again later, even days or weeks later. With the usual straw cans, you get one shot and then they’re done regardless of if you used all of the material inside or not.
It might be worth considering drywall gaskets too (the gun foam kind) if you want to do airtight drywall.
Bill
I had an insulation contractor add R-60 fiberglass to my attic in 2006. 1,664 square feet for under $2,000.00. I know that was a good price but it will give you a starting point on attic insulation. The price quoted you was absurd. Insulation and air sealing can be DIY and if committed you will most likely get a superior result than hiring out. Standard insulation and air sealing materials are cheap, should not run more than 5k for the entire house.
My local big box is getting just a bit over .40 per sf for unfaced R-19
https://www.menards.com/main/building-materials/insulation/insulation-rolls-batts/guardian-r-19-unfaced-fiberglass-insulation-batt-15-25-x-93-87-2-sq-ft/510516/p-1444437006428-c-5780.htm?tid=4735317468976193115&ipos=16
I DIYd my house addition and am now tackling the renovation (early winter isn't helping). I'm in zone 5. I used the REMOTE system http://cchrc.org/remote-walls/ which I found to be perfect for do-it-yourselfers. I applied all of the exterior insulation, batt insulation, and blown-in insulation. The addition ended up with R35 walls and R60 roof insulation values and is very energy efficient.
You have some good advise above, but having said that, in my 35+ years in this business, every time I know a homeowner, who is not in the business, becoming his own GC, the price goes up in almost every thing. I'm sure your insulation bid was to pay for all company bonuses. 😱
I just had insulation done last year on a new build. 1450sqft two level home. Two layers of batts in a sloped ceiling for R-60 and blown-in fiberglass into 2x6 stud bays throughout house. They put batts in the floor system too.
They had a crew of three and did this work in one long day and charged $5,500 for the whole thing. And this is in a high cost of living area. I thought it was a bargain for the amount and quality of work done. This also included a vapor barrier on the floor of the crawl.
> r-30 faced fiberglass batts in the walls. 2×6
Did he explain that R30 of fiberglass in a 6" wall is a waste of money and will yield about R21?
Don't focus on insulation and neglect air sealing and moisture performance. See Table 2 A or B here for the latter.
Exterior insulation (unfaced EPS) is highly recommended, even if it's less than typical:
https://www.continuousinsulation.org/content/2021-ibc-and-irc-adopt-improved-vapor-retarder-requirements
Test the air sealing with a blower door.
Someone else mentioned it, but compressing R30 into a 5.5" wall cavity is wasted effort, to say nothing of compromised results. Not only do you NOT get an R value of 30 (more like 20 or 21) but that is a significant amount of compression as an R30 batt is about 10" thick. That could result in some drywall bowing as well. For a 5.5" stud cavity, fiberglass insulation manufacturers make high density wall batts up to R23 at the 5.5" thickness. In your area, Menards can get you that product, although it might have to be ordered. High density fiberglass is more expensive initially than is regular density (R19) product, but from a thermal performance perspective, well worth the initial cost difference. Speaking from more than 50 years of experience in contracting and manufacturing, I personally find the high density products easier to work with than the standard density products. They are gutsier, fabricate more easily and stay where you put them with no sag.
For someone willing to pay attention to the actual installation process, installing fiberglass batts is not difficult. In your case, not having to rush through the installation process in order to "get it covered up" like occurs in the production building sector, will allow you to do a high quality job. There is really only one time to get the insulation (and AIR SEALING) right from the beginning. So regardless of the products that you use, take your time and install them correctly. There are lots of manufacturer and independent videos available on proper installation techniques.
I just want to thank everyone who gave such thoughtful posts and advice. I feel much better informed And now we are encouraged to do this job ourselves. After all what are teenage sons for? I hope you all have a fabulous Christmas and I look forward to any more comments.