DIY Foam Insulation for a fraction of the cost! (best insulator out there)

[Miss Growing Green]

So, we recently converted a sunroom to a bathroom and entryway in our 1940's house which was really poorly insulated.
We live in Montana and really wanted an energy efficient building without the high price tag...
Closed-cell spray foam insulation is about the best insulator out there (better than fiberglass or any kind of blow in), but it usually isn't a DIY job and costs *a lot* of money compared to other methods.
We figured out an awesome work around that involved rigid foam boards and gave us the same R-Value as the spray foam for almost a third the price!
I outlined our project step-by-step in one of my recent blog posts:

http://www.thegrowinggreen.com/diy-foam-insulation-construction-cost-saving-measures/

[Rural]

That's a great, tight job you did there. The best thing about our (professional) spray foam insulation here is that it's a full air seal as well as being R35 in the walls (6 inch nominal/ 5 inch really) and R56 on the roof deck (8 inches thick). Usually foam board won't approach that sort of air seal, but yours looks like you took the time to fit things really well and then sealed any visible spots.

[Miss Growing Green]

Thanks Rural!  Yeah, the air seal is really important.  Unfortunately, we were working with 2x4 walls, so the best we could get was R-19.3... sounds like you have 2x6 walls?  That R-35 must be so nice!

[Rural]

Yes, 2x6 in the exterior framed walls (three walls are poured concrete and earth bermed). My husband did the design and he and my father did the build, so we ran the numbers and decided the 2x6 framing would pay off quickly. A lot of ours is keeping cool inside in summer here in the South, but it helps a lot in winter, too -- would help more if I agreed to cover the windows, but even with huge expanses of glass, we stay above 50 inside in winter without heating (we do heat as I'm a wimp, but I know this from last winter before we moved in).

Edited because stupid ipad "correction"

[Jack]

Thanks Rural!  Yeah, the air seal is really important.  Unfortunately, we were working with 2x4 walls, so the best we could get was R-19.3... sounds like you have 2x6 walls?  That R-35 must be so nice!

I occasionally find myself wondering if it would be worth it either to shim out 2x4 exterior walls to 2x6 depth (or add a second layer of 2x4 studs, offset between the existing studs with a 2x2 top and bottom plate) and then reinsulate and redrywall or to remove the siding, add 2" rigid foam board on the exterior and reinstall.

[Cromacster]

Thanks Rural!  Yeah, the air seal is really important.  Unfortunately, we were working with 2x4 walls, so the best we could get was R-19.3... sounds like you have 2x6 walls?  That R-35 must be so nice!

I occasionally find myself wondering if it would be worth it either to shim out 2x4 exterior walls to 2x6 depth (or add a second layer of 2x4 studs, offset between the existing studs with a 2x2 top and bottom plate) and then reinsulate and redrywall or to remove the siding, add 2" rigid foam board on the exterior and reinstall.

For a job the intensive the payback is going to be a long time.  Most of the heat loss in a house is through the attic/roof.  That should be your first plan of attack, along with air sealing everything you can.  If you are refurbing/remodeling/residing or otherwise doing something where you are down to the studs anyway, then it might be worth your time.  As was the case of the OP.

OP: Really nice job!  A Major improvement.

[Milspecstache]

Nice job.  I am considering doing the same thing in a garage that I have and heat when working on cars/projects.

[zolotiyeruki]

Nice!  I did something very similar in our basement a couple years ago--I discovered that the original builder had not sealed up any of the penetrations in our look-out basement, and there was lots of dirt/mildew on the fiberglass batts.  I cut 2" XPS foam to fit each stud bay with a 1/4"-1/2" gap around all four sides, glued in the XPS, then used spray foam around all the edges to get a nice tight seal.  It was a fair bit of work, but I also took that opportunity to seal up all the holes in the wall (spigots, electrical service, outlet boxes, poorly-sealed sill plate, etc).  The exterior walls are 2x6 framing, so I filled in the remainder of the stud bays with regular R-13 kraft-faced batts purchased at a yard sale.  The basement was a whole lot warmer the following winter :)

[Exflyboy]

Miss Growing Green,

I tried to post this to your blog but it didn't seem to take so if you get this twice you know why.

Did the building inspector have any issues with the Great stuff foam sealant? Reason I ask is that I believe it is pretty combustible and foam insulation I believe is treated with a fire retardant.

Of course it is also behind the sheetrock which is your primary resistance to fire.

Thanks

Frank

[Miss Growing Green]

Frank,

Sorry, new comments on my blog have to be approved by me before they show up (I approved yours so it should be there now).

Nope, he didn't say anything about it one way or the other... so I'm not sure if he just overlooked it or if it was "okay".  But, isn't Great Stuff designed to fill gaps and cracks in walls, windows, floors, etc?  I mean, weren't we essentially using it for its intended purpose?

Thanks for the heads up!

[TomTX]

There is a fire-barrier rated version of Great Stuff at my local Home Depot. I have a can in the garage for when I seal the perforations in my attic.

Attic plan:

1) Additional lighting in attic. Done.

2) Catwalks to move around on up there, especially after Step 4. 80% done.

3) Foam every perforation/opening I can.

4) Add reflective foil/bubble insulation on the outside of the stupid kneewall.

5) Blow cellulose over existing blown fiberglass (which is probably overfluffed, and has definite low spots.

[Exflyboy]

Right now I am tracking down air leaks in the house we doubled in size and remodelled..

I am amazed at the little gaps I never even though of as being significiant that are letting in a lot of drafts

In less than a days works I have made this place considerable more toasty and the thermostat has been turned down by a full 4 degrees (F) for the same comfort level.

And I'm still finding more leaks.

Definately pays to make sure there are ZERO gaps between the inside of the house and into the crawlspace etc.

Frank

[zolotiyeruki]

You're making me want to go into our attic and make sure all the penetrations are sealed.  Given the original (low to non-existent) sealing of penetrations, it wouldn't surprise me to find a lot of air leaks.

I just wish I had my own FLIR camera (or a cheap, nearby place to rent one).

[Exflyboy]

You're making me want to go into our attic and make sure all the penetrations are sealed.  Given the original (low to non-existent) sealing of penetrations, it wouldn't surprise me to find a lot of air leaks.

I just wish I had my own FLIR camera (or a cheap, nearby place to rent one).

wet your fingernail and put it in front of the suspected leak.. Its by far the most sensitive place on the human body to detect air movement. (one of my old HVAC techs told me this). Surprisingly effective.

I have just torn the carpet up in the closet in the spare room... oh my word there is a 3/8th wide gap in the floor letting in a virtual gale!

Just caulked it up!

Frank