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# spray foam insulation.. help understand

## spray foam insulation.. help understand

#1
02-03-16, 02:17 PM
Member
Join Date: Feb 2014
Posts: 10
spray foam insulation.. help understand

I am trying to plan the insulation I am going to do when I get to that stage in my basement. My basement is a 1/2 basement, and has roughly 650 board feet. I have seen the touch-n-seal kits that says it expands 30x. the kit claims to have 200 board feet. I used an online calculator to estimate how much I needed and I am so confused. I put in the values that I had 650 Board feet, and wanted a 3" thickness. It told me that I needed 1,900 board feet.

So here is my question. If it claims to expand 30x, then if I spray the foam 1" thick on the wall, then should it not expand to 30" in a confined space?

When they say it has 200 board feet, are they saying 200 board feet expanded, or un-expanded? Has anyone here installed the spray foam insulation in their 1/2 basement (roughly 650 sq foot basement), and if so, how much did you need to complete the job? what brand did you buy?

If I really need 1,900 BF, then maybe I will just lines the stud pockets for seal and fireblocking and fill the rest of the pocket space with fiberglass.

thanks.

#2
02-03-16, 03:57 PM
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Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
I think you are confusing the terms board feet and square feet. A board foot is a piece that is one foot wide, one foot long and one inch thick. 650 square feet of insulation 3 inches thick would be 1,950 board feet of insulation.

If it claims to expand 30x, then if I spray the foam 1" thick on the wall, then should it not expand to 30" in a confined space?
You don't spray it on one inch thick, only a fraction of an inch. If you want it to fill a stud space then the initial spray will be about one-eighth of an inch in thickness. This IS hard to estimate as the material starts to foam up almost as soon as it comes out the nozzle. You MUST keep the spray gun moving all the time the trigger is pulled or you will end up with a HUGE gob of expanding foam where you stopped moving.

When they say it has 200 board feet, are they saying 200 board feet expanded, or un-expanded?
Expanded, under optimal conditions. The manufacturers all want the room temperature to be in the upper 60s (degrees F.) and optimally the canisters to be in the middle 70s. Cooler temperatures WILL yield less than the stated amount of expanded foam. Further, there IS a learning curve applying enough, but not too much, foam to fill the cavity without overfilling. Anything that expands beyond the face of the studs is just lost, you cannot reuse it for anything.

Has anyone here installed the spray foam insulation in their 1/2 basement (roughly 650 sq foot basement), and if so, how much did you need to complete the job? what brand did you buy?
I don't know what a 1/2 basement is but I don't think I need to know. I used a kit to fill the outside wall in my back bathroom where the water and sewer vent pipes were and also where the studs were not at standard distances. Using any material other than foam would have been a nightmare. I don't remember the brand, maybe Handi Foam? The kit had a pair of tanks, about the size of 11 pound propane tanks, maybe about 10-12 inches in diameter and about 15-18 inches tall. This WAS back in about 2003 and the cost of the kit was somewhere between \$120 and \$175. The space it filled was maybe 4 feet wide and 8 feet tall. The price of a similar kit today is about double, maybe \$250 to \$450, in other words ungodly expensive. Heck, it was ungodly expensive back when I did it.

Rather than using fiberglass, which I consider to be an inferior (but CHEAP) insulation, I would suggest using Roxul mineral wool batts. The Roxul is about twice the cost of fiberglass but much easier to work with and generally a much better product all around.

OR, call around to some insulation contractors that do foam. The cost of having it done professionally is actually less in many cases than using the DIY kits. It will still be expensive but it will also be a superior job with superior materials. I personally prefer closed cell, two pound density but in your particular case I would listen to what the pro specifies. If you go this route be sure to get multiple bids.

#3
02-03-16, 04:55 PM
Member
Join Date: Feb 2014
Posts: 10
I will call around and get bids. I am guessing that I do not need the entire stud pocket filled, since touch-n-seal is 7.2 R-value per inch. so if I did 2 inches, that would be 14.4 with zero airflow through the walls, and it would act as my fire barrier, vapor barrier and draft sealer. but going 2" thick would reduce my cost.

Wow, closed cell foam is very expensive if it is 297.00 for 600 board foot.

My basement is pretty much a box with all wall length totally 85ft. the walls are 7.5 ft. tall. so since the board foot is 1'x1', that is 637.5 sq foot depth not included.

#4
02-03-16, 05:38 PM
Member
Join Date: Oct 2008
Location: New England
Posts: 9,460
There are many threads here about finishing basements and many steps before you add the insulation. I'll add a popular reference link on basement insulation, but basically a layer of continuous rigid foam, then your stud wall, then fill with batt insulation seems to be the most popular and lowest risk for mold.
Understanding Basements | Building Science Corporation

Bud