# foam calculator



## dweeter (Dec 5, 2009)

Hi. I am looking at buying one of those 2 part foam insulation kits for a room-remodel job. The old sheetrock will be out, so I figured I might as well replace the old worthless fiberglass insulation with some foam.

But when the package says 200 board feet at 1 inch (roughly 5.5 r value per inch) does that refer to the product's wet/applied value of 1 inch--that is, prior to the foam expanding?

What I am getting at is this: how much does 1 inch of wet/immediately applied foam expand? Does 1 inch expand out to become four inches or so? So in that case, when the kit says it covers 200 board feet at 1 inch, does it actually cover 200 board feet with a finished, expanded total of 4 inches of foam (roughly an r value of 20)? 

Thanks, as always.


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## Windows on Wash (Aug 30, 2011)

How many square feet? What type of foam?


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## joecaption (Nov 30, 2011)

Never once seen a cost effective DIY foam kit.
Why do you think the fiberglass is worthless.
Way more info needed.
No one knows where you are so hard to suggest what's needed.
What are you trying to insulate, walls ceiling?
The whole house?


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## beenthere (Oct 11, 2008)

joecaption said:


> Never once seen a cost effective DIY foam kit.
> Why do you think the fiberglass is worthless.
> 
> Fiberglass doesn't stop air movement. Foam will greatly reduce the air infiltration to that room.
> ...



By his opening post, it looks like he is only interested in 1 room.


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## beenthere (Oct 11, 2008)

dweeter said:


> Hi. I am looking at buying one of those 2 part foam insulation kits for a room-remodel job. The old sheetrock will be out, so I figured I might as well replace the old worthless fiberglass insulation with some foam.
> 
> But when the package says 200 board feet at 1 inch (roughly 5.5 r value per inch) does that refer to the product's wet/applied value of 1 inch--that is, prior to the foam expanding?
> 
> ...



Generally, it refers to the expanded thickness.


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## dweeter (Dec 5, 2009)

Thanks, Beenthere. Your reply is all I needed. Not going to bother to answer the other questions from Joecaption--I'm not sure they were asked in a spirit of helpfulness to begin with--but if anyone wants to know why I considered the fiberglass worthless it is because it was home to a red squirrel or a chipmunk and is full of nuts and holes. Might be cost effective to replace it at this stage.


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## premington (Feb 19, 2015)

I've used the DIY foam kits when remodeling a below-grade room. I purchased a 200 sq. ft. kit. The kit is in board feet (1"x1"x12"), expended. I found the kit to be pretty true to the expanded amount. The area I foamed wasn't 200 sq. ft, but about 60 sq. ft. I was able to get a little over 3" of expanded foam on the wall space. This covered the block to the studs of a wall we installed in front of the foam. We then insulated in the studs, over the foam, and that rooms is fantastic with holding heat.

When using the foam, you need to install it at prime temperatures to get the most expansion possible. The wall needs to be at a specific temperature range (consult your instructions--it'll tell you this range), and the foam kit also needs to be warmed up. I drew up a warm bath of I think it was around 80f and put the canisters in this for an hour or so. Swirled the contents around every so often, then put it back in the bath. I made sure the canister contents were warm before using the kit. Again, follow your instructions.

Once everything was ready to go, the kit I used was pretty true to the square footage they advertized. I did notice one canister emptied a little before the other did. That left some unexpanded material over the foam, but I just ignored that.

Good luck!

-Paul


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## dweeter (Dec 5, 2009)

Thanks, Paul. Big help! I appreciate it.


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## Greg.Now (Feb 23, 2015)

premington said:


> I've used the DIY foam kits when remodeling a below-grade room. I purchased a 200 sq. ft. kit. The kit is in board feet (1"x1"x12"), expended. I found the kit to be pretty true to the expanded amount. The area I foamed wasn't 200 sq. ft, but about 60 sq. ft. I was able to get a little over 3" of expanded foam on the wall space. This covered the block to the studs of a wall we installed in front of the foam. We then insulated in the studs, over the foam, and that rooms is fantastic with holding heat.
> 
> When using the foam, you need to install it at prime temperatures to get the most expansion possible. The wall needs to be at a specific temperature range (consult your instructions--it'll tell you this range), and the foam kit also needs to be warmed up. I drew up a warm bath of I think it was around 80f and put the canisters in this for an hour or so. Swirled the contents around every so often, then put it back in the bath. I made sure the canister contents were warm before using the kit. Again, follow your instructions.
> 
> ...


Well that pretty much sums it up I guess. @dweeter you still havn't posted where you are from though. You might get more info from the other guys if you post a budget, time-frame and location.


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## premington (Feb 19, 2015)

My reply above messed up on the dimensions of a board foot. It would have been 12"x12"x1". I typoed and missed adding a 2 to one of the dimensions.

Oh well... I guess I'm human. :wink:


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## Ocelaris (Oct 9, 2012)

How thick can you spray on the foam? I thought if you sprayed more than 1" it would slide off? For example if the original poster had 100 square feet and since typically the smallest kit comes in 200 board foot, could he get 2" worth of foam? 

Not to detract from the original poster's thread, but I have about 300 board feet, and so it's cheaper to buy the 600 board feet than 2x200 board foot kits, so I was just wondering if you can pile it up for extra R value or there is a limit on vertical walls how much you can make "stick".


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## beenthere (Oct 11, 2008)

Its dries/cures fairly quickly. You layer it. A second coating will adhere to the first coating.


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## Olcrazy1 (May 28, 2013)

I went through all this not long ago and almost went the diy foam route. Read lots of stories where people were not getting the yield square footage being advertised plus cheapest I could find at the time was about $1.00 square board foot on the diy stuff. Found a local company who quoted a $1 sbf so I just went with him. Professional equipment and they did a great job. Paid for 2" thick but they sprayed 3"+ in the whole room. Guys explained how to get the best yield the foam has to be heated and pumped at correct pressure. Showed me all the equipment in the trailer and ran a long hose from tailer to basement. Think it had 4 lines inside the hose and was about 3" in diameter. 1 hose for part A of the foam, second for B, then one for air pressure and the last for heat to keep it at temp. Think he said 90 degrees but not sure. Long story short I never could have done the job they did with the diy cans and it cost me the same and j didn't have to do a thing. Check your local spray foam guys. If you can find $1 sbf I would jump on it. Just my opinion


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## Ocelaris (Oct 9, 2012)

Question, did they spray in the winter? I'm looking to either do it myself or have them do it, and I thought if you sprayed cold surfaces (i.e. sil plates) that it wouldn't stick or at least not expand. 

Can you have them spray upside down? We have some plywood under the heated electric floor in our two bathrooms that I'd like to insulate from the bottom, but not sure if it would stick or if it would fall down? 

We had an energy audit about a year ago, and some of the stuff they wanted to do was very expensive; but they did quote the spray foam quite low; so we had considered having them just do it. Sometimes we just like doing it ourselves for that reason, we know what we did and are sure of what we pay for. Most of the time it's cheaper, but I agree, in this case it doesn't seem like there is a huge price difference. Especially after the $100 for shipping for the canisters!


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## Olcrazy1 (May 28, 2013)

It was spring in Cleveland when I did mine. I wouldn't want to answer you questions and be wrong so I will leave them for someone who knows. I had them do from floor to ceiling including the rim joists. In the rims they sprayed even thicker basically filling the entire cavity. Very pleased with the results and can tell a huge difference between lag winter when it was in-insulated and this one.


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## jayb614 (May 6, 2015)

When applying spray foam, specifically closed cell, it is optimal to do it in more thin coats than in one thicker coat do to the way it cures, If you spray some for example and you let it cure, then you slice it open you will notice it appears porous inside and more smooth on the outside. This is key to getting maximum moisture barrier from it. Each layer will give another outter barrier. More layers in the same depth gives more protection then less thicker layers.


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