the foam board Im using for insulation

[cutthroatxxx]

Hey fellas I posted awhile back about insulating my shop with foam board its 24x36 with a shed style/lean too type roof.Its framed &sheeted with osb than felt then tin what I'm trying to see is if I made a bad decision on the foam board.Its 1&1/2 in Styrofoam but not like the Dow sheets its like what a cup would be made of if you break it,it has the little balls that are compressed together its not like the expanded foam.I think you get what I'm saying.I'm almost done with doing the whole shop now&have enough leftover that I can double or triple it up.Think I may do double on the roof.Anyway was this a bad choice?The guy I got it from only charged me 2 dollars a sheet & gave me another 100 or so for free.
I hung it all with 1x2 & I'm hangin tongue and groove boards over everything because I can get enough to do it for around 300. so basically is there any kind of cons to this type of foam?

 

[Dick in Wisconsin]

What is the R-value/inch/dollar? How does that compare to the Dow sheets.

If it has an extremely low R-value, you might be better off taking the money in one dollar bills, crumpling them up, and using them instead.

 

[cutthroatxxx]

Wah wah wah...I have no idea the fella I bought em from builds pole barns&he has 1000s of em I have no idea who makes em&I thought they were the same as the Dow boards till I cut into one.If I need to Ill go buy some Dow boards&hang em over em.I did notice it already feels tons warmer in there its just not finished yet.

 

[Kevin C]

http://www.finehomebuilding.com/item/4822/which-rigid-insulation-should-i-choose

Good link .... Yours is about R4 per inch... Dow's is R5 per inch. ISO is around 6.5 per inch.

Not a huge R value but not a lot of thermal bridging.

 

[cutthroatxxx]

http://www.finehomebuilding.com/item/4822/which-rigid-insulation-should-i-choose

Good link .... Your is about R4 per inch... Dow's is R5 per inch. ISO is around 6.5 per inch.

Not a huge R value but not a lot of thermal bridging.

Thank you that was what I needed.

 

[Nowater]

White stryofoam cups are not waterproof, and I suggest that your insulation is not either. For that reason, a vapor barrier should be used on the warm side to prevent water vapor from condensing on your roof. Considering the money you saved on the foam, putting a vapor barrier is not such a bad tradeoff.

 

[cactiki]

Cups are not waterproof?

I wish I could find this stuff for $2 a sheet, I would make my garage into a giant Ice Chest like you are doing! You said you can feel a difference already, and if it is not enough, you can do another layer.....

 

[cutthroatxxx]

Lol yeah I though thru Styrofoam cups aren't waterproof was kinda funny too...guess that's why I can't keep my whiskey in em anyways yeah its a huge difference!It was cold outside today&I was in there with my big drum fan going.The fella says he has thousands of em.

 

[Thorold]

I'd have to say that at that cost it's amazing insulation - i'd take all i could and finish my attic.

I believe it's called compressed polystyrene.

 

[BigGMC]

"Expanded" polystyrene (EPS), the Dow blue board or Owens Corning pink board is "Extruded" polystyrene (XPS).
At that price, it's a fine insulation. For comparison, my local HD (new york) has the 4'x8' Dow boards, 2" thick, for $38 (if I remember right)

 

[bgarrett]

White stryofoam cups are not waterproof, and I suggest that your insulation is not either. For that reason, a vapor barrier should be used on the warm side to prevent water vapor from condensing on your roof. Considering the money you saved on the foam, putting a vapor barrier is not such a bad tradeoff.

What is the 'warm' side??? In the winter, its the inside, in the summer its the outside
Where should I put vapor barrier?

 

[mmhouse]

It is indeed 'expanded polystyrene.' It typically has an R-value of around 4 per inch. It is considered to be 'semi-permeable' to water vapor so should be used along with a vapor barrier which should go on the inside of the building.

 

[Full Throttle]

What is the 'warm' side??? In the winter, its the inside, in the summer its the outside
Where should I put vapor barrier?

To the interior side

 

[green.bubbly]

To the interior side

Unless you live in the south.

 

[mmhouse]

Unless you live in the south.

True, but the OP said "it already feels tons warmer in there" which indicates he is in the north.

 

[bgarrett]

Unless you live in the south.

Where does the vapor barrier go near the Arkansas/Missouri state line?
That aint the South nor is it the north

 

[NUTTSGT]

I put 1 1/2 of it on the inside back wall of my garage. While it may not be the best insulation out there, it's better than nothing, especially at that price.

I covered the same wall on the outside with 3/4", whick I bought at Menard's for $5/sheet I believe. If you have enough, I'd put a second layer up, why not ? I'd try to stagger the seams if you can.

BTW, I'm not sure what you cut it with but I use an old steak knife, maybe a small bit of wd-40 on it.

 

[mmhouse]

The best thing to cut it with is a hot knife tool like this...

http://tinyurl.com/9cte9by

 

[NUTTSGT]

The best thing to cut it with is a hot knife tool like this...

http://tinyurl.com/9cte9by

Then I'd have to buy another tool. too bad I'm done.

 

[trbomax]

HF has those hot knifes for around 13$. I used and am still useing,about 150 sheets of 1.5" and 2" in the shop so far. The hot knife smells really bad and the foam shrinks back about 1/4" from it so precision cuts are tough. I use a lowes break off knife with the wide 3/4" blade.Leave the blade all the way out,use a aluminum straight edge ,and as shallow of an angle as you can on the knife.

 

[NUTTSGT]

HF has those hot knifes for around 13$. I used and am still useing,about 150 sheets of 1.5" and 2" in the shop so far. The hot knife smells really bad and the foam shrinks back about 1/4" from it so precision cuts are tough. I use a lowes break off knife with the wide 3/4" blade.Leave the blade all the way out,use a aluminum straight edge ,and as shallow of an angle as you can on the knife.

Nice to know (knew about the fumes) I guess I'll stick to my steak knife.

 

[green.bubbly]

True, but the OP said "it already feels tons warmer in there" which indicates he is in the north.

Hey, we are going to have a low of 40 early next week down in south Louisiana.

 

[bigguns69]

This is what I did for insulating the walls of my 36'x50'x15' Menards kit building that I built 2 years ago. I used the 1 1/2" styro-foam in between the exterior girts, held them in place with nails that I pounded in partially and then bent over to capture the foam board. I then added the vapor barrier and stapled to the inside of the exterior girts and post. I then hung 6" thick non-faced bat insulation to the gap width of the poles. I then installed interior girt boards and sheeted it with OSB and then a lot of paint.
I cut the styro-foam with a hunting knife, scoring it about half way through the thickness and then snaping the sheet into pieces like you would drywall. My building is nice and tight, warm in the winters, cool in the summers and quiet from outside noises.
I put the foam board up to insulate the steel sheeting from the temperature difference between outside and inside. On pole buildings, the condensation collects on the inside surface area of the steel when the air inside is warm and moist next to a cool steel surface. Eliminate the direct contact surface area, eliminate the potential for moisture.

 

[NUTTSGT]

This is what I did for insulating the walls of my 36'x50'x15' Menards kit building that I built 2 years ago. I used the 1 1/2" styro-foam in between the exterior girts, held them in place with nails that I pounded in partially and then bent over to capture the foam board. I then added the vapor barrier and stapled to the inside of the exterior girts and post. I then hung 6" thick non-faced bat insulation to the gap width of the poles. I then installed interior girt boards and sheeted it with OSB and then a lot of paint.
I cut the styro-foam with a hunting knife, scoring it about half way through the thickness and then snaping the sheet into pieces like you would drywall. My building is nice and tight, warm in the winters, cool in the summers and quiet from outside noises.
I put the foam board up to insulate the steel sheeting from the temperature difference between outside and inside. On pole buildings, the condensation collects on the inside surface area of the steel when the air inside is warm and moist next to a cool steel surface. Eliminate the direct contact surface area, eliminate the potential for moisture.

You have a build thread on this place ?

 

[milner351]

I did something similar to bigguns69 but I skipped a few steps.

Given time and cost restrains, I put 2" foam "white board" over the girts (leaving a 1.5" air gap between exterior metal and foam) then used 3" barn metal screws to install interior steel right over the 2" board. I used expanding foam to seal any gaps if the boards didn't fit tight.

I only did this on the walls, since I also have a metal roof and open trusses - I had icynene foam sprayed on the underside of the roof 6" thick or so (left it un trimmed - looks like the surface of the moon)

I have a 185,000 clean burn waste oil furnace that will warm the place up just fine even with the horrible sliding barn doors that are nearly impossible to seal.

 

[trbomax]

Mine is like that too but much more extreem .I had a thread called "trbo's wall construction" a while back.