Insulation Question

[wlivesey]

Some parts of my build will require about 2 1/4 inches of insulation. I was thinking about stacking a few layers of foam board to reach this thickness. My question is: Do I need to remove the plastic skin from the inner layers of foam? It seems to me that I may only want to keep the plastic vapor barrier on the outside. Is there a better vapor barrier to use? Maybe tyvek or similar???

FYI... I plan on using 1/4 ply on top of the foam with a .040 aluminum skin.

Thanks in advance!

[Rock]

The closed cell insulation is already vapor proof, water proof, insect proof....

I think the film is used in manufacture and probably also to protect it during handling. Leave it on.

Eric

[wlivesey]

I heard somewhere that the plastic skin IS the vapor barrior...

[bobhenry]

The closed cell insulation is already vapor proof, water proof, insect proof....

I think the film is used in manufacture and probably also to protect it during handling. Leave it on.

Eric

Rock is dead on The somewhat streatchy film is simply a reinforcement for the closed cell foam sheet. It acts much like the chords of a truss as the sheet trys to bend the film stretches and adds resistance to the bending. Without is it would be all but impossible to apply 4x8 sheets on a home on a breezy day. Stack in in the cavaties and a good trick is to tape it where it flushes up with your wall's wooden members. This will help to seal out the drafts on a windy day.

Another trick I used with multiple layers is to "nail" the sheets together.
I skewered the layers together with a tooth pick here and there to keep them from dropping in behind each other.

[wlivesey]

Thanks for the good ideas...

I know I'm going to have some gaps (in the insulation) here and there, where wiring and/or other obstacles get in the way. I was thinking about filling in the gaps with Great Stuff. Are there any issues with that approach?

[starleen2]

And seal the Gaps -if there are any - with foil tape tape. You can achieve a tight fit with the foam in the cavity, but I like to seal it all up with the foil tape just be sure nothing gets in between. You can see it on the back wall (had to go way back to find a pict)

[starleen2]

Thanks for the good ideas...

I know I'm going to have some gaps (in the insulation) here and there, where wiring and/or other obstacles get in the way. I was thinking about filling in the gaps with Great Stuff. Are there any issues with that approach?

BE sure to wear some disposable gloves - If you get that stuff on you, then it's really hard to get off!. Used it on the Lady Bug WW and it does what it advertised. However, I sprayed it the gaps one day and waited till the next to trim off the surplus with a hacksaw blade. Went through it just like cutting foam - then covered over with foil tape

[wlivesey]

And seal the Gaps -if there are any - with foil tape tape. You can achieve a tight fit with the foam in the cavity, but I like to seal it all up with the foil tape just be sure nothing gets in between. You can see it on the back wall (had to go way back to find a pict)

You didn't put the tape on the framing did you? I can't tell from the picture... You would want that surface for glue.

[starleen2]

And seal the Gaps -if there are any - with foil tape tape. You can achieve a tight fit with the foam in the cavity, but I like to seal it all up with the foil tape just be sure nothing gets in between. You can see it on the back wall (had to go way back to find a pict)

You didn't put the tape on the framing did you? I can't tell from the picture... You would want that surface for glue.

It's hard to see in the photo, but you can see some wood peaking trough. It's about 1/4 inch on the framing member. You are correct leave some wood exposed for adhesive. This was an interior piece. I insulated in reverse of yours. The exterior was already applied.

[wlivesey]

I decided to live up to my tag line and went with spray foam insulation. Take a look at my build thread for photos.

[starleen2]

YEAH - buddy - That things gonna hold together no matter what comes it's way!

[caseydog]

I decided to live up to my tag line and went with spray foam insulation. Take a look at my build thread for photos.

I have to crack the windows when I camp in December. And, in July, my TD air conditioner barely runs.

Basically, where we live, insulation is not a critical issue.

CD

[wlivesey]

I decided to live up to my tag line and went with spray foam insulation. Take a look at my build thread for photos.

I have to crack the windows when I camp in December. And, in July, my TD air conditioner barely runs.

Basically, where we live, insulation is not a critical issue.

CD

It sounds nice there, where you live. Where I live, in Texas, it frequently surpasses 100 degrees in July and temperatures below freezing in December are not uncommon. I couldn't imagine going without some form of insulation here.

[starleen2]

I decided to live up to my tag line and went with spray foam insulation. Take a look at my build thread for photos.

I have to crack the windows when I camp in December. And, in July, my TD air conditioner barely runs.

Basically, where we live, insulation is not a critical issue.

CD

It sounds nice there, where you live. Where I live, in Texas, it frequently surpasses 100 degrees in July and temperatures below freezing in December are not uncommon. I couldn't imagine going without some form of insulation here.

Yep - there is a Huge temperature difference between north and south Dallas!