Xps foam

[mwildt]

Just installed a new insulated attic access/ladder. Next I want to beef up the existing attic 'dome' with additional layers of xps foam.

It is the kind that is like 1.5" thick with foil cover. Any recommendations on glue when sandwiching some layers onto the existing box ? So basically foil to foil.

It is some places recommended to use construction adhesive, but I'm not familiar with those products enough to know what would be best.

 

[Peter_C]

Your post is not clear to me what your trying to do ???

As a rule of thumb, rigid foam insulation can be adhered with any construction adhesive that is low VOC/low solvent so as not to dissolve the foam. Most of these will say they are suitable for use with polystyrene, polyethylene, or rigid foam board, and include Liquid Nails Heavy Duty construction Adhesive (LN-903), Loctite PL375 Heavy Duty, and OSI F-38 Drywall Adhesive. Do NOT use polyurethane adhesives as these are solvent based and will eat the foam.

That being said, the RMax type product is foil faced on both sides protecting the foam from the adhesive, so most any adhesive will be fine. The before mentioned LN-903 is a good all-around choice.

http://www.homedepot.com/p/Loctite-PL300-10-fl-oz-Foamboard-VOC-Adhesive-1421941/202020476

 

[mwildt]

Thanks for the pointers. I'll see what the home center have of those.

The existing foam box will get an additional layer on all sides as to increase the r value. Both box and the new layer is xps foam with foil cover so gluing the layers together is foil to foil. I'll caulk or foam the seams and use foil tape as necessary. May install a second set of gaskets on the bottom as well.

 

[Cheese]

I've used PL 400 and also PL Premium without any issues.

 

[mwildt]

Thanks all.

 

[tjbnwi]

A second on the PL-300.

R-Max is a very good xps board. I use the Thermasheath-3 a lot.

Tom

 

[Brice Burrell]

I wouldn't bother buying construction adhesive unless you need it for something else.  You'll be able to use any latex or silicone caulk you have laying around.