Can you paint the insulation boards after installing them? This would be for an attic interior installation. Then could I skip the dry wall? How good would it look compared to drywall?
Can you paint Dow THERMAX WHITE FINISH INSULATION
insulationpainting
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It's common to do the reverse...clad the outside in foam insulation to prevent thermal bridging from that side.
Your idea is sound. I'd suggest using full panels and then tape them. That would add additional insulation to the entire wall and also act as a Vapor barrier for you.
Another technique is instead of using insulation, install 1x2" slats horizontally across the studs every 16" and install the sheetrock to that. The theory is the same in that the only bridging would then be and the small points where the two pieces of lumber meet.
Yes, Rigid foam (XPS and ISO) boards are frequently used in exterior applications, and can be a great option for improving efficiency. There are a couple of issues with your proposed approach, though:
- Vapor barrier location. The vapor barrier should be on the warm side (probably inside, unless you live in a very hot & humid climate). Ideally, this is immediately behind your interior drywall. You also do not usually need an extra vapor barrier layer adjacent to rigid foam sheets, they are typically highly resistant to moisture.
- Attachment. You cannot rely on glue to support foam and siding panels. These need to be mechanically fastened.
On a wood frame house, you'd want to use this order:
- interior drywall
- possibly a vapor barrier (e.g. poly sheeting), though the wisdom of this is debatable (see the comment from iLikeDirt below)
- wall studs (optionally with batt or cellulose insulation in between)
- exterior sheathing
- rigid foam
- wooden strapping for attaching siding, screwed to studs through foam. This provides support for the siding and also allows air circulation behind the siding, so any moisture that gets behind the siding can dry out.
- siding panels, nailed to strapping
Here's a visual from Fine Homebuilding, which has a couple of good articles on this:
Note that adding foam on the exterior of your house complicates some things. You will likely need to redo the trim on your windows and doors, which will become more in-set. These inset areas will need to be flashed properly or you will have leaks, which have more potential to do damage when you've got multi-layered, thick walls that could trap moisture. If done well, you can get very good insulation. But make sure to work with someone who knows what they're doing!
Best Answer
Thermax is rated for fire exposure and those particular boards are intended for interior finished space, so yes, you can paint the boards instead of covering them in drywall. However, I'm not sure the result will be very aesthetically pleasing or durable if this is going to be a finished residential space, which, based on your previous question, I'm guessing it is. But it should work.