Technicalities of code-compliance for Spray Applied Polyurethane Foam Insulations
Rebroadcast of last years' post on the technicalities of applying spray-foam in California
Thicknesses of foams are limited in ICC evaluations. Back in my freewheelin' days of classroom hand waving, me and my colleagues used to dream of filling 2x12 cavities full of petrochemical plastic foam insulation and watching for non-convexiities in utility functions for insulation, otherwise known as "tunneling through the cost barrier". Other people call it "R-wars," but for the most part, those are a figment of our spreadsheets and our imaginations-- at least when it comes to spray applied foams as the sole insulator: Why? (you might ask)
Well then... It turns out that those aren't really possible in reality, at least not in a while that's been tested and certified by certification agencies.
For any foam plastic (spray foam) application submittal to a code-enforcement agency, it'll be good, if not essential to have some sort of testing report on specific assemblies that have been tested and approved:
here's an example ICC Legacy Report: www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1826.pdf Energy Modeling Ramifications:As a Title-24 modeller, my hands are tied when it comes to representing the superior performance of foam plastic insulation, since the Joint Appendices (which is the Bible of Lookup Tables that I have to refer to for my R-value numbers) only gives a generic "Foam Plastic" R-value based on thickness. This R-value reflects the most poorly performing foam plastic product that is registered with the state. That's going to be really different than the ecstatic claims that you'll see on technical data sheets from specific insulation manufacturers.
Workability of foam plastics:
In terms of labor costs and such, foam plastics will take more time than the average crappy batt job, because you've got to spray it on (which takes a bit of time) and then come back a couple of days later and scrape off any overspray. For the open-cell foam, it's fairly easy to scrape off, but for the closed-cell, it's a pain in the butt-- more like stone sculpture and less like . Some foam plastics apply smoother than others, and so installers have this experience (or they should)-- in either case, it's usually preferable, if not essential to have at least 1" or 1-1/2" of "Slop", or extra space in the cavity for the insulation to expand into so that the installers have some fudge room and not have to shave off a whole bunch so the salivating sheet-rockers can get on with gyping houses and general contractors ;)
Here's a youtube video that shows what I'm kinda referring to here: http://www.youtube.com/watch?v=-o6M4a-Fhqg&feature=related
Oh yeah-- unventilated attic assemblies
These are not formally allowed in California code. Any unventilated attic must be specifically permitted by the Authority Having Jurisdiction. Talk to the code enforcer people. They can be nice sometimes.
One of these days, maybe I'll post the code reference up here for y'all to look at.