Friday, May 7, 2010

Closed Cell foam and Refrigerant calculator

Hi all,
Here's a revisitation of an old topic:  what is the greenhouse gas balance for a closed cell foam as insulation in a building assembly.  The issue is that a lot of closed cell foam uses a blowing agent that has a substantial global warming potential.  In the application of the foam, does one end up releasing more GHG's than one would save in the energy efficiency of the assembly?

HFC-245fa is generally the refrigerant in use in many of my projects, and the global warming potential is generally agreed to be about ~1000 times that of CO2.

I made up a spreadsheet full of all sorts of assumptions and calculations.  They're all mutable.
Based on the current numbers, even thin layers of foam have a substantial greenhouse gas impact-- on the order of a 10-20 year GHG payback for a standard 4" assembly.
Given this result-- another reason to approach closed cell foams with caution.

Updated Link!!
(update to updated link-- for some reason Google Docs is pwnd-ing me like the n00b that I once was.  The link keeps on breaking-- at some point very soon I'll fix that and figure out what's up)

There are probably errors in my calculator that I haven't spotted yet.  I hope you'll help me weed those out, which is why I'm still wary of any outright ban on closed cell foam in my projects.  It's good stuff when applied well and correctly.  But there are many alternative assemblies which could perform just as well...