Replies

1. GBA Editor
   Martin Holladay | Mar 18, 2010 05:39am | #1

   Bruce,
   I haven't seen such charts, but I know that Joe Lstiburek's Building Science Corp. has spent tens of thousands of dollars building a test facility to measure insulation performance at different temperatures to create just the curves you are talking about.

   They have run into a variety of technical problems, however, during the set-up process. Eventually they hope to publish their findings.

2. 
   Riversong | Mar 18, 2010 09:36am | #2

   Bruce,

   Fiberglass is almost unique among insulation materials in it's performance at different temperature differentials because it does little to restrict internal convection. The thermal conductivity of an insulating material changes little with temperature changes, but the increased delta-T causes a convective drive (stack effect) which will move air through air-permeable materials like spun glass fiber.

   For this reason, fiberglass performs poorly both at low ambient temperatures and at high ambient temperatures, in other words when thermal performance is most needed. This is particularly true of loose-fill attic insulation and less so with the newer, more dense batts and blown fiberglass.

3. 
   jklingel | Mar 19, 2010 12:51am | #3

   Bruce: I have seen, but can not find, said charts for cellulose and fiberglass batts, and the data was right on what Robert said. If I can find the *&^% file, I'll post it. Oak Ridge Labs, or someone.... did it. john

4. 
   Riversong | Mar 19, 2010 09:49am | #4

   Here's a Dupont document with some interesting temperature vs R-value curves for polyurethane foam, which is dependent on the boiling point of the refrigerant used as the blowing agent.

   http://www2.dupont.com/Formacel/en_US/assets/downloads/h54876.pdf