Hi

I've got a thumbnail image of this graph (ridiculously low-res image attached). It shows R value vs. ambient temperature and plots cellulose and fiberglass insulation. The R value fall-off for fiberglass is dramatic!

I would really like to obtain this graph and related documentation for my project file. Searching the ORNL website didn't help me find it. Can anyone provide a link to the graph?

Thanks

John

John,

http://www.monolithic.com/s...ues/photos

This may help.   From above link:

Figure 2.4 — There is a problem with loose-fill fiberglass attic insulation in cold climates. It appears that , as attic temperature drops below a certain point, air begins to circulate into and within the insulation, forming “convective loops” that increase heat loss and decrease the effective R-value. At very cold temperatures (-20F), the R-value may decrease by up to 50%.

In full-scale attic tests at Oak Ridge National Laboratory, the R-value of 6 inches of cubed loose-fill attic insulation progressively fell as the attic air temperature dropped. At -18F, the R-value measured only r=9. The problem seems to occur with any low-densitiy, loose-fill fibrous insulation. (J.D. Ned Nisson, “Attic Insulation Problems in Cold Climates,” Energy Design Update, March 1992, 42-43)

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I did look for J. D. Nisson report (several spellings of his name are out there but was not able to find it). 

Regards.

the problem with that report is the advancements in blown insulations since 1992. With more modern fiberglass loose fill and cellulose, convenction loops are greatly reduced compared to what they are claiming 20 years ago.

Not really new news. Having started my career in the insulation business the first time we blew blowing wool in a large commercial job I knew it was junk. I'd still give a caution about the new [30 years old] permium fiberglass products. They can still be over fluffed and unlike cellulose they will take a life time to reach their settled density. The cubed wool that is being sold at the homarama should be outlawed, it's garbage.

Your right. Not really new news is right but I wasn't able to find the report. I would like to find this research because it seems to me that R-values for these products would also go down with increasing temperature as well since the test is done at about 70 degrees in a vacuum and is conduction only. Any temperature change at all up or down will cause convective loops. Regards.

True but I suspect the "cold attic" convention is worse since hot air (in the insulation) rises.

Walls might be the same regardless of heating or cooling season though.

John

(The University of Colorado "House A vs. House B" study sure makes cellulose look better than its raw R value.)

Well that can't happen. You have alink to that study?

Link to copy of U. of Colorado study:

http://www.builditsolar.com/Projects/Conservation/Insulation/Colorado.pdf

Thanks Lee.