Quote:
Originally Posted by Daox
I just wanted to discuss this and get some info floating around here on it. It has been mentioned a number of times here that fiberglass looses its r-value in cold weather.
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About 15 years ago I built a test rig which was incredibly simple... I took a 5 gallon bucket, made a small pedestal upon which my test sample would be placed, and heated to boiling, an aluminum beer can of water.
I placed insulation in question below, and beside the sample.
The test was conducted in my living room, so the temp was always the same.
I would place the sample into the test rig, put a thermocouple in the water, place insulation over the sample, put on a lid with holes (there were also holes in the bottom of the bucket) and take data at regular intervals, for an hour.
I had no way to quantify the materials, but I could get a ranking of materials
when I plotted the heat loss data.
The ranking agreed with the study you cite.
Cellulose = best
Fiberglass = middle
Styrofoam peanuts = worst (recycling maniac = me)
However, when I mixed small-particle styrofoam chunks in with the peanuts to fill the voids, it ranked with cellulose. So yes, air migration was the villian.
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There's also an R-value creep regarding polyurethane foam, if compared to expanded poly-styrene. Funny, the study didn't mention that in the study. Possibly it's because they (Foam-Tech) sell the polyurethane foam.
The polyurethane foam has a higher initial R-value (and cost) but over time (15 years or so) it's R-value falls, because it takes up moisture, to about the R-value level of EPS (expanded poly-styrene).
So initially, polyurethane foam is the R-value winner, but over time, EPS becomes the 'R-value per dollar' winner.
Best Regards,
-AC_Hacker
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