Thanks
just jim

Note: fiberglass as an
Note: fiberglass as an insulation technology is well over 100 years old and fiberglass Batt hasn’t changed except for the elimination of VOC causing additives, ex. formaldehyde. It’s still very much the same product. Alison (Energy Vanguard) has provided me with updates regarding the changes with their blow in product.

The only recent studies coming out are mostly directly from the manufacturers. My concern is that there are no longetivify studies being performed by third parties, or being followed up on. If my data is so outdated, can you please provide me with updates since no one else can?

Additionally, I recently found out that the OSHA toxicology definition which encompasses fiberglass was changed in the last two decades to not include the Insulating fiberglass fibers… hmm

Note that all of the
Note that all of the references Jose listed are 18+ years old.

I’d like to see third party
I’d like to see third party testing on the performance of these materials. Anyone that can find any sources — please let me know.

Have you all seen these? “Fiberglass BattsLabeled vs. Installed Performance”
https://www.demilec.ca/documents/Tech-Library/Building-Science/Actual-performance-of-fiberglass.pdf
https://web.ornl.gov/sci/buildings/conf-archive/1998%20B7%20papers/032_Christian.pdf

These papers contradict the performance metrics suggested by the fiberglass batt product manufacturers.

However, if I might make an observation or two, don’t you find it interesting that they only change the make up of their products when other people point out their faults. Are we really to believe they were unaware of these inadequacies! Now we are supposed to believe everything is OK and their products are up to specifications and will perform properly? Aren’t many of these manufacturers the same ones that told us for over 100 years that asbestos was safe and we had nothing to worry about! I can assure you (based on my own personal experiences) any testing that they provide should be thoroughly scrutinized, even down to how the test chamber was prepared. In closing let me say this, I find it appalling that they would have their attorney send you a letter reprimanding you for anything considering their past history!

I have wondered about why fiberglass batt insulation seems to collapse over time. When you go in an old attic like the one I have pictured, the insulation seems to have settled to a mere hint of what it might have originally been. Years ago I was told that the insulation is held together by an adhesive binder of sorts and as moisture moves through the insulation via the convective flows the moisture breaks down the binder and the fiberglass fibers gradually settle. This is a wonderful way to further emphasize how important the air sealing is.

I did ask someone in authority at OC a number of years ago and he said that was not the case, but it would be an interesting thing to be studying as well. Time impact as well as temperature. Do you know if there is any truth in the binder story?

I have a hunch that the convection issue doesn’t apply, since relatively cooler air in immediate proximity to the topside of the ceiling beneath the insulation is denser, so should remain in position.

However, I wonder about radiant effects. Asphalt shingles and the sheathing immediately under them routinely exceed 150*F, especially with dark colored shingles. What happens to the heat that radiates downward onto the top of the fiberglass?

Oh and the building industry puts them squarely on the bottom of the pay scale, meaning most look like they’ve lived a hard life to begin with and haven’t always made the best decisions, but you’re hoping as a homeowner that today they will.

The issue with fiberglass is that it remains exactly as it’s installed, so when speed is the goal, installers tend to turn the machine on the highest blow rate and stand back and load the attic like a ski area covers runs. Rather than crawling back into the tight perimeter areas with the hose and getting the end out into each cavity and allowing the product to bubble back at them, installers tend to make it snow and ensure the area around the inspection hatch is above the rulers.

Cellulose, on the other hand, still requires good installers, but it’s density at 3x greater than fiberglass, makes it less prone to installer defects by settling to its rated r-value over time. So insulating with cellulose is inherently less risky than fiberglass, and capping a fiberglass attic (that has already been fully air sealed) with cellulose is a good practice.

I’be also found that ducts with radiant barrier jackets perform much better in summer time when they are surrounded by blown fiberglass over cellulose, and I believe the reason is the incredible r-values of radiant barriers (changes with each orientation) when there is an adjacent air space (created by pockets within the low mass fiberglass that are larger than cellulose). Deeply buried ducts in FG tested near R-30 whereas cellulose ones were about 10 less from memory.

Lots to think about with real people installing products. Thanks for another good article and reopening “the great debate”. 🙂

I a wondering not about the air falling in from the top side of the insulation, but air from the poorly installed or bypassed soffit baffle. Do you know of any research that shows a de-rate in the R-value of attic insulation when soffit air infiltrates it down low on the drywall side of the insulation?

I have always thought that the depth of the material in the attic compensates for our inability to practically enclose the top side of vented attic insulation. The depth helps ensure that attic ventilation air does not fall through all the way to the drywall of the ceiling below. But air can still migrate through fibrous air permeable insulation. So the baffle at the soffit becomes more important to ensure that air is not infiltrating into the attic insulation down low at the drywall level. What do you think of this? does it make sense or am I barking up the wrong tree? Thanks