A representative of the industry says I shouldn't be picking on fiber glass. He's right.
This TreeHugger used to complain a lot about fiber glass insulation, but much has changed over the last few years. I recently wrote Over half the new homes in the USA are insulated with fiberglass batts where I ate some of my earlier words and noted:
My main complaint about it was that "nobody understands how to install it properly to minimize air leakage or wants to spend the time and money doing it."
When properly and carefully installed, with a properly and carefully installed air and vapor management system on the inside and out, fiberglass isn’t so bad. They have mostly eliminated formaldehyde binders and it scores pretty high for health. It’s not even that bad for embodied carbon.
I then received a long and thoughtful response from Angus E. Crane of the North American Insulation Manufacturers Association (“NAIMA”) who had issues with the post. He starts by noting that, "in order to achieve intended thermal performance, all forms of insulation must be installed properly. That is why NAIMA strongly supports energy codes and standards that either promote or require Grade I installation for all batts."
Totally agree – if installations were all Grade I there would be no issue here. But Mr. Crane is absolutely correct in noting that poor installations happen with every kind of insulation, not just fiber glass. My emphasis on his most important point:
To single out fiber glass batts is unfair and inaccurate. If there is a problem with batts, there is a problem with all batts, including cotton, plastic, denim, rock wool, slag wool, or any other types of batt. Moreover, the rate of improperly installed fiber glass batts must also be weighed in balance with the fact that fiber glass is the most widely used insulation product in North America. Put simply, more fiber glass batts are installed so more are likely to be improperly installed.
Many insulation products when incorrectly installed not only fail to deliver their optimum thermal performance but may cause serious damage or destruction to the building, too.
Indeed, we have complained often about spray foam because of installation problems, health issues, embodied carbon and fire hazards during and after installation. Crane writes:
Significant fire and explosion hazards exist during installation of spray foam products. OSHA has identified several fatalities and incidents due to severe asthmatic attacks and fire/explosions associated with the use of isocyanate-containing materials (which is one of the chemical hazards in spray foam products).
Mr. Crane notes that the cellulose beloved of green builders can also be problematic:
Most other blown-in products can also be under-sprayed, fluffed, or subject to settling. For example, cellulose insulation settles over time. Third party documentation estimates that settling of cellulose insulation shows an average settling value of 19 percent....The installer must consider installed thickness and settled thickness, which means additional product must be added to compensate for that settling factor.
He also reminds us that cellulose can be a fire hazard if improperly installed around pot lights and furnace flues, a worry we share. Mr. Crane concludes his letter:
NAIMA hopes that in future columns you can join with NAIMA and many other insulation producers in advocating proper installation for all insulation products. To single out fiber glass actually does a great disservice to your readers because it suggests that it is somehow a unique issue to fiber glass when, in reality, it is an issue for the entire insulation industry.
He's absolutely right. I have seen terrible foam installations and beautiful fiber glass installations, like this blown installation being done by Hammer and Hand in Seattle a few years ago. Ten years ago I thought fiber glass insulation was fundamentally problematic, but they have fixed that by switching from formaldehyde to acrylic binders, while at the same time we have learned about the problems with other insulations. Fiber glass is the least expensive insulation, so it makes sense that it's the one chosen most often when builders want to build quick and cheap. But it is a fine product when used properly.
I will be taking Mr. Crane's advice and will be an equal opportunity whiner about installation quality, whatever the insulation is.