We used to say this stuff should be banned because it was always installed badly. Has anything changed?
Why is this installer wearing a mask and a TYVEK suit? He’s rolling out fiberglass batts, and the stuff is really itchy. You don’t want to breathe in the fibers because they are a lung irritant. He is rolling it out carefully, but it’s often installed really badly, to the point that some building experts have suggested it be outlawed.
The performance vs. value tradeoff in the decision to specify insulation materials is often discussed among home builders. Some would use a full-cavity fill of foam insulation if the cost were lower. Some believe fiberglass is the best bang-for-the-buck, but if they’re looking for higher energy performance, they will put their money into other areas of their homes – like more energy efficient windows and HVAC systems.
So builders will happily keep building crappy walls that the wind can blow through because people can’t see it. They would rather sell visible performance, like windows and mechanical systems, because they can get real money for that.
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 – not nearly as good as cellulose but comparable with rock or mineral wool. (Cellulose, for some reason, has “seen a substantial decline in market share in new homes over the past few years.”)
The big problem with it is that nobody understands how to install it properly to minimize air leakage or wants to spend the time and money doing it. One reader at Green building Advisor “talked to many builders, most of whom are offering a 'standard' insulation package consisting of fiberglass batts in the wall and no separate air-control layer other than drywall or plugging holes discovered in blower-door testing.”
So it is pretty likely that half the new homes in the USA have the wind blowing through their walls, barely passing a 3 ACH blower test.
Bronwyn Barry of the North American Passive House Network recently tweeted the question, “When your house is on fire, would you use a bucket of water or a fire hose?” Surely we are past the point where this kind of approach to building is good enough.