How To Choose And Use Insulation - This Old House

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vkatgol: can you use both open and closed cell in the same area ?

Rick Evans: It is a bit troubling that the environmental impact of each of these insulation options weren't discussed. For those keeping track at home: Closed cell spray foam contains a blowing agent that destroys the ozone layer. It is an ideal insulation for retro-fit jobs- especially air sealing an old attic before additional fluffy insulation is added. Or, sealing an old cellar or crawlspace to control vapor/air. Please don't insulate the entire house with it though, even if you can afford it.

Also, in a 2x4 (which is actually 3.4") wall- they can only fill the cavity up 2.5" - 3". They have to leave an air space because closed cell foam cannot be trimmed back like open cell. This lowers the effective r-value of the wall. Ultimately, you are paying a lot more for an environmentally damaging product that will have a net r value that is about the same as a wall with high density FG batts or Roxul.

Some spray foam companies have sought to lower high global warming potential of the foam (honeywell). Its still way too high for a full house application but this is a wonderful improvement in the product nonetheless.


Haydon Peterson: I have a deck with a steal roof I want to turn it into a four season room but I have condensation from the steal roof would blow insulation fix my problem?

the dyslexic: We can go from -40F (-40C) in the winter to 104F (40C) in the summer.  Would you consider that to be like New England when it comes to vapor barrier/vapor retarder?

Jake Guerra: RetroFoam is way better then any of these so called systems.

Kevin Shayne: Foam is seriously dangerous chemicals. What happens when the house burns! Toxic toxic toxic. In addition, MANY people are getting sick from these foam spray applications. Want take a risk on losing your health and your home? Then try spray foam.

Mario C: I live in Southern Ohio, we get both hot summers and cold winters here in the midwest. My home was built in the early 1950's and has very scattered fiberglass insulation on the attic floor. If I wanted to turn the attic into a usable space during the summer and winter, would I have to insulate interior of the roof instead? Currently it is just framing, nothing but wood. Also- would this mean leaving what is on the floor? replacing it? or adding to it?

All recommendations welcome!

Ionut Ghira: I love how people completely disregard the health effects of these insulation materials. All of these are not good for you, and will create a potentially dangerous living condition. The only one that I have found to be safe is AirKrete, if anyone cares a little about their health.

Angelum Band: I don't see any questions being answered here. I guess we are on our own.

Amon Mwaijengo: How do I get these fire foams. I would like to become your distributor here in Dar es Salaam, Tanzania. Contact me via

craigsclocks: We have a attic with no insulation at all. . We want to go with the spay foam but what kind do we use and what company to trust? HELP This old house is more then welcome to my home.

Kashkaani Aspen: Help plz I am wanting to buy a mobile home and was thinking to use foam insulation found at Home depot but watching all the videos of insulation gone wrong smelling like fish or chemicals makes me Leary of DYI but I cant afford to hire someone. Input plz

Susie Barnes: At what point does the r value begin to only marginally improve insulation? In hopes to be clearer, the cellulose vs the closed foam. What would one expect to save?

Jonathan Gwynne: For simple stud/joist bays, I prefer rock-wool. Better R-value than fiberglass, waterproof, fireproof and better sound deadening.

Reuben Anderson: Thank you for the information and video. I also have a plaster condominium in Virginia and have been wondering what to do about the walls. After further review it looks like cellulose is also better for it's fire retardant properties and insecticide(boron). My idea now is to use cellulose then probable hire out the plaster work.

Mickey Cook: I watch this show on You Tube and the the TV....... it's just too bad we don't have these type of craftsmen in the Houston area...... where things are very often built the "Houston way".......... aka, build it so it "lasts" a year, after which, the warranty is up and it is the homeowners problem. See these poor workmanship issues all over town. Especially on the west and northwest side. Pretty sad.

the dyslexic: Doesn't shaving off the top "skin" of the foam diminish the vapour barrier effectiveness...or can you combat that by spraying in two or three goes?

alwaysrockn2009: Great video!!!

Livin In A Box: At 2:40 the guy talks about a vapour retarder, would this be something to go on both sides if you get hot and cold weather ? I'm wondering if it would need to go next to the exterior wall and on the other side next to the interior wall.

spacecadet28: So why is fiberglass most commonly used?
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