My uncle is so cool.

[electricland]

I had a moment of idle curiosity about our spray foam insulation yesterday and emailed him to ask about it. This is what I got back:

Robin, here is what I prepared for Martin Elksnitis. I didn't send it in the end, because the manufacturer's technical expert told me that it wouldn't be likely to do any good: a number of building inspectors share Martin's scepticism, and have the authority to insist on an additional vapour barrier.

Medium density polyurethane foam -- OMHA Approval #94-09-09:
Reference: http://irc.nrc-cnrc.gc.ca/ccmc/registry/07/216/12380_e.pdf.

When we were discussing heat insulation, I think I must have given you the impression we were intending to use a low density open-celled foam, like Icynene. As you pointed out, Icynene has a lower r-value than fibreglass and very little resistance to water vapour. If so, I apologise for the confusion: we are using Polar Foam 7300, a closed-cell, medium density sprayed polyurethane foam (SPF) which is a far better insulator and vapour retardant. We are applying it directly to our walls at a thickness of 2", which gives an aged total R value of 12. We are applying 4" to the roofs and under the floor of the back room on the first floor, which is over an unheated crawl space; the aged total R value is estimated to be at least 24.

The CCMC reference advises that Polar Foam 7300 can be an effective vapour retardant when sprayed directly onto the substrate (i.e., not just poured into a cavity wall) at a thickness of at least 1". An NRC report recommends 40mm (1.6"), still below the 2" we are applying. On a masonry substrate, the permeance of SPF is 29.5 at 2", well below the maximum of 45 required by the Ontario Building Code. The permeance is higher when applied to a wood substrate: -- where we have 2" applied to wood in the third floor side walls, the permeance might be as high as 52 . However, the thickness in the roof and under the back room on the first floor is 4", for a permeance of about 30.

Martin told me to change one small detail in the plumbing (a vent, of course!); otherwise it passed. He also will not object to the sonopan. He also wants the foam insulation cut back from the party wall and replaced with non-flammable safe-and-sound -- your mother slaved away at that this afternoon. He also wants a mechanical permit, which means you or Jen will have to come and visit City Hall with me...?

Cheers,
John

ARGH MECHANICAL PERMIT! DAMMIT DAMMIT DAMMIT! Trip to City Hall in my future, I see...

But the sonopan and the plumbing both passed! This is good!

Comments

[electricland.livejournal.com]

It is kind of cool, actually, although it took FOREVER.

[nellisir.livejournal.com]

Are we talking about spray foam or renovating? Or something else altogether? It's been one of those mornings. ;) Happy American Thanksgiving, btw.

[electricland.livejournal.com]

oh dear, unclear antecedents. I was talking about the spray foam, the renovating being not yet safely in the past tense. Also, "cool" is the wrong adjective now, as it is significantly warmer. Although during the blazing hot days of summer we did notice the insulation made a big difference. So. Um. Yeah, one of THOSE mornings. Happy Thanksgiving to you too!