[Greenbuilding] Foam vs. wet spray cellulose vs. "flash & batt"

[Mark Marcoplos]

Most bang-for-the-buck is damp-spray insulation. Costs about $100 more per 
1000 sf  & will pay for itself in a year or two. Plus it uses recycled 
newsprint (10% of manufacturing energy required vs. fiberglass) treated with 
a borate solution as a flame retardant which doubles as a benign pesticide. 
Plus, instead of having to sell the family jewels to afford the foam, you 
may find haikus in the bits newsprint that are left behind.


----- Original Message ----- 
From: "Doug Horgan" <Doug at bowa.com>
To: <greenbuilding at listserv.repp.org>
Sent: Tuesday, May 20, 2008 11:09 PM
Subject: [Greenbuilding] Foam vs. wet spray cellulose vs. "flash & batt"


> Okay, so we're all looking into better insulation. And going energy star
> with our new houses.
> There seem to be two kinds of insulators around here, the all spray foam
> guys, and the regular guys who now dabble in spray foam. (Around here
> being Washington DC, climate zone 4, 4000 HDD & 1200 CDD).
> The spray foam guys say if you use all foam you will save so much money
> your electric meter will run backwards and automatically fill up your
> bank account. (I think that's what he said, it was a lot like that
> anyway...). Seriously, 500-60% savings vs. "normal". This for R15 walls
> & R25 attics.
> The other guys say to "flash and batt": use 1" foam at the most, then
> batts or cellulose. They claim the foam gives you all the air sealing,
> and you don't need to spend money on more foam after that. It is cheaper
> by a bunch, like 20% less than all foam.
> And, we have a gentleman working for us who's from Michigan and says
> they only ever used wet-spray cellulose up there and he isn't sure why
> we'd use foam at all.
> So:
> 1. Does 3-8" foam really do much more for you than other insulation?
> 2. Any thoughts on flash & batt? Specifically, how does it do on air
> sealing? Anyone out there who has done blower door tests on houses
> insulated that way?
> 3. Can wet spray get the job done? Again, anyone know what to expect
> from the blower door when you do good air sealing and wet spray?
> 4. For that matter, can you get a good blower door score using batts?
> Around here we never use a poly interior vapor barrier/air barrier,
> because of our high cooling load, but I have been reading up on sealing
> rim joists, bottom plates, using a bead of glue around the entire
> perimeter of the drywall, etc. etc.--does this stuff ever get you to
> excellent, or are batts really hopeless?
> 5. okay, one last thing. To me adding 1" closed cell foam to the inside
> face of the OSB sheathing does more good than harm, because it raises
> the temperature of that first semiimpermeable surface. That is, the
> inside face of the foam is much warmer than the inside face of the OSB
> without the foam, which should reduce the condensation potential in the
> cavity in winter. Therefore adding the foam should make the assembly
> perform better. Am I missing some important factor though? Should I be
> leery of 1" of closed cell foam on the inside of the OSB?
> Just asking for the moon,
> Thanks,
>
> Doug
> Doug Horgan, CGP
>
> BOWA Builders, Inc.
>  Celebrating 20 years of building relationships and award-winning
> projects.
>
>
>
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