Loose-Fill Insulation in a Temperate Climate
Is loose fill cellulose in the attic a bad idea in the PNW?
I’m in the Seattle area (Climate 4c; rainy much of the year). My general contractor’s insulation guys responded to my request for R49 blown-in cellulose in my attic, which is vented (via eave vents + ridge vents), saying cellulose is not used in the northwest only in dry climates. I’ve never heard this before — is it correct? They also quoted my bib & cellulose for my walls without trouble — but I guess those are less “exposed” to the elements.
Am I asking for the wrong kind of cellulose here and, if so, what should I actually be asking for?
They originally assumed I was asking for blown-in fiberglass, which gets my respiratory anxiety running loose… but does it have advantages over blown-in cellulose?
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Replies
finePNW,
That's a really odd thing for them to say. Every attic I've seen in houses built here in coastal BC in that last couple of decades has had cellulose in them - except for the odd DIY built ones. There simply aren't any problems associated with it.
That's great to hear. Thanks!
Oddly enough, I can't find any clear documentation from generally trusted sources (that I can share with them) talking about the pros (or even the cons) of using blown cellulose in attics in the PNW. Know of any? I'm currently hunting BC's illustrated guide for 4-coastal climate, which I think I saw once a while back. That must have some mention of cellulose.
Edit: found it, but no (PDF-searchable) mention of cellulose or loose-fill -- https://www.bchousing.org/publications/IG-Energy-Efficiency-Houses-Climate-Zone-4-LowerMainland.pdf
finePNW,
I don't think it has ever come up because it isn't something anyone has had a reason to turn their minds to. It's just a well working accepted practice.
The link you posted is a guide to the new code requirements in BC for energy efficiency. You will find better general advice in this one: https://www.crownpub.bc.ca/Product/Details/7630002069_S
I'm in Seattle and have blown cellulose in my attic. I've talked to at least 4 different contractors about blown cellulose and none of them suggested it was a bad idea in the attic. My impression is that blown cellulose is the *most common* attic insulation around here. It's especially common as a retrofit for old houses that are uninsulated.
That’s also my understanding. Weird. Was yours blown in dry or wet/dense packed?
Maybe they were saying folks don’t use it in walls here and I misunderstood them?
Blown in dry. My walls also had cellulose blown in via holes in the sheathing at some point >20 years ago. I think blown cellulose is/was an extremely common retrofit for old houses with uninsulated walls because you can get it in without totally deconstructing the wall
The company's policy apparently was to stop installing all cellulose in PNW homes ~ 20 years ago after people had trouble with cellulose gaining water (maybe weight and mold?). That's all they were able to tell me. Any chance you know the brand you used in your attic recently? I'm going to try to present them a spec sheet and ask for more detail and/or for them to reconsider. Really not stoked about the potential for blown-in fiberglass, but maybe that's a bit unscientific of me.
Looks like someone else already pointed you at greenfiber, which seems to be the brand everyone sells around here. And also suggested you look for a different insulation contractor, which was going to be suggestion also :-)
It is not possible to prove a negative ask him to provide positive evidence that would confirm his statement. Like a warning instruction from a cellulose manufacture.
Walta
Turns out it is a company policy for a large company ("Superior Insulation" which seems to be part of "TruTeam": https://www.truteam.com/branches/wa/puget-sound/547/).
The policy apparently was to stop installing all cellulose in PNW homes ~ 20 years ago after people had trouble with cellulose gaining water (maybe weight and mold?). That's all they were able to tell me. I am going to try to provide a specific type and brand for attic and, separately, walls, and ask if they can review spec sheets and reconsider. Got any type/brand recommendations?
To my ear it sounds like the policy of this one company is to install other products with a higher markups.
Walta
Probably a reasonable interpretation, and a good point.
I am going to attempt to provide a specific product and ask their comfort.
Does anyone have a specific product they would recommend for attic, separately, for walls (for application in new construction/open walls)? I assume some sort of loose dry fill for attic and dense wet fill for walls, but unsure. Brand names would be great, too, so I can share an example spec sheet.
Another anecdote that cellulose is commonly used in the PNW: I specify cellulose in walls and in attics all the time in the PNW and it's probably the one envelope thing I haven't ever had a contractor give me pushback about. I've had pushback about rainscreens, pushback about flashing details, pushback about continuous insulation. But my experience has been that everyone I've worked with has been happy to use cellulose.
If you want cellulose, it might make sense to ask your general contractor about the possibility of using a different insulation subcontractor, rather than trying to convince that sub to install cellulose. You're always going to get the best results when your desires line up with what the contractor or subcontractor has a lot of experience installing.
Yeah, that's a pretty good point re: contractor experience w/ cellulose. What product(s) do you specify for attic and walls? Loose fill for attic, and dense pack for walls? Any specific brands?
I specify loose fill for attics, dense pack (the kind where they staple up netting, then blow it in) for walls. I don't typically specify the brand of cellulose.
It looks like GreenFiber is the brand Home Depot sells, if you're just trying to find a common brand to look for cut sheets, installation instructions, etc.
much appreciated.
Martin Holladay has an article up on the GBA website right now about roof failures:
https://www.greenbuildingadvisor.com/article/low-slope-roof-assembly-failures
Quote from the article:
The failures that Dupuis has investigated—the failed roof assemblies were generally on large commercial buildings or multifamily residential buildings—have very shallow attics under a flat (or so-called “low-slope”) roof. Above the top-floor ceiling, the plans call for the installation of blown-in fiberglass insulation; above the insulation is a shallow air gap, and above the air gap is the roof sheathing.
Later in the article he mentions that repairing one of these roofs can cost half a million dollars.
I could see that if a company had provided the insulation for a roof like that, and got caught up in the ensuing litigation, they'd be inclined to get out of the blown insulation business forever.