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Here in Pacific Northwest, virtually everyone uses green Douglas Fir for framing. By green is meant: if you rip this stuff it will cover your goggles w/ spray.
I would like to use dense pack cellulose, but, as I understand it absorbs moisture, what will happen in the roof cavities with wet 2×12’s, cels sandwiched between them, sheathing and drywall?
Would fiberglass be a better choice, because of this? Or the extra cost of engineered joists? But then there’s the same possible problem with 2×6 walls. Or am I worrying too much?
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jim.. i know your framing is wet.. but it ain't that wet.. the cellulose will be ok.. especially if you use a detail that will allow it to release the moisture when the conditions change..
it will asorb, and hold the moisture ..and release it..UNLESS you exceed it's saturation point
.in other words, unless you have a leak.. you will not exceed it's saturation point..
fiberglass, on the other hand, cannot absorb moisture so the moisture condenses.. drips down to a horizontal surface and starts rot.. this does not make it superior.. it makes it inferior.. it's saturation point is close to zero.. so it will make your wet framing problem worse..
b but hey, whadda i no ?
*Jim,If the moisture content of the framing is low enough that the framing would not rot, then Cellulose will only help. Moisture moves from wet to dry. That is, it'll wick out of the wet wood and diffuse into the cellulose, leaving the framing a lot drier and the gereater volume of cellulose a little wetter, but not nearly as wet as the framing was to start with. As mike says, build the wall in such a way as to allow it to dry between periods of heavy moisture load...ie: no double vapor barrier. Not too sure, but I would think that in the Pacific NW most air-impermeable yet vapor permeable on both sides would be the way to go. Look to Lstiburek's builders guide for more authoritative answer re vapor barrier and your climate. I would look it up for you, but I've packed all the books away for my move to the midwest.steve
*Mike,I promise you: it will throw moisture in your face when you rip it! Remember, out here, what you get at job site may have been a living tree a week before. (Well, that's a guess, but the moisture's fact.)What you and Steve say--sort of that cels will SPREAD the moisture--makes a certain amount of sense. The situation on the Oregon coast is worsened by the fact that it rains like 334 days a year, so I do't know when the moisture has a chance to go away.Since I think the condition would be far worse in ceiling than in walls, I may just spend the extra 35% and get BCIs. Heck, this little cabin I'm building, I might be able to not insulate/drywall the walls for a year........
*Yes, the best thing would be to live in it a year and burn the woodstove really hot for that first winter, then insulate and close, if that's really an option.Steve
*jim... BCI's ?... another million brain cells down the tubes .. help me out.. what's a BCI ?
*Mike,Boise Cascade's I-joist; pretty much the same (I'm told) as Trus-Joist, TJI's as they're called out here.By the way, whenever I see your tag, I think about the fact (I discovered a coupla years ago) that my first American Lewis ancestor settled in Westerly, RI around 1661; the Lewises, my line, stayed in the area for many generations, and I may still have distant cousins there.
*The "ISP" thread made me wonder if I wanted to consider a SIP roof, to avoid moisture problems in insulation. I think my design would be a natural for SIP: shed style roof, 14' span. But I'd like to find out about the problem Steve mentioned.Heck, maybe I ought to consider SIP walls, too. And floor. (But then--Barry, are you there?--a SIP floor would negate half the reason for Warmboard!
*I tracked down the SIP problem Steve mentioned:http://www.jlc-update.com/archive/12_01/panel_roof.htmlA big mess, obviously. I'm getting a quote for a SIP package (precisionpanels.com) and am going to mail them this article and see what they say. It seems the concensus is that inadequate moisture barrier on inside is allowing moisture to migrate up to SIP joints. But is the problem only happening in Alaska? Why?
*A LOT more roof rot info:http://www.sipweb.com/monitor/monitor_feature.asp
*Jim, The biggest problem I see is venting the wall cavity to the outside and allowing the moisture a way to escape. Using cdx/osb just compounds the problem as both serve very well as a vapour barrier. You would be better off using board sheathing or at least drilling holes ( 1/2" every 12" centers minimum) to allow moisture to escape. Or you could leave a gap on your plywood seams, but to provide adequate sheer, you may be required to block at your joints.I would still go with cells as the best insulation available and mitigate the moisture by allowing your exterior walls more permeability.walk gooddavid
*---a SIP floor would negate half the reason for Warmboard!-- What you are really saying, "if I insulate my home well, I will need less heat. If I insulate my floor, I will have a warmer floor."walk gooddavid
*david,No, what I meant by negating half the reason for Warmboard is that it's 1+" thick comply, designed to serve as subfloor, as well as distribute heat w/ aluminum coating; if I used a SIP floor, the structural aspect of Warmboard would be wasted.
*Whadya talkin' 'bout? Warmboard works in a SIP house! But as a floor, you're right--HALF the reason for Warmboard is its function as a structural subfloor. I would say that Warmboard's structural function wouldn't be wasted--just augmented strongly by the SIP.The extraordinary insulation of a SIP building of the size you are contemplating would probably require little more than the heat from the refrigerator compressor motor to keep the airspace warm in the mild Oregon coast climate.I'm still interested in the green lumber issue... I haven't seen the moisture problem you were concerned about, but a bigger problem is the warping and twisting as the green lumber dries. I believe it is possible to order KD (kiln dried) lumber, or at least lumber that has seasoned naturally in the yard before use. Getting the moisture content stable before nailing, I believe, would be critical. For the rough framing, however, it wouldn't appear to be that important for moisture issues.Barry
*Heh, heh, Barry, I didn't figure you'd miss this trick!I don't think I'll go with SIP, so Warmboard's dearly paid for structural aspects won't be wasted. And I'm pretty sure I'm going to use I-Joists for roof; and I probably should look into dried 2x6's for exterior walls.I really like dense pack cellulose, but don't know where I'd get a blower; I'd be amazed if there was one in Gold Beach.....but I should call the rental place there, and down the road in Brookings.BTW, when I built an unpermitted studio for my wife, I came up with this method for blowing in cels: framed roof, put down sheathing, drywalled ceiling below, using extra screws. Then cut little 6" square holes in middle of each bay in roof sheathing and blew in cels; glue-screwed 1x2 ledgers under holes and screwed sheathing squares back down, and finished roof. It was a lot easier to blow down than it would have been from under.
*Wet fir lumber is nailable. Dry fir is not nearly so. Try it your self. Also... wet fir drys quickly as it does not hold that much water to begin with. I build with wet fir Winters in North Jersey area. I have tried to reuse deconstructed fir and am it is not fun. I do like to save for use as planks.near the fir tree at the bend in the stream,ajps... Kiln dried to 19% SPF mostly Spruce is the framing lumber in the Lake George area. Much easier to work with.
*AJ,You're SO right! Doug Fir is nearly impossible to nail when dry, If I were going to use dry lumber, it'd be spruse or something.So, how fast DOES fir dry? Like?