Hate to do this, but FG versus cellulose
Looking to sub blown-in for my attic, new construction, SE MN climate (worst case 100 degree design delta minus 30 > +70). Daily delta can be, and often is, 30 or 40 degrees.
Have heard numerous times on this forum about the superiority of cellulose over FG, about how air moves freely through FG, moisture condenses on FG, at super low temps convection in the FG lowers the R-value, etc etc. Got me convinced to go with cellulose rather than FG. BUT,
Calling around to insulation contractors…they say no-one around here (Rochester, MN) even thinks about blowing cellulose, that it holds moisture, eventually settles and lowers its R-value, get call backs, etc. Say that with temperature extremes that we have here, cellulose is worse at moisture retention than FG…but do agree that cellulose would be better in warmer or more stable climate.
So…without getting into long drawn out chevy-versus-ford thread, what’s up with this? Also, one contractor says he uses Certainteed blown in FG, that he can get R-40 with 14″….seem light to me.
Edited 1/21/2004 10:12:56 AM ET by johnnyd
Replies
In one of the other discussions, someone, perhaps Mongo, posted a link to the results of a national lab's test of R-value; FG v cellulose. Cellulose clearly won, particularly at colder temps. Search the old threads for that.
Yes. cellulose holds moisture. It also dries out as conditions change. I don't see moisture as a concern if you do a good job air sealing, which is good practice no matter what insulation you choose. No inside air reaching the insulation during the winter, then no moisture problems.
As to cellulose losing R-value as it settles, that's pure bull pucky. Well, sort of. Yes, it loses R-value as it settles. However, by law, the R-values published for cellulose are for the eventual settled thickness of the stated just-blown-in thickness. You get what you pay for.
I know, I read that...which is why I'm posting now...big inconsistancy...are these guys that I'm calling that far behind? Or is there a financial incentive to them blowing FG?
They are that far behind & they have the equipment to do what they've always done.
Joe H
What Joe said.
This is going to sound arrogant, but it's not meant that way. One thing that I've learned from 15 years in the trades followed up by 7 years at FHB is that a depressing percentage of tradespeople really don't know much about what they do. It's just a job, and don't bother them with having to learn about it. (And while most of the folks at Breaktime represent the other end of the spectrum, it's even hard to get them to agree:)Andy Engel, The Former Accidental Moderator
Well, I guess I'll get on the phone, then, and try to find one "enlightened" insul guy. Sure don't want to DIY this one!
Actually, if you're just blowing cellulose into an open attic, it's a perfect DIY job. Around here, if you buy the material from them, Lowes will loan you the blower. I've done it several times and find that I quite enjoy the Zen of cellulose blowing.Andy Engel, The Former Accidental Moderator
I'm doing the electrical, plumbing, wall insulation, hanging the drywall, RFH, flooring, painting, and trim...but two things I WON"T do are (1) crawl up there and hope I get the insulation where it needs to be (I don't like balancing on truss chords), and (2) taping and finishing the drywall for the common reasons.
Actually, a www search yeilded a "nu-wool" contractor in the area...left him a voice mail.
> I'm doing the electrical, plumbing, wall insulation, hanging the drywall, ....
Be sure to get all that stuff done before you have anything blown in. The big downside to blown-in is that it's a major pain to work on anything else once it's in the way.
Does anybody know of a kind of insulation that gets you good R values, and is also easy to work around or to R&R?
-- J.S.
Tell me about it, that's what I've been scrambling to do the last X weeks, trying to get the lid on and heated. Going to be -9 tonight with wind chill -20 to -30. Every time I think I'm just about ready for sheetrock, I find something else to finish up.
Did find some excellent socks at Sam's Club. 85% lambswool. ~ $4 a pair. Put those under another pair of worksocks, toasty warm and dry toes.
However, ceiling rock is delivered and stocked, lift, SR gun, and helper lined up for this weekend.
Other posters have said they much prefer to work around cells than FG.
Edited 1/21/2004 1:54:47 PM ET by johnnyd
How does cellulose perform if I blow it in on top of the exsisting fiberglass batts that are allready up there. I like the price of cellulose but the previous experince I have had with FG.
a topping of cells will improve the performance of the fiberglass underneath since there is no where for air to move to...
if i had fiberglass in my attic, i'd just blow a topping of cells..i wouldn't go to the expense and bother of taking the fiberglass out... fiberglass is a good insulator if you can keep the air from moving thru it or around itMike Smith Rhode Island : Design / Build / Repair / Restore
Seems EVERY insulation contractor in SE Minnesota either is too busy to return calls or only blows FG.
All you cellulose fans out there...can you give me any help in finding a contractor who will blow cellulose and also return calls?
Or do I need to figure out a way to DIY this too?
Edited 1/23/2004 9:27:39 AM ET by johnnyd
No one has mentioned it - so I will.
Spray Foam Insulation. Might be worth a look. High intial cost, but good payback on the utility bills.
Blows FG away (no pun intended).
Pinemarten
Already ruled it out due to the high initial cost. R value is R value, and I'm detailing sealing out air leaks myself...besides, this is only 1600 sq ft total, partially birmed on north side..all daytime living areas have generous, efficient windows facing south.
Bedrooms, laundry, air-lock mudroom all on north with small windows.
Find Mike Smith's comments about trying to air seal. Even if picky-picky you will have problems down the road. Once you have air convection, you loose ground (or heat as the case maybe) rapidly. It sounds like the new soy-foams are not as expensive as others, and maybe a "thin" coat to seal, with cells blown on top may be your answer.
Just food for thought.
Pinemarten
How does all this pan out for a house in Florida? Vapor barrier theory, largely formed and modeled on a cold climate, seems to get more complicated for Floridians.
We pretty much follow the model well in the cold portions of winter. The outside is cold, below the dew point for the relative humidity. The interior is filled with warm, moist air. If it was allowed to the warm, moist air inside would migrate outward until it reached the dew point within the insulation. As this point the warm air would cool enough to drop its water.
Soaked insulation, I think most will agree on this point, is not good but if it only a small amount of moisture, and if it dries out relatively quickly, it does little long term harm. It lowers the R value but not the end of the world.
Of course the standard model for vapor barriers is that they are placed between the moisture source, consistently inside on a house in the north where the heating season is most of the year, and the insulation. The problem being that while this is grand for the whole month of winter here it reverses during the six months of summer.
During the summer the exterior is warm and moist, humidity hovering around 90% morning and evening, while the interior is air conditioned to something close to 75F. In these conditions it would seem that the vapor barrier should be on the outside.
First thought is a vapor barrier on both sides. Sounds good as long as everything is sealed completely and no moisture gets into the wall. Of course a complete seal is highly improbable if not impossible. In the case of any failure the moisture trapped between the barriers would remain there long term. Rot and mould would be the likely outcome.
No vapor barrier would be one way, the early houses had no barrrier but little insulation to hold moisture either. Assuming good interior ventilation to moderate the moisture there might be enough air movement to allow any moisture to disipate. I don't know.
The interior moisture sources are stronger. People and their activities tend to be wet. Exterior moisture can be close to 100% RH for 6 hours, morning and evening, for months.
The temperature gradient is much higher in winter, as much as 50F, mostly close to 30F. Only about 30F maximum during the summer with something like 20F being a working average.
The rainy season is in the summer, often a heavy shower twice a day, and fall. Spring less wet. The winter is drier with occasional rainfall but not uncommonly dry for weeks.
Any ideas?