BIBS fiberglass dense pack vs. cellulose dense pack
After reading about all I could find on dense pack fiberglass vs cellulose (which is much less then I’d have expected)…I decided I’d love to have cellulose in our new +- 3000sf home/shop that is being built in Western SD…BUT…I cannot find any professionals to install it.
We have taped the seams of the osb and brought the air seal across the ceiling. We are installing a HRV. Lets call it zone 6b
While I’d love to have cellulose installed…I cannot find anyone to do it. Everyone used to, but the ease if trucking and installation of dense pack fiberglass seems to have driven all the local installers away from cellulose.
I could gear up to do the cellulose dense pack myself….Ive never done it, but can rent a force2 blower and buy the needed tools and give the insulation project a week of my life trying to get it right.
But after doing the math…it saves me maybe $1500 -$2000 compared to having a respected professional outfit come in and do a BIB system without me lifting a bale of cellulose or making several 100 mile round trips to the nearest menards to get materials.
Right now I’m leaning towards having a professional dense pack the fiberglass…..as a quality install seems as important as product when insulating. I’m in the process of talking them out of using poly, and just blowing into their version of insolweb.
Near as I can tell, modern day dense pack fiberglass at 1.8+ pounds per sq ft. insulates and slows air/vapor flow nearly as good as dense pack cellulose at 3 or 3.5 pounds per sq ft.
The fiberglass might not be as eco or as fire resistant as I’d like it to be, but are there any other major detractors that I’m missing that should compel me to try and insulate my house myself?
Thank you for your advice.
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Cellulose has several advantages over BIBs systems. One is the fact that cellulose has very low embodied energy in its production. That's important to the Earth but isn't something you will see personally. Something that you will see and is very important is that cellulose is hygroscopic. That is, it acts like a reservoir for humidity and will quickly distribute any point of excess moisture to points of lower moisture within the cellulose wall. A lot of FG dense packers don't understand that this is a GOOD thing, but it is.
That's especially important in colder climates like yours. One of the biggest dangers to houses over the long term is condensation of water on wall sheathing. Besides all the other known good qualities of cellulose this wicking away of excess moisture from local sheathing damp spots is a really good thing. It gives a house resilience from the imperfections that always creep into the building process no matter how hard you try to avoid it.
I hope you are able to do it yourself. I did my house and it wasn't that hard. The best thing to do is to start on one interior wall until you get the hang of it. It doesn't take long. The only limitation on doing it yourself is the thickness of the wall. If the framing is greater than 6 inches thick I'm not sure any of the rental blowers, including the Force 2, is capable of making it dense enough that it won't visibly slump at the top over time.
Daryl,
Leaving aside the issue of embodied energy, and focusing on performance, I would say that either product should perform well. As you noted, conscientious installation matters more in this case than the material chosen.
If your wall system is well designed, and you pay attention to airtightness, and you have good exterior water management details (flashing and -- ideally -- a ventilated rainscreen), there is no reason to worry about moisture accumulation in your wall assembly, regardless of whether you choose blown-in fiberglass or cellulose.
Thank you both for you thoughts...and your encouragement Eric. I will most likely call a few more places looking for installers/supplies. The largest bays I have are about 7' tall by 22.5" wide by 7" deep...so i guess the power of the force2 might be the straw that breaks the camels back on this choice. Everything I'm dense packing is 7" deep.
I'm finding out over and over that the devil is in the details and many of the things that seem easy on paper, are more difficult to pull off in practice when you consider the education, tools, and materials which must be rounded up to do them properly.
Even if it cost more to get cellulose done correctly I'd most likely do it, as I believe what Eric saids has merit, but it just seems difficult to pull off in this neck of the woods.
Is adding certainteeds 'smart' membrane...a smart move? I know that one of the downfalls of fiberglass dense pack is that it does not deal with vapor as well as cellulose. In a dry climate like we have here in far western SD...is the use of Certainteeds membrane a good thing in a wall that uses air sealed OSB on the outer side, and dense pack fiberglass as insulation?
Daryl,
The best wall for your climate would include insulation on the exterior side of the wall sheathing; this could be rigid foam or mineral wool. The exterior insulation helps keep the sheathing warm and dry.
You didn't mention any exterior insulation, so it may be too late for you to take advantage of this advice.
If you are building conventional 2x6 walls without any exterior insulation, the two most important steps you can take to protect your wall sheathing are (a) Pay close attention to airtightness when building your wall, and (b) include a ventilated rainscreen gap between your WRB and the back of your siding.
Once you've taken those steps, a third step would be to install a smart vapor retarder like MemBrain. There is no down side to MemBrain -- it's a good product -- other than its price.