Replies

1. GBA Editor
   Martin Holladay | May 11, 2014 06:03am | #1

   Laura,
   "Toxic" means poisonous. Neither open-cell spray foam (with soy components) nor cellulose poses a poisoning risk when properly installed, although a small number of homeowners have experienced lingering odor problems and health complaints with some types of spray polyurethane foam. (For more information on these cases, see Spray Foam Jobs With Lingering Odor Problems.)

   The percentage of soy-derived chemicals in spray foam that advertises its soybean content is quite low, so I wouldn't choose an insulation based on the (mistaken) idea that the percentage of soy-derived chemicals is significant.

   Open-cell spray foam and cellulose insulation both have about the same R-value per inch (about R-3.7 per inch).

2. Expert Member
   MALCOLM TAYLOR | May 11, 2014 09:11pm | #2

   "open-cell spray foam poses … (no)... poisoning risk when properly installed, "

   Ah, but there's the rub:
   http://www.cbc.ca/marketplace/blog/is-spray-foam-safe

3. 
   lalollie | May 11, 2014 10:39pm | #3

   I'm in Alaska and need a higher R factor (closed cell). Frankly am leaning to rock wool or fiber glass by CertainTeed with plant binders and no formaldehyde. Out gassing is an issue for me.

4. Expert Member
   Dana Dorsett | May 12, 2014 11:16am | #4

   Cellulose has no appreciable outgassing issues other than very modest amounts found in the newsprint ink (being predominantly a recycled newsprint product.)

   Cellulose (unlike fiberglass & rock wool) can buffer significant amounts of wintertime moisture accumulation without damage or loss of function. This can be both a benefit and a problem in very cold climates- the cellulose protects the structural wood by sharing the wintertime moisture burden, but it's drying rates can be slower than other fiber insulation during the relatively brief drying season, raising the importance of air sealing the interior side of the assembly, and keeping the interior side vapor permeance low. Cellulose is more air-retardent than batt solutions, which helps, and in general the net benefit outweighs any risk. (Air sealing and permenace control is important with all insulation types.)

   As a rule, blown insulation delivers a more perfect fit than batt solutions.

   Higher density fiberglass is more air-retardent than mid-density goods, all currently available rock wool is comparable in air-retardency to HD fiberglass. Blown fiberglass needs to be 1.8lbs per cubic foot or higher to be comparable to the air retardency of cellulose, and at 2.2lbs density is more air retardent than cellulose.

   Fiberglass batts has more outgassing issues than rock wool batts, since the volatile components of the binders are mostly cooked out during the high temperature processing of rock wool batts during manufacture.

   Most closed cell foam is blown with HFC245fa as a blowing agent, which takes several decades to outgas, but it also steadily releases low amounts of polyols and fire retardents throughout it's lifecycle. HFC245fa is a powerful greenhouse gas (about 1000x CO2), which can be reason enough to limit where and how much one uses- not what you would want to use for attaining high R-values. It may be reasonable for use in air sealing and moisture control in some applications, but it's not exactly "green" as insulation.

5. 
   lalollie | May 12, 2014 12:51pm | #5

   Humidity and moisture retention is not a problem here; on the contrary we are excessively dry and encounter numerous challenges due to our arid climate (especially in the winter)

   CertainTeed has developed plant binders rather than using formaldehyde. This is relatively new and available now for both kinds of batting. Also I understand that sound proofing is better with the rock wool and a little better R factor.

   Outgassing of the fire retardants is a concern for the cellulose. However a house in Southern California has 15 years of dependable insulation for both hot and cold conditions with blown in cellulose, and it is a great choice for remodels. This house is forced air, with excellent ventilation. The Alaska house has a boiler, with code approved ventilation, but poorer air circulation in the winter and a tighter seal overall.

6. Expert Member
   Dana Dorsett | May 12, 2014 01:21pm | #6

   In a cold climate such as the interior of AK the exterior layers of the assemblies dwell for months on end at temps well below the dew point of healthy (for humans) conditioned space air. That means that air-leakage from the interior into the insulated assembly will give up it's moisture to the colder wood/insulation/other, which can lead to mold & rot issues over time.

   Even with an air-tight interior vapor diffusion through latex paint can occur at rates higher than the exterior sheathing can accomodate it by drying toward the exterior. Latex paint on wallboard tests out at about 3-5 perms, compared to 0.8-1.5 perms for OSB, or 1-2 perms for half inch CDX. That is why in cold climates it's common to put 6-mil polyethylene (~0.03-0.05 perms) between the wallboard and insulation in these climates, which becomes something of a two-edged sword, since it blocks any drying of the assembly toward the interior.

   The borate fire retardents used in cellulose are non-volatile and have very low human toxicity. Products that contain ammonium sulfate fire retardent can outgas ammonia if it ever becomes wet, and are to be avoided. Almost all "stabilized" cellulose use in damp-sprayed applications is borate-only / sulfate free, and is preferable (even for dry blown) on a number of grounds. The MSDS sheets for specific cellulose products describe all chemicals that have been added, but do not specify the contents of the inks (which vary by feedstock source.)