Helpful? 0

What would be the best insulation choice for a chemically sensitive family?

What would be the best insulation choice for a chemically sensitive family whose primary concern is indoor air quality for the cathedral ceiling areas that have no attic space?

The home is at 6,000 ft elevation at LakeTahoe, Nevada.

Asked by Neil Adams
Posted Wed, 11/14/2012 - 14:08
Edited Wed, 11/14/2012 - 14:30


3 Answers is currently in maintenance. During this maintenance it is not possible to change site content (like comments, pages and users).
Select your preferred way to display the comments and click "Save settings" to activate your changes.
Helpful? 0

If you install an airtight layer of roof sheathing (for example, taped plywood), you can install all of your roof insulation on the outside of your house. If you go this route, install several layers of rigid foam with staggered seams, followed by strapping and roofing (or strapping, more sheathing, and roofing).

Another approach is to install a structural insulated panel (SIP) roof.

If you choose instead to install insulation between your rafters, most people would probably advise you to choose cellulose and to avoid spray polyurethane foam.

For more information, see How to Build an Insulated Cathedral Ceiling.

Answered by Martin Holladay, GBA Advisor
Posted Wed, 11/14/2012 - 14:36

Helpful? 0

Rigid polyisocyanurate foam placed above a sealed roof deck would have very low risk. It's blown with pentane which outgases quickly with very low lingering VOCs, plus above the roof deck you'd be putting it outside the pressure boundary of the house rather than inside.

You'd still need to ventilate between the roof deck and fiber, but semi-rigid rock wool batts that run ~R4/inch or higher have very low VOCs and none of the friable particulate/aerosol issues of fiberglass. Most rock wool products use the same phenolic formaldehyde binders used in fiberglass as part of the process, but unlike fiberglass batts those chemicals get cooked off in production to extremely low levels by the time it's a finished batt. (Roxul claims something like 13 parts per BILLION formaldehyde in the entrained air of a rock wool batt.)

Most non-expanding injection foams (eg: Corefill 500, TriPolymer, etc.) are zero VOC (blown with air) and chemically inert , and run ~R5/inch. But it's more expensive per unit R than polyiso, which is already more expensive than rock wool.

Also for a lot of money, foamed cement (eg AirKrete, etc) is pretty safe, but I'm not sure it's really the right thing for cathedral ceiling, and it would take a lot of inches of depth to meet code.

Knowing the class of chemicals to which you're sensitive might steer you to one vs. the other based on the MSDS sheet info.

Answered by Dana Dorsett
Posted Wed, 11/14/2012 - 14:55

Helpful? 0

Martin- some people may have issues with newsprint-ink and fire retardents found in cellulose, which have substantial amounts of borates, &/or sulfates. (Borate-only versions are probably less of an issue, and are DEFINITELY nicer to metals, should it ever get wet.) Depends on the sensitivities.

Amongst readily available fiber insulation, rock wool is about as chemical-free as it gets, since anything volatile has long since been burned away in the spinning of the fiber, and even the batt-binders are mostly cooked down to (next to) nothing.

Answered by Dana Dorsett
Posted Wed, 11/14/2012 - 15:00

Other Questions in GBA Pro help

Does a flexible stainless steel chimney flue really need an insulation wrap?

In General questions | Asked by W. Timothy Ward | Jan 26, 15

Flooring questions

In General questions | Asked by sr kod | Jan 27, 15

Got cellulose insulation, how to fix the interior holes?

In Green building techniques | Asked by Alan B | Jan 22, 15

Roxul Comfort Board vs. Thermafiber RainBarrier

In Green products and materials | Asked by Caitanya Joy | Jan 23, 15

Double Staggered-Stud Wall vs. 2x3 + Foam Strip + 2x4 Wall

In Green building techniques | Asked by Jeff Cooper | Jan 23, 15
Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!