Question

How can I reduce the formaldehyde released by the fiberglass insulation in the walls of my unfinished basement?

Asked by Jesse
Colbert, WA

I recently purchased a home with an unfinished basement. The builder has already installed fiberglass insulation batts between the exterior and interior wall studs, as well as the ceiling joists of the basement. The exterior walls are also covered with a vapor barrier (6 mil. polyethylene sheeting) as specified by residential building codes in my area. The interior walls of the basement have nothing covering the insulation.While it's nice that the basement is already insulated, I'm concerned about IAQ, particularly with regard to formaldehyde. I'm currently finishing the basement, and I'm ready to sheetrock the walls. Is there a way to "cover" the insulation prior to installing the sheetrock that will further reduce formaldehyde when my basement is eventually finished? Would installing the same 6 mil. polyethylene plastic sheeting over the insulation in the interior walls help to reduce formaldehyde offgassing? Thank you so much for your time and experti

Answer

David Willson

Answered by David Willson

Sebastopol, CA

Advanced Home Performance

January 31, 2012

Jesse,

The amount of formaldehyde in insulation is far less than it used to be and some insulations are made formaldehyde-free.

You can buy a do-it-yourself test kit (google formaldehyde test kit) for $75 or $100 that will give you an approximation of your concentration, if any.

  • If it does turn out to be an issue, ventilation is the only solution - lots of it.
  • Open any windows or outside accesses and put in a fan that blows OUT of the basement.

As far as your question about placing another plastic barrier on the inside of the studs - no, don't do it. With a 6 mil barrier on the outside, any moisture that gets into the wall, up through the bottom sill or just from any puncture, must dry to the inside and can't if there is an interior membrane. 

In a basement such as yours, humidity control is very important. If you don't have a forced air supply going into the basement, I suggest you install a humidity sensor to monitor the humidity level. Keep it under 70%, even if you have to use a dehumidifier.

Lastly, radon is a significant concern in some areas of the Country.

  • Find a radon map of your area or ask around to see if its a concern where you are.
  • If so, special ventilation techniques are required.

Good Luck!

 

For more information:

Read "Does insulation containing formaldehyde continue to offgas into the home after the walls are sheetrocked and painted?" a Q&A answered by William Fry.

Tagged In: home air quality, insulation

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