What is the safest way to insulate our three story, wood framed clapboard/shingle Victorian house?

Asked by Shellee Colen
Brooklyn, NY

We don't want substances on which mold might grow and or those which prevent the house from breathing. Blown in fiberglass insulation (Atticat) was suggested, but it contains formaldehyde. Are other products safer for our health without being harbors for mold ? How important is it to block up cracks where the walls meet the floors, etc.?



Mold growth occurs when two specific items are present, the first is sustained moisture and the second is a food source. Regardless of the material if these two items are present, mold will grow.

In older homes such as yours, there are many places for water infiltration along with organic material such as pollen and dirt to find its way into the building cavity.

To reduce this type of infiltration you have to begin with installing proper vapor barriers, flashing and maintaining and repairing caulk joints around windows, doors and dissimilar material. The biggest contributing factor to heat/energy loss is air infiltration through opening in the walls, under sill plates, at the attachment to the foundation, around windows and doors. It is key to make sure these areas are sealed and filled.

Now once this is done you must install the proper fresh air intake onto your heating and cooling system so that you do not create a negative pressure zone on the interior of the home when exhaust fans are switched on. Also by having the proper fresh air introduced to your home you will reduce the amount of toxic substances (such as VOC’s and formaldehyde) from building up and creating sick building syndrome.

As for insulation in the walls, there are many types to choose from. The question is to what extent you would like to remove existing walls to access and properly install the insulation.

  • Any system which is blown or injected through holes will not evenly fill the wall cavities and improperly installed could loosen plaster or force clapboards away from the studs.
  • Insulation for attics is easier to install.
  • If possible rely on the insulation manufacturer's safety data sheets (MSDS) to inform you the consumer of chemical compounds in their product. The MSDS is available to everyone, typically on the manufacturers website, and there are many manufacturers whose insulation does not contain formaldehyde.

Again sealing against air infiltration is key and there are a multitude of single and hybrid systems which would do the trick.

To go about this the correct way, refer to the ‘Find a Pro’ section on the Green Home Guide website and locate energy auditors in your area to assist you in making the best decision for your circumstances. The money spent for proper analysis will in turn save you money over the course of years and create a healthier home.

Good luck on your endeavors. 


For more information:

Read "I need to insulate the roof of my 1904 two-family Boston, MA home and I'm looking at air-krete. Please advise." a Q&A answered by Elizabeth DiSalvo.

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