I’m in the process of building a straw bale house with a vaulted ceiling. All the materials I’ve selected for construction so far have been chemical free and do not off-gas. However, now that I’ve started to look for insulation for the vaulted ceiling, all I can find is Fiberglas batts and blown cellulose, both of which do not meet my criteria for chemical free insulation. Do you have any advice or recommendations you can offer for an insulation product that will meet these criteria?

One product that you haven’t mentioned and that you may consider researching is rock wool.  Essentially, it is an expanded, inert rock by-product often derived from combinations of basalt, limestone and / or mining slag. For instance, a local company in the Kootenays produces a high quality, non- combustible, high R-value rock wool insulation from the abandoned mine tailings located at Grand Forks.

Other “organic” alternatives include wool batts, cornhusks, and sawdust mixed with lime. However, there are problems associated with these products. Even when mixed with lime, sawdust can spontaneously combust due to a phenomenon called pyrolosis. As well, if your structure is being constructed with a building permit, the local building inspector will have objections to use of alternative insulation materials that are not certified for use in the BC Building Code. The logic behind this seemingly intransigent position goes like this.

The building prescriptions and materials that are dictated to builders through the Code ensure that future purchasers of the home you build can expect a minimum performance level from the products that you have chosen for your home today.  Unfortunately, even though you may be satisfied with the performance of an “unapproved” product, in the 100-year life expectancy of a building, the province wants assurances that the most expensive purchase a future buyer makes will meet certain criteria. Even though it often stifles creativity in the building process, the Code does accomplish its mandate for achieving a set of minimum expectations. However, there are options.

Often, the local building inspector will open the door to new ideas by asking you to provide evidence that the product you are proposing to use will meet the existing Code standard. For instance, if you can prove that the insulation product you intend to use meets the same R-value and is equivalent to other criteria specified in the insulation standard, the inspector may accept your proposal.  Be prepared to do lots of research on your proposal. Often, this is how new products come to acceptance.

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This article was written by Steven Cannon, a Registered Building Official and partner in Lynch Building Inspection Services Ltd. of Nelson, British Columbia. It originally appeared in The Nelson Express.

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