Is blown-in insulation a fire hazard in New Brunswick homes? | Insulation IQ?

Blown-in insulation is not a fire hazard when it is properly installed using code-compliant materials — and in fact, certain blown-in products offer better fire resistance than some traditional batt insulation. However, there are important distinctions between the two main types used in New Brunswick homes: fiberglass and cellulose.

Fiberglass blown-in insulation is non-combustible. The glass fibres themselves will not ignite or sustain a flame, making this material inherently fire-safe. It carries a Class A fire rating and is widely used in New Brunswick attics for this reason. If a fire occurs in the attic space, fiberglass loose-fill does not contribute fuel to the blaze.

Cellulose blown-in insulation is made primarily from recycled paper or wood fibre, which is naturally combustible. However, all cellulose insulation sold in Canada must be treated with fire-retardant chemicals — typically boric acid, ammonium sulphate, or aluminium sulphate — to meet the requirements of CAN/ULC-S703, the Canadian standard for cellulose fibre thermal insulation. When properly treated, cellulose achieves a Class A fire rating as well. The fire retardants slow ignition significantly and reduce the material's ability to support sustained burning. Independent testing has shown that treated cellulose actually performs comparably to fiberglass in fire scenarios, and some studies suggest it can slow the spread of flame through a wall cavity better than unfaced batts.

The New Brunswick Building Code (which adopts the National Building Code of Canada) requires that any insulation installed in contact with occupied spaces be separated from the interior by a thermal barrier — typically 12.7 mm (half-inch) drywall. This applies in wall cavities and, where applicable, in attic hatch openings. The drywall acts as the fire separation, not the insulation itself, so the combustibility of the insulation is largely mitigated by code-mandated construction.

There are a few practical concerns worth noting. Old cellulose that has lost its fire-retardant treatment — typically in homes from the 1970s or earlier where the product may have been applied without adequate treatment — can pose a higher risk. If you are inspecting or renovating an older home in Fredericton, Saint John, or Moncton and find loose grey material in the walls or attic, it is worth having a professional assess whether it meets current standards. Signs of compromised cellulose include clumping, heavy settling, or a dusty, degraded appearance.

Another concern involves recessed light fixtures (pot lights) that penetrate the attic floor. These fixtures must be IC-rated (Insulation Contact rated) if blown-in insulation will come into contact with them. Non-IC pot lights generate enough heat that contact with any insulation — blown-in or batt — creates a fire risk. This is a common issue in Quispamsis and Riverview homes where pot lights were added after original construction. Blown-in cellulose or fiberglass must be kept clear of non-IC fixtures, typically by building a dam or using a pre-made baffle cover.

Vapour barrier integrity is another consideration. Polyethylene vapour barriers are required in Climate Zone 6 (all of New Brunswick), and blown-in insulation in attics sits above the barrier in the attic floor assembly. This placement is correct and does not create a fire concern. However, if blown-in insulation is being retrofitted into walls via drill-and-fill, any penetrations through existing vapour barrier must be properly sealed to maintain both fire integrity and moisture control.

In practice, blown-in insulation in a properly installed New Brunswick home presents no meaningful fire hazard above that of other insulation types. The bigger risk factors — non-IC fixtures, compromised fire-retardant treatment in old stock, and unsealed penetrations — are all addressed during a professional installation assessment.

If you have questions about the safety of existing blown-in insulation in your home, a certified energy advisor or insulation contractor can assess the material type and condition. New Brunswick Insulation's network lists vetted professionals throughout the province who work with current code-compliant materials.

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Looking for experienced contractors? The New Brunswick Construction Network connects homeowners with qualified professionals:

• Thirty Four Renovations
• 3Tone Construction Ltd
• Arctic Fox Construction Inc.
• Gionetterenovations
• Brunswick insulation & roofing