Attic insulation inspections in Thunder Bay

Of Thunder Bay's 37,935 houses (single-detached, semi-detached, row houses and duplexes), 43% were built before 1961 and 84% before 1991, according to the 2021 Census. Attics in older houses commonly have a fraction of today's recommended insulation, and top-ups done over the years often buried air leaks instead of sealing them first.

Thunder Bay gets about 5,405 heating degree-days a year, a measure of how much heating its climate needs, and its winter design temperature, the cold day heating systems are sized for, is −28.6°C. Those figures come from the climate data for Thunder Bay in HOT2000, the home-energy software Natural Resources Canada (NRCan) gives energy advisors. That's the 9th-highest heating demand of the 70 cities we cover. The colder the climate, the faster added attic insulation pays for itself, and in a hot summer the same insulation keeps attic heat out of the bedrooms below.

Vermiculite. Loose, pebbly, grey-brown or silver-gold insulation may contain asbestos. Health Canada's advice is not to disturb it; have it sampled before any attic work. Asbestos and vermiculite testing in Thunder Bay

• Seal the air leaks first: top plates, pot lights, plumbing stacks, the hatch.
• Fix ventilation baffles so new insulation doesn't block soffit vents.
• Then top up the insulation. Burying unsealed leaks under new insulation wastes much of the benefit.

What an attic inspection checks.