Insulating an older house in the right order

Why does the order of upgrades matter?

Heat escapes through leaks and through insulated surfaces. A thick layer of insulation over an open gap behind it does little. Air carries both heat and moisture, so stopping leaks first both saves energy and protects the building. After that, spend where the heat loss is largest and the work is easiest to reach.

An energy advisor can rank your house specifically. The home energy audit turns these general rules into a list for your building.

Step 1: seal the air leaks

Common leak points are attic hatches, wiring and plumbing penetrations through the ceiling, around chimneys, at the rim joist, and around windows and doors. A blower door test shows how leaky the whole house is and helps find the worst areas.

Seal with products rated for the job, including fire-safe materials around flues. And keep the other side of the trade-off in mind: a much tighter house needs planned ventilation, ideally a heat recovery ventilator. Combustion appliances that draw air from the room need a safety check after air sealing.

Step 2: attic insulation

Warm air rises and the attic is the largest, easiest area to improve in most homes. Adding insulation on top of existing material is often straightforward. Many older Canadian attics have far less than current guidance, and the programme and code targets vary by region, so look up your area's recommended level instead of copying a number from a neighbour.

Keep ventilation openings at the eaves clear using baffles, and avoid covering recessed lights not rated for contact with insulation. Seal the ceiling below the insulation before adding more on top.

Common mistakes to avoid

Stuffing insulation against the roof deck at the eaves blocks ventilation and invites frost and mould. Skipping the air seal under new attic insulation wastes much of the effort. Using materials that are wrong for damp basements causes rot behind the finish. And hiring on a price per square metre of insulation, without a plan for air sealing, ventilation and combustion safety, leaves the house worse in some respects than before. A written scope, an energy advisor's before and after tests and a contractor who has done the same job before all help.

Step 3: basement and rim joist, then walls

The rim joist, the band of framing at the top of the foundation wall, is a classic leak and cold spot. Insulating it, with an air-sealing layer, is a modest job with a good return. Basement walls come next. Insulating from the inside needs attention to moisture, so fix any water entry first and choose materials that tolerate damp.

Exterior walls are last for most owners. Filling cavities or adding exterior insulation involves cladding or finish work, so costs are higher and the payback is longer. It makes the most sense when you are already re-siding or renovating. Windows come after that unless they are failing, since replacing a window often saves less than sealing and insulating the attic; the windows guide explains how to compare them.

A small example, and why heat loss shrinks heat supply needs

Take an attic of 100 m2 with a modest starting level. Adding insulation lowers the heat flow through that surface; the saving is proportional to the drop in U-value and to the temperature difference over the heating season, which is why cold regions benefit most. Your quote and an advisor's model replace any rough figure here.

Lower heat loss also lets a smaller heating system do the job, whether a furnace or a properly sized heat pump. Drake Landing is the large-scale illustration: its 52 R-2000 homes could run on a low-temperature loop only because their heat demand was small to begin with.

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