How much attic insulation does a Calgary home need?
R-60 is a useful benchmark for a Calgary attic. The City of Calgary lists RSI 10.43, or R-60, for ceilings below attics in its current insulation guidance. An older home is not automatically required to be retrofitted to that level, but it gives you a sensible starting point when planning a top-up.
In many of the older Calgary attics we inspect, we find roughly R-20 to R-30. Most have fibreglass, although we also find cellulose and fibreglass batts. In some much older homes, we have found wood shavings or sawdust with another material added over the years.
Before adding anything, we need to know what those layers are doing now.
How many inches is R-20 or R-30?
R-value measures resistance to heat flow. Depth alone does not tell the whole story: ten inches of one material can insulate differently from ten inches of another.
Here is a rough homeowner reference using Natural Resources Canada's average values. It helps explain an existing measurement, rather than giving an exact rating from depth alone:
Material | Approximate depth |
|---|---|
Blown fibreglass Average R-value per inch: R-2.9 | Approximate depth for R-20: 6.9 inches Approximate depth for R-30: 10.3 inches |
Fibreglass batts Average R-value per inch: R-3.2 | Approximate depth for R-20: 6.3 inches Approximate depth for R-30: 9.4 inches |
Settled loose-fill cellulose Average R-value per inch: R-3.6 | Approximate depth for R-20: 5.6 inches Approximate depth for R-30: 8.3 inches |
Wood shavings Average R-value per inch: R-2.4 | Approximate depth for R-20: 8.3 inches Approximate depth for R-30: 12.5 inches |
These are estimating averages, not installation specifications. Products vary, and compressed, wet or uneven material needs a closer look. In a layered attic, each material has to be assessed separately.
For a product-specific example, Owens Corning's Canadian AttiCat coverage chart lists R-60 at 21.5 inches, with a required quantity of material as well. That describes a full R-60 layer of that product, not 21.5 inches to add over everything already there.
The problem we keep finding at the edges
One recurring finding on our moisture calls is insulation packed over the soffit intake, with no baffles keeping the passage open.
Soffits are the undersides of the roof overhangs. In a vented attic, their intake openings let outdoor air enter low down. Baffles hold a channel between the insulation and roof deck so that air can get into the attic.
Adding more insulation without clearing that path makes the attic look fuller while leaving the blocked intake underneath it.
Where we can access the eaves, we move insulation away from the intake openings, install baffles, and then add the new insulation without blocking the route again. The insulation still needs to cover the ceiling out to the wall; clearing the vent path does not mean leaving the room below with an uninsulated strip around its edge.
What is included in our insulation work?
Air sealing, hatch insulation and baffles where access allows are normally included in our attic-insulation scope. On some low-pitched roofs, there is not enough room to install baffles from inside. We check those limits before planning the work; adding more insulation over a blocked intake is not the answer.
Think of a winter coat with the zip partly open. The padding still helps, but the opening gives warm air an easy way out. Insulation and air sealing do different jobs in a house too: insulation slows heat flow, while air sealing closes the gaps that let air escape.
The attic hatch needs both. A lid with little insulation or a poor seal leaves a weak point in the ceiling.
We use Owens Corning blown-in fibreglass. The proposed top-up accounts for the existing material and the finished level agreed for your home.
We also check what we're about to cover. If we find wet or damaged insulation, that material is dealt with first. Where appropriate, we use Concrobium Mold Control as a preventative mould-control treatment on suitable attic surfaces before adding the new insulation. It does not replace correcting the moisture source, and treated areas are allowed to dry before the top-up goes in.
If the attic is wet, the moisture problem comes first. Covering it with a fresh layer does not repair it. Our companion article, “Ceiling stain after a Calgary Chinook? Roof leak or attic rain?”, explains what we look for.
Questions homeowners ask
Do I need to remove all the old insulation?
Not usually. Dry, serviceable insulation can often stay, including a different material beneath the new layer. Wet, contaminated or badly damaged material needs a separate decision. Suspected vermiculite should be assessed without disturbing it.
How often does an attic need a top-up?
There is no automatic five- or ten-year replacement schedule. The reasons to reassess are low coverage, material that has shifted or been disturbed, moisture damage, or a planned upgrade to a higher insulation level.
Will a top-up help a cold bungalow?
Yes, when heat loss through the ceiling is contributing to the problem. Attic insulation matters in single-storey homes too. Its job is to slow heat leaving the living space, whether that is a bungalow or the upper floor of a two-storey house.
Should I choose the quote with the most bags?
Compare the finished insulation level and the preparation included. Ask specifically about baffles, air sealing and the hatch. A lower price for blowing in material alone is a different scope of work.
Find out what your attic actually needs
Book a free insulation assessment with TrueFlight. We'll check the existing insulation and explain the preparation and top-up your attic needs. If you are already replacing the roof, we can discuss the attic work at the same time.
Call us directly: 403-879-8988.
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