Attic Insulation.
Red Deer sits in Climate Zone 7A. A ceiling below an attic has to reach an effective RSI 10.43 (R-59.2) with no heat recovery ventilator, or RSI 8.67 (R-49.2) where an HRV is installed — Tables 9.36.2.6.-A and -B of the 2023 Alberta code.
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Most attic work in Central Alberta is an air sealing job with insulation on top of it. The code number is effective RSI, measured across the whole assembly, so what the ceiling plane leaks counts for as much as what sits above it.
Every Zone 7A figure a permit actually asks for — ceilings, walls, floors, foundations, slabs — is laid out clause by clause in our Alberta code compliance guide including which table each number comes from.
What Attic Work Actually Involves Here.
Two different parts of the code govern a Zone 7A attic at the same time — the energy requirements in Section 9.36 and the venting requirements in Section 9.19 — and they constrain each other at the eave, which is where most attics are quietly non-compliant.
- The ceiling air barrier first. Article 9.25.3.1 asks for a continuous barrier to air leakage both outward and inward, and names limiting soil gas entry as one of its jobs.
- Effective RSI 10.43 (R-59.2) for a ceiling below an attic in Zone 7A with no HRV; RSI 8.67 (R-49.2) where a heat recovery ventilator is installed.
- The eave relief in Sentence 9.36.2.6.(3): a reduction is permitted for no more than 1 200 mm, only as far as roof slope and minimum venting clearance force it, and nominal RSI 3.52 (R-20) is still required directly above the exterior wall.
- Venting kept legal where the attic stays vented — unobstructed vent area of 1/300 of the insulated ceiling area, or 1/150 where the slope is less than 1 in 6 or the roof is framed with roof joists (Article 9.19.1.2).
- Clearances held: 63 mm between the top of the insulation and the underside of the sheathing, at least 25 mm at a preformed baffle, and the baffle carried at least 50 mm above the insulation (Article 9.19.1.3).
- The penetrations that actually cost you the rating — hatch, top plates, plumbing stacks, chimney chase, pot lights, bath fan ducts.
- Where closed-cell foam is used at the ceiling plane, it clears the code's air barrier material threshold at roughly 25 mm: published Canadian products measure around 0.002 L/(s·m²) at 25 mm against the 0.020 limit in CAN/ULC-S705.1.
- Foam inside a concealed attic space needs no thermal barrier of its own — Article 9.10.17.10 carves concealed attic and roof spaces out, and the ceiling gypsum below does the work. Foam left exposed in an accessible, conditioned attic is a different case and has to be covered.
How an Attic Gets Scoped.
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Vented or unvented
A vented attic keeps insulation at the ceiling plane and Section 9.19's ratios apply. Bringing insulation to the roof deck instead makes it an unvented assembly, which in Alberta runs under STANDATA 23-BCV-017 and a different R-value. Two assemblies, two rulebooks — the decision comes first.
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Find the leaks before adding depth
Effective RSI is an assembly measurement, not a product label. A hatch with no gasket, an open chimney chase and eight pot lights will hold a nominally deep attic well below its stated rating.
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Set depth against Table 9.36.2.6
RSI 10.43 without an HRV, RSI 8.67 with one, and the 1 200 mm eave relief at nominal RSI 3.52 where slope and baffle clearance genuinely force it.
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Protect the airflow path
63 mm above the insulation, 25 mm at the baffle, baffle 50 mm proud, and vent area split with at least 25 percent high and 25 percent low. Buried soffits are the single most common reason a re-insulated attic reads damp the following spring.
Frequently Asked Questions About Attic Insulation
How much attic insulation does the Alberta code require in Red Deer?
Effective RSI 10.43 (R-59.2) for a ceiling below an attic with no heat recovery ventilator, or effective RSI 8.67 (R-49.2) where an HRV is installed. Those are the Zone 7A columns of Tables 9.36.2.6.-A and -B in the 2023 Alberta edition of the National Building Code. Note the word effective: the figure is for the finished assembly including heat flow through the framing, not the nominal number printed on a bag or a batt. Alberta adopted Tier 1 only, and under AR 5/2024 a municipality or accredited agency cannot require a higher tier than that.Is spray foam the right choice for an open attic floor?
Often it is not, and it is worth saying so. Where there is an open attic floor with headroom to build depth, loose-fill insulation buys more R-value per dollar than foam does, and other Canadian contractors publish exactly that comparison. Spray foam earns its price in an attic where the real problem is air leakage, where there is no room to build depth, where the geometry is complex, or where the assembly is being taken unvented at the roof deck. If the honest answer on your attic is blow more in and seal the ceiling plane properly, that is the answer you should get.Does an attic still have to be vented if spray foam is used?
It depends where the foam goes. Insulation at the ceiling plane leaves a vented attic above it, and Section 9.19 still applies in full — 1/300 vent area, or 1/150 for shallow slopes and roof-joist roofs, split at least 25 percent top and 25 percent bottom, with 63 mm of clear space above the insulation. Insulation applied to the underside of the roof deck creates an unvented assembly instead. Alberta permits that in Part 9 buildings province-wide under STANDATA 23-BCV-017, provided the design requirements of the RDH Building Science report it names are followed and that report goes in with the permit application.Does spray foam in an attic need to be covered with drywall?
Not where the attic space is concealed. Article 9.10.17.10 requires foamed plastics in a wall or ceiling assembly to be protected from adjacent space, but explicitly excludes concealed spaces within attic and roof spaces, crawl spaces, wall assemblies and ceiling assemblies — in a normal vented attic the ceiling gypsum below is the thermal barrier. An accessible, cathedralized attic with foam left showing is not concealed and does need an interior finish, sheet metal at least 0.38 mm thick with a melting point of 650 °C or higher, or a listed thermal barrier. One caution worth knowing: a Nova Scotia mutual insurer refused in 2018 to accept a sprayed intumescent coating in place of board covering, at a cost of about $3,700 to the homeowner, even though the coating complied. Confirm with your insurer before choosing a coating over drywall.Will a better attic cut my heating bill in half?
No, and anyone promising that is guessing. What can be said with a source: space heating accounted for 65.6 percent of Alberta residential energy use in 2021, per NRCan's National Energy Use Database — higher than the national 60.1 percent. US EPA modelling of comparable homes puts air sealing plus insulation at about 11 percent of total energy costs, or 15 percent of heating and cooling, across a 5 to 16 percent range with northern climates at the top; that is US modelling and should be read as such. Percentage-of-bill claims also overstate the case in Alberta, because a fixed daily delivery charge on a gas bill does not move no matter how little gas you burn.What is the difference between nominal and effective RSI?
Nominal is the rating of the insulation on its own. Effective is the whole assembly, including the framing that conducts heat around the insulation. The code's Table A-9.36.2.4.(1)-A treats a rafter roof at 406 mm on centre as roughly 13 percent framing and 87 percent cavity, and that framing fraction is why a ceiling full of nominal R-60 does not automatically deliver effective RSI 10.43. Every number in Section 9.36 is an effective number.