The R-value is a system used to measure thermal resistance. In other words, it tells you how good a material is for keeping heat in during the winter and out during the summer. The higher the R-value, the better the performance.

In commercial buildings, poor thermal resistance forces HVAC to work harder, using more fuel and leading to an increase in energy bills. The right R-value controls energy costs, keeps indoor temperatures stable, and creates a comfortable environment all year round.

If you own or manage a commercial property, understanding commercial roof R-value isn’t just technical, it’s investing in comfort, durability, and long-term energy savings.

Commercial Roof R-Value Requirements

In Canada, commercial roofing must meet strict local codes for safety and energy efficiency, depending on the region. The baseline requirements are set by the National Energy Code of Canada for Buildings (NECB), and each province adapts them considering local climate conditions.

British Columbia follows the BC Building Code. The province is divided into four climate zones, each with specific requirements. Coastal areas require lower R-values than interior regions. Northern BC demands higher thermal resistance due to extreme temperatures.

The required R-value depends on some factors, including:

The climate zone your building is located in
The type of roof assembly
If the roof is vented or unvented

Buildings with attic spaces in Metro Vancouver need a minimum R-value of R-40. R-value is needed for exterior walls where the thermal resistance of all materials in the construction adds R-value, not only the insulation itself.

Failing to meet the effective R-value indicated on the BC Building Code during new construction builds can lead to costly delays, repairs, or penalties by inspectors. On the other hand, meeting the required value helps avoid high energy bills and allows for a more energy-efficient building.

Types of Insulation and Their R-Values for Commercial Roofs

Spray Polyurethane Foam

Also known as SPF, it’s a liquid which expands into a solid foam and delivers R-6 to R-6.5 per inch, a high R-value insulation per inch. It creates a continuous layer with no gaps, offers moisture, air and high fire resistance, is ideal for irregular surfaces and adds structural strength to the roof.

Polyiso

This material is a rigid foam board usually used in flat roof systems for its characteristic of being compatible with most roof systems. It’s lightweight and easy to install, offering R-5.5 to R-6.5 per inch, a high R-value insulation.

XPS

Extruded Polystyrene (XPS) boards are moisture-resistant and maintain thermal performance over time. It’s a good roof insulation option for buildings in areas with frequent freeze-thaw cycles, with R-5 per inch.

EPS

Expanded polystyrene typically offers R-3.6 to R-4.2 per inch, with stable thermal performance. The material costs less than other rigid foam options and absorbs more moisture than XPS, for example. EPS works well in multilayer and combined systems, and is more cost effective than Polyiso although some roofing manufacturers require a minimum of 2″ inch Polyiso installed on top in order to meet warranty requirements.

R-Value Comparison Chart

Insulation Type	R-Value per Inch	Cost Level	Moisture Resistance
Spray Foam (SPF)	R-6 to R-6.5	High	Excellent
Polyiso	R-5.5 to R-6.5	Medium	Good
XPS	R-5	High	Good
EPS	R-3.6 to R-4.2	Low	Fair

Ready to upgrade your commercial roof insulation R-value? Contact a skilled team for a professional assessment and customized solution that meets your building’s specific needs.

How to Determine the Right Commercial R-Value for Your Building’s Roof

You must calculate the total effective R-value of all your roof components to find the right R-value, which includes all the roof insulation layers, air barriers, and any cover boards or membranes. Also, don’t forget to consider your climate zone and local energy code requirements, if applicable.

For example, consider a flat-roof building in Burnaby, BC, which needs an R-value of at least R-40. To achieve this value, the building owner could combine expanded polystyrene (EPS) as the base layer with polyisocyanurate (Polyiso) on top:

5 inches of EPS insulation, which has an R-value of about R-4.2 per inch, providing R-21.0.
3.5 inches of polyiso insulation, which has an R-value of about R-5.7 per inch, adding R-19.95.

This gives a total insulation R-value of R-40.95. However, this is just the raw roof insulation value. The effective R-value depends on how well the layers are installed, if there are gaps or thermal bridges, and how continuous the insulation is across the roof deck. All these factors often lower the calculated raw value by 10-15%.

Benefits of Optimizing Your Roof R-Value

When you achieve the ideal roof R-value, you’re also protecting your investments, controlling heating costs, saving energy at the same time that increases the building’s energy efficiency, and adopting environmentally friendly actions. For many commercial places, this also means:

Lower heating and cooling costs
Comfortable indoor temperatures
Reduced risk of condensation and roof leaks
Extended roof and HVAC system lifespan

Transform your building’s roof insulation and energy performance today. At Canuck Roofing, we are experts in assessing your current insulation R-value and planning commercial roofing system projects and meet the local building codes requirements, including roof replacement and the right insulation installation.