What is the difference between R-20 and R-24 insulation for the British Columbia building code?

R-20 and R-24 insulation both refer to thermal resistance values, with R-24 providing 20% better insulation performance than R-20. The main difference is that R-24 insulation resists heat transfer more effectively, reducing energy costs and improving comfort in BC's varied climate.

Understanding R-Values

The "R" stands for thermal resistance — how well the material resists heat flow. R-20 means the insulation provides 20 units of thermal resistance, while R-24 provides 24 units. Higher R-values mean better insulation performance. In practical terms, R-24 insulation will keep your home warmer in winter and cooler in summer compared to R-20, while reducing heating and cooling costs by approximately 15-20%.

BC Building Code Requirements
Under the BC Building Code 2024, minimum insulation requirements vary by climate zone and building component. For Metro Vancouver (Climate Zone 4), typical requirements include R-20 minimum for walls and R-31+ for ceilings. However, the BC Energy Step Code pushes these minimums higher — many municipalities now require Step 3 compliance, which often means R-22 to R-24 walls and R-40+ ceilings for new construction and major renovations.

Material Thickness Differences
The thickness difference depends on the insulation type. For standard fiberglass batts, R-20 is typically 6.25 inches thick, while R-24 is about 7.25 inches. For spray foam, R-20 requires roughly 3.5 inches of closed-cell foam, while R-24 needs about 4.2 inches. This thickness difference can impact framing requirements — 2x6 walls easily accommodate R-20 batts, but R-24 may require 2x8 framing or advanced framing techniques.

Cost and Performance Trade-offs
R-24 insulation typically costs 15-25% more than R-20 but provides long-term energy savings. In Vancouver's climate, the upgrade from R-20 to R-24 wall insulation can reduce heating costs by $150-300 annually on a typical 2,000 sq ft home. The payback period is usually 8-12 years, making it worthwhile for new construction but requiring careful cost-benefit analysis for retrofits.

When to Choose Each
Choose R-24 for new construction, major renovations, or when pursuing Energy Step Code compliance. R-20 may be sufficient for minor renovations where framing constraints limit options, but check with your local building department first. Remember that insulation is just one component — proper air sealing, quality windows, and continuous thermal barriers are equally important for energy performance.

For any insulation upgrade project, consult with energy advisors and insulation contractors who understand BC's climate requirements and can ensure proper installation for maximum performance.