How Insulation Requirements in Ottawa Homes Have Changed Since 1900

When I’m inspecting a home, one of the most common questions I get is:

“Is this enough insulation?”

The amount of insulation I usually find depends heavily on when the home was built. Insulation standards in Ontario have changed dramatically over the past century — and understanding that evolution is helpful to assess whether insulation levels have been upgraded in the past, or need to be now.

Measuring insulation levels

R-value measures how well insulation resists heat flow. It’s a standardized rating that tells us how effective a material is at slowing the movement of heat. The higher the R-value, the better the material insulates.

For some context, this is how much insulation is needed to provide an "R-38" value. R stands for resistance (to heat flow).

Now, here's a decade-by-decade look at how attic and wall insulation has evolved in Ontario.

1900s–1930s: The Pre-Insulation Era

Attics: Typically none 

Walls: None

Homes built in the early 20th century were not constructed with insulation in mind. Walls were often just wood framing with plaster and lath. Attics were frequently empty — or, in some cases, loosely filled with materials like sawdust.

There were no energy efficiency requirements in building codes at this time.

What this means today: These homes often feel drafty and can be expensive to heat unless they've been upgraded.

1940s–1950s: Early Post-War Construction

Attics: Minimal or inconsistent 

Walls: Minimal or none

Insulation started appearing more frequently, but there were still no meaningful energy efficiency standards in Ontario’s building codes. What was installed varied widely by builder.

You’ll sometimes find early batt insulation in walls — but often not at modern levels.

1960s–1970s: Growing Energy Awareness

Typical attic insulation: ~R-12 to R-20 

Typical wall insulation: ~R-11 to R-13

As energy costs rose and awareness grew, insulation became more common in new construction. However, standards were still modest by today’s expectations.

Homes from this era often have:

• 2×4 wall framing with R-12 or R-13 batts

• Modest attic insulation that may now be compressed or insufficient

1980s: Early Code Influence

Typical attic insulation: ~R-20 to R-30 Typical wall insulation: ~R-13 to R-19

By this point, insulation was becoming more standardized. The Ontario Building Code (introduced in 1975) began incorporating clearer thermal performance expectations.

2×6 wall construction (allowing R-19 batts) became more common.

1990s: Energy Standards Tighten

Typical attic insulation: ~R-30 to R-31 Typical wall insulation: ~R-19

Homes built in the 1990s generally have:

• R-19 in 2×6 walls

• R-30 or slightly higher in attic spaces

These homes are usually much more efficient than earlier decades — but still below current new-build standards.

2000s: Significant Improvements

Typical attic insulation: ~R-40 to R-49 Typical wall insulation: ~R-20 to R-24

Energy efficiency became a stronger focus. Attic insulation levels increased significantly, and wall assemblies began improving toward effective R-24 performance.

This period laid the groundwork for major code changes that followed.

2010s: Major Code Shift (SB-12)

In 2012, Ontario introduced Supplementary Standard SB-12 under the Building Code, which formalized much higher energy efficiency requirements.

Typical minimums after 2012:

• Attics: ~R-50 to R-60

• Walls above grade: ~R-24 to R-29 (depending on compliance package)

This was a substantial jump from previous decades and marked a clear shift toward performance-based energy compliance.

2020s: Current Ontario Building Code (2024)

Under today’s Ontario Building Code:

• Attics: Typically around R-50 or higher

• Walls above grade: Typically around R-24 effective

New construction must meet energy performance standards under Standard SB-12, either through prescriptive insulation levels or performance modelling.

Why This Matters During a Home Inspection

When evaluating insulation levels, I don’t judge a 1965 home by 2024 standards.

Instead, I consider:

• What was typical when the home was built

• Whether insulation has been upgraded

• Whether performance concerns (ice damming, high heating costs, comfort issues) are present

Understanding the historical context helps buyers make informed decisions — especially in Ottawa, where housing stock spans more than a century.

Final Thoughts

Insulation standards have increased dramatically over the past 100+ years. A home built in 1920 wasn’t designed for energy efficiency. A home built in 2024 absolutely is.

If you're buying an older home, insulation upgrades can often provide one of the best returns on investment — improving comfort, lowering heating costs, and reducing condensation risks.