New 2025 Ontario Building Code Targets Radon in New Home Builds
New 2025 Ontario Building Code Targets Radon in New Home Builds What it means for homeowners in Kitchener, Waterloo, Cambridge & Guelph
In a move that puts radon safety front and center, Ontario's 2025 Building Code now mandates rough-ins for radon mitigation systems in all new residential construction. This update reflects growing awareness of radon gas risks - particularly in regions like Kitchener, Waterloo, Cambridge, and Guelph, where certain soil compositions have been linked to elevated radon levels.
Why the Change? Radon is the second leading cause of lung cancer in Canada, yet it's completely invisible and odorless. The only way to detect it is through proper testing. By requiring mitigation-ready infrastructure in new builds, Ontario is taking a major step toward prevention.
What Does This Mean for Homeowners? If you're buying a newly built home in 2025 or beyond, it will likely include a radon mitigation rough-in - an access point that allows for easier installation of a radon fan if testing shows unsafe levels.
However, if you live in an existing home - especially in parts of Guelph's south end or near the Grand River in Kitchener - you still face risk. Homes built before this code update won't have these systems, and testing becomes even more critical.
Our Local Take: What We're Seeing At South West Radon Pros, we've noticed more builders and buyers asking about radon, especially in Cambridge's newer developments and older homes near Uptown Waterloo. These conversations are important - because the earlier you plan for radon safety, the easier it is to protect your health.
Why This Matters for KWCG Residents Kitchener, Waterloo, Cambridge, and Guelph lie on the edge of the Canadian Shield and the Great Lakes-St. Lawrence lowlands - geology that can trap radon. While not every home is affected, we've seen homes test over 400 Bq/m³, well above Health Canada's recommended limit of 200 Bq/m³.
Next Steps for Homeowners and Buyers
- Test your home - especially if it was built before 2025.
- Ask builders if the new home you're considering includes radon rough-ins.
- Contact South West Radon for certified testing and mitigation that meets (and exceeds) the new standards.
Closing Thought The 2025 code changes are a big win for public health - but they're just the beginning. Whether you're buying, building, or already settled in, radon awareness and proactive testing remain the most important tools in your toolkit.
Further Reading / References:
- Health Canada - Radon: What You Need to Know
- Ontario Building Code 2025 Updates (Government of Ontario) (look for radon-related amendments in Part 9)
- Take Action on Radon - National Radon Program in Canada
- CMHC - Radon Control in New Construction
- World Health Organization - Radon and Health
- Waterloo Region - Public Health and Radon Testing
- WDG Public Health - Radon Testing in Guelph
<h3>Further Reading / References:</h3>
<ul>
<li><a href="https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon.html" target="_blank" rel="noopener">Health Canada - Radon: What You Need to Know</a></li>
<li><a href="https://www.ontario.ca/laws/regulation/120332" target="_blank" rel="noopener">Ontario Building Code 2025 Updates (Government of Ontario)</a></li>
<li><a href="https://takeactiononradon.ca/" target="_blank" rel="noopener">Take Action on Radon - National Radon Program in Canada</a></li>
<li><a href="https://www.cmhc-schl.gc.ca/en/professionals/industry-innovation-and-leadership/industry-expertise/building-technology/indoor-air-quality/radon" target="_blank" rel="noopener">CMHC - Radon Control in New Construction</a></li>
<li><a href="https://www.who.int/news-room/fact-sheets/detail/radon-and-health" target="_blank" rel="noopener">World Health Organization - Radon and Health</a></li>
<li><a href="https://www.regionofwaterloo.ca/en/health-and-wellness/radon.aspx" target="_blank" rel="noopener">Waterloo Region - Public Health and Radon Testing</a></li>
<li><a href="https://wdgpublichealth.ca/blog/reduce-your-radon-risk" target="_blank" rel="noopener">WDG Public Health - Radon Testing in Guelph</a></li>
</ul>
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