Radon in New Homes: A Canadian Perspective on a Silent Threat

Radon is a naturally occurring radioactive gas found in soil and rock throughout Canada. Because it is colorless and odorless, radon can accumulate indoors without detection. Health Canada estimates that radon exposure contributes to more than 3,200 lung cancer deaths each year, making it the second leading cause of lung cancer after smoking. Contrary to popular belief, radon is not limited to older homes. Modern energy-efficient construction can actually increase radon accumulation if mitigation systems are not properly installed.

Canada's Radon Reality: It's Widespread, Not Isolated

Radon gas does not respect geographic boundaries and is widespread throughout Canada, including in Radon in new homes, with concentrations that vary with the local geology of the area where a home is built. While Health Canada hasn't conducted extensive research on Radon levels in new homes, it has found that approximately 7% of surveyed homes have Radon concentrations above the Canadian guideline of 200 Bq/m³. Uranium is a significant contributor to the radiological context of the Canadian Shield. However, homes across Canada can experience elevated Radon concentrations. In new homes, especially in Radon, the risk without built-in safety systems is even greater.

Decoding Radon Entry: Understanding the Home's Interface

Understanding how these factors vary by home type is essential for effective radon risk mitigation. Although geology is the bedrock of everything, it is primarily the building's interface with the geology that drives Radon ingress. 

Radon Concentration and Soil Permeability

The first component is the Radon concentration, and the second is the soil's permeability. Granitic soils, shales, and some glacial deposits have higher concentrations of uranium and, consequently, Radon. Then, there is permeability, the ease with which Radon and other gases move through the soil. 

Foundation and Structural Entry Points

Any hairline fractures in your foundation, floor drains, sump pits, or utility penetrations can break the seal and allow air to flow into the basement. Even with the soil gas being warmer, there is still some ingress with the concrete because the porous concrete and direct openings are more often the greater contributors.

Indoor–Outdoor Pressure Differences (Stack Effect)

Lastly, there is the indoor-outdoor pressure differential, also known as the stack effect, which is most pronounced in colder climates such as Canada. Some of the warmer air in the house rises and exits through the higher openings. This leads to a reduction of atmospheric pressure in the lower levels of the building. This reduction in pressure is called negative pressure, and it causes soil gases (including Radon) to enter the building through any available openings or cracks. This pressure effect is more enhanced the taller a building is, and the colder it is outdoors. This means different building types have different Radon levels. It is a potentially dangerous phenomenon. Each of these situations leads to a different set of unique variables, which is exactly why a standardized approach to Radon mitigation does not work.

The Modern Myth of Radon in New Homes

There are widespread misconceptions regarding the presence of Radon in new builds. In Canada, building codes and construction methods are relatively new. The misconception about Radon in new builds could be reckless. Construction methods have focused on the building envelope, or exterior of the building, bringing new builds to a whole new level in energy efficiency. However, the paradox is that these methods are leading to higher Radon concentrations. Without installing radon gas prevention measures before construction is complete, the problem will worsen.

Modern Construction and Reduced Natural Ventilation

When considering new Canadian homes, the obvious construction methods and thereby building-envelope materials come to mind: sealed windows, construction-level air barriers, spray or board foam insulation, and other measures that aid energy efficiency and climate control. But it also means the home will have reduced natural ventilation. If Radon gas is allowed to enter the home during the construction of a new home, or before Radon gas prevention measures are completed, Radon gas can accumulate to higher and higher levels.

Passive Systems and the Need for Active Radon Mitigation

While passive systems are a great start, they are not enough, and most of the time, they do not lower Radon concentrations below the guideline established by Health Canada. This is the reason why testing after people move in becomes impossible to negotiate. If testing shows a Radon concentration above 200 Bq/m³, that rough-in pipe becomes an integral part of the building. It can be easily converted into a working active sub-slab depressurization (ASD) system by adding an inline fan. This fan operates continuously, drawing Radon gas from below the slab and safely venting it outside.

Older Canadian Radon in New Homes: Unique Challenges and Smart Retrofits

Older Canadian homes present additional radon risks due to construction practices that predate modern energy and air-sealing standards. Homes older than 30 years have unique challenges, especially those built before energy-efficiency standards were incorporated or modern construction guidelines were implemented. Older homes have more pathways for Radon to move more freely into the home from the ground. 

Foundations That Are Unsealed: 

Homes that were built decades ago usually have foundations that, let’s say, have more porosity, more cracks, and more jointed separations. 

Crawl Spaces Made of Loose Dirt or Gravel: 

Many older homes have unsealed crawl spaces and exposed earth, which provide large pathways for Radon to enter the living areas. 

Open Sump Pits and Floor Drains: 

Historically, empty sump pits and floor drains that lack trap seals allow soil gas to enter as direct chimneys.

Untreated Utility Penetrations:

Unsealed gaps around water, sewer, electrical, and furnace pipe penetrations through the foundation are avenues for soil gas.

Limited Vapour Barriers: 

Older homes have fewer sub-slab vapour barrier layers than current codes require for the vapour barrier, granular, and Radon control, allowing more Radon to move up through the house.

Radon Mitigation in Older Homes

When dealing with Radon exposure in older houses, it is often necessary to complete a full retrofit. This is unlike our new builds, which have convenient rough-in piping, so older houses are more complex. The most efficient and, in my opinion, the best means to do this is through Active Sub-Slab Depressurization (ASD), which consists of:

1.   Creating a Suction Pit: 

A small pit, about 10-20 litres, is excavated below the basement floor slab to access the soil gas.

2.   Construction of a PVC Pipe:

A sealed PVC pipe is placed in this pit, crosses the concrete slab, is normally positioned in a utility closet or garage, and is then ducted safely outside, preferably above the roof. 

3.   Inline Fan: 

An inline fan is placed in the pipe, usually in the attic or garage. This device continuously extracts soil gas from beneath the slab and diverts it to the outside. Thus, negative pressure is created beneath the foundation, preventing Radon from entering the house.

Apartment Dwellers and the Radon Issue

When thinking about the risk Radon poses, we tend to think of single-family homes, don’t we? However, the situation is different for Radon in apartments and other multi-unit residential buildings (MURBs), which pose all kinds of problems for property managers, building owners, and tenants, and Radon poses unique risks in multi-story buildings. The principle of Radon entering from the ground remains consistent, but the building's design changes fundamentally in how Radon can enter.

• Ground Floor vs. Upper Floors: 

However, that does not imply upper levels (floors) are safe. Upper levels (floors) are not safe from Radon exposure, as it may still reside in the building (lesser) and may creep through mechanical chases, elevator shafts, and building (shared) ventilation systems.  

•  Shared Foundations and Systems: 

MURB buildings share the same foundation. As a result, Radon released from the ground may affect multiple units. Shared ventilation, plumbing, and electrical systems provide a conduit for Radon to move freely between units, both vertically and horizontally.

• Building-Specific Ventilation: 

Radon movement can be greatly influenced by the pressure generated by the building’s ventilation system. A well-designed positive-pressure ventilation system may reduce or maintain Radon levels at low levels.

• Patterns in Occupancy: 

Compared with single-family homeowners, apartment renters may be less inclined to open their windows. This could increase the likelihood of indoor air stagnation and higher Radon levels.

Testing and Mitigation: Canadian Best Practices to Protect Your Home

The single greatest contributor to Radon risk for Canadians is a lack of proper testing and mitigation. This point applies to everyone involved with homes. From a single-occupant homeowner to a multi-unit building operator, across all types of construction and development. Understanding the risk and taking proper action is essential. 

Long-Term Testing (Minimum 91 Days): 

This testing method is tried and true. There is a significant potential for Radon levels to fluctuate daily or seasonally. It is best to conduct this test during the colder months, when the windows are closed. 

Test Location: 

Where the detector gets placed is important! It should be in the lowest area of the house where people sleep—think finished basements with bedrooms or living rooms—and away from any drafts, heat sources, or direct sunlight.

DIY Kits vs. Professionals: 

DIY kits are readily available at your local hardware store or online, and therefore much cheaper. These kits include an alpha track or an electret ion chamber, and therefore require extremely detailed and specific instructions to send the test to the lab for an accredited analysis. certified professionals handle the testing process, ensure it is properly placed, set up all data for the test, and complete all analyses.

Regulatory Landscape and Industry Impact in Canada

Radon-related laws in Canada affect multiple industries, including construction, real estate, and public health, as they shift toward a more protective and preventive paradigm. The laws influence everything from public health-focused Radon prevention in construction to health-centered real estate transactions. 

Health Canada’s Guiding Hand

Health Canada has a guideline for indoor Radon at 200 Bq/m³. Unfortunately, they must guide the provinces in forming laws to regulate this. Health Canada, however, is responsible for the Canadian National Radon Proficiency Program (C-NRPP) and accredits it. The C-NRPP certifies Radon measurement and Radon mitigation professionals. 

Improved Construction Regulations and Sustainable Structure Criteria

Although Passive House and Net-Zero homes use controlled ventilation and may worsen Radon levels because of their very air-tight design, future construction guidelines will focus on advanced Radon mitigation systems to ensure that energy-efficient construction does not compromise indoor air quality. Incorporating Radon mitigation into construction is also a current trend in green building certifications, such as LEED Canada. The construction industry is also seeing the development of Radon-resistant coatings (paint and sealants) that trap Radon within the structure.

Climate Change and Radon Dynamics  

The potential interactions between climate change and Radon are intriguing and worthy of study. Radon levels and climate change may be linked in different ways. Extreme weather (e.g., droughts and floods) alters soil moisture and, in turn, soil permeability and Radon's ability to enter buildings. Due to patterned ground (frost heave) resulting from an altered freeze-thaw cycle, the soil beneath buildings may become susceptible to Radon entry through foundations. More Canadians are trying to reduce their use of heating and cooling, which may increase the need for strong mechanical ventilation and Radon mitigation systems in their homes.

Public Understanding and Knowledge

Innovative and sustained public outreach efforts are essential if we want to normalize Radon testing and familiarize the public with it. The use of up-to-date accessibility resources, interactive maps, social media, and other digital tools will help streamline all of these efforts. Among other things, updated epidemiological studies will help clarify and refine the long-term impact of Radon on public health, even at minimal exposure levels. Similarly, studies focused on the duration, efficacy, and cost-effectiveness of different mitigation strategies (especially those applicable to larger, more complex multi-unit dwellings) will continue to support our best-practice standards.

Key Insights

• Radon is not an “old home” problem: There is a myth that only old, drafty homes are at risk. This is not true. Radon in new homes with modern, energy-efficient Radon mitigation systems, if implemented correctly, can be trapped more effectively than in homes built without systems, passive or otherwise.

• There is no substitute for testing: The only way to accurately assess Radon levels in a home is through testing. Testing is especially important because radioactive gas is both colorless and odorless. The guideline set by Health Canada is 200 Bq/m³; even though this standard is used, some risk remains, and therefore, testing should be done regularly.

Frequently Asked Questions

Is it true that every home in Canada, no matter where it is, has to be tested for Radon?

A lot of people think that Radon is only a problem in certain "hot spots" in Canada. Don't assume that just because your neighbour tested their home or the regional map shows low levels, you are safe. Your home could have even higher levels than your neighbour's.

New homes are constructed in compliance with the new Canadian building codes that require energy efficiency. Why should I be concerned about Radon in new homes?

This is one of the biggest misconceptions we face, and it is definitely true. Building modern envelope energy-efficient constructions is great for insulation and heating bills, but they also trap air in the house.

Future Trends: Design Improvements for Radon in Canada

The continued pervasive challenge of Radon gas in Canada illustrates the potential of emerging research, new technologies, and changing public attitudes in its management. New patterns will create both opportunities and challenges for policymakers, the construction industry, and the public, especially regarding Radon gas in new and existing homes. It is an ever-changing field, and I find it highly interesting. The rapid development of smart home technologies offers exciting new opportunities for improving Radon detection. The traditional long-term alpha-track detectors are still the gold standard for regulatory compliance. However, consumer-grade Continuous Radon Monitors (CRMs) are becoming more accurate and less expensive. These CRMs are integrated with smart home technologies and provide homeowners with real-time data and analysis.