Radon Mitigation in Tight Homes: Why Every Mitigator Must Understand ASHRAE 62.2

Modern homes are becoming more energy efficient, with tighter building envelopes designed to reduce unwanted air leakage and energy loss. For radon professionals, however, tighter construction can make the relationship between radon control, building pressure, and indoor air quality more important.

An Active Soil Depressurization (ASD) system is designed primarily to control radon entry from beneath a building. Residential ventilation has a different role: providing controlled air exchange to support acceptable indoor air quality.

For professionals working on high-performance homes, understanding how these systems interact can help identify potential problems before they affect building performance. That’s why we created this CE course to help radon professionals understand when and how to use ventilation as a mitigation technique.

Check out our 4-hour, on-demand course, “ASHRAE 62.2 Ventilation Standards for Radon Mitigators,” available through the Ecosense Learning Center.

Why Tight Homes Require More Attention to Airflow

A tightly constructed home allows less uncontrolled air exchange with the outdoors. That can improve energy efficiency, but it also means that indoor air movement needs to be considered more deliberately.

Pressure inside a building can change because of weather, temperature differences, exhaust fans, combustion equipment, HVAC operation, and other mechanical systems. An ASD system adds another pressure-related factor by creating negative pressure beneath the building.

The important point is that radon mitigation and residential ventilation should not automatically be treated as the same function.

ASD and Ventilation Have Different Jobs

An ASD system works at the source. It creates a pressure field beneath the building and directs soil gas through a collection system so it can be exhausted outside.

A mechanical ventilation system addresses indoor air exchange. Depending on its design, it can introduce outdoor air, exhaust indoor air, or balance both processes.

ASHRAE identifies Standard 62.2 as the residential ventilation and indoor-air-quality standard for dwelling units, covering ventilation, local mechanical exhaust, and source-control measures. The current published edition is 62.2-2025, although the applicable edition can depend on the project and jurisdiction. 

An ASD fan should therefore not simply be assumed to satisfy a separate residential ventilation requirement.

Why Pressure Balance Matters

When a home is well sealed, unintended air leakage may provide less opportunity for pressure equalization.

Adding exhaust-driven equipment can change that balance. Depending on the building, this may affect combustion appliances, comfort, humidity, energy use, or the way air moves through the structure.

That does not mean an ASD system is inherently problematic in a tight home. It means the entire building should be considered rather than looking at radon mitigation as an isolated system.

A useful building-science approach is to consider:

• Building envelope tightness

• Existing exhaust equipment

• Combustion appliances

• HVAC operation

• Outdoor-air requirements

• Pressure relationships

• Measured ventilation airflow

This broader view can help professionals recognize situations where additional ventilation analysis may be appropriate.

Where Balanced Ventilation Can Help

Balanced systems such as heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs) are designed to exchange indoor and outdoor air while controlling the movement of air through the building.

Their role is different from ASD, but the systems can be considered together when evaluating a home's overall airflow strategy.

A properly designed balanced system can help reduce reliance on uncontrolled air leakage and provide a more predictable exchange of indoor and outdoor air. HRV and ERV systems can also recover energy from outgoing air, which can be useful in energy-efficient homes.

The actual system design should be based on the building, applicable requirements, climate, and measured conditions rather than assuming one ventilation approach works for every property.

What Radon Professionals Should Measure and Document

Modern mitigation work can involve more than selecting a fan and routing a discharge pipe.

Professionals working in new construction, energy retrofits, or tightly sealed homes may encounter projects where ventilation and indoor air quality need to be considered alongside radon control.

Useful information can include:

1. Existing mechanical ventilation equipment

2. Building characteristics and envelope conditions

3. Airflow measurements

4. Pressure relationships

5. Local exhaust systems

6. Applicable code or program requirements

7. Post-installation radon measurements

The goal is not simply to install equipment. It is to understand how the completed system performs within the building.

Build Your Ventilation Knowledge With Professional Training

For radon professionals who want more structured education, Ecosense offers an online course focused specifically on residential ventilation and radon mitigation.

The ASHRAE 62.2 Ventilation Standards for Radon Mitigators course is listed as a four-hour Radon CE Course and includes sessions covering ventilation and acceptable IAQ, dwelling-unit ventilation, fan sizing, local exhaust, installation, testing, and other requirements. The course page also identifies radon mitigators as its intended audience and provides a certificate of completion.

What the Course Covers

Professionals can explore topics including:

• Residential ventilation requirements

• Ventilation as a radon mitigation technique

• Fan sizing

• Local exhaust

• Installation considerations

• Performance testing

• Compliance requirements

This can be particularly relevant for mitigators working with new construction, energy-efficient homes, or projects where indoor air quality and building performance are important considerations.

Ready to expand your ventilation knowledge? Explore the ASHRAE 62.2 training for radon professionals

Final Thoughts

Tighter homes have changed the building environment in which many radon professionals work. Effective radon control still depends on understanding soil-gas entry and mitigation performance, but the wider building context also matters.

By developing stronger knowledge of airflow, pressure relationships, ventilation design, and indoor air quality, professionals can approach complex residential projects with a more complete understanding of how the building systems interact.

For mitigators who want to develop this knowledge through structured professional education, Ecosense's dedicated online training provides a practical starting point.

Frequently Asked Questions

1. Is the Ecosense ventilation course available online?

Yes. The course is provided through the Ecosense Learning Center, allowing professionals to access the training online rather than attending a traditional classroom session.

2. How long does the radon ventilation course take?

The course is currently listed with a duration of four hours. It is divided into multiple learning sessions and quizzes.

3. Who is the course intended for?

The course specifically lists radon mitigators as its audience. This makes it relevant to professionals who want education focused on the connection between residential ventilation and radon work rather than general HVAC training.

4. Does the course provide a certificate?

Yes. Ecosense currently lists a certificate of completion as part of the course information. Professionals should separately confirm whether the course satisfies the specific CE requirements of their credentialing organization or jurisdiction.

5. What topics are included in the training?

The listed curriculum includes ventilation and acceptable indoor air quality, dwelling-unit ventilation, fan sizing, local exhaust, installation, testing, and selected additional requirements.