In Greenwich, we worked with a homeowner during a major home addition project to plan long-term radon protection across a complex multi-foundation property.

The home includes five separate foundation sections along with significant ledge conditions beneath portions of the structure, creating a more advanced airflow environment that required careful phased planning for future radon mitigation improvements.

As part of the new construction project, the homeowners recently completed insulation work within portions of the crawl space areas while additional framing and foundation work continued throughout the addition.

The initial phase of the project focused on two crawl spaces — an existing 30x15 crawl space beneath the original foundation and a newly constructed 20x8 crawl space area being prepared ahead of the slab pour for the addition.

For the new crawl space section, perforated PVC piping and encapsulation materials were planned beneath the slab area before the concrete pour to establish the foundation for a future passive radon mitigation system. This early preparation allows the homeowners to preserve future mitigation flexibility while construction access remains open.

The long-term mitigation discussion also included a larger five-point system strategy for the entire property once the addition and renovation work are fully completed.

At this stage, the homeowners elected to begin with crawl space encapsulation and passive system preparation first, with additional radon testing and potential active system expansion planned after the renovation project is completed.

The project focused on integrating long-term radon planning directly into the construction process to improve future indoor air quality options while minimizing disruption later in the build.

In Greenwich, we evaluated a historic home built around 1920 where radon levels tested at 5.0 pCi/L across a complex foundation layout that includes one main foundation area and two crawl spaces.

Because the home features older field stone foundation construction, the mitigation strategy required careful planning to improve airflow beneath multiple sections of the structure while working within the existing foundation conditions.

A three-pipe radon mitigation system was designed to provide broader airflow coverage beneath both crawl spaces and the primary foundation area. The vent routing is planned along the right side of the home behind the chimney to maintain a cleaner exterior appearance.

The home also includes a sump pump and perimeter water management system, both of which were reviewed as part of the mitigation planning process.

During the consultation, an existing ERV ventilation system was discussed after the homeowner noted limited improvement in overall indoor air quality performance. Additional foundation sealing work was also identified, including sealing a crack near the washer and dryer area around existing plumbing penetrations.

The project focused on improving sub-slab airflow, strengthening foundation sealing, and addressing the unique challenges that often come with older field stone construction.

In Greenwich, we evaluated a home built around 1960 after radon levels tested at 7.35 pCi/L shortly after the homeowners moved into the property.

The basement is currently under renovation, with the lower level opened up for construction work. This created an ideal opportunity to address radon mitigation and foundation sealing improvements before the basement is finished.

The home includes two sump pump systems with existing covers that require additional sealing improvements to help reduce potential radon entry beneath the slab. The basement also includes a perimeter water management system that will require sealing as part of the overall mitigation strategy.

A one-pipe radon mitigation system was designed with venting planned along the right side of the home to improve airflow beneath the foundation and support long-term indoor air quality improvements.

In addition to the mitigation system installation, approximately 98 feet of foundation and perimeter sealing work was identified to strengthen airflow control beneath the basement slab and around the water management system.

In Greenwich, we evaluated a home with radon levels testing at 6.4 pCi/L where the structure is primarily built on slab construction with one smaller foundation section.

Because the home does not include a crawl space beneath the structure and does not use radiant heat within the slab, the mitigation approach focused on exterior system placement and strategic extraction point locations to improve airflow beneath the home.

The primary design included a two-pipe mitigation system installed along the exterior near the AC units. The layout required exploratory access points to better understand the slab and foundation configuration before final extraction placement.

A secondary mitigation option was also discussed that would utilize a single extraction point positioned near the master bedroom area if field conditions required an alternate approach.

The planned extraction locations include one point near the bedroom section of the home and another beneath the window area within the original foundation section. The system design also includes a muffler to help reduce operational sound and maintain quieter performance near the living spaces.

Existing exterior electrical access is available for the fan installation, and ABS piping was selected as part of the proposed exterior routing design.

In Greenwich, we worked on a property with multiple structures, including a main home with an existing passive radon system and a separate indoor pool area without passive mitigation in place.

To improve performance in the main home, a radon fan was added in the attic to convert the existing passive setup into an active mitigation system. The attic area included extensive spray foam insulation, requiring careful planning for fan placement and pipe routing.

The upgrade was designed to improve airflow beneath the foundation and provide more consistent radon reduction while utilizing the existing passive piping already installed in the home.

A post-mitigation radon test kit was also left behind so updated levels can be monitored after the fan installation.

In Greenwich, we returned to a home where the radon level tested at 6.0 pCi/L. The property has four separate foundation areas, with an existing mitigation system already in place for one section.

We previously replaced the fan earlier this year, and the homeowner has been monitoring radon levels since then. Based on those results, the decision was made to expand the system to improve coverage.

Two additional extraction points were added—one in the crawl space and another in a closet—bringing the system to cover three of the four foundation areas. This approach allows the homeowner to address the most active sections first and evaluate whether the fourth area will need to be included later.

The system is now better aligned with the layout of the home, providing broader coverage while allowing flexibility for future adjustments if needed.