- Homes built since the 1980s
Frequently have a gravel bed under the concrete slabs, which creates a great opportunity for air flow. System design in these homes is almost exclusively aesthetics and the fan choice is a very energy efficient, lower suction fan.
- Homes built before the 1970s
Likely these have slabs poured directly onto the soil, frequently compacted soil, or clay, which may lead to decreased airflow and special mitigation considerations. These special needs have a larger effect on system design and may benefit from the use of a high suction fan.
- Slab areas greater than 2,000 + sq feet.
These homes may require special design considerations, and system design may include or combine, larger piping, multiple penetrations or multiple systems. Fan selection is based upon both the pressure field extension and sub-slab materials.
More often than not, proper mitigation will require addressing the whole building. If the home has more than one foundation type or level, (or crawl space) the system design may need to incorporate the full slab with additional pipe extensions into other slab areas.