Case Study Home # 5
Continuous Whole Building Ventilation
Geo-Exchange Crawl Space Energy

Alamo, California

The purpose of this study is to establish the Earth’s thermal energy contribution to the home, by documenting the energy performance when fresh air ventilation systems are incorporated.

The 1980’s one story 7,000 s.f. Mediterranean residence, with 6,500 sf crawl space has been renovated with “Passive House” techniques incorporating a Mechanically Ventilated Crawl space, “Continuous Whole Building Ventilation,” and air sealing the building envelope for indoor air quality code requirements. The home had been gutted to the framing and fully air sealed with spray foam at the roof, rafters, walls, and crawl space rim joists. A radiant barrier insulative plywood was used for the roof framing, and the attic space is now ventilated as part of the conditioned home. We replaced the existing network of ducting, sealed up the exterior crawl space vents, insulated the skirt walls, and installed a continuous ground vapor retardant barrier for code compliance.

We have two separate HRV units which will operate independently, but will be linked together for seasonal energy transfer only. One for the crawl space and the other for the living space. The contained energy of the crawl space will now create a geo-thermal “buffer space” between the home’s conditioned space, and the outdoors. The HRV maintains the geo-thermal advantages of the crawl space, while the other assists the heating and cooling of the home. In the peak heating and cooling season, the conditioned crawl space’s stale air pre-conditions the main house HRV’s fresh air, using the crawls space energy for cooling in the summer and heating in the winter. In addition to the thermal benefits, the separate system will improve the air quality and health of the building’s occupants, due to the negative air pressure created in the crawl space. Our systems now jointly harnesses the Earth’s natural “Geo-Solar” energy in this  temperate crawl space.

For this study, we are monitoring the utility load in comparison to the load prior to the encapsulation and mechanical modification.  We will compare this data to the new results after each season. Our goal is to make our mechanical system, a “passive / hybrid” / geo-exchange heating and cooling system, eligible for the geo-thermal federal 30% tax credit, by proving how much they can reduce the energy consumption of our homes.      


FreeWatt HVAC Cogeneration System