Case Study Home # 1

Geo-Solar Thermal Storage Crawl Space Energy

Lafayette, California 

The purpose of this study is to establish the Earth’s ambient / passive geo-exchange energy contribution, by documenting the performance of a home with the crawl space sealed off from exterior ventilation during the cooling and heating season. In addition, energy will be saved, because of the reduction of building envelope heat gain  / loss, which is equivalent to the area of the home’s foot print.

Method One:   The least expensive is to provide air change through an air to air heat exchanger called an Energy Recovery Ventilator (ERV). This will transfer a majority of the incoming fresh air temperature to the exiting exhaust air, while maintaining the air temperature in the crawl space during ventilation. The result will be an ambient / passive geo-exchange. Interpretation of the  local code would be required.

Method Two:   The permanent way, which is the most energy efficient and International Code compliant, is to encapsulate from moisture and air infiltration. When combined with the homes mechanical HVAC system, proper insulated, you will create an energy source of passive / geo-exchange.

The challenges are the air tightness of the cavity being used as an air return / plenum. In general, we need to insulate with spray foam at the rim / floor joist, and the seams of the rigid insulation in the wall framing above the concrete foundation where the encapsulation typically terminates.  The spray foam should overlap and seal the encapsulation membrane.

The crawl space has been encapsulated from moisture and air infiltration, meeting code requirement of an approved continuous vapor retarder for mechanically ventilated crawl spaces.

For this study, we will monitor 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 the cooling season is over.

My goal is to becoming eligible for the geo-thermal federal tax credit, by documenting the energy reduction to qualify as a “passive” / geo-exchange heating and cooling system.