Case Study # 3


Clean Air Crawl Space Energy

San Carlos California

 Fall 2011

The “health” needs of the owner inspired the renovation of their 1930’s single story 1700 s.f.  Californian Bungalow. These health issues wer the result of bad crawl space air quality caused by the presence of mold spores, fungus, decay, elevated radon levels, asbestos deterioration, termite, and other health concerns. These contaminants were infiltrating into the cavity of the occupied envelope of the home, from the crawl space, and were contributing to the health decline of our client. To solve the air quality issues, we had to seal up the building envelope and introduce “Mechanical Fresh air Ventilation”. We used a “Continuous Whole Building Ventilation” system, incorporating a heat recovery ventilator (HRV), which jointly harnesses the Earth’s natural thermal energy, in this damp, musty, temperate, crawl space.

The home retrofit consisted of encapsulating the crawl space, sealing of the existing HVAC plenum & ducting, andair sealing” the building shell. The result was an isolated and reasonably air tight living envelope. The HRV transfers the majority of the stale, indoor air temperature to the incoming fresh air, maintaining the temperature of the building. 

Our solution established a positive air pressure in the occupied envelope, forcing shell contaminants to the exterior of the 80 year old framing. By sealing off of common envelope components, and creating a negative pressure management system within the crawl space, we prevent infiltration into the living envelope. This negative air pressure meets the intent of the ASHRAE Standard 62.2  for “Ventilation and Acceptable Indoor Air Quality in Residential Buildings”.

By utility monitoring before and after this system, our goal, in addition to this system improving the air quality and health of the building’s occupants, is to make our integral heating and cooling system, a “passive / hybrid” / geo-exchange system, eligible for the geo-thermal 30% federal tax credit, by illustrating with data, how much this system can reduce the energy consumption of our homes.   

Left to right: "Team"

James Wright Energy Architect, Barry Stephens sales Rep Zehnder America, Matt Groves Engineer Zehnder America, Hahns senior engineer Zehnder Germany