California's First Passive House Remodel

Imagine a house that can reduce energy consumption by as much as 90% without using solar panels or other expensive equipment.

hat is the definition of a “passive house,” and a home in California is in the process of being remodeled into one. It will be the first California house being remodeled to meet Passive House Institute standards.

Passive houses are airtight and constructed to retain as much "free" heat created inside of a house as possible.

The concept mostly dispenses with conventional HVAC systems in favor of a heat exchanger that uses heat generated from its occupants, appliances, electronic devices, pets, etc. to warm fresh air coming in from outside –then the air is circulated through vents. The ventilator has a fan that sucks fresh outside air through ducts into the bedrooms and living room and another fan that sucks moist or smelly air out of ducts in the kitchen and bathrooms. In the process, heat is exchanged so it does not leave the house.

Absolute airtightness is essential –and works in combination with insulation, optimal solar orientation, shading, a well-balanced ventilation system, and energy-efficient appliances and lighting fixtures. The proportions of different elements need to be carefully balanced and natural light needs to be used effectively. Windows are triple-paned to increase passive solar gain.

The California home, a single-family one-story structure located on a 73.5- by 100-foot lot in Sonoma, will retain its original foundation and about 40% of its walls, says Graham Irwin, a principal with Essential Habitat in Fairfax, California., and a certified Passive House consultant. He’s working on this project with builder Rick Milburn, who owns Solar Knights Construction in Napa; and Jarrod Denton, an architect with Lail Design Group in St. Helena, California.

The 2,400-square-foot house, built in the 1960s, will soon start a precertification process that involves a series of air-exchange tests. The project is on target to be finished by July..

Passive house construction has been used for 20 years in Europe, but only recently has been introduced in the United States. There are now about 15,000 passive houses globally.

The Sonoma house’s costs were about 10% higher compared to a traditional remodeling project, but should quickly recoup that investment through energy cost savings. In Europe, costs are only 1% to 4% higher since building materials that meet Passive House Institute standards are more plentiful.

Denton admits that he was initially skeptical about building to Passive House Institute’s performance levels. “When I read the requirement of 0.6 air exchanges per hour at 50 Pascals, I thought it was a typo,“ Remodeling.net quotes him as saying. “But that’s also what’s most impressed me about this construction.” The Passive House standards far surpass the LEED standards established by the U.S. Green Building Council.

The supplemental HVAC source for the Sonoma home is an air-to-water heat exchange that works in tandem with an energy recovery ventilator. There is also a small backup cooling system. At peak, these systems will need to generate only 6,800 BTUs per hour of heat and less than 4,000 BTUs per hour of cool air. “These are incredibly small [systems]; less than half a ton,” says Irwin.

The partners also believe that building and remodeling to Passive House standards might be the most practical way for California to achieve its mandated goal of reducing its greenhouse gas emissions to 1999 levels by 2020, and for all new residential buildings to be net zero energy by 2020. Solar panels can be found on houses all over California, but a 1,500-square-foot house would need 1,300-square-feet of PV panels to meet its energy demands. Remodeling homes into passive houses could be all that is needed.