Cranking up the heater or throwing on an extra sweater are two ways to cope

with a drafty house that allows chilly air to seep in through cracks, doors

and windows.

When the sun blazes in the summer, that same house warms up rapidly,

prompting people who live there to close the shades or drapes, pour an icy

beverage and possibly flip on an air-circulating fan.

A new concept in energy efficiency, known as the ''passive house,'' sets

specific standards for designing a home that reduces -- or completely

eliminates -- the need for a furnace or air conditioner. The home is

constructed to be super energy-efficient and to regulate air temperature in a

''passive'' manner.

An airtight structure adhering to passive house guidelines could reduce

year-round energy costs by an estimated 80 percent.

It's been described as working like a sealed envelope or thermos bottle,

preserving hot and cold equally effectively. Heat generated by appliances,

bathing and the body itself are factored into calculations.

Accordingly, a house that's vacant most of the day would generate less heat

than one where occupants are using computers, TVs and kitchen and laundry


More than 10,000 passive houses have been built in Europe since the design

approach was introduced in Germany in the early 1990s. But only a handful have

been constructed in the United States.

Early advocate

Petaluma-based architect Bill Wolpert, principal of Green Building

Architects, has been interested in creating energy-efficient structures since

he was a student at Cal Poly San Luis Obispo in the 1970s.

Early in Wolpert's career, when gas, electricity and water costs were low,

energy efficiency wasn't a top priority. But now, most clients want buildings

that make abundant use of solar energy, have well-insulated walls, doors and

windows, conserve water and are constructed with recycled and/or nontoxic


Last year, Wolpert attended a lecture by Berkeley architect Nabih Tahan, a

passive house pioneer in California, and afterward asked two of his

residential clients in Sonoma County if they wanted to incorporate passive

house standards into their project, even though the design was nearing


The first certified passive house in the United States was built in Urbana,

Ill., in 2003 by German architect Katrin Klingenberg, who established the

Passive House Institute US. In January 2008, it was established as the

official certifying body in North America by the the Passivhaus Institut in

Darmstadt, Germany.

Passive house building techniques include use of the latest construction

materials, such as multipane windows containing a thin metallic film, argon

gas and a layer of mylar film, to create an insulating ''sandwich.''

A special feature is a central ventilation system with warm air moving

through it alongside cold air coming in from the outside. This heat exchange

is considered to be 90 percent efficient. An ''energy recovery ventilator''

provides a constant supply of fresh, filtered air and creates good interior

air quality while maintaining a comfortable temperature.

Previous efforts to create airtight construction have resulted in problems

with mildew and mold, Wolpert said.

Another key design consideration is positioning a house to take advantage

of maximum sun exposure.

Scrapping the dome

Wolpert's clients, Chris Read and Chris Vein, are San Francisco residents

who spend weekends on a seven-acre, oak-studded property with stunning views

above Sonoma.

They knew when they purchased their 30-year-old geodesic dome residence

three years ago it would need remodeling, but as they began investigating

improvements, the men realized it would be easier to scrap the dome and design

a modern home that could be smaller, energy-efficient and take full advantage

of the site.

''Our goal was not to be a super-green client. But we'd like to do as much

as we can to reduce energy consumption," Chris Read said. ''We're into

balancing the practical with the (passive house) standard itself.''

They agreed with Wolpert's suggestion to hire energy consultant Graham

Irwin of Remodel Guidance in Fairfax to do a detailed energy analysis using

computer software from the Passive House Institute US. Irwin, who is certified

by the institute, found some design elements were fine, but others could be

improved, such as changing window locations to allow more air flow and

choosing ultra-thick insulation for the walls.

Wolpert also used software showing where the sun and its shadow would fall

on the house from dawn to dusk, resulting in useful information about

positioning windows.

While Wolpert and his clients haven't finalized the plans and building

materials, they acknowledge it will be a home in the passive house spirit even

if it might not meet the exact energy usage criteria for certification.

''We're getting something that makes us feel better about the energy we do

have to burn,'' Read said, noting that the house will have a floor radiant

heating system and will use materials from the deconstructed dome and salvage


Typical home leaky

Many communities have voluntary standards for green building, but lack

specific thresholds for carbon output and energy performance. Following

passage in 2006 of Assembly Bill 32, the California Global Warming Solutions

Act, municipalities are looking at numerous ways to reduce greenhouse gas

emissions, including guidelines for energy consumption in remodels and new

home construction.

''A typical home in California leaks 30 percent of air to the outside. It

has to do with standard of work. A lot of problems in existing homes are the

fault of the craftsmanship,'' Wolpert said.

If Read and Vein agree to the recommended window and insulation changes to

boost energy efficiency, he believes the radiant floor heating they're

planning could make the house too hot. He hasn't suggested, however, that they

construct it with no heat source.

''The passive house idea wasn't on my radar until two years ago. This way

of doing things is a little different,'' Wolpert said. ''It if works in

Germany, there's no reason it wouldn't work here. We have the ideal climate.''

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