10 Benefits of a Passive House

Can building just one passive house stop pollution or global warming? Sadly, no. But if even a small percentage of the new homes and buildings constructed in the United States and elsewhere were built to passive house standards, the energy savings would be significant.

A study conducted in Germany in 2003 compared the energy consumption of passive houses with the energy consumption of both conventional and energy-efficient homes and found that passive houses had an average energy savings of 90 percent over conventional homes and up to 80 percent compared with homes built to Germany's stringent low-energy construction standards [source: Passivhaus Institut].

Passive houses still use electricity for things like lighting, electronics and appliances, and heating water, but most require no heating source at all aside from the sun and the incidental heat generated by the appliances and people inside the house. By using energy-efficient appliances and alternative energy sources like solar panels or wind turbines, many passive house owners can power their homes with little or no reliance on the electric company or other polluting sources of energy.

Passive house design eliminates the need for traditional heating systems in even the most challenging climates, so bills for heating oil, natural gas or propane could become a thing of the past. Super-insulated construction and the use of energy-efficient appliances further reduce the energy footprint in a passive home. To be certified by the Passivhaus Institut, a passive house must consume less than 15 kilowatt-hours of electricity per square meter per year for heating and cooling, with total energy consumption for all heat, hot water and household electricity not to exceed 120 kilowatt-hours per square meter per year [source: Passivhaus Institut].

Dr. Gary Konkol, owner of the "Passive House in the Woods," a 1,940-square-foot (180.2 square-meter) passive house built in 2010 in Hudson, Wis., reported energy consumption of 679 kilowatt-hours for a 38-day period that included the cold and cloudy month of November 2010 [source: Hanson]. Even with the cloudy weather, a small solar array in the yard provided 366 kilowatt-hours of electricity, leaving just 313 kilowatt-hours to be purchased from the electric company. Total energy cost for 38 days: $35, which covered all heating, ventilation, hot water and household electricity [source: Eian].

While specific tax incentives vary from year to year and place to place, you may be eligible for a number of federal, state and local energy tax credits when you retrofit your existing home to passive house standards, or build a new energy-efficient home such as a passive house.

Some states, municipalities and utility companies also offer grants, rebates or low-interest loans to help you cover the cost of purchasing and installing new energy-efficient materials, appliances and structures. Web sites such as EnergySavvy.com and the Database of State Incentives for Renewables & Efficiency make it easy to search for the credits and rebates available in your area.

One of the most important elements of the passive house concept is controlled mechanical ventilation, which continuously replaces stale, humid or otherwise "polluted" indoor air with fresh, outdoor air [source: Passivhaus Institut].

In a passive house, high efficiency ventilation systems pull air from kitchens, bathrooms, and any other high-moisture or odor-producing spaces and pipes fresh air into bedrooms, great rooms and other living spaces. This balanced ventilation system keeps the humidity inside the home at a comfortable 30 to 60 percent [source: Passive House Institute US]. While the windows in a passive home can be opened just like the windows in any other house, homeowners may also choose to keep them closed, bringing all fresh air in through the filtered ventilation system and reducing exposure to dust and allergens.

The notion of comfort is so integral to the passive house concept that the Passivhaus Institut has gone so far as to apply a "comfort equation" to its building process [source: Feist]. Passive house design strives to maintain a comfortable, even temperature throughout the home, with low temperature variations from room to room. The difference between radiant temperature (i.e., the temperature of windows, doors and other surfaces) and air temperature remains small, helping to eliminate drafts.

High-performance windows and superior insulation also help to keep the inside of the passive house extremely quiet, and the steady ventilation eliminates odors and keeps the humidity within a comfortable range.

To meet the passive house certification standard established by the Passivhaus Institut, homes must be built to the best possible modern standards, making for a durable, well-built home. Because every aspect of the passive house is carefully planned and specified in advance, there is theoretically little room for error in the building process, and nothing is left to chance with regard to materials or construction. Many of the interior and exterior finish materials used in passive house design, such as the high-end windows and doors, are virtually maintenance-free, and the elimination of a furnace, boiler or other conventional HVAC system means that there are fewer "moving parts" to repair or maintain.

The high-performance windows and heavily insulated doors and walls in a passive home greatly reduce exposure to street noise and other outdoor sounds. Inside the house, Passivhaus Institut requirements specify that the efficiency of the central heat exchanger should be high, energy consumption of the fans should be low, the operational conditions should be clean and the unit should be very quiet [source: Feist].

In the Wisconsin "Passive House in the Woods," even the duct work itself helps reduce noise in the home. Flexible plastic air ducts are run directly to the ventilation system, without the need for duct tape or other joint adhesives, "making for a clean and quiet system, where noise cannot transfer from one room to the next through the ventilation ducts" [source: Eian].

While building a passive house doesn't necessarily mean going entirely "off the grid," many devotees of the passive house standard are quick to point out the benefits of decreasing our reliance on oil, coal or natural gas -- and the infrastructure that supplies them -- as we confront an uncertain energy future.

The low-energy consumption required by a passive house makes it easy to supply some or all of the household's electricity through clean, on-site power sources such as solar panels or wind turbines. Added bonus: You get to enjoy many of the benefits of an underground bunker without giving up fresh air, sunlight or a social life.

There's no question that the upfront cost to build a passive home is higher than the cost to build a conventional home, but over time, the higher initial price of materials, design and construction will be offset by savings on utility bills and home maintenance.

The Passive House Institute US estimates that an additional upfront investment of around 10 percent of the construction budget is required to achieve passive house standards, as compared to regular energy code-compliant 2x4 construction [source: Passive House Institute US]. In practice, the cost difference is often greater, but the price per square foot to build a passive house may be partially offset by the relatively small footprint of the home.

For example, The Shift House, a 1,741-square-foot (161.7 square-meter) passive home outside Portland, Ore., had a construction and design budget of $330,000, or approximately $190 per square foot. That's compared to an average cost of about between $200,000 and $282,000 ($85 and $120 per square foot) to build a conventional new home with an average size of 2,349 square feet (218.2 square meters) [source: Minervini]. But by spending an extra 10 percent during construction, Root Design Build (the project designers) expect to reduce the energy costs for heating by 90 percent indefinitely, and don't anticipate the annual heating bills to cost more than $200 [source: Minervini].

As of September 2010, there were just 13 certified passive structures in the United States, and the few passive homes in existence here have taken on near celebrity status among environmental enthusiasts [source: Zeller].

Roughly 2,000 visitors toured the Passive House in the Woods in the six weeks before it was first occupied by its owner in October 2010, and several of the passive homes built to date have been featured on green building Web sites, in newspaper articles, and in building and remodeling magazines [source: Eian].

Of course, even if you'd prefer not to have a few thousand of your closest friends traipsing through your house before you do, you'll be able to rest easy knowing that you're minimizing your impact on the environment even as you improve your own quality of life.