April 2, 2013 — The “Ruby House”, designed by Brach Design and located in the Avenues Historic District in downtown Salt Lake City, has been certified by the Passive House Institute United States (PHIUS), signifying that the home’s design and construction has met their rigorous standard for energy efficiency. It is only the second building in the state of Utah to achieve the certification, and one of about 60 nationwide.
The Passive House Standard is widely considered the most difficult and meaningful energy consumption certification because it requires a reduction in total energy use far below what is required by the building code or any other “green building” programs. In order to be certified, a building must stay below four key thresholds: one for heating energy, one for cooling energy, one for air-tightness, and one for total annual energy consumption (heating, cooling, hot water, lighting, and all miscellaneous electrical appliances). Computer energy modeling is necessary to make sure the process is based on sound building science, and although the concept is not applicable solely to residential buildings, the commercial market has been slow to adapt to the requirements of passive design. For more info on Passive House visit www.phaus.org and www.passivehouse.us.
“At first, I honestly did not think it was possible,” says architect Dave Brach in reference to the owners’ initial goal of designing their home to meet the criteria. “It is a very thin, sloping lot that is not ideal for winter solar gains, and because the design needed to satisfy the Salt Lake City Historic Landmark Commission, even an inefficient home would be challenging.” But the owners were steadfast in showing that it could be done, and Brach–who is a veteran Passive House designer–was up to the task.
A building that utilizes holistic and passive design principles integrats energy performance into the building design itself which allows the use of inexpensive, low-tech building elements to drastically cut mechanical heating and cooling. In short, Interior comfort is maintained without the carbon footprint.
The shell of the building, including all the doors and windows, is highly insulated and completely devoid of thermal bridges, which keeps the building warm in the winter and cool in the summer. Passive Buildings are necessarily air-tight, so warm air doesn’t leek out, cold air doesn’t blow in, and moisture stays out of the walls in winter, where it can condense and cause mold. This air-tight construction requires the use of a small ventilation system which provides and even steady flow of fresh air to the living spaces, while sucking out and exhausting all of the stale moist air out of the building.
Triple pane glass keeps the home super quiet, and proper window sizing and orientation ensures that the house is heated by the sun in the winter. The majority of space heat in a passive house is provided by the sun, and by incidental heat sources inside the home such as appliances and people. There is absolutely no need for a large and expensive geothermal heating system.
In Summertime, shading is the name of the game for passive building design. The harsh summer sun is blocked from entering the home, and natural ventilation, in conjunction with thermal mass, is used to flush unwanted heat out of the house at night. The small amount of mechanical cooling that is required for comfort can be provided with a very small point source air conditioner, or even just a few ceiling fans.