Many have heard of LEED Certification, a rating system created by the USGBC to distinguish high performance buildings. Now, up to version 3, the market popularity of LEED has grown internationally. In addition, it has evolved into several systems of certifications, for homes, commercial interiors, core & shell, new construction, schools, healthcare, retail, and existing building operations & maintenance, with a new pilot system for neighborhood developments. However, there are many other certification systems for buildings. While LEED is popular in the U.S., there are several in Europe that are growing in popularity, and now moving into the U.S. as well. The Passive House Energy Standard is one of them.
Passive House is based on the concept that energy conservation comes before producing energy. By insulating well, ensuring there are few sources for heat to leak from the building, and designing for the correct access to the sun, the certification indicates that the house can operate on very minimal energy per square foot. Heating and cooling can be economized given this well insulated building shell.
The Passive House Energy Standard comes out of Germany and is one of the most stringent certification systems today. Its energy criteria is 4.75 kBTU/SF per year for heating, which is about 90% less than typical space heating costs.
While it seems difficult to achieve this type of energy savings in a climate as cold as Minnesota's, Tim Eian of TE Studio, has just completed the Passive House in the Woods project, located on an acre of land in Hudson, Wisconsin, just 30 minutes outside of the Twin Cities. Through a well designed building shell, the house does not need a conventional furnace or boiler, even on the coldest days. The walls have an overall R-value of R-70, the roof R-95, and a floor slab of R-60. In addition to the high insulation values, given by Insulated Concrete Forms, polystyrene insulation, and polyisocyanurate insulation, the windows and doors are also high-performance. The houses uses Passive House certified windows and doors, which have a value of R-8. Compared to typical doors and windows, which can have anywhere from an R-2 to R-5, these triple pane windows have low-E coatings and frames designed to prevent thermal bridging. This translates to very little heat loss through the envelope of the house.
As mentioend earlier, the house does not need a typical mechanical heating system. In place of a boiler or furnace, the house only has a heat recovery ventilator, and a few electric heating mats in some rooms, with localized thermostats. These mats are only required for extremely cold weather, and use very little energy. For domestic hot water, 40 square feet of solar thermal panels pre-heat water, with an electric on-demand water heater to bring the temperature up.
The energy-efficient design also produces energy using solar photovoltaic panels. Given this particular house's energy conservation, the solar panels produce more electricity than the house consumes. Finally, the interior is finished off with materials that are low or no VOC, promoting healthy interior air quality.
The Passive House in the Woods project proves that the energy standard can be used in the extremely cold climates of Minnesota and Wisconsin. Even more exciting, in a recent presentation of the house, Eian indicated that the cost for construction was only about 20% more than a typical house of that size. Considering the long-term energy savings, and the durable construction and healthy interiors, the Passive House can be well worth the investment. For more information on the project, go to the Passive House in the Woods site http://www.passivehouseinthewoods.com/.
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