Lessons from a passive house
A passive house is cutting edge, but the lessons learned can be applied to all existing homes. These tips come from the Minnesota Pollution Control Agency:
Address energy efficiency first.In every home, heat is lost through the shell of the building. Passive house dramatically reduces that loss by using super-insulated walls and highly efficient windows that prevent the transfer of heat and cold between inside and outside, paying special attention to penetrations and joints. Only the most efficient appliances, electronics and lighting are used in a passive house. Every home, however, can have its air leaks sealed, insulation added, and lighting and appliances updated to become more energy efficient and meet the Passive House retrofit standards.
Use passive design strategies.Energy from the sun is used to heat the passive house. Specialized windows allow for optimal solar heat gain and retention. Large, super-insulated, air tight windows are located on the south to catch the winter sun, while windows are smaller on other sides of the house to reduce overheating and minimize heat loss. Every house can use shading devices, window films and the solar-heat-gain-co-efficient (SHGC) of windows to allow in, or keep out, heat from the sun, specifically tailored to the direction each window faces.
Find heat sources in unexpected places. Since the passive house is so well insulated, it can be heated by all the things inside a house that generate heat, including people, pets, household appliances, computers, TVs, other electronics and lights. When these sources are combined with passive heat from the sun, the house has no need for a furnace. Every household can remember to power off computers, TVs, other electronics and lights when not being used, especially in the summer to reduce AC loads.
Combine air-tightness with continuous ventilation.A passive house needs to retain a great percentage of all the heat (in the winter) and coolness (in the summer) that are passively captured. To do this, the building envelope is built much more air-tight than average construction. However, to keep the air quality fresh, ventilation allows Passive Houses to have some of the best air quality measured in buildings. Every house can use a combination of passive ventilation from windows and active ventilation from bathroom/kitchen fans or a heat recovery ventilator (HRV) to improve indoor air quality.
Use cooling concepts for your region.Architecture of the region usually includes strategies for cooling, such as shading from a screen porch, deciduous trees species, night ventilation and other such strategies. In a passive house, these elements are carefully modeled and designed to use their full advantage. The passive house has only 2 percent overheating above the desired temperature over the course of the year.
Consider renewable energy. A passive house does not need to have renewable energy, but including relatively small solar hot water, solar photovoltaic (PV), and earth loop systems can make a passive house totally energy independent. The passive house on display featured a solar thermal panel for hot water. Heating water accounts for 14 percent of the energy your home uses. Using less hot water, and heating hot water with the sun, saves energy in every home. Our passive house is also displaying a small earth loop used to pre-temper the fresh air coming into the house.
Use reused, repurposed and recyclable materials.This home features reused wood siding from an old barn. Reusing building materials extends the life of the product and prevents the use of new materials. Wood siding also is renewable. Other materials were repurposed for building, such as the use of wine bottles as aggregate in the concrete panels and the use of coffee jute sacks as screens and guardrail material.
For more information, see our Building a Green Home research center.