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Passive Solar Designs

The first thing you notice about a passive solar house is that it’s easy to tell which side of the house you’re looking out, whether the sun is out or not. There are lots of windows on the south side, which opens up to the outside world to maximize exposure to the sun, while the north side has just a few, smaller windows to keep the winter cold outside. An awareness of the site the house occupies is a part of its basic design. Compare this to a conventional house, where it’s almost impossible to tell which side of the house faces south—unless the sun is out. These houses are indifferent to the site they inhabit, which means they require more resources to maintain have to work harder to maintain indoor comfort levels.

Passive solar design helps us limit a home's lifetime impact on the local ecology and minimize heating and cooling costs. By designing with a keen awareness of the sun's path and the local climate we are able to improve the quality of natural daylight inside the house and greatly reduce the external energy inputs needed to maintain a comfortable indoor temperature year round. That means much less oil or gas coming out of the ground or less wood coming out of the forest. Passive solar design has four main components: solar orientation, glazing to floor area ratios, insulation and thermal mass. Each is essential, and the four work together.

Passive solar homes are also much more comfortable for the people living inside than conventional buildings are. Solar heat feels better than any other kind on the human body. And solar heat stored in the abundant thermal mass of our floor system means that the indoor temperature remains relatively constant during both daily cycles of day/night and longer seasonal cycles. A passive solar home tends to stay warm in winter and cool in summer, without expensive mechanical heating systems.

Orienting a building's longer side to within ten degrees of solar south allows us to take full advantage of the sun's light and heat. Sizing and positioning the windows on each side of the house according to careful calculations maximizes heat gain and minimizes overnight heat loss--the most important factors in our cold northern climate. Adequate thermal mass properly positioned to absorb the sun's heat allows us to store it during the day and then slowly release it once the sun goes down. Earthen floors are great for this. Finally, abundant insulation in the walls and ceiling, and double-paned windows ensure that most of the heat gained during the day will stay inside the building. For our walls and ceilings, we combine the timber frame structure with a lightweight truss system that allows us to achieve R-38 for the walls and R-60 for the ceiling, while all but eliminating thermal breaks.

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