Passive Solar Design

Passive Solar Principles

The bath tub area is set in a bump-out area, surrounded by five windows. We used a special tool to calculate the overhang of the roof for different solar angle projections at different times of the year. In the summer, there is shade. In the winter time there is abundant sunlight and warmth filling the entire room. The surrounding slate tiles help to capture the heat.

 

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Eco-Cottage: Slate roof installed

100_6859Slate roofs are by far the best choice, as long as the supporting structure has been planned to handle the extra weight. Slate is beautiful, durable, and ecologically sustainable.

100_6866Yes, slate is an expensive material to purchase, time-consuming and expensive to install, but a slate roof will last for a century and more with proper maintenance. Considering the long-term value of slate, it is probably the least expensive choice for your roof.  An asphalt roof will need to be replaced every ten to twenty years, but your slate roof will only require minimal maintenance every twenty years or so.

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Thermo Siphon

A thermo-siphon solar heater installed on the southern wall of a building can be used to provide heat on most days. This is recommended for workshops or other out buildings that are used mostly in the day time. On this project, we used old skylights that had been removed from a building because they leaked. (There are lots of rejected leaky skylights available on craigslist.org!) We put aluminum studs in between the glass and wall board to act as absorber plates and painted everything black. With cement board over this we added thermal mass and lateral bracing. Cold air from the interior moves into the panel from a low vent, heats up inside the panel and exits the panel into the room as warm air. On a 40 degree day, the air coming out of the heater is around 90 degrees. Free heat.

In the summertime the southern side of this building is in complete shade from a cotton wood tree.

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Greenhouse

100_1811Passive Solar Design  can capture the sun’s energy and store the heat in a earthen or stone floor.

A greenhouse can be added to your house as a passive solar heater. During the coldest days of the winter, a greenhouse will stay 15 to 25 degrees warmer than the outside at night.  On a clear cold day it will heat up to 80 degrees if it’s 30 outside. During the spring and fall, a greenhouse makes a very pleasant sitting room.  During the summer, the roof vents should be opened and the roof  covered with deciduous vines or bamboo screen to make a nice well-ventilated, shady area.