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Swall Institute -> Design Solution

Heating & Cooling
Active Solar Heating:
Solar water panels are one of the cheapest ways to capture free energy from the sun. We use this system to heat both the domestic hot water and the radiant floor heating. Radiant floor heating is that it adds important thermal mass to the floor (see Passive Solar Design).
The design of the solar heating system was done by Peter Millar (Building Energy Solutions, Reno, NV). Steve Cupp (The Energy Source in Bishop, CA: 760-873-6165) was an amazing local resource for used solar parts and system installation.

To power 80% of our Domestic Hot Water (DHW) and Space Heating (SH) needs, we installed five 4ft. x. 8ft solar collector panels (160ft2) and two 120gal storage tanks (1.5*160ft2). We "staged" the two tanks so that all the solar energy goes to heat one tank first, then when it is hot, the other tank is heated. This staging has two benefits: One is that on a cloudy day you can at least count on one 120gal tank with hot water. The second is that the hot water will recharge faster. The basic concept is that 120gal of hot water is more useful than 240gal of luke warm water.

Since our biggest demand for solar heating is in the winter, we positioned the solar panels at a 60 degree angle to maximize winter gain. We used this great solar angle calculator: Sun Angle Calculator.

Backup Heating:
Backup heat for both the domestic hot water and the radiant floor system are provided by a high efficiency condensing propane boiler (Knight Boiler)

Cooling in the summer is achieved simply by:
1) optimal placement of windows and overhangs
2) thermal mass in the floor
3) well insulated and tight envelope
4) a ceiling fan, and
5) cross ventilation

The effectiveness of these is maximized by "night venting." This means opening the windows at night and closing them during the day. Daytime ventillation with hot air will only heat, rather than cool, the house. To see the effect of night venting, check out this simulation.