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Passive Solar Design Data

Passive Solar Design Data

Design Objective

Here is some passive solar design data from a garage/workshop I built.  The design objective was to build a workshop/garage that is comfortable year round but has no heating or cooling bill.  To me, comfortable year round means: above 60F in the winter, and below 80F in the summer.  It is located in Albuquerque, New Mexico.

I designed the building using the book: “The Passive Solar House” by James Kachadorian, and “Passive Solar Design Strategies: Guidelines for Home Building” by the National Renewable Energy Laboratory.  I built excel spreadsheets to calculate heat gain and loss, and had an architect review my design and suggest improvements.

Winter Heating Design

There are three 3 ft x 6 ft windows in the south facing wall to heat the 16 ft x 20 ft building in the winter.  In the winter the sun shines on the concrete floor where the radiant energy is stored and continually warms the garage.

To keep the heat in at night, on the inside of the windows, I plan to put 2” Styrofoam doors that close at night using a timer or light sensor.  The walls are stucco and 2x6 construction with R-19 insulation.  The ceiling is 2x12 construction with R-30 insulation.  The garage door is 2x4 construction with R-13 insulation.  Heat wants to flow out (not down) from the foundation to the cold surface of the earth in the winter.  There is 2 inches of Styrofoam, 2 ft deep around the foundation to slow this heat flow.

Summer Cooling Design

There is an overhang on the south wall.  It allows 8 weeks of full sun through the windows in the winter, and 8 weeks of full shade in the summer.  Here’s a link to the overhang specs from the New Mexico Solar Energy Association (PDF).  There is also a deciduous tree near the southwest corner of the building.

The ceiling is 9 ft on one side 8 ft on the other side.  On the high side there are vents with fans on timers.  They blow warm air out of the building after midnight.  There are vents near the floor on the other side of the building, so the cool night air is drawn in, flows across the concrete, and cools it.  The slab helps keep the building cool during the day.

Actual Temperature Data

I did not have the building insulated last winter (January 2009) so I don’t have winter data yet.  During the hottest part of this summer (late July and early August), overnight lows were near 70F and daytime highs were about 95F.  Inside the extremes were about 74F at sunrise and 82F at sunset.

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