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Collect solar energy for heat storage and re-distribution using exterior shading geometries, windows, floor, wall and roof surfaces.

Direct gain systems capture solar radiation through south-facing glazing during winter months with thermal mass (floors) and block solar radiation during summer months via shading and landscaping. Indirect gain systems use thermal storage walls and thermal storage roofs to collect heat and then slowly radiate heat throughout the interior space. Isolated gain systems use a solar collector to collect heat and then transfer heat via convection to a storage unit. Interior space is than heated via convection from the storage unit.

Solar energy is collected through properly-oriented, south-facing windows and stored within “thermal mass,” comprised of building materials with high heat storage capacity such as concrete slabs, brick walls, or tile floors. The thermal mass components then distribute the stored solar energy back to the living space through the mechanisms of natural convection and radiation.
To obtain the maximum amount of heat, specify south-facing glazing with a high solar heat gain coefficient. Also, use summer and winter sun angles to calculate optimum shading design to allow direct solar gain to hit the building facade in the winter while blocking it during the summer.

Passive solar systems do not have a high initial cost or long-term payback period, both of which are common with many active solar heating systems. Modest usage can reduce heating requirements by 5 to 25 percent; aggressive usage can reduce heating by 25 to 75 percent.

Passive solar heating tends to work best and be most economical in climates with clear skies during the winter heating season.
Use passive solar heating strategies only when they are appropriate. Passive solar heating works best in smaller buildings where the envelope design controls the energy demand.

South-facing! Best for climatically controllable spaces such as small buildings or components of large buildings (i.e. non-heated winter gardens of residential units). Careful attention should be paid to constructing a durable, energy-conserving building envelope. Reduce air infiltration (insulation before insolation). Make sure there is an adequate quantity of thermal mass

1.1.3 Building Orientation
1.4.1 Solar Heat Gain Coefficient
1.4.4 Exterior Solar Shading
1.5.3 Commissioning
1.7.5 Fabric Energy Storage