Design considerations concerning passive solar heating are invaluable for a designer. This is because they help designers use passive solar heating technologies correctly and efficiently.
In addition, the design considerations serve as general guidance to help engineers and designers make the right decisions about the various design aspects of the passive solar heating system. For instance, building orientation, placement of different rooms based on their functions, provision of suitable size and number of windows and doors, envelope type selection, sealers, shading, etc.
What are the Design Considerations for Passive Solar Heating System?
- Specify the orientation of the building during site planning, and protect openings from prevailing winter winds.
- Organize living or working space on the south side of the building and less frequently utilized areas like bathrooms on the north side.
- Design the building to avoid sun glare; for instance, plan rooms and furniture layouts of the house to prevent glare from the sun on computers, televisions, and other equipment.
- If possible, extend the building along the east-west axis to increase the south-facing elevation and increase the number of south-facing windows.
- Determine glazing amount based on climate and building type.
- Choose windows with low thermal transmittance values (U values) but high solar heat gain coefficient (SHGC), i.e., use a window that admits ample amount of solar radiation into the house. It is recommended to consult National Fenestration Rating Council’s Certified Products Directory for tested performance.
- Enhance the performance of the building by using either high-performance, low-E glazing, or moveable insulation to minimize heat loss from the glass at night.
- Passive solar glazing of passive solar building should face true south or within 30 degrees of true south, and not be shaded by obstructions like buildings or trees, to have full exposure to the sun from 9 am to 3 pm for ultimate solar heat gain during winter.
- The south-facing glass should not lead to an increase in the cost of house cooling during summer. In many regions, shading in summer is as important as admitting solar energy into the house in winter. Therefore, the designer should use the sun’s summer and winter angles to compute optimal overhang for windows, see Figure-1. This ensures adequate solar heat energy gain during winter and provides suitable shading during summer.
- Provide air-tight seal around doors, electrical outlets, and windows on the exterior wall.
- Prevent overheating in hot climates by minimizing west and east-facing windows and using proper shading elements. Overheating can increase the cooling cost for large buildings with great internal heat gain.
- Ensure the provision of natural light to every room in the building.
- Provide an adequate amount of thermal mass. It could be challenging to place a sufficient amount of effective thermal mass in passive solar heating buildings with high solar contributions.
- Design the passive solar heating building for natural ventilation in summer using operable windows designed for cross ventilation. Additional air movement can be obtained through ceiling fans or a heat recovery ventilator.
- Select a durable, energy-saving envelope for the building.
- Provide adequate insulation levels for floors, walls, and roofs. As a benchmark for determining suitable insulation levels, check minimum insulation levels in the Council of American Building Official’s Model Energy Code.
- Provide entry vestibules and keep ductwork with the insulated envelope of the building to guarantee thermal integrity. Consider blower-door tests of model homes to show air-tightness and minimize duct losses.
The passive solar heating design uses construction materials and different structural elements like walls, floors, and roofs to use the sun’s heat energy and reduce energy consumption during winter.
1. Orientation of the building and openings
2. Thermal mass
4. Movement of air inside the house
True south is the direction toward the south pole.
The function of the overhang is to block sunshine during summer, resulting in the prevention of overheating inside the building during the hot season.
The extension of the passive solar-heated building along the east-west axis leads to an increase in south-facing elevation and the number of south-facing windows. This increases the amount of heat admitted into the house.