Incorporating Passive Solar Design into Energy Efficient Building
As BC’s Energy Step Code becomes implemented across the province, mandating energy efficiency targets for new buildings, there is an opportunity to draw on the principles of passive solar design to help buildings reach these objectives. Passive solar design allows a building to minimize it’s heating and cooling requirements by incorporating some simple spatial and thermal considerations.
Passive heating and cooling utilizes sun exposure on site to minimize solar gain in the summer (through shading) and to maximize solar gain in the winter. Passive solar heating can supply as much as 30 percent of a conventional home’s annual heating needs, with little or no increase in construction costs. Unfortunately, there aren’t any specific products that can guarantee effective passive solar performance. A building’s solar performance depends on its design, orientation, level of energy efficiency, and construction.
Principles of Passive Solar Design
Site Selection – select a site that has good southern sun exposure that is not obstructed by neighbouring buildings or topography.
Orientation – the building should be positioned with its long axis facing south, in order to maximize solar gain in the winter and minimize western exposure in the summer months.
Window Placement – place majority of the windows along the south side of the building. As a rule, the amount of south facing glazing should equal 9-12% of the homes’ conditioned floor area. East facing windows will allow morning sun, while large west-facing windows can allow in too much afternoon sun, causing overheating. North facing windows contribute to heat loss, so keep these small.
Shading – appropriately sized overhangs can keep high summer sun out while allowing low winter sun to enter and provide solar gain.
Room Layout – Locate more frequently used room like living and dining areas on the south side for optimal use of natural light during the day. Less-used room like bathrooms and storage are best to the north, and bedrooms in the east to take advantage of morning light.
Insulation – a continuous insulation layer with a high R-value will help to minimize heat loss during winter and heat gain in the summer.
Air-sealing – an air-barrier that is completely sealed around the entire building envelope will reduce heat loss through cracks and reduce the movement of moisture laden air through the building envelope.
Ventilation – Airtight high performance buildings need a controlled ventilation supply/exhaust system to maintain high indoor air quality by bringing in fresh air and removing stale, stagnant air.
Thermal Mass – Dense, heavy materials like concrete, masonry, stone and tile can store heat during the day and radiate back into the home during cooler nighttime hours.
Landscaping – planting deciduous trees can provide shading in the summertime but allow winter sun to enter the home.
Incorporating these simple principles into energy efficient design and construction takes advantage of natural solar and seasonal cycles to minimize your home’s heating and cooling needs!