Incorporating Passive Solar Design into Energy Efficient Building

Incorporating Passive Solar Design into Energy Efficient Building

Introduction

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.

A diagram shows how to maximise passive solar heating in the home. Internal walls should be well insulated. There should also be good roof and ceiling insulation. The home should be able to avoid hot summer and cold winter winds. Deciduous trees are good for sun control, and when the sun is lower in winter, allows maximum sun penetration; but during summer, the tree’s foliage blocks the height of the summer sun.

 

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.

Image result for passive solar orientation

 

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.

Image result for passive solar winter sun

 

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.

A cross-section of a home indicates how to insulate well. External walls should have up to R2.0 insulation; cavity brick walls should also be insulated. Insulation should also be used under timber and suspended slab floors. Up to R3.5 ceiling insulation should be used, and walls between ceilings should be insulated to the same rating as the ceilings. Pay special attention to cathedral type ceilings.

 

 

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.

A diagram of a house shows potential sources of air leakage. At the base of the house, this includes gaps between walls or floors and skirting boards, gaps between floorboards, and gaps where pipes penetrate walls. On the sides of the house, this includes gaps between windows, air vents, fixed air conditioners and heaters, construction joints between wall materials, as well as gaps up chimneys and gaps around doors. On top of the house, this includes gaps between walls or ceilings and cornices, vented downlights, exhaust fans ant vented sky lights.

 

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.

A cross-section diagram illustrates how a north-facing window can be used to better heat a home during winter. During summer, the angle of the eaves means that direct sun is excluded. But in winter, direct sun enters the north-facing window and heat is absorbed by the concrete slab during the day.

 

Landscaping – planting deciduous trees can provide shading in the summertime but allow winter sun to enter the home.

Image result for deciduous trees passive solar

 

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!

 

References:
http://www.yourhome.gov.au/passive-design/passive-solar-heating
https://www.energy.gov/energysaver/energy-efficient-home-design/passive-solar-home-design
https://www.ecohome.net/guides/1428/passive-house-and-passive-solar-what-these-buzz-words-really-mean/