Why Passive Design is key to building an energy efficient home
When we conduct an energy rating report, our thermal performance assessors will do more than input numbers into a software program to assess your home or commercial building’s energy efficiency. We understand there are a number of design and building practises that work together to deliver an energy efficient home and we always refer to what’s called Passive Design principles for the minimum 6 Star Energy Rating.
In Australia, it’s estimated around 40% of energy use in the home is related to heating and cooling. Passive design incorporates design and building practises that best utilises your location’s climate to naturally generate and maintain heat in Winter and coolness in Summer. This makes for a comfortable home all year round; one requiring less additional heating and cooling.
Whilst passive design will vary depending on your location’s climate, experienced thermal performance assessors will incorporate its principle strategies in energy rating software to deliver you the minimum 6 Star Energy Rating and an energy efficient home.
What is passive design?
Put simply, passive design incorporates various strategies to collect heat from the sun and store it within your home in cooler months, and strategies to cool your home and release heat in warmer months. The end result is a home or commercial building that feels cool in Summer and warm in Winter without the need for powered heating or cooling devices.
Whilst passive design can incorporate higher upfront costs in design and some materials, overall it’s a cost effective solution to save on energy bills and reduce greenhouse gas emissions, all whilst producing a comfortable home or commercial building to live in and occupy.
Passive design includes various elements that work together and it’s important to choose skilled professionals (architects, builders and energy raters) to deliver a good passive design through to end build.
Below we outline 14 factors for good Passive Design and how to build an energy efficient home.
In Australia, there are eight main climate zones. It’s important to identify your climate zone when designing a home as strategies to keep homes cool in, say, a tropical climate would not be helpful in keeping a house warm in cooler climate zone.
Orientation relates to how your house or commercial building is positioned on your site to take advantage of your climate zone’s sun angles and breezes. For example, in southern Australian zones, living areas should face north to maximise sun exposure to provide natural heat in Winter.
Whilst orientation is about positioning your home to take advantage of sun for Winter heat, it’s important to also consider shading as part of passive design to minimise temperature increases from direct sun in Summer
Incorporating shading into your design can include eaves and roof overhangs, window awnings, shutters and pergolas. Large trees can also block significant amounts of direct sun to reduce the need for additional cooling in summer; deciduous trees have the added benefit of shading sunlight in Summer and allowing it through in Winter.
Reducing air leaks is one of the easiest tips to increase the comfort level of your home and reduce energy bills. Sealing your building against air leaks will reduce or eliminate heat loss generated in Winter and cooling loss in Summer.
It is, however, important to consider condensation (in some climate zones) and air quality issues when sealing a home.
5. Thermal mass
Good Passive Design considers the thermal mass of building materials and how they absorb, store, release and distribute heat throughout your building.
Using high thermal mass materials, such as concrete, bricks and tiles that absorb and store heat and slowly radiate it back through your home, can save on energy bills by averaging day to night temperatures. Low thermal mass materials such as timber that don’t easily store heat are good to reflect sunlight away.
It’s important to note poor use of thermal mass can result in exacerbating temperature extremes, such as radiating heat on a hot summer night.
6. Passive solar heating
Passive solar heating incorporates orientation, sealing and thermal mass to keep sun out of your home in Summer whilst letting it in Winter. This means your home will naturally keep heat inside in Winter and let heat escape in Summer.
7. Passive cooling
Passive cooling incorporates cooling strategies such as ventilation and shading to keep your home or commercial building naturally cool in Summer.
Well insulated walls, ceilings and floors that keep heat inside or outside (depending on what you need in your location) is a well-known method to maintaining year-round thermal comfort and reducing energy bills. Insulation level and type will depend on your climatic location and ideally should work alongside other passive design principles.
Glazing is widely known to be a major source of heat gain (in Summer) and loss (in Winter), therefore it’s vital to good Passive Design. It’s important to choose the right glazing option and the windows’ size and location in your home for your climate zone. Other factors to consider include how high up windows are located (because heat rises), shading and sealing.
Window Energy Rating Scheme (WERS) is an important reference that rates the energy-related performance of different window products.
10. Building layout
The layout of your rooms and outdoor spaces is another element of Passive Design. For most climatic zones in Australia, living areas should face north to capture all day sun for Winter months, and include horizontal shading to stop overheating in Summer. Bedrooms should face east for more comfortable summer sleeping. Rooms that face west will have good afternoon sunlight, but may overheat. South-facing rooms will have little to no sun.
11. Natural ventilation
Natural ventilation takes advantage of the natural wind in your location to increase thermal comfort. Ventilation design strategies will depend on your location, but should carefully consider the design layout and size and placement of openings.
12. Site Selection
When building a new home or commercial building, it’s important to consider how it and the surrounding area may change in the future. Considerations such as new or established trees growing and future multi-level developments can quickly change your building’s solar access. If solar access isn’t protected in your location, ideally find a site that’s deep from north to south and place the house at the north end.
Skylights provide natural light and improve ventilation, but they are also a source of heat gain and loss. When choosing your skylight, consider factors such as size and spacing, energy efficiency and climate.
14. Distribution mechanisms
A final consideration for good Passive Design is how the solar heat captured is transferred to different areas of your building by conduction, convection and radiation.
- Conduction is the heat moving between two objects in direct contact with each other, such as when a sun-heated floor warming bare feet.
- Convection is heat transferring through a fluid, such as moving air from warmer areas into the rest of the house.
- Radiation is heat you feel standing next to a sunny window.
Are you ready for the future of building?
Building an energy efficient home or commercial building that saves on energy costs, reduces carbon emissions and is comfortable and healthy for its occupiers is easier said that done.
There is not one element of Passive Design that’s more important than the other as they each need to work together to capture your location’s climate to best deliver you a naturally comfortable home.
Good Passive Design also requires the collaboration of experts in their field, architect to thermal performance assessor to builder, to deliver on best practises in their field.
The above elements are what we consider as experienced and qualified Thermal Performance Assessors and recommend in our reports accordingly.
Implementing innovation is always a more considered option on a budget. But it’s important to also add to the equation the cost of not innovating, of not implementing best practise, and not considering the lifetime of your investment and the people who will live in it.
Contact us via our online form or call on (03) 9135 0300 to discuss how we can provide an energy rating report to build an energy efficient home or commercial building. If you’re ready for quote, head straight to our free quote form.
For further reading, we recommend the Australian Government initiative http://www.yourhome.gov.au/.