‘Passive design’ is design that takes advantage of the climate to maintain a comfortable temperature range in the home, so it’s naturally cooler in Summer and warmer in Winter.
In a passively designed home, the need for mechanical heating or cooling is reduced, meaning you can save money on your energy bills and live more sustainably.
Building a new home is the perfect time to get serious about passive design, since you have complete control over the different elements that need to be considered. However you can certainly implement some, if not all, of the strategies when renovating or upgrading your home. As you read through this article you’ll be able to identify what’s possible for your home and situation.
Your Building Envelope
A building envelope refers to your roof, floors, walls and windows, and the barrier they form to control the climate inside your home, through the control of airflow from outside.
If your building envelope is loose, it means the air can flow more freely through your home. Whereas a tight building envelope restricts the airflow and controls how it enters inside, therefore making this the preferred choice, particularly with the varied conditions we experience in Sydney and the Central Coast.
Passive Design Considerations
The strategies for passive design vary depending on your climate and the different characteristics of your site. However, there are always five main considerations:
Simply placing your home in the right direction can make a huge difference to its natural efficiency. Here in New South Wales, the ideal position is generally facing North. This allows you to:
- Get maximum sun exposure in Winter
- Easily create shade on walls and windows in the Summer
- Make the most of the warm and cold breezes when you need them
Following on from above, while you want maximum sun exposure in Winter, it’s important to create the right shade in Summer to avoid generating excess heat inside your home. At the same time however, you need to ensure that this shading doesn’t block the Winter sun, as the natural heat is critical at this time.
Strategic shading can be achieved with:
- Window awnings
- Other buildings
- Plants and trees – particularly deciduous that will lose their leaves in the Winter and let the sun through
Windows can be a major source of heat gain in the Summer and heat loss in the Winter. In order to create the right strategy for your windows, you must first take into consideration their size and location. Then you can make them more efficient with the use of:
- Shading to block out the sun
- Seals to protect from draughts
- Glazing to better control the airflow
- Film to reduce the effects of convection and conduction
Thermal mass refers to the way different materials absorb and store heat. Denser materials such as brick and concrete have a higher thermal mass because they’re able to store more heat. Whereas lightweight materials like timber have a low thermal mass.
For this reason it’s important to carefully consider which materials you’ll use in the different areas of your home, so you can capitalise on the different levels of thermal mass and maintain a natural temperature more consistently.
Effective insulation is critical for creating an efficient building envelope and naturally maintaining the temperatures in your home, as it regulates the airflow that comes in and out through your walls, floors, windows and roof.
One quarter of heat gain and loss occurs through your walls, so there are massive gains to be had by insulating them. Since there are a variety of installation options, it is possible to insulate walls made of all types of materials:
- Double brick
- Timber vinyl and compressed fibre cement clad walls
20% of heat gain and loss happens through your floors, because generally they are made from a material with a low thermal mass and/or there is a gap between the floor structure and the ground, which creates airflow.
By regulating this airflow with insulation, you’re able to prevent cold rising up from the ground, and heat/cool air escaping back into the ground from your home.
Without roof insulation you could be losing 35% of your heating/cooling capacity, which translates into 10 degrees cooler in summer and up to 7 degrees warmer in winter.
With three main insulation options for your roof, it’s easy to find a solution that fits with your needs and budget:
- Woolcell – a pump-In material combining natural Australian wool, recycled paper, Borax and Boric acid
- Polyester – made from the same material as pillows and doonas and installed with batts
- Fiberglass – great for those on a strict budget
You can further improve your efficiency by installing downlight covers and exhaust fan covers, to minimise gaps and reduce unwanted air loss/gain.
The great news about insulation, is it can easily be installed into existing homes, meaning you can make big improvements to your energy efficiency and carbon footprint, even if you’re not in a position to consider the other factors of passive design.
How to Get Started With Passive Design
Of course if you’re building a new home, you should have much more flexibility and scope to incorporate a lot, if not all, of the elements of passive design. So employing a specialist will help you to maximise these opportunities, while also keeping to your design aesthetic and budget.
If however you are renovating or upgrading your existing home, you should by now have a clearer understanding of what’s possible. Unfortunately, moving the orientation of your property is going to be a challenge, but you can certainly consider the thermal mass of the materials you use, add/remove shade, replace or upgrade your windows and install or upgrade your insulation.
If you decide insulation is the way to go for you, and you’d like to get a better understanding of your options, please get in touch with one of our experts who can talk you through the various solutions and even organise a free quote.