As energy costs rise and environmental concerns grow, finding sustainable ways to keep your home comfortable has never been more important. That’s where passive cooling comes in.
What is passive cooling?
Passive cooling is a core tenet of Passive House design – but it’s not exclusive to these types of buildings. This design approach naturally regulates a building’s temperature without relying on mechanical systems, such as air conditioning. The concepts can be utilised in any new build to create a high-performance home, and are particularly relevant in Western Australia’s hot climate.
How does passive cooling work?
Passive cooling uses key building design choices, such as ventilation, shading, thermal mass, and insulation, to reduce heat gain and boost heat loss. Based on the materials and layout your home uses, it can stop excess heat from entering the home, while expelling unwanted heat efficiently and effectively. Techniques include strategic window placement, natural airflow, reflective roofing, and materials that absorb and release heat slowly, helping to keep spaces comfortable while reducing energy consumption.
Essentially, it’s a more natural way to keep indoor temperatures stable and cool, and reduce your reliance on expensive and energy-draining air conditioning.
Understanding passive cooling systems
Passive cooling puts a focus on using building materials and the home’s design to control the temperature during hot weather.
There are two core principles to passive cooling:
- Reducing heat gain, or heat prevention, is focused on stopping as much of the external heat from the weather and the sun’s rays from entering the home.
- Heat dissipation centres on helping to remove unwanted heat from the home as efficiently as possible.
Passive cooling design factors for your new build
Building orientation
How your house is placed in relation to the sun has a big impact on the amount of heat it receives throughout the day. When building a home, you have the chance to optimise its orientation right from the start.
In Australia, the path of the sun is to the north, so aim to orient your house on a north-south axis. Putting the main living areas on the north side allows their windows to receive the most sun during the day. And as the sun is at a higher angle, this reduces the effective surface area for the UV rays to hit, meaning it’s not receiving the full force of direct sunlight.
Floor plan and layout
Rather than relying on air conditioning or fans, carefully designing your home’s floor plan and layout can allow you to make the most of cooling breezes as they flow through your home.
Open plan and narrow home layouts can make the most of breezes, funneling the air through more effectively.
Minimising the number of windows on the western side of your home—while still having some—reduces the afternoon heat gain, while allowing you to take advantage of cooling afternoon breezes that roll in from the ocean and flush out the heat of the day. But keep them small, and high up, limiting their surface space while still ensuring you can throw them open and let the fresh air through the house in the afternoon.
When done in tandem with your orientation, it goes a long way towards the passive cooling of your home.
[Take a tour of a passive house by Trueline]
Roof design and materials
Your roof gets full sun throughout the day, so it’s important to choose the right materials and design.
As a first line of defence, choose light coloured roofing materials to reflect more of the sun’s direct heat.
Utilising efficient insulation in your roof and ceiling spaces also helps to slow or minimise heat transfer. Your builder can advise on the best materials to make this happen.
Ensuring good ventilation in your roof space also plays an important role in cooling your home. This creates a space for air to flow into and out of your house, and expel warm air as the temperature cools down.
Window design
Passive house design features carefully calculated eaves and overhangs, installed at the right angles, to limit the amount of direct sunlight hitting your windows. Given the changing angle of the sun throughout the seasons, this works to block the hottest summer sun while allowing full sun to come in during the winter months.
When choosing your windows, at a minimum, you should opt for double glazing. This adds a layer of inert gas in between the two panes of glass, which works to stop the amount of heat conducted between the outside and inside environments.
Thermal mass materials
When building a house on passive design principles, the thermal mass and thermal lag of your building materials play a big part in its heating and cooling.
- Thermal mass is a material’s ability to absorb, store, and release heat.
- Thermal lag is the speed at which they release that heat.
Heavy construction materials like concrete, stone, and brick have a high thermal mass with a low thermal lag, making them highly efficient materials for a passive home, particularly for your walls and flooring materials.
And while it may sound counterintuitive, this thermal mass helps to cool your home, too. If your window shading is calculated correctly, you can block the majority of the sun’s direct heat from hitting the thermal mass. Then throughout the day, the materials will absorb heat from inside the home instead, rather than from the outside, helping to keep a more even temperature throughout. Cooling afternoon and evening breezes then pass over the materials overnight, drawing out even more heat to cool your spaces down further.
Landscaping for passive cooling
Your landscape and garden design also play a part in passive cooling for your home.
Lush green gardens and plants, rather than hard surfaces like bricks or concrete, can help to reduce the temperature of the air surrounding your home. This happens through a natural process known as evapotranspiration, which draws moisture from the soil and plants into the air, cooling it.
Planting large trees and shrubs can work to block some of the sun, and if planted in certain ways, they can be used to create wind tunnels to funnel cooling breezes into crucial areas of your home.
Work with a builder who understands high-performance homes
If you’re looking into smarter, more sustainable, and energy-efficient ways to cool your home, contact TrueLine Homes and book a passive house design consultation.
We can help you utilise passive cooling concepts that make the most of your home’s design, orientation, layout, and building materials to limit the amount of heat that gets in during a hot Perth summer.