Comfort, practicality, and aesthetics — these are the three most important factors in building any structure. If these are your priorities when building your home, you should venture into a passively-designed structure. Passive design is about creating an internal environment with consistent, comfortable temperature throughout the year while utilising the power of the sun, wind, and other natural resources. It enables you to warm and cool your home naturally. It gives you a home that isn’t 100% reliant on artificial heating and cooling, thus cutting your power use.
The process starts with designing a home that perfectly suits your location and the climate zone. In this blog, we’re going to discuss the everything that a Sydney and Melbourne resident needs to know about naturally cooling their home, so it remains comfy all year around.
Discover your climate zone
The National Construction Code (NCC) sets the minimum requirements for the design, construction, and performance of all buildings, both new and existing, throughout Australia. It divides the country into eight (8) climate zones. Sydney is under the warm temperate zone while Melbourne is in the mild temperate zone. Because the two cities are in the temperate regions, the locals experience a mild summer. Still, passive cooling techniques can help homeowners here ensure a cool and comfortable home during the hottest months.
Discover your climate zone is here.
Calculate your sun’s angle
Having the right amount of daylight inside the house is essential when building a passive house. To do this, you have to know the sun’s path throughout the day and at different times of the year in your location.
Here’s how you do it:
Step 1: First, take note of your location’s latitude. Melbourne’s is at approximately 38° while Sydney’s is at approximately 34°.
Our planet revolves around the sun. The phenomenon called an equinox occurs twice a year. It’s when the earth’s axis neither tilts towards nor away from the sun, resulting to a day and night of equal length.
Step 2: To find the angle of the sun at noon at your location, use these formulas:
Highest sun angle during Equinox = 90° minus the latitude of your location.
Highest sun angle during summer solstice = Highest sun angle during Equinox plus 23.5°
* The Earth tilted at 23.5° through the north and south poles
* The latitude of the North Pole is 90°N and the latitude of the South Pole is 90°S.
* The summer solstice is when the sun is at its highest point in the sky at noon and is marked by the longest day.
Using the formula, we found out that the angle of the sun at noon in Melbourne is at 52° (90°- 38°), which is slightly lower compared to in Sydney which is 56° (90°- 34°). During the summer solstice, the sun will be highest in the sky in Melbourne at 75.5° (52°+23.5°) and at 79.5° (56°+23.5°) ins Sydney.
Your architect should be able to use these measurements in designing a home that lets the right amount of natural light inside it. Too little and it will feel chilly. Too much and it will feel like a hot box.
Strategically position your windows
If you’re planning to build a new home, avoid putting too many windows on the eastern and western side of the house. East and west-facing windows receive excessive sunlight in summer but too little in winter, autumn, and spring.
- If you’re going to have east and west-facing windows, keep it small and well-shaded
- Keep them operable so you don’t compromise ventilation.
- Consider using glazed windows with a low solar-heat gain coefficient (SHGC). High-performance glazing such as low-e or toned glass will work too.
- Use shades and blinds with a reflective backing to avoid too much heat absorption.
- Close your drapes and blinds before the sun’s rays hit these windows.
North-facing windows receive twice the winter sun compared to east and west facing windows. These help brighten and warm your home better, so locate the common rooms such as your living, dining and kitchen here. To avoid excessive heat absorption, consider glazing, shading, and using window treatments.
Consider south-facing windows if you have a good view. These only require minimal shading from the sun. Keep these windows operable to heighten ventilation.
Having skylights or roof windows are an isolated case. These are exposed to the sun all through the day. Consider using blinds, shades, and covers that are specifically made for these windows to control the amount of light that comes in your space.
Make use of external shading
Shades can block up to 90% of the sun rays that can enter through your windows. These prevent too much heat absorption, especially during the hottest months.
The best kinds of external shading that can block the blistering sun in the middle of a summer day are eaves. Keep them at a depth of 600mm so they don’t block the winter sun. Horizontal shades like sails, covered pergolas, and awning can shield you from the sun that travels high above you. If you have an indoor-outdoor space, consider building a deep verandah for it can prevent the noon sun from entering the house too.
The sun also strikes the eastern and western parts of your house, but at a lower angle. Consider vertical shading like external blinds and laser-cut screens to shield these areas from the brunt of the summer sun from the east and west. You can also use trees and plants to shade the external wall surfaces of your home.
Choose a white or any light-coloured roof
Your roof is the most exposed surface to the sun. Consider having a white roof for it will reflect heat rather than absorb it. It reduces heat build-up in our homes and the heat island effect in our cities. It’s a practice done in New Zealand and some Mediterranean countries.
Unfortunately, many Sydney councils have laws regarding white roofing. If your council prohibits you, consider other light-coloured options which can deflect heat and look awesome.
Let the fresh air in
The types of window you have at home should promote the movement of air around the house. You can have a casement window that opens so the cooling breeze can come in the house. You can also use adjustable louvres on your clerestory windows. Fans expedite the air movement too and can make you feel more comfortable in the room.
Consider evaporative cooling
It’s cooler by an ocean or a river because of evaporation. The water absorbs the heat and evaporates. This hot air goes up into the atmosphere and pushes the cool air down as a refreshing breeze. You can achieve the same effect through having an artificial pond or any water feature near your home.
Also, situate plants along the path of the breeze. Plants transpire and it helps cool the breeze before it enters your home. They also filter the air, thus a steady stream of fresh air comes in.
Mind the thermal mass
Homes in Sydney and Melbourne are best made with heavy weight materials such as bricks, stone, tiles or concrete. These building materials have a high thermal mass, meaning they can store heat to keep the indoor temperature lower. When the temperature drops at night, the stored heat will be released into the house and exhausted through high windows or in a process called nighttime cooling.
Rely on nighttime cooling and the stack effect
These two are a team. Night time cooling or night purging happens when your home’s building envelope cools down and releases the warmth it stored all day. The stack effect refers to the natural movement of warm air in and out of a building. The warm air rises to the ceiling and will escape through a high, open window. Consider opening up the adjacent areas in your house to disperse the warm air throughout. At the same time, cool air from the outside will come in and keep the temperature inside comfortable.
Build a sustainable, eco-friendly, and energy-efficient home
If you’re living in Melbourne and in Sydney, these passive cooling principles will work for you. Invest in summer shading, catch cool breezes, and allow cross-ventilation and night time cooling and your home will be surprisingly comfortable especially during the hottest months of the year.
It’s also important to design your home for the entire year, not just one season, so consider the designs that will help you warm your home in the winter too.
We can help you take advantage of the climate to maintain a comfortable temperature in your home. Together, let’s design a home that doesn’t rely on auxiliary heating and cooling. We can help you reduce running costs through proper ventilation, window glazing, external and internal shading, and more importantly, insulation.