An Architect's No-Fail Methods for Cooling Your House in Summer
An architect explains the infallible logic of passive shading your home for maximum comfort during summer
Bridget Puszka
8 December 2017
Houzz Australia Contributor. Principal Architect at BP Architects, an award-winning Melbourne-based architectural consultancy that designs healthy, sustainable homes. Certified Passive House Designer.
Houzz Australia Contributor. Principal Architect at BP Architects, an award-winning... More
Did you know that passive solar principles for keeping your home cool can be applied worldwide? They are logical and make common sense, you just have to adapt them for your hemisphere, where you are located, and for your climate zone. Using the localities of Melbourne and Sydney as an example for Australia, this article explains what you can do to keep your home cooler in summer forever more.
Climate
Australia has eight climate zones as defined in the National Construction Code (NCC). The NCC sets the minimum requirements for design construction and performance of buildings throughout Australia. You can see what your climate zone is here. Within these eight climate zones are numerous sub-zones.
Melbourne is a mild temperate climate zone, and Sydney falls under warm temperate. As the recurring word ‘temperate’ implies, we enjoy pleasant and agreeable temperatures in both Melbourne and Sydney. However, using passive solar techniques, you can ensure a comfortable and cool home during the hot months of summer, no matter where you are.
10 Fixes for Homes That Face the Wrong Way
Australia has eight climate zones as defined in the National Construction Code (NCC). The NCC sets the minimum requirements for design construction and performance of buildings throughout Australia. You can see what your climate zone is here. Within these eight climate zones are numerous sub-zones.
Melbourne is a mild temperate climate zone, and Sydney falls under warm temperate. As the recurring word ‘temperate’ implies, we enjoy pleasant and agreeable temperatures in both Melbourne and Sydney. However, using passive solar techniques, you can ensure a comfortable and cool home during the hot months of summer, no matter where you are.
10 Fixes for Homes That Face the Wrong Way
Shading
Shading your home from the summer sun is the best way to approach a cooler home. This is because once sunlight has entered your house through your windows, this sunlight transforms into radiant heat, and is absorbed then re-radiated as long-wave radiation.
This long-wave radiation cannot pass back out through the glass, which leads to a build-up of heat in your home. This is a situation similar to a glasshouse, greenhouse or your car on a hot day, when temperatures can steadily increase.
Shading can block up to 90 per cent of the warmth before the sun heats up your home, so stopping the sunlight before it radiates into your home makes sense.
Shading your home from the summer sun is the best way to approach a cooler home. This is because once sunlight has entered your house through your windows, this sunlight transforms into radiant heat, and is absorbed then re-radiated as long-wave radiation.
This long-wave radiation cannot pass back out through the glass, which leads to a build-up of heat in your home. This is a situation similar to a glasshouse, greenhouse or your car on a hot day, when temperatures can steadily increase.
Shading can block up to 90 per cent of the warmth before the sun heats up your home, so stopping the sunlight before it radiates into your home makes sense.
North, east and west shading
The sun travels high overhead in the middle of a summer day. Therefore, if you have eaves or horizontal shading this will shade your windows from the high summer sun. Horizontal shading can include shade sails and pergolas with louvres.
On the east and the west sides of your home the sun will be at a lower angle, as that’s where the sun rises and sets. Vertical shading works well on these sides of your house. Vertical shading can include deciduous trees or vines, deep verandahs or adjustable vertical screens such as awnings or external blinds. Deciduous vines and trees, other plants, shadecloth and screens can all be utilised to provide seasonal shading.
Temperatures can be up to 10 degrees cooler in the shade, so it also helps to shade the wall surfaces that will get the full brunt of the summer sun in the east and west.
The sun travels high overhead in the middle of a summer day. Therefore, if you have eaves or horizontal shading this will shade your windows from the high summer sun. Horizontal shading can include shade sails and pergolas with louvres.
On the east and the west sides of your home the sun will be at a lower angle, as that’s where the sun rises and sets. Vertical shading works well on these sides of your house. Vertical shading can include deciduous trees or vines, deep verandahs or adjustable vertical screens such as awnings or external blinds. Deciduous vines and trees, other plants, shadecloth and screens can all be utilised to provide seasonal shading.
Temperatures can be up to 10 degrees cooler in the shade, so it also helps to shade the wall surfaces that will get the full brunt of the summer sun in the east and west.
Roof
With a high overhead sun at midday, the roof is the surface of your house most exposed to the summer sun. A white roof will reflect the heat from the high summer sun overhead and help keep your home cool. Whirly birds or vents in your roof attic space will help exhaust the build-up of heat in your roof, and keep your home cooler.
With a high overhead sun at midday, the roof is the surface of your house most exposed to the summer sun. A white roof will reflect the heat from the high summer sun overhead and help keep your home cool. Whirly birds or vents in your roof attic space will help exhaust the build-up of heat in your roof, and keep your home cooler.
Windows and skylights
If you are planning to build a new home, keeping windows on the east and west to a minimum will also help reduce the summer heat. If you cannot shade the outside of your windows, you might want to use a reflective internal shade, which can reflect the sunlight before it enters into your home.
Or on east- and west-facing windows you could use glazing with a low solar-heat gain coefficient (SHGC), particularly if the windows are large. These windows use toned glass or tinted films to reduce the amount of solar heat transmitted through them. A low solar-heat gain coefficient will allow less solar heat to be transmitted through the window. This will also block the winter sun, however, so it is better to use adjustable external shading if possible.
There is little solar heat gain from south-facing windows so there is no need for these to be low SHGC. Skylights, on the other hand, will often be exposed to the sun all through the day. They can be protected with reflective blinds or external blinds or louvres.
Browse homes with sunny skylights
If you are planning to build a new home, keeping windows on the east and west to a minimum will also help reduce the summer heat. If you cannot shade the outside of your windows, you might want to use a reflective internal shade, which can reflect the sunlight before it enters into your home.
Or on east- and west-facing windows you could use glazing with a low solar-heat gain coefficient (SHGC), particularly if the windows are large. These windows use toned glass or tinted films to reduce the amount of solar heat transmitted through them. A low solar-heat gain coefficient will allow less solar heat to be transmitted through the window. This will also block the winter sun, however, so it is better to use adjustable external shading if possible.
There is little solar heat gain from south-facing windows so there is no need for these to be low SHGC. Skylights, on the other hand, will often be exposed to the sun all through the day. They can be protected with reflective blinds or external blinds or louvres.
Browse homes with sunny skylights
Air flow
A cooling breeze can make the difference between a room that feels overly warm and one that is comfortable. This works by facilitating evaporation of perspiration, thereby cooling you in the process. This makes it much more pleasant to be in a room with a breeze than one that does not have any air movement. Fans can help facilitate this air movement, and make a room more comfortable during the hotter months.
The types of windows your home has also makes a big difference, as they can either block or help direct air flow through a home. A casement window that opens into the path of a cooling breeze can direct air through a home. An awning window in the same location may block the flow of air, and reduce the amount of cooling breeze that can enter the home.
Tip: Having a larger window on the side of the house that is down wind or sheltered from the wind, and a smaller opening on the side facing the wind, will increase the breezes through the home. This happens because of the pressure differentials in the house as the wind is sucked towards the area of lower pressure.
A cooling breeze can make the difference between a room that feels overly warm and one that is comfortable. This works by facilitating evaporation of perspiration, thereby cooling you in the process. This makes it much more pleasant to be in a room with a breeze than one that does not have any air movement. Fans can help facilitate this air movement, and make a room more comfortable during the hotter months.
The types of windows your home has also makes a big difference, as they can either block or help direct air flow through a home. A casement window that opens into the path of a cooling breeze can direct air through a home. An awning window in the same location may block the flow of air, and reduce the amount of cooling breeze that can enter the home.
Tip: Having a larger window on the side of the house that is down wind or sheltered from the wind, and a smaller opening on the side facing the wind, will increase the breezes through the home. This happens because of the pressure differentials in the house as the wind is sucked towards the area of lower pressure.
Night time cooling and the stack effect
You can rely on night time cooling, when air temperatures drop at night time, or if there is a change in weather with cooling breezes, to exhaust the hot air out of your home. As the air temperature cools, the heat which has been absorbed into your home’s thermal mass, whether that is a concrete slab, stone or bricks, will release this heat and cool down.
The stack effect is the movement of air in and out of a building using air temperature and the natural flow of heated air. Hot air rises, so placing an openable window high on the wall or in the roof will allow you to exhaust hot air. You can draw in cool air at lower levels to help move this warm rising air.
The size of a room also matters in terms of comfort. A small room will heat up quickly unless the heat can be released. If you can open up areas in your house to increase the internal volume of your home this will help disperse the hot air throughout.
You can rely on night time cooling, when air temperatures drop at night time, or if there is a change in weather with cooling breezes, to exhaust the hot air out of your home. As the air temperature cools, the heat which has been absorbed into your home’s thermal mass, whether that is a concrete slab, stone or bricks, will release this heat and cool down.
The stack effect is the movement of air in and out of a building using air temperature and the natural flow of heated air. Hot air rises, so placing an openable window high on the wall or in the roof will allow you to exhaust hot air. You can draw in cool air at lower levels to help move this warm rising air.
The size of a room also matters in terms of comfort. A small room will heat up quickly unless the heat can be released. If you can open up areas in your house to increase the internal volume of your home this will help disperse the hot air throughout.
Natural evaporative coolers
Plants naturally transpire and when placed in the location of breezes, can help cool down the air temperature of a breeze before it enters a home.
The same effect can be achieved with water evaporating from ponds and water features drawing the breeze across these water bodies into the home. In humid climates, however, this will not cool down the breeze as the air is already saturated.
How to Select Garden Shades and Shelters
Plants naturally transpire and when placed in the location of breezes, can help cool down the air temperature of a breeze before it enters a home.
The same effect can be achieved with water evaporating from ponds and water features drawing the breeze across these water bodies into the home. In humid climates, however, this will not cool down the breeze as the air is already saturated.
How to Select Garden Shades and Shelters
Thermal mass
Thermal mass in a house is heavy weight materials such as bricks, stone, tiles or concrete. This thermal mass can help store heat during the hottest part of the day, and help keep the indoor air temperature lower. At night time, when air temperatures drop, this heat will be released from the thermal mass and can be exhausted from the house through high windows or night time cooling.
Thermal mass in a house is heavy weight materials such as bricks, stone, tiles or concrete. This thermal mass can help store heat during the hottest part of the day, and help keep the indoor air temperature lower. At night time, when air temperatures drop, this heat will be released from the thermal mass and can be exhausted from the house through high windows or night time cooling.
For the swotter: the sun’s path
Here, we can use Melbourne and Sydney as examples, to help you determine the sun’s path throughout the day and at different times of the year; Melbourne’s latitude is approximately 38° and Sydney’s latitude is approximately 34°.
Equinoxes occur twice a year when day and night are of equal length. This is when the earth’s axis in neither tilted towards nor away from the sun, resulting in nearly equal amounts of daylight and darkness. To find out the high angle of the sun at noon, you can work it out for solstices and equinoxes.
Equinox = 90° minus latitude.
Summer solstices = equinox + 23.5° (the tilt of the earth is 23.5° through the north and south poles).
For Melbourne the angle of the sun at noon at the equinox is 90° minus 38°, which equals 52°. For Sydney the angle is slightly higher at 56°. So at the summer solstice, the sun will be highest in the sky in Melbourne at 75.5° and again slightly higher in the sky in Sydney at 79.5°. The summer solstice is when the sun is at its highest point in the sky at noon and is marked by the longest day.
Geoscience Australia allows you to find the latitude of more than 250,000 place names in Australia and calculate the sun angle at any time of the day, on any day of the year.
Here, we can use Melbourne and Sydney as examples, to help you determine the sun’s path throughout the day and at different times of the year; Melbourne’s latitude is approximately 38° and Sydney’s latitude is approximately 34°.
Equinoxes occur twice a year when day and night are of equal length. This is when the earth’s axis in neither tilted towards nor away from the sun, resulting in nearly equal amounts of daylight and darkness. To find out the high angle of the sun at noon, you can work it out for solstices and equinoxes.
Equinox = 90° minus latitude.
Summer solstices = equinox + 23.5° (the tilt of the earth is 23.5° through the north and south poles).
For Melbourne the angle of the sun at noon at the equinox is 90° minus 38°, which equals 52°. For Sydney the angle is slightly higher at 56°. So at the summer solstice, the sun will be highest in the sky in Melbourne at 75.5° and again slightly higher in the sky in Sydney at 79.5°. The summer solstice is when the sun is at its highest point in the sky at noon and is marked by the longest day.
Geoscience Australia allows you to find the latitude of more than 250,000 place names in Australia and calculate the sun angle at any time of the day, on any day of the year.
Summer cooling
These summer cooling principles can be applied to houses in Melbourne and Sydney. Careful consideration of passive solar cooling during the summer should also take into account the winter months, to ensure that you have thermal warmth in winter when you want it.
In our temperate climate, if you do not allow for summer shading, cross-ventilation, night time cooling, insulation and catching the cooling breezes, you may find your home uncomfortably warm in summer. These simple techniques work surprisingly well, and are worth implementing to make your home more comfortable throughout the year.
Tell us
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Browse landscape designers who can help to shade your home
These summer cooling principles can be applied to houses in Melbourne and Sydney. Careful consideration of passive solar cooling during the summer should also take into account the winter months, to ensure that you have thermal warmth in winter when you want it.
In our temperate climate, if you do not allow for summer shading, cross-ventilation, night time cooling, insulation and catching the cooling breezes, you may find your home uncomfortably warm in summer. These simple techniques work surprisingly well, and are worth implementing to make your home more comfortable throughout the year.
Tell us
If you found this story helpful, like it, bookmark it, save the photos and share your thoughts below. Join the conversation.
More
Browse landscape designers who can help to shade your home
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i've used BASIX for a dual occupancy rural dwelling, several residential renovations and the latest rural steel shed dwelling without any problem and i seem to remember that you can apply for special consideration for anything that doesn't suit the standard (although responses from BASIX staff was less than encouraging and i couldn't lie) but, for eg our new project doesn't have access to gas and we didn't want to use solar power and hot water so i've found that by upping the grade on the taps and testing the impact of the suggested space heaters or cookers and altering windows (size, shape orientation or style) this counteracts the lower rating for the water and space heating and i always aim for the lowest pass rating as that allows for more choices when final decisions have to be made.. but, luckily for us i like playing with the program to see what alternatives there are before finalising any plans... an option that takes a lot of time but would be very expensive to pay for professional BASIX calculations
Basix is a software tool that provides some measurement of the sustainability of a building. There are a number of tools available such as AccuRate and First Rate. The NSW Dept. of Planning describe these tools as ‘simulation programs used to estimate the heating and cooling loads of a dwelling’. The regulations that they fall under in the Building Code of Australia / National Construction Code is the Energy Efficiency Regulations.
Although I understand your frustrations with these tools, it is worth noting that these tools are just that. Tools. They have a number of assumptions built into the program which may or may not rate the energy building efficiency of your dwelling. As bob marley found out, it did not allow for their home. Firstrate, for example, favours brick veneer construction on a concrete slab in its software.
The certificates and the rating that you obtain using these tools do not replace applying knowledge and energy efficiency principles in the design of a project. Get this right and you have a home that will be comfortable to live in all year round that doesn’t use a lot of energy.
For example, a home I designed has indoor air temperatures mostly between 20degC and 25degC all year round despite having outdoor air temperatures that fall to zero in winter and go up to 40degC. My Client said “So it seems a well-designed & well-built house does indeed provide good thermal performance without any further energy input than the sun, wind, & ceiling fans.”
Although it is compulsory to meet compliance with these house energy rating tools, And as oklouise said, these tools can be tweaked to get compliance.
The principles of best practice energy building efficiency will win hands down every time. For your benefit.
The benefit to you comes with an energy efficient home that has been designed to respond to your climate and the sun path and your surrounding environment. That's when you get a great outcome in a home that will be comfortable to live in with low energy bills.
I Love those large overhangs keeping the sun out. Must take some engineering :) . great in photos too of course!