1. Cooling by keeping the hot air out and the cool air in
Turn off the lights and TV
It’s always a good idea to turn off lights on hot summer days because they affect the temperature of the room. Incandescent light bulbs produce 95% heat, so they actually produce 19 times more heat than light. LEDs are 5 times or so more efficient, but they still produce 4 to 5 times more heat than light. However, because they do produce more light per unit energy consumed, the heat produced is also much lower. Switch to LEDs.
Turn off all heat sources such as lamps, plug-in power adapters, your computer and the TV when you’re not using them. Anything electrical in your home ultimately generates heat, so anything not being used should be turned off at the wall; it’s that simple.
Close your windows
It may not seem to make sense, but on hot summer days opening the windows will often make your home warmer, not cooler. Close windows – along with blinds and shades – before the sun hits your house in the morning.
When night falls, if the air outside is cooler open windows wide, particularly those oriented towards prevailing winds so you can take advantage of cross ventilation. This will allow the cool night air to circulate. Windows on the east and west of your home receive low-angle summer sun, so shade these with curtains, blinds or shutters.
You can also invest in double-glazed or WERS rated windows to prevent unwanted heat from being absorbed through your windows. Double-glazed windows have two glass panels in the same frame, separated by a small space for air. The insulation properties of double-glazed windows stop a significant percentage of heat entering the home as they reduce the amount of radiated heat gained.
Windows Energy Rating Scheme (WERS) rated windows and WERS rated window films allow you to compare different window choices for their energy efficiency performance and according to the climate zone of your property.
Use trees strategically
Your house heats up when the sun beats down on it relentlessly on hot summer days. Let nature help reduce your energy bills – plant deciduous trees on the east and west sides of your home to shade your house. Also consider planting trees or shrubs to shade high-heat areas such as air-conditioning units that emit heat, and driveways and walkways that absorb it. You can also put house plants – particularly larger potted trees – in front of sunny windows to absorb some of the sun’s energy.
Being wise about water in the garden
Gardens typically count for the largest percentage of water used in the home – so through creating a low water garden, made up of native plants suited to your region, you can decrease the amount of water used to upkeep your garden. As rainfall typically decreases over summer, water restrictions may come into effect in your area, so having a low water garden will mean you are not relying on being home to water your garden for it to remain kept and alive.
Just as shady leafy trees work to shield your home from the sun’s rays, awnings can save you money on energy bills by cutting down on the heat your house absorbs. These can be fixed or retractable or you can rig up a temporary awning as they do in Morocco using fabric with eyelets, rope and poles.
For most climates, installing awnings between 450 and 600mm on north-facing windows will prevent the summer sun from heating up your home, leading to passive shading – meaning shading without any action from the occupant. Awnings between 600mm and 1200mm are required for tropical climates of Australia.
Insulate your ceiling
Keep unwanted heat out with bulk insulation or reflective insulation in your ceiling. Insulation is measures by its R-value (resistance to heat) and the value you require will depend on which climate you live in. While you can install insulation using DIY methods, it is best to consult with an accredited installer. You can also install insulation in the walls and floors for more effective measures throughout the year.
Reduce cooking with the oven
Don’t use the stove or oven to cook on hot days. Use the grill, microwave, a slow cooker or barbeque meals outside. Even better, eat fresh summer salads and no-bake desserts.
Cooking with the power of the sun
This is so much fun. On really hot days (over 32°C), slow cook tomatoes in the sun.
2. Cooling by moving the air in and through the house
Capture the breeze – the power of cross-ventilation
Moving air through your home naturally is the best solution when it comes to saving on energy costs and consumption. It is also healthier as there are no ducts and filters to worry about cleaning as with air-conditioning. Moving air through the house in this way can provide thermal comfort, which is when you are in balance with your environment, feeling neither too hot nor too cold.
Capturing natural breezes will make your home more desirable and cost efficient. The optimum is cross-ventilation – pressures generated on the building by the wind drive air through windows or doors on one side of the building through to windows or doors on the opposite side, making sure cool breezes can pass right through the house. Windows are aligned with internal doors in a way that does not block weaker breezes.
So, when the air is cooler outside than inside the house, and you want to take advantage of that, it is best to have 1x area of window open to the windward side and 2x areas of window open to the leeward side. This causes a pressure differential that draws the air through the house more effectively.
Getting the most from your fans
Did you know? An air speed of 0.5m per second equates to a 3 degree drop in temperature at humidity of 50%.
Ceiling fans don’t actually cool the room itself, they cool the people inside. So remember, when you go out make sure you turn off the fans. A ceiling fan actually costs more to install than an air-conditioning unit, but its operating costs can be a fraction of the cost.
During summer the direction of the breeze from the fan should be blowing down on you, not upwards which is best for winter.
Floor, upright and portable fans
Fans need to be placed directly in front of you for you to really feel the benefit. Spraying your face with water when in front of the fan will help bring your temperature down – the water evaporates off your skin maximising the cooling effect of the fan.
You also might like to try small, portable, water-misting fans. These portable devices are battery operated so you can take them with you wherever you go. As you mist and fan yourself the water evaporates off your skin, giving you an instant cooling sensation.
Getting the most from your air-conditioner
Buy energy-rated appliances
Whether you’re buying a central air-conditioner or just one for a single room buy the most energy efficient one you can find. In Australia and New Zealand it is now mandatory that most products feature an “Energy Rating” Label showing the energy rating up to 6 stars (or 10 stars for really efficient products). Depending on the star rating, standby power usage can be reduced by up to 50%. The Australian consumer watchdog, CHOICE, provides data on “standby to wake scores” for certain products, indicating that consciousness is indeed growing and people are wising up.
The Energy Rating label enables consumers to compare the energy efficiency of domestic appliances in a fair and balanced way. It also provides incentive for manufacturers to improve the energy performance of appliances. To compare specific air-conditioners and other appliances, visit the Energy Rating website.
The Energy Rating App
Use your thermostat wisely
You may be surprised to find that the contrast between outdoor and indoor temperatures matters as much as the absolute temperature inside your home. When you’re home, set the temperature at 21°C to balance comfort with energy and cost savings.
If you have central air controlled by a thermostat, use a programmable thermostat to save energy by increasing the heat significantly. Turn your thermostat up a few degrees rather than having it really cool; say, 24–26°C during the day when the house is empty. You can give up a couple of degrees at night too – especially on the hottest days.
Air filter check
Whether you have central air or a room air-conditioner, a dirty filter will reduce its efficiency, making it use more energy and cost more money to do the same job. Clean your air filter monthly and expect to change the filter every three months.
Service your air-conditioner regularly
- If you have central air-conditioning, consider an annual checkup. A professional should be able to diagnose any inefficiencies before you’ve wasted money on monthly cooling bills.
Tips for extra efficiency
- Any exterior air-conditioning equipment should be installed on the shaded side of the house, with plenty of free space around it.
- Cool only one or two rooms – those that you are using the most. Cooling one room with a split air-conditioning unit requires much less energy (and investment) than a central air system.
- If the machine has adjustable louvres, adjust them towards the ceiling for cooling.
- Use door snakes to insulate the gap between the bottom of doors and the floor.
- Close your windows and blinds so the air-conditioner functions as efficiently as possible.
- Only use the air-conditioner on the hottest days, and remember to turn off your system (or set it to “away” mode) when you’re travelling.
- If you are purchasing a new air-conditioner, refrigerative air-conditioners are effective in most climates, and are available with a reverse cycle option.
- Evaporative coolers are really only suited to hot low humidity climates.
3. Keeping your body cool
Take a cold shower or bath or go swimming
It may sound obvious, but it’s worth saying: If you’re hot, cool off your core temperature by immersing yourself in cold water. Unless there’s 100% humidity, the evaporation of water off your skin will further cool you once you emerge from the water.
If you don’t have a pool and you’re not near the beach then you can fill your bathtub with cool water and get in. Once you are used to the temperature, let some water out and refill with cold water. Keep doing this until you are sufficiently cold. Your body will stay cool for a long time after you get out. For a fast cool-down, add ice!
Run cold water over your wrists for 10 seconds on each hand. This will reduce your temperature for roughly an hour.
Soak your feet in a bucket of cold water. The body radiates heat from the hands, feet, face and ears, so cooling any of these
will efficiently cool the body. Kids wading pools are great for adults’ feet too.
For a shortcut, use water and ice cubes or wet a handkerchief and put it on the back of your neck. There are much bigger blood vessels in the neck, so you can make the rest of your body think that you are cool … but make sure you don’t overdo it.
Drink water frequently. The relief is almost immediate, and will last for up to one hour or more. Your body will feel cooler if you are hydrated. Try drinking a glass of water at least every hour. Adding a squeeze of lemon or lime to your water makes it even more refreshing.
Keep cool on the inside
Keep hydrated and cool with cold beverages. Just as drinking a nice cold drink cools your body, eating cold food helps keep your internal temperature lower on a hot day. But remember, cold, sugary drinks will heat you up much more than warm, non-sweetened drinks. Explore summer salads rather than cooked meals.
Cucumbers are very astringent and cooling – you can even take a cold cucumber from the fridge and place on your forehead; it works remarkably well!
Frozen fruit: For kids, try freezing bananas. Peel the banana and wrap in plastic and place in the freezer for a healthy cooling treat. They taste just like ice-cream and are great to replace ice-cream in smoothies. Frozen grapes work really well too
Wear the right clothes
Be sure your clothing is made of natural fabrics and loose-fitting. Wear clothes made from fabrics such as cotton, silk and linen rather than artificial fibres like polyester and rayon, which can generate heat. Of course, there are some sports performance fabrics that are the exception.
Wear light colours. Darker colours will absorb the sun’s heat and stay warmer longer than light or white clothing, which reflects light and heat.
Other sources for more tips on how to be sustainable at home:
- Your Home
- Royal Institute of British Architects
- The Daily Green
- Sustainability Victoria
- Positive Charge
- Feature image credit to ©iStock.com/Martin Dimitrov