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Beat the heat


Choosing the right aircon

When it’s stinking hot outside, you’d crawl over hot coals for a bit of air conditioning. And while it can be expensive to run, there are ways to reduce the costs, and it pays to know which one to choose. An air conditioner’s capacity is measured in kilowatts (kW). If your home is not insulated, you’ll need a unit of about 0.14kW/m2 capacity. When used in a 20m2 room, that’s a 2.8kW unit. If your home has ceiling insulation, you’ll need roughly 0.10kW/m2, or a 2kW unit in a 20m2 room, and if your home is fully insulated, you’ll need 0.08kW/m2 capacity, or a 1.6kW unit, to cool that 20m2 room.


Shady character

Often the best things in life are free, and this applies to keeping your home cool as well. On hot days, close up the house to stop the hot air getting in. As the temperature drops in the evenings, throw open the windows at opposite ends of the house to capture breezes.
Try planting deciduous trees to shade north- and west-facing windows. Ask at your nursery for the best balance between the mature height of the trees, the density of the foliage and potential for root attack of the house footings and pipes, and potential bushfire hazards.
With roof space temperatures reaching 60°C on hot days, a whirlybird can suck out hot air. They are wind driven, so there are no ongoing costs. But even if your roof is insulated, the heat from the cavity can transfer into the house. Purging that hot air, or preventing it from reaching that level in the first place, will keep you cooler.


Clever air

Enter Smartbreeze. This is a thermostatically controlled solar air mover that not only purges
hot air in summer, but recirculates warm air in winter and on cold nights. In summer it should reduce temperatures by 5-10°C, and reduce energy usage by up to 40 per cent. Simply set your thermostat (to say, 22°C), and the unit will try to get as close to that temperature as it can using the ambient or heated air available.


Roof types

If you have a corrugated metal roof you can use the solar-powered Smartbreeze unit, which has a fan that only draws 14W. It uses air trapped between corrugations and sarking, has a battery pack to run the unit at night, and 240V back-up. If the gap is filled with an insulation blanket or you have a tiled roof, you’ll have to use a 240V powered unit that uses a larger 52W fan, which is still less than a 60W light bulb.
Once installed, the unit will extract hot air or pump in warm or cool night air, day or night, to try to maintain the temperature of your thermostat setting. This, in turn, allows you to reduce the use of air conditioners and heaters. Installation is by accredited installers, or you can do it yourself in about half a day (for instructions, see below).

Misting system

Water misting has been used for years for industrial cooling, but the same concept of flash evaporation to cool air can be used to keep you cool, too. This outdoor misting system uses a series of 0.3mm nozzles to create a ‘fog’ of ultra-fine water droplets, which evaporate in hot weather and cool the air. Depending on humidity and where you are, the air temperature can be lowered by 7-12°C.
Everything is in the Mr Mister kit, including a filter to stop the nozzle clogging up. The system runs off mains water, and uses only about 1.8L of water per hour. Larger kits can serve for whole patio and pergola areas.

Gather your supplies
• 2 Mr Mister misting kits for a large umbrella
• Large outdoor umbrella

Step 1
Lay out tube on ground and fit end plug. Cut off eight 600mm sections using cutter supplied. Join sections with the nozzle holders, which slip and lock (grab and seal) pipe as you push them together. At other end, add a tap fitting and insert an inline polyphosphate filter about 1m from tap fitting. Attach to tap and then run water through system to flush out the line.

Step 2
Screw 0.3mm mist nozzles into holders. Hand-tighten firmly without tools, as each nozzle has its own seal.

Step 3
Attach the flexible alligator clips to tubes, then clip to edges of umbrella. Turn it on again and check nozzles are working. Ahh, the cool!


Set up smart breeze

Gather your supplies'
Smartbreeze kit (solar or powered) which includes roof unit, electrostatic filter, 200mm flexible ducting, 200mm ceiling register, thermostat, sensors, wiring

you’ll also need
Power outlet for 3 cables (fitted by electrician); roofing silicone (clear or colour matched); duct tape; self-drilling screws; plasterboard saw; safety harness

Step 1
Decide on location for unit. About 3-4 rows of tiles down from top of roof is best, on a north-facing surface above where internal ceiling outlet (register) will be. The ceiling register should be in the main room you want to cool, although more than 1 register can be used. Have an electrician install a pair of double power outlets in the roof space within a metre of roof unit and electrostatic filter.

Step 2
Remove 8-10 tiles to install apron of roof unit. Walk on roof carefully to avoid cracking tiles,
and be sure to wear a properly anchored safety harness. Cut away any sarking that is in the way.

Step 3
Lift tiles above opening for roof unit and slide apron into place, well under tiles above. Measure gap to right-hand side of rafter or truss to make sure there’s room for 200mm fan without having to cut a rafter. Screw apron to batten above with
2 self-drilling roofing screws.

Step 4
Using handsaw, cut out small section of tile batten to fit fan unit.

Step 5
Feeding down cables first, slip main unit over apron’s upstand and make sure it fits with plenty of room for fan duct. If not, undo screws holding apron and slide assembly until it fits and re-screw. Secure roof unit to apron with 2 self-drilling screws in each side.

Step 6
Replace tiles, making sure they are fitted properly. You may have to measure and cut some tiles to fit in place. Cut using angle grinder and masonry cutting disc. Dress bottom flashing to profile of tiles.

Step 7
Seal around join with a roofing silicone, in case of water build-up. This is important for roofs with a low slope.

Step 8
Unclip collar to remove top of unit. Connect cables for ambient temperature sensor and thermostat. The roof heat sensor is already inside roof unit. Then reseal the top.

Step 9
Feed wire and install outdoor ambient temperature sensor under southern or eastern eaves so it’s out of direct sun. Also feed wires and install thermostat in the house. It should be centrally located on an internal wall, about 1.5m above floor.

Step 10
Suspend electrostatic filter unit under roof unit using strapping provided. The strapping allows filter to be mounted with no need for complex framing. Filter cleans potentially dusty air collected from roof space and needs filter changes every 3-12 months depending on conditions. Use flexible ducting to connect filter to spigot on underside of roof unit and tape both inner and outer layers to unit and filter.

Step 11
Run more ducting from bottom of filter to position where the ceiling register will be. At centre of register position, drive a screw through ceiling so it pokes through underneath.

Step 12
On underside of ceiling, use template supplied with ceiling register to mark in a circle for vent, then cut out circle with a plasterboard saw.

Step 13
Reach inside hole and pull flexible ducting through and tape to register. Flip up clips on register, push through hole and clips will automatically snap to hold vent in place.

Step 14
Plug in power cables, switch on system, and program control unit using instructions provided. Then it’s time to sit back and be cool.


Add an awning

When sunlight enters a room through glass, it changes in part to infrared radiation, which is trapped inside and heats the house. The only protection is stopping the sun hitting the glass in the first place.
Putting up an awning will only take an hour or two. Depending on colour, awnings can provide up to 75 per cent shading, with the most effective being light colours, as they reflect heat rather than absorb it. These awnings have a UV-resistant fabric, are available in a range of sizes, are self-locking and, as they are at an angle to the window, will allow heat trapped behind the awning to escape.

Gather your supplies
• 1800mm outdoor awning
• Drill and masonry drill bit

Step 1
Mark a line 100mm above window, or as high under eaves as you can if window is full height. Level across from 1 window to the other. Mark in position of 2 brackets to suit width of awning, and drill four 4mm screw holes in wall or masonry using an appropriate bit. In clad walls you’ll need to screw brackets to framing members, such as studs beside window. Screw on brackets with clamping screws facing down. To do this in brickwork, drill a 4mm hole with a masonry bit for each screw and insert plastic wall plugs.

Step 2
Unwind clamping screws so they leave bottom bend of bracket completely clear. Slip awning head box into brackets, align so it’s centred over window, then use bracket clamping screws to secure awning in place.

Step 3
Use cardboard template to mark holes for guide arms under brackets. Align template with bottom rail of head box. Mark screw holes, drill holes and screw guide arms in place.

Step 4
Slide guide runners to guide arms, unscrew bolts in ends of bottom rail of awnings and screw arms to blind. Tighten bolts with a spanner or cordless drill. Check that arm self locks when pushed up, to hold awning in position.

Step 5
Slide bottom guide supports up each guide, check that guide arms are parallel and vertical, then screw on as before.


Join the fan club

Don’t forget the humble ceiling fan! A fan can keep you 3-4ºC cooler by evaporating the perspiration on your skin and, wisely used, are a more economical option than other forms of cooling. For large rooms of about 20m2, choose a 132cm diameter fan, and for smaller rooms, go for the smaller 122cm fans. Make sure there is 300mm between the fan blades and the ceiling, and that the blades are at least 2.1m above the floor. Ceiling fans are also available with lights, too.