Pittwater Online News

How To Keep Your Home Cool During Heatwaves

Living beside the sea in a place that has worked to retain its tree canopy has its advantages during the hotter weeks of the year. Just as an umbrella will shield you from blazing sun, a tree will absorb those hot rays and provide shade to keep cooler areas around you.

Around the home

Reduce heat gain by closing drapes, shades or blinds, and use shelters to prevent direct sunlight from streaming in through windows of the house. If you do not have tall cooling trees close enough to your home to cast some cool shade, overhangs, latticework, awnings and shade cloths all work well to keep scorching afternoon sun off glass.

Reduce indoor humidity to make room air feel cooler. Minimise middle of the day showering, and cooking. If you must do these then, turn on ventilating fans to help extract warm, moist air from the house. 

Turn off heat-generating lights and appliances unless you absolutely need them. Incandescent lights, in particular, generate more heat than you might think. 

Keep the heat out of the kitchen - when it’s time to cook, opt for the barbecue instead of the range.

When the sea breeze is running open windows to allow this to filter through your home; alternatives include an oscillating fan.

No Trees = No Shade areas

If you live in an area with restricted air flow due to surrounding buildings, lots of concrete or other hard surfaces that creates radiant heat, or have a lack of trees or green breaks, the outside temperature may be hotter than that inside your home and your street may be hotter by as much as 3-4 degrees than one facing that cool ocean.

In that case you may be better shutting up your home during the hotter part of the day, drawing curtains and installing ceiling fans to create air movement. However, if your home does not have adequate insulation to keep out heat, and there is no breeze whatsoever, an air-conditioner in one room and closing off the others until a sea breeze occurs is going to be your best option for comfort and reducing energy costs. You could also shade outdoor areas around the house with plantings and shade structures to lower the ground temperature and in turn the temperature of incoming air. Even a shade cloth or large market umbrella over hotter areas will reduce the temperature being radiated against your home's walls and then inside your home.

There are also many ways you can cool your home through what is termed passive (non-mechanical) cooling, as well as hybrid approaches which utilise mechanical cooling systems. Passive cooling is the least expensive means of cooling a home in both financial and environmental terms. 

Cooling buildings:

• shading windows, walls and roofs from direct solar radiation
  
• using lighter coloured roofs to reflect heat
  
• using insulation and buffer zones to minimise conducted and radiated heat gains
  
• making selective or limited use of thermal mass to avoid storing daytime heat gains.
  

Evaporative cooling by installing water features

As water evaporates it draws large amounts of heat from surrounding air. Evaporation is therefore an effective passive cooling method, although it works best when relative humidity is lower (70% or less during hottest periods) as the air has a greater capacity to take up water vapour.

Pools, ponds and water features immediately outside windows or in courtyards can pre-cool air entering the house. Carefully located water features can create convective breezes. The surface area of water exposed to moving air is also important. Fountains, mist sprays and waterfalls can increase evaporation rates. A previous DIY Ideas page on how to install water features is archived below.

Open Design to Maximise Natural Ventilation

Heat enters and leaves a home through the roof, walls, windows and floor, collectively referred to as the building envelope.  

• Maximise the indoor−outdoor relationship and provide outdoor living spaces that are screened, shaded and rain protected.
  
• Maximise convective ventilation with high level windows and ceiling or roof space vents.
  

As those living in Pittwater know that cooling sea breeze is going to run inland from the east and south (southerlies), make sure you have windows facing in those directions that can be opened to allow cool air to replace hot air within a home. Opening a window on the opposite side will allow air to be drawn through the home.

In rooms where it is not possible to place windows in opposite or adjacent walls for cross-ventilation, place projecting fins on the windward side to create positive and negative pressure to draw breezes through the room.

Insulation

Insulation is critical to passive cooling — particularly to the roof and floor. Windows are often left open to take advantage of natural cooling and walls are easily shaded; roofs, however, are difficult to shade, and floors are a source of constant heat gain through conduction and convection, with only limited cooling contribution to offset it.

In climates that require only cooling or those with limited cooling needs, use multiple layers of reflective foil insulation in the roof instead of bulk insulation to reduce radiant daytime heat gains while maximising night-time heat loss through conduction and convection. This is known as the one-way insulation valve.

Reflective foil insulation is less affected by condensation and is highly suited to cooling climate applications as it reflects unwanted heat out while not re-radiating it in.

Roof space

Well-ventilated roof spaces (and other non-habitable spaces) play a critical role in passive cooling by providing a buffer zone between internal and external spaces in the most difficult area to shade, the roof.

Ventilators can reduce the temperature differential across ceiling insulation, increasing its effectiveness by as much as 100%. The use of foil insulation and light coloured roofing limits radiant heat flow into the roof space.

Hybrid cooling systems

Hybrid cooling systems are whole house cooling solutions that employ a variety of cooling options (including air conditioning) in the most efficient and effective way. They take maximum advantage of passive cooling when available and make efficient use of mechanical cooling systems during extreme periods.

Fans

Fans provide reliable air movement for cooling people and supplementing breezes during still periods. 

At 50% relative humidity, air movement of 0.5m/s creates maximum cooling effect; air speeds up to 1.0m/s can be useful in higher relative humidity, but prolonged air speeds above 1.0m/s cause discomfort.

Standard ceiling fans can create a comfortable environment when temperature and relative humidity levels are within acceptable ranges. In a lightweight building in a warm temperate climate, the installation of fans in bedrooms and all living areas (including kitchens and undercover outdoor areas) significantly reduces cooling energy use.

Fans should be located centrally in each space, one for each grouping of furniture. An extended lounge/dining area needs two fans. In bedrooms, locate the fan close to the centre of the bed. Because air speed decreases with distance from the fan, position fans over the places where people spend the most time. [1.]

Before rushing out and loading up with ceiling fans or floor fans or choosing an air-conditioner it would be wise to do some research and decide what your best options are and what will suit your home's needs best.

Combining using your air conditioner with your ceiling fans will circulate and draw that cold air through those other rooms and reduce your reliance on this cooling method for longer periods and in doing so, reduce your energy costs. 

Of course for residents here, opening the house as much as all your windows and doors will allow from late afternoon to early morning is beneficial if overnight temperatures fall below your homes' inside temperature, especially when that cooling sea breeze is running. 

As long as you have intact flyscreens to keep out all those wing-borne insects such as mosquitoes and cockroaches, or that eight legged version of garden-house visitor, the optimum is to make use of where you are and invite that salt air inside your home. 

1. Sourced from Your Home: Passive cooling - Australian Government. Retrieved from: www.yourhome.gov.au/passive-cooling

The products shown here are all sourced from Johnson Brothers Mitre 10 and are examples of what is available. Pop into one of their stores at Mona Vale, Narrabeen or Avalon and speak to their friendly trained staff about cooling your home. The Mona Vale store has water features as well as many other items that will assist in keeping you and your family more comfortable during heat waves.