How to Weatherproof Your Granny Flat for Summer

A granny flat is like any other building when it comes to energy usage. In hot climates, air conditioning can account for a big chunk of your household energy costs, so unless your granny flat is energy efficient, you will be spending a lot of money keeping it cool in the summer months.

Factoring cooling into the design and build of your granny flat is the best way to keep your energy costs down. But even if your granny flat is not new, there are still things you can do to cool it for less and this article looks at some of those ways, along with some energy saving design tips.

Design ideas for the coolest granny flat on the block

There are a number of features you can incorporate into the design of your granny flat that will help to keep the temperature down as well as your costs. These include:

• Highly reflective roofing to help deflect excess heat. A variety of spray on heat reflective coatings are now available on the market.
• Well insulated floors, walls and ceilings to prevent heat from penetrating inside on hot days. Reflective insulation is the most effective in hot climates.
• Air vents that capture and circulate airflow to keep the roof cavity cooler.
• Double glazing to keep cool air in and prevent hot air from entering through the windows. The vacuum between the two panes of glass prevents heat energy from passing from one pane to the other.
• Windows and doors aligned to allow cooling breezes to flow through the house.
• Slight elevation of the home to catch breezes and allow cool air to circulate underneath.
• Eaves on the roof to shade windows in the summer (particularly those facing west).
• An open plan internal layout to help facilitate ventilation.
• Security screens on all windows and doors to allow safe, effective cooling at night.

As well as the design of your granny flat, the way it is positioned on your block can also contribute to efficient cooling in summer. Ideally, if it is an elongated building, one of the longer sides should face north, with the shortest side exposed to the west, which receives the strongest radiation from the sun during the hottest part of the day.

Ways to keep an existing granny flat cool

If it’s too late to influence the design of your granny flat, there are still plenty of ways to make it cooler in summer, without resorting to expensive air conditioning;

• Plant large trees for maximum shade in summer and smaller trees, shrubs and vines to minimise heat on the exterior walls. Plant alleys of trees and shrubs to funnel the natural air flow and channel breezes into the home.
• Paint your roof a lighter colour to reflect heat rather than absorbing it.
• Choose cool interiors such as tiles instead of carpet and blinds instead of drapes (apart from block-out drapes on west-facing windows).
• Invest in some indoor plants, which lose water during transpiration and help to cool your interiors.
• Install adjustable artificial shading such as pergolas, shutters and retractable awnings (these can be adjusted to suit the angle of the sun during the day).
• Keep window coverings closed during the hottest part of the day and open up at night to let the cooler air in.
• Avoid waste energy heat generation by using energy efficient lighting and appliances and natural lighting where possible (i.e. install a skylight or light tube).
• Use stove top, bathroom and laundry vents to dump hot air from cooking and washing outside.
• Use ceiling fans to circulate breezes when you open up (a fan costs much less to run than an air conditioner).
• Set your ceiling fans to rotate counter-clockwise, so they push cool air down towards the floor.
• During the heat of the day, close off rooms not in use and focus your cooling efforts where they are needed most.
• If the climate is humid, invest in a portable dehumidifier to help remove excess moisture from the air.
• If you must run your air conditioning, make sure it is set no higher than 25C, as every degree higher adds 10% to your energy bill.
• Consider replacing any air conditioning unit older than 10 years, as a new more efficient model could easily halve your energy usage.
• If you have a deck, adopt a more indoor/outdoor lifestyle and cook on an outdoor grill in the evenings to avoid heating up the house with the oven.

A granny flat can be many things to many people. It can be guest accommodation, a study, an office, a studio, a teenage retreat or a permanent home. And whatever use you put it to, there’s no reason why it can’t be comfortably cool in summer without paying a fortune in energy bills, simply by incorporating practical design features and good site orientation and adopting sensible, cost-effective methods for keeping the heat at bay.

Ask the experts

At Titan, we have plenty of experience helping customers find the perfect guest house or granny flat for their needs, as well as a huge range of options, price points, and features to choose from.

If you’d like to contact us, you can get in touch by calling 13 27 36 during business hours, or through our online contact page.