Sitting at home in the summer heat, your mind may start to wander to that fancy new air conditioner.
As we spend more than ever on maintaining and improving our homes, we’re also becoming more aware of how their design and use impact on our health and society. Add to this climate change and rising energy costs.
There are many ways to reduce energy and stay comfortable (for instance here and here). Numerous reports suggest it should be possible to reduce your energy use by 50-80% using existing and available materials and appliances.
Appliance are the easy bit, and you can find the most efficient appliances using energy star ratings. But before you go out and buy that air conditioner, consider the following principles that can help you decide what you need to create a comfortable home.
Prevention better than cure
For a long time the perfect “room temperature” was considered to be around 21℃. But we now understand that as humans we like temperature variations rather than vanilla indoor environments.
As explored in Lisa Heschong’s book Thermal Delight in Architecture (1979), most of us are not looking for a beige thermal environment after all. So to start with, we need a change in attitude. Bring back the cardigan for winter and the shorts for summer!
The next point is basic knowledge about your climate zone. For instance, in Melbourne there are more heating days (159) than cooling days (35). So, if you are retrofitting in summer, remember the main annual task is actually letting the sun in in winter.
Even with climate change, Melbourne will still require heating on more days than cooling for decades to come, whereas in Brisbane the priority is keeping out the heat and catching the breeze.
So Melbourne homes need reversible sunblock. You can use plants with seasonal foliage to shade summer windows, or temporary techniques like temporary sail shades or movable window awnings can work. Plants can also cool outdoor spaces through evapotranspiration, which helps combat the growing “urban heat island” problem and makes the backyard a more pleasant place to be.
Despite some bad press over the years, insulating ceiling, floors and walls where possible remains the best way to address 50-80% of heat gains/losses. In many homes ceiling insulation is cheap and easy to fit and can even be topped up. Insulated homes have also been found to perform better during extreme weather events and are quieter, more comfortable and natural places to be.
In summer sun, black roofs are bad news. Coating surfaces can reflect excess heat. Coating technology has been employed in paint products for your walls and roofs, and is also being developed in landscaping materials for the backyard.
Single-glazed windows are responsible for 10-35% of heat gains/losses in our homes. A range of double-glazed window products is now available, or you can even get a secondary glass pane to place over existing windows.
Double-glazed (or triple-glazed) homes are more comfortable in extreme weather, and are also quieter and more comfortable. Add drapes and blinds for added temporary use to keep out sun or keep in warmth when needed.
While these preventive passive measures might seem basic, the fact is that (a) technologies, markets and pricing are changing rapidly, so it makes sense to be open to new retrofitting ideas and products; and (b) comfort remains the big-ticket item and it will only get more so as climate change affects all of our homes. Addressing this first will reduce the requirement for other technologies and appliances.
The principles of retrofitting
For the more enthusiastic, if you buy a couple of temperature loggers and place one in your main living area and one in your main bedroom you can collect data at intervals as small as one second. You can use this data to identify how your house is performing and how you are using it. More importantly, you can satisfy yourself that the retrofit you’ve just paid for has made a difference.
We’ve only covered a few focus areas in this article. There are many good options we haven’t dealt with. However, we propose three principles for any retrofit project:
- Prioritize big-ticket items (such as thermal comfort) – what do you need most and what uses the most energy? – to plan and design around your climate zone and home needs
- Prevention is better than cure – focus on passive elements before turning to appliances
- Diversity is better than standardisation – don’t aim for 21℃, aim for controllable comfort, openable windows and adjustable systems room by room. Design in easy adjustment through movable technologies such as fans, curtains, plants and shades.
With all the hard work done, it’s time to sit back and enjoy the new indoor environment, but be aware that, as with our climate, our conventions, routines and expectations of comfort are constantly changing.
Some argue for evidence of a comfort dividend, where occupants of newly eco-retrofitted homes increase their use of heating or cooling appliances (or both).
Undoubtedly, as consumption patterns change and social standards shift, we will need to adjust our eco-retrofit priorities. Homes are not just a material work in progress, but are sites of social and cultural life after all.