A few weeks ago, I spent a sunny autumn Saturday at a local sustainability field day which included some interesting presentations about building a house using passive design principles.
Passive design principles stem from the Passive House movement developed in Germany in the 1980s. Passive house design offers a way of designing and building homes that are low energy. Certification is based on performance in that the outcome is key rather than the specific materials used in the build.
Passive design principles focus on site orientation for passive heating and cooling, thermal mass and insultation, shading, glazing and ventilation. The key is to minimise unwanted heat gain and loss in the home.
The Australian Government has a website – YourHome - which includes an incredible amount of detail about building a passive house and some ideas for renovating or extending using passive house design. There are even some model designs that suit different climate zones in Australia.
I live in Climate Zone 7 – cool temperate – so I read the information for that zone.
Australia Climate Zone 7 – cool temperate:
In this zone we have four seasons, hot summers and cold winters. Temperatures in spring and autumn vary – in some years it feels like summer is going on forever and autumn coolness can’t come soon enough. We can also get early spring weather in August.
According to Your Home: “The main aim in this zone is to reduce the need for heating in winter, but also achieve thermal comfort in summer. Designs with large north-facing windows and double glazing, together with appropriate thermal mass, are recommended to increase solar gain.”
In terms of designing furniture layout the website recommends that we “Design furniture layouts to minimise exposure to convection draughts.”
There’s not much more detail on furniture layout than that. There are links to Liveability and Accessibility standards which are helpful. But I wondered how you might design an interior layout using passive design principles for some of the types of existing houses in this climate zone. Older houses in this area are often built of timber and sited on stumps. Not all of them face north. Many are poorly insulated.
In this blog post I’m focusing on how these principles can be applied to the interior design of the home. I’m particularly focusing on furniture layout following passive design principles.
Elements of the design that impact on passive heating and cooling:
A building with high thermal mass can help to passively heat the house, reducing the need for additional heating sources – which would ordinarily be essential in a cool temperate climate.
Thermal mass needs to be considered along with orientation, insulation and glazing. You want to make the most use of north facing walls and glazing and minimise external wall areas facing east and west. A lot of older houses don’t do this so it can be a challenge to manage the heat gain and loss. But there are things you can do to follow passive design principles in older houses.
You can start with providing shading in summer from trees that drop leaves in winter, creating appropriately sized eaves to produce enough shade - depending on the angle of the sun, and using sunshades over windows. You can also include ventilation that adjusts according to the seasons, helping to minimise heat gain in warmer months and allow for heat gain in the colder months.
Dealing with draughts:
In a cool temperate zone, you need to design furniture layouts that lessen the exposure to convection draughts. This occurs when air releases its heat to cooler glass in windows and sinks towards the floor. It’s why you can feel cold in an otherwise warm room because you’re experiencing a cool convection draught near a cold window.
You can minimise draughts by creating effective seals in the first place which a passive house design will work to achieve during the design and build of the house.
But what if you’re house was not originally a passive design house? Older houses are particularly leaky, especially if they are built on stumps – like mine is. We get a lot of draughts and that makes improving comfort year-round a challenge. One of the main things you can do with an older timber house is make sure the windows are airtight.
And there are things you can do to minimise draughts and heat loss in winter while effectively protecting the house from summer heat gain, ensuring air flow to keep the house cool.
Furniture layout:
You can ensure air flow through the house, by designing a layout that results in keeping the larger, heavier furniture from blocking the flow of air. And to keep the house warm you can move furniture away from heaters and vents.
Window treatments:
You can insulate the window and/or window frame. Heavy curtains and a pelmet will also provide an effective barrier to the cold and keep heat inside. Opening the curtains during the day in colder months will also help to heat the house. In warmer months you can close them or use lighter curtains and a block out blind and external shade to keep the heat out.
Impact of heat and cold on furniture & fabrics:
Direct sunlight on furniture and fabrics can bleach the material. A blockout lining will protect your curtains from the direct impact of the sun. Sheer curtains can also filter sunlight coming into the house for those times when the curtains are open. External shading will also help. Keeping furniture away from direct sunlight and swapping out covers regularly helps to ensure that any exposure is spread more evenly.
Cold weather can also affect furniture and furnishings. Some fabrics, including otherwise strong synthetics, can crack in extremely cold temperatures. Over time, repeated cold temperatures – or rapid changes between warm and cold - can cause degradation of fabrics.
Leather also needs to be protected from damp conditions, so it doesn’t discolour and develop mould. Controlling humidity, condensation and airflow will help to prevent the build-up of moisture in which mould thrives. Keep furniture, carpets and rugs away from windows and wet areas.
Wooden furniture expands in warmer temperatures and contracts in colder temperatures. Over time this can lead to warping. As humidity drops the level of moisture in wood decreases. Keep wooden furniture away from heat sources and out of direct sunlight. Wood can dry out in cold weather, so it makes sense to clean and wax these pieces in autumn as well as spring.
Flooring, carpet, rugs and draught stoppers:
Vinyl, linoleum, rubber and cork flooring provide good insulation against cold temperatures. Carpet and rugs will help to stop draughts in older houses with wooden floors and poor under floor insulation.
Draught stoppers also make a difference where short doors, uneven flooring and gaps at the base of doors and windows if letting in cold air. So maybe I should do a post on draught stoppers?
Floor plan - room layout:
Hot air rises so it makes sense to avoid high ceilings in houses in a cool temperate zone. But you will find raked ceilings in cool temperate zones so how do you make heat sink in cooler weather? If you have a ceiling fan you can adjust it for winter weather.
According to Fans Online, your ceiling fan should have a switch to change the direction of the blades. In reverse mode the fan rotates clockwise and at low speed will create an updraft that pushes the hot air downwards.
Ideally you would also have airlock spaces at the front and rear entrances and between floors. This can be a challenge if your front door opens straight onto your living space. Options are to extend out from your front door to create a new entryway, or to enclose your existing porch, or to carve out the space in your living room. The same applies to the rear entrance if you want to create a mudroom or laundry space that doubles as a rear airlock.
Room and window size affects furniture and storage:
Many houses in cool temperate zones are configured for large, open plan spaces, with tall or wide picture windows. This can impact the arrangement of the furniture if you’re trying to keep pieces away from windows and out of draughts. You also need to consider the amount of clear space available for people to move about the room. Australian Standards for liveable housing recommend clear circulation space of at least 2250mm diameter.
The size and location of storage is directly impacted by the location and size of windows and doors. Keeping storage low can help you to organise the room in zones depending on usage and provide easy access to a range of people with different levels of mobility.
Living in an older house doesn’t mean you automatically miss out on the benefits of passive design. These principles are useful and practical, though they may require some effort to improve the state of an older home.
If you want to see it in more detail, you can download our furniture layout for an older climate zone 7 from our Downloads page.
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