Design for climate
Sustainable housing is often promoted in the mainstream market as an easy fix; add a bunch of systems on to a building that offsets the power and water usage, throw in some ‘family friendly' features and you get the Big ‘S' badge. Only a handful of companies in the mass market are genuinely promoting responsible material choices and reassessing the scale of buildings, and fewer still, are really getting to the ‘nitty gritty' of passive design and helping their clients understand and build homes that actually work in our climate. Consumers need to be empowered to be a part of the process from the beginning, even if it's purely for the financial reason of not ending up with an energy-guzzling white elephant in future years.
This article gives three very basic starting points for good passive design.
- Orientation
- Floor plan
- Eaves and windows
A good builder or designer will be able to alter a standard design or juggle the orientation and layout to suit awkward blocks so these basic principles are met.
1. Orientation
The golden rule of passive design is "face the sun, not the street". This means lining up your floor plan so that the long axis runs East-West with your living areas facing true north, wherever possible (true north varies for every location in Australia, and on the Sunshine Coast is about 10.50 west of magnetic north. Note: compasses indicate magnetic north). This is an important distinction, as it is the ‘true' axis of the sun's yearly movement through our sky.
What a long east-west axis does, is make the ‘short' walls of the house face east and west, where the sun hangs low in the sky, in the early morning and late afternoon in summer. By heavily insulating and shading these short walls with external screens or plants, and by having few windows, the inside of the building is protected from heat gain during the warmer months. (If you have children's bedrooms facing west with large windows and minimal shading, you are already experiencing the effect of bad design during summer - kids, early bedtimes and hot rooms don't mix well).
Secondly, you cluster living areas to true north, so that the sun can be used to warm the most used spaces during winter and shaded out in summer. If your block does not allow a long east-west axis, it's important to reorganise the floor plan so that your main living areas have glazed windows or doors facing true north, with correctly sized eaves, to achieve the same effect. (See following sections).
More info: Case Study 7.1 Modifying a Project Home is a great example of how a few minor changes to a basic plan can make huge improvements to how the home works.
2. Floor plan
Designing a plan that is ideally one-room wide throughout, or with operable or louvred internal walls, allows breezes to cross from one side of the building to the other and cool and ventilate rooms naturally. Like water, air likes to take the most direct path, so for good cross ventilation, you should place openings directly opposite each other. A window in one wall, without a corresponding opening opposite, won't do a lot to draw air through the room.
Cluster living areas that need heating in winter, to the north, and use ‘utility' rooms such as the laundry, garage and bathrooms in the southeast and southwest corners to buffer the hot morning and afternoon sun in
summer. Obviously this is a very prescriptive approach - there are a million ways to design spaces that perform these same basic functions.
3. Eaves and Windows
On the Sunshine Coast, eaves that sit out roughly half the distance of the height of the glazed area below them on the northern side of the building, will allow warming sun into the living areas during winter months when its travelling low in the sky, and keep it out during summer when its passing higher overhead. Coupled with good roof insulation and deciduous trees or vines on a pergola across the north face of the house, the right sized eaves will maximise the natural heating and cooling of internal spaces without the need for mechanical systems.
Glazed areas (windows and doors) should ideally be equal in area to about a fifth of the floor area of the room they are located in, on the northern face. This way during winter, enough sun will be allowed into a room to effectively heat it.
Ample eaves over windows will also allow windows to be open during storms in hot months, when ventilation is important.
Short east and western walls should have as few windows as possible (other than small ones to facilitate cross ventilation) and be shaded all year round, either with vertical shutters, screens, or vegetation.
Southern windows should be kept to a minimum, to avoid too much heat loss during Winter (from the shaded, cold side of building) - again, just enough to provide good cross ventilation.
When choosing windows for the side/s of the house that receive the cooling summer breezes, (usually northeast to southeast) think about side-hung or pivoting window frames that will act as a funnel or sail, to catch breezes and direct them into the house, rather than sliders (that cut off half the area to breeze) or louvres (effective, but only open straight-on from the wall - and they don't have the ‘funnelling' effect).
There are literally hundreds of small things you can do to manipulate sun and air movement around a home and make a massive improvement on its energy requirements.
For more detailed information, visit the yourhome website or get weekly eco-design tips by email from Jo's website by clicking here.
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