Q: Orientation can be crucial to designing a building with great pas sive design strategies. What big and small things can I do on sites where optimum orientation is limited/restricted?
A: It is very important to recognise that only a minority of residential lots have what we might call 'perfect ori entation'. In NSW, a survey of solar access to residential lots was con ducted by SEDA (NSW Government agency, now defunct), which found only 35 per cent of lots enjoyed 100 per cent solar access. This is likely to be higher in other states with flatter terrain, but to my knowledge, has not been mapped in any systematic way. SEDA's mapping showed that around 30 per cent of lots might have little or no useful solar access at all, at least in a way that allows clas sic passive solar design principles to be applied. That leaves another third somewhere in between.
Therefore, we must approach each building uniquely — starting with a thorough appreciation of the site. This is where my continued criticism of project homes that are not tai lored to the site springs from. In tropical localities, solar access is something to hide from all year — this question does not apply to those. If there is no useful solar access to north facing glazing, there are a number of alternate strategies we can draw on, each increasing in cost and complexity according to the severity of the problem. The cost of these is normally more than offset in the discounted cost of the lot — in most cases, north facing lots will be priced higher than south, all other things like views being equal.
The first rabbit we might pull out of the design hat would be to bor row the solar access from somewhere else on the building, like the roof. Does a site analysis show that the roof would get mid-winter sun? If so, for a few thousand dollars you can use simple solar-thermal air heating systems like the Sola-Venti to bring heat inside whenever there is heat in the sky.
Such systems are limited in the ability to heat in cloudy or cold con ditions, and for the same cost as ducted air-conditioning, you can design solar-thermal hydronic heat ing systems which heat high thermal elements within the core of the building (e.g. floor slabs, walls), thus storing heat for days or weeks. These can have gas boosting and be incor porated with the domestic hot water system to improve economy. The cost of pumping the water is negligi ble, so these can be considered 'de facto passive design'.
If there is no winter solar access at all (and we are now talking about 5 per cent of lots), ground loop heat pumps can be used. These use a modest but measurable amount of electricity, so need a renewable source for that somewhere, presum ably not on the building (or hydron ics would be more cost effective).
The cost can be in the many tens of thousands of dollars, but any lot with such a solar deficit should have been cheap to buy in the first place or have such spectacular views that the budget is big enough to cope in any case. And any client who is spending big bucks should be on 100 per cent accredited GreenPower as a matter of course — it’s not as if they can't afford it.
Dick Clarke is principal of Envirotecture, which provides design and consulting services. He is an accredited building designer with 30 years experience, focusing exclu sively on ecologically sustainable and culturally appropriate buildings. Clarke is director of sustainability and past president of the Building Designers Association of NSW.
Are you in a design quandary?
Send your questions to stephanie.mcdonald@reedbusiness.com.au to have them answered.
