Q: From a specifiers point of view, the level of accreditation and sourcing of timber prod ucts, especially hardwoods from old growth forests, is making timber selection difficult. Where once Western Red Cedar was the timber of choice, the collec tion of thuja plicata may not be sustainable now. Same with our old favourite tallow wood for timber decks.
My initial thought was to see what the Australian Standards have to say (AS 4707 and AS4708) but reading between the lines it’s apparent there is a huge juggling act evident in the standards to satisfy unions, industry and NGOs.
So how do you specify tim ber and feel green all over?
A: This is such a troublesome topic — more green paint has been spilled by the timber industry than any other. There is no independently recognised timber sourcing accreditation scheme that has no critics: all have groups that say 'too green', others say 'not green enough'. At the same time, there is still a long way to go before we truly understand what a sustainably managed global timber industry might look like. We have defined sus tainable practice in isolated forests, but most remain unknown and unplanned to varying extents.
The most widely accepted standard is Forest Stewardship Certification (FSC). FSC brand ing appears on an increasing range of timbers, some even being available in Bunnings. I recently purchased Brazilian Mahogony with FSC approval — which was a pleasant surprise.
FSC is an independent, sci entifically-based, audited 'chain of custody' program, where the stick of timber on the shelf car ries a unique number which is traceable back to the stump in the ground. It can take years for a plantation to gain FSC accreditation, and in the mean time Greenpeace have an interim rating guide which trades the timber as Good Wood, either excellent (use every time), or In Transition to Green (use when there are no other better options).
There are now seven Australian plantations and one native forest with FSC certifica tion, with more coming on stream. You can get more infor mation at fscaustralia.org > Find an FSC Certified Product, and greenpeace.org/australia > Good Wood Guide.
Below those two standards there are a myriad of others, but the details of how to sift through them require a lengthy article to explain. The various state forestry supply channels (such as NSW Regional Forest Agreements — RFAs) and others have been too repeatedly criticised by authoritative experts to be taken at face value.
Other marketing labels may use green looking symbols and terms, but these do not neces sarily equate to a sustainable timber product. Tasmania and Western Australia in particular, and East Gippsland to a slightly lesser extent, all suffer drastically from historically poor forest management, where the value of the forest is only measured by the cubic meter age of commercial timber that can be pulled out of it — even if that incredibly high value timber is used to make cardboard boxes for wide screen TVs, or newspapers partially read once then thrown away.
At least we want to honour the value of the tree's hard work by building something useful out of it! I'll probably find myself on the wrong end of a law suit for saying that, but I cannot say what ain't the facts.
Q: I believe that the critical working for a natural ventilation system is the ratio of ceiling height to room size volume (or floor plate size). Is there a rule of thumb ratio for each 100 mm increase in ceiling height with out using computer generated outcomes, and if so, how does the roof pitch play in this also?
A: If there is a rule of thumb, it is simply that every extra 100 mm of ceiling height above the awful minimum of 2.4m is worth grabbing! There is an upper limit, which increases with decreasing latitude. So if 2.65m is a workable minimum for Hobart, we need 3.3m in Cairns, and maybe no ceiling as such at all in Darwin! That would mean 2.7m would be good for Melbourne, Canberra, Sydney, and most points in between. Adelaide might want to be a whicker higher, as could Perth. Broome would be like Darwin. Is that a rule of thumb?
The use of software — espe cially that which models passive cooling well — can give us a lot more detailed feedback, assum ing we use it to run a series of 'what ifs'. This is how such soft ware should be used, like all the second generation tools that comply with the new NatHERS Protocol, such as AccuRate, BERS and probably FirstRate, although I have yet to test it.
As to roof pitch, this also needs to be considered in con junction with ceilings: to rake or not to rake - that is the ques tion. The warmer the climate, the more reason to rake. Of course, roof and ceiling insula tion principles should be applied in the correct way in each climate zone. Raking the ceiling may therefore not appear to be 'the right thing to do' in cooler climates, but if the insulation is correct, and the floor levels and layout of the building is designed to take advantage of the rising ceiling lines, then a great result can be obtained. Like so many things in life — it’s not what you do, it's how you do it!
Dick Clarke is principal of Envirotecture, which provides design and consulting services. He is an accredited building designer with 30 years experience, focusing exclusively on ecologically sustainable and culturally appropriate buildings. Clarke is director of sustainability and past president of the Building Designers Association of NSW.
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