I am hearing a lot about great sustainable buildings, however in 99% of all cases the articles fail to deliver some hard fact, ie numbers. What is sustainable about them, what is their water use, energy use. What materials have they used? What great features were put in. What sets it apart really?

GreenStar NZ is a great tool for rating and comparing buildings. However I struggle slightly when people call it benchmark. It is a tool that enables interested persons to compare buildings and building efficiency, not give an indication whether a building is necessarily great or not.

Green Star is a comprehensive, national, voluntary environmental rating scheme that evaluates the environmental attributes of New Zealand’s buildings using a suite of rating tool kits developed to be applicable to different building types and function.

(About GreenStar)

GreenStar does not do LCA (Life Cycle Assessment), a product with recycled content may not be that great as a product without recycled content if the content was actually renewable, just as an example. Having some downcycled content in a vinyl floor covering may still not be as good as a solid timber floor and a recovered floor covering may or may not be as good as a new timber floor – that would depend on how much energy went into the recovery and reconstituting. Who can tell? Really, noone.

I refer to my age-old article about green building materials. Unfortunately still up-to-date.

It should also be noted that GreenStar give you two options for certification: Design and Built.

Design gives a theoretical rating and built gives the actual measured performance. You can find quite a lot of articles on the web about the difference and some buildings not living up to their claim.

The natural ventilation system is expected to operate about 60% of the time, reducing air-conditioning use by 40–50%.

Mark the word “expected”.

Features that earned it the 5 Green star rating include water-efficient fittings and rainwater harvesting.

Do not most rural properties in  New Zealand work that way? I have a water tank, I have low water usage fixtures, low flow showers, a front-loading dishwasher. I use zero town water. So why is the above extraordinary?

ASB North Wharf needs a lot less artificial light than typical buildings due to a rooftop reflector.

How much less is much less? How can we quantify it and conceive as a great idea worth pursuing? Are there maybe other options that would be better or more cost-effective? I am not saying this is no good, all I am saying is that I am missing proof of the statement.

A screen shading system on the building’s north façade reduces heat from the windows and provides 65% of the interior shading.

Sounds great. However, does that mean it uses less air conditioning? Probably, so the resulting question is how much energy is the building using per m2 per year compared to other buildings?

This, combined with efficient space utilisation, has seen ASB cut electricity use by 50% compared to the previous head office.

50% less is a pretty good number, however is that per building, per employee or per m2? You see, one can put this against a lot of different key indicators. Ultimately I would like to see this in comparison to employee, after all maybe they are using more space per employee, which may not necessarily be sustainable either. Efficient use of space and land would be a performance indicator too.

via Banking on green | BRANZ Build.

Unfortunately there does not even seem to be a register of GreenStar certified buildings, their rating and some actual data. So if you are interested in the projected energy or water use of a building, you most probably have to contact the NZGBC.

While this all may sound like I am trying to make GreenStar bad, this is not necessarily the case. I would just welcome more transparency in claims so we can actually do what the tools was supposed to do: being able to compare buildings and their inefficiencies, learn from it and pick the best working bits in order to develop them further. Comparing stars alone will not take us any further.

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