Solar vs. Facade: The Offset Dilemma 1

Thursday, January 14th, 2016
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With the Australian solar PV industry getting so little attention these days, we need every excuse to legitimise the use of low carbon strategies in commercial building projects.

While solar contribution can admittedly be low – in the 0.5 to three per cent range for a typical office building’s baseload – improvements in technology efficiency, further integration into façade design and greater industry confidence on the delivery side will add fuel to the solar conversation. We have so many reasons to be global players on the PV market, but PVs continue to take a back seat to the pro-coal agenda.

That being said, over the last year an increasing trend has arisen which needs industry standardisation and a greater level of clarity moving forward. This trend brings about questions regarding supporting solar on larger commercial projects. In short: should we be pushing for solar technologies as a ‘trade off’ against façade and fabric performance to meet minimum Section J compliance?

Today, we head down an energy efficiency compliance pathway typically via an energy modelling route (JV3) that stipulates ‘trading’ as the opportunity to provide flexibility and varied design responses.

To put it in concise terms, this works by running a reference model based on standardised compliance numbers and then compares two further models to optimise mechanical services in one and façades and fabric in the other. It’s simple enough: three models all up, and both mechanical services and façades and fabric both need to surpass the ‘performance’ of a reference model to meet minimum compliance.

More often than not, this is where the minimum performance for façade and fabric is challenged while the minimum performance for mechanical services is a breeze, as performance for the latter is based on older lower performance technologies. Indeed, the industry tends not to run the mechanical services model these days as the minimum performance numbers are almost guaranteed to be met (in most cases) and thus is a bit of a pointless exercise for many unless aiming for Green Star points or other.

So, if we cannot quite meet our façades and fabric performance (i.e. it cannot surpass the performance of our reference model), then do we play the trading game with solar technologies against the façades and fabric? Is it right to increase cooling and heating loads via lower performing façades and fabric design through the addition of a tack on PV solution?

Whilst energy efficient services are great, the inherent efficiency and comfort gained by a building’s façade and fabric must surely be considered more ‘sustainable’ based on its intended life cycle and passive principles alone. Services may change over time and need to be maintained to perform, but façades and fabric performance deteriorate over a much longer time period – at least two to three times longer than services.

Referencing the ABCB publication Using On-Site Renewables and Reclaimed Energy Sources (2011) and having spoken to a very helpful ABCB technical advisor, I can say the following holds true:

  1. It is technically feasible to trade off any over-performance of services against under-performing fabric under exceptional circumstances
  2. This trade-off is against the general intent of energy efficiency provisions to emphasise fabric performance
  3. Any alternative solution other than JV3 works. The three modelling solution with JV3 aims to prevent this trade-off, and so JV3 cannot be used

The jury may still be out, but with this official guidance, the process seems slightly clearer. While the vagaries of what an ‘exceptional’ circumstance can be debated until we see the next release of Section J in 2019, the guidance calls for an alternative solution other than JV3. It seems likely that most building surveyors would not raise an issue on the subject.

Is it time we put submitted a Proposal for Change to the ABCB to clarify this issue or is trading solar technologies with façades and fabric to meet minimum performance acceptable for better buildings?

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  1. Greg Goldbltt

    Darren, as a relative layman, could you please offer clarification of 'fabric' with regard to your article.
    Assuming these are Architectural Textiles