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Meeting Section J through passive design

Meeting Section J’s DTS provisions through passive design. By Katie Fallowfield, Senior Built Ecology Consultant, WSP Built Ecology

 

“Section J” or “JV3” are phrases which strike fear into the hearts of many in the construction industry.  What is it and why are we fearful?

Section J was integrated into the BCA (now the National Construction Code or NCC) in 2006 applying to all Class 2 to Class 9 buildings. To begin with, it was understood by few, it was onerous to many, but accepted overall. The section aims to improve energy efficiency of buildings by requiring certain performance parameters of the building envelope, glazing and services. Its intent is to reduce greenhouse gas emissions from the built environment.

One option for meeting Section J is for a project to meet the deemed-to-satisfy (DTS) provisions of all parts of Section J – an elemental or tick-box exercise.

If a project does not meet the DTS provisions, the next option is to demonstrate compliance via an alternative approach, of which there were originally three – Verification Methods 1, 2 and 3.

In 2010, the DTS provisions of Section J became more stringent. It was time for our buildings to step up their energy performance. In addition, Verification Methods 1 and 2 were dropped, leaving just Verification Method 3, or ‘JV3’.

Irving Street Brewery ModellingWhy is it so scary?

For some, Section J stops them from building what they want – large expanses of clear glass facades with minimal shading and walls with limited space for insulation. With these features, a building is unlikely to meet the DTS provisions of Section J.

Option 2, is to demonstrate building compliance using Verification Method JV3. This means difficult energy modelling, consultants fees, specification of expensive glazing…..it becomes complex!

But truthfully, a glass box with minimal insulation, no shading and no real glazing performance, is unlikely to pass via JV3.

It doesn’t need to be like this.

Traditionally, buildings are built to meet the needs of its occupants. Simply put, if the ‘glass box’ example of a building was a greenhouse and its occupants were tomatoes, a glass box would suffice, and it wouldn’t need to meet Section J.

However, if it was intended as an office, this glass box wouldn’t meet the needs of the occupants, nor would it meet Section J. Occupants would complain of extreme heat and glare, would need to wear sunscreen indoors and energy bills would be high .

Good architects and developers now realise that incorporating ‘passive design’ into their buildings is the way forward. The occupant needs are met, energy demands decrease, occupant satisfaction increases, sale and rental values can increase and, if done correctly, Section J is a breeze.

What is ‘passive design’ and how can it help meet the DTS provisions of Section J?

Passive design focuses on key features such as:

  • Controlling solar gain
  • Maximising daylight availability (this is not a contradiction of the point above)
  • Minimising heat gains and losses through the envelope

These key features all work towards optimising energy efficiency, and as a bonus, they can:

  • Maximise external views
  • Improve visual comfort
  • Promote indoor environment quality

Passive design assists in meeting the functional requirement of Section J for the building envelope.

Good passive design doesn’t always ensure the building will meet the DTS provisions of Section J. Unfortunately, the DTS tick-box exercise is a one-size-fits-all version of compliance. But as we all know, one size does not always fit all.

This is where a JV3 modelling approach kicks in. If passive design is incorporated from the outset, the chance of passing via JV3 is dramatically improved.

JV3 is the tailored version to demonstrate compliance. It’s the method used to ensure a better fit, or optimised solution for the building, particularly when considering Part J1 Building Fabric and Part J2 Glazing of Section J. JV3 allows a building which has been optimised for passive design to demonstrate energy efficiency which, in turn, meets the intent of Section J.

The DTS provisions for insulation, glazing performance and shading design operate on a worst case scenario.

For example, glazing is considered only in relation to its orientation and the proportion of the wall on which it sits. Therefore, if 100% of a wall facing in one orientation is glazed, the highest glazing parameters would apply to the glazing for that orientation; alternatively the glazed area needs to decrease. The DTS assessment does not take into account whether or not the remaining walls are fully glazed or whether they are 100% solid or a combination of both.

Using the example of Irving Street Brewery, Central Park, Chippendale, it is clear how passive design and JV3 modelling can be applied to meet the DTS requirements of Section J.

The redevelopment of this heritage listed building in the Central Park Precinct proposes a new, fully glazed façade to the north of the building, whilst maintaining the heritage building structure. If the building was to meet the DTS requirements of Section J, the fully glazed north façade couldn’t be built. The glazing proportion would need significant reduction and an enhanced solar performance,  resulting in a dark tinted glass which does not correlate with the architectural intent for the building.

The other key architectural constraint is the existing heritage structure. Insulating the external walls and isolating the steel structure to prevent thermal breaks detracts from the architectural intent and adds complexity in terms of designing out potential condensation and damp risks to the structure.

Using passive design techniques, WSP was able to identify opportunities for optimising the design of the building.  Increasing insulation levels in the new walls and the roof in combination with an innovative double skin façade to the north, allowed for a decrease in glazing performance parameters. This enabled a demonstration of compliance with Section J via a JV3 modelling approach.

In the case of the Irving Street Brewery, this passive design strategy is integrated with the operable portion of the façade and the mechanical system to enable the building to take advantage of the clearer glass installed. During hot periods, the operable part of the windows located towards the top of the façade will open to allow warm air to escape. In this way, the heat build-up in the space will be avoided. In colder months, the operable windows will close to retain warm air and the clearer glass allows for greater solar heat gain, reducing reliance on artificial heat sources.

Similarly, the hotel proposed for the Australian Turf Club (ATC) has a predominant southern façade, with suites offering race track views at Randwick Race Course. The south facing glazing therefore needs to be large and clear to promote views.

To meet the DTS requirements of Section J, the glazed area needs to be reduced in conjunction with high performance glazing. However, by optimising the passive design of the building on the remaining three sides, WSP was able to demonstrate compliance via a JV3 modelling approach and retain the essential views of the racecourse.

When designing buildings, there is no need to become focussed on prescriptive compliance design. Instead, consider the form of the building and how it might respond to the climate it is located in. A building that has been designed to take full advantage of passive design measures will provide an internal environment which is optimised for the occupants and the building function. It will have reduced operational energy costs, improved occupant satisfaction and health and most likely perform better than a building that meets the bare minimum DTS parameters of Section J. Such a building (if it doesn’t meet DTS provisions) is likely to run smoothly through a JV3 modelling approach.

 

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