Is VURB a loophole to avoid delivering energy-efficient homes?
Willow Aliento | 12 October 2017
An article in The Conversation earlier this week claimed the Verification Using a Reference Building method for energy efficiency compliance of detached residential dwellings was a “loophole” allowing builders to avoid complying with the six star standard.
Naturally, The Fifth Estate had to ask, “Is this so?” and fact-checked the claim with some experts. Another claim made in the article, written by Curtin University PhD candidate Saskia Pickles – that raising building standards from 4.5 stars to 6 stars could “typically cost tens of thousands of dollars” – was also put under the microscope.
Director of Team Catalyst PC Thomas has been working with the Australian Building Codes Board on the VURB method for compliance with the minimum mandatory energy efficiency requirements for detached dwellings.
Thomas says the VURB method has been used for some time for commercial buildings, but is relatively new in the residential space.
NatHERS has been the main compliance pathway for houses for many years, he says.
With either pathway, there is “potential to get outcomes that are poorer than is typical of 6 Star NatHERS,” he says.
This is due to the fact the compliance requirements of the ABCB cannot enforce the performance levels of the NCC – unlike NABERS, for example, where performance verification is part of the tool. That said, Thomas notes that in the commercial building sector, unless an office building is being sold or leased (and 1000 square metres or more), there is no requirement for it to have a NABERS rating, which is triggered by Commercial Building Disclosure (CBD) legislation.
The bottom line for homes and other habitable buildings is that if is delivered in a manner that does not meet the NCC performance requirements – it is illegal.
“Compliance is a very big issue for both commercial and residential buildings,” Thomas says.
The ABCB puts out the code – but unless someone goes out to check a building is compliant, there is no verification.
“It is unfortunate,” Thomas says, “that code compliance is a state and local government authority responsibility, but the ABCB gets blamed for non-compliance.”
It also highlights the variations between states and how NatHERS is used.
“In some jurisdictions people want a 6 star building, some want an 8 star, and in some you can comply by having 5 star with a balcony and a ceiling fan.”
Whether VURB is any better or worse than NatHERS really comes down to what compliance level it is being compared to, he says.
“There is no common basis between the states.”
This again is different in the commercial sector where NABERS makes things much more straightforward.
He says in Western Australia there is a lot of discussion around people using the VURB method, and whether it is being used appropriately to achieve compliance.
The NCC sets out what must be done, but some builders may diverge from the specifications of a design that would meet VURB requirements in order to achieve cost reductions.
That kind of violation of the compliance process is not the result of VURB, Thomas says, it is “an indictment of a small percentage of builders who are unscrupulous”.
Like any system, VURB can “be gamed” to make building a house cheaper with a commensurate thermal performance penalty.
All compliance systems are equally susceptible to gaming, Thomas says.
“It is not an issue with the systems; it is an issue with how people are applying the systems.”
Air leakage a big issue compromising performance
One of the issues that has been repeatedly identified as compromising the performance of a home is air leakage.
Thomas says that the concept of air blower door testing to assess air tightness is good, as there is still not a lot of data about how leaky or not our homes are.
“So should we aim for the Passive Haus standard?”
As a minimum, we “should do all those commonsense things”, such as tape around windows, and avoid gaps between the edges of construction, or lay chipboard down before laying floorboards to minimise air leakage.
“We have problems that are not being addressed because of how our construction systems don’t deal with moisture and condensation in our milder and moderate climates that are way more important than tightly sealing up an Australian house to perform to European winter requirements,” Thomas says.
The problem isn’t VURB; it’s its application
General manager of the Australian Building Codes Board Neil Savery says his office’s investigations indicate the problem is not the VURB method, but the application of it.
An example was given in Pickles’ article of a brochure from an engineering firm, Structerre, which promised to save builders thousands by using the VURB method. The Fifth Estate sent the article to the ABCB for comment.
“The Structerre example, which is non-compliant with V126.96.36.199, illustrates that this is a compliance problem,” Savery says.
NOTE: 17 October 2017 – Structerre has contacted The Fifth Estate to say that there was a typo in the original case study that transposed the results for heating and cooling of the building.
The reason it is non-compliant with the relevant NCC 2016 section – V188.8.131.52 – is that the heating load of the proposed building (60.3 MJ/sq m) is more that the heating load allowance of the reference building (43.0 MJ/sq m), he says.
When applied correctly, that is, when a compliant calculation method and correct inputs are used, V184.108.40.206 is a legitimate option for complying with the NCC energy efficiency provisions for housing.
Savery says that while not preventing the use of NatHERS software, V220.127.116.11 was included in the Building Code of Australia in 2003 specifically to allow the use of other calculation methods.
“There are four basic pathways to compliance with the energy efficiency provisions for housing in the NCC: the elemental provisions [Deemed to Satisfy provisions]; use of NatHERS software to achieve the specified star rating; the reference building verification method (V18.104.22.168); and other Performance Solutions.
“V22.214.171.124 allows different types of calculation methods to be used on the proviso they meet the criteria specified in subclause V126.96.36.199(c).
The ABCB published an advisory note on the correct use of V188.8.131.52 in late September 2017 to assist builders with compliance.
Savery says it is a matter for the building approval authority or certifier to determine whether the calculation method meets the criteria in subclause V184.108.40.206(c) and also whether all the modelling criteria in V220.127.116.11 have been complied with.
The ABCB is currently reviewing the relevant section as part of a general review of the energy efficiency provisions for the 2019 version of the NCC.
“The review is considering changes to strengthen the technical provisions underpinning V18.104.22.168 to ensure buildings designed using this compliance pathway achieve the desired level of performance.
“There is no intention to reduce the number of compliance pathways in NCC 2019.”
Public consultation on the NCC energy efficiency provisions including potential changes to V22.214.171.124 is due to commence in February 2018, as part of the overall NCC 2019 consultation process.
Now about that costs claim
It is a regular feature of discussions on raising standards for homes that it will increase costs. However, the Regulation Impact Statement for changes to the BCA in 2010, where the standard was raised from 5 star to 6 star, does not show proof of this.
The RIS by the Centre for International Economics found that the proposed thermal performance and lighting provisions alone would have an impact in terms the net cost of about $2400 for a typical house, and a net benefit in terms of reduced energy costs of about $6400, depending on the compliance pathway and location.
Gap between design and as built as wide as the Grand Canyon
Envirotecture principal Dick Clarke also dismisses the “it costs tens of thousands of dollars” to go from 4.5 star to 6 star claim.
“It depends on the base design,” Clarke says.
By starting with a fundamentally good design, and getting things like orientation, shading and insulation right, there is no reason an efficient home should be an expensive one.
“But if you have a bad design, you can throw money at it all you like and not get a result.”
The big issue Clarke sees is the performance gap between the design, which is what gets rated for energy and thermal performance, and the as built result.
“In places that is wider than the Grand Canyon,” he says, recommending a compliance regime with “real teeth” that checks the as-built outcome.
Despite the Building Designers Association, ASBEC and others trying to get the states to step up on this, Clarke says there has been very little movement.
Queensland is starting to make some traction in the space, he says, but they are starting from way behind.
One of the reasons many builders don’t care if the end product is non-compliant is that, unlike an auto manufacturer, for example, there are far fewer companies with high reputational risk involved.
“The leaders, for example MIrvac, are trying to have standards, but most builders, they’ve got no reputation to be damaged if there is a performance gap,” Clarke says. And it is not until “many years down the track” that a home owner might realise the gap exists. And when they do, he asks, what levers are there for the home owner to pull to get redress?
The consumer laws needs to be able to “get its teeth into shonky companies”, Clarke says, though he also thinks there may be builders unaware they are creating a performance gap.
“They are just doing what they’ve always done – which we know doesn’t work.
“What support is there for them to improve?”
In terms of VURB, Clarke says there has been “a lot of consternation” about the reference building from designers and others.
“And the ABCB has acknowledged that.”
Increasing performance – but what about verification?
Envirotecture director Andy Marlow says some of the early proposals for changes to the NCC in 2019 include adding an air tightness requirement for the reference building of 0.5 air changes an hour.
“That’s better than Passive Haus,” he says.
The air tightness assumption is the basis for the reference building’s energy performance – but here’s the rub. Marlow says there is no proposal to add verification via air blower door testing to ensure that standard is being delivered.
That could see VURB become a loophole as the model will give “awesome results” but there’s no testing of the end product.
“They should make it a legal requirement to test the building,” Marlow says.
The proposed NCC 2019 is also low on specific detail, he says.
“The code uses fluffy terms, like phrases around ‘the building should be sealed’.
“They are just motherhood statements.”
Blower door testing is the only way to be sure, he says.
“At the end of the day, you need a metric.”
It would also get around another problem – while the code might talk about sealing around doors and windows, this is hard to inspect once the architraves have been put in place, Marlow says.
Thermal performance could be the next cladding scandal
He believes we need to consider the performance of homes as a safety feature.
“Thermal comfort is also a safety issue [as well as an energy one].
“It’s a resilience issue. When the power system collapses [during a heatwave], your ability to survive the shock is dictated by the quality of the building fabric you are sitting in.”
Aside from air leakage, other problems can include poorly detailed insulation and poor quality building wraps that result in condensation issues.
“There is a link to be made between the issue of fire safety and cladding and the thermal performance issue,” Marlow says.
“With the cladding, there’s been a big backlash about who will pay [for rectification]. We will have the same thing with thermal performance.”
He says the states budgeting for enforcement and compliance around cladding also need to be thinking about how much they have budgeted for condensation and poor thermal performance issues.
None of the rating systems are perfect in terms of ensuring the outcome.
“It’s hit and miss with everything,” Marlow says. “The ratings are relying on everything being good – but rarely do the stars align.”
In terms of building, he says achieving a compliant home that performs well doesn’t mean the workmanship has to be exceptional.
“It just has to be competent. Just do it properly.”