Who Benefits From VURB Method?

VURB method shows promise where:

Do I need VURB or Star Rating?

Whenever you are building a new residential dwelling or undertaking a major extension or alteration to your existing house, you’ll have to obtain a building permit from your governing council. In the process, you may come upon some difficulties regarding energy efficiency compliance for your development. Difficulties emerge from the high cost of building insulation and/or glazing to comply with the code. This includes, for instance, installing double or triple glazed windows or adding insulation to an existing wall.

So how do you overcome this problem? or in a better sense, how could you get your building permit while reasonably reducing your construction costs? VURB is a method proposed by NCC Vol 2.0 as a Performance Solution method of compliance that may suit your project condition.

Can you use VURB for commercial buildings?

Yes, and No! VURB is a term NCC uses as an alternative solution for residential buildings (Class 1 buildings to be more accurate). For commercial buildings, NCC refers to an alternative solution called JV3 modelling which is similar to VURB with fewer restrictions and easier compliance.
Click here for more information on NCC building classes.

FACT: For residential buildings, NCC doesn’t allow the use of onsite solar electricity to offset electricity demand and CO2 reduction. However, for commercial buildings, NCC allows the use of onsite solar electricity generation or any other renewable solution to offset CO2 emissions associated with the building energy demand. For a commercial building, it also allows electricity and gas reduction through the use of better than MEPS certified equipment to assist with energy compliance.

What are all options to an NCC energy compliance for a residential building?

There are three ways to demonstrate energy compliance for your residential building:

• Elemental provisions: there exists a set of prescriptive provisions for insulation of building fabric, glazing thermal performance, building sealing and air movement. The only drawback of this approach is that it is very rigid; therefore, you cannot change any of the required provisions. This approach is generally called DtS elemental provisions.
• Star rating: this method is another DtS method of demonstrating compliance for energy efficiency under NCC. This method considers a building is deemed to comply with NCC energy efficiency provisions, provided the building obtains at least 6 stars from one of the NatHERS accredited tools.

CONs of above DtS approaches: The outputs of the above DtS approaches are proved to increase the cost of construction. This is certainly true for buildings with large floor areas or a large ratio of glazing to floor areas.

• Verification Using a Reference Building (VURB): this method allows for a more realistic energy modelling of a building. The energy assessor undertakes VURB through an energy modelling software capable of analyzing the energy demand of the house in an hourly manner. Due to this hourly analysis and the various realistic inputs from the actual house, the results of this method (if done professionally) are deemed to address a meaningful energy demand of the house. In this approach, different elements of the house (e.g. windows and roof) are integrated in a way that the whole building is assessed holistically.

Take the example below from our past experience, using this method:

What are the PROS of VURB?

Reduction in construction costs (especially glazing):

Energy modelling tools account for heat stored or released from the ground:
The soil beneath the slab works like a thermal battery that stores and discharges heat from the house. Therefore, it has a great capacity to offset the heating or cooling demand of the house. Thermal mass is more accurately considered in VURB method. Hence, buildings with a slab on ground have a higher chance to have a cheaper construction cost with VURB.
Holistic integration of building zones and their fabrics and glazing:
Energy modelling tools allow for a more complex integration of building elements in energy balance, and hence the model may represent a deeper sense to obtain building energy demand. For example, solar heat gains from a large window can be transmitted inside the room and absorbed by the concrete slab with a high thermal mass. In the sun’s absence, the heat is then transformed back into the zone and offsets heating demand. Therefore, large north glazing, to a degree may be beneficial to some houses if the complex nature of the building fabric integration could be understood and undertaken. In our experience, buildings with large glazing to floor area ratios may gain better deals using VURB than the Star Rating method.

VURB model can be readily used for other assessments

With a little modification, VURB model can be used for daylight modelling where compliance with Part P2.4.4 Natural Light is required by the council. Also, with a VURB model, a CFD analysis can be undertaken for natural ventilation purposes and air movement assessments.

Best method to predict building’s heating & cooling demand in the design stage:

Determine the size of HVAC equipment and annual energy use:
Outcomes of energy modelling from VURB closely represents the actual energy demand of the Proposed Building. This information is useful to architects, builders and especially building services engineers. Once the HVAC equipment size is determined, it’s easier to locate their location with respect to the view, weight, and to estimate the overall cost of the HVAC system.
Undertake feasibility analysis for different energy source options:
Hour by hour heating and cooling demand of the proposed building is the key parameter to estimate what equipment or renewable option is most feasible for the building. It’s wise to consider referring to a professional feasibility assessment company that also undertakes VURB option for energy compliance. Once the Proposed Building is modelled and deemed to be compliant, the hour by hour results can also be used to determine what energy source option is the most suitable to meet the building demand.

Unlike NatHERS, Class 1b benefits from VURB method:

NatHERS Star Rating involves Class 1a, but VURB covers both Class 1a and Class 1b buildings.

Click here for further information on NCC building classification.

DISCOVER OUR PAST EXPERIENCE

Check out our past projects and see some complex buildings that Energy Compliance Team has managed to satisfy its compliance while maximising the heating and cooling energy conservation.

What are the CONS of VURB?

VURB doesn’t cover Class 2 and Class 4 part of a building:

Only NatHERS star rating covers Class 2 and Class 4 buildings as there are no Elemental Provisions for energy compliance of Class 2 and Class 4 buildings in Section J.

VURB can’t be used to gain BESS energy points

When a Victorian council demands BESS best practice as an ESD initiative, points are awarded in case you go beyond a 6-star rating. Unlike JV3, VURB method can’t be used to achieve BESS energy efficiency points.

VURB is relatively more expensive to undertake:

3D modelling takes more effort than 2D modelling.
NatHERS accredited tools model the building in a two-dimensional form and also generate reports that are valid for submitting, but this is not the case under VURB. Accurate 3D modelling of a complex building takes much more effort and therefore relatively more expensive to undertake. However, construction cost reduction is usually more than the energy assessor fee.

What are NCC Reference Building requirements?

NCC Reference building is a building that has the same geometry of the clients proposed building but for the sake of energy efficiency modelling, NCC requires you to modify it as per below:

Reference Building roof

The Proposed Building can have a roof of any shape and material. However, NCC requires you to compare it to a standard roof that most average Australian houses have. Therefore, the NCC Reference Building should have a roof at 23 degrees with a solar heat absorptance value of 0.6.

Reference Building ceiling

The Proposed Building can have a ceiling with any height or a sloped cathedral ceiling for that matter. However, NCC requires you to compare it to a minimum ceiling height of 2.4m for a habitable room. This ceiling must also be flat to the exclusion of any cathedral ceiling.

Reference Building ground floor

The Proposed Building can have a suspended floor above ground floor level. However, NCC requires you to compare it to a building having a concrete slab on ground. Ground temperature fluctuation is lower than the ambient weather and relatively closer to the temperatures where people feel comfortable. This temperature stability together with a higher concrete thermal mass is the reason why NCC requires a comparison between Proposed Building and Reference Building having a concrete slab on ground.

Reference Building roof lights

The Proposed Building can have any number of roof lights. However, NCC requires you to compare it to a building having no roof lights. NCC Vol 2.0 Part 3.8.4 allows roof lights for habitable rooms with no or minimum means of daylighting. As roof lights add to the building cooling demand, NCC requires Proposed Buildings to have minimum to no roof lights.