Verification Using a Reference Building (VURB)

If you want to minimize construction costs related to energy efficiency, i.e. glazing or slab insulation costs, the best approach for NCC energy compliance is called Verification Using a Reference Building (VURB) method. This method allows for a more realistic building modelling and takes everything into account. This is where an assessor can optimize the shading, introduce shading devices, trade-off insulation and SHGC of the windows to conduct the best low-cost solution possible for your building.

VURB method is also the last resort for energy compliance of alteration or extension to an existing building; Especially where some parts of the building are to be kept from new works.

At Energy Compliance, we offer all avenues to demonstrate your building compliance under any conditions.



We perform more iterations to reduce your construction costs.
We illustrate the added insulation to minimize any mistake during the construction stage.

Service Guarantee

If we can’t reduce your construction cost by more than our fee, we’ll only charge our 40% deposit. This is the best proof of how cost-efficient our performance-based solutions are. You won’t get this anywhere else!


Quick Turnaround

Quotations: Same business day of inquiry.
VURB Performance Solution reports: 4-7 business days.

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Who Benefits From VURB Method?

VURB method shows promise where:

  • A 6-star rating seems out of reach for the proposed alteration to an existing building.

  • Some parts of an existing building are to be kept from new works while aiming for energy compliance.

  • You are seeking to optimize cost and energy use, having an experienced energy assessor by your side.

  • Additional insulation to some parts of a new building is impossible and you need an insulation trade-off.

  • Glazing cost is too high and you need to offset energy use by adding more insulation, optimized shading or shading devices.

  • You wish to kill a bird with one stone: having the best solution for compliance while using its realistic outputs for choosing the best energy source option.

Too Good To Be True?

How do we do VURB here at Energy Compliance?

  1. Model the geometry of the house as per final architectural plans
  2. Apply heating and cooling setpoints and heat gains as specified in NCC.
  3. Apply schedules for people, appliances and HVAC operation.
  4. Use NCC Glazing Calculator to calculate minimum requirements for the glazing and assign them.
  5. Apply minimum DtS insulation requirements to the building fabric. Save the model “Proposed building based on DtS requirements”.
  6. FACT: NCC 2019 assumes an efficient standard Australian house should have:
                   – Ceilings not higher than 2.4m.
                    – Roofs pitched at 23 degrees with no skylights.
                    – Concrete slab on ground.
    Apply the above facts to step 5 and call it “Reference Building”. Run the model and calculate annual heating and cooling demand.
  7. Minimize the building cost for the “Proposed Building”. We may do this with low-cost thermal improvements such as adding insulation to the model from Step 5. Other low-cost means are shading size optimization or addition of shading devices to offset summer heat gains. If glazing cost is not the biggest concern, modify the cost minimization strategy. Addition of insulation to other parts of the building can reduce the high-cost added insulation to the existing walls.
  8. Run the Proposed Building. The Proposed Building is deemed compliant if its heating and/or cooling demand is less than the Reference Building.
  9. Iterate & optimize improvement to the Proposed Building in step 8 until you get to the sweet spot that offers the highest cost-saving.
  10. Complete the report.

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:

Reference Building

Click here to to investigate Reference Building model and its assigned building fabric insulation and external glazing thermal performance.


Building fabric:
No insulation added to the internal walls of the unconditioned spaces.
R2.3 added to the external walls.
R4.7 Added to the ceilings.

External glazing:
U-Value: 2.69, SHGC: 0.45

No skylights are modelled.

Proposed Building

Click here to to investigate Proposed Building model and its assigned building fabric insulation and external glazing thermal performance.


Building fabric:
R2.5 added to the internal walls of the unconditioned spaces.
R3.0 added to the external walls.
R5.9 Added to the ceilings.

External glazing:
U-Value: 3.49, SHGC: 0.65 

U-Value: 2.58, SHGC: 0.24

What are the PROS of VURB?


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?

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.