VURB

VURB (Verification Using a Reference Building) demonstrates compliance with residential energy provisions of the National Construction Code (NCC) by verifying that your proposed building with your preferred insulation and glazing uses less heating and cooling energy than the NCC Reference building. It allows for utmost flexibility by using hour-by-hour energy modelling software and results in reducing construction costs (e.g. glazing) compared with the NatHERS Rating or Deemed to Satisfy method.

a VURB model used to conduct a Performance Solution report

Who Benefits from VURB Assessment?

VURB method shows promise where:

  • A costly Energy Rating seems out of reach for alteration to an existing building or a new luxury house with high raked ceilings and large windows.

  • For an alteration or extension project, where some parts of an existing building are to be kept from new works, while aiming for energy compliance.

  • You are seeking to optimize construction 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 two birds 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 Consultants?

1. Model the geometry of the house as per the 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 the ABCB Glazing Calculator to calculate the Performance Requirements for the glazing.
5. Apply minimum DtS insulation requirements to the building fabric. Save the model “Proposed building based on DtS requirements”.

Realistic energy modelling for VURB projects

Fact: Under NCC 2022, the reference building model must match the proposed design, using the minimum building fabric performance values specified in Housing Provisions Part 13.2. However, under NCC 2019—which remains applicable in Tasmania—the reference building differs from the proposed model in certain aspects:

  • Ceilings not higher than 2.4m.
  • Roofs pitched at 23 degrees with no skylights.
  • Concrete slab on ground.
3D modelling is a basis for VURB Performance Solution

6. 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 the addition of shading devices to offset summer heat gains. If glazing cost is not the biggest concern, modify the cost minimization strategy.
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.

VURB modelling involves creating a detailed 3D model

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.
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VURB

Do I need VURB or NatHERS 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.

What are NCC compliance methods 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.
  • Energy Rating: This method is another DtS method of demonstrating compliance for energy efficiency under NCC. This method considers a building to be deemed to comply with NCC energy efficiency provisions, provided the building obtains at least a 7-star rating from one of the NatHERS accredited tools.

Cons of the above DtS approaches: The outputs of the above DtS approaches are proven 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 analysing 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:

Residence at Marengo

NatHERS rating with U2.7 windows (double glazed, thermally broken):

Residence at Berwick

NatHERS rating with U1.5 windows (triple glazed, thermally broken):

using VURB, residential building can have compliant low-cost windows
VURB method allows for a flexible and cost-effective design

What are VURB Pros?

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 the VURB method. Hence, buildings with a slab on ground have a higher chance of having 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 of obtaining 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, the VURB model can be used for daylight modelling where compliance with the NCC 2022 Housing Provisions, Part 10.5 (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 a 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 represent 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 its 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 the 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 which energy source option is the most suitable to meet the building’s demand.

Unlike NatHERS, Class 1b benefits from the VURB method

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

DISCOVER OUR PAST VURB EXPERIENCE

Check out our past projects and see some complex buildings that the Energy Compliance Consultants has managed to satisfy its compliance.

What are VURB Cons?

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

Only the 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 7-star rating. Unlike JV3, the 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 submission, but this is not the case under VURB. Accurate 3D modelling of a complex building takes much more effort and is therefore relatively more expensive to undertake. However, construction cost reduction is usually more than the energy assessor fee.

FAQ

Assessors use the NatHERS Rating as a means to achieve compliance with energy efficiency provisions of the NCC. However, using the VURB method as a means of compliance has the following benefits:

  • With VURB, your building is compared to your building! Not with a Benchmark or a preset of area-adjusted heating and cooling demand. Therefore, VURB allows a comparison with a reference building having the same geometry and features.
  • With VURB, the modelling software calculates an hourly energy demand using a weather file. Also, you will be able to assess solar gain in an hourly manner. Therefore, the software captures the physics of solar heat gain in building materials such as windows and also the impact of thermal mass and shading devices.
  • VURB method utilizes commercial software for energy analysis. Commercial tools have many features like design optimization and parametric study. These features help to reach a better solution for the compliance of your building.

These benefits generally allow you to have cost-effective compliance compared to a simple NatHERS rating. Check our experience for more details.

NatHERS rating method often gives you very expensive windows. This is certainly true for a 7-star energy rating which is a requirement under NCC 2022.

BCA developed VURB as a verification method that allows for compliance with energy requirements using computer modelling. Using methods like NatHERS rating or DtS, buildings with complex geometries face difficulties achieving compliance with the code. In such instances, VURB helps to achieve cost-effective compliance with low-cost glazing. Using VURB, you can add insulation in requirements to part of the building (i.e. under-slab) to compensate for the weak performance of cheaper glazing. Also, you can consider the impact of thermal mass, solar gain or two-way heat transfer through a concrete slab.

A 7-star energy rating report specifies the performance requirements for your windows.

Minimum Deemed To Satisfy (DtS) energy performance requirements for the glazing U-value & SHGC are specified in NCC 2022 Housing Provisions, Part 13.3. This means knowing the acceptable range of U-values for your building requires following the Deemed to Satisfy (DtS) provisions. However, if you need to go beyond rigid DtS provisions and install cheaper windows, you need to use the Performance Solution pathway for your building’s compliance. In other words, you need to undertake a Performance Solution instead of following NCC’s Performance Requirements. For instance, VURB rating is a Performance Solution for residential dwellings that is verified under the NCC 2022 as a Verification Method.

VURB is a method to comply with the energy efficiency requirements of NCC. This method is used in the following cases:

  • To obtain a cost-effective energy compliance
  • To obtain energy compliance when you can not achieve a 6-star rating
  • To obtain energy compliance for Class 1b building, that is not covered in 6-star rating using FR-5.

VURB is a verification method to achieve compliance under NCC 2022 Vol 2.0, Part H6, Performance Requirement H6P1. This involves compliance with the following:

  • Part 13.2 (building fabric)
  • Part 13.3 (external glazing and shading)
  • Part 13.4 (building sealing)
  • Part 13.5 (ceiling fans)

Note that compliance with the above parts could also be done using other methods, such as DtS or NatHERS Rating.

Only Class 1 and Class 10 buildings can use VURB as a verification method to achieve compliance with the energy efficiency requirements of NCC Vol 2.0.

VURB is often referred to as a verification method for the energy compliance of residential dwellings.

For commercial buildings like hotels, office buildings, retail and restaurants of Class 3 and Class 5 to Class 9 buildings, there is a similar verification method that is called JV3.

Here at Energy Compliance Consultants, we deliver our VURB Performance Solution reports between 4 to 7 days. This depends on the complexity of your building and the effort we put into our computer modelling.

For a VURB assessment to start, architectural drawings involving floor plan, roof plan, elevations, sections, and window schedule shall be supplied to the assessor. In addition to that, client preferences and a former 7-star assessment report also help with a comprehensive VURB assessment.

VURB and JV3 are both verification methods of compliance with the energy efficiency requirements of NCC. The methods are the same methods, but applicable to different building classes. VURB is an alternative solution to achieve compliance under NCC 2022 Vol 2.0 Part H6 for Class 1 and Class 10 buildings. JV3 is an alternative solution to achieve compliance under NCC Vol 1.0 Section J for common parts of Class 2, Class 3, to Class 9 buildings.

The older version of NCC (NCC 2019) is still applicable in Tasmania. NCC 2019 Reference building is a building that has the same geometry as the proposed building, but for the sake of energy modelling, NCC requires you to modify it as indicated 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 the 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 at which people feel comfortable. This temperature stability, together with a higher concrete thermal mass, is the reason why NCC requires a comparison between the Proposed Building and the 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 a minimum to no roof lights.