Queensland Renovations (2022) - QDC 4.1

State: Qld

Member Question:

Have been reading the revision to the QDC4.1 due to come into effect from May 1. It’s indicated that renovation work will need to comply with P1.

Section 1.3 of the current tech note refers to ‘major renovation’ work requiring simulation. Do you have a way of measuring what constitutes major renovation work?

In the instance where the renovation work is considered major and needs to be simulated, does all of the existing building need to be modelled? Or just the new portion?

TechLink Response

Summary

• Internal Renovation not requiring building approval – no energy efficiency assessment is required
• Minor Renovation (less than 50% by volume of dwelling altered) – energy efficiency assessment on new or altered works only, usually via DTS, but NatHERS can be used if preferred.
• Major Renovation (more than 50% altered) – certifier decides scope of energy efficiency assessment, ranging from new only, to whole dwelling. This can be carried out via DTS or NatHERS.

Yes – adds/alts need to comply with P1 under the new QDC.  

• QDC MP 4.1 v1.15 defines Renovation as any alterations or addition to an existing class 1 building or the sole-occupancy unit of a class 2 building requiring building development approval.
• P1 states that a class 1 building (and an enclosed class 10a building attached to a class 1 building) must comply with performance requirements H6P1 and H6P2 in the BCA (NCC, volume 2).
• If the renovations are internal only, and no building development approval is required, then no Energy Efficiency Assessment is required.

If a DA or BA is required, this is where things get interesting!  The Building Act and the QDC don’t appear to line up on the assessment of alterations and additions, and so care needs to be taken to ensure compliance.

Rules for a “Major Renovation”

If a DA or BA is required, and if the current renovation (including any structural alterations carried out in the previous three years) represents more than half the total volume of the existing building, there is a specific section of The Building Act – S 81 (Building development approval for particular alterations may require existing building or structure to comply with building assessment provisions) that applies.

This section states that if the 50% is exceeded (or if the Certifier deems the alterations pose a risk to safety or fire safety), then:

“The building development approval may include a condition that all, or a stated part, of the existing building or structure, must comply with all or a stated part of the building assessment provisions as if it were a new building or structure”.

So, for a major renovation, the Certifier decides whether the Energy Efficiency requirements need to apply to the whole building or just the additions and alterations, per S81.

The ‘more than half the total volume’ is not explained further.  So there is discretion on that point as well.  For example, if the flooring in the whole house is being re-done, and 2 windows swapped from sliding to louvre, is that more than 50% by volume of the dwelling being altered?  What about if all the walls and ceilings are being re-lined?  What if there is a pure addition of 3 rooms, but they only comprise an additional 40% by volume?

The QDC Guide, although not binding, interprets the QDC and provides guidance for its implementation.  It states that “Building certifiers should take into account the factors associated with requiring compliance when compared to the potential benefits. For example, if the building work represents more than 50 per cent of the existing building’s floor area, the building certifier can impose conditions in the approval that require the existing part of the building to comply with all or a stated part of the current building assessment provisions. The building certifier may reasonably decide not to impose conditions for upgrading the existing part of the building in circumstances where they consider that applying the new building requirements would:

• not provide a level of benefit commensurate with, or exceeding, the additional costs
• otherwise be overly onerous or technically impractical” (4.3.2, QDC Guide)

Therefore, the Energy Assessor needs to obtain direction as to the scope of their Assessment in a particular renovation from the building certifier.  

Rules for a “Minor Renovation”

If the current renovation (including any structural alterations carried out in the previous three years)  represents less than half the total volume of the existing building, there is no provision in The Building Act.  One might conclude that an assessment is not required.  However, this does not mean that there is no requirement for assessment, as alterations are also covered under the QDC MP4.1.

Minor additions (requiring a BA or DA) need an Energy Efficiency Assessment, but only on the parts of the building that are being altered or added to by the renovation.

The QDC MP4.1 Guide discusses alterations (which include additions) and provides for a common sense approach, saying that the alterations need to comply “as much as practical.”  (4.3.2, QDC Guide)

Therefore a DTS Assessment on the alterations is the most straightforward approach, as it can be clearly demonstrated what parts of the work the energy assessment relates to.

When discussing using the NatHERS Software to assess an alteration, the QDC Guide has some interesting suggestions.

The first seems at odds with the NatHERS Tech Note’s specific requirement to only use the NatHERS Software to assess a whole dwelling (“NatHERS software tools are used to assess an entire dwelling. Additions or extension to an existing dwelling must be modelled as part of the entire dwelling”, NatHERS Tech Note, June 2019, part 2.3).   The QDC Guide states “To determine the energy equivalence rating for an alteration to an existing house, a software assessment of the building design is recommended. The plans need to include the kitchen area as a reference point to undertake the software assessment to determine internal heat loads. The software assessment could model the area covered by the alteration (inclusive of the kitchen area).  Accredited NatHERS Assessors (and they should all be accredited!), cannot follow the QDC Guide at this point, as they need to model the whole dwelling.

The QDC Guide goes on to state: “Another approach is to undertake two assessments of the entire house, one before and one after the alteration, to demonstrate any degree of energy efficiency improvement. The building certifier should consider any of the available practical steps that the energy efficiency assessor has identified that could assist the house in achieving a rating as close to 6 stars as possible. It is recommended that homeowners discuss possible requirements involved with the alteration with the building certifier as early as possible in the design stage.

Where practical, the following features should be considered and applied to the alteration:

• insulation in new walls, roof lining and ceiling (note, for some councils, a change in roof type, for example, from tile to metal sheet roofing, is subject to a building development application)
• shading of walls and windows with roof eaves and awnings (note, it would not be expected that existing roof eaves would need to be altered)
• window size, type and location to promote cross-ventilation
• lighter colour roof and external walls
• treated glazing
• ceiling fans in living areas and bedrooms.”

This guidance implies that a NatHERS Assessment can be undertaken but then allow common sense to apply as to which features should be required to be implemented.  Given the sophisticated science behind all the inputs in a NatHERS Assessment, it seems like a strange approach to have a model which shows 6 Star compliance, but then the building certifier decides which of the inputs should be adopted.  

What about having the additions assessed under older legislation?

S61 of The Building Act states that “Alterations to safe existing work may be approved on the basis of earlier building assessment provisions”.  It would be possible to make a case to a building certifier that a particular alteration would be best assessed via earlier legislation, but it would be the certifier who would have the final say.  An example might be an older home with single-glazed windows throughout that is having 2 windows replaced as part of a renovation.  If those windows had to be consistent with current energy efficiency legislation, they might need to be low-e or double-glazed, but this would have them looking different to the existing windows beside them.  One solution would be to have all the windows replaced, but this would be overly costly and impractical.  In this case, the building certifier could allow for the new glazing to be assessed via earlier legislation, which would allow for consistent single glazing throughout.

What is the practice in Queensland?

The guidance for alterations and additions is not actually straightforward or consistent.  What happens on the ground?

If there is a BA or DA for a major renovation, there should be an Energy Efficiency Assessment carried out.

Additionally, most building certifiers require an Energy Efficiency Assessment in the following three cases:

• where there is significant new work being added to an existing building
• where there are new windows being added
• where there is a change of use from non-habitable to habitable (think Garage conversion to bedroom).

In these cases, the new work is assessed, usually via the DTS Method, and needs to comply with current Energy Efficiency Legislation. If the new windows are only facing a particular direction, it is considered reasonable for the Assessor to assess the glazing of the floor as a whole but only require the new glazing to comply with the requirements.  This practice is not referenced in any Queensland-specific legislation but is the guidance noted and explained in the Victoria Building Authority’s Practice Note 55-2018 “Residential Sustainability Measures.”

This is the common sense, practical approach in 99% of cases, although may be more challenging under the NCC 2019 or NCC 2022 DTS provisions.