Section J NCC 2019 Changes and Impacts – Façade Performance

18 February 2020

Section J NCC 2019 is well and truly here, and as the deadline for the current transition period comes to an end on the 1st of May 2020, we look at what we have learned over the last 10 months. Including what are the key changes, and what are the major impacts that they may have on your projects. This article will focus on J1-Building Fabric, particularly façade performance.

And remember, any Section J NCC 2016 report will need to be updated to Section J NCC 2019 if the construction certificate has not been lodged before the 1st of May 2020.


Overview

  • Wall insulation and glazing performance assessed collectively.
  • Thermal bridging in facades to be considered in line with AS/NZS 4859.2.
  • Limited roof solar absorbance for DTS.
  • More floor insulation for DTS.
  • Increased construction costs for DTS.
  • Greater potential for use of JV3 to rationalise overall building designs.
  • Facade design required at DA stage to avoid costly modifications later.

Why the change?

  • To align with the COAG National Energy Productivity Plan, the revised Section J aims to reduce building Greenhouse Gas Emissions by 30-40% compare to NCC 2016.
The construction, operation and maintenance of buildings accounts for almost a quarter of greenhouse gas emissions in Australia.

When will the change happen?

  • The official NCC 2019 came into effect from the 1stof May 2019.
  • Section J – Energy Efficiency was given an additional 12-months transition period until the enforced date.
  • Construction Certificates lodged after the 30th of April 2020 will need to meet the requirements of NCC 2019 Section J.

What can I do to get ready?

  • Due to significant changes to Section J for 2019, it is now good practice to conduct the Section J assessment at the design development stage.
  • This includes conducting your Deemed-to-Satisfy (DTS) or Performance based solution (JV3) prior to your DA submission.
  • Early commitment to window sizing and façade construction materials is important to determine the minimum wall insulation and glazing specification.
  • Increased restrictions on glazing limits and performance may require design and window detail changes to meet compliance. These changes can be more easily implement prior to your DA submission. I.e. increased shading.
  • Any Section J 2016 report will need to be updated to Section J 2019 if the construction certificate is not lodged before the 1st of May 2020.
It is now good practice to conduct the Section J assessment at design development stage.
Early commitment to window sizing and façade construction materials is important to determine the minimum wall insulation and glazing specification

Which projects are affected by the changes?

  • The Deemed-to-Satisfy (DTS) Provisions of NCC 2019 Volume 1 apply to building elements of
    • class 2 non-BASIX projects only
    • class 3 large boarding houses, student accommodation, and hotels
    • class 5 office buildings and general medical practitioners
    • class 6 retail, restaurants and cafes
    • class 7a carpark buildings
    • class 7b warehouse and storage buildings
    • class 8 factory and workshop buildings
    • class 9a health-care clinic and hospital building.
    • class 9b assembly buildings
    • class 9c aged care buildings
  • In NSW, class 2, class 3 small boarding house and 4 buildings are covered under NatHERS and BASIX

What are the major changes for NCC 2019 Section J?

Thermal bridging

  • Also known as cold bridging, thermal bridging is a kind of ‘short circuit’ for heat transfer.
  • Where high conductivity materials touch, heat will bypass insulation and travel the path of least resistance.
  • Calculations for facades must be in line with AS/NZS 4859.2.
  • The wall total R-value (Rt) will be highly dependent on the amount of thermal bridging within the façade.
  • A small amount of thermal bridging (which is normally ignored) will have a large negative effect on the Rt.
  • Thermal breaks will be required for facades with metal framing.
  • For more information on thermal bridging calculations and implications for your project please get in contact with the BCA Energy team.
Section J assessments must now have wall thermal bridging calculations to correctly determine the total wall R-value (Rt). Metal framed walls will require thermal breaks.

Roof and Ceiling Construction

  • All climate zones, except 8, to have a maximum roof solar absorptance of 0.45 (light color Colorbond).
  • All medium and dark color roofs will require a performance-based solution (JV3) to demonstrate compliance.
  • This includes green roofs and dark-coloured concrete or membranes

Walls and Glazing Construction

  • Previously, walls and glazing were independent of one another. I.e. wall (opaque) Rt2.8 and glazing assessed using the NCC 2014 glazing calculator.
  • For 2019, using an area-weighted average between the wall area and glazing area, combined they must have a maximum U-value of 2.0 for most buildings and climate zones.
  • An example of area-weighted calculation below. (Rt includes thermal bridging calculations and U-value is full window system).
Area weighted average U-value must be under 2.0 for most buildings and climate zones.
  • For U-value, method 2 uses a weighted average across all orientations.
  • A poor performing façade can be offset by a well-performing façade. This is the preferred method with better overall results.
  • The SHGC calculation must be under the allowable ‘solar admittance’ or ‘air-conditioner energy value’.
  • Air-conditioner energy value’ is a series of calculations which theoretically predicts HVAC energy use, without the need for simulation.
  • An example of solar admittance calculation below.
The SHGC calculation must be under the allowable ‘solar admittance’ or ‘air-conditioner energy value’.
  • Depending on the building envelop design, you can use maximize the amount of wall (opaque) area to reduce glazing specification. However, this will increase the amount of insulation required.

Display glazing

  • Exempt for J1 – Building Fabric.
  • Display glazing has its own performance limits. System U-value less than 5.8 and SHGC less than 0.81 / Shading factor.
  • Frameless single, clear glazing without the need for shading.
  • This is only for class 6 retail display glazing adjacent to walkways. i.e. Shopfront or car showroom.
  • This can’t be used for Commercial, Cafés or Restaurants.
Display glazing has its own performance limits. System U-value less than 5.8 and SHGC less than 0.81 / Shading factor.

Floor insulation

  • All floors will require insulation, including open/enclosed suspended and slab on ground.
  • NCC 2019 includes a ‘sub-floor offset’, which means floor insulation may be reduced or not be required depending on the building’s floor area to perimeter ratio.
  • Depending on the climate zone and building use, the required floor insulation can be removed with a JV3.

What are the major impacts to my project?

  • Thermal breaks to be installed between metal frames and façade elements.
  • Spandrel panels will require thermally broken frames to retain insulation performance.
  • JV3 performance solution needed for medium to dark coloured roofs.
  • DTS now allows for glazing specification standardisation across different orientations without the need for a JV3.
  • Facades with a high ratio of glazing to wall area will require higher performance glazing compared to NCC 2016.
  • Demonstrated in the graphs below as the glazing ratio increases the performance of the glazing is increased.
As the glazing to wall ratio increases, the glazing performance becomes increasing hard to meet.
  • This does mean an increase in façade costs for high glazing ratio facades.
  • Ratios above 60%, thermally broken double-glazing systems may be required where previously single glazed low-e would be adequate.
  • The graph below demonstrates as the glazing ratio increases the SHGC of the glazing becomes more stringent compared to NCC 2016.
  • A lower SHGC will mean dark tinting, increased reflectivity or addition of colouring such as green or blue.
  • Importantly, façade designs with high glazing to wall ratios may lead to glazing specifications that are impractical or not possible to be sourced. I.e. Triple glazing with unrealistic SHGC values.
  • It will depend on your ESD consultant to suggest helpful and effective design changes to retain the concept design of the façade while achieving practical glazing specifications.

What is my next step?

  • Contact us at BCA Energy to discuss the changes and impacts for your specific projects.
  • We can help you through the transition period and make it easier for your projects to meet the new and more stringent performance requirements of NCC 2019.
  • Projects which have been assessed under NCC 2016 will need to be updated to NCC 2019 to comply with Section J from the 1st of May 2020. We can make this update as smooth as possible.
  • BCA Energy are also providing an NCC 2019 Section J update presentation. If you would like a copy of this or you would like us to present this to your team, please let us know.

 

For more information on Section J 2019, or how BCA Energy can assist in meeting your other ESD requirements please contact Robert Romanous within our office on 1300 787 302 or at rromanous@bcaenergy.com.au