A client recently asked if they could build with concrete block (or Besser Brick) external walls without having to insulate them.
The answer?
Yes, yes, sometimes, possibly, no and yes.
Or to put it another way, it depends!
Whether Concrete Block external walls require insulation to comply with the Energy Efficiency Provisions of the National Construction Code and the relevant State & Territory legislations depends on three main factors:
- Class of Building
- Climate Zone
- Method of Assessment.
All these interplay with each other, so it is difficult to discuss them independendently. But for simplicity we will attempt to do this.
1. Is the building Commercial or Residential?
If the building is Commercial, and an assessment is undertaken via the Section J Deemed to Satisfy Method (as opposed to a JV 3 Assessment), then only the conditioned zones are required to be insulated. The non-conditioned zones (such as un-conditioned toilets, store rooms etc) are not required to achieve a minimum R-Value for the building envelope walls.
For walls surrounding conditioned zones (or zones likely to be conditioned), the walls will require additional insulation. If the only space for insulation is providied by a furring channel or batten, then the requirements are reduced, but additional insulation will still be required. The exception is if the wall is an earth-retaining wall, then it is not required to be insulated.
If the assessment is undertaken via JV3, then it is possible for the walls to be uninsulated, but compensations would need to be made via increased roof/ceiling insulation, good shading and orientation, appropriate glazing etc.
If the building is Residential, then it depends on the answers to the next two questions:
2. What method of Assessment is being Used?
If the assessment method is a NatHERS Software (6 Star Rated) Assessment, or the lesser used “Verification using a Reference Building”, then it is possible to achieve the 6 Star Rating in warmer climate zones without insulating the concrete block walls, as long as compensation is made with appropriate roof/ceiling insulation, good shading and orientation, appropriate glazing, and ventilation etc. A competent Energy Assessor can advise you whether insulation will be likely to be needed for your project, and assist you with the levels required in order to achieve the 6.0 Star Rating.
If the assessment method is a” Deemed to Satisfy – Elemental Provisions assessment” (DTS), then under BCA 2009 (allowed in NT and QLD if certain conditions are met), no insulation is required in the following situations (assuming the walls achieve a surface density of not less than 220kg/m2 (190 x 140 x 290mm and above achieve this)):
- If the wall is facing South (and the dwelling is located roughly south of Rockhampton)
- If the walls are a light colour, the habitable rooms contain ceiling fans and the glazing achieves a higher standard.
- If the walls are well shaded (amount depends on zone and orientation)
- For Climate Zone 2, if the walls are constructed on a flooring system in direct contact with the ground, eg slab on ground
For other situations in QLD, BCA 2010 must be used for DTS Assessments, and any concrete block walls are required to have at least R 0.5 additional insulation added.
Note that in NSW, BASIX is the required assessment method, and there is the option to have uninsulated concrete block walls with both DTS and Simulation method in the Thermal Comfort Section, however other conditions have to be met for other elements of the building.
For all other States and Territories, Assessed via NCC 2016, the Climate Zone is relevant to DTS Assessments.
3. What is the Climate Zone?
For Deemed to Satisfy Assessments using NCC 2016, where the concrete block external walls have a surface density of not less than 220kg/m2, then the following is true:
- In climate Zones 1, 2 & 3 any concrete block external walls are required to have at least R 0.5 additional insulation added.
- In climate Zone 5, if certain stringent conditions for shading, glazing, floor type and internal wall types are met, then there is the option to have uninsulated concrete block walls
- In climate Zones 4 & 6, the concrete block walls can be uninsulated if more stringent glazing conditions are met.
- In Climate Zones 7 & 8, external concrete block walls are required to have additional insulation.
Conclusion
Yes, yes, sometimes, possibly, no and yes. It might be simpler to consult an Accredited Thermal Performance Assessor. Contact BERA, and we can help you out.