R1.0 vs R1.5 Insulated Ductwork: What Is the Difference?

If you are getting quotes for ducted reverse cycle air conditioning in Melbourne or anywhere in Victoria, you will see ducting described as R1.0 or R1.5. The difference matters for comfort, running costs and compliance. Here is what the numbers mean, what the National Construction Code (NCC) requires in Victoria, every case where R1.0 is allowed, and what to check before you sign a quote.

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R1.0 vs R1.5 ducting in Victoria: the short answer

• R1.5 ducting is better insulated than R1.0.
• For ducted reverse cycle, Victoria's climate zones 4, 6, 7 and 8 all need R1.5 as the standard minimum.
• R1.0 only meets the rules in a few limited situations, listed in full below.
• EZYAIR uses R1.5 on every Victorian job.

What R1.5 insulated ducting means and why it is required in Victoria

Every EZYAIR ducted reverse cycle package comes with R1.5 insulated ducting. The R-value tells you how well the insulation around each duct resists heat passing through it. The higher the number, the better your ducts hold warmth in during winter and keep roof space heat out during summer.

Victoria's climate zones and the R1.5 minimum

The National Construction Code (NCC) splits Australia into 8 climate zones. Victoria covers climate zones 4, 6, 7 and 8, and for ducted reverse cycle all four need R1.5 duct insulation as the standard minimum. Most of Melbourne, Geelong and Bendigo are in zone 6, Ballarat and the ranges are in zone 7, the north west around Mildura is zone 4, and the alpine areas such as Mount Hotham are zone 8. Under NCC Housing Provisions clause 13.7.4, a ducted reverse cycle system is "a combined heating and refrigerated cooling system", and for this type of system the minimum material R-value for ductwork is R1.5 in climate zones 1, 3, 4, 6, 7 and 8, and R1.0 only in climate zones 2 and 5. No part of Victoria is in zone 2 or 5.

Simplified, see ABCB climate zone map. Drawn by EZYAIR from the ABCB's climate zone data. Check your own address on the official ABCB Climate Map (data on data.gov.au). The duct R-values come from NCC Housing Provisions clause 13.7.4, and the BPC checks duct R-values in its mechanical services audit checklist.

EZYAIR uses R1.5 ducting on every job across Victoria, in every climate zone.

When R1.0 or a lower R-value is allowed: the full list

We believe in being upfront, so here is every case in NCC clause 13.7.4 where ducting with less than R1.5 can still meet the rules in Victoria:

1. Ducts under a suspended floor with an enclosed perimeter. For ducted reverse cycle in climate zones 1, 3, 4, 6 and 7, the NCC says the minimum "may be reduced by 0.5 for combined heating and refrigerated cooling systems in climate zones 1, 3, 4, 6 and 7 if the ducts are" "under a suspended floor with an enclosed perimeter". That takes the minimum from R1.5 to R1.0. The NCC explains that "An enclosed perimeter treatment means that the airspace under the floor is enclosed between ground and floor level by walls which have only the required subfloor vents." An open subfloor, such as a home on stumps with open sides, does not qualify.
   
   
2. Ducts in a roof space with insulation directly under the roofing. The same reduction applies if the ducts are "in a roof space that has an insulation of greater than or equal to R0.5 directly beneath the roofing." This means insulation fixed under the roof sheets or tiles themselves, not the batts lying on your ceiling.
   
   
3. Ducts inside the insulated part of the home. These are exempt from the duct R-value requirement altogether. The NCC says "The requirements of (1) do not apply to heating and cooling ductwork and fittings located within the insulated building envelope including a service riser within the conditioned space, internal floors between storeys and the like."
   
   
4. Heating only or cooling only systems. This is not ducted reverse cycle, but for completeness: for "a heating-only system or cooling-only system including an evaporative cooling system", such as gas ducted heating or evaporative cooling, the NCC minimum for ductwork is R1.0 in climate zones 1 to 7 and R1.5 in climate zone 8.

The reductions in points 1 and 2 do not apply in climate zone 8, so in Victoria's alpine areas ducted reverse cycle needs R1.5 wherever the ducts run outside the insulated envelope. Read the full wording in NCC Housing Provisions Part 13.7, clause 13.7.4.

Why EZYAIR still uses R1.5 everywhere

• One standard for every home: R1.5 meets the minimum for ducted reverse cycle in every Victorian climate zone, whether your ducts run through the roof, under the floor or elsewhere. Nothing depends on a borderline judgement call.
  
  
• No hidden roof or subfloor assumptions: the R1.0 cases rely on insulation directly under the roofing or a fully enclosed subfloor. These are often hard to confirm, can be patchy, and can change if the roof or subfloor is altered later.
  
  
• Better results even when R1.0 would be allowed: thicker insulation means less heating and cooling lost on the way to your rooms. That is why we fit R1.5 even where the rules would accept less.

Why R1.5 ducting is better for your family than R1.0

• Less heat lost or gained in the roof space: roof spaces get very hot in a Victorian summer and cold in winter. Thicker insulation slows heat moving through the duct walls, so more of the heating and cooling you pay for reaches your rooms. As a guide, the NCC's explanatory table for flexible ducting lists 63 mm of glass wool for R1.5, compared with 45 mm for R1.0.
  
  
• Lower running costs: when less energy is wasted on the way to each room, your system does not have to work as hard to reach the temperature you set.
  
  
• More comfort at the outlets: air arrives closer to the temperature the system produced, so it feels warmer in winter and cooler in summer.
  
  
• Less condensation: in summer, cold ducts in a hot roof can collect moisture. Better insulation keeps the outside of the duct closer to the roof space temperature. The NCC notes that "In some climate zones condensation may create problems with uninsulated ductwork, in which case insulation should still be considered" and that "Insulation for refrigerated cooling ductwork should have a vapour barrier to prevent possible damage by condensation."
  
  
• Compliance: R1.5 meets the NCC minimum for ducted reverse cycle across all of Victoria's climate zones, whatever your roof or subfloor is like.

Sources: ABCB, NCC Housing Provisions Part 13.7 Services, clause 13.7.4; BPC, Mechanical services including duct fixing checklist (PDF); BPC, Permitted assessment reference materials, plumbing classes; BPC, Practice Note EE 03, Energy efficiency requirements for new residential buildings; Technical Solution Sheet 7.04, Flexible ducting for heating, cooling and ventilation (2020, archived copy, no current BPC version); ABCB Climate Map.

Ask us about R1.5 ducting for your home or see our ducted air conditioning packages

R1.0 vs R1.5 ducting FAQs

What is the difference between R1.0 and R1.5 ducting?

The R-value measures how well the insulation around a duct resists heat passing through it. R1.5 ducting has a higher R-value than R1.0, so it holds heat in during winter and keeps roof space heat out during summer better. As a guide, the NCC's explanatory table for flexible ducting lists 63 mm of glasswool for R1.5, compared with 45 mm for R1.0.

What R-value ducting is required in Victoria?

Victoria is in NCC climate zones 4, 6, 7 and 8. For ducted reverse cycle (a combined heating and refrigerated cooling system), NCC Housing Provisions clause 13.7.4 sets a minimum of R1.5 for ductwork in all four zones. R1.0 is the standard minimum only in climate zones 2 and 5, and no part of Victoria is in those zones.

When is R1.0 ducting allowed for ducted reverse cycle in Victoria?

In climate zones 4, 6 and 7 only, the minimum can be reduced by 0.5 (to R1.0) if the ducts are under a suspended floor with an enclosed perimeter, or in a roof space with insulation of at least R0.5 directly beneath the roofing. These reductions do not apply in climate zone 8. Ducts inside the insulated building envelope are exempt from the duct R-value requirement.

Why does EZYAIR use R1.5 ducting on every job?

Victoria is in NCC climate zones 4, 6, 7 and 8, and in all of them the standard minimum for ducted reverse cycle ductwork is R1.5. R1.0 only meets the rules in limited cases: ducts under a suspended floor with an enclosed perimeter, or in a roof space with at least R0.5 insulation directly beneath the roofing (zones 4, 6 and 7 only). Ducts inside the insulated part of the home are exempt. We fit R1.5 on every Victorian job so you meet the minimum wherever the ducts run, lose less heating and cooling, and get more comfortable air at the outlets.

How can I check the R-value of my ducting?

Flexible ductwork must be labelled with its R-value, and the label is repeated along the length of the duct. Check the printed rating on the ducts in your roof space, and ask any installer to put the R-value of the ducting in your written quote.

Does gas ducted heating need R1.5 ducting?

For a heating only or cooling only system, such as gas ducted heating or evaporative cooling, the NCC minimum for ductwork is R1.0 in climate zones 1 to 7 and R1.5 in climate zone 8. Ducted reverse cycle has the higher R1.5 minimum across Victoria.

Talk to EZYAIR about your ducting

EZYAIR has been heating and cooling Melbourne homes since 2007 and is a Victorian Energy Upgrades accredited provider (A2261). See our ducted air conditioning packages, every one with R1.5 insulated ducting, or contact us for a free quote.