Single-layer system

The traditional single layer segment installation methodology will no longer meet the new H1 requirements.

This is because segment widths designed to fit between truss chords create a thermal chimney over the structure, which allows heat loss into the ceiling space. As R-values increase and calculations are based on more robust accounts for thermal bridging, the impact of this heat loss cannot be adequately offset.

To address concerns about thermal bridging and heat loss between segments in ceilings, Comfortech® has developed the new extra-wide Pink® Superbatts® insulation. At 460mm wide, rather than the traditional 432mm, Pink® Superbatts® ensures a tight fit around the truss chords, with optional on-site notching to fully eliminate air gaps and airflow around structural members.

Pink® Superbatts® is available as an R7.0 for compliance via the Schedule method and other R-values for compliance via the Calculation and Modelling methods; these will include Pink® SuperBatts® insulation R4.5, R5.0 and R6.0.

Two-layer system

In developing its two-layer solution, Comfortech® knew it needed a denser first layer to ensure the expected thermal performance was still delivered under the compression of the second layer, as two layers of R3.6 would not deliver an R7.2 once compression was factored in.

Further to this, while typical truss bottom chords are 90mm or 140mm in height, Comfortech® identified that it needed to also accommodate for the fact that metal ceiling battens are hung below the truss chords and not fixed directly to them.

Therefore, Comfortech® developed its two-layer solution, with the top layer of the two-layer system being R4.5 and the first layer R2.6 with a 110mm thickness for 90mm truss chord, and Pink® Batts® R3.0 with a 160mm thickness for 140mm truss chords. The extra 20mm thickness ensures the top of the first insulation layer aligns with the top of the truss chord and, when the second layer is laid over, that there are no pockets or paths for heat flow/loss that would reduce the effective performance.

Insulation guard

Under the new H1 regulations, the last 500mm of the perimeter of the ceiling insulation can be reduced to R3.3, allowing the insulation to be carried out over the top plates of the wall, while reducing the barrier to air flow from the eave edges.

Adequate ventilation is critical to the performance of ceiling insulation. As R values increase, the temperature differential between the air below and above the insulation also increases, therefore increasing the likelihood of condensation occurring when the warm air from below meets the cold air above.

With the increase in insulation thickness required to meet the 5th Edition of H1, Comfortech® also identified a potential increased risk of the insulation coming into contact with the underside of the roof and underlay, preventing ventilation of the ceiling space and creating a condensation and mould risk.

Therefore, Comfortech® recommends installing an insulation guard for both the single and double layer system, over the roof trusses and under the roof underlay, before the roof is installed. The insulation guard ensures the minimum 25mm air gap is maintained even where the insulation is installed under compression out to the roof edge, over the top plate. This enables convective heat flow to remove moisture from the roof space, preventing condensation build, which would reduce the thermal performance.

Skillion roof solution

Skillion ceilings pose a unique challenge for achieving the new higher values, particularly via the Schedule Method.

With rafters at 600mm centres or less, an R7.0 segment will not achieve the required R6.6 construction R-value. Therefore, Comfortech® has developed a new R7.4 single layer solution, suitable for skillion roofs with 290mm rafter depths.

For rafters of less than 290mm depth, the Comfortech® solution is to use the R 6.0 Skillion Roof Pink® Batts® insulation with a second layer, at 40mm thickness, of R1.0 Pink® Batts® installed below the rafters, between the ceiling battens.

This system addresses the thermal bridging issue and ensures the R6.6 construction can be achieved even in a skillion roof situation. Additional over-eave ventilation should also be considered, as the small volume of airflow in skillion roofs increases the condensation risk further.

Contact Comfortech® for more solutions at technicalsupport@comfortech.co.nz.

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Floors

Windows & Doors