Thermal Efficiency Meets Practicality with the Viking Warm Roof System

The Viking Warm Roof system renders a more energy-efficient building — warmer in winter, cooler in summer. This BRANZ appraised system (no. 713) comprises a layer of rigid Kingspan polyisocyanurate insulation installed on top of a substrate (plywood, concrete or steel) with a Viking waterproofing membrane system installed on top of that (a vapour barrier is also required in Climate Zone 3). A Viking Warm Roof can achieve the Building Code's H1 minimum R-value requirement for roofs of R-2.9, with just 75mm thickness of Kingspan insulation.

While suitable for new-builds, the Viking Warm Roof system is commonly used as an overlay solution for re-roofing a building. This can be extremely useful seeing as Building Consent isn't required providing the existing substrate (which isn't being replaced; just 'overlaid') has satisfied the minimum 15 year durability requirement under B2.

Other benefits of a Viking Warm Roof overlay include:

It avoids having to relocate building inhabitants and contents;
With a warm roof, the dew point is transferred to the outside of the building rather than finding itself in the ceiling cavity, so it's a healthier option;
A tapered insulation panel option is available to promote water-shed. This negates the costly carpentry required to re-pitch a flat substrate to the minimum slope of two degrees;
There is no dumping of the old roof, or the need for scaffolding / shrink wrap to cover the exposed building during the reroof process;
The rigid insulation will stiffen and brace a plywood or steel substrate, but remain sufficiently light for a building structure not to require reinforcement;
The energy savings from the high R-Value can pay for the warm roof overlay within ten years (depending on the thickness of insulation installed).

Viking WarmRoof System

Viking Roofspec

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The most commonly accepted definition of a warm roof (for low slope roofs) is 'a roof where the insulation is installed on top of the roof structure' i.e.

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The Viking WarmRoof System has been appraised for use as an insulating roof on buildings within the following scope:

the scope limitations of NZBC Acceptable Solution E2/AS1, paragraph 1.1 with regards to building height and maximum floor plan areas; and,
on limited access flat roofs with concrete, plywood or steel structural decks subject to specific structural design; and,
with roofs constructed to drain water to gutters and drainage outlets complying with the NZBC; and,
with roofs constructed to suitable falls (refer paragraph 15.3 and 15.4 of the Viking Warm Roof BRANZ Appraisal); and,
with no integral roof gardens; and,
situated in NZS 3604 Building Wind Zones, up to, and including Extra High

The Viking WarmRoof System has also been appraised for durability and thermal performance as an insulated roofing systemon buildings that are the subject of specific design with no building height restriction. Building designers are responsible for the building design and for the incorporation of the Viking WarmRoof System into their design in accordance with the declared properties and instructions of Viking Roofspec.

Clause B1 STRUCTURE: Performance B1.3.1. The Viking WarmRoof System meets this requirement.
Clause B2 DURABILITY: Performance B2.3.1 (b), 15 years. The Viking WarmRoof System meets this requirement. See paragraph 10.1 of the Viking WarmRoof BRANZ Appraisal.
Clause E2 EXTERNAL MOISTURE: Performance E2.3.1 and E2.3.2. The Viking WarmRoof System meets these requirements. See paragraphs 15.1 — 15.9 of the Viking Warm Roof BRANZ Appraisal.
Clause F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1. The Viking WarmRoof System meets this requirement and will not present a health hazard to people.
Clause H1 ENERGY EFFICIENCY: Performance H1.3.1 (a). The Viking WarmRoof System will contribute to meeting this requirement. See paragraph 14.1 of the Viking WarmRoof BRANZ Appraisal.
Clause C/VM2 FIRE PERFORMANCE (of wall and ceiling linings) — ISO9705, Group 1S = highest possible rating.

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