September 23, 2023

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H1 Building Code Compliance Tool

H1 Building Code Compliance Tool

On 1st of January 2017 Clause H1 Fourth edition Amendment 3 came into force. It calls up the 2009 version of NZS4218 as Acceptable Solution for Clause H1. NZS4218:2004 including the Clause H1 replacement tables remained an Acceptable Solution until 30 May 2017.

From 1 June 2017 only NZS4218:2009 is the Acceptable Solution for Clause H1.

Below is a list of the most important changes in the new Clause H1:

  • The Acceptable Solution does explicitly exclude the use of foil insulation. (H1/AS1 1.0.2)
  • The maximum permitted area of skylights for using the NZS4218:2009 Schedule Method has been increased from 1.2m² to 1.5m² or 1.5% of the roof area, whichever is the larger. (NZS4218:2009 4.1.1(d))
  • Up to 3m² of glazing with an R-value of less than R-0.26 (“decorative glazing and louvers”) is permitted in the NZS4218:2009 Schedule Method. (NZS4218:2009 4.1.1(c))
  • The maximum of 50% glazing for using the NZS4218:2009 Calculation Method has been retained. NZS4218:2009 refers to a limit of 40% (4.2.1), however, this is modified in H1/AS1 2.1.6 to 50%. (H1/AS1 2.1.6)
  • When using the NZS4218:2009 Calculation Method to trade off R-values the lowest permitted R-value for walls, floors and roofs has been reduced from 60% to 50% of the corresponding Schedule Method R-values (the old “60% rule” is now a “50% rule”). There are no mimimum R-values for glazing. (NZS4218:2009 4.2.8)
  • In the NZS4218:2009 Calculation Method the reference building glazing R-values for glazing in excess of 30% of the wall area have been increased. (NZS4218:2009 Tables 5, 6 and 7)
  • The reference building in the NZS4218:2009 Calculation Method does not have any skylights. The roof area of the reference building consist of the sum of roof and skylight areas of the proposed building. (NZS4218:2009 Tables 5, 6 and 7)
  • Up to 6m² of opaque door can be ignored in the heatloss calculation of the NZS4218:2009 Calculation Method. (NZS4218:2009 4.2.7 and H1/AS1 2.1.7) (Note that for simplicity reasons this feature has not been implemented in the DesNav calculator. Most doors in modern houses consist largely of glazing, which has to be included in the window area anyway.)
  • Only recessed downlights that can be safely abutted to (CA rated) or covered with insulation (IC rated) can be used. (H1/AS1 2.1.4)

The easiest way to show compliance for additions and alterations is to show compliance for the whole building rather than only for the changed parts. That means you enter all external floors, walls, roofs and windows whether they are existing or new.

The trick is that for all existing unchanged parts you can assume that they comply with the Schedule Method R-value targets (Table 2 in NZS4218:2009), irrespective of whether they in reality do. So you would for example enter for all existing windows an R-value of R-0.26, even if they are single glazed.

If the R-values of the existing parts are known and higher than the Schedule Method R-values then you can even use these R-values.

Only for the new and changed parts of the building you use the actually proposed R-values for these elements.

Any walls or other elements that used to be external, but are now internal elements will be ignored as usual.

This method follows the approach in NZS4218:2009 Appendix D3.

There is also a message trail on the issue on the DesNav message board.

The NZS4218:2009 Table 2 R-values are:

Zone 1 Zone 2 Zone 3
Roof R-2.9 R-2.9 R-3.3
Wall R-1.9 R-1.9 R-2.0
Floor R-1.3 R-1.3 R-1.3
Glazing (vertical) R-0.26 R-0.26 R-0.26
Glazing (skylights) R-0.26 R-0.26 R-0.31

Pod insulation systems consist of insulation pods (usually polystyrene) placed underneath the slab. Concrete channels separate each pod and provide structural stability.

The R-value of pod insulation systems is quite complex to calculate and the literature is conflicting.

Two relevant references are a BRANZ article published in the BUILD magazine in 2011 (BUILD 123 April/May 2011, page 26) and the Firth RibRaft Design Solution Brochure.

The BRANZ article is based on thermal computer simulations and found that “…for a traditional slab-on-ground floor without insulation … the thermal resistances of the (pod insulated) floors are similar for a building with 100 mm deep walls.” For 250mm deep walls the simulations found an R-value increase of 20% compared to an uninsulated slab.

The Firth Design Guide on the other hand refers to NZS4214:2006 and lists quite significant R-value increases due to the RibRaft system. It should be noted that the referenced Standard does not specifically cover pod insulation systems and only deals with total slab insulation and slab edge insulation.

Because of these conflicting resources I recommend to either ignore any benefits of the pod insulation systems in the DesNav calculations and treat the slab as uninsulated or to use a “custom R-value” and enter the BRANZ or Firth R-values manually and add a corresponding reference to the consent application.

The short answer: Yes

The long answer:

The first question is always whether the building has to comply with the thermal targets of Clause H1 at all. The screen shot below shows the relevant section in Clause H1.

H1 Building Code Compliance Tool

If the building does not fall into one of these groups, i.e. if it is not exempt then you have to comply with Clause H1. In that case the permitted compliance method depends on the building size and type.

  1. Smaller than 300m² or housing of any size: The NZS4218 Schedule and Calculation Methods are the Acceptable Solutions for all buildings smaller than 300m² and for all housing irrespective of size. That means that for example also an apartment building must comply with NZS4218. It also means that a small office which is smaller than 300m² must comply with NZS4218.
  2. Non-housing larger than 300m²: If the building is larger than 300m² and it is not housing you have two options: Show compliance with NZS4218 (Schedule or Calculation Method) or show compliance with NZS4243 (Schedule or Calculation Method). Both of these standards are Acceptable Solutions. The reason why most designers will show compliance with NZS4243 instead of NZS4218 is that the R-value targets in NZS4243 are a lot lower than the targets in NZS4218.

The DesNav program tests compliance with NZS4218 Schedule and Calculation Methods.

So that means that you can use the DesNav calculator to show compliance with Clause H1 also for a non-housing building larger than 300m². If the building fails to comply you can either increase the insulation levels to meet NZS4218 (using the DesNav calculator) or instead you check whether it complies with NZS4243 (which is not part of the DesNav calculator).

Note that for some large non-residential buildings you also need to show that the lighting power density complies with Clause H1. Usually your lighting consultant will be able to do these calculations for you.

PS: I am also providing professional services to do NZS4243 H1 calculations. If you are interested you can send me the building plans to [email protected] and I can give you a quote.

Since 1 June 2017 the NZS4218:2009 (Schedule and Calculation Method) is the Acceptable Solution for Clause H1 of the Building Code. The previous standard (NZS4218:2004) is no more called up in Clause H1 as an Acceptable Solution.

This version of the Design Navigator H1 calculator uses NZS4218:2009, including ammendments from Clause H1 Fourth edition Amendment 3 from January 2017.

  • If I make changes to a paid project do I have to pay again?

    No. Once you have paid for a report you can make as many changes to the project and download a new copy of the report free of charge.

    Just be aware that if you create a copy of the project you would have to pay again for the report of the copied project.

  • Do I also have to pay for old projects?

    No. Reports for projects that were created before the 19th of February 2015 remain free of charge.

  • How does the payment system work?

    The payment system is set up so that when you open the report page you have two choices, either pay by credit card or be invoiced.

    If you select credit card it redirects to a separate ASB website where you do all the credit card stuff. Once that is done it returns to the DesNav page and e-mails you the report and a receipt.

    If you choose the invoice option the DesNav website will send you the H1 report and together with it an invoice.

    There is also a monthly invoicing system available that collates all invoices during each month. Please let me know if you would like to have an account set up for this.

    I hope is convenient to you.

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