H1 Compliance Calculator

Christmas and New Years Special


Need an H1 report in a rush?

Have your H1 calculations done by us. For a short while we offer to do your residential H1 calculations for you. Prices start from $200+GST and turn-around times are usually three days or less.


Just send me your plans (as PDF files) together with your preferred insulation type (designnavigator@gmail.com). I'll have a look at them, let you know whether I need more details and and will give you a quote.

I hope this takes a bit of the pre-Christmas pressure away and you will enjoy a relaxed and wonderful Christmas and New Years break.

Sunny regards

PS: In case you are wondering: We can also do H1 calculations for commercial buildings.

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This website calculates compliance with insulation targets of NZBC, Clause H1 as of 10 October 2011. It calculates compliance with the New Zealand Standard NZS4218:2004, Schedule and Calculation Methods, using the R-value targets from NZBC/H1 (October 2011) and for compliance with the Building Performance Index (BPI).

On 1st of January 2017 the new version (2009) of NZS4218 came into effect as Acceptable Solution of Clause H1. NZS4218:2004 including the Clause H1 replacement tables remains an Acceptable Solution until 30 May 2017. Over the next few weeks I will update the DesNav calculator to refer to NZS4218:2009 rather than NZS4218:2004.

The Calculator should be used in conjunction with the Energy Efficiency Clause H1 of the New Zealand Building Code and NZS4218:2004, which can be purchased from Standards New Zealand.

You can create as many Design Navigator projects as you want free of charge. Once you have finished a project and download a completed H1 report a fee of 26.40+GST applies. Payment can be made via invoice or credit card. Please contact me if you want to have an account for monthly invoices set up.

Payment Update: You can now pay for your H1 report using direct credit with the POLi online payment option. POLi is safe payment system used also by some other large companies such as The Warehouse and Air New Zealand.
Notice: The Internet Service Provider will need to shut down the server that is hosting the Design Navigator website for maintenance between Start time: 06/12/2016 23:00 NZDT End time: 07/12/2016 03:00 NZDT.
The server crashed late morning on 21 March 2014. The ISP has recovered the database, however some projects created on the 20th and 21st March might be corrupted or deleted. There was another crash on 25th March that may have also corrupted some data. Sorry about this.
The Design Navigator will be turned off for several hours Tuesday night.

There currently is a bug in the Design Navigator H1 calculator, which is probably caused by changes which the ISP implemented recently.

Projects cannot be saved if they include a *previously* created construction R-value calculation table (view screen shot). The bug does not seem to occur for projects with *newly created* construction R-value tables.

You can still modify old projects and print the reports. You can also save projects, but before you do that you have to replace the old construction R-value tables with newly created ones, even if they are for the same detail.

I am working on fixing the problem.

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Click here to use the H1 calculator without saving and printing of projects.

Note: I am regularly adding further improvements to this calculator. I am always trying to conserve any previously saved projects but suggest that you keep printed copies of the compliance reports so that you can reproduce the results should the database records be damanged.

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Training Videos

Introduction tutorial:

Tracing scanned floor plans:

Home This tool was created by Design Navigator Ltd.

Additions and Alterations

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 apply with the Schedule Method R-value targets (Replacement Table 1 in NZBC H1), 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. Note that this version of the Standard is not an Acceptable Solution (that is still NZS4218:2004), but most BCAs will accept this approach since there is no alternative method recommended in NZS4218:2004.

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

The H1 Replacement Table 1 R-values are:

Zone 1Zone 2Zone 3
Glazing (vertical)R-0.26R-0.26R-0.26
Glazing (skylights)R-0.26R-0.26R-0.31

Slab Pod Insulation Systems

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.

Can the DesNav Calculator be used for commercial buildings?

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.

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 designnavigator@gmail.com and I can give you a quote.

NZS4218:2004 or NZS4218:2009?

On 1st of January 2017 the new version (2009) of NZS4218 came into effect as Acceptable Solution of Clause H1. NZS4218:2004 including the Clause H1 replacement tables remains an Acceptable Solution until 30 May 2017. Over the next few weeks I will update the DesNav calculator to refer to NZS4218:2009 rather than NZS4218:2004.

Old - still valid explanation for NZS4218:2004.

NZS4218:2004 is an "Acceptable Solution" called up in Clause H1 (page 9, 3rd edition from October 2011).

Since 2011 Clause H1 contains a number of "replacement tables" with minimum target R-values. These replace the minimum R-values in NZS4218:2004. Incidentally the values in the H1 replacement tables are largely the same as the values in NZS4218:2009.

But all the other requirements such as the maximum permitted windows and skylight areas, etc. must still be taken from from NZS4218:2004.

The BCA must therefore accept calculations based on NZS4218:2004 and the replacement R-values tables as "Acceptable Solutions".

The good news is that the DesNav calculator automatically takes care of the confusing situation when checking for compliance.

PS: The BCA can of course at its own discretion accept compliance reports based on NZS4218:2009 as "Alternative Solutions", but it is not obliged to do so.

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