The very first thing to check is whether the building is going to utilise energy from a network utility operator or uses any depletable energy sources. This is usually the case, but it would exclude for example a lifestyle home that has it's own solar power panels for electricity and uses firewood for space and water heating. But as soon as it would use LPG gas for example the exemption wouldn't apply because LPG is depletable.

The next step to check is whether the building falls in one of the building classifications that do have to comply with the thermal requirements of H1.2(a). Specifically assembly service buildings, industrial buildings, outbuildings, and ancillary buildings do not have to comply with the thermal requirements of Clause H1. The screen shot below shows the relevant section in Clause H1.

A description of the classified uses with some examples is in Schedule 1 of the Building Code.

If the building does not fall into one of these groups then you have to comply with the thermal section of Clause H1. In that case the permitted compliance method depends on the building size and type.

All of the Acceptable Solutions (AS1 Edition 4, AS1 Edition 5 and AS2 Edition 1) include a Schedule Method and a Calculation Method. The Schedule Method is a simple lookup table of R-values that your design has to meet. The Calculation Method allows some trade-offs between R-values in one element agains those in another. For example you can drop the roof insulation if you increase the wall insulation, etc. There are some prerequisites for using each of these methods and some additional requirement to meet the compliance requirements whch are specific to each version and edition of the Acceptable Solution. These conditions are all automatically checked within the Design Navigator Calculator. The Design Navigator Calculator also shows on its report pages why the design complies with a certain method or not.

One important thing to remember is that all of the Acceptable Solutions only assess the R-values of the building. They do not assess other thermal features such as solar exposure, thermal mass, internal air flows, etc. Although thermal insulation (R-values) are by far the most important factor for the thermal performance of a building looking at only the R-values can in some cases not give the full picture of a building's thermal performance and comfort.

The Verification Methods (VM1 Edition 4, VM1 Edition 5 and VM2 Edition 1) require a full scale thermal modelling of the building. Such a model simulates the building's heat flows and temperatures on an hour-by-hour scale for a typical climate year taking account the thermal insulation, but also factors such as solar gains (orientation of the building and window sizes), thermal mass, and it may even look at infiltration and ventilation effects. Such a model also looks at different thermal zones within a building. This allows the consideration of different comfort requirements throughtout building, i.e. a living room may be kept at 20degC whereas a bathroom at 16degC. These thermal simulations are reasonably complex and the Design Navigator calculator does therefore not include this assessment method. But I can undertake a Modelling Method assessment for you on a consultancy basis if you are interested.

The new Clause H1 Edition 5 unfortunately doesn't provide any clear guidance on alterations and additions. The Building Act says that if the building did not comply with the provisions of the building code immediately before the building work began, it has to “continue to comply at least to the same extent as it did then comply”. But in regards to energy efficiency performance it is not that clear what “the same extent” means.

If you only replace some building elements and don't change or add any additional elements then you can interpret that to say that you just must not reduce any R-values. But if it involves some additions to the building or other element alterations such as changing window sizes it becomes more complicated.

In those cases I recommend to use the approach that is described in NZS4218:2009 Appendix D. That suggests to assess the whole building, rather than just the new parts. But the trick is that for any existing unchanged parts of the building you can for calculation purposes assume that they have R-values meeting the Schedule Method targets (H1/AS1 Ed.5 Table 2.1.2.2B), irrespective of their actual R-values. Only for any new or changed elements (walls, windows, roofs, floor) you will have to calculate and use their actual construction R-values.

So for example if your existing building has R-1.7 walls, you can still enter R-2.0 for these existing walls in the DesNav calculator, as if they are meeting the current Schedule Method target. Only for those elements that are new or have been modified you enter their actual R-value.

There is a DesNav construction R-value option for these unchanged existing elements. Make sure you select the option for the *current* H1 edition, i.e. the one you are checking for compliance for, rather than the H1 edition when those existing elements were built. So usually you should select one of the H1 Edition 5 options:

Internal elements between the new and the old part of the building are ignored just like normal internal walls, midfloor, etc.

You can only use those “default” R-values for existing parts that were residential and had to comply with H1 before. So if you are for example converting an existing garage into a living space you would need to use the actual garage R-values, meaning that you would probably have to insulate it, in case it wasn’t insulated before.

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.

AS1 Edition 5 includes an extensive list of slab R-values which have been calculated independently without references to NZS4214:2006. These tables also include some scenarios for slabs with pod insulations. The tables have been implemented in the Design Navigator construction R-value options.

These R-values can also be used for designs that show compliance with AS1 Edition 4.

If a particular slab detail for a pod insulation floor is not included in the available options I recommend to use one of the options which don't include the pod insulation because the pods have only a minor impact on the slab R-value.

AS1 Edition 4

In AS1 Edition 4 you have some flexibility. It allow to show compliance for large building using either NZS4243 or NZS4218. NZS4218 is the method that is implemented in the Design Navigator for AS1 Edition 4 compliance.

That means that you can use the Design Navigator calculator to show compliance with Clause H1 AS1 Edition 4 also for a building larger than 300m². If the building fails to comply you can either increase the insulation levels to meet NZS4218 (using the Design Navigator 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.

AS2 Edition 1

Since November 2021 a new Acceptable Solution is available for buildings larger than 300m² that are not housing. This is "AS2 Edition1".

As with housing and buildings smaller than 300m² it includes a Schedule and a Calculation Method. The target R-values have been significantly increased compared to the NZS4243 which listed the target R-values for AS1 Edition 4.

The Design Navigator includes AS2 Edition 1, i.e. the Schedule and Calculation Methods for large buildings.

Simply enter your data as usual and select the AS2 Edition 1 assessment option.

The Design Navigator assessment also includes the Lighting Power Density calculation. You can use that in case your lighting designer does not provide the compliance statement for the lighting.

PS: I am also providing consultancy services to do H1 calculations for large commercial buildings. If you are interested you can send me the building plans to designnavigator@gmail.com and I can give you a quote.

You may have come across cases where an R-value has changed from the value that you previously calculated with the Design Navigator calculator.

There can be a few reasons for that:

• It may simply be that I made a mistake in specifying the R-value for a certain material or insulation product. I obviously check the numbers and try my best to avoid this, but I am human, and errors do happen.
• In other cases I may have simply updated a previous R-value when more accurate information became available. For example I may have used a default value from the literature but some new research has come up with more accurate values. Usually these corrections are fairly small and are less than R-0.05, but depending on the material and where in the consruction assembly it is used the differences can be larger. I usually use fairly conservative (low) default R-values when no specific information is available. So in general these corrections would lead to improved R-values in later versions of the calculator.
• There are also instances where insulation manufactures or suppliers provide updated data on their products. This may be because they changed their manufacturing process or for some other reasons why they had to adjust the R-values from their original literature.
• In some rare instances I also change the way the construction R-values are calculated. The method that Design Navigator applies is always based on Clause H1 which generally refers to NZS4214:2006 for the methodology to calculate R-values. Although this Standard is usually quite prescriptive there are cases where it leaves some room for interpretation. One such example are assemblies with immediately adjacent insulation layers, such as for example a timber framed wall with an additional insulated counterbatten layer. In these instances I generally follow the most intuitive approach, but if that leads to some problematic scenarios which seem inconsistent with actual data measurements I update the methodology. This can sometimes lead to quite significant changes to the calculated construction R-value. I therefore make these changes only when there are compelling reasons to do so and only if there is scientific evidence showing that the alternative approach leads to results that are more in line with real measurements. I usually also announce it when these types of substantial changes happened.

Are the R-values automatically updated for existing projects?

Generally no.

When the Design Navigator program saves a project, it does not only save the selected detail name, but it also saves the corresponding R-values and also the other options that were avalable for that component. This makes it backward compatible. Assume for example that I change the name of a cladding product or remove it all together because it is no more on the market. If the calculations for your saved project would refer to the new Design Navigator version the calculation would crash because it couldn't find the product anymore. Therefore all the products that were available for your selected construction detail are saved and restored when you re-open the project.

The other reason is that it would be quite confusing if you would create an H1 report for a project, and when you open the project again some time later the new R-values - and possibly even compliance results - would be different from the ones in the report that you created earlier.

There can of course be cases where you want to use the new product or an updated R-value for that product. In that case you will have to create a new construction R-value. Then simply select the same details as for your old construction R-value calculation in your project. Because you created a new construction the program will in that case use the current product names, R-values and calculation methods.

F.1.2.2 says:

That's a recommendation only, and not mandatory.

But there are a few implications on how to calculate the slab R-value:

1. If there is no edge insulation around the external walls it won't make any sense to add edge insulation between the garage and the house. So without that internal edge insulation the slab R-value calculation is simple. The slab area excludes the garage and the perimeter length includes the external house perimeter and the garage/house joint length, but not the external garage perimeter.
2. But if there is edge insulation around the rest of the house it gets a bit tricky. If you would place edge insulation around the external garage walls then it would be useless, unless you include the whole garage in the thermal envelope, i.e. insulate the garage walls and roofs as if they are part of the house. But if you don't want to include the garage in the thermal envelope the only way would be to add edge insulation between the garage and the house, as the Clause F.1.2.2 recommends. Then the R-value calculation is the same as in the first scenario, but this time with edge insulation.
3. But what to do if you have edge insulation around the rest of the house but exclude the garage from the thermal envelope and have no edge insulation between the garage and the house? As you can see in the DesNav calculator there is only an option for having edge insulation or having no edge insulation. There is no option for having edge insulation only around 80% of the perimeter (assuming for example that the joint length between the house and the garage makes up 20% of the total perimeter.)
   1. Simple option: In that case you just calculate the R-value with no edge insulation. You would use the perimeter length including both the actual external house perimeter and the joint length between the garage and the house (but not the external garage perimeter). That R-value will be a bit smaller than the actual R-value, but that would be a simple practical approach.
   2. Accurate option: If you want to be more accurate you could calculate both the R-value for the “no edge insulation“ scenario as explained in the “simple option” (RNoIns) and calculate the R-value with edge insulation RIns using the same dimensions as in the simple option. Then you can calculate the “average” R-value. But R-value averages are not “normal” averages. You will have to use this formula:
      100% / (%PerIns/RIns + %PerNoIns/RNoIns)
      With:
      %PerIns the percentage of the insulated external house perimeter (80% for example) and
      %PerNoIns the percentage of the uninsulated garage joint (20% for example)
      If for example the edge-insulated slab R-value is R-1.65 and the edge-uninsulated slab R-value is R-1.4 then the average R-value would be 100/(80/1.65 + 20/1.4) = 1.59