Question on min. R-values

[lin]

Hi,

On the Design Navigator H1 Compliance Calculator
2. Performance Targets-Calculation Method
all the individual components must have at least the following R-values:
Floor 0.8, walls 1.1 .....

Where are these min. R-values from?? NZS 4218? I really can not find this information, can you get me a bit help to show me where is that from?

Thanks a lot

[Albrecht Stoecklein]

Hi Lin,

The Calculation Method in NZS4218:2004 allows you to reduce R-values in certain building elements as long as you increase them in other components so that the overall heat loss of the proposed building is smaller than that of the reference building. But the NZS sets a limit by how much you are allowed to reduce these R-values, even if the heat loss of your proposed building is smaller than the reference building heat loss. So you can for example usually not get away with removing all the wall insulation and make up for it by increasing the roof or floor insulation.

This minimum insulation level for the Calculation Method is 60% of the R-values which are listed in the tables for the Schedule Method. The NZS4218:2004 refers to this rule in Clause 3.2.6. These 60% values are the numbers shown on the DesNav screen and report.

Sunny regards

Albrecht

[hshhuang]

Hi Albrecht

I am also a bit confused about the minimum R values for different building conponments when using the calculation method. I have a mixed construction type building with mostly masonry walls and some timber framed wall. I can see there are different figures for solid construction and non solid construction when it comes to minimum R value(table 1 and 2 of NZS4218-2004). Also, H1 compliance doucments "replacement tables" have tables with same titles but different minimum R-values. I suppose the H1 tables supercede those in NZS 4218:2004??? Also, if I have a block wall (solid construction) In H1 replacement table 2(b) Option 1a Wall, the minimum R value is R 0.8 for the schedule and that means for calculation method the minimum should be 60 Percent of R0.8 which is R 0.48. Is that correct??? In the design navigator tool, I seems to be getting a much higher minimum( I suspect it's one from non-solid construction )? Could you shade some light on these question please.

regards

Jason

[Albrecht Stoecklein]

Hi Jason,

Yes, the DesNav calculator takes a simplistic approach to that. But I was working on an upgrade just last week to allow combinations of different wall types in the same building. I hope to complete that by next week.

For the moment the DesNav can not deal with buildings with mixed constructions, i.e it means that you have to treat the whole building as non-solid. But if the 60% minimum values are the only reason why it fails you could probably just add a note to the report explaining the details.

In regards to the actual values you are correct that the DesNav uses the values which are directly referenced in Clause H1. The values in NZS4218:2004 are outdated.

One additional thing you have to keep in mind is that you also have to meet the R-value targets in E3. That requires the following R-values.

For light timber frame wall or other framed wall constructions with cavities: R-1.5
For single skin normal weight masonry based wall construction without a cavity: R-0.6
For solid timber wall systems no less than 60 mm thick: R-0.6
For roof or ceilings of any construction: R-1.5

So your masonry wall must still have at least R-0.6.

As soon as you strap and line it if becomes a cavity wall and you have to use the non-solid R-values in both H1 and E3.

I trust that helps.

Sunny regards

Albrecht