Building at scale? Volume certification makes Homestar simple

04 February 2019

by Danidu Wijekoon, NZGBC

We are constantly looking at ways to make our rating tools better, more accessible, and easier to use. If you design and/or build a large number of houses based on standardized blueprints across multiple developments or subdivisions, we have a useful new pathway to certify them under Homestar.

Why certify a house in the first place?

I can say I’m from Mars, but that doesn’t make it so, and you probably won’t believe me unless my birth certificate said so - it doesn’t by the way - and even then, it’s a stretch.As a reputable company you will go to extra lengths to ensure that the homes you design and/or build are of high quality, won’t make residents sick, will keep them comfortable through all seasons, and won’t cost the earth to live in (considering they’re likely to also be paying off a mortgage for the next 20 – 30 years). However, others may not build quality houses like that. Of course, you will market these homes on the benefits they are designed to provide, and talk about how it’s a home, not just a house. However, so will those others.

So how does the market know who to believe? This is why you certify with a Homestar rating and get that independent stamp of quality.

However, it can be time consuming to get an assessor to complete a Homestar assessment all over again each time a house based on a standard design typology is built on a new development. By contrast if multiple houses of a single typology are built in the same development you only have to assess the lowest performing one. This is the criteria we use because some credits within Homestar depend on orientation, shading, site attributes, waste management practices and other criteria that vary from location to location even where houses themselves are identical.

The new volume certification pathway rolled out in late 2018 does just this, and the first volume certified project was successfully completed in December.

Homestar is a credit-based system, where each credit has a number of points awarded for meeting various benchmarks or for providing various features. Volume certification allows any design element (relevant to a Homestar credit) that is standard across some or all your designs to be assessed at a plan level and the associated points ‘pre-confirmed’. In addition, the Quality Assurance process you have in place to ensure that houses are built as per their design, as already assessed, is evaluated. Then each time that design is built on a new development only a sample onsite verification is required to confirm the associated points under Homestar.

This could just be one or two items. For example you might use the same paint products across all developments and all house plans, and under volume certification all these plans can have qualifying points available under the ‘Applied Coatings’ category in MAT-1 and MAT-2 credits pre-confirmed. Then every time a house based on one of these plans is built the aforementioned points are already there, requiring an assessor only to verify this on site on a sample of builds.

On the other end of the spectrum an entire design can be assessed and rated. For example, say you are targeting a 6 Star rating for all houses built across a number of standard plans. The EHC-1 (Thermal Comfort) credit is the only mandatory credit that is impacted by location and orientation and to get the 12 required points you just need to ensure the design thermal envelope meets or exceeds the minimum construction R-values that is specified for the climate zone the house is built in. There are only four climate zones so only four sets or R-values and the compliance pathways are set up just like that for Building Code H1 (NZS4218 schedule or calculation methods).

This means you can submit each plan with a different insulation specification for each zone you plan to build in (or you could go for the nuclear option and have one spec that covers requirements for all zones), which may be possible without changing the rest of the design much, or at all depending on design decisions.The other mandatory minimums are location independent and so are plenty of other credits that will help you get enough points to meet the total of 60 required for a 6 Star rating.

The key is to consider this during the design process, where decisions around glazing, frame thickness, etc. can have an impact on how feasible it would be for an unchanged design/ specification to achieve a 6 Homestar rating (or higher) regardless of location or orientation. Some level of standardization across multiple typologies and careful selection of product ranges also helps.

If this can be achieved, the entire portfolio of plans may be pre-certified, effectively getting each plan an unofficial design rating. Then when these plans turn into houses across multiple developments a sample of features across a sample of houses in each development is verified and signed off by an assessor (rather than full assessments across a half a dozen typologies in each development) and the 6 Homestar ratings awarded en masse. Once a plan is pre-certified it is valid for three years, after which the certification can be renewed at discount. (This does require a re-submission as the plans or the Homestar tool could have been updated.) Also, any development with houses based on a pre-certified plan will get a discount on registration fees based on the number of points pre-confirmed, and any plan with at least 40 points pre-confirmed comes with a “Homestar-pending” logo that you can use for marketing.

Whether Homestar is offered as standard, or an added upgrade, what this does is enable you to market a product with certainty that it will get the desired Homestar rating and with associated costs and time requirements, not to mention the associated legal risks minimised. So, if you are group home builder, designer, social housing provider or a developer working at scale to deploy standard housing products around the country but haven’t quite dipped your toes in Homestar waters yet, this is your chance. If you’re interested, don’t hesitate to contact the NZGBC technical team for more information.