Homestar was first launched in 2010 after having been developed by the New Zealand Green Building Council (NZGBC), BRANZ and Beacon Pathway as a nationwide scheme for applying an objective rating to stand-alone houses as a measure of their environmental performance. With the rapidly developing interest in the rating scheme, 'Version 3' of the Homestar Tool has been released, formally bringing apartments and terrace housing into the assessment process. These types of domestic accommodation cannot be equated with the suburban house on its own site, so alternative means and aspects of measurement were needed to more adequately reflect the performance of these forms of dwelling.

The Homestar assessment process looks at much more than the NZ Building Code requirements for the proper construction of a building. While half the points towards the maximum 10 star rating are concerned with aspects of energy, health and comfort, the assessment also evaluates waste and home management, water usage, materials and site. Innovation in design can be rewarded, as can smaller dwellings, but as house size increases above the average and the density factor is lowered, there is a downgrading to account for the proportionally greater resources consumed.

To encourage more sustainable design and life-time performance, there are also mandatory minimum levels of performance for core aspects of the building. If these stages are not met then a greater rating is not available, even if the other aspects would justify a higher rating. This makes it important to have the Homestar requirements considered as part of the brief for the design, and even thought of before the site is purchased. Homestar has now become well established, even to the extent where local authorities are introducing minimum Homestar ratings for some new building developments, and developers are beginning to mandate minimum ratings for their subdivisions and projects.

In the past, as both a practitioner and assessor, I have met significant resistance to the concept of Homestar from designers, architects and real estate agents. However, with councils becoming interested in making minimum ratings part of their development requirements, it is probable that the property market will latch onto the concept more quickly than might be thought. After a short time star ratings for kitchen appliances became a standard consideration for the purchaser. At the Auckland waterfront a 7 star rating is being applied to some sites, and a sub-division north of Auckland requires a 6 Homestar rating for all houses to be built there.

In my opinion, it is unwise for a property owner to not look towards the future when designing their new home. Despite the current general lack of interest from the building industry (apart from where the councils are making demands), I expect that by the time property owners come to sell the house after seven years there will be a premium on having a star rating. At present much of the New Zealand housing stock would only achieve 2 stars as they don't reach the thermal performance needed to progress to 3 stars. Even if the owner does not particularly believe in star ratings, the better performance of the thermal aspects of the dwelling will be a worthwhile investment over the life-time of the building, especially considering that 'purchased energy' will increase in real cost over time.

As both an architect and a Homestar Practitioner and Assessor, I consider that a 6 Homestar rating can be achieved without too much difficulty, but it requires a positive attitude to design to ensure the target is reached. If there are no council or developer minimum requirements, then if the anticipated final rating is missed there is no major problem. On the other hand, if the minimum is mandatory, then it is a different matter. With the normal planning requirements of car parking, site coverage and envelopes, view-shafts, vegetation areas etc., it is easy to determine compliance with these single issues at the time of developed design, and they can be fixed from that stage on. The Homestar Built Rating is an entirely different matter.

To begin with, the Homestar assessment is of the dwelling as it has been built and, as all in the building industry will know, what is on the drawings and described in the specifications is not necessarily what has been constructed (the building consent amendment process anticipates changes may be made). The aspects to be considered for the assessment are many and varied, and so small changes can combine to result in a lowered final rating. Until the building is constructed, the rating cannot be assured. With this in mind, it is my view that the designer should aim significantly above any required minimum and check very carefully before authorising changes. As an example, an on-site change of thermal insulation material may result in the required R-value not being achievable within the wall thickness available. The assessor has strict evidential criteria to comply with, and to submit to NZGBC if a feature is to be included in the assessment. Assessment points can be lost very easily. For the purposes of council consents and market promotion, a 'Design-Rating' can be assessed, but this needs to be followed-up with a formal 'Built-Rating' issued by NZGBC.

I became a Homestar Practitioner in 2011 and an Assessor in 2012. As such, and with my practical knowledge as a Registered Architect, I am able to provide comments on projects during the design phases and to undertake formal assessments, all as an independent professional.