Homestar Technical Clarification Rulings
| Clarification Type | Tool Version | Month Released | Credit Name | Tool Category | Amendment/Approved Ruling |
|---|---|---|---|---|---|
| Technical Clarification | V5 | October | EN | All projects (including attached dwellings and apartments) registered from September 1st, 2023 must achieve at least 1 pt in EN2. This means, in practice that all projects must complete a full (modules A-D) greenhouse gas life-cycle assessment of the building. Assessments of non-NZ3604 style homes (e.g. apartments) can now be carried out using the Greenstar Embodied Carbon Calculator, which is available on the NZGBC website. | |
| Technical Clarification | V5 | October | HC4 - Moisture Control | HC | 6 and 7 Homestar homes are exempt from the HC4 mandatory minimum fRsi requirements stated in the Homestar v5 Technical Manual. Thermally broken window frames with a minimum R-value of 0.25 are still required for all Homestar v5 projects This ruling is in response to uncertainty regarding the real life moisture accumulation risk of certain junction thermal bridges in New Zealand climates. The fRsi guidance provided in the Homestar v5 Technical Manual is based on static modelling with the threshold of eliminating any moisture occurring at the junctions. The approach of eliminating moisture risk by fully insulating the junctions remains prudent however static modelling does not consider other factors such as the ventilation rate of the conditioned space and the thermal mass of the envelope components. More importantly, static modelling provides no detail regarding the length of time that moisture is likely to be present in any location or if the building envelope is more or less prone to either accumulating moisture or drying out over time. Additionally, there remains several market concerns about the available options for insulating the edges of concrete slabs and concrete mid-floors. These concerns include cost and durability. NZGBC has commissioned dynamic hygrothermal modelling research to re-assess the risk of moisture accumulation over time at specific junctions within typical building envelopes. While this research is being completed and the market continues to respond to any demand for slab edge insulation, NZGBC has made the decision to allow 6 & 7 Homestar v5 projects to proceed without specific fRsi requirements. While slab edge insulation will not be explicitly required for the duration of this Technical Clarification, insulation in this location may be necessary for achieving the requirements of EF4: Energy Use and HC1: Winter Comfort. |
| Project Specific | V5 | October | HC4 - Moisture Control | HC | The NZGBC approves the proposed alternative to meet the thermally broken window frames requirement of HC 4:mosisture control credit by demonstrating through simulation that the surface of the frame at the coldest point meets the ANSI/ASHRAE Standard 160-2021, Criteria for Moisture-Control Design Analysis in Buildings. That is the mould index is below 1 on the internal surface. This alternative approach is accepted because it fulfils the aim of the credit requirement which is to reduce condensation risk on the frames to improve IEQ, reduce risk of mould and increase durability. Also, considering that this is an existing building, there are sustainability advantages from a cost and carbon perspective for retaining the current windows, essentially while meeting the aim of the credit requirement. Please see more comments below: The project must provide evidence that: 1. Occupancy, room volume and ventilation rate for the most conservative apartments be used in the analysis; 2. Ventilation must be continuous and specified as such in the documentation; 3. Ventilation must have acoustic consideration (i.e. openings attenuated or fan noise considered) to reduce the chance occupants will turn off or block the system. We strongly recommend commissioning the mechanical system to ensure it functions as designed. |
| V4.1, V5 | EN3 - Sustainable Materials, MAT1 – Sustainable Materials | MAT, EN | In both v4 and v5 of Homestar, NZGBC advises that the Responsible Products Framework may be used in lieu of the NZGBC’s Framework for Product Certification Scheme. The following Responsible Products Value (RPV) may be converted to the previous levels A, B and C: • RPV 10 or above = Level A • RPV 7 – 9 = Level B • RPV 5 – 6 = Level C New Zealand suppliers and manufacturers who aim to be rewarded for their responsible products in Homestar projects should reach out to GBCA to check if their product's certification scheme is approved. If not approved, they can ask their certification scheme provider to approach GBCA for approval. GBCA Products website Responsible Products Framework | Green Building Council of Australia (gbca.org.au) is updating a list of recognized initiatives and in the interim, please email materials@gbca.org.au for the most current list. | ||
| Project Specific | V4.1 | October | EHC4 – Surface and Interstitial Moisture | ||
| Technical Clarification | V5 | HC4 - Moisture Control | HC | Where the application of an air control system involves a blower door and/or other means of testing building permeability, an airtightness measurement can be taken at the time of application of that system. The tester (who may also be the applicator) will be responsible for the airtightness test result. | |
| General | V5, V-5 | October | LV1 - Inclusive Design | LV | |
| General | V5, V-5 | October | EF4 - Energy Use | EF |
The NZGBC approves that where a project includes a main source of heating (e.g. heat pump, centralised heating system, or electric radiators that satisfy HHA heater sizing requirements) serving as the primary heating source, any secondary heating
The project must show a document that indicate that this assumption has been shared with the client. For example: “This home is capable of meeting the heating requirements of the Homestar standard, on the proviso that the electric fireplace is used for decorative purposes only. If the fireplace is used as the main heating source, it may result in exceeding the allowable electricity demand for the Star rating being targeted.” |
| General | V-5 | LV1 - Inclusive Design | LV |
Under the “Design for Vision Impaired Occupants Checklist”, the NZGBC approves that while the light switches must be within 300mm of a doorway (measured from the edge of the opening); Phone jacks and power points outlets may be located in logical, intuitive and standardized locations (e.g. near bedside tables, near TV, in corners of rooms where a lamp or table is likely to be placed, etc). This flexibility is granted in recognition that these locations align with expected occupant use and ensure accessibility through familiarity and predictable |