Three revised New Zealand Earthbuilding Standards are out for public comment. This is a great opportunity—very time limited—to review the content of the draft standards without having to purchase them.
These are only available until 26 May 2024. Download the files here. There is general background on the Earth Building Association of New Zealand (EBANZ)’s website, available here.
These standards are not sponsored by MBIE and will not be available unless purchased once they are finalised. Unlike standards such as NZS4214:2006 Methods of determining the total thermal resistance of parts of buildings. If you didn’t know, MBIE has sponsored over 120 building industry Standards, making them available for free download in order to “remove barriers to achieving compliance”.
The revised standards are important in light of the higher H1 requirements introduced to the NZ Building Code last year. Earth-based buildings now need to either have similar insulation to a timber-framed buildings or must use dynamic modelling to show they perform as well as a building that has those high R-values. Some types of natural materials, such as straw bale buildings, easily meet these R-value requirements (see Hiberna Passive House, for example). However rammed earth, cob or adobe brick buildings will either need a dynamic thermal model or to specify insulation inside the walls.
Sustainable Engineering Ltd’s team has experience with the dynamic thermal modelling required to demonstrate Code compliance. We can also provide hygrothermal modelling, which can be used to assess how heat and moisture travel through building assemblies. Senior Analyst Jessica Eyers is experienced in architectural design, Passive House design and designing strawbale houses. She says that hygrothermal modelling has a lot of value for non-standard (non NZS3604) materials and assemblies, both in improving design and demonstrating compliance.
Modelling also addresses many of the challenges and benefits of building with these high thermal mass materials. Many years ago we modelled the Kawakawa Library and Service Centre* which is located in the Te Hononga Hundertwasser Memorial Park. This rammed earth SIRE wall building is incredibly efficient and the dynamic thermal models were used to review internal moisture levels for the books and artworks contained in this unique building. It’s semi-tropical climate and high summer visitor numbers adds to its complexity.
Project Designer Pip Bolton of Avail Pacific and Jason Quinn of Sustainable Engineering touring the site during rammed earth wall construction. Photo: © 2019 Sustainable Engineering Ltd
Here’s the building completed, with a late night glimpse of those gorgeous and super-insulated rammed earth walls. It’s been built to last hundreds of years (a normal aspiration for a house where I hail from in NE USA, but sadly unusual in Aotearoa). You can learn more about the background and details to this remarkable building in this rather bonkers write up by the plumbing team on the job.
Photo credit © 2021 Sustainable Engineering Ltd
“Traditional building materials like earth have been used for millennia and their embodied carbon emissions are very low. Passive House methodology is barely 40 years old—its genius lies in radically reducing operational carbon emissions,” notes Jessica. “There’s a real opportunity to combine the old and new to create long-lasting, extremely comfortable and beautiful buildings that work toward our urgent climate goals.”
Sustainable Engineering certified this Passive House home (pictured above, case study here), which uses light earth for internal walls and strawbale construction for the external walls, all finished in natural plaster. Clay, strawbales and timber were locally sourced. The biggest embodied carbon component is a concrete slab, which supports the weight of the plaster and made it much easier to achieve universal accessibility.