Hempcrete buildings and Passivhaus buildings have equally well-deserved reputations for performance and liveability.
The critical points in any Passivhaus build are the joints between components. The Passivhaus Planning Package (PHPP) is highly analytical of thermal bridges, but most Australian buildings take little or no account of this. Air-tightness is also critical, proven by a blower door test that must achieve an air leakage rate of no more than 0.6 ACH at 50Pa with building details that do not allow thermal bridging.
For a hempcrete build, the floor-wall joint and the wall-roof joint are critical and as yet not commonly detailed in the design industry. Window and door frame sealing is also critical but less uncommon.
Part 1 of this paper presents an example our method of combining Passivhaus taping technology with traditional hempcrete sealers to achieve 0.6 ACH-50.
NCC 2022 was conceived as a way of ensuring high building standards while also allowing innovation to flourish. It may be achieving the first objective, but may be failing failing in the second.
Volume 1 (non-residential) Part F3 is concerned with health and amenity, contains performance requirements for roof and wall cladding. Cladding here means an external weatherproof skin, regardless of the material or how it is attached to the structure.
The significant difference between Volumes 1 and 2, and from the 2016 edition of Volume 1, is that expert opinion is no longer an acceptable pathway to satisfying the verification method contained in verification method F3V1.
The requirements in F3V1 effectively limit testing to a NATA registered facility. Experience has shown that a single test will cost a minimum cost of tens of thousands of dollars.
This is an impediment to innovation, where materials and systems that have proven effective, sometimes for thousands of years, can no longer be used. Or where a small scale producer, or a materials start up, with some innovative new or adapted material, is effectively barred from any non-residential project.
Innovation must allow for the new, for the appearance of things that have not yet stood the test of time, without such high cost that only established ‘majors’ in the materials supply chain can afford that kind of testing.