12th April, 2016 | Jessica Hogg
Working in the construction industry as an environmental engineer can be disheartening at times, as you watch key attributes of a project get value managed away into the ether.
Design elements are removed that would inherently improve the quality of the building, ensuring indoor environments that would maximise the health and well-being of future building occupants.
Unfortunately, it looks like we’re pretty far away from the NCC raising the quality of buildings, and until then the driver for better construction seems to be coming from the grassroots level – a bottom-up approach in which the industry itself is shouting that it wants more.
Widely accepted as the most effective energy efficiency standard of buildings, and certainly the fastest growing, Passivhaus (PH) is currently pulling more and more traction in Australia as it becomes clear that the current quality of building is seriously missing the mark. More and more architects and specialist PH consultants are popping up all over the country, spreading the word and driving change.
As of yet, there are no certified non-residential buildings in the country, but it seems that soon that is likely to change.
Multi-unit residential developments lend themselves well to a Passivhaus approach due to their inherent beneficial external envelope to floor ratio, and often work out to be financially more tempting than single-occupancy dwellings.
With this is mind, before the start of any Passivhaus project, there are a few aspects that should be considered at an early stage:
Pursuing a Passivhaus certification will require a longer time commitment in both the design and construction process. As the standard is well above the current state of play in the Australian construction industry, the additional time allocated for more in-depth collaboration between consultants, more thorough documentation, potentially more labour intensive construction techniques, additional testing and site monitoring, and longer lead-in times from overseas products (if the design requires it) needs to be accounted for.
Position of the thermal line
The location of any unconditioned zones needs to be carefully considered and developed; car parks (particularly if in the basement) need to be correctly detailed, but the location of stairwells and lift shafts can also determine the required thermal performance of the associated external envelope, and also impact the calculation of the treated floor area that is entered into the PH software.
Airtightness and thermal bridging
These are the two elements of Passivhaus that are currently so far removed from our existing building code, they are pretty much an alien language. There is a lack of knowledge within the construction industry, both from a design perspective and especially from a construction perspective. Where you have two different sub-contractors, the difficulties manifest unless you have an incredibly collaborative approach, highly detailed design documentation and thorough site monitoring.
A key decision for these developments will be whether to have decentralised or centralised building services. Bearing in mind that a multi-residential development designed to the Passivhaus standard will require additional mechanical ventilation above and beyond the traditional extract-only design to ensure excellent air quality even when windows are shut. There are benefits to each of the distribution methods; the design choice will depend on the specifics of the development, maintenance preferences, spacial allowance for services, proposed tenants, management of the building and cost limitations.
Hot water generation
The primary energy target stipulated in the PH certification includes the usage of hot water, which is often the largest end use of energy in PH multi-residential developments. The maximum output from solar collectors will be determined by available roof space; depending on the number of apartments within the development, the design may need to incorporate additional heat recovery mechanisms to ensure the primary energy target is not exceeded.
In order to get the official stamp of the PH certified building, the design and construction needs to be assessed and reviewed by a third party certifier accredited by the PHI. Currently, no one exists in this capacity in Australia. In fact, all of them are currently located in the northern hemisphere. Technology these days can certainly make that distance feel a lot closer, but that doesn’t mean the time difference won’t often be a drag and cause delays, with communication turnaround being quite slow.
Momentum is definitely building for the Passivhaus standard in Australia. Sure, there are some big gaps in the knowledge of the industry here, but that shouldn’t be seen as a deterrent to progress. The opportunity to become a leader in the field and show others how it could be done is an opportunity that shouldn’t (and hopefully won’t) be wasted.