Rethinking construction to create high-quality, carbon-zero homes. By Michael Smith
As a response to the increasingly prohibitive costs and shortages of high- quality, healthy housing in New Zealand – and the length of build times and urgent need for sustainable construction – leading architectural practice RTA Studio has designed the Living House.
Timber Trader News took the opportunity to ask studio founder Richard Naish about the three-bedroom, 85 sq m house, which combines home-grown architectural IP with advanced timber technology to transform traditional construction into a streamlined assembly process.
Naish says the innovative system is about “rethinking construction to create high- quality, carbon-zero homes that are faster, simpler and more sustainable to build”.
The Living House combines intellectual property developed by RTA Studio with the mass timber fabrication expertise of Rotorua’s Red Stag TimberLab. Construction is from natural, low- maintenance, low-carbon-footprint building materials resulting in a healthy indoor environment. Thermally efficient materials and technologies provide warmth in winter and cooling in summer, and the design optimises natural light and ventilation, indoor air quality and comfort.
Last year, Naish presented the concept in Singapore at the World Architecture Festival after it was shortlisted in the future housing category. And this year, demonstrating RTA Studio’s commitment through direct investment, Living House purchased a subdivided section in suburban Rotorua to build the first Living House. “Around the world, there are many examples of architect-designed housing systems that never get past the conceptual stage because of the investment required. We’re architects, not developers, but we’re personally invested in the Living House because we have exactly the skill set required to design better, faster and healthier affordable housing.”
COST REDUCTIONS
The Living House system is designed for quick assembly – taking as little as five to six weeks once the foundations are ready. While the average cost of a New Zealand Government funded house is $586,000 to build (excluding land costs), the Living House estimate is just $333,000, excluding the cost of land but including GST.
That cost includes a functionally designed kitchen with a green energy and appliance package put together by Fisher & Paykel Home Solutions (which features a Haier cooktop, oven, rangehood and dishwasher, as well as solar panels, inverter, solar hot water and heat pump). Flooring, lighting and carpets are also included in the cost.
Naish explains that the off-site manufacture and speed of construction resulted in greatly reduced labour costs, “which we estimate to be a reduction from 50% to 20%. The Living House features exposed CLT throughout the interiors, which reduced the labour component around stopping and painting trades, compared to a typical two-stage services installation.
“The CLT panels provide useful thermal mass and are wrapped with PIR insulation. This methodology allows a continuous thermal envelope to be achieved for the roof, walls and suspended floor, thereby outperforming a typical timber-frame building.”
Further, he notes that the Living House panels have been intentionally designed with simple lap-joint and only screwed connections. “Structural engineers Dunning Thornton designed out the need for complex bracketry and worked with RTA Studio to provide a straightforward panel sequence that enables the builder to use a HIAB truck to position each panel. This simplicity allowed the prototype house to be quickly constructed by a local licensed building practitioner with no prior experience of CLT.”
PROOF OF CONCEPT
Naish acknowledges that CLT panel cost is greater than an equivalent size area of timber framing, but there is a misconception that building with CLT is prohibitively expensive. “The Living House prototype is proof of concept that it can be an affordable option when the design is centred on CLT from the outset.
“Different suppliers of CLT have differing design and performance characteristics for their products, so the mass timber procurement avenue needs to be understood and managed correctly early in the process to give a clearer understanding of costs.”
He adds that the Living House can be built anywhere in New Zealand, so it has to cope with the worst-case environmental constraints, including wind, corrosion and climate. “From the foundations up, the structure has been designed for the majority of seismic conditions, including zones 1, 2 and 3, in New Zealand – but specific engineering would be required for seismic zone 4.
“The prototype Living House in Rotorua is built on timber-driven piles, but a site-specific approach is required for each foundation design to ensure it is appropriate for the environmental constraints of the site. As a standalone residential house, there were no specific fire or acoustic requirements.”
Above: The interior features exposed CLT, which reduced the labour component around stopping and painting trades.
WEATHERTIGHT ENVELOPE
It’s interesting to note that some multi-storey engineered wood projects have encountered on-site issues in protecting timber from the weather in the initial stages of construction. However, the short timeframe with the Living House prototype – from CLT installation through to a weathertight envelope – greatly reduced the risk of timber being exposed to wet weather.
“The modest size allowed the builder to use a simple tarpaulin to cover the house when required to protect it from the weather – and timber moisture content was monitored throughout construction. In other projects with longer construction timeframes, RTA Studio has had success using factory-applied protective coatings to mitigate the effects of weather.”
ONE-TRUCK DELIVERY
Naish says the CLT panels were specifically designed for a one-truck delivery with no pilot vehicle required – no matter where the modules are delivered. “Our research showed that pilot vehicle costs increased exponentially as factory-to-site delivery distance increased, so we designed that need out of the delivery process.
“The system eliminates most on-site building waste, and is verified as embodied carbon net zero, ensuring minimal impact from construction to operation.
“Currently, supply of CLT in New Zealand is from Red Stag Timber in Rotorua, but the panels could be produced by any CLT factory. Freight costs for CLT from Rotorua in the North Island to the bottom of the South Island add around $10,500, including GST, to the total cost of a Living House.”
He is encouraged by the positive feedback to the project received so far. “We have had representatives from both the Labour and National parties through the house since the prototype was completed.”
Member of Parliament for Rotorua and Minister of Forestry Todd McClay praised the project and said, “the Government had signalled a willingness to work with community groups and the private sector in Rotorua to build homes at a reasonable cost. He added, ‘I congratulate all those involved for their hard work and will make sure senior ministers are aware of this accomplishment’.”
Labour’s Kieran McAnulty [the party’s spokesperson for housing] said the country should be better utilising these more innovative solutions to address our housing challenges.
“Community housing providers and iwi groups who have been through the house have also praised the simple design and found it spatially satisfying, acknowledging the efficiency and low-maintenance robustness.”
FUTURE ITERATIONS
Naish says the design team are currently working on one- and two-bedroom versions, and the plan, eventually, is to add a two- storey terrace house to the portfolio. “We are working on some schemes for iwi and other developments incorporating the Living House in a co-housing scenario. We will also work on other options for housing, using the Living House CLT concept, as required.
“The Living House isn’t a silver bullet for the New Zealand housing crisis,” says Naish. “The cost of land is a major issue, and a three-bedroom home isn’t fit for all scenarios. I think the most in-demand social housing typology is actually a single-unit dwelling.
“For us, however, hearing daily news stories about kids living in cars and motels was a strong motivation to design a family home.”
Note: the house will be sold at cost to a family who would otherwise find home ownership unattainable, in a collaboration with Rotorua Lakes Council, iwi and other parties.
