Case Studies

Ethos Homes choose wool insulation for Passive House homes 

by Brad Stuart | May 9, 2024

Rata homes at Bushland Park passive house subdivision

Peter Bielski, owner of Ethos Homes, is passionate about wool. ‘Wool is such an integral part of our builds,’ he says, ‘it helps keep indoor temperatures stable and comfortable all year round.’   

Peter and his team specialise in building Certified Passive House and high-performance homes. Their latest projects are the two Rātā House designs at 8 & 10 Bushland Place, Bushland Park, designed by Meta Architects. Passionate about wool, Peter has used Terra Lana insulation throughout these new builds.

‘As well as selecting high-performing products, installer safety impacts our product choices. Terra Lana insulation is easy to work with, with no nasties, allergens or fibres that are harmful to my team,’ Peter says. ‘Add to that genuine sustainability, with a local supply chain, and you’ve got the perfect product to achieve our goals.’ 

Terra Lana wool insulation offers an ethical choice for builders and specifiers like Ethos Homes. Not only does it support local farmers and build New Zealand’s innovation in wool products, it also offers excellent carbon footprint and product stewardship credentials. 

Wool is hygroscopic, unlike synthetic fibres

Terra Lana insulation within Passive House homes can not only meet the high thermal requirements but offers inherent unique performance properties. Wool is hygroscopic, which means it absorbs and releases moisture, without compromising thermal performance. We know this to be true in nature on the back of a sheep, and when we wear wool textiles on our skin. In a building, this helps reduce the risk of moisture accumulating in the structure. 

Terra Lana insulation uses thermal bonding technology, which ensures no slumping or degradation over the lifetime of the building. The benefit for the homeowner is a healthier, more comfortable living environment that requires less energy to heat and cool than required with synthetic insulation.

A renewable resource for sustainability

For Peter, wool’s sustainability and the economic benefits of being one of New Zealand’s greatest renewable resources are just as important as its performance. 

‘In our homes, it’s all wool carpeting and wool insulation,’ he says. ‘We’re supporting innovative local companies like Terra Lana that offer a local supply chain and product circularity. We need to create a circular economy for the products we use, and wool is ideal for that based on a major primary industry.’ 

Terra Lana’s new wool is sourced from local Canterbury farms, and their recycled wool is from carpet manufacturers’ pre-consumer waste. All Terra Lana offcuts can be returned and recycled in their low-carbon manufacturing plant.

Rigid insulation that won’t sag

Ethos Homes has now built nine certified Passive House homes, making them one of the most specialised in the country. In Ethos Homes’ workshop, Peter has developed a whole system approach and his preferred envelope build-ups for constructing both Passive Houses and high-performance homes. 

‘Terra Lana has come up with innovative new products to fit 900-centre trusses or rafters that are rigid and don’t sag. With the new H1 requirements, if you put that much insulation weight in a ceiling it sags so much between the trusses, and their product doesn’t because it’s more rigid.’  

‘Passive House is not just a standard to meet, it’s a process,’ says Peter. ‘We have completed the energy modelling, minimised thermal bridges, designed the airtight building envelope, planned the pathway of the ventilation ducts, selected high-performance windows and doors and we cocoon homes in a continuous layer of wool insulation.’ 

With the entire Bushland Park subdivision targeting Passive House Plus certification, Peter is adamant that Ethos Homes will use only one type of insulation going forward. ‘We use wool because it’s the right product to use.’ 

Passive House requirements and calculations

To achieve Passive House requirements completed buildings must not exceed 0.6 air changes per hour (ACH). Using Terra Lana wool insulation in the walls and ceilings of the Rātā homes, Ethos Homes achieved 0.18 ACH at 8 Bushland Place and .26 ACH at number 10, well under the standard. See the full calculations on Sustainable Engineering’s website.