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  • HPH239 : 3 great eco developments in New Zealand – with Matthew Cutler-Welsh

    HPH239 : 3 great eco developments in New Zealand – with Matthew Cutler-Welsh

    Matthew Cutler-Welsh takes us through three exciting projects that are making an impact in New Zealand.

    Interview with Matthew Cutler-Welsh

    Matthew Cutler-Welsh of Home Style Green was one of our early guests on the podcast, talking about some of the challenges of creating sustainable urban systems.

    Since we last spoke with him, he has trained in building surveying. It has taught him more about building science and he sees it as a positive step that expertise in building science is generally becoming more recognised and utilised in architecture and construction in New Zealand.

    “Because what I’ve realised is that buildings are complex systems and they’re a system of systems, and the more we make them controlled environments on the inside then the more we have to understand how the various aspects of physics, basically, interrelate to each other.”

    This interest has also led Matthew to his new role working with Pro Clima, where he primarily works to educate and support both the design industry and building industry in their understanding of some of the fundamentals of building science.

    Matthew is also on the board of the Passive House Institute New Zealand.

    The Living House

    Matthew’s first choice to discuss is owned by friends of his – Rochelle and Joel. This one is unique in that as well as physically building the house themselves using rammed earth, they are also targeting the triple prize of achieving the Passivhaus standard, Living Building Challenge and Homestar (equivalent to the old Code for Sustainable Homes or LEED).

    Rochelle is an engineer by trade and is very detail focused, hunting down products and details and finding out everything there is to know about them.

    Matthew explains that as well as being an amazing home, it will be an incredible resource for the whole industry, leading the way for others to follow.

    He says the house, by pushing boundaries, is already making waves and challenging the Council. Meeting standards is generally the path of least resistance to getting permission, but for anyone trying to build a house that actually performs better they may find themselves with an uphill struggle.

    “So, if you’re doing something that falls outside of that because you want to have a house that actually performs really, really well, then you have to put in quite a lot of effort to prove to the Council that the products, systems and how everything fits together is not going to cause them any problems down the track.”

    Because they’re doing a Living Building Challenge, they are able to argue a case for not having to pay fees for Council utilities that they won’t be using. They’re finding that this is rattling a few cages!

    The design

    Rochelle and Joel are building a contemporary style of home using rammed earth. The earth is sustainable as it is sourced fairly locally, and also allows them to do much of the building themselves. While it might not have universal appeal in terms of aesthetic and time it takes to build with, it is certainly a unique product.

    Living Building Challenge

    Matthew explains the Living Building Challenge as going beyond sustainability. He says that ‘sustainable’ is just a case of not doing harm, whereas the philosophy behind the Living Building Challenge is thinking about how the environment can actually be improved by the building being there.

    “So, the building becomes an asset to the ecology and the environment around it. Rather than just taking it as how do I make this building and do less bad to the environment, how can I actually use this building as an integral part of the ecosystem.”

    One aspect is in the treatment of water, where the building systems (natural filtration systems, rain gardens etc) clean the water so that any run-off from the site is actually cleaner than the water that comes onto the site in the first place.

    Living Building Challenge also provide guidance on the use of products and materials, which can be a particular challenge in a small island nation, where you’re encouraged to use as many local materials as possible. They also don’t allow the use of some materials like certain foams and polystyrenes because of the chemical toxicity in the manufacturing process.

    Waikato House

    Matthew’s next choice is a house built in the Waikato region, south of Auckland. It was built by a builder who now works for eHaus, a national brand of Passivhaus building in New Zealand.

    Matthew explains that it stands out as being built by someone who clearly has been re-inspired and discovered a new passion.

    He describes it as a contemporary home in green pastures and farmland, that has a beautiful design and doesn’t look like a Passivhaus.

    “But it was really that passion from the builder, the pride and the beauty of the simplicity of this house that really struck me.”

    This house has been built as a show home for the construction company, and Matthew comments on how something they are seeing more of, is builders offering a “try before you buy” approach to selling houses. So instead of visiting a show home for half an hour you’re able to try it out for a night and experience first-hand how well it performs.

    Dunedin co-housing

    This co-housing group formed in 2013, and they are looking to build 20-25 houses on a 5000 square metre site, which was formerly a high school.

    The group have overcome challenges, particularly financial ones, and now have plans for two rows of terraced housing.

    Images from Architype NZ

    Matthew is drawn to this project, partly because of its Passivhaus credentials and sense of community, but also because it is addressing the affordability issue.

    “Co-housing projects like this really open up the opportunities for creating community and creating housing that works for people.”

    He sees it as an exciting project that could pave the way for future similar schemes around the country.

    Matthew highlights that there is a global community of people involved in co-housing, who have done projects successfully and are keen to help on other projects.

    And although this, and many other co-housing projects, can take a while to get off the ground, it’s actually as much about the process as the finished house.

    Find out more

    Check out Matthew’s Home Style Green podcast

    Follow Matthew on Twitter

    Find out more about the projects in this episode:

    The Living House

    Waikato House

    Dunedin co-housing

    Transcript

    Download a transcript of the interview with Matthew Cutler-Welsh

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  • HPH227 : What’s the best way to build an airtight structure? – with Paul Jennings

    HPH227 : What’s the best way to build an airtight structure? – with Paul Jennings

    Air leakage expert Paul Jennings looks at how best to achieve that all important airtightness when using particular construction methods.

    Interview with Paul Jennings

    Paul Jennings is an air leakage expert with over 25 years experience. In our previous interview with him he explained how to achieve airtightness in low energy buildings. He also appeared in our documentary “The Future of Housing – and How Airtightness Can Help”, taking a look at housing construction quality and building performance to see how they could be improved.

    For this podcast, he looks at some of the issues with achieving airtightness in different construction types.

     

    Cross Laminated Timber (CLT)

    Paul recently tested a bungalow that was built using Cross Laminated Timber. The airtightness is essentially in the timber, and in this bungalow there were up to 8 laminations in each of the panels. The roof was a sandwich panel with layers of lamination, insulation, and more laminations on top. With the panels being larger than standard OSB boards, there is less taping involved. Each panel is also very strong, and strengthened further when screwed together. The taping goes where the panels butt up to each other, around windows, ventilation ducts, sun pipes etc. Once you have taped to the timber you have airtightness.

    Paul is starting to think that there is no need for a membrane on the outside. The CLT doesn’t meet insulation values but he thinks it’s perhaps easiest to insulate it externally and make it airtight on the inside.

     

    Structural Insulated Panel Systems (SIPS)

    Paul has experienced very good results with SIPS panels, which he feels have the potential to be very airtight. So far he hasn’t seen anyone using the airtight OSB as one of the faces of a SIPS panel system, which he thinks could improve it further.

    He explains there is a difference in results depending on whether foam is injected into the pre-made box, or whether a piece of foam is cut and put into a section of wood which then has sides added. The latter won’t be as airtight.

    SIPS panels can be a problem on site if they get saturated with water as they take such a long time to dry out, and the airtightness tapes do not adhere properly.

     

    Masonry Construction

    Masonry construction ticks the box of being a system that normal builders are used to building, where most materials can be sourced from a standard builders’ merchant. Paul offers Denby Dale Passivhaus as a great example of this.

    Paul explains that any construction with a cavity in, is a weakness for airtightness. If air can move laterally it can get around things and leak where you wouldn’t expect it to. He prefers a masonry build that has a masonry wall which is ideally wet plastered for airtightness on the inside, with insulation and render on the outside.

    “Because at that point, you have to have a continuous hole from the inside to the outside. You can’t have a hole through the inner leaf, then air moving in which way it likes in a cavity and then coming out somewhere else. It’s more robust for airtightness.”

    Paul points out that almost every masonry build has a timber frame roof, so as soon as you’ve opted for masonry construction you’ve doubled the number the number of build forms in your house anyway.

    Paul emphasises how the more complicated a build is, the harder it will be to achieve the airtightness. There is greater scope for people on site getting confused, doing the wrong thing or not checking details properly.

     

    Modular construction

    This isn’t a widely used construction method in the UK but there are increasing numbers of companies trying to develop it. The benefits of this method are that production has less of an issue with weather, shortage of trades people etc, than for on-site construction. The ones Paul has seen have been generally at a prototype stage with initial positive signs and great potential. He believes they will have to be built to be incredibly robust, as otherwise they wouldn’t survive being craned on to a lorry, driven to the site and craned off again.

    One of the big advantages of modular construction is there is less time spent on site, which means less financial impact from weather delays, and less overheads on things like site supervision, site cabins and toilets.

     

    Airtight OSB is gaining in popularity

    The trend that Paul is seeing at the moment is that membranes are losing out to the airtight Oriented Strand Board (OSB) and, for refurbishment particularly, to blowerproof paint. The most popular he currently sees in the market, and which he thinks are proving to be very successful, are the Durelis and the Propassiv.

    “At the same time, the refurbishment market is a bigger market than the new build market. We need to tackle refurbishment and we need to tackle it better. And we’re not. We’re learning lessons but really we’re taking our time over getting it and I don’t think we can afford that time.”

     

    Choose the right tape for the job

    Choose the right manufacturer, and the right tape. For example, don’t try and use 50mm tape to cover a gap of 60mm. Choose one that is wide enough for the gap.

    Paul believes the two best products for airtightness are produced by SIGA and Pro Clima. But no matter how good the tapes, most important of all is how well they’re applied.

     

    Plan early and get advice from the experts

    “You really want to get your designing done early, get your planning done early and then don’t mess with it. Because every time you change it, there will be unforeseen consequences. Usually those will be things that make your airtightness worse or harder at least.”

    Paul encourages self builders to take advantage of the Passivhaus Open Days and talking to the people who have built them. There are also the AECB and UK Passivhaus conferences that people can attend and find out more about the network of experts.

    “There are networks of people and a lot of them are very committed people. They give their time, they give their energy and they often don’t charge as much as they should for it, because they believe in it.”

     

    Find out more

    Visit the website of Design Buro

     

    Transcript

    Download the transcript of the interview with Paul Jennings.

     

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