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Tag: rammed earth

  • 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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  • HPH141 : What is a structural engineer? – with Andrew Collinson

    HPH141 : What is a structural engineer? – with Andrew Collinson

    Andrew Collinson explains the role of a structural engineer.

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    Interview with Andrew Collinson

    Andrew Collinson is a structural engineer based in Herefordshire. His degree course in the subject was mostly based on theory, so his real training came from learning on the job for a big contractor. From working on site he moved to the design office and this background gave him a good understanding of the practicality of a design.

    “The basic job of a structural engineer is to make things stand up”

    The engineer’s involvement will usually begin with receiving architects drawings, and their job is to make sure the foundations are suitable, and any beams, floor timbers, roof timbers etc are the correct size.

    Quite often they will be appointed through the architect who already has the building design but just needs engineering help in certain areas, like the foundation details or beam sizes. In these cases Andrew will be dealing with the architect directly and may not need to meet the client.

    Most people don’t go to the expense of having a site investigation

    For most jobs the ground conditions aren’t fully known before work commences. The structural engineer will have to make a best guess that will cover most circumstances, by writing down the assumptions that the ground is likely to be something suitable and that particular foundations will work with that. If, once the contractor starts digging, they find anything outside those parameters then they will come back to the engineer for a revision. Andrew says that in most cases standard foundation solutions will work, but there will always be a few that don’t, based on whatever surprises are found once digging starts.

    “Until you dig in the ground you don’t know what’s under there so you either pay up front to get someone to come and have a look at it, or you take the risk when you dig that there might be a slight delay.”

    And it’s important to remember, that everything can be resolved – it just may come with a heavier price attached!

    Most cases are covered by Part A of the Building Regulations

    Part A of the Building Regulations has a series of descriptions, and depending on the loading of the wall coming onto the foundation, it stipulates the minimum foundation width and how deep they need to be. Andrew says that most people could read off these tables if they knew what the loading coming down the wall was. There are variations for example if there are trees nearby or it is clay soil. Doing something smaller than is covered by Part A of the Building Regulations might need more careful engineering, and for that you would need to know soil conditions.

    Natural materials are less well covered by the Building Regulations

    Masonry builds are very well covered by the Building Regs. Timber frame for example is less well covered by the documents but often that is designed by the supplier who will have their own engineers.

    It is more challenging to convince building control officers that materials like rammed earth, cob and straw bale have been designed right and won’t fall down, because they are not so well defined structurally and it is difficult to put a figure on their strength.

    Andrew recommends that if you’re wanting to use one of the less common building materials it’s good to get an engineer on board early so they have time to research, and ensure there aren’t any difficulties that are likely to arise.

    Steel or timber frame?

    Steel is very stiff and an efficient material from an engineering point of view. Steel beams can be made to be near identical, and if you have limited head room it can be hidden effectively. It is readily available, fairly inexpensive and builders know what to do with it. With steel though you would normally need to get someone else to cut it for you and it has to be right first time.

    One advantage of timber is that it can be cut on-site to get the exact size required. Every timber beam will be different so can have more of an aesthetic quality. And being a natural material it tends to have more movement, particularly from drying and shrinkage with green oak. Timber also benefits from less embodied energy than steel.

    As a client, it’s important to manage changes in the right way

    Andrew uses the example of a current self build project he’s working on, where the scheme is virtually complete but the client is very hands-on, has done a lot of research and is open to making changes. Andrew says that it is refreshing to work with a client like that who is able to understand the more technical details and can have more informed decisions about whether to make changes to improve the scheme. He does add however that there’s a fine line between that and an interfering client who keeps changing things!

    “Because when you’re trying to move things along quickly, change needs to be managed as a process. Nothing wracks up bills more quickly than constant changes by the client because it can often involve going right back to square one and re-doing a whole load of stuff, which isn’t readily apparent to someone who doesn’t understand.

    “So it is important to manage changes in the right way as a client. Which doesn’t mean to say that you can’t change things but you need to understand there may well be consequences.”

    Use personal recommendation to find a good structural engineer

    Recommendation is the best way to find a good structural engineer. Ask a previous client about whether they produced things to a reasonable time scale, were the costs reasonable, and even just getting a gut feeling about them from speaking on the phone.

    “Do they feel a bit stand-offish, are they someone you could have a discussion with? Are they the sort of person that you would want working for you or not? Because sometimes if people don’t speak to you nicely on the phone the first time, how are they going to talk to you later on?”

    Transcript

    Download a transcript of the interview with Andrew Collinson.

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