IDEAL House – New Zealand

Project Goals: Certified Passive House, Positive Energy & 8/10 Homestar design. Proudly supported by IDEAL Electrical Suppliers.

Green Roof & Update

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It’s been a busy couple of weeks locking down some of the design aspects of the home and finalising budgets.

When conceptualising the deck on top of the garage, Matt Wilson from S3 Architects suggested a green roof. To be honest, apart from seeing them in various Council presentations (and a few rumours of DIY projects going literally sour, with trapped water turning septic), this was an area of green building with which we weren’t terribly familiar. After some interesting meetings and quite a bit of research, we’ve determined that there, unsurprisingly,  isn’t one “right” way to build a green roof! Ranging from DIY to pre-grown systems that are planted in advance, there are so many options to consider.

Because the roof of the garage is flat, we need to waterproof it anyway, so using a membrane and then placing a drainage system and lightweight growing medium over the top sounds logical, and also appeals to our aesthetic sensibility. A rooftop oasis certainly sounds lovely! Additionally, a green roof would contribue to our overall score within the HomeStar rating.  However, before we start mentally planting, we’ll need to do some careful budgeting and engineering to see how a green roof may impact our current structure. One of the estimates we’ve been given is 200kg/square metre for a fully saturated system, so that means the 38m2 garage would need to support up to 7.6 tonnes of weight. At least we’ve got a solid timber substrate to work with, which will be far less complicated than traditional joists, bearers, and plywood – we just need to ensure we get the correct specification.

We’re also delighted to have a range of suppliers join our project over the past couple of weeks, from door hardware from ASSA ABLOY, through to specifically environmentally conscious products like Envirocrete from CEMIX. We’ll be needing to work closely with ASSA ABLOY with regards to their Henderson door tracks when it comes to designing cost effective sliding louvres for the western side of the house. The evening western sun can be harsh in summer, and we don’t want the house heating up like a greenhouse.

Other suppliers that have joined us:

  • Hume Doors will be supplying the over-height 2200mm internal doors, and some of the cavity sliders.
  • pro clima have recently had their external wall wrap, Solitex Extasana, CodeMark certified. After being in the industry for years, there are a wide range of wall wraps available, each with their own pro’s and con’s. I have been impressed with the immense water-tightness of the Solitex Extasana, and having the CodeMark certification (the Department and Building and Housing’s own certification system) gives us complete assurance that it will fly through the consent stage at Council.

We’re also pleased to have been featured on the Envivo website. (click here) The completion of the survey meant S3 determined that the house was infringing on height restrictions on the eastern side. This has meant trimming the overall structure by about 200mm, and also shifting it west (up the slight slope) another metre.

Last but not least, iDEAL Electrical have been working furiously behind the scenes on assessing the best energy efficient electrical products and systems for the build. Philips have pledged their assistance with design and materials, and we’re very keen to demonstrate innovative LED lighting products. We will be posting specific articles on what products we end up choosing, and why, and what benefits they will have over other products on the market.

We’re a week out from Christmas, and the building industry is winding down for the holidays. Even though we want things done NOW, the project will mostly go on hold for a few weeks until mid-January. We’ll be back then with more updates! Merry Christmas and Happy New Year!

Some pictures provided from from Viking on their roof membrane system during our research, just used in the Taranaki. How good is this going to look when completed!

New Ply Roof Garden install April 2012 (25) (2)

New Ply Roof Garden install April 2012 (35) (2)

New Ply Roof Garden install April 2012 (37) (2)

New Ply Roof Garden install April 2012 (44) (2)

One thought on “Green Roof & Update

  1. Hi Murray, good to see some progress with this website, and good luck with the project!
    Frankly, I would not bother with the green roof. You are not in a densely build up area, so I do not see much benefit (apart from perhaps retaining stormwater run-off – but there are cheaper and safer solutions for that), and the golden rule of building construction is still: to drain water away from all surfaces as fast as possible. Green roofs can work – I have some positive experience with them – but why take the risk and cost when, in your case, the benefits are slim?
    My advice would be to concentrate on reducing the energy demand to the utmost possible, and – in case there are still funds left when this is perfected – invest in renewables. Reducing the energy demand has a multitude of fringe benefits – most other areas of so called building sustainability are riddled with conflicting goals, and simple rating tools like HomeStar are little help in cutting through the chase.

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