A Green Roof I Experienced in Tokyo.
I was visiting an architect friend’s house in Tokyo, by the name of Eri Doi, who had designed her own house. Being a Realtor, I had already noticed how effectively she had designed the house in such a way as to maximize the feeling of space despite the lack of actually having it, a challenge which Tokyo is so famous for. But there was something to the place that had yet to reveal itself.
After having spent a while there, it came out that they had a lawn. Pretty amazing since such a thing is almost unheard of in Tokyo and most of Japan for that matter as the lots are taken up entirely or almost entirely by the houses that are built on them. The thing was, they had theirs on the roof. I just had to see it, so we climbed up and out the little door that leads to the roof to see their “yard”.
This private green space can of course be used for leisure, but it is also ecologically desirable as it has a positive impact on carbon emissions and general pollution. According to Eri, the evaporation of the water in the soil has a cooling effect on the house in the summer and it also provides some extra insulation.
The benefits of this relatively simple innovation are varied. Green roofs are used to:
- Provide amenity space for building users — in effect replacing a yard or patio
- Grow fruits, vegetables, and flowers
- Reduce heating (by adding mass and thermal resistance value) and cooling (by evaporative cooling) loads on a building — especially if it is glassed in so as to act as a terrarium and passive solar heat reservoir
- Reduce the urban heat island effect
- Increase roof life span
- Reduce stormwater run off — see water-wise gardening
- Filter pollutants and CO2 out of the air — see living wall
- Filter pollutants and heavy metals out of rainwater
- Increase wildlife habitat in built-up areas — see urban wilderness
And yes, that’s right there is one thing that may not appeal to everyone, it does need to be mowed periodically if you want to keep it looking good. This particular one has some pretty solid safety harnesses on the roof to keep you anchored to it while the yard work is done on that convex section of the roof. The mower was kind of interesting too, it was the size and shape of an upright vacuum, but on the bottom was a spinning disc shaped blade with straight little teeth on it. I assume that once the grass is cut by this blade, it is sucked up into a container like in a vacuum.
Oh, and by the way, Japanese grass doesn’t stay green all year. In fact it’s totally dry and brown in the winter, just in case you were wondering why it’s not totally green in the picture above.
Seeing this got me thinking about applying it to homes in Nanaimo. Right away I thought of us it as a way to improve ones view, as ocean views are such a hot item in Nanaimo. I’ve seen so many homes in Nanaimo where you have a great ocean view from upstairs and/or from the roof but not from the yard. I think it would be a great way to maximize one’s enjoyment of the view available to them or get one that wasn’t available before. I haven’t seen or heard of one in Nanaimo yet, and would like to hear from anyone who has or is planning to attempt these kinds of things.
Eri gave me the roof plans in PDF format for the roof and some photos of the construction process. I’ve put a translation of the steps below. Check them out.
Here is a translation of the steps described in the PDF with photos of the construction process of the curved section of the roof. They are numbered to match the photos:
1. Fibre Reinforced Plastic (FRP) waterproofing is the first layer to be put down. It is installed with some resilient and springy layers for enduring the effects of earthquakes.
2. Here is the completed FRP waterproofing. There are some protruding bars/ledges for preventing dirt from sliding.
3. Plastic loop fasteners are taped and glued to the FRP surface.
4. Those rings are covered with a net.
5. Sand bags are fastened around the sky lights, the roof’s edge and the protruding bars/ledges.
6. A 10cm layer of artificial lightweight soil is installed.
7. Sections of turf are placed aroundthe edge and fastened so they don’t move.
8. The rest of the turf is installed in an interlocking fashion.
9. The green roof is completed by watering the grass.
As for the flat part of the roof, we see more of the same kinds of steps.