Midori-chan is a patented and revolutionary ultra-lightweight greening system utilizing recycled waste and designed to maximise vegetation growth whilst dramatically minimising water usage and maintenance requirements. Midori-chan is truly sustainable technology; our engineers at the Kawada Group in Japan developed the system to meet the demands of greener and cleaner communities, consistent with Kawada's corporate mission of "building a better tomorrow".

It is based on a system in which rainwater is effectively cleaned, stored, recycled, and supplied to vegetation. The system mimics the natural water supply and evaporation that occurs on the earth's surface. Moisture transfer from the water storage units is generated by the thermal energy balance in the soil. A special regenerated charcoal layer cleanses the rainwater as it passes into the retaining trays and then grips that water as vapour, drawing it up to the plant roots.

Installing Midori-chan on building rooftops or roadside greening works offers multiple environmental and social advantages, primarily by using drastically less water than more conventional greening systems. By lessening the need to irrigate vegetation, the water usage drops dramatically. Urban temperatures will drop through the adoption of increased rooftop vegetation. We have verified that with the use of Midori-chan, the temperature on a bare concrete deck can be reduced by over 30°C. The thermal load on the environment will decrease since plants cool down the atmosphere and lower the heat gain into the roof slab. The greater the area of vegetation used, the greater the rate of photosynthesis that will take place, thus lowering harmful CO2 in the atmosphere.

As highlighted below within "System Characteristics for Different Plant Species", soil depths can be kept to a minimum depending on the type of plant species selected, thus concerns regarding loading constraints can be overcome whilst realising a truly "green" space.


System Outline

System Outline

Standard type (34L) Slim type (16L)

System Composition

System Composition

Comparison with Conventional System

Green Roofs Irrigation Comparison Table

Water consumption comparison

  • Conventional system - 190 litres / m² / month
  • Midori-chan - 0.17 litres / m² / month

System Characteristics for Differing Plant Species

  Grass Grass Groundcover Shrubs (small) Shrubs (large) Mid-sized trees
  Slim type Standard type 100 ∼ 500mm 600mm or less 900 ∼ 1,200mm 1,500 ∼ 2,500mm
Vegetation installation examples Slim type Standard type 100 ∼ 500mm 600mm or less 900 ∼ 1,200mm 1,500 ∼ 2,500mm
Plant spacing Complete coverage Complete coverage 200mm intervals 400mm intervals 600mm intervals 1,000mm intervals
Mulch mm - - 50 50 50 50
Soil thickness mm 50 50 100 150 200 250
Regenerated charcoal bags mm 30 30 30 30 30 30
Water storage unit mm 40 70 70 70 70 70
Total thickness mm 120 150 250 300 350 400
Saturated reference weights Without plants kg/m² 78 102 160 205 245 290
With plants kg/m² 86 117 168 215 301 350

Pre-construction to Post-construction

Pre-construction Within a minimal amount of time, a fully fledged rooftop garden can be achieved Post-construction

Service Flow

  • Effective utilisation of space and limited water resources stimulate opportunities for vegetation growth, improved aesthetics, healthier living, and reduced building / land maintenance costs.
  • Kawada's "Midori-chan" solutions promote responsible choices by capitalising upon evaporating water via the adoption of regenerated charcoal.
  • Creating environmentally friendly systems using recycled materials that exceed the construction industry's increasingly stringent environmental standards.
  • Pursuing opportunities overseas where Kawada technology can effectively be merged with other leading environmentally friendly products / technologies.
  • Effectively providing a "one-stop shop" for all green rooftop services, under Kawada's umbrella, commencing with waterproofing solutions to ongoing maintenance of the plants species.

Service Flow

Experience counts...

Over the duration of our trials in Hong Kong for the past 5 years, we have adjusted our plant palette, designs, soil depths, maintenance requirements, and hard landscaping components to match the arduous Hong Kong climatic environment. Through these trials we were able to determine the optimal soil design mix, planting spacing, mulch type, and soil depth whilst ensuring that the species are evergreen, low maintenance, aesthetically pleasing, and require virtually zero irrigation once established. As a consequence of this work, we have created a "plant palette" that comprises an assortment of over 60 species covering an array of colours, heights, and densities.

Midori-chan will not only dramatically cut greening lifecycle costs but also significantly cut the building cost of a new structure itself. As the system is ultra-lightweight and soil depths are minimal, this results in less structural steel, concrete and reinforcement in the construction process: a huge capital cost saving.

Outside of Asia, we are starting trials in Sydney, South Africa, and the West Coast of the U.S. We are examining projects in India, Singapore, the Philippines, and the Middle East. With Architects and Landscape Designers, we are exploring applications other than green roofs - ground-level applications such as median strips, roundabouts, planter boxes and green hoardings, where our technology can be put to good use.Using median strips as an example, the adoption of Midori-chan and its reduced maintenance needs means that watering vehicles are no longer required. This introduces one more cost saving - consumption of petrol/diesel and vehicle emissions are cut. In short, Midori-chan fights pollution while it just lays there, being green, being environmentally-friendly.

We all want the planet to be greener and are aware that "wanting" and "achieving" can be far apart. Midori-chan provides a solution. It is a truly "green" technology that is simple, economical, a "feel-good" sociology in itself, which we believe could help bring environmental benefits not only within Hong Kong, but across this entire planet of ours.