Thermal insulation, Energy saving and Carbon Emission Reduction
Thermal insulation mechanism
- Bottles with water inside and space created between bottles give better heat insulation.
- Shade created by plants which reflect sunlight and absorb solar radiation. The higher Leaf Area Index (LAI) the better.
- Evapotranspiration effect (evaporation+plant transpiration). Heat disperses with evaporation.
- Soil layer (including pores). It provides functions of heat insulation and dispersion (with evaporation).
- Non-woven fabric (but with limited efficacy due to its thinness).
Energy Saving Mechanism
- Thermal insulation → lower indoor temperature → less need for air-conditioning → energy saving
- Keeping indoor warm in winter (unfortunately, this is a major drawback in Taiwan and other places with similar weather, to be explained.)→ less need for heater → energy saving
- Urban heat island mitigation → lower urban temperature → less need for air-conditioning → energy saving
Carbon Emission Reduction Mechanism
- Energy saving → less need for power supplied by fire-power plant → carbon emission reduction
- Photosynthesis → carbon to be sequestrated inside plants or soil → carbon emission reduction
Zero food mileage
After being produced, the food has to go through a long and multi-stops delivery channel before it reaches the urban residents. In this channel, packaging and transportation consume resources and energy and cause significant carbon emission. The best way to avoid such things is to produce food at own home, e.g., zero food mileage. It is not only the most environmental friendly way for producing food but also ensures food safety.
Diminishing Urban Heat Island Effect
Causes of Urban Heat Island Effect
- High density of building and paved roads. Due to their smaller Specific Heat Capacity, surface temperature of them increase rapidly after absorbing heat.
- Urban canyon effect. It increases radiation reflection and causes more building heat absorption.
- Less green coverage. Evapotranspiration (evaporation and plant transpiration) converts sensible heat to latent heat and release it, which helps cool down the environment. Less green coverage means less heat absorption and thus environment temperature increases.
- Slower airflow in city. Due to building blockage, air flows in city more slowly, which restraints waste heat and pollutants.
- Man-made waste heat emitted by automobiles, air conditioning, etc.
- Particulate matter. It changes the radiative property of atmosphere (reflect shortwave and block longwave).
According to the study of Li et al. (2014) on the effect of green roof application in USA Baltimore-Washington, the surface urban temperature is estimated to drop 1oC if green roof coverage reaches 30% of the city; and 2-meter-high urban temperature is expected to drop 0.5oC when coverage reaches 90%.
Rainfall retention reduces runoff, postpones peak runoff, and thus relieves drainage system loading.
- PET bottles store rainfall. Every 16 small bottles can store water about 9.6 litters. Bigger bottles store more.
- Plants and leaves absorb rainwater too.
- Soil and media (moisture content) can also retain rainwater.
No water pollution
- Conventional green roof will discharge polluted water due to irrigation. However, for our kits, water is stored inside bottles and does not overflow except during storm events, and therefore almost no water pollution problem.
- Water flows into bottles without exposure to outside environment, and thus leaves no chance for mosquito inhabitants.
Air Pollution Abatement
According to Nowak (1994) and Rowe (2011), plants abates the following pollutants:
- Particulate matter (PM)
- Nitrogen Dioxide (NO2)
- Sulfur Dioxide (SO2)
- Ozone (O3)
- Hydrocabon (HC)
- Carbon dioxide (CO2)
- Take up gaseous pollutants through their stomata;
- Intercept PM with leaves;
- Breaking down certain organic compounds such as poly-aromatic hydrocarbons in plant tissues or in the soil;
- Lowering temperature →indirectly decreases photochemical reactions that form pollutants such as ozone;
- Excellent for noise attenuation, especially for low frequency noise.
- Extensive green roof can lower noise by 40 decibels (see https://greenroofs.org/about-green-roofs/).
Creation of Habitat
Providing habitats for flora and fauna.