Green point

Written by
Dr Ayub Macharia

Green point2
NEMA recently launched a Green point at Isiolo City in Kenya. As can be seen in the photo above, this is a building with special features and and is regarded as a green building. In this article, I will explain what a green building is and what is regarded as a green point by NEMA.
A green point integrates both a green building and other initiatives that promote green economy within the compound. NEMA conceptualizes a green point as an educational centre where public and schools are taught about green buildings and also a site where stakeholders promoting green technologies, products and practices could meet to exhibit and explain the same to members of the public. Hence visitors at the green point will be met by diverse stakeholders who promote different green initiatives as well as learn how to construct and operate green buildings.
Gum arabicaKEMU
Let me explain about the uniqueness of the green building. It is important to note that the Isiolo Green Point exhibits all the features mentioned below and hence is an ideal place to learn how green buildings contribute to reducing carbon emissions and hence mitigating the negative effects of climate change.
green concept
A building is considered green when it fulfill the following criteria:-
1. Optimizes the structure’s energy efficiency
2. Minimises energy demand
3. Maximizes efficiency of energy supply
4. Maximizes a share of renewable energy sources
To fulfill this criteria, green buildings have the following features
1. Lighting
The orientation of the building is done in such a way as to take cognisant of the movement of the sun during the day and throughout the year. Hence efforts are made to consider effects of neighboring buildings in terms of shading and sunscreen effects. In Kenya, the recommended orientation is East-West axis to minimize direct exposure to solar radiation.
Natural lighting is preferred and should be maximized. This could be optimized by installation of high reaching windows and openings on the roof  to provide best distribution of light.
2. Aeration
Use of natural aeration is emphasized. Hence understanding of wind speed and direction is essential. The building should allow for free flow of wind. There should be large openings (doors and windows) which should be shaded to reduce solar radiation.
3. Topography
Its good to consider natural features around the building which contribute to existing microclimate. Features such as rivers, streams, valleys, hills, mountains which may assist or obstruct free flow of wind, natural cooling and sun shading.
4. Vegetation
Vegetation such as trees regulate temperatures, trap dust, act as wind breakers and provide oxygen through photosynthesis.
5. Distance between buildings
This is an important consideration to ensure that there is no hampering of natural light. Appropriate distance should also assist to ensure that the wind flows freely between the buildings and hence natural ventilation.
6. Building footprint
The area occupied by the building should not exceed 50% of the total plot area. The remaining area should be left permeable to ensure rainwater infiltration.
7. Cooking
There should be provision for energy efficient stoves in the building design.
8. Roof
A sloped roof is preferred to avoid storm water retention and infiltration. Sometimes, plants are planted on the roof to decrease temperatures, purify air and as sound proofing.
9. Building materials
The climate zone is the key determinant of the materials used in construction. In warm dry regions, with temperature range of 14oC stones are preferred as they store heat during the day and emit it during the cooler night. In other places, wood is used as it does not store heat.
It is advisable to use local materials to support the local economy and to avoid pollution.
10. Colours
Light colors befit the indoors to reflect day light. Light colors outdoors and on the roof reflect more sunlight and absorb less heat.
11. Energy supply
a. Solar
Lighting – Use solar panels installed on the roof.
Water heating – Use solar water heaters comprising of a collector, and insulated storage tank.
b. Wind
Wind turbines could be installed to generate electricity for lighting or pumping water. Wind power depends on constancy, speed, direction and turbulence.
c. Biogas
Anaerobic digesters could be installed to produce energy in form of heat and electricity. Biogas could drive a small scale power generator and could also be used directly for cooking.
d. Biomass
There should be provision for improved cookstoves that uses less charcoal and firewood. Use of biogas should be encouraged.
12. Water
Some of the waste water could be recycled and used for flushing toilets and garden watering. Waste water from kitchen sinks, and toilets are heavily contaminated and require treatment. Green buildings normally have waste water treatment system if they are located far from the sewer system.
13. Rainwater harvesting
Green buildings have provision for collection of rain water from the roof using gutters and directing it into storage tanks where it could be used for gardening and flushing toilets. If this water is properly treated, it could be used for drinking and cooking purposes.
14. Surface runoff
When there is too much rain, some of the water does not infiltrate but runs over the surface as runoff. This water could cause soil erosion and flooding. Green building minimize impervious surfaces and provide storm drains to improve drainage.
15. Solid waste
Green buildings promote household garbage sorting as the first step in sustainable solid waste management. There is also provision for onsite sorted waste disposal and communal garbage collection. Sorting helps to recover wastes such as glass, paper, plastic and metals which are reused or recycled. Organic waste can be used for making compost manure or to generate biogas.
UNEP (2006) Eco-housing guidelines for tropical regions. Bangkok, Thailand
UN-HABITAT (undated) Urban energy technical note No. 01

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