Building green in Israel
Lately, in Israel, we hear more and more often about so-called “green architecture.”
But what does this term mean exactly? Can it be applied to all types of buildings or is it something exotic and “organic”? Is it true that a house built according to the principles of green architecture is more expensive than a “normal” one? And are restorations possible using these principles?
I will answer all these questions (and more...) in a series of articles on green architecture.
Green, or better said, “bioclimatic” building refers to planning and building principles that allow us to construct a house which saves energies such as gas, electricity, and fuel and maximizes the use of renewable energy resources like the sun and the wind for heating and cooling purposes.
As a result, in such buildings maintenance costs are significantly reduced, and quality of life is high and healthy.
In the past, people knew how to manage extreme climate conditions without the help of electricity and fuel. So why can't we learn from them and do the same today?
The secret is to work in cooperation with local climate conditions and not against them!
There are three different “green” approaches:
PLANNING PRINCIPLES: these don't increase building costs, but they do reap great results. If we design the house with the right shape, locate it in the right place in the yard, size and position openings on the correct facades, we have already done the most important part of the work with no extra costs!!!
2. SOLUTIONS THAT REQUIRES AN INITIAL INVESTMENT, BUT REPAY THEMSELVES IN A FEW YEARS: like adding extra insulation in walls and roofs, photovoltaic systems on the roofs, separating gray water, double insulated windows, etc.
3. GREEN RETROFIT OF EXISTING HOUSES AND APARTMENTS: improves the energy performance of existing buildings. It usually requires, and investment and the result can be very impressive, but it will never be as good as a house built and planned from the beginning according to bio-climatic rules.
The Israeli climate has certain characteristics that make it ideal for green architecture:
big difference in temperatures between night and day (depending on areas)
high solar radiation in the winter on southern facades
northern and western winds in the summer evenings
If we work with the climate (and not against it!) and we take full advantage of these features, we will be able to build a “solar house” with minimum energy consumption and significant savings in the expenses.
The idea is to heat the house in the winter with passive solar heating, to keep the heat outside and to cool it with the help of winds in the summer. Well insulated walls with high thermal mass (materials such as stone, concrete, earth, ceramic in opposition to materials like wood and metal) help to achieve this result.
The incidence angle of the sun rays changes during the seasons: in the summer the sun is very high in the sky, but in the winter it is low.
Passive solar heating is possible through big windows facing south. The low winter sun passes through these openings, heats the house and is absorbed by the thermal mass. In the late afternoon when external temperatures are getting lower, the thermal storage mass begins to emit heat inside the house it gained during the day, and so it maintains healthy conditions.
All this is possible if the house is very well insulated on the external side of the walls.
In the summer, the solar radiation is relatively low and the sun incidence is very high on surfaces facing south. If we put shadings (overhang) on the windows or deciduous plants next to the southern facades (that protect the house in the summer but allows sun passage in the winter), the sun won't enter the house.
Nowadays we can precisely calculate overhang dimensions, thanks to very innovative and simple software (for example, Google Sketch-up has a function to calculate shadows). These shading systems can be made from several materials such as wood, aluminum, concrete or fabrics.
Also, the walls accumulate heat during the day and emit it with a delay of many hours, when outside temperatures are lower and fresh winds can refresh the house.
Controlling the amount of light and sun radiation entering from other facades is more difficult.
On east and west facades sun radiation is very high, and the incidence angle is low in the summer. For this reason, it is better to minimize openings on these sides and to put shutters to protect them from the sun.
On the other hand, northern windows don't help us for heating the house, so if we want direct sun in the room facing north, we can elevate the ceiling height and open some upper windows facing south.
These windows can also improve summer micro-climate in the rooms: hot air is lighter than cold one. Therefore it goes up and goes out through the upper window creating air movement in the chamber.
A green building is not necessarily more expensive than a regular one: when we consider climate conditions and implications from the start of the design process, we can build a green and energy saving house with the same costs of a conventional building.
For any question feel free to write me back, I will be happy to help!
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debby@dsearc.com
