Some rules to reduce energy for houses IV

12. We are an indoor species

We spend about 90% of our time inside buildings. We use mainly fossil-fuel-derived energy to maintain comfort conditions within those buildings, and the production of that energy results in the release of CO2, a greenhouse gas linked with global warming and climate change. Unless we revert to being a mainly outdoor species, we must reduce our energy use.

Free heating, cooling, lighting in housing:

  • Free heating: direct, isolated and indirect solar gain
  • Free cooling: using earth, wind and water
  • Free lighting: daylight
  • Color

– In hot climate, keep the earth around a building cool.

– With shading, a pond on the roof will keep the building cool.

-Pipe in air that has been cooled by the earth.


-Use daylight to reduce energy use. We should aim to capture daylight and put it to use where it is needed. A day-lighting strategy might save up to 40% of energy consumption over an artificial lighting scheme.


A room will appear gloomy if more than 50% of the working place is beyond the line.


For the right amount of daylight you need the right size of window.


A tall window throws daylight deep into a room


Daylight is more plentiful overhead


Use roof-lights to bring daylight into large spaces

A room with dark interior finishes will need almost twice the window area of a light-colored reflective room, and this increase heat loss and/or heat gain. The further the window is from a room`s rear wall, the higher the reflectance of the finishes will need to be if there is no artificial lighting.


Exterior color influences energy use

A black wall or roof will absorb up to 20 times the solar energy of one which is white. In climates with cool/cold winters, darker absorptive solar-oriented roofs and facades will be good for heat gain. In hot desert regions, where solar intensity is high, white building will always be favoured.

Keep it simple

Building occupants will ignore complex controls and systems. Over time, they will forget how a building works. However people feel more comfortable when they have some control of their environment, so low energy-use architecture needs to be intuitive and simple.

13. Recover and reuse valuable heat

In a heating season (a winter in temperature and cool climates), heat generated in spaces such as kitchens and bathrooms can be recovered rather than expelled, and the heat exchanged with incoming fresh air, which, now warmed, is recirculated to where it is needed. Such systems need a well insulated and airtight envelope. In large complex buildings where some rules for natural ventilation might not be applicable, the whole building might adopt year-round mechanical ventilation with heat recovery.

14. Rules for single-sided ventilation


15. Rules for crossing ventilation



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