We have seen that measures reducing energy demand are amongst the most cost effective measures to mitigate CO2 emission. This focus on demand side measures is the basis of the Trias Energetica principle. Applying this approach to construction, design of low energy buildings starts with a building envelope that prevents unnecessary loss of energy. The key parameters are thermal insulation and air tightness of the building. Only after the building envelope is established are the higher levels of the triangle considered. 

This integrated design strategy follows three steps:           

 

 1.             Minimize energy demand for cooling and heating of the building   

Optimise building form and zoning; apply highly insulated and air tight conventional envelope constructions; ensure low pressure drops in ventilation air paths; apply efficient appliances to reduce heat load, etc. Apply responsive building elements if appropriate, including advanced facades with optimum window orientation, exploitation of daylight, proper use of thermal mass, redistribution of heat within the building, dynamic insulation, etc. Provide intelligent control of systems including demand control of heating, ventilation, lighting and equipment.  

2.             Utilise renewable energy sources

Provide optimal use of passive solar heating, natural lighting, natural ventilation, night cooling, etc. Apply solar collectors, solar cells, geothermal energy, ground water storage, biomass, etc. Optimise the use of renewable energy by application of low energy systems. 

3.             Efficient use of cleanest fossil fuels

If any auxiliary energy is needed produce it by using the least polluting fossil fuels and in an efficient way, e.g.  heat pumps, high-efficient gas fired boilers, gas fired combined heating and power (CHP) units, etc. Apply efficient heat recovery of ventilation air during the heating season; Apply energy efficient electric lighting.  

Appropriate thermal insulation is the largest single factor which influences the energy performance of buildings. According to the climate alliance (ref 6) energy efficient buildings could reduce carbon dioxide emissions by 460 million tonnes a year (more than Europe’s total Kyoto commitment) and could reduce energy use by the equivalent of 3.3 million barrels of oil a day and save Europe 270 billion Euro a year in energy costs. Other results would be improved energy security, reduced air pollution, job creation and poverty alleviation.   

 In Europe considerable building activity can be expected over the coming decades. New buildings will continue to be erected but probably more important will be the fate of old building stock which either needs to be refurbished or demolished in order to meet new regulations.  In Germany, for example, already 70% of all insulation activity is related to renovation and this percentage is expected to rise even further as a direct consequence of the need for improved energy efficiency.

Building design and performance will need to change as public and legislative awareness increases on the need for energy efficiency and reduction of greenhouse gase