Nowadays, energy efficiency is one of the key indicators used to evaluate the sustainable character of buildings. Certification schemes are being developed in many countries to evaluate and rate such building energy performance.
The thermal energy balance of buildings is a complex issue and there is currently no harmonised methodology to assess thermal performance. Many factors and parameters influence such performance, including building functionality, building design, climatic zone, season and orientation.
Intelligent facades incorporating aluminium systems can decrease energy consumption in buildings by up to 50%. The key feature of these intelligent buildings is their constructive interaction with the exterior, markedly reducing energy demands in heating, cooling, ventilation and lighting.
This is achieved through numerous techniques and processes including photovoltaics, optimized glazing systems, intelligent ventilation mechanisms and appropriate light and shade management.
To design glazed areas or windows properly, both the climate zone and orientation need to be considered carefully in order to optimise their contribution to the whole building’s thermal energy balance. In cold periods, heat losses need to be reduced while solar gains have to be maximized.
In such cases, large insulated double or triple glazed surfaces with high solar gains will be used in the most exposed orientation, as in passive houses or energy efficient buildings.
Maximizing the transparent areas of windows through the use of slender frames can also contribute to the optimisation of solar gain. Slender, thermally broken aluminium profiles can increase the transparent areas of windows by up to 20% compared to those equipped with frames made of competing materials. This increase in natural lighting is beneficial for the occupants’ comfort and well being, while at the same time reducing the need for artificial lighting, contributing significantly to the building’s sustainability.
The use of insulated aluminium shutter in cold periods will also limit heat losses at night. In hot seasons, solar gains need to be minimised in order to optimize the occupants’ thermal comfort or to reduce the air conditioning needs.
As a result, in warm regions, colored glazing with low solar gains should be used with associated shading devices, such as solar blades or shutters. In region where winter and summer temperatures vary significantly, it is crucial to design shading devices properly in order to optimise the solar gains of the glazed surfaces.
As a result, modelling or evaluating the contribution of glazing surfaces or windows to the whole building performance is not simple and needs to be done at the building level, considering all the features of the window system. Windows are usually perceived as elements contributing negatively to the energy performance of buildings.
However, intelligent designs, combined with responsible building use-behaviour can reverse this negative contribution. Everyone can contribute to a better energy balance by adapting heating, insulation, shading and ventilation according to the weather and to the season.