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How much do we save by changing the windows?

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A recent study claims that the savings could be up to 16% in warm zones, while reaching 19% in cold zones.

The AEA Spanish Association of  Aluminium and Surface Treatments has chosen Tecnalia, one of the accredited laboratories of Research, Development and Innovation (I+D+I) and one of the most renowned laboratories of the country to carry out the study entitled: “Determination of the significance of a window influential factors  in the energy demand in a building”.  This study intends to compare and quantify the savings that we can obtain when we change the windows in our homes.

In the study it has been used a typical residential block with a 30% of voids in the façade. The building has been modelled to meet the requirements of the CTE in its update of the 2013 DB HE (Energy Savings) for the Climatic Zones A y E (warn and cold). Afterwards 32 comparative simulations have been carried out with DesignBuilder, which uses EnergyPlus as calculation engine, modifying the following parameters:

  •  Air permeability: Amount of air that filters through the void.
  • Thermal transmission coefficient of the glass: Amount of heat lost or gained because of the glazing.
  • Solar factor: Relation between the radiation which fall upon the glass and the radiation that goes into the house.
  • Thermal transmission coefficient of the frame: Amount of heat lost because of the frame.
  • Frame percentage: connection between the total area of the void and the area occupied by the frame.


These simulations calculate data about savings in warm and cold climates, as well as the factors that influence the more in the reduction of energy demand. According to the study, the savings can be up to 16% in warm zones, while reaching 19% in cold zones.



Another remarkable point in the study is that if now we have 3000€ in climate-controlled expenses (heating and air conditioning), we would save 485 €/ year in warm zones and 570 €/year by changing our windows. If we just change the frame for an aluminium one, our savings would be 4, 80 €/year and 40 €/year respectively, having all the advantages that offers:


Useful links

AEA-Records (here)


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