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Factors the Affect Energy Saving in a Window

The energy saving in a window is determined mainly by three values: the solar factor, transmission losses and air infiltration.

The solar factor represents the solar energy that allows a certain enclosure to pass to the interior rooms and is the first one to take into account for energy saving in a window . It is calculated simply by dividing the solar energy that passes through the glass by the total energy that hits the glass. Obviously, the lower the solar factor in a glass, the lower the heating generated.

Let’s see how we can contemplate them with the aim of saving energy in a window in two different scenarios. If we are calculating it for a city with a cold climate, we will need the solar factor to be high, so that a lot of energy goes through the window so that the house is warmer and we need less heating. The opposite will happen when we are calculating for a city with a hot climate, we will need it very low so that the solar energy through the window is as small as possible and we need less cooling in the house. The solar factor will be important for energy saving in a window.

There are three factors that affect the energy saving in a window
The second variable that intervenes in the energy saving of a window is the transmission or better defined as thermal transmittance, which measures the temperature difference between the exterior and the interior of the enclosure, without considering the air flows or solar radiation.

The thermal transmittance of an enclosure is calculated in a proportional manner to the surface occupied by each of the elements of the enclosure, with which the glass takes on a great importance in the whole of the window, since it is the element that most percentage of the surface occupied in the window with an average of 75% and even in many cases exceeding 80%, assuming the largest surface of the window that transmits heat. With this it is very clear that the framework is not a determining factor in the energy saving of a window.

But really the factor that determines the energy saving in a window is the air permeability, which measures the losses by infiltration of air or what is the same, the unforeseen air renewals that take place inside the homes.

The number of closing points and quality of the hardware affect the air permeability of the enclosure, always counting that the window has no defects of manufacture or placement.

They also affect the air permeability and therefore the energy saving in a window the type of opening of the same, resulting in less infiltration in the case of hinged windows than in the sliding ones.

The air permeability must be a value that remains uniform throughout the life of the window, but not all are able to maintain these characteristics over time, so it is important to choose a window that by material and design it guarantees it, materials that dilate little, very resistant and that does not degrade with the sun and the meteorological effects. In this respect, aluminium with thermal break is an excellent option.

With all this, and contemplating these values very well, the use of slats or shutters in energy saving in a window will always help.

At Beautex Fenestration we are constantly improving the aluminium systems.

Energy saving in a window  by Beautex Fenestration for Construction –  Aluminium Systems.

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