How much heat escapes through the windows and external walls of the building? Impact on home insulation

How much heat escapes through the windows and external walls of the building? Impact on home insulation

17th September 2019 Off By krzys

In single-family homes, the largest percentage of energy is used to heat the building. Heat escapes through walls, windows and doors as well as through the roof. However, heat losses can be significantly reduced by using appropriate wall and roof insulation. Large heat losses are also caused often by the use of incorrect windows and / or by their incorrect installation. How much heat escapes through the external walls of the house and through the windows? What insulation materials should be used to increase the energy efficiency of the home? How to prevent heat loss? We answer these and other questions below.

Nowadays, great importance is attached to energy efficiency in the construction industry – both single-family and multi-family. The heat transfer coefficient is one of the most important parameters in this area. Investors make sure that the house after construction generates the lowest operating costs. Small heat losses translate into lower heat bills.
What allows you to calculate the coefficient?

The aforementioned heat transfer coefficient (U) given in W / m²K is a parameter that allows calculating how much heat escapes through various partitions such as walls, windows or roof. The heat transfer coefficient also makes it possible to compare the properties of different insulation and partitions. The lower the heat transfer coefficient, the better the barrier has insulation properties – Upvc windows


What does the heat transfer coefficient say?

In other words, the heat transfer coefficient will tell us what heat losses we need to prepare for and whether the heating bills will be high or low. Good insulation and windows are not enough to achieve a low U-value. If there are thermal bridges in the partition, it means that the partition is not tight and the U-value will be higher.
Heat transfer coefficient value

From the beginning of this year for newly built houses, the heat transfer coefficient for walls can be at most 0.23 W / m²K. (legal basis – Regulation of the Minister of Infrastructure of 12 April 2002 on the technical conditions to be met by buildings and their location, as amended) For windows, this parameter was set at 1.1 to 1.6 W / (m2 · K) depending on the type of windows.

How much heat escapes through the windows?

about how much the windows cost and whether they are nice is certainly very important information. However, the most important thing is that they have a low heat transfer coefficient and are correctly installed without creating thermal bridges. In addition to heat losses, windows also generate profits. Sunlight falls through the windows, heating the interior – of course these are not big profits, but in passive houses every window is carefully thought out and located at this angle.

There are three U indicators for windows. Uw is the heat transfer value for the whole window together, Ug – the heat transfer parameter for the glass and Uf, i.e. the heat transfer value through the frame.

Energy-saving windows

Window manufacturers state the heat transfer coefficient for individual models. It is worth choosing energy-saving windows, not only because of the law, but from pure savings measured over the years, at which saving when buying windows seems to be completely irrelevant. Experts say that we can lose up to 20-30% of heat through doors and windows.

double vs triple glazing

In addition to the selection of windows with the right, i.e. the smallest U-factor, it should be remembered that the windows should be installed by specialists. Installation errors can affect the loss of thermal insulation properties of the window.

Our vigilance should arouse the fact if the manufacturer or seller in the window information only gives the Ug (glass) coefficient instead of Uw. This may mean that the parameters for the entire window are unsatisfactory.

How much heat escapes through the exterior walls in your home?

How much heat escapes through external walls in a home depends on many factors, but one of the most important is the type and thickness of the thermal insulation used, i.e. the building’s insulation. In the case of insulation materials, the heat transfer coefficient is also used, but it is determined differently – λ – lambda. As in the case of walls or windows, the lower the coefficient, the better the material will have insulation properties, and thus a thinner layer of insulation can be used to achieve the same parameters.