How to calculate the heat transfer coefficient

The construction of energy-efficient houses largely involves increasing the thermal insulation of the building. The degree of insulation is determined by the heat transfer coefficient of the various elements of the house. The value applies to the roof, walls, doors, windows, as well as foundations, among others. How to calculate the heat transfer coefficient?

Heat transfer coefficient U – what is it?

The definition of the heat transfer coefficient is the amount of energy that penetrates a given building envelope of a house. We use this value to determine the energy loss of a given structural element of the house. The heat transfer coefficient refers to building partitions such as walls, windows, or doors. Simply put, it captures everything that connects the inside to the outside. The value of the heat transfer coefficient is expressed in watts, hidden under the abbreviation W/(m2*K). In determining the coefficient, aspects such as the temperature difference or the surface area of the building envelope in question are taken into account.

Why is the heat transfer coefficient U important?

The heat transfer coefficient is extremely important when building a house. The number shows how much air escapes outside the building. Among other things, it is related to heating costs. When building a house, we should aim for the lowest possible heat transfer coefficient of each structural element of the building. This will make interior heating more efficient and reduce maintenance costs.

The formula for the heat transfer coefficient U

Not all manufacturers of windows or doors specify at the time of sale what heat transfer coefficient the product has. The same applies to walls, roofs or foundations. The formula for the quality of thermal insulation is not difficult, so we can easily determine its value or verify the data provided by the manufacturer.

The first formula for the heat transfer coefficient is U = λ/d. “U” is the value of the coefficient, “λ” the thermal conductivity, and “d” is the thickness of the element or building block. This scheme applies to uniform materials.

In turn, when we are talking about a partition created from several materials, it is necessary to use the formula R = d/λ for each building layer. The result obtained determines the thermal resistance of the partition. The numbers should be added up with the earlier calculation of the heat transfer coefficient. Then we use the formula -U = 1/R. Nowadays, when calculating the coefficient, a great convenience are websites that offer the service of a heat transfer coefficient U calculator.