How to calculate the heat transfer coefficient?
The heat transfer coefficient (U) expresses the energy (usually in joules) that flows through 1 m2 of partition in 1 second with a temperature difference of 1K on both sides. Thus, we calculate it using the formula: [W/m2K]. This is an important value, needed to calculate the amount of energy lost by the whole object. It is essential to understand that this refers to a thermodynamic category, where heat represents the flow of energy between areas of differing temperatures. However, it is worth remembering that the vast majority of heat exchange with the external environment takes place in the process of conduction, described by Fourier's law.
The lower, the better
The heat transfer coefficient [U] allows us to determine how much heat loss we can cope with in ceilings, windows, walls, doors and other elements. It is important to consider the significance of the coefficient's magnitude. The lower it is, the better for the occupants. A lower U-value assures us that heat loss will not be large. This is favorable news for our finances, as it will help mitigate heating expenses.
It is important to note that, in the context of new construction, maximum heat transfer coefficients are defined by the Building Law. Accordingly, each partition in the building - such as ceilings, walls, floor - must be not only properly designed, but also properly insulated, for example using PIR boards, distinguished by a very low heat transfer coefficient.