What is a good U-value?

What is a good U-value?


The thermal transmittance indicates the amount of heat that is exchanged with the outside. In the façade of a building as a whole, the weak point is the openings, and it is particularly important to choose the right values.

Profiles: their thermal transmittance depends on the material and geometry of the profiles. The Technical Building Code includes a table (based on the European standard UNEEN ISO 10077-1) with the U-values of the most common materials used for window and door frames (PVC, metal and wood). These are the “default” values to be used in the absence of tests carried out by an officially recognized laboratory.

Calculation of r-value

Thermal transmittance (U, but also referred to as U-value in some places) is the measure of heat flow per unit of time and surface area transferred through a building system, consisting of one or more layers of material, with plane parallel faces, when there is a thermal gradient of 1°C (or 1K) of temperature between the two environments it separates.[1] In the International System it is measured in units of W/m²K or in W/m²°C.[2] In the International System it is measured in units of W/m²K or in W/m²K.

In the International System it is measured in units W/m²K or W/m²°C. Its value includes the surface thermal resistances of the building element faces, i.e. it reflects the heat transfer capacity of a building element in its actual position in the building. The lower the U-value, the lower the energy transfer between the two faces, and therefore the better the insulating capabilities of the building element. In the case of windows, it depends on the level of insulation of the profile and the glass.

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It is used to express the insulating capacity of a particular building element formed by one or more layers of materials. From a physical point of view it is the amount of energy that flows, in the unit of time, through a unit of surface of the element, when there is a unit thermal gradient. It is the inverse of thermal resistance.

How to calculate the k-value

The R-value indicates the thermal insulation capacity of a layer of material, often used as an insulating value for double glazing, walls, floors and roofs.  The R-value is the heat resistance of a material layer and is expressed in m 2 K/W. The higher the R-value, the greater the resistance to the passage of heat and the better the material insulates.

The calculation of the R-value depends on the materials found in the structure in question.  The thickness of the material, in meters, is divided by the λ value (the thermal conduction coefficient).  The higher the value, the better the insulation, a layer twice as thick will have twice the thermal resistance.

Thermal glass price

Indeed it is not totally technical to call them practicable (although it is a very ususal denomination not long ago I made a national study of denominations) but if we are going to be so rigorous we should call them I think (1) that is hinged and the “sliding” sliding. The denomination “hinged” is usually used to denominate the oscillating ones of inferior axis. All this if I am not mistaken comes in the standard UNE EN 12519:2006 Windows and doors.Terminology. I have at home the document of prUNE EN 12519 and unless it has finally changed so is the terminology …. (1) that’s why I put I think. The old UNE 85-202-81 if it called them hinged. Remember the name oscilobatiente (oscilantente + swing) but then it is the other way around what it does and is called in carpentry “oscilobatiente logical”.

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calderin I am surprised that you remind me, obviously, although it is not an excessively rigorous method if you did it by the UNE EN 10077 and UNE EN 12567 method “Hot box” as it should be done you would be surprised.