It is the movement of water vapor molecules in a mixture of gases (e.g., air), aiming to equalize the concentration of vapor. Thanks to diffusion, water vapor can pass through partitions on the basis of equalization of the partial pressure prevailing on both sides of the partition. The course of this process depends on the conditions prevailing on the opposite sides of the partition. The process of diffusion of water vapor through a building envelope depends on the temperature and humidity of the air on both sides of the envelope (on the difference in partial pressures of water vapor on both sides).

It is a constant quantity for different types of materials, characterizing their diffusion resistance. The μ coefficient is defined as a relative value, indicating how many times the diffusion resistance of a layer of material is greater than the resistance of the same layer of air under the same conditions. For air μ = 1, and in the case of lightweight porous insulation materials with good thermal insulation, the value of the μ coefficient approaches 1.

It combines the DIFFUSION RESISTANCE COORDINATOR - "µ" with the thickness of the material - "d"; Sd=µ-d. It can be interpreted as the thickness of a stationary layer of air that poses the same diffusion resistance as the layer under test. The equivalent diffusion resistance coefficient (Sd) is the diffusion-equivalent thickness of the air layer that provides resistance to water vapor. Sd is expressed in meters. The smaller the value, the lower the resistance, and vice versa.

It is the difference between the indoor surface temperature and the outdoor air temperature, divided by the difference between the indoor and outdoor air temperatures, calculated assuming that the heat transfer resistance at the indoor surface is Rsi. The temperature coefficient f is an indicator of the lowest internal surface temperature f_Rsi of a particular joint. It is actually a dimensionless temperature describing the temperature of the inner surface, independent of the exact boundary conditions, with a value between 0 and 1 (the closer the value to 1, the better protected the joint). Building components must ensure the elimination of the risk of local mold and surface condensation on the inner surface of the joint.

The ability to limit (regulate) the passage of water vapor through the partition. The issue of diffusion tightness is closely related to the moisture state of building partitions, and in particular to the provision of such a partition moisture that can be considered correct, that is, not causing negative thermal and operational consequences. A diffusion-tight partition is such a partition into which water vapor should not penetrate in an uncontrolled diffusive manner, and the type and arrangement of the layers of this partition ensure that it is not threatened by internal condensation (condensation of water vapor at reduced temperature), especially increasing in subsequent years, which can lead to increasing moisture in some layers, and as a result, to the development of fungi and biological degradation.

Air tightness affects operating costs, acoustic properties, thermal efficiency of the building and thermal comfort of the occupants. One of the key places to ensure airtightness are the junctions between the jamb and the frame. Poor sealing of this joint accounts for about 15% of the total air loss in an average single-family home.

The occurrence of strong, gusty wind gusts is often associated with another unfavorable weather phenomenon - heavy rain. It is very important whether the window structure and the junction of the window and frame with a certain wind load strength will also maintain watertightness against rainwater penetration into the interior. Watertightness, is another property of the window and joint, in which the pressure exerted on the structure by the wind plays a considerable role. Windows and connectors bearing the E1200 designation will begin to allow water to penetrate the structure only at a pressure of 1,200 Pa, which means that leaks could happen if the falling rain was accompanied by a hurricane blowing at more than 160 km/h.

The λ value is an indicator that determines the energy efficiency of a building material - the lower the λ value, the better the material insulates the joint. It should be remembered that it is the junction between the jamb and the frame that is the classic linear thermal bridge. The minimum requirement for the junction between the jamb and the frame, the 3D correction factor at the junction ψ, is 0.10 W/mK. Linear thermal bridges, which are the junctions of the frame and jamb, account for an important part of the total heat loss in the building - their impact in this regard is usually overlooked by designers, and with poor detailing can be very large. Condensation and mold often occur on the inner surface of thermal bridges, especially with increased humidity in the room. That's why it is so important to properly insulate the junction between the jamb and the frame.

A thermal conductivity coefficient that characterizes a building material or product; it shows how much heat will pass through a material regardless of its thickness. The lower the lambda coefficient, the better the insulating material.
Unit: [W/(m*K)]

A value that determines the ability of a product to stop heat loss; it depends on the thickness of the material and thermal conductivity - the thicker the layer, the greater the resistance and the less energy escapes to the outside of the building.

Parameter characterizing the insulating properties of building partitions, e.g. ceilings, walls, windows, determining the amount of heat that penetrates a given partition; U-values for partitions calculated in accordance with Polish Standards must not be greater than the U(max) value. The lower the U-value, the better the insulating properties of the partition.
Unit: [W/(m2*K)]

Sound insulation requirements are placed on the entire external structure of the building, including all the elements installed in it. The sound insulation coefficient R'w,res of the exterior part of the building(exterior wall + windows) is determined. When planning the wall joints, care should be taken to ensure that the noise is suppressed as much as possible. For a well-insulated and sealed joint, the value of Rs,w should be ≥ 45 dB for a 20 mm joint.