Wood-aluminium window Natura Solid 110

There are six resistance classes with increasing protective effect from RC1N to RC6 in accordance with the European standard DIN EN 1627 (the old designation, used until September 2011, was WK 1 to WK 6). RC stands for Resistance Class.

RC1N - Attempted break-in using physical force such as kicking, body-slamming, jumping against, levering up and the like. Elements of this resistance class are therefore mainly suitable as protection against vandalism. Windows of resistance class 1 offer only very low burglary protection.

RC2 - The opportunist offender additionally attempts to force the window open using simple tools such as a screwdriver, pliers or wedges. Windows of resistance class 2 offer low to average burglary protection.

RC3 - The offender additionally attempts to gain entry using a second screwdriver and/or a crowbar. WK3 windows offer high burglary protection. In a private household, protection to resistance class RC 2 and RC 3 is usually sufficient.

RC4 - The experienced offender additionally uses sawing and striking tools, e.g. an axe, crowbar, hammer and chisel, as well as a cordless drill. Windows of resistance class 4 offer very high burglary protection.

RC5 - The very experienced offender additionally deploys power tools, e.g. a drill, jigsaw or reciprocating saw and an angle grinder with a maximum disc diameter of 125 mm. Windows of resistance class 5 offer very, very high burglary protection. The resistance time is at least 15 minutes. 

RC6 - The very experienced offender additionally uses power tools such as a drill, jigsaw or reciprocating saw and an angle grinder with a maximum disc diameter of 230 mm. Windows of resistance class 6 offer extremely high burglary protection, and the resistance time is at least 20 minutes.  

A RAL colour refers to standardised colours from a colour collection that has been authoritative for colour selection for over 85 years and is distributed by RAL GmbH under the name RAL Classic.

Each colour in the colour catalogue is assigned a four-digit colour number. The first digit is systematic: 1 - yellow, 2 - orange, 3 - red, 4 - violet, 5 - blue, 6 - green, 7 - grey, 8 - brown, 9 - white/black shades, and the remaining three digits are chosen sequentially.

For a surcharge, almost all products, such as timber windows, timber-aluminium windows, aluminium windows, roller shutters and external window sills, can be produced in a RAL colour of your choice.

The thermal transmittance coefficient, abbreviated U for unit of heat transfer (the unit of heat transfer), replaced the k-value in the course of European standardisation. Measuring the U-value determines the heat loss from the inside to the outside, specifically per square metre and per hour at a 1° temperature difference.

A window's thermal insulation depends on the frame material, the glazing and its airtightness. A window's insulating properties are determined by the U-value. The lower this figure, the better the thermal insulation.

For windows, three U-values are generally distinguished. The thermal transmittance coefficient Uw refers to the entire window. This value incorporates the U-values for the glazing Ug and the frame Uf.

• Uf = U frame – is the U-value of the window frame.
  The Uf-value is determined by measurement for the frame-and-sash combination. The visible width of the profile is taken as the area for calculating the Uw-value.

• Ug = U glazing – is the U-value of the glazing.
  The Ug-value depends on the type of gas filling in the cavity between the panes, the distance between the panes and the number of panes.

• Uw = U window – is the U-value of the entire window.

The thermal transmittance coefficient for windows is generally calculated for the standard window size of 1.23 m x 1.48 m. Please note that larger glass areas achieve better values, since glazing allows better U-values than the frame material.

Under OIB Guideline 6 of 2011, the Uw-value for standard glazing must not exceed 1.4 W/m2K. The German Energy Saving Ordinance (EnEV) of 2014 limits the thermal transmittance coefficient to 1.3 W/m2K for an existing building. Windows with a Uw-value no greater than 0.8 W/m2K are considered suitable for passive houses.