Formwork surfaces or walls with inhomogeneous cross-sections of limited mobility

Formwork surfaces or walls with inhomogeneous cross-sections of limited mobility require specially good-natured inside insulation systems due to the different physical properties. There is always a risk of over-insulating formwork surfaces and hindering the part’s ability to dry out. Special recommendations are also stated in the WTA information sheet E 8 5 00 D.

Cracks between the frame and the wood can always be expected in exposed formwork. When the façade is exposed to rain, these cracks can lead to a high water absorption, in particular on the side of the building exposed to driving rain. The water quantities absorbed here can exceed the dew quantities created many times over due to the capillary-active inside insulation. This water need to be able to dry out again, and this requires effective energy input.

If the framework is insulated with iQ-Therm, the energy input is so heavily reduced by the performance capability of iQ-Therm that drying can no longer by guaranteed. For this reason, the WTA information sheet specifies: “The additional inside heat insulation should not exceed the value of Delta Ri = 0.8 m²K/W.” When converted this means that the insulation layer thickness dmax may not be greater than Lambda x 0.8.

This means the following for iQ-Therm:
0.031 W/(mK) x 0.8 m²K/W = 0.0248 m = 24.8 mm.

The ideal system for energetic restoration of exposed formwork is iQ Therm 30.

  • None or very little moisture can penetrate framework that is covered, so that iQ-Therm can be used here.
  • The U-values specified in the EnEV are much lower for half-timber buildings than for other façades.

“If work pursuant to letter a, c or d is carried out on external walls that are assigned to the driving rain exposure group I acc. to DIN 4108-3: 2001-06 and which are in very protected positions, the requirements of section 1 are deemed satisfied if the heat transition coefficient of the created wall structure does not exceed 0.84 W/(m²•K)”.