Thermal parameters of the facade

In recent years, more and more attention is paid to thermal parameters of the facades. According to Regulation of the Minister of Transport, Construction and Maritime Economy of 5th of July 2013, the value of Uc heat transfer coefficient for external walls may not exceed the values specified in the table below.

Room temperature Maximum allowable heat transfer coefficient Uc(max)[W/(m2 · K)]
from 1st January 2014 from 1st January 2017 from 1st January 2021 (*)
ti> ≥ 16°C 0,25 0,23 0,20
8°C ≤ ti < 16°C 0,4 0,45 0,45
ti < 8°C 0,90 0,90 0,90

ti – temperature of the heated room in accordance with §134 paragraph 2 of the Regulation.
(*) For buildings occupied by public authorities and owned by them.

The above values of heat transfer coefficient include corrections due to air voids in the insulation layer and mechanical connectors passing through the insulating layer. In case of ventilated facades, mechanical fasteners mean mainly pins that hold the mineral wool and an aluminium substructure system used to fix the cladding panels.

The above requirements should be taken into account in the design phase especially when choosing insulation wool with appropriate thickness and thermal conductivity as well as substructure system with favorable thermal insulation parameters. Thermal calculations should be performed in order to confirm that all the requirements and conditions have been met. According to the PN-EN 6946 standard, corrections for mechanical fixings and fasteners should be taken into account by detailed calculations described in the PN-EN ISO 10211 standard.

ATTENTION: It is a mistake to calculate the correction for brackets according to procedure described in point D.3.1 in PN-EN 6946 standard. This calculation method can only be used for elements with straight, simple and symmetrical shape (wool pins for example).

BSP solutions

Elements of the BSP aluminium substructure, in comparison with the competitive offers, are characterized by high durability due to innovative shape, dimensions and thickness of aluminium. Thanks to this amount of brackets needed is reduced and there is less so called “thermal bridges” which significantly improves the insulation performance of the entire facade. Moreover wide range of BSP products include multiple types of passive brackets designed and developed with constantly increasing thermal requirements in mind. They limit “thermal bridges” phenomenon to the minimum thanks to their shape and used materials.

Our company uses TRISCO (Physibel) for thermal calculations which allows us to build 3D models and calculate heat transfer coefficients according to a detailed calculation method in accordance with PN-EN ISO 10211. At the client’s request we select and design a substructure to meet all thermal insulation requirements and perform comprehensive thermal calculations for the designed facade. Sample thermal calculations are available for download below.

Sample thermal calculations: