A correction factor to approximate the design thermal conductivity of building materials. Application to Spanish façades

• Published in: Energy and buildings 2015-02, Vol.88, p.153-164
• Main Authors: Pérez-Bella, José M., Domínguez-Hernández, Javier, Cano-Suñén, Enrique, del Coz-Díaz, Juan J., Álvarez Rabanal, Felipe P.
• Format: Article
• Language: English
• Subjects: Building envelope; Buildings; Construction; Design thermal conductivity; Heat transfer; Mathematical analysis; Moisture content; Regulations; Spain; Temperature; Thermal conductivity; Thermal design
• ISSN: 0378-7788
• DOI: 10.1016/j.enbuild.2014.12.005

•Functional approximation to the design thermal conductivity of building materials.•Correction of the normative conductivity values established by building regulations.•Implementation in façades of 52 Spanish sites considering its climatic conditions.•Validation analysis regarding the design values calculated through ISO 10456:2007. The thermal conductivity of building envelope materials varies according to the conditions of temperature and moisture content. Precisely determining the thermal conductivity is a primary challenge in developing more appropriate, realistic thermal designs for buildings. However, a detailed implementation of environmental conditions requires either the use of sophisticated software programmes and the collection of a large set of climate data at each location or a laborious analytical calculation. To simplify the thermal design of buildings, regulations use normative conductivity values based on constant, standardised conditions of temperature and moisture content, which are independent of ambient conditions. This article proposes a correction factor that considers these conditions to functionally approximate the design thermal conductivity of materials based on their normative values. For this calculation, a procedure that simplifies the standard ISO 10456:2007 using the mean annual temperature and relative humidity data for each location is proposed. The procedure is applied in 52 Spanish cities to correct the conductivity values established by the Spanish regulation for façade materials. A correction map of Spain is presented. Finally, by using the ISO standard, the corrections are validated by comparing the values with the design thermal conductivities calculated for different case studies.