In-situ thermal transmittance assessment for appraising the actual building thermal performance

Energy diagnosis and check of energy performance of traditional houses are becoming urgent and essential to achieving energy saving in the residential sector. The paper presents the results of experimental studies focused on the enhancement of the methods to assess the energy efficiency in traditional houses. In these houses, the thermal performance of opaque elements cannot be correctly assessed, because there are not commonly accurate data about the U-values, which are the most important subject which impacts on the steady-state thermal transmission. Although the national laws offer standards information of U-values particularly for new construction, they only consider a few constructive technologies, and they are sometimes inappropriate regards to the wall thickness. Also, they do not usually consider the influence of the inner humidity of the components.This paper is focused on U‐values as an indicator of thermal energy efficiency of traditional houses and involves in-situ measurement and the subsequent comparison with U-values calculated by a software tool, through the knowledge of thermal conductivity values and thickness of the elements constituting each layer. The method has been performed on thirteen walls made of stone, brick, solid mud and mixed materials and one insulated roof.It has been concluded that in the case of masonries, the differences between the standards and in-situ measurement U-values varies considerably 8% to 23.5%. In addition, these differences are within a range of 4.7% to 12.8% in the brick construction houses, due to the different thermal conductivity of brick materials. Also, there is a substantial difference of 42.5% for solid mud construction. Although, for the brick walls, particularly the new ones with an insulation layer, the standards and U-values calculated by energy simulation software can be used, for very old houses of stone walls, it is not appropriate to trust these calculated U-values.

In-situ thermal transmittance assessment for appraising the actual building thermal performance Keywords:

In-situ measurement , Thermal transmittance , Heat transfer coefficient (U-value) , Building energy performance simulation , Traditional dwellings