DIN EN 17887-2:2024-11

This document has been prepared by Working Committee NA 005-56-98 AA "Wärmetechnisches Messen (SpA zu CEN/TC 89/WG 8, WG 13 und WG 14, ISO/TC 163/SC 1/WG 15, WG 16, WG 20 und WG 21)" "Measurement of thermal properties (national mirror committee for CEN/TC 89/WG 8, WG 13 and WG 14, ISO/TC 163/SC 1/WG 15, WG 16, WG 20 and WG 21)". One factor that can have a significant impact on the energy consumption and carbon dioxide emissions of buildings is the performance of the building fabric. Since the performance of the building fabric has traditionally never or only rarely been tested on site, it was assumed that it functioned as originally designed. In recent years, however, a wealth of empirical evidence has emerged showing that there can be a discrepancy between the theoretical performance of the building fabric and its actual performance on site. This discrepancy between designed and measured performance is commonly referred to as the "performance gap" of the building fabric. For this reason test methods have been developed in CEN/TC89, WG 13 that measure and verify the performance of building fabric on site and can determine the extent of a possible "performance gap". The aim of the DIN EN 17887 and 17888 series of standards is to provide a test method (Part 1) and an analysis method (Part 2) for measuring the aggregate in-situ heat loss of a building or test sample. This test and analysis method can be used as a sampling verification method for large-scale production, as confirmation of prototypes, as confirmation of the performance of particularly important buildings, and possibly as a diagnostic tool for determining the actual performance of individual building components and as a basis for further investigations and measures. The test method is applicable to both newly built and existing domestic scale detached buildings and attached domestic scale buildings, such as semi-detached houses, terraced houses and apartments. Specially manufactured test specimens representing individual building elements (building structures) do not fall within the scope of the EN 17887 series of standards, but are covered by the EN 17888 series of standards. Part 2 (analysis method) of the EN 17887 and EN 17888 series of standards is almost identical and is based on the same research work, measured under British weather conditions, see reference texts [6]. The investigations included few periods with more extreme thermal boundary conditions (such as nighttime cooling under clear skies, higher solar radiation, etcetera), and therefore the measurement uncertainties and error tolerances specified in Annex D are only of limited applicability to locations in Germany with more variable environmental conditions. For this reason, Annex D is for informational purposes only. It can be assumed that measurement uncertainties of +/-20 % or higher apply (and not the specified +/-6,3 %) for houses and building structures where not all building elements and materials have undergone special thermal measurements in the laboratory in advance. A more realistic estimate of in-situ measurement uncertainty is given in ISO 9869-3 "Thermal insulation of building elements, In-situ measurement of thermal resistance and thermal transmittance – Part 3: Probe insertion method":2023, A.5.3, 5.4, and B.4. Since the effort involved in carrying out such in-situ measurements on entire houses or special structures over many weeks is high, experience with these measurement methods in Germany is limited, but has been available in some institutions for many years and should be further tested.