Civil Engineering Reference
In-Depth Information
6 Possible Intervention Analysis
A set of refurbishment actions has been evaluated on each case study, as shown in
Fig.
3
for case A and Fig.
4
for case B, which report the flow chart of the inter-
vention. Each intervention has been labelled by a code so that A0 and B0 indicate,
respectively, the energy performance models of the existing buildings, while A1,
B1, A2, B2, etc. represent the series of subsequent interventions. Moreover, the
different calculation methods adopted are marked with small letter: for example,
B1.a represents the first calculation test ''a'' for case study B (apartment) after the
action ''1''.
7 Main Result and Discussion
7.1 Determination of the Thermal Transmittance
The thermal transmittance, which characterizes the building envelope, represents a
significant parameter in the calculation of the building energy performance, mostly
during the heating season. Defining thermal transmittance can be more or less
accurate depending on the knowledge of wall's composition and on the reliability
of material thermal properties.
EN ISO 13790 establishes the thermal transmittance of each envelope element
to be determined in accordance with EN ISO 6946, but, in case of existing
buildings, a simplified method or default values, depending on the characteristics
of the considered structures, may be defined at national level.
In fact, UNI/TS 11300 Part 1 assumes that the evaluation of the thermal
transmittance can be performed in three different ways:
• by deriving thermo-physical properties of materials from product certificates, if
available, or
• assuming thermo-physical properties of materials from UNI 10351, UNI 10355
and EN ISO 6946 or from Appendix B of UNI/TS 11300 Part 1,
• by determining the thermal transmittance according to the building typology and
to the year of construction from Appendix A of UNI/TS 11300 Part 1, in default
of trustworthy design information about material and wall compositions.
This last method is the most approximate one for the thermal transmittance
estimation, because it does not take into account thickness and thermal conduc-
tivity of each layer which composes the wall, but rather it provides a thermal
transmittance value depending only on the kind of the wall and on its total
thickness.
