Table 1: Layers and transmittance value of the vertical walls in the current state
STRATIGRAPHY CONDUCTIVITY THICKNESS THERMAL RESISTANCE Liminal inner layer-- 0.13 Civil plaster and gypsum 0.70 0.02 0.03
Concrete blocks of pumice |
0.20 |
0.25 |
1.25 |
stone |
|
|
|
Plaster type“ Li Vigni” |
0.64 |
0.03 |
0.05 |
Liminal outer layer-- 0.04 THERMAL TRASMITTANCE U
0.67 W / m2K
The current value of the transmittance of the opaque envelope is U = 0.67 W / m2K, which happens to be a value greater than the transmittance limit imposed by the law for the climatic area“ B”, in which lies the city of Palermo( Italian Decree n. 192 / 2005) that is, instead, equal to 0.48 W / m2K. In addition, a further verification was performed on the other characteristics of the dwelling that determine behavior in summer mode: surface mass( Ms) and periodic thermal transmittance( Yie). These results, when compared with the respective limits, require adequate interventions of opaque envelope insulation, such as to adapt their characteristics to those prescribed by current laws.
The table 2 shows the main thermal and dynamics characteristics of the opaque wall, in the current state:
Table 2: Comparison between the key thermal characteristics and with the limits established by law
Thermal and dynamic characteristics Law requirements Current state
Thermal transmittance U [ W / m2K ]
Surface mass Ms [ kg / m2 ]
Dynamic transmittance Yie [ W / m2K ]
0.48 0.67
230 255
0.12 1.51
Results by adding different insulating panels
Once analyzed the current state of the dwelling envelope, and understood the low energy performance of the opaque walls, it is necessary to compare some actions that could be possible to applied as energy retrofits.
Eco-friendly materials for the energy retrofit of existing buildings 589