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