E n e r g y R e c o v e r y o f ‘ 7 0 e s I n d u s t r i a l i z e d B u i l d i n g
519
Basing on technological and orientation analysis, one of the buildings with the
longitudinal facades to north-east and south-west sides and the transverse ones to
north-west and south-east was chosen as case-study.
For a better energy analysis, thermographies were performed in different days and at
different times from different angles to avoid misinterpretations due to temperature
reflected by other surfaces and occasional heat absorbers (plants, linens, furniture).
Thermography allowed identifying the location and types of main thermal bridges of the
analyzed buildings. In particular, as shown by the thermography of the longitudinal
facades thermal bridges were discovered in the variations of the shape, corresponding in
this case to the corners, but above all where materials changed (in the reinforced
concrete walls and slabs) (Fig.6).
Thermographic analysis was carried out on the r.c. transverse walls, where apparently
there was no material discontinuity, and the presence of thermal bridges was discovered
in the thickness of the slabs, due to the internal insulation, made of polystyrene sheets,
ended next to the slabs.
Furthermore, through the thermograms, it was possible to detect thermal differences,
particularly those between areas of the same thermogram and between same areas
related to thermograms made at different times (on different days and different times of
the day, with opposite solar exposure conditions between morning and afternoon).
These thermograms showed that there is temperature difference between reinforced
concrete walls and slabs and the walls of about 1.6 °C, related to the longitudinal walls
facing north-west in both conditions. In the transverse walls facing south-east between
r.c. walls and slabs, there is temperature difference of about 0.5-0.8 °C.
Furthermore, the thermogram (by the shooting on different days) of the r.c. transverse
walls facing south-east was red, because the wall is much warmer than the wall facing
north-west, having been exposed to the sun for almost 8 hours (from 6:00 a.m. to 15:00).
The best thermograms were made when the wall was in shade because shooting is not
affected by sunshine.
In the second phase, it was conducted the energy evaluation of the thermal performance
of several building elements, constituting the envelope, as to quantify the energy
improvement required and the best technological solutions to achieve it.
The calculation of thermal transmittance of walls and roofs was conducted according to
regulatory requirements and UNI standards.
The thermal transmittance is given by the inverse of the sum of the partial thermal
resistances, related to the different functional layers of the technical elements, and those
of air in contact with the inner and outer surfaces. The internal resistances, marked with
Rn, due to the mechanism of thermal conduction between the various layers depending
on thickness and material, were calculated according to the UNI standards.
