Retrotec USACE - Manual (Page 391)

Appendix K K3
Complementary to the analytical approach, a holistic approach aims to con-
sider an old building in its complexity and its dynamics. It allows taking into
account the different levels of complexity of an old building within several sub-
systems: environment and site, indoor distribution, traditional building tech-
niques, envelope, windows, equipment, and occupants (Figure K1).
K.2 Subsystem: Environment and Site
This subsystem is the ecosystem in which the old building is immersed. Local
environmental constraints can have a signifi cant impact on energy perfor-
mance.
As regards energy behavior, an old building is dependent on immediate
environment and is more sensitive than a modern building. A modern building
is often designed like a closed system in which the exchanges of energy fl ows
with the outside are mechanically controlled. The local climatic environment
and the site factors have not been a priority for the designer. The modern
building is tight and impermeable. It is a mechanically ventilated box and thus
less sensitive to the external environment.
An old building works like an open system. Its envelope is generally a per-
meable boundary of the system, receiving and controlling the solar fl ow. There
are several exchanging air and humidity fl ows by infi ltration and natural ven-
tilation. Thus, in old buildings, there are strong thermal interactions between
indoor and outdoor environment.
The situation of the building is generally defi ned in its immediate neigh-
borhood by the following constraints:
Microclimate (wind, temperature, precipitation, exposure to sunshine, ■
altitude, mountain or littoral area, urban or rural area, etc.; e.g., Figure
K2)
Close relief (a cliff may moderate the changes in air temperature; an
■
embankment slope may bring thermal attenuations, etc.)
Solar shading (other buildings, persistent vegetation, etc.)
■
River
Evaporation Evaporation
River
Figure K2. Example of microclimate around an
old building.