Retrotec USACE - Manual (Page 396)

K8 ENERGY & PROCESS ASSESSMENT PROTOCOL
Humidity and thermal transfer have a strong impact on the U-value of large
old walls. Generally, existing materials in old buildings must not be replaced by
other kinds of materials with different thermal properties.
Wide and heavy walls provide a strong thermal inertia in old buildings.
They have to be preserved, particularly in southern areas, because of warmer
outdoors climatic conditions in summer.
Modern building techniques aiming at energy conservation measures may
not be adapted to old buildings. They may reduce the thermal qualities of ex-
isting buildings and after some years even damage and deteriorate the building
(cf. Figure K5).
Figure K5. Complexity of energy fl ows in old buildings.
K.5 Subsystem: Windows
The window openings provide access to daylight. They help recover the solar
contributions in winter and allow the regulation of air ventilation in summer.
However, they can generate thermal losses and create a cold wall effect, es-
pecially if there is a simple glazing, which is the case in many old buildings
(Figure K6).