Retrotec USACE - Manual (Page 397)

Appendix K K9
Figure K6. Various windows in facades of old buildings.
Other properties of the openings in old buildings make it possible to dis-
tinguish simple openings (simple windows with simple or double glazing) from
specifi c openings (double windows, oriels, and verandas). Simple openings are
easily characterized by their thermal performance. They allow solar contribu-
tions in winter according to their situation, size, and orientation. In summer,
these openings also have thermal regulation roles with shutters or possible
crossing air ventilation. However, their type of glazing does not always comply
with current regulation requirements regarding insulation. Infrared thermo-
graph shows defects in sealing for this type of windows in several old build-
ings.
In old buildings, all openings have a signifi cant function of air ventilation
strategy. A defective sealing is also the main source of natural air ventilation. To
replace old windows with tight windows can cause disorders related to humid-
ity fl ows and condensation.
Moreover, specifi c openings present particular thermal devices. They can
be the active thermal buffer spaces of the building. For instance, a double
window creates an air space in the building envelope between outside and
inside.
In winter or at midseason, the entering new air is preheated in this space
by a greenhouse effect, thus generating energy savings.
In summer, the outside window can be opened to cancel this greenhouse
effect. In addition, a shutter system placed in the space between the two win-
dows can protect the indoor climate from the solar radiation. Nowadays, such
a system is used in contemporary buildings in the shape of the double skin.
Thermal verandas, oriels, and bow windows are similar to double windows.
They are meant to create an active buffer thermal air space between the out-
side and the inside of the dwelling.
K.5.1 Recommendations
When old windows have to be replaced, it is necessary to check that the venti-
lation strategies effi ciently integrate the new performances of air-tight windows.