Retrotec USACE - Manual (Page 346)

G16 ENERGY & PROCESS ASSESSMENT PROTOCOL
The evaluation of a building’s thermal performance is usually required
F ■ or evaluating a need of renovation
When defects have been found in the building, the structures, or the ■
indoor climate
In the quality control of new buildings
■
The applications presented above are only a small sampling of the numer-
ous applications of IR thermography. The more precise and advanced the
methods are that are used, the greater the inspection costs will be. For this
reason, actions taken must be dimensioned according to the objectives and
the achievable savings. Ultimately, all building surfaces and structures are to
be inspected.
The consequences of actual insulation defects depend on the environ-
mental conditions; in cold climates, such defects cause more problems. The
greatest defects can be typically found in the tightness of the air-vapor bar-
rier, the joints of the outer walls, ceiling, and fl oor, and joints associated with
breakthroughs (electric tubing, ventilation ducts). Often the tightness of the
building envelope and ventilation system look like contradictive factors. The
defects that are related to the air-vapor barrier can be typically found in an
airtightness test (blower door test). For example, in buildings with a natural
ventilation system, the zero line of the pressure difference is somewhere at
halfway through the windows or about 30–50% of the height (depending on
the height of the building). In this case, at the joint of the ceiling and the
outer wall, there is, in normal conditions, a positive pressure drop, and warm
indoor air leaks out from the holes of the air-vapor barrier. In this case, air-
laden water vapor might condense on the structures. This kind of leaking
spot can only be found under negative pressure drop, when the direction of
the airfl ow is reversed.
Buildings with mechanical ventilation should have an airtight envelope
and a balanced ventilation system (thus having a slight negative pressure
drop). Uncontrolled air leaks increase the feeling of draft, especially if the
leakage spots are highly localized or close to the fl oor level. If the uncon-
trolled ventilation grows up to a high level, it might cause abnormal energy
consumption.
The most common way to improve the thermal performance (without taking
into account payback time) is to replace the windows, from one-pane to two-
paned, or three-paned in northern countries, to reduce heat transfer through
the window area. By using thermal imaging, it is possible to monitor window
conditions and estimate the necessity of their replacement as well as observe
defects in the seal of a double-paned window (Figure G17). By using thermal
scanning, both the average temperature of the windows and the convection
fi gure caused by the radiators can be evaluated. The temperature distribution
and the surface temperatures of the windows have an effect on how comfortable
it is to live, and especially work, in a certain room.