FLIR InfraCAM User Manual page 125

2 Thermal insulation used here is assumed to have a conductivity of 0.03 W/m K.
3 The difference in temperature between an anomaly and the good areas is 1.2 de-
grees on the outside and 4.1 degrees on the inside.
4 The UKTA TN1 surface temperature factor for internal surveys is:
F = T – T /T
si sia so si
where:
T = internal surface temperature at anomaly
sia
T = external surface temperature (good area)
so
T = internal surface temperature (good area)
si
5 The UKTA TN1 surface temperature factor for external surveys is:
F = T – T /T
so soa si so
where T = external surface temperature at anomaly
soa
12.3.8.4.3 Selecting maximum acceptable defect area
The allowable area of defect is a quality control issue. It can be argued that there
should be no area on which condensation, mould growth or defective insulation will
occur and any such anomalies should be included in the report. However, a commonly
used value of 0.1% of the building exposed surface area is generally accepted as the
maximum combined defect area allowable to comply with the Building Regulations.
This represents one square metre in every thousand.
12.3.8.4.4 Measuring surface temperature
Measurement of surface temperature is the function of the infrared imaging system.
The trained thermographer will recognise, account for and report on the variation of
emissivity and reflectivity of the surfaces under consideration.
12.3.8.4.5 Measuring area of the defects
Measurement of defect area can be performed by pixel counting in the thermal anal-
ysis software or most spreadhseet packages provided that:
the distance from camera to object is accurately measured probably using a laser
■
measurement system,
the target distance should take into account the IFOV of the imaging system,
■
any angular change between the camera and the object surface from the perpen-
■
dicular is accounted for.
Buildings consist of numerous construction features that are not conducive to quan-
titative surveys including windows, roof lights, luminaries, heat emitters, cooling
equipment, service pipes and electrical conductors. However, the joints and connec-
tions between these objects and the building envelope should be considered as part
of the survey.
Publ. No. 1558299 Rev. a200 – ENGLISH (EN) – February 12, 2007
– T
so
– T
si
12 – Introduction to building thermography
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