EKS-HUM-021 / Condensation, measurement and control

Surface Temperature

表面温度

Surface temperature is the temperature at the boundary of a material, component or item of equipment at a specified location and time.

Aliases: local surface temperature

QUANTITY, SYMBOL AND UNIT

Quantity / objectSurface temperature

SymbolT_s, t_s

SI°Cdegree Celsius

SIKkelvin

IP°Fdegree Fahrenheit

Definition

Surface temperature is the temperature at the boundary of a material, component or item of equipment at a specified location and time.

For condensation screening, the relevant value is usually the lowest credible temperature of a surface exposed to the local moist air. It may be measured directly or calculated from heat-transfer conditions, but the method and location must remain identifiable.

Relations and distinctions

Surface and air temperature

Air dry-bulb temperature describes the air at a measurement point; surface temperature can be higher or lower because of conduction, radiation and local airflow.

Measured and calculated surface temperature

A contact sensor, infrared measurement and a thermal model have different spatial resolution, emissivity and uncertainty boundaries.

Engineering meaning

Identify cold corners, penetrations, frames and other local paths rather than relying on one accessible surface point.
Compare a conservative local surface temperature with the corresponding local air dew point.

Common misconceptions

MisconceptionRoom air temperature is a reliable substitute for every surface temperature.

Accurate explanationThermal resistance, geometry, radiation and airflow can create local surface temperatures far from the room-air reading.

Application boundaries

Infrared readings require a suitable emissivity and reflected-temperature treatment.
A steady calculated minimum may not capture start-up, weather changes, solar loss or equipment duty cycles.

Supporting sources

International Organization for Standardization / SRC-ISO-10211-2017-SCOPE

ISO 10211:2017 - Thermal bridges in building construction - Heat flows and surface temperatures - Detailed calculations ↗

2017 / Public abstract and scope
Supports: Minimum surface temperature is a calculated quantity used to assess surface-condensation risk; Geometry, thermal boundaries and material properties belong to the calculation context
ASHRAE / SRC-ASHRAE-F25-CH01

ASHRAE Handbook - Fundamentals, Chapter 1: Psychrometrics ↗

2025 SI edition / Chapter 1, dew-point definition and moist-air cooling relation
Supports: The air dew point supplies the saturation comparison temperature

Maintenance record