Publication

Impact of air-flow on thermal performance of air-spaces behind cladding (ASHRAE 1759-TRP)

Dolaana Khovalyg, Mohammad Rahiminejad
2020
Reports

Abstract

The project ASHRAE 1759-RP addresses the impact of the ventilated cavity behind external claddings on the thermal performance of the wall structure by defining “effective thermal resistance” of air gaps based on the linearized network of thermal resistances that is the basis for building components energy code compliance applications. The magnitude of the impact significantly depends on conditions such as air flow rate, air temperature, and incident solar flux. Even for steady-state and no solar conditions, the air space could be able to resist the heat flow even more than certain wall components. For certain air change rate values, ventilation air flow in the air cavity effectively off-sets or diminishes the thermal resistance contribution of the cladding to the overall wall assembly, and the cladding thermal resistance no longer fully contributes to the simple linearized network of thermal resistances. The project provides suggestions to improve thermal design accuracy to support code-compliant use of the ventilated air spaces by accounting for the thermo-hydrodynamic behavior of the airflow, and it provides recommendations to modify the ASTM C1363-19 test method to incorporate and study air flow-related effects considering possible uncertainty of measurement.

Official source

https://infoscience.epfl.ch/entities/publication/3d9feb6e-993e-46c2-9ce4-d89aff72ebf9

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Dolaana Khovalyg, Mohammad Rahiminejad
2020
Reports

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/3d9feb6e-993e-46c2-9ce4-d89aff72ebf9

About this result

Related concepts (32)

Thermal conductivity

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by , , or . Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials like mineral wool or Styrofoam.

Heating, ventilation, and air conditioning

Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR (as in the designation of HACR-rated circuit breakers).

Ventilation (architecture)

Ventilation is the intentional introduction of outdoor air into a space. Ventilation is mainly used to control indoor air quality by diluting and displacing indoor pollutants; it can also be used to control indoor temperature, humidity, and air motion to benefit thermal comfort, satisfaction with other aspects of the indoor environment, or other objectives. The intentional introduction of outdoor air is usually categorized as either mechanical ventilation, natural ventilation, or mixed-mode ventilation (hybrid ventilation).

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