Analysis of Duct Insulation Requirements for Ducts in Conditioned and Indirectly Conditioned Spaces

Measure Description

This report describes a study of issues associated with running uninsulated ductwork through
conditioned spaces in houses. The primary focus of the analysis is uninsulated ducts that pass though
vertical stud cavities, however other duct installations are also investigated.

The two key issues are:

1. the potential for condensation on cool duct surfaces, and
2. non-uniformity in grille delivery temperatures due to thermal conduction losses through the duct walls.

The two objectives of this report are:

1. to investigate both of these effects, and
2. to provide some guidance to the California Energy Commission on how to address the insulation level of ductwork running through conditioned and indirectly conditioned spaces.

The research performed included:

1. modelling of indoor dew points with CBECC-RES simulations, including comparison with existing measurements,
2. comparison of indoor versus outdoor dew point temperatures,
3. modelling of condensation/evaporation in building cavities with uninsulated ducts,
4. modelling of condensation/evaporation for insulated and uninsulated ducts located in rooms and in cavities for different surface emissivities, and
5. modelling of thermal losses from uninsulated ducts.

Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.

• Technical Report – Analysis of Duct Insulation Requirements for Ducts in Conditioned and Indirectly Conditioned Spaces