Building America Case Study: Compact Buried Ducts in a Hot-Humid Climate House, Lady's Island, South Carolina

Charles Booten, V. Kochkin, D. Mallay

Research output: NRELFact Sheet


A system of compact, buried ducts provides a high-performance and cost-effective solution for delivering conditioned air throughout the building. This report outlines research activities that are expected to facilitate adoption of compact buried duct systems by builders. The results of this research would be scalable to many new house designs in most climates and markets, leading to wider industry acceptance and building code and energy program approval. The primary research question with buried ducts is potential condensation at the outer jacket of the duct insulation in humid climates during the cooling season. Current best practices for buried ducts rely on encapsulating the insulated ducts with closed-cell spray polyurethane foam insulation to control condensation and improve air sealing. The encapsulated buried duct concept has been analyzed and shown to be effective in hot-humid climates. The purpose of this project is to develop an alternative buried duct system that performs effectively as ducts in conditioned space - durable, energy efficient, and cost-effective - in a hot-humid climate (IECC warm-humid climate zone 3A) with three goals that distinguish this project: 1) Evaluation of design criteria for buried ducts that use common materials and do not rely on encapsulation using spray foam or disrupt traditional work sequences, 2) Establishing design criteria for compact ducts and incorporate those with the buried duct criteria to further reduce energy losses and control installed costs, and 3) Developing HVAC design guidance for performing accurate heating and cooling load calculations for compact buried ducts.
Original languageAmerican English
Number of pages2
StatePublished - 2016

Bibliographical note

Work performed by Partnership for Home Innovation (PHI), Upper Marlboro, Maryland

NREL Publication Number

  • NREL/FS-5500-65261

Other Report Number

  • DOE/GO-102016-4797


  • Building America
  • buried ducts
  • compact ducts
  • ducts
  • ducts in conditioned space
  • home innovation
  • hot-humid
  • Partnership for Home Innovation (PHI)
  • residential
  • residential buildings


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