Residential Attics and Cathedral Ceilings

Introduction
As a result of this research program, we hope to gain a better understanding of the construction, ventilation, thermal performance, and energy flows of residential attics and cathedral ceilings. Improved attic testing procedures and insulation strategies, along with a fundamental understanding of the air distribution systems within attic spaces, will lead to better-insulated and sealed ducts and more energy-efficient houses.

Issues
The roof/ceiling of a house is one of the largest sources of heating and cooling loads, representing about 20~30 percent of the heat loss or gain through the building envelope. Many houses, especially in the Sunbelt, have air distribution systems in attic spaces. Heat gains and losses through the duct walls due to conduction and air leakage to or from the attic air space can seriously degrade the overall energy efficiency of the heating / cooling system. Even small improvements in the energy efficiency of residential roofs / ceilings and attic air distribution systems, if widely adopted, would result in large energy savings.

Objectives

  • Gain a fundamental understanding of the thermal performance of residential attics (including their interaction with attic ducts) and cathedral ceilings
  • Develop a handbook of practical technical data that describe ways to achieve cost-effective and energy-efficient attics and cathedral ceilings

Research
To allow laboratory studies of the thermal performance of residential attics, an attic test module simulating typical residential construction was built for use in the Large Scale Climate Simulator (LSCS). This module has been used for measuring the in-service performance of various types of attic and duct insulation under simulated winter and summer weather conditions. Results from the attic duct studies have helped to validate duct computer models which support the development of the ASHRAE 152P duct efficiency standard.

In addition to our work with attic ducts, we have been evaluating and analyzing the thermal performance of steel-framed attic systems. A test module to experimentally measure the thermal performance of a steel-framed attic was designed, constructed, and used to measure the heat loss through an attic with C-shaped steel framing. New ways to help us better understand the physics of heat, moisture, and air flow in residential attics with attic ducts were explored. To develop an attic energy efficiency rating system, the thermal performance of traditional wood frame attic systems serves as the baseline for comparison to innovative attic insulation strategies.