Short-Term Monitoring to Diagnose Comfort Problems in a Residence in Central Texas

Abstract

This paper presents results from a project to resolve comfort problems created by high indoor humidity in a 3,400 sq.ft. house in Bryan, Texas. The case study house had been certified by the local utility to meet their energy efficiency standards. However, the resident of the house complained that the house felt too humid although the desired temperature conditions were being maintained. Several HVAC contractors had been previously hired to resolve the problem without success. The field measurements undertaken to diagnose the problem are typical of those that could be undertaken by a house inspector and include an inspection of the construction of the house, short-term monitoring of temperature and humidity, blower door tests and whole-house pressurization tests. To perform the analysis both floors of the house were instrumented with portable data loggers and monitored for a period of two weeks to measure the temperature and relative humidity of the supply, return and ambient conditions. Analysis procedures applied to the house include comparing the measured data against the ASHRAE comfort zone (ASHRAE, 1997) which confirmed adequate zone temperatures with high humidity conditions, and inadequate supply air delivery temperatures for humidity removal. Combined results of the blower door tests and whole-house pressurization tests indicated a potential for leakage through the return air duct. After the recommendations were presented to the homeowner, a new contractor was hired and retrofits applied on the house (i.e., cleaning the cooling coils, enlarging the compressor and relining of the return duct). Measurements were then repeated to determine that the problem had been f ~ e d . This paper describes the case study residence, the measurements used to diagnose the problem, analysis methods, and presents results of the application of the analysis.