Moisture transport in attic spaces located in hot-humid climates

Current trends in residential-style construction have included techniques that utilize a non-vented attic space. A proposed advantage of this technique is that it could reduce the in-flow of moisture-laden air into attic spaces. However, little research has been done relating this aspect of construction to moisture transport in hot-humid climates.; A full-scale test facility was constructed to study many aspects of typical residential construction materials and techniques. The Building Products Test Facility is located on the University of Florida's Gainesville campus. This facility was used for the purposes of this investigation to provide insight into moisture transport phenomena related to attic spaces (vented, unvented, flat ceiling and cathedral) in a hot-humid climate.; A one dimensional moisture transport model was constructed and evaluated using boundary condition data obtained from a full-scale facility located in a hot-humid climate. This model was evaluated with global environmental conditions and homogeneous building materials. Moisture transport rates obtained with the model were then compared to rates obtained from actual installed conditions of common building materials and boundary conditions associated with early morning saturated dewpoint conditions. These rates were much higher than those obtained in the first case. In addition, comparisons of long-term moisture contents for roof sheathing were presented for measured and derived values.; Additional data were obtained that described a removal mechanism for the moisture transported through the roof structure. The mechanism was based on continuous soffit and ridge vent structures.; The results of this study show that moisture moves through a shingle roof boundary driven by nighttime cooling followed by solar heating. Furthermore, current attic venting practices provide a removal mechanism for this moisture flow.