Designs That Work

Hot Humid Climate

Introduction

A hot-humid climate is defined as a region that receives more than 20 inches of annual precipitation and where one or both of the following occur:

A 67°F (19.5°C) or higher wet bulb temperature for 3,000 or more hours during the warmest six consecutive months of the year; or
A 73°F (23°C) or higher wet bulb temperature for 1,500 or more hours during the warmest six consecutive months of the year.

The intense solar radiation in this climate imposes a large thermal load on the house that can increase cooling costs and affect comfort. The approach presented minimizes the impact of solar radiation on the building, its mechanical system, and its occupants.

Moisture is a significant problem in this climate, more so in those areas that receive more than 40 inches of annual precipitation. The ambient air has significant levels of moisture most of the year. Since air conditioning is installed in most new homes, cold surfaces are present on which condensation can occur. Controlling the infiltration of this moisture-laden air into the building enclosure and keeping moisture away from cold surfaces are major goals of design and construction.

Housing types vary greatly throughout all of the different climate zones, but nowhere is the contrast so great as in the Hot-Humid climate of the southern United States.

In many parts of Florida, block wall assemblies predominate, whereas wood frame is most commonly used in Texas. For this reason we have chosen three different building profiles that we think best represent the Hot-Humid climate:

The "Houston" - two-story, slab-on-grade, first floor brick veneer, second floor fiber cement lap siding, conditioned attic with asphalt shingle roof.
The "Maitland" - two-story, slab-on-grade, both floors stucco, conditioned attic, tile roof.
The "Orlando" - two-story, block stem wall with slab, SIPS walls, Cement board siding/brick veneer, vented unconditioned attic, metal roof.
The "Montgomery" - one-story, conditioned crawlspace, vinyl/aluminum lap siding, unconditioned attic, standing seam metal roof.

Additional information on construction methods and alternative designs are included in the Builder's Guide Hot-Humid Climates at Building Science Press and in the EEBA Water Management Guide at the EEBA Bookstore.

¹This definition is identical to the ASHRAE definition of warm-humid climates and is very closely aligned with a region where the monthly average outdoor temperature remains above 45°F (7°C) throughout the year.