How to Design a New Home for a Hot Climate

Building a new home in a warm, humid climate, like south Florida, or in a hot and dry climate, like Arizona or New Mexico, can be a lot different than building a home in a cold climate.

Selecting the wrong design, accepting not-up-to-par construction, or opting for the wrong products (or builder) can result in an uncomfortable home that’s too warm or too moist, that contributes to mold and mildew, and that leads to high energy bills.

As with cold climate home building, warm climate home owners need to have a basic understanding of how heat, air and moisture travel within the walls of a home, how insulation and windows are rated, as well as passive energy designs, and energy efficient products and HVAC systems is key. Your home builder can answer your questions. Just as with cold weather homes, warm weather homes need to be tightly sealed, have adequate insulation for the location, use energy efficient windows and doors, and provide effective ventilation and humidity control.

Here are some tips for ensuring your new home will be well suited for hot weather:

Reduce Heat and Moisture

In hot climates, reducing heat and moisture gains is crucial. Control heat-gain with high performance windows, ceiling insulation, LED lighting and energy efficient appliances. Air and moisture barriers and quality flashing are keys to slow thermal convection, reduce air leakage, and prevent moisture in walls that can cause mold and mildew. Materials should have low emissivity to limit the absorption of radiant heat. Heat-reflective foil insulation and radiant barrier roof sheathing can help.

Walls should have low-conductivity and a high R-value. Look for tightly sealed windows with low SHGC ratings. Double-paned, low-E windows (perhaps with some tinting) are a good option. North or south facing windows are best. Light tubes provide less heat gain than skylights. Concrete, brick, and tile offer thermal mass that absorbs heat during the day and released it at night. Ceramic tile floors are cooler than carpeting.

Select a light colored roof with high solar reflectance and high emissivity. See that adequate-sized roof overhangs will shade windows (or plan on landscaping that will do this). A hipped roof with wide overhangs works well.

Is there adequate ceiling insulation? Does the plan call for continuous insulation? Rigid foam board applied to the outside walls works well. Will the slab edge be insulated? Is there a continuous layer of foam board insulation under the slab? Are ceiling can lights insulated? Do A/C ducts run in conditioned space and are they well sealed?

Compact house forms, rather than sprawling, multi-wing designs work best in hot locales. Home designs with shaded porches, wrap around porches or plans with courtyards that create a shaded open area within the building are ideal.

Ventilation Key

Ventilation is vital to capitalize on air flow throughout the house. An open floor plan allows natural ventilation. Roof vents, louvered attic vents, and ceiling fans help. Don’t forget bathroom fans/vents to exhaust moisture. You might also consider an energy recovery ventilation (ERV) system or an air-to-air heat pump. Whole house ventilation systems can remove moisture vapor from the home.

The Building Science Corporation (BSC) in Westford, MA, warns that “most houses in hot, humid climates are over ventilated.”

Humid attic air migrating into living spaces, operation of the HVAC system with external A/C equipment, HVAC ducts leaking into unconditioned pace, leakage of the building envelope, and unbalanced air flow, all can increase the home’s air change rate and humidity level. If these issues are not considered in the home’s construction, according to BSC, adding excessive outdoor air via ventilation can lead to serious moisture problems.

Addressing these issues, notes BSC, may require additional framework in the wall cavity, tightly sealed ductwork, sealed air handlers, and room-to-room transfer vents to reduce air flow rates. In addition, make sure that your new home has a correctly sized and variable speed A/C system. Finally, you should probably add supplemental dehumidification.

In warm, humid areas, you want to keep the moisture out and, to save energy, prevent cooled-conditioned air from leaking out. As in cold climate homes, this requires an air tight exterior envelope, sealed gaps and adequate insulation. It’s important that A/C ducts run inside conditioned space.

Check to see that the home has high performance, double paned, low-E windows. Orient the home so that the main windows face away from the sun. Add drapes, blinds, shades and/or landscaping to block sunlight. Select a light colored roof to reflect sun light and insist on proper window and roof flashing.

As in any climate, ask for energy efficient products, including high performance A/C equipment and ENERGY STAR® rated appliances. Efficient appliances and LED or fluorescent lights also produce less heat. Ask your builder about the thermal mass benefits of thick concrete, brick or even adobe walls.