Building in a Hot-Humid Climate Zone

 

We build homes mainly to protect ourselves from the surroundings and the environment. Aside from extreme environmental events, remember that climate is part of the environment and the overarching system surrounding our homes. 

Understanding the climate system and the microclimate around your home should be one of the first steps in designing or retrofitting a home. 

Designing your home for the climate zone it is in has two key merits:

1. It helps maintain thermal comfort for occupants at all times with minimal active heating and cooling, resulting in significant energy savings.
2. It increases the house's resilience and durability for many years with minimal impact from mold, decay, and pests. It also ensures a healthy and safe environment and lowers maintenance bills.

 

 

Adapting to Climate Zones

About 50% of household energy in the U.S. is used for heating and cooling (space and water). This rate could be dramatically cut to almost zero in new construction and can be reduced significantly when retrofitting existing homes (depending on the scope and budget).

Data from recent years shows the acceleration of extreme climate events. We should expect significant changes in climate, some gradual (rising temperatures, droughts, sea-level rise) and some harsh and unexpected (extreme storms, precipitation, wildfires).

 

Designing a home for the current climate or based on historical data is a good start. That’s exactly what building codes help us achieve. However, assuming houses are built to last two to three generations, today’s designs should be able to meet future challenges while demonstrating consistent efficiency and durability throughout those years. To achieve true sustainability, we must adopt best practices that adhere to local climate zones, micro-climates, and predictable extreme events. 

This blog focuses on the basic need to adhere to your local climate zone. You shouldn’t design the same home in Arizona, Indiana, Texas, or Oregon. In each region, the trajectory of the sun, the direction of wind and rain, the ranges and fluctuations of temperatures and humidity, the amount of precipitation, snow, and ice, and the risks from wildfires, floods, and earthquakes differ. Therefore, we want to stress two key considerations: 

1. All the mentioned climate factors command a thoughtful approach to the design and the alignment of a home’s elements. It includes the elevation of the house, the slope of the roof, the size of the overhangs, and the location of rooms, windows, solar panels, and essential energy and water systems. A design that considers its climate zone will perform better while keeping the indoor ambiance cool in summer and warm in winter. It will also help your house dry quickly after water exposure and improve resistance to mold, decay, and pests, to name just a few benefits.
2. Consider the use of materials, assembly, and detailing. For example, a humid climate poses different challenges from a dry climate. The materials and their assembly can change a house from one that accumulates moisture and develops mold and decay, to a house that dries quickly and healthily performs for many years. 

Our blog is not a substitute for proper design and construction. Awareness, research, and hiring the right professionals will help you make the right choices and save you money and aggravation from day one. 

Which brings us to the prevailing question: what about the cost?

Cost is a leading factor in decision-making for any type of investment. There is a misconception that designing and building with sustainability, resilience, and efficiency in mind increases costs and tends to be above middle-of-the-road solutions. Check out our blog ROI (Return on Investment), which aims to demystify these conceptions.

When calculating your overall costs, you should consider the following in addition to the upfront expenses:

1. Rising prices of energy and water 
2. The rising cost of usage (operational costs) of energy as the climate becomes more extreme.
3. Losses and discomfort due to energy and water grid outages
4. Maintenance and repair costs of house elements due to climate impact

The difference between a truly resilient house and standard construction isn’t necessarily the cost. Many times it is awareness, asking the right questions, and implementing the knowledge by proper design and assembly, and by using adequate materials.

 

U.S Climate Zones

Building America, a program funded by the Department of Energy (DOE), provides ample information and data on design and building practices based on 8 different climate zones in the U.S. Its main aim is to help homeowners achieve the most energy-efficient homes. They also provide critical strategies for durability and adaptation to relevant climate zones, providing additional safety, comfort, and cost savings. To learn more about the difference between adaptation vs mitigation climate change, check out our blog about the two terms.

 

 

To determine the climate zone relevant to your property, check Building America Best Practices for a list of counties and climate zones. Or, you can use our tool by submitting your zip code and getting your relevant climate risks and your climate zone.

The climate zones defined by Building America are based on heating degree-days*, average temperatures**, and precipitation. The International Energy Conservation Code ( IECC) has a slightly different method for dividing and defining the U.S. climate zones. We rely on both resources. However, in this blog as in other sections of our website, we follow Building America’s climate zones.

Here is a summary of considerations in designing or building in the different climate zones in the U.S:

All content below is credited to Building America and the DOE, although we have refined and added some nuggets! Building America is a professional, reliable, and motivating source to follow for further information.

 

HOT-HUMID

A hot-humid climate is generally defined as a region that receives more than 20 inches (50 cm) of annual precipitation. Hot-humid climate states experience on average 40 to 70 inches of precipitation per year. Temperatures typically stay above freezing, with variations of approximately 30 degrees between the average summer and average winter temperatures (NOAA 2010).

Parts of the hot-humid climate zone are subject to frequent and intense rain and tropical storms, severe thunderstorms, tornadoes, and hail. Most of the region is at high risk for hurricanes and high winds. Large parts of the Southeast have been subject to flooding. 

The hot-humid climate zone is considered at low risk of earthquakes, volcanic eruptions, and landslides. Except for a small area on the southwest Alabama border, all of the hot-humid climates are at low to moderate risk for forest fires. 

 

States that are partially or entirely within the Hot-Humid climate zone:

• Texas
• South Oklahoma
• South Arkansas
• Louisiana
• South Mississippi
• South Alabama
• South Georgia
• South-East South Carolina
• South-East North Carolina

 

In this climate region you should mainly focus on the following hot climate architecture issues: 

• Moisture and precipitation management
• Moss
• Solar radiation
• Hurricanes
• Flooding
• Hail
• Lightning
• Pests

 

Moisture and Extreme Precipitation:

Probably the biggest challenge for maintaining a durable home is keeping its structure dry. Water in its various forms - liquid, solid (ice), vapor (moisture) - finds its way onto the exterior (rain, snow, ice), interior (floods, showering, cooking, breathing), and within the structure (leaks). Here are some key strategies to explore with your architect and contractors when designing or retrofitting a waterproof house:

• Most importantly: properly design and build your walls, roofs, and the foundation floor (crawl space/basement). A solid design will help drain water quickly and allow materials to dry. The design defines the layers you should use such as sidings, vapor, air, and water barriers, insulation, drywall, etc., the order by which you will lay them from the outside in, and the materials you use. The build is how well you attach them and run the detail so there are no cavities/leaks and thermal bridging. Check our blog on “water” for further details.
  
• Design the right size and angle of overhangs (eaves and gables) with a proper gutter and drain system that is capable of routing water from heavy storms away from the house.
• Landscaping is key. By digging a ditch or creating a small barrier/slope, and planting the right plants, you can help stop excess rainwater from running off and ending up damaging your property or overwhelming the local sewer system or water reservoirs. 
• Use door jambs that are designed for water and rot resistance.
• When installing windows use sill wrap, corner shields, and adhesive flashing tape to protect against water intrusion.
• Use cement backer board behind tubs, showers, and kitchens
• Install a dehumidifier - these systems suck wet air, cool it down, and condense the water back into a container or a pipe system and back into the world, preferably for good use and/or away from the house.
• Install a thermostat with humidity controls.
• The EPA still allows the use of paints containing mildewcide which potentially can repel bacteria but is also deemed toxic. Instead, look for VOC-free, or Low-VOC (some of the low-VOC become free after drying for a couple of weeks). 

 

Moss:

These small flowerless plants thrive on damp surfaces and in between cracks. Moss causes damage to roofs in various ways, mainly by:

• Not allowing your roof shingles to dry and applying constant moisture. This can rot and decay your roof and attract pests that thrive on damp materials.
• Spreading underneath shingles and creating cavities that will weaken the roof composite and become entry points for water to penetrate the roof structure and attic.
• Adding weight to the roof and deterring your house load and ability to withstand other hazards such as strong winds and earthquakes.
• Overall nuisance and reducing curb appeal.

Ways to prevent and handle Moss:

• Remove all shading elements and keep your roof fully exposed to sunlight.
• There are no “moss-resistant” shingles, but there are algae-resistant shingles. These inhibit the growth of algae which also helps slow the growth and spread of moss.
• If your shingles do not contain metals that oxidize and help kill the moss, you can install various metal strips (such as copper) along the ridge of an existing roof. Over time, rainwater will wash over the metal down the roof surface, creating almost the same effect as algae-resistant shingles.

 

Solar Radiation:

Simply put, solar radiation heats up the roof, walls, windows, and doors, and that energy then heats up the interior of the home. In order to have an energy-efficient home (that uses less energy) and resilient (that reduces the dependency on the energy grid and cooling systems, even during extreme heat waves), you should:

• Install a reflective roof and use light or reflective exterior wall colors.
• Install a radiant barrier in the attic.
• Install overhangs, covered porches, awnings, pergolas, or shade trees to minimize solar heat gain (avoid shading the roof due to moss).
• Place the air handler and ducts in a conditioned space or go ductless with mini-split heat pumps.
• Install high-performance, low-emissivity windows with low solar heat gain coefficient.
• Locate windows on the sides of the house that can catch coastal breezes.
• Create a tight thermal envelope and install a positive-pressure ventilation system.
• Use non-heat-producing Compact Fluorescent Light (CFL).
• Install ceiling fans and look for solar-powered fans (as backup).

 

Hurricanes

Damage from hurricanes varies depending on the category of the storm and the location of the house. The main risks from hurricanes are falling trees, poles, and flying debris, power outages from days to months, major flooding and excess rain, and loss of water supply. In all storm categories, there is a risk of damage or full removal of the roof, sidings, and other exterior elements, structural damage (walls, roof) to complete displacement or destruction of the house. 

Following are strategies to reduce potential damage In hurricane areas:

• Structural load design and assembly: designing walls to resist uplift using hurricane strapping and other metal fasteners that provide a continuous load path from foundation to roof.
• Anchoring walls properly to foundations.
• Designing roof geometries that are less prone to wind damage than gable roofs and installing continuous roof underlayment. 
• If you decide to go with a gable roof, properly plan the length and width of the gable overhang, strengthen gable ends, and outlooker attachments at gable ends. 
• Eave designs with extended fascia providing drip edge, and recessed soffit vents (Zoeller 2006).
• Adequately securing chimneys to the structure.
• Ensuring windows and doors meet appropriate design pressures (“impact windows and doors”) in addition to being protected from windborne debris. 
• As with windows and doors, there are hurricane-proof garage doors and tracks. Or reinforce an existing garage door using a garage door bracing kit.
• Safe-room / Shelter - according to the Federal Emergency Management Agency (FEMA), a safe room is a: “hardened structure specifically designed to meet the FEMA criteria and provide near-absolute protection in extreme weather events, including tornadoes and hurricanes. Near-absolute protection means that based on current knowledge of tornadoes and hurricanes, the occupants of a safe room built in accordance with FEMA guidance will have a very high probability of being protected from injury or death.”
• Consider steel-reinforced concrete walls.
• Use outswing doors.
• Use hurricane shutters.

Read further on strategies and products to enhance protection to your home from hurricanes in our blog. 

 

Flooding

Floods are the most common natural disaster in the U.S. We tend to think that floods happen mainly around coastlines and during hurricanes, but America is experiencing more frequent and devastating floods along creeks and rivers (“riverine floods”), lakes and ponds, and areas with inadequate drainage systems. In some cases, extreme precipitation events (“atmospheric rivers”), in-land tornados, and melting snow/ice can also cause floods in unexpected locations. 

In flood risk zones consider:

• Elevating your home above BFE (Base Flood Elevation level).
• Build slab-on-grade foundations and grade lots to drain away from the structure. In areas of likely coastal flooding build on concrete or pressure-treated piers.
• Adoption of Water Resistive Materials.
• Elevating Essential Infrastructure.
• Backing up Critical Systems.
• Install a generator-ready electrical service panel to run generator-powered shop hvacs, fans, and heaters to dry out the house and reduce water damage during post-storm recovery when electric power outages are common.
• Building Rain Gardens and Barrier Systems.
• Buy flood insurance.

Read further on strategies and products to enhance protection to your home from floods, in our blog. 

 

Hail

Hail is a form of precipitation consisting of solid ice that forms inside thunderstorm updrafts, sometimes building rapidly and without advanced warnings. Hail can damage homes and landscaping and can be deadly to people, livestock, and pets. 

In Hail risk zones consider the following:

 

• Harden your roof using impact-resistant shingles (Go for Class 3 or 4 UL2218 tested shingles)
• Protect windows and skylights with either permanent or temporary shutters.
• Cut trees around the house that may fall on the house during hail storms.
• Stowaway (indoors) all backyard and front yard furniture during the storm.

Read further on strategies and products to enhance protection to your home from hail, in our blog. 

Lightning

Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground. Lightning is one of the oldest observed natural phenomena on earth. It can be seen in heavy snowstorms, large hurricanes, and obviously, thunderstorms (with or without rain). 

 

 

 

 

 

 

 

 

Lightning protection systems do not prevent lightning from striking the structure, but rather intercept the lightning strike and provide a conductive path for the harmful electrical discharge to disperse safely into the ground. 

The installation of a complete lightning protection system includes several components. These components must be properly connected to each other in order to minimize the chances of any sparks or side flashes. In addition to the conductive and grounding elements, you need to further protect the house from electrical surges which might flow through the house piping and wiring networks putting these elements at risk as well as the appliances connected to them.

Components of a  lightning protection system:

• Air/strike terminals - these are basically lightning rods made of conductive materials (mainly copper) mounted on a structure (usually the roof) and intended to intercept the lightning strike.
• Cable conductors - route lightning current from the air/strike terminations at the top, to the grounding system.
• Grounding - there are various grounding solutions, all are effectively routing the electrical charge into the ground.
• Bonds - help interconnect the above lightning protection components and other electrical systems in the house to the grounding system. Their main job is to eliminate the opportunity for lightning to sideflash internally.
• Surge protectors - A surge protector or arrester is a device that protects electrical equipment from surge current events caused by lightning or other electrical events.
• Landscaping - lightning strikes may cause severe damage to trees. In addition, trees close to your property may either damage the structure after being struck, or the lightning may move from the tree to a conductive material in the structure. You can either avoid large trees in proximity to the structure or install lightning protection systems on the tree which may reduce such risks.

Read further on lightnings and homes in our blog. 

 

Pest Control:

Pests do not only pose a risk to your property but are also a threat to your family’s health. As with other hazards, prevention and being on the offense is a better strategy than being on the defense after pests have gained access or control over parts of your property.

The following methods are layers of protection that perform well together to reduce the threats from pests.

• Start with researching the threats in your location. You can learn about the main or common risks from local building codes and other local public resources, or use our tool. 
• Once you gain knowledge, either hire a professional or try to monitor and identify if you have any ongoing infestation. Either way, the main objective is to create an environment that rejects or eliminates pests;
• Use pest-proof building materials;
• Eliminate food sources, hiding areas (cracks), and other pest attractants;
• Use traps and other physical elimination devices; and only when necessary, select appropriate poisons for identified pests.
• Termites and carpenter ants are a threat to your home structure. The main strategies here are keeping your structure and the soil around it (about 18 inches) dry, and creating barriers to block easy access: 
  • Use the Termite Infestation Probability (TIP) maps to determine environmentally appropriate termite treatments, bait systems, and treated building materials for assemblies that are near soil or have ground contact.
  • Keep all wood (including siding, decking, and fencing that attaches to the house) from soil contact to minimize the presence of wet wood, which attracts carpenter ants. 
  • Use termite flashing and insulation products with termiticides or use fiberglass rigid insulation when insulating slab edge or exterior foundation walls
  • Provide roof drainage to carry water at least 3 feet beyond the building.
  • Apply decorative ground cover no more than 2 inches deep within 18 inches of the foundation.
  • Keep plantings at least 18 inches from the foundation with supporting irrigation directed away from the finished structure.
  • Specify and install an environmentally appropriate soil treatment and a material treatment (treated wood, termite blocks) for wood materials near grade.
• The CDC provides a good starting guide to help protect your home and the health of your family from various pests such as rats, flies, roaches, mosquitos, and fleas. 

 

Summary:

Climate is part of the environment and the overarching system that surrounds our homes. The main reason we build houses is to protect ourselves from weather and natural phenomena. 

 

Homes should be designed to adhere local climate zone characteristics and the microclimate around the home in order to meet the following objectives:

1. A resilient and durable home with minimal impact from mold, decay, and pests - ensuring a healthy and safe environment for occupants
2. Provide thermal comfort for house occupants at all times with minimal active heating and cooling, resulting in great energy savings and resilience (less dependency on the grid).
3. Provide an ongoing supply of good quality air and water.

 

Achieving these objectives requires suitable design, choice of materials, and proper construction. Building codes are a good starting point, however, they set the minimum requirements and don’t always cover all the best practices. Assuming houses are built to last 50 - 100 years, the goal should be to ensure their design can meet future challenges and demonstrate the same efficiency and durability over that time. 

 

To reach true future sustainability:

• Research and understand your climate zone.
• Study how to mitigate the risks it poses.
• Tap into information from local governments, communities and neighbors.
• Hire certified professionals that will help you achieve these goals in the most cost-effective way. 

 

Remember, working with the environment and adhering to the local climate zone is the necessary first step. The next step is being ready for future extreme events, those - “one-in a-century events” - which now occur more often. These require additional measures and planning.

 

KEEP COOL. BUILD RESILIENCE. EAMPACT.