One of the main reasons we build houses is to protect ourselves from the environment. Setting aside extreme environmental events, climate (which is part of the environment) is the overarching system that surrounds our homes. When designing or retrofitting a home, one of the first steps you should take is understanding the climate system as well as the microclimate around your home.
Two key merits of designing a home for the respective climate zone it’s in:
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 constructed homes, and can be significantly reduced in existing homes depending on the scope (and budget) of retrofitting projects.
Data from recent years shows the acceleration of extreme climate events, and that we will be experiencing significant changes in the climate, some subtle and growing slow (rising temperatures, droughts, sea-level rise) and some harsh and unexpected (extreme storms, precipitation, wildfires).
Designing a home based on historical data or for today’s climate is a good starting point and that’s what building codes help us achieve. However, assuming houses are built to last two to three generations (say 80 years) the goal should be to ensure those designs can meet the future challenges and demonstrate the same efficiency and durability throughout those years. To reach true sustainability, it is important to adopt best practices that adhere to local climate zones, micro-climates, and predictable extreme events.
Setting aside extreme events, this blog focuses on the basic need of adhering to your local climate zone. You cannot design the same home in Arizona and 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, the risks from wildfires, floods, and earthquakes differ. Therefore, we want to convey two key takeaways:
What about the cost? The difference between a true resilient house and standard construction isn’t necessarily the cost. Many times the difference is being aware, asking the right questions, choosing the right professionals and then properly designing and assembling the house, using the right materials.
U.S Climate Zones
“Building America”, a program funded by the Department of Energy (DOE), has divided the U.S into 8 climate zones and provides ample information and data on design and building practices based on those climate zones. Their main aim is to help homeowners achieve the most energy-efficient homes, but they also provide key strategies for durability and adaptation to the relevant climate zone, providing further safety, comfort, and cost savings.
To determine the climate zone relevant to your property, check the Building America Best Practices Volume 7.3 Guide to Determining Climate Regions by County (DOE 2015) for a list of counties and climate zones.
All content below is credited to Building America and the DOE, although we have refined and added some nuggets! Still, Building America is a great professional, reliable and motivating source to follow.
HOT-HUMID
A hot-humid climate is generally defined as a region that receives more than 20 inches (50 cm) of annual precipitation and where one or both of the following occur:
States that are partially or entirely within the Hot-Humid climate zone:
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.
In this climate region you should mainly focus on:
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:
Moss
These small flowerless plants thrive on damp surfaces and in between cracks. Moss causes damage to roofs in various ways, mainly by:
Ways to prevent and deal with Moss:
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 (use less energy) and resilient (reduce the dependency on the energy grid and cooling systems, even during extreme heat waves), you should:
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 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. In hurricane areas:
Flooding
Floods are the most common natural disaster in the United States. 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:
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:
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, in 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 (see components below) includes several components. These components must be properly connected to each other in order to minimize the chances for any sparks or side flashes. In addition to the conductive and grounding elements, you need to further protect the house from electrical surge which might flow through the house piping and wiring networks putting these elements at risk as well as the appliances connected to them.
Wildfires in risk zones
Wildfires pose a risk for the lives of people who live near those ecosystems and their homes. Moisture is one of the main factors that determine wildfires frequency and since the changing climate in recent years brings dryer winters, the consequences of wildfires are becoming more devastating, and the fire season becomes longer. In fire risk zones consider:
Pest control
Pests do not only risk your property, they 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 defence 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.
Summary
Climate (which is part of the environment) is the overarching system that surrounds our homes and one of the main reasons we build houses - to protect ourselves from weather and natural phenomena. The main impacts of the climate on our homes are - water (in all its forms), air (quality, wind, moisture carrier), and thermal (hot and cold)
Setting aside extreme events, homes should be designed in a way that adheres to the local climate zone characteristics and the microclimate around the home in order to meet the following objectives:
Achieving these objectives require the right 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 such time.
To reach true future sustainability:
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.
References:
https://www.eia.gov/energyexplained/use-of-energy/homes.php
https://www.ncdc.noaa.gov/billions/
https://www.energy.gov/sites/default/files/2015/10/f27/ba_climate_region_guide_7.3.pdf
https://www.energy.gov/sites/prod/files/2013/11/f5/40percent_hot_humid.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/40percent_mixed_humid.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/18899.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/cold_climate_guide_40percent.pdf
https://www.energy.gov/sites/default/files/2013/11/f5/marine_40_guide.pdf
Footnotes:
* Wet Bulb Temperatures
Dry bulb and wet bulb temperature: The temperature of air measured with a thermometer whose sensing element is dry is known as “dry bulb temperature.” If a thermometer’s sensing element is surrounded by a wet wick over which air is blown, the sensor is evaporatively cooled to its “wet bulb” temperature. When the relative humidity is at 100%, there is no difference between dry and wet bulb temperatures, but as the relative humidity of the air drops, so does the wet-bulb temperature with respect to dry bulb temperature. In climates such as those in the Southwest, where humidity is routinely quite low, the differences are substantial. For example, at 10 percent relative humidity and a dry bulb temperature of 90ºF, the wet-bulb temperature is 58ºF, a 32-degree difference. This is often called the “depression” of wet bulb below dry bulb.
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