There are three main things to consider when designing a garden that’s cool in the summer: Maximize shade, use light-colored materials and increase airflow. Look at your landscape now to understand where the hottest areas occur so that you can plan a garden that creates long-term shade for the summers to come.
Getting Started
So much of understanding the landscape begins with simple, sustained observation. You can figure out your yard’s microclimates on your own or hire a landscape pro. Identify where and how the heat is building in the landscape. Pay attention to surfaces that are retaining heat, such as paved areas and dark walls, and where the air feels stagnant.
Most important, identify the areas that receive full sun by tracking the sun across your yard and noting how many hours of sun each area receives. You can do this yourself by taking a photo every hour from the same vantage point and then reviewing the collection of photos. A smartphone may come in handy for this task. For more complex sites, with multiple buildings or steep terrain, a landscape architect or designer can combine aerial views and digital 3D models to track the sun and shadow cast in your space with more precision.
Maximize Shade
Permanent structures. Shade shields us from the direct heat of the sun. Shady areas will stay cooler throughout the day because the ground has not been heated up by the sun. This makes for more effective nighttime cooling, allowing for the area to stay cooler on average than nonshaded areas.
The best areas for permanent shade structures are where you want to create an outdoor room — like a patio or deck — or any space that you want to use for outdoor living. Think about an area adjacent to the pool, grill or potting shed, or a corner of the yard where you want to sit and read a book. These are the spaces that will benefit from sun protection in the summer so that you can maximize your enjoyment there, even on hot days.
Paving. Lighter-colored materials will not absorb as much heat as dark ones. Paving is one of the most important materials to consider for color because paving affects ambient air temperatures by either reflecting or retaining heat on the ground surface.
The amount of heat reflected is measured on the Solar Reflectivity Index. Cool materials stay cool by reflecting heat instead of absorbing it and have a high SRI. For example, newly poured black asphalt has an SRI of less than 5, while white Portland cement has an SRI of 86 to 100. Paving materials with high SRI include travertine, marble, white granite and light concrete.
Let Air Move
Air circulation helps our sweat evaporate, which helps us feel cooler. It’s key in humid climates where the air can feel stagnant. A wall or fence that allows for air passage keeps the garden cooler in hot climates. Metal screen fences, wood slat fences with spaces between or a vertical slat fence like the one pictured are all great solutions. Of course, an overhead fan also does wonders to circulate air and keep your skin feeling cool.
A broad and dense shade tree will provide the most effective cooling for a space when it is planted to block afternoon and late-day sun from hitting a specific area. For example, your deck may be on the west side of your home, exposed to the late-day sun. Plant a shade tree that will block this light and provide shade on the deck for the latter half of the day.