Landscaping should be part of your long-term plan for reducing heating and cooling costs; a well-crafted landscape is the first step for low-energy homes.
Vegetation provides shade and evapo-transpiration. Choose the right trees and the right shrubs, and position them in order to shade your windows, roof, walls and ground. Shading is the most cost-effective way to reduce unwanted solar heat gains and a key element for energy savings in many climates.
This page deals with landscaping for shade.
Plants release water vapor (evapo-transpiration) that reduces the air temperature around them.
Temperatures near the ground of shaded areas can be 25ºC/14ºC cooler than in non-shaded areas.
Begin your landscaping plan by drawing a sketch of your lot - to get a picture of it and to plan the improvements.
With the help of that sketch, study your home’s exposure to the sun and wind, and the impact of nearby buildings, fences, driveways, patios or water bodies, if they exist… They all can have a big impact on your home, by absorbing or blocking the sun's radiation.
Pay attention to the existing trees, hedges, shrubs, and their role, age and adequacy to your goals.
What you have determines your needs and what you should do.
Using trees to Shade the Windows and the Roof
You should have one or more wide trees, with a large crown, in the sunny side of your house. Plant the tree or trees, if you haven't them yet. They will provide maximum shade during the summer. The goal is to shade the windows and the roof (and on a lesser scale the walls), to reduce heat gains during the hot weather.
Instead of one or two large shade trees with wide branches, you may use a row of several narrow trees, planted close enough…
You should also plant shorter and broader trees – or high enough hedges – to the east and west, to intercept low-angle morning and afternoon sun…
Be careful with evergreen vegetation. Evergreens are good to deflect winds, or to channel them, and you may use to achieve such goals, but do not use them in moderate and cold climates for home shading. You need to maximize solar heat gains during the cold weather period, and evergreen trees and shrubs collides with it...
The types of trees
Trees vary in their height, shape and foliage density. Take it into account.
Prefer native and slow or relatively slow-growth shade trees. They will last longer and are more drought-resistant and stronger (they tend to have deeper roots, and are less prone to breakage).
Some trees can begin shading the windows during the first two years, but most slow-growth trees may require 5-10 years to provide shade to the roofs. That's their disadvantage...
Select the right trees, with manageable roots and adequate shapes. Shapes can be very different and you should find the right type of shape for your purposes: spreading, round-top, open, columnar, pyramidal, weeping… See, for details on this issue: Shade Trees and Shrubs for Landscaping.
Also consider the density of the foliage, quite variable with the species. Dense foliage plants can cut solar heat and winds by 60% or more, while low-dense foliage trees or shrubs may only reduce them by, say, 30%-50%.
Using hedges to get shade
Hedges are great for privacy or as windbreaks, but they can also provide shade to specific areas. Many shrubs can reach high heights, and many can be trimmed and shaped according to the needs, providing excellent spot shading.
Consider them – and isolated shrubs or groundcover plants - to shade the outside elements of HAVC equipment (it may increase their efficiency significantly) or to shade the pavement and the ground around your home.
Also use them – or trees – to shade driveways, sidewalks, patios and the ground in general. Shading them will decrease temperatures around your house and ultimately inside your home. A number of studies have shown that temperatures close to the ground can be reduced by half by using shade.
If you live in a hot climate, consider trees but also pergolas, trellises, ground cover plants and patios with vegetation. Pergolas, trellises and ground covers should be located closer to the home or to the ground... Patio areas with vegetation and water ponds can also be used to reduce the temperature around the house.
Shading the walls and the windows with vines
Vines offer a fast-acting option to cool walls and windows, but also patios, by creating cooler buffer zones. They can provide shade to walls and windows – and the foundations of the house – during their first growing season.
Be aware, anyway. Unless in some hot climates, avoid dense foliage greenery close to your home, or growing too close to walls. In cold and mixed climates they are also a source of moisture. If you live in a wet area, breezes should flow around your home, to keep the walls and the soil sufficiently dry.
trees and shrubs Placement
Before planting (or buying) a tree, a shrub or a bush, consider how large and how tall it will be in their mature stage. That's important to know the distance they should be planted from each other, or from your walls, windows and roofs. The specie, the shape and the mature size of the plants should be known ahead...
Large mature trees should be at a distance of 20 feet (6 meters) or more from the house, which means that young trees should be placed at a higher distance... An example: to shade a 20 ft one-story home, the mature trees should be at a distance of 15-20 feet (5-6 meters) from the house.
Taking into account your micro-climate
Remember that many plants will never thrive and be healthy in your climate and soil, and that is a reason to prefer native plants.Your microclimate – the climate affecting your home - determines the plants you should choose and the landscape improvements.
Never ever underestimate the impact of your climate in your landscaping project.
If you live in a cold or cool climate, you should design your landscape in order to get as much winter sun as possible, and consider planting dense windbreaks to protect your home from the winter winds.
If you live in a hot-dry climate, your project should consider ground-level breeze circulation (by planting adequate trees and hedges) and drought-resistant trees, able to shade your home and your yard.
If you live in a hot humid climate, you need trees with spreading crowns and branchless trunks, high enough not to block possible breezes; and you shouldn't plant dense hedges close to your home, to not block the breezes.
And you live in a temperate climate, trees in the sunny side of the house should be open and of deciduous type to allow the winter sun to hit and warm your windows and your home (and to shade it during the summer)…
Creating or Reducing Yard Lawns
Play and resting areas are important in any large yards; but they should not involve large lawns. You may have a beauty and agreeable landscape, and areas for kids to play or adults to relax, without large expanses of lawn. That's important for water savings.
More than half of the outdoor water consumption is used for watering lawns and gardens, and you should reduce it as much as possible, namely by reducing the area of your lawns.
Improving your landscape for shade and wind protection