Energy efficiency

Your landscaping can add to the energy efficiency of your house

If you think that energy efficiency in the home is just a question of construction materials, you're wrong. There many ways that your landscaping can make your house cooler in summer and warmer in winter. What's more, it will not only make a difference in your house, but around it as well.
In the summer, trees and bushes can absorb and dissipate heat from the sun very fast. Hard materials like bricks, on the other hand, absorb and retain heat, making your house and ultimately your neighborhood warmer through the day, but also through the night. In the winter, heat from the sun can provide some of the energy needed to heat your home, bringing your energy costs down and reducing the quantity of oil, gas and electricity your house, neighborhood, city or municipality, and ultimately your whole nation consumes.

The main idea is quite simple:

when its cold outside, let the heat in and keep the cold out
when its hot outside, keep the heat out and let cooler breezes in.

To try to attain better energy efficiency, there are two very important factors to consider: the prevailing winds and the sun's apparent path in the sky both in summer and winter. You may be surprised how much the winds can change as the seasons change. Obviously, the sun will not change course, but people living farther north in the Northern Hemisphere and people living farther south in the Southern Hemisphere, do see a big difference between summer and winter sun.

During the cold season

To keep the cold out, use vegetation to break the cold season's prevailing winds.
To let the heat in, make sure that as much sunlight as possible can reach your windows and penetrate inside your house.

During the warm season

To keep the heat out, use vegetation as a sort of parasol, to keep the walls and roof cool and prevent the sun's rays from shining through your windows.
To let cool breezes in, use vegetation that can block the sun while letting some airflow through.

Energy efficiency is a question of balance. Blocking the sun and wind when needed and letting them through at other times.

Deciduous trees and bushes (ones that shed their leaves)

They are great in summer, because they block the sun, thus keeping your walls and roof cooler, as well as preventing the sun's rays from heating the inside of your house.
They are great in winter, because they let the sun shine through, thus letting the energy form the sun heat your walls and roof, as well as the air inside your house.
In winter though, they don't provide a lot of protection against cold winds. Conifers are better at slowing down cold winter winds.
In summer, since they block the sun and slow down the wind, they can make your house and yard a bit more dark and damp.

Conifers

They are great in winter, because they provide protection against cold winds. Not to mention that they can also provide protection to birds on those cold winter days.
They are not so great in summer, because their shapes don't block as much sun as deciduous trees and bushes, so they don't keep your walls and roof as cool, and they let more of the sun's rays inside of your house.
In summer, since they don't block as much sun and they don't slow down the wind as much as deciduous tress and bushes, they can make your house and yard a bit less dark and damp.

Vines

Like deciduous trees, they are good in summer, because they block the sun and thus keep your walls cooler. On the other hand, they will do nothing for your roof and, since you will probably trim them so they don't grow in your windows, they won't prevent the sun's rays from heating the inside of your house.
In the summer, they may protect your walls from the rain.
Unlike deciduous trees, they won't make your yard darker and damper, but like them, they may prevent the sun and wind from drying up your walls.
On this subject, some people argue that vines are bad because they damage the masonry. Most of the masons to whom we have posed this question did not agree with this. What they said was that the vines themselves are absolutely incapable of damaging the masonry, but that the fact that they may keep the walls damper longer, may damage the masonry when the temperature dips below zero and the moisture turns into ice crystals. But then ice crystals usually form in winter and in winter there are no more leaves in the trees and vines.
So their conclusion was that both trees and vines can block the sun and wind in summer and thus keep house walls cooler and damper, but that this has no real negative impact on the masonry.

Fences

A well placed fence may be the best wind breaker. Bear in mind that all trees need light and that most of them need a lot of direct sunlight, so don't install your fence in a location where it will block the sun and make your trees dwindle.

Where you live on the globe, as well as the position of your house relative to the prevailing winds and the sun, both have a big impact on the energy efficiency of your house. In order to find the best energy efficiency solution for your situation, you will have to mix and match multiple strategies. There is no "one solution" and no "one perfect energy saving tree". It may be that a vine here, a couple of deciduous trees here and a couple of conifers there are best for you, while it may be just deciduous trees and bushes for your neighbor.

In the illustration to the right, a red arrow is used to represent the sun's rays shining on the house on a winter afternoon. The deciduous trees in front of the windows let most of the sun's energy shine through.
The blue arrow is used to represent the winter's prevailing cold winds. Conifers and fences break the force of these winds, protecting the walls and windows.

If you want to go farther, you could also consider changing your roof into a green roof. Note that green roofs should be left to the experts. That's unless you want to see your roof top garden land in your living room.

All these energy efficiency solutions, with the exception of the green roofs, are sure to be cost efficient. If they are properly applied, they will soon translate into energy savings that will more than cover the money spent on the landscaping.

Also bear in mind that your house is filled with energy saving ideas that are just waiting to be discovered. Visit Going-Green-Challenge.com for Simple ways to Save Energy.

Links

Energy-efficient landscaping, from Wikipedia, the free encyclopedia
Landscaping and Your Regional Climate (USA)
Gardening and Landscaping for Energy Efficiency, from Toronto Hydro, Canada
Landscaping for Energy Efficiency, from the US Dept. of Energy