Friday, April 13, 2012

Energy-Efficient Landscaping, Strategic Design for Warmth

house with landscaping Energy Efficient Landscaping, Strategic Design for Warmth

Part 2: Using landscaping to stay warm over the winter.

When most people think of putting in landscaping, they probably think more in terms of how it can make a home cooler over the summer, which is what I discussed in an earlier post. But people probably don’t think quite as much about how to strategically design landscaping to stay warmer during the winter to reduce energy costs and lower your electricity bills.
Landscaping as a Windbreak
As residents of cold regions know all too well, wind chill can not only drop the temperature outside your home, but can also blow in through the cracks outside your home and drive up heating costs substantially.
So the name of the game with winter weather landscaping is to use it as a windbreak. If properly designed and implemented during the summer months, landscaping can help reduce and redirect wind and modify the micro-climate in the sheltered area.
Proper landscaping windbreak design needs to take several factors into consideration:
  • Windbreak height. This is probably the most important factor for determining the size of your sheltered area.  Depending on the density of your windbreak (more on that shortly), wind speed can be reduced on the windward side by a distance of two to five times the height of the windbreak.  But it’s the leeward (downwind) side that you really care about, and that’s where the most dramatic impact can be seen: wind speed can be reduced by a distance of up to 30 times the height. For the sake of comparison, a 10-foot windbreak can reduce winds on the leeward side by 250 feet or more.
  • Windbreak density. This plays a major factor in determining the amount of wind speed reduction.  Obviously a low-density windbreak doesn’t do as much to reduce wind speed, but a high-density windbreak isn’t necessarily helpful either: the low pressure that results on the leeward side pulls air coming over the windbreak downward, which raises turbulence and reduces downwind protection.
  • Location and construction. Depending on the location of your home and surrounding structures or topography, you will need to put together the right combination of trees and shrubs in the right places to achieve an optimal windbreak.
    • One or more rows of trees and shrubs with low crowns (leaves and branches) to block wind close to the ground
    • Plant low shrubs on the windward side of a windbreak to block snow from blowing next to the home.
    Those are the tips for utilizing landscaping as a windbreak for cold weather.  However, sharp-eyed readers will recognize a conundrum: What if you need landscaping to lower your temperatures over the summer and help keep back the cold during the winter?  Obviously there’s no easy answer here, since every home is a bit different.  However, consider the following:
    • Plant deciduous trees, which shed their leaves during the winter.  Depending on the type of tree, you should have a good thick canopy for summertime shade, and when it loses its leaves during the winter, enough sunlight should come through to help heat things up over the winter.
    • Combine trees with fences where possible.  Trees combined with a fence or wall can help deflect wind over the tops of homes during the winter.  Depending on its location, it can still help provide some shade during the summer.
    • Plant bushes and shrubs close to your house.  This offers the best of both: as detailed in the previous post, it will help keep the ground cooler during the summer, and can help block wind and snow during the winter.  (The same goes for crawling vines over a latticework or trellis outside a wall.
    Again, there is no straightforward answer, since every situation is different.  And of course, there are plenty of other variables to consider, such as cost, aesthetics and effort involved in planting, among others.  Besides, if you’re looking to reduce your electricity costs, there are other projects you can consider, such as installing sunshades.  But if you’re already looking to do some landscaping on your house, proper design and application can both make your home prettier and more comfortable in all seasons.

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