Sure, the planting beds around your house can look pretty. But have you thought through how investing in plantings can reduce your home's energy needs? So many benefits come from shade trees - Areas with trees have reduced crime, increased property values, less road rage and traffic accidents, and people even drive slower on tree-lined streets! (Texas A&M did a study that showed people slowed down 3-15 mph along streets with trees.) If you want more fun trivia and data about how awesome trees are, this infographic from the US Department of Energy is great.
Besides all that good stuff, trees add beauty and bring the party outside – they make it more pleasant in the hot summer, that’s for sure. It turns out that a well-designed landscape can even reduce your energy bills. According to the Department of Energy, carefully positioned plantings can save up to 25% of an average household's energy costs. I know about a million things I'd like to spend that 25% on! I heard an excellent talk from Mark Dwyer of the Rotary Botanical Gardens in Janesville Wisconsin a few years ago, and it changed the way I design plantings around people’s houses. I'm thinking of the aesthetics, sure, but I'm also thinking of adding value and taking care of our earth while saving my clients some money. I’m excited to share some thoughts on landscape design for energy efficiency as the temps rise outside.
As we enter into the hottest months of the year, let's think about how plants can impact your wallet and your air conditioner. Shade provided by plants around your home can cool things down before your A/C even needs to come on – air temps around trees can be as much as 12 degrees F lower than out in the sun. Each appropriately-placed tree can save an average household over $50 every year. It will cost you about $400 to have a nursery plant a nice 2”caliper tree (that’s 2” diameter at the trunk, basically) at your house – so in 8 years, the tree has paid for itself, while still adding to your home’s value and providing habitat for all sorts of birds and other creatures. Seems like a no-brainer to me. So, how do you get started? What do you need to think about?
North, South, East & West
It's worth it to pay attention to the path the sunlight makes across your yard. Remember that "west is best" for energy efficiency - meaning, we want to shade western exposures above all else. You might think south-facing areas are the most impacted, but it turns out that more than 2 times more solar energy comes in the east and west windows than through the south windows. And, at least in the Heartland, any western exposure pretty much gets the stuffing knocked out of it all year long... cold blasting winds from the northwest in the winter, and hot blazing sun along the southwest in the summer. So shading the west side of your house is your first priority. Then hit up the east. It's good to actually leave the south-facing exposures open for solar gain in the winter.
What needs the shade?
Try to shade any impervious surface - that's roof, walls, driveway, walkway, patio, and anything else that attaches to your home on the west or east sides. A driveway can soak up the heat and remain hot for hours after the sun has gone down, and keep your car hot, too.
Next, take a look at your A/C - where is it? The A/C unit(s) should be shaded without affecting the air flow around it. I've noticed when working in new construction that many A/C units are attached on the north side of the house or in a shaded spot, but my century-old farmhouse has one on the west side - where it gets blazing hot afternoon sun all. summer. long. Since a shaded air conditioner can increase efficiency up to 40%, we are planting shrubs that will grow high enough to shade it for now - and eventually, we'll bury an electrical line so we can add a shade tree to shade that side of the house.
What should you plant?
To provide shade and reduce cooling costs, use large shade trees. With acres of developments all around our town, all planted with the same maple cultivar, I want to encourage some diversity. Maples are lovely trees, but there are many more shade trees out there to choose from.
Deciduous trees that will let sunshine in during the winter and shade the sun during the summer are a great choice. The branches will block the sun even in the winter (when you want it) so choose trees that have a more open canopy. Trees that leaf out on the later end of spring allow more warmth when you still need it. Kentucky coffeetree is one of those late leafer-outers that works great. Honey locusts also add dappled shade and have the bonus of not needing lots of raking in the fall- their leaflets are so tiny. Oaks and hickories are great choices too. The new hybrid elms like ’Accolade’ are gorgeous, and disease-resistant. Take a look at our underused shade tree guide and see if anything catches your eye.
Where should you plant?
I know we already said start on the western side, but it's good to think about how close to the house you get. You need to look at the mature size of whatever tree you choose. Don’t plant so close to the house that you’ll have to pay for expensive pruning later on. Siting a shade tree about 20 feet off the southwest corner of your house is a solid bet, but it depends on how many stories your house is and what the terrain is like. Each property is different, so give some careful thought to how the tree will grow before you get it in the ground.
Here's one more fun source for tree info - this brochure from the Morton Arboretum has tons of great data on why trees are so good:
I know at my own house I experience the impact that designing for energy efficiency has on how comfortable our house is. Take a look at your property one of these sweltering days and see if you have a spot to add a tree or put the shade in just the right place.