How to use plants to cool your house: planting for energy efficiency

Wise planting can help shade a house in summer.

I have a south facing wall of the house. This wall and small yard area get wickedly hot under the summer desert sun. My backyard also has a west facing house wall which runs along my entire backyard. This also has sun beating on it for many hours every day. The heat, of course, moves into the house through the wall and the roof in spite of the insulation.

I need to have some kind of cover along those baking expanses- either with a deciduous tree, or with some sort of vine which I would grow up a trellis beside the house. My neighbor has a young tree which will eventually shade the southwest part of my house, but not for at least five years. So, I decided I would grow vines up the house, but not against the house. Some of the most popular vines like ivy or trumpet vine often damage a house in the process of growing along a wall.

The idea is to have plants that make shade during the hot summer and keep the house cool but then lose their leaves so the less intense winter sun can warm the walls. Here are links to examples of the information that is often available on electricity supplier’s websites about using plants for shade.

Landscaping for Energy Efficiency

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Grapes grown on a trellis. Image from Vicki's Garden Tips.

I will put up trellises that will be self-supporting, so the vines won’t touch the house. When I was younger, I saw the Amana colonies in the Midwest. These were early religious settlements that were clever and efficient with their farming practices. They put grape trellises growing parallel but not touching the walls of may of their houses. This allowed for shade against the house, without damaging the house, and it grew a crop in an otherwise unused space. They could squeeze between the house and the arbor to harvest the grapes.

I will do something similar on the south-facing side of my house. Because of the wine industry, there is a ton of research about different grape varieties, their cold-hardiness and fruiting. The Colorado State extension has findings on successful varieties for the HOT summer/cold winter successes from an agricultural research station in Colorado. California grape research is all over the Internet too, so there is no lack of info on growing grapes.

I will need varieties that can take the heat of a southern exposure and I will probably put annual vines there, too, until the grapes plants are larger. I might put morning glories, or a climbing bean or maybe a small fruited vine in the squash family like gourds or a vining cucumber. Bush cucumbers are more common, so I will need to look specifically for a variety that suggests growing on a trellis or fence. If any of these annual vines grow up from seed in the hot sun, they will be fine as long as I keep them well watered.

Along the west side, I've decided to put vines on a temporary trellis which I can tear down. So what comes to mind for my west wall is hops –yea, the beer ingredient. It’s very easy to find in nurseries these days since home beer brewing is becoming more popular. It is a fast-growing, wiry perennial vine that is a bit prickly and will twine around anything.

Hops fruit on the vine. Picture from Logee's.

I grew hops at my old house and know that they are tough and will cover my new trellis in a short time. However I don't like the smell of the leaves when you touch them, though many folks do (I don’t like a beer that is too hoppy, either), so cutting down the vines is always a job I dislike.

At the old house, it would cover the back fence every summer in about 3 to 4 weeks. I like that speed – much faster than most vining plants. It is pretty in a leafy way, but its flower is small and inconspicuous so don’t plan on anything but soft lime to mid-green. It does make an interesting fruit, which is the part that is used in beer making, and these persist on the plant through mid-winter. During winter, the whole plant turns a soft red-brown, and provides some winter interest.

My solution is to plant them so that they are climbing disposable trellises and to put them in a place where I won’t brush against them.

I will grow them up disposable plastic fencing. You can find this fencing at most big box stores or garden shops. The kind I am familiar with is gray or black, has ½ - 1 inch squares and is sold as bird protection cover for cherry trees,  or for temporary fencing. It is about 3 feet wide, very lightweight and not very expensive so I won't feel bad about taking it down and throwing it away.

Along the west side of my house: These trellises are disposable fencing, held down with T-posts and attached at the top to hooks which are attached to the house. When winter comes, I will disconnect them from the posts and the unhook them from above and toss the whole thing in the trash. After a summer of hot sun, the fencing will be damaged, so I can justify my non-thrifty disposal.

The trellis along the southern wall of my house with the dormant grapes. The trellis is a ranch fence panel and electrical conduit pipe. It is attached to the house at the top.

Hops die to the ground every winter and re-sprout with enthusiasm in the late spring when the soil warms up. They can be aggressive, if allowed to spread unchecked along the ground.

I have to guide the first growing sprouts so that they grow where I want them to go. But after that I can leave it on its own, and just beat it back in several years when its underground growth takes it to places in my garden where I don’t want it. If you plants hops, be aware of this spreading, because they shouldn’t be ignored if you garden in a small space.

I will leave the vines up for visual interest until winter when the sun drops low. And then, I can just clip the dead stems off at the ground, rip off the temporary fencing and throw the entire mess away.

These are the grapes in early June. I have planted gourds next to them because it will obviously going to be a number of years before the grapes grow enough to shade the house. The corn poppies are an early blooming annual that reseed themselves with abandon and which die and are removed by July.

Here are the hops in just over a month in mid-June, covering the fencing. I took the temperature against the house in late afternoon in the shade – 90 degrees, less than the air temperature at that moment. The side of the house in the sun was 109 degrees. Notice the shade on the hops on the right. This is shade made by my apricot tree, which in a few years will cast enough shade to keep the backyard much cooler – and may give me some fruit as a bonus.

Hops will spread easily, and new babies will sprout up nearby. If you don’t want too many hops plants, dig these new babies early. They are attached underground to the main plants so use a sharp shovel to cut them apart about halfway between the 2 plants. They transplant well, so you can pass them onto a friend.