How do trees help keep a house cool?
A tree in the right place blocks the hot sun before it reaches your roof, walls and windows. Less sun on the house means less heat to push back out.
Why shade works
Sunlight carries energy. When sunlight hits a roof, a wall or a window, much of that energy turns into heat. The heat soaks into the house. Then your air conditioner has to work to move that heat back outside.
A tree’s leaves catch the sunlight first. The shadow under a tree is cooler because the sunlight never got there.
Trees have a second trick. Leaves let out tiny bits of water into the air. This is called transpiration (say it “tran-spuh-RAY-shun”). When that water dries into the air, it takes a little heat with it, so the air near trees feels cooler. It is the same drying trick a panting dog uses. See How Animals Keep Cool.
Right tree, right place
Tree experts say “right tree, right place.” That means picking a tree that fits the spot when it is all grown up, not just when it is little.
West side = afternoon hero
The hottest sun hits the west side of a house in the afternoon. A big shade tree on the west or southwest side blocks it.
Leaves that drop = winter sun
Trees that lose their leaves in fall give shade in summer and let warm sunshine through in winter.
Give it room
Big trees need to be planted far enough from the house that their branches and roots have space when they grow up.
Look up first
Tall trees never go under power lines. Short trees can.
Elbow room for the AC
The outdoor unit needs open air around it to let heat out. Bushes close to it can block that air.
Texas trees for Texas weather
Native trees like live oak, cedar elm and bur oak are used to Austin’s heat and dry spells.
Shadow-drawing planner
Where does shade fall around your home? Find out with chalk. You need a sunny day, sidewalk chalk and a grown-up.
- Pick a tree, a pole or a fence near your home that you can reach from the yard or sidewalk.
- In the morning, trace the edge of its shadow with chalk. Write “AM” in it.
- At lunch time, trace the shadow again. Write “NOON”.
- In the late afternoon, trace it one more time. Write “PM”.
- Look at your three shapes. Which way did the shadow move? When was it shortest?
- Which side of your house gets the most afternoon sun?
Four-season window watch
Pick one window. Look out of it once each season and write what you see.
| Season | Does the sun shine in? When? | What do the trees look like? |
|---|---|---|
| Fall | ||
| Winter | ||
| Spring | ||
| Summer |
From the same window, look at the outdoor unit if you can see it. Are plants or vines growing close around it? Tell a grown-up.
My Tree Buddy log
Choose one tree near your home, school or park to watch all year. Draw it and write about it on paper.
| Date | Leaves: green, changing or gone? | Animals I saw | How the shade felt |
|---|---|---|---|
What changed over the year?
Texas Arbor Day
Texas celebrates trees on Texas Arbor Day, the first Friday in November. Fall and winter are a good time to plant trees in Texas, because the weather is cooler and the roots can grow before summer comes back.
More to explore
Earth Helpers
Where old ACs go, and how families save energy.
🤝Help Austin
Ways kids and families help the city.
🗓️Season Calendar
November’s mission is a tree talk.
❄️How AC works
Why less sun means less work.
