Rocket has covered the Station Rooftop table in sketches: awnings, white paint, a tree the size of a house.
"I designed everything," he says. "Now we build it all."
Raven reads the sketches one by one. "What do you notice about what the family actually has? And who is allowed on the roof?"
Rocket deflates a little. "Nobody our age. And we do not own a tree the size of a house."
Nova floats over the pile and lights two blank columns on a fresh page. "Engineers write these first," she says. "What must the plan do? What must it work within?"
"Criteria and constraints," Raven says. "Then we design."
Rocket picks up a clean sheet. "Okay. Smaller tree."
NGSS asks you to define a design problem's criteria and constraints with enough precision to ensure a successful solution.
Criteria are what the design must do. Constraints are the limits it must work within.
TeachEngineering, a University of Colorado program, calls the first design step Ask. What is the problem? Who is it for? What are the requirements and the limitations?
Here is this week's problem. Design a plan that keeps your home comfortable and safe on hot days and during storms, using what the family already has.
| Criteria (what the plan must do) | Constraints (what it must work within) |
|---|---|
| Give a shaded or cooler spot to rest on hot days | Household materials and what the family already owns |
| Name a safe indoor place for lightning, high wind and flooding | A grown-up handles anything on a roof, ladder, hot or sharp |
| Tell the family when a heat or storm alert is in effect | No new tree can be planted without the people who own the land |
| Include a way to monitor whether the plan is working | The plan must be ready in one week |
TeachEngineering lists the steps as Ask, Research, Imagine, Plan, Create, Test and Improve. The process is iterative, which means you repeat it.
You have already done Ask and Research. The EPA and National Weather Service pages this week were your research.
Imagine means brainstorming many ideas. Plan means picking the most promising one. Create means building a version, even a paper one.
Test means checking it against the criteria. Improve means redesigning and trying again.
Shade: the EPA found urban forests 3.0 degrees F cooler on average. A tree, an awning or a shade cloth over a window applies the same principle.
Light colors: a cool roof or cool wall reflects more sunlight. Any light-colored change to a roof or wall is a grown-up and landowner decision.
Plants: NASA notes plants take in carbon dioxide through photosynthesis. A pot of plants gives shade and uses a tiny bit of that gas.
Hot-day habits from the National Weather Service: slow down, wear lightweight and light-colored clothing, limit direct sun and drink plenty of water.
Storm rules from the National Weather Service: when you hear thunder, go inside a substantial building. Stay there 30 minutes after the last thunder.
In high wind, move to an interior room. In a flood, get to higher ground and never walk through moving water.
Community: the National Weather Service asks people to check on family and neighbors during heat warnings. A plan can include a phone list.
NGSS also asks you to design a method for monitoring and minimizing a human impact. Your station is the monitor.
Monitor: record the indoor temperature and the shade-spot temperature on hot days, before and after your plan starts.
Minimize: shade and light colors mean a building takes in less heat. The EPA notes that lowers the energy a cooling system needs.
Keep the log. If the shaded spot is not cooler, that is a test result, and the design goes back to Improve.
| Design review | True or false? |
|---|---|
| Criteria describe what a design must do. | ? |
| A student may change a roof color as part of the plan. | ? |
| The design process is repeated, not done once. | ? |
| The National Weather Service says to wait 30 minutes after the last thunder before going back outside. | ? |
| Monitoring means guessing whether the plan worked. | ? |
A real design, built on real data. Tomorrow you present it and write your Weather Lab report.