How does a green roof, or roof covered by plants, affect the temperature of the inside and outside of a building? Learners design and build houses to find out the answer. In doing so, they need to consider experimental design and controlling variables as well as cost constraints on building materials. Learners need to calculate surface area to calculate cost of materials. Learners then design an experiment and collect data to determine the effect of a green roof on a building. Time estimate for activity can be spread across multiple meetings.