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(Describer) In an animation, different colored icons include a car, a house, a model for hydrogen, and an arrow that looks like lightning. In another one, a woman connects cables. As she laughs and smiles, title: Green Revolution, with Lisa Van Pay PhD (Scientist).

(Describer) Other icons: house plus a leaf times gears turning equals question mark.

(Describer) Title: Green Roofs.

(Lisa Van Pay) Today we pay attention to how we live. We recycle, reduce our water and electricity use. We walk, bike, or drive more efficient cars. Many of us never think about where we live, work, or go to school. I mean, a building's a building, right? Not necessarily. Let's say you grow some plants atop your building, and they use sunlight, water and carbon dioxide, just like they're supposed to. Suddenly, you've decreased your energy bill, reduced air and water pollution, and made things a little greener. Places all over the world have tried it. So why aren't there more green roofs? Is it worth the extra work? It makes sense that rooftop plants keep the building cooler, even if only providing little shade. But what's really happening? Where's the heat energy going? How do green roofs change how a building transfers heat? That question led us onto a ten-year chase.

(Van Pay) Jelena Srebric is an architectural engineer at Penn State University studying energy flow in and around buildings. She and her students built their own green roof. But their model controls the weather, testing what happens when sun, rain, wind, and plants all work together on a building roof. But experiments don't always go as planned. Our first facility was so poorly designed that it caught accidentally on fire and we had to remove it. It was a great learning experience.

(Van Pay) Just because you're a talented engineer, doesn't mean you have a green thumb.

(Jelena Srebric) Plants die and get sick. They need maintenance.

(Van Pay) They went to an expert. Rob Berghage is a horticulturist. He knows all about plants.

(Describer) Title: learning from green experience. On a green roof...

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Jelena mentioned they killed many plants when they tried to figure out what grew well on a roof. Can you explain how you helped them choose the right plants for a roof setting? Plants we pick are adapted to growing in a harsh environment. We're trying to achieve something that is more or less in balance. You said fifty percent of the water that would have run off is absorbed by the plants and put back in the atmosphere? How do plants do that? It's evapotranspiration. It's a normal process for all plants. They take water and release it into the atmosphere.

(Van Pay) Evapotranspiration is why green roofs keep buildings cooler in summer. Instead of being absorbed by the building, the sun's heat is transferred to water in plants and soil and released to the atmosphere. We've got a lab, the plants are thriving. What's next?

(Describer) Title: Sometimes smaller is better. In the lab...

One of the major questions we wanted to answer was, "What's the best way to analyze or collect data?"

(Describer) Tyler Meek, Undergraduate Researcher:

So you wanted to recreate some of the outdoor conditions in the lab and try to measure the different variables? Right. Well, for part of the experiment,

(Describer) They stand at a table with green plants on it.

we needed numbers on how many leaves were actually in this entire sample. So that was fun. We had to measure every leaf in a 2.5 inch by 2.5 inch square. It was around 4,000 leaves. That big? Yeah, probably.

(Describer) Lisa and he hold their hands in a small circle.

Four thousand leaves. I got my counting skills on that there.

(Van Pay) You take a small space and then calculate how many leaves are in a larger area. Beats counting to a million. It's easier starting on a small scale than to go gung ho on a big project. If we understand a small scale, we move to a bigger scale and adjust our finding. Some sensors take measurements every second, some every minute, but we're always monitoring data.

(Van Pay) They take that data-- everything they know about that small space-- and identify all factors affecting energy flow. With these numbers, they can discover how the energy moves within the system. Then another lab member, Paulo Tabares Velasco, uses math to take lab results and turn it into a computer model to explain their experiment's conclusions and predict real world results.

(Describer) Lisa and Paulo sit by a green roof.

So Paulo, we saw a lot of the different instrumentation you had in the lab and the measurements taken. How did you take the numbers and data there and make it into a model you could use to predict what's happening outside?

(Paulo Tabares Velasco) That's very interesting. First, we do a statistical analysis. We take an average of that data and put it into our model to make sure

(Describer) Titles: Average: is the measure of the “middle” or “expected” value of the data set. To calculate an average, you add up all the values in the data set and then divide the sum by the number of values in the set.

our model predicts the right type of phenomena. Essentially, we compare what our model says with the actual data. So you start simple, and then increase complexity as you understand the simple parts.

(Velasco) That's correct.

(Van Pay) It's cooler in the shade. How do you prove it? What's different between green roofs and regular ones? It may not matter to many people. If their buildings are cooler, they're saving money. But NSF funds people who want to know more-- engineers like Jelena, Tyler, and Paulo, who build models, inventing ways to test ideas that future architects and designers can use to make buildings to change our world for the better. Sometimes, the best place to start is at the top.

(Describer) She stands on a wooden deck by the green roof.

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(Describer) Icons appear: house plus a leaf times gears turning equals a house with a leaf on it.

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(Describer) Titles: Produced by Lisa Van Pay, Maria Zacharias, Lisa-Joy Zgorski.