LISA VAN PAY: These days, most of us pay attention to how we live.
We recycle, we try to use less water and electricity, we walk or bike or drive more efficient cars.
But a lot of us never really think about where we live
or work
or go to school.
I mean, a building is a building, right? Not necessarily.
Let's say you grow a bunch of plants on top of your building and they use sunlight and 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?
Well, is it worth the extra work?
It makes sense that plants on a roof would keep the building cooler, even if they only provide
a little shade. But what's really going on?
Where is the heat energy going? How does a green roof change the way a
building transfers heat?
JALENA SREBRIC: So that simple question led us onto a ten-year chase.
LISA VAN PAY: Jelena Srebric is an architectural engineer at Penn State University,
who studies energy flow in and around buildings. She and her students built their own green roof.
But with their model, they can control the weather to test what really happens when sun, rain, wind and
plants all work together on the roof of a building. But experiments don't always go as planned.
JELENA SREBRIC: Our first facility was so poorly designed that it caught accidentally on fire,
and we had to remove it. But it was a great learning experience.
LISA VAN PAY: Just because you're a talented engineer, doesn't mean you have a green thumb.
JELENA SREBRIC: Plants do die. They get sick, they need maintenance.
LISA VAN PAY: So they went to an expert.
LISA VAN PAY: Rob Berghage is a horticulturalist. He knows all about plants.
LISA VAN PAY: So Jelena mentioned that they actually killed a lot of different plants when they were
trying to figure out what would grow really well on a roof.
Can you explain to us a little bit about how you helped them choose the right
plants for a roof setting?
ROB BERGHAGE: Okay, so the plants we pick are adapted to growing in a harsh environment.
What we're really trying to achieve is something that is more or less in balance.
LISA VAN PAY: So you said fifty percent of the water that would normally have run off is actually taken up
by the plants and put back into the atmosphere? How do plants do that?
ROB BERGHAGE: It's called evapotransporation, and it's a normal process that all plants go through.
They take water up and they release it into the atmosphere.
LISA VAN PAY: Evapotransporation is one reason a green roof keeps a building cooler in the summer.
Instead of being absorbed by the building, heat from the sun is transferred to water in the plants and
soil, and released to the atmosphere. Okay, so we've got a lab.
The plants are alive and well. What's next?
TYLER MEEK: One of the major questions we wanted to answer was what is the best way to analyze our data,
or collect the data for the first place.
LISA VAN PAY: So you wanted to recreate some of the conditions that might be outdoors, in the lab,
and then try to measure the different variables?
TYLER MEEK: Right. Well, for a part of the experiment we needed numbers on how many leaves were actually in
this entire sample. So that was fun. We had to measure each and every leaf that was in that
probably 2.5-inch by 2.5-inch square. It was around 4,000 leaves? (Lisa: That big?)
Yeah, probably, yeah. (Lisa: 4,000 leaves.) Yeah, so I got my counting skills on that day.
LISA VAN PAY: So you take a small space and then use math to calculate about how many leaves are in a much
larger area. Beats counting to a million, I guess.
TYLER MEEK: It's a lot easier to start on a small scale than it is to just go gung-ho at a big project.
So if we understand a small scale, the plan is to move it to the bigger scale and just adjust what we're
finding. We're taking measurements. Some sensors take them every second, some take them
every minute. But we're always monitoring that.
LISA VAN PAY: So they take that data, everything they know about that small space, and identify all the
factors that affect energy flow. With all these numbers, they can start to figure out
how the energy moves within the system. Then another lab member, Paulo Tabares Velasco‚ uses math to take
what they learned from the lab, and turn it into a computer model to explain what happened in their
experiment, and predict what will happen in the real world.
So Paulo, we saw a lot of the different instrumentation you had in the lab and the
measurements you were taking. How did you take, then, the numbers and all the data you got there, and make
it into a model you might be able to use to predict what was happening outside?
PAULO TABARES VELASCO: That's something very interesting. First we do a statistical analysis of the
data. We take average of the data‚ and then we put it in to our model to make sure that our model is
predicting the right type of phenomenon. In other words, we compare what our model says,
with the actual data.
LISA VAN PAY: So you have to start simple and then make it more complex as you understand the simple
parts more? (Paulo: Yes, that's correct.)
Everybody knows it's cooler in the shade. But how do you prove it? What's different between a green room
and a regular room? It might not matter to a lot of people. All they know is that their buildings are
cooler, and they're saving money. But NSF funds people who want to know more.
Engineers like Jelena and Tyler and Paulo, who build models and invent ways to test their ideas.
Ideas that future architects and designers can use to make buildings that will change our world for the
better. And sometimes the best place to start is at the top.