To view the multimedia features on this page, you will need to download the latest version of Flash Player and/or enable JavaScript.

Video Closed Captions

(music)

Shana Weber:
Whenever you change anything in a system, it's really important

Shana Weber:
to get information about the condition of the system before

Shana Weber:
you changed it.

Shana Weber:
Dr. Eileen Zerba in the Princeton Environmental Institute has been

Shana Weber:
initiating a green roof study on one of our renovated residential

Shana Weber:
colleges. And, um, what's really neat

Shana Weber:
about that is that it took collaboration between academic

Shana Weber:
programs, curriculum, staff in the

Shana Weber:
facilities department and students to make this happen.

Shana Weber:
What we're going to get out of it is live information about the

Shana Weber:
performance of this green roof.

Shana Weber:
And it's set up so that some of the rooftops are green roofs,

Shana Weber:
some are not, and we'll compare between the two.

Eileen Zerba:
So, Butler College, one thing to put this in

Eileen Zerba:
perspective, is uphill from Carnegie Lake,

Eileen Zerba:
and a part of the sustainability initiative is to decrease the

Eileen Zerba:
flow into Carnegie Lake with sustainable practices like green

Eileen Zerba:
roofs or stream water restorations.

Eileen Zerba:
What I have in front of me now are two mock-ups of the green

Eileen Zerba:
roof. So what we want to know in the

Eileen Zerba:
mock-up model is to look at -- a five-by-five square is what

Eileen Zerba:
this is -- and the proportion of water

Eileen Zerba:
that is retained within the roof layers, the soil medium, in

Eileen Zerba:
comparison to a conventional roof.

Eileen Zerba:
So, the thermal advantage of a green roof has to do with the

Eileen Zerba:
surface itself. So, you have evaporation and

Eileen Zerba:
you have transpiration from the plants.

Eileen Zerba:
Plants have small holes in their leaves.

Eileen Zerba:
That's how they take on CO2.

Eileen Zerba:
They're called "stomata."

Eileen Zerba:
When those open, they evaporate water,

Eileen Zerba:
and that serves to cool the surface of the roof.

Eileen Zerba:
A conventional roof -- you can see the smaller layers -- these

Eileen Zerba:
temperatures can get 20 to 40 percent higher than the green

Eileen Zerba:
roof temperatures.

Eileen Zerba:
We've already got the data monitoring online, and we've seen

Eileen Zerba:
that just this summer.

Eileen Zerba:
The advantages of having this is not only to get empirical

Eileen Zerba:
values, we can mathematically model

Eileen Zerba:
this roof, and I think that will have a

Eileen Zerba:
lot of utility in terms of feeding the information back to

Eileen Zerba:
the University and retrofitting other buildings on campus.

Shana Weber:
We've all renewed our commitment to achieving results

Shana Weber:
that can be repeated elsewhere.

(music)