ering the solar heat gain coefficient to reduce coolingwhile
maintainingthe visual transmission of the glass to capture
daylight savings.However, harnessing daylight in a build-
ing poses asignificanttechnicalchallenge because ofthe great
variability in daylight intensity.Achievinghigher energy
savings under these conditions requires looking beyond static
systemstodynamic systemsthatrespond tochanging climatic
or occupant conditions. By linking a dimmableelectric light-
ing system with daylighting controls to a fenestrationsystem
that can automatically modify the transmission of daylight,
we can get real-time control of the coolingand lightingen-
ergy balance while addressing glare and thermal comfort.

We investigated this dynamic systems concept using an au-
tomated blind system as a substitute for as yet unavailable
electrochromic "switchable" glazings, workingtowards an
occupant-responsivesystem that can be linked to the build-
ing HVAC system by a network of sensors and operated by
intelligent energy management controls.The position of the
blind system is coupled actively to variable external and in-
ternal conditions--the sun going behind a cloud or changing
functional needs in a room, for example. The system accom-
modatesoccupantpreferences for controlling view,glare,pri-
vacy,and tasklighting levels when the spaceis occupied,and
could switchtoaminimum energy consumptionmodewhen-
ever the occupant left the office.

Our performance evaluation can be found on page 20.

"Smart" electrochromic glazings now under developmentoffer the bestlong-term potential for dynamic control.The technologyconsists of a multilayered, thin-film
device that changes from a clear toan increasingly dark, colored statewhen low-
voltagecurrentis applied. By employingelectrochromic glazingsin a curtain wall, we
can dynamically alterdaylightlevels andvisual privacy in thespaceand control ther-
mal energy flows in the entire building envelope.Goodprogress is being made in R&D labs, butitwill beseveral years beforea specifiableproductemergesfromglass
companies.

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