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Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

Simulation and Field Evaluation 

Support for ESTCP Dynamic 

Windows

Cooperative Research and 

Development Final Report

CRADA Number: CRD-12-492

NREL Technical Contact: Robert Guglielmetti

CRADA Report

NREL/TP-5500-63768

February 2015
NOTICE

The submitted manuscript has been offered by an employee of the Alliance for Sustainable Energy, LLC 

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Cover Photos: (left to right) photo by Pat Corkery, NREL 16416, photo from SunEdison, NREL 17423, photo by Pat Corkery, NREL 

16560, photo by Dennis Schroeder, NREL 17613, photo by Dean Armstrong, NREL 17436, photo by Pat Corkery, NREL 17721.

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Cooperative Research and Development Final Report

In accordance with Requirements set forth in Article XI.A(3) of the CRADA document, this document is 

the final CRADA report, including a list of Subject Inventions, to be forwarded to the Office of Science 

and Technical Information as part of the commitment to the public to demonstrate results of federally 

funded research.

Parties to the Agreement: Soladigm, Inc.

CRADA Number: CRD-12-492

CRADA Title: Simulation and Field Evaluation Support for ESTCP Dynamic Windows

Joint Work Statement Funding Table Showing DOE Commitment:

Estimated Costs NREL Shared Resources

Year 1 $ 252,331.00

Year 2 $ 97,328.00

TOTALS $ 349,659.00

Abstract of CRADA Work:

We will leverage new building performance and daylighting simulation tools to characterize the 

performance of a new electrochromic (EC) glazing as well as perform a field evaluation of the same 

product installed in a DoD facility. The in situ data will be used to validate and calibrate the simulation 

model, which will then be used to extrapolate the performance of the product across all US climate zones. 

The property as part of this agreement will be installed at MCAS Miramar, California.

Summary of Research Results:

The results of an annual energy simulation using the “combined rule” (planned control algorithm for 

commercial product) show that the View electrochromic glass resulted in a small increase in heating 

energy due to times when the building is in heating mode and the increased solar gain is beneficial. 

However, the EC glass also resulted in a decrease in cooling and fan energy that overcame the small 

heating energy increase, resulting in an annual whole-building energy savings of about 0.4% and an 

annual HVAC savings of approximately 0.6%.

The combined rule was also simulated in DOE Climate Zone 2A (representative city Houston, Texas) and 

5A (representative city Chicago, Illinois). The simulations were performed using EnergyPlus, EMS 

controllers for the windows, and TMY2 weather input data. The results showed that the EC glass resulted 

in a small increase in heating energy due to times when the building is in heating mode and the increased 

solar gain is beneficial. However, the EC glass also resulted in a decrease in cooling and fan energy that 

overcame the small heating energy increase, resulting in an annual whole-building energy savings of 

about 8.4% and an annual HVAC savings of 18.6%.

From the occupant perspective, the View Dynamic Glass retrofit on the in situ test facility was a neutral 

to positive change. The primary advantage proved to be increased satisfaction with access to views. The 
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primary disadvantage is general comfort with the darker tint. The latter issue was addressed through 

improved control algorithms in the second phase of the retrofit (May-September 2014).

The baseline/closeout survey and ongoing survey results support the following conclusions:

• Overall comfort with respect to interior lighting and thermal conditions was not significantly different 

before and after the retrofit.

• Satisfaction with views improved during the dynamic glass demonstration.

• The improved control algorithm that responds to exterior solar condition and interior sun penetration 

depth proved superior to timer-based control in terms of occupant reports of glare and overall 

satisfaction, but the glare simulations indicate some possible areas for improvement in the predictive 

control.

• Emphasis of occupant issue reporting shifted from a desire for increased views and decreased 

brightness in the baseline scenario to a focus on the following two issues in the post-retrofit scenario: 

• Lack of operable window control

• Decreased brightness to the point of “gloominess”.

• Recommendations for future View Dynamic Glass installations include:

• Seek retrofit opportunities where operable windows are not already in place and where 

the occupants are currently not benefitting from a view due to closed blinds

• Do not rely on dynamic glass to completely mitigate glare; pair with interior furniture 

layouts or other means to block midafternoon view of the sun

• Focus on afternoon glare issues on the west façade when setting up and adjusting control 

system

• Consider using view glass in only some areas in open and closed offices, maintaining 

some clear glass under shaded areas to prevent the gloomy appearance when all dynamic 

windows are tinted.

Subject Inventions Listing:

none

Report Date:

January 13, 2015

Responsible Technical Contact at Alliance/NREL:

Robert Guglielmetti (PI), NREL Commercial Buildings Research Group

robert.guglielmetti@nrel.gov

303.275.4319

This document contains NO confidential, protectable, or proprietary information.