This past August, tinted window films were applied to the glass of the Ralph S. O’Connor Recreation Center and the Glass Pavilion. Similar films were applied to the Bloomberg School of Public Health (BSPH) Wolfe Street Building in 2013. These films selectively filter the sun’s light, allowing visible light to pass unimpeded into the space, while reflecting and absorbing infrared light which would heat the interior of the buildings.
The project was a joint effort of the Office of Sustainability and the Sustainable Hopkins Infrastructure Program (SHIP), a student group which advocates for sustainable infrastructure development.
The installation of the films was a result of complaints by building occupants that the buildings’ air conditioning systems were unable to keep up with demand. The problem was especially pronounced in BSPH, where offices sit on the outside of the building with large, east-facing plate glass windows.
“The sun comes up in the morning, shines deep into the office, heats up everything, and it takes the rest of the day for the air conditioning to catch up,” Ed Kirk, the University energy manager, said. Kirk is part of both the Office of Sustainability and the Facilities and Real Estate Department.
The air conditioning in BSPH had to supply air at 52 degrees Fahrenheit, outside of the standard 55 to 60 degree range. The system in the Rec Center was unable to maintain a target temperature of 72 to 74 degrees, and the temperature inside the building’s fitness center, weight room and offices would reach 78 degrees.
“Often when things don’t work well… we just throw more energy at it,” Kirk said. “That’s what we’re trying to avoid; let’s fix the problem that’s causing the overheating or the overcooling.”
Individual films were designed for each building; 3M manufactured the films for BSPH, and Kodak for Homewood. The films at BSPH were installed by ATD Solar and the films at Homewood by Absolute Perfection Window Tinting & Graphics. However, even within brands, different films were designed for each building to optimize results.
“It’s not a one size fits all solution: Window films are a good opportunity to save energy, but even within that there’s specifications that can make it an even better solution for any one building,” Ashley Pennington, the senior program coordinator for the Office of Sustainability said.
Window films have not only kept both buildings within their desired temperature range, but also allowed the buildings to step down from peak air conditioning, saving energy and money.
In addition to this success, the Office of Sustainability has already gotten positive feedback. “People have already said, ‘Hey, how do I get window film in my office?’” Kirk said.
The total cost of applying the films was $146,956. Half of this was covered by a rebate from Baltimore Gas & Electric (BGE), leaving a cost to Hopkins of $73,478. The films will save an estimated $46,584 per year in energy costs, resulting in a payback period of less than two years.
Hopkins has accessed $5.5 million in BGE rebates across all campuses since the rebate program’s inception five years ago.
Careful considerations must be made in order to install window films on existing glass. The films absorb solar heat, which means the glass itself is heated. This can induce stress. Films are carefully designed to not stress the windows beyond their tolerance.
“One of the problems we were having at the BSPH was people putting cardboard or black garbage bags in front of the windows and routinely shattering the windows,” Kirk said.
BSPH occupants also expressed public health concerns about possible outgassing by the films or their adhesives; SHIP and the Office of Sustainability carefully investigated all of these possibilities before moving forward with the project.
Additionally, on the Homewood campus, films were narrowed down to those that fit the buildings, then SHIP conducted surveys with samples to determine optimum reflectivity, tint level and color per taste. Students, Facilities and the University Architect weighed in.
The project started as a SHIP initiative to investigate window treatments, such as blinds and shades. Eventually, window films were selected as a better solution, as they require no maintenance by the occupants of the building.
The Office of Sustainability, which often works with SHIP, helped the students find suitable buildings for a demonstration of the technology. SHIP drafts a plan for a project, proves that it will save energy and money on paper and submits those plans to the respective Divisional Business Officers of the Whiting School of Engineering and the Krieger School of Arts and Sciences to receive funding.
These projects are considered demonstration projects; they exist to prove the viability of a solution. Going forward, the Office of Sustainability wants building occupants and Facilities to take initiative in evaluating whether window films will be a good addition for their building.