ANALYSIS OF THE ENERGY PERFORMANCE OF A BOROSILICATE COATING
JACK E. KERSTEN
Dr. J.E. Kersten, P.E. & Associates
Mechanical Engineers
Rondo Cordova, California
Mr. Kersten's objectives are to provide new data and information advocating significant and reductions in building energy demand and simultaneously extend roof life by including borosilicate’s coating systems in architectural an.d engineering plans. ·
On April 12, 1981, the space shuttle, Columbia was launched from Kennedy Space Center to a 172-mile altitude, circular orbit at 40 degrees inclination around the earth. The flight lasted 54 ½ hours before landing at Dryden Flight Research Center in California on April 14, meeting all primary objectives. The landing of Columbia marked the first time that a manned non-ballistic re-entry had ever been performed. It involved flying a space vehicle/glider by orbiting over the Indian Ocean, area, ending temperature of 2,700°F upon re-entry into the atmosphere, approaching the California coast at 2.27 miles per second and landing on a three-mile-long runway in the Mojave Desert, touching down at 196 knots.
A most critical problem which took years of research to solve was to find a practical way to dissipate enduring temperatures of up to 2,700°F (l,482°C)from the outer skin of the shuttle upon re-entry into the atmosphere at ten times the speed of sound. To protect the vehicle and the astronauts from such intense heat, Lockheed Missiles & Space Company developed ultrapure silica fiber insulation tiles which were coated with a 15 mil (0.015 inch or 0.038 cm) thickness of borosilicate glass. This was a space age discovery. Consequently, temperatures on the shuttle's aluminum skin never exceeded the structural design limit of 350°F (176°C). A cutaway view of the tile is provided in Figure 1.
Borosilicate coating is the only material identified to date with such pronounced dissipation property values. This combination of values produces the "cool surface phenomenon" where a roof surface exposed to full sunlight during a hot summer day is relatively cool to the touch of the hand. This is a very simple “hands on” demonstration that borosilicate coating significantly reduces heat load on a building.
3.1.l
Case Test No. l:
In early September 1994, with outside temperatures ranging from 100°F (38°C) to 105°F (40°C), the Detering Grade School Kindergarten room in Carmichael, California, was sweltering in mid-90°F (32°c) temperatures. This room has an 18ft. ceiling and was without air conditioning. The building had a commercial rolled asphalt roof. After coating the roof and the west (sunny side) wall of the kindergarten room, the teachers reported that with recorded heat temperatures outside of 101°F (38°C) to 105°F (40°C); the inside temperatures were 74°F (23°C) to 78°F (25°C), respectively, after the coating was applied. This is a 27°F difference from the outside to the inside during the outside heat peak.
Case Test No. 2:
Information contained in Patterson (1992) provides data recorded from a Florida home giving additional verification that where building located in hot, humid temperature climate (over 95°F) energy consumption is significantly reduced (over 30%) after roof modification with borosilicate coating.
Summary of KW. h Consumption
Home in Casselberry, Florida
Billing Period: 6/9/92 – 7/13/92
% of Roof Coated: None
K.wh Consumed: 1,970
% Change: -
Billing Period: 7/13/92- 8/10/92
% of Roof Coated: 50%
K.wh Consumed: 1,603
% Change: 18.6%
Billing Period: 8/10/92 –9/10/92
% of Roof Coated: 100%
K.wh Consumed: 1,329
% Change: 32.5%
Case Test No. 3:
A case study of a 50,00 sq ft manufacturing building with HVAC including a 6,000 sq. ft office area, located in Sacramento County, CA. The building requirement is for 6,000 sq. ft. of airconditioned office space.
The original standard design required 29 ¼ tons of air conditioning (200 sq. ft./ton) in the office area for an estimate installation cost of (29 .25 tons x $1,200/ton) $35,100.
The revised design incorporated 6,000 sq. ft. of borosilicate white roof coating over a new roof at a cost of $1.00 per sq. ft. and reduced air conditioning requirements to 20 tons in the office area. Total cost of the revised design is [(20 tons x $1,200/ton) + ($1.00/sq. ft. for coating x 6,000 sq. ft.)] $30,000. The revised design will affect a reduction in capital cost of ($35,100 - $30,000) $5,100 or a 15% reduction in capital cost.
In addition, the building user will save an estimated 30% of the annual energy demand for the office area (Reference Case Test No. 2), and with estimated utility bills of $1,000/mo.)and savings of (.3 x $1,000/mo.) $300/mo. is projected as a result of the reduced power requirements.
Thus, the annual energy-savings are $3,600/year. Then by applying the 15-year product warranty, the total energy-savings is projected to be $54,000 over the life of the material warranty.
Summary
In this paper, information and data describing the physical properties and thermophysics of a borosilicate coating have been presented. Studies of the applications of this coating demonstrate that it performs as a heat-barrier that significantly reduces summer heat loads on buildings and shows insulative characteristics during winter months. It saves a significant amount of cooling and heating energy throughout the year. By simply coating an uninsulated building without air conditioning, will reduce inside temperatures during a summer day by 10°F. Studies, testing and observations for borosilicate coating applications and performances over the past five (5) years exposure to UV, roof membranes of borosilicate coating, show little or no surface degradation, and the coating continues to retain its elastomeric properties matching those of borosilicate coating.
Specifically, this paper demonstrates that borosilicate white coating (in a class by itself) can save up to 70 or 80 % of cooling costs under certain conditions, but in general, the coating can save 30 to 50% of total annual energy requirements.
The most significant obstacle in borosilicate coating use is that architects, engineers, builders and urban planners need to be informed. Borosilicate white surface technology and its energy-saving, ecological and humanitarian benefits must be presented in terms that people understand and backed by the engineering community. The main purpose of this paper is to inform the members of the ASME and others abut borosilicate white coating and its applications and performances.
