Design Innovations in Green Buildings
By Gerard Hillenbrand, P.E.
That was the interesting subject captivating the attention of the many attendees at our March 16th dinner meeting at Mullen’s Restaurant in Manhattan. This meeting was co-sponsored by N. Y. Chapter of N.Y.S. Society of Professional Engineers and the metropolitan section of the American Society of Mechanical Engineers and the subject matter qualified for 1 professional development hour of credit toward the continuing education requirements recently mandated by the N.Y.S. Department of education.
The evening’s speaker was Gary Pomerantz, P.E., who was substituting for the scheduled speaker Daniel Nall, P.E., F.A.I.A. Mr. Nall was called out of town shortly before the meeting. Messrs. Nall and Pomerantz are associates at the firm of Flack and Kurtz Consulting Engineers in New York City. Mr. Pomerantz’s presentation featured a computerized slide series depicting a number of Green Building Projects with which the Flack and Kurtz firm has been significantly involved. Green Buildings, of course, are structures that use materials and techniques, which enhance the environment in which they function. More specifically, this presentation covered the subject of radiant heating and cooling systems for these green buildings. The environmental advantages of radiant techniques over remotely powered, Fossil Fueled Furnaces, and Air-Conditioned space in conventional buildings are most evident in lower operating costs and energy consumption as well as substantial reductions in harmful emissions.
These advantages include avoiding expensive duct work for air distribution, dramatic reduction in air conditioning requirements, improved human comfort, and absorption of solar energy into the thermal mass of the building, and preferably, into the building floor which, ideally, should have a maintained ambient temperature of 68oF. To achieve this ideal several important factors must be considered and designed for. Among these is ventilation of the entire building space, humidity control, avoidance of water vapor condensation, changeover from heating to cooling modes, and lastly, the construction of the radiant floor itself. The analysis of these variable factors has been most effectively achieved by employing computerized modeling driven by a radiant heat program as a design tool. This program takes into account such factors as two-dimensional heat transfer along the radiant floor, the radiant fluxes of the heat emanating from the floor, the stratification of thermal effects in the room above the floor, the maintenance of the comfort zone in the lower part of the room, the varying effects of solar energy input and outside air flow, all coupled together to provide a visual depiction of the fluid dynamics behavior of the building.
The use of this program technique as a design tool was effectively illustrated by several projects successfully completed by the engineers of the Flack and Kurtz firm. The renovation of the St. Meinrad Arch Abbey Church built in England about the year 1100 was most impressive. This masonry structure has a 75-feet high nave and 39-feet high aisles with cast iron framed glass windows. The basic upgrade design was to construct a new radiant floor with an average year-round temperature of 23 oC (73 oF).
The new floor consisted of a grid of polyethylene tubing on 6 to 10 inch centers located on inch above the sub floor by Styrofoam clamps all embedded in a poured concrete upper floor. Because of the huge volume of space above this floor a fan operated ventilation system proved necessary. This system was controlled by a space sensor and introduced ventilation through benches above the floor. Displacement diffusers provided air velocity control and the return air-handling unit provided a bypass for reheat. Provisions for system operation during church closure also were needed.
Another interesting installation is the Calloway Discovery Center in Georg/Ax where a 6 inch thick concrete floor utilizes embedded pipes stapled to wooden board sub-flooring. The fluid circulated through the piping is taken from an adjacent lake used as a heat sink for both heating and cooling. A conventional ventilation unit controlled by space sensors provides fresh air when required. The use of an adjacent body of water as a circulating medium is becoming increasingly common in radiant heating systems. A number of installations have been successful in the San Francisco Bay Area and the I.B.T. headquarters in Santa Monica, Southern California, employs a bay on the Pacific Ocean.
The Hearst Building in New York City, now under going reconstruction and expansion, has been landmarked both inside and outside, thereby limiting design options. To let sunlight in, an all-glass roof has been designed and the building lobby has been modified to provide direct sunlight to the lobby floor, which produces a radiant comfort zone for people traffic in the lobby. Incidentally, radiant floors utilize dark colors most efficiently.
Another notable installation is the Clinton Presidential Library and Museum in Little Rock, Arkansas, which was recently dedicated during a rainy, uncomfortable day in the Ex-President’s hometown. The building itself is a long, narrow structure elevated off the ground with a 700 foot long by 40-foot high glass wall facing west. The structure has a capacity of 400 people and is ventilated by moderately pressurized air directed along the inside of the glass wall. Precise humidity control is also provided. The floor consists of a bamboo wood composite with 10 miles of radiant coils embedded therein. Ventilation equipment is located in a belly enclosure under the floor. Rainwater has been collected to provide processing fluid and irrigation of the surrounding grounds. A large atrium contributes to the energy input and tests have documented that the structure requires 34% less energy consumption than a conventionally constructed building of equivalent size.
Because of the length and detailed information provide by the presentation, the normal question and answer period had to curtailed. However, Mr. Pomerantz remained after the presentation to answer one on one inquiry and discussed all aspect of this very stimulating subject of Green Building Design. We look forward to greeting you at the next monthly meeting of our society, which promises to be equally significant.