It's Over Our Heads
- By Jerry Enderle
- February 1st, 2001
The space above the ceiling is an area that is not often thought about, but it can be the cause of a lot of frustration during the construction and installation process. The fact is, some consider it to be the most important space in a building.
With so much going on inside such a small area, there must be considerable forethought that goes into its planning and design. To find out exactly what is involved, SP&M spoke with several engineers from the DLR Group who deal with these questions on a regular basis. Answering our questions are: Robert Berry, PE, principal, at the Overland Park, Kan., office; Gary Nelson, PE, senior associate at the Phoenix office; and Shawn Whaley, PE, RCDD, principal at the Minneapolis office.
SP&M: Components like lighting, sprinkler systems, phone lines, computer cabling, electric, heat and ventilation ductwork, plumbing and PA systems are obvious, but what are some of the other things that are hidden above the ceiling tile?
NELSON: Mechanical systems above most school ceilings include: fan coil or heat pump air conditioning units; supply air ductwork with smoke detectors; return air ductwork; code-required outside ventilation air ductwork for indoor air quality; exhaust air ductwork and exhaust fans from toilets, showers and other areas; hot water or electric heating coils; variable volume fan powered terminal units; chilled water piping for the air conditioning system; piping for the heating system; cooling coil condensate drainage piping; and refrigerant piping for the air conditioning system.
WHALEY: Also included would be cabletray and the structural steel joists and beams -- they take up the most space. Cabletray and ductwork are the hardest equipment to coordinate with the structure to make sure it will all fit above the ceiling.
BERRY: The plumbing, to be fully appreciated, should include: domestic hot, cold and recirculated water; waste piping; vent piping; roof drain piping and roof drain overflow piping. The cooling system for a typical 4-pipe system includes chilled water supply, chilled water return, hot water supply and hot water return. These systems are piped to either a suspended fan-coil unit and its condensate drain piping, or to a VAV box for each individual zone of control.
In addition, the cooling system for a water source heat pump system has loop water supply and loop water return piping. This system is piped to a suspended water source heat pump and its condensate drain piping for each individual zone of control.
NELSON: Add to that, the waste drainage piping for any floor above the floor in question, plumbing vent piping for each trap in the school, natural gas piping, fire protection water piping and sprinkler heads.
SP&M: That’s almost overwhelming. When designing and planning that space, what are the biggest challenges?
NELSON: The biggest challenges are to make sure that the services needed (supply air, return air, exhaust air and the equipment) will fit into the space with allowances for inlets, outlets and piping clearance. Eventually, the equipment will need to be maintained. The location must be accessible by ladder, but in such a way as to keep the maintenance personnel as unobtrusive to the function of the space as possible.
WHALEY: Code issues are usually related to the area above the ceiling being a plenum space, which means that environmental air is being returned via the ceiling space. All cabling that is not in conduit needs to be plenum rated. All equipment that is to be above the ceiling needs to be carefully coordinated. Usually, showing zones for mechanical, electrical and technology works best.
BERRY: The biggest challenge is coordinating all of those systems mentioned so they don’t run into each other. The next challenge is code-related -- specifically, all of the rated wall types that require fire and/or smoke dampers at penetrations. Smoke dampers are worse because they are operated by an electric motor, which means one more conduit and one more piece of equipment that needs future maintenance access.
SP&M: What gets priority on space or placement?
NELSON: Systems that require sloped drainage, waste piping and condensate drainage take the first priority. Equipment, bigger pipe and ductwork should take the next priority. The fire protection piping must also be accommodated, because it requires precise spacing of the sprinkler heads. Problems arise when a general contractor does not oversee the work and allows the fire protection to be placed first, without regard to the other services.
WHALEY: The priorities are as follows -- structural, mechanical, cabletray, then electrical.
BERRY: I agree that first priority is usually the roof drain piping. Second priority is supply and return ductwork, since they occupy so much space. The heating and cooling piping come next because they are bigger than domestic water piping and are insulated. Next is the domestic water piping. Finally, the electric conduits have lowest priority, since they are smaller than pipes and easier to install. Exceptions to this rule are large electrical conduits -- more than two inches.
SP&M: How is this space regulated? Are there inspectors with codes? Who, if anyone, is ultimately responsible for and has the power to dictate how this space is used?
NELSON: I believe the person ultimately responsible is the general contractor. He is responsible for the construction of the entire facility. He has contracts with the subs and can and should direct the work.
WHALEY: There are many inspectors. Electrical inspectors look for clearances for equipment, like mounted disconnects and the plenum rating issue. Building code officials look for things like fire separations and if fire stopping is used when rated corridor walls have conduits going through them.
BERRY: It is the architecture and engineering firm’s responsibility to ensure that it is physically possible to get everything up there. But they can’t show all of the systems on a drawing, so the contractor has a responsibility to coordinate the system installations between the various subcontractors to avoid stacks that don’t fit in the space.
SP&M: It would seem that this issue becomes more complex depending upon the type of construction that is being done, for example, new, additions or renovation. Which is the most difficult and why?
NELSON: Renovations are the most difficult, especially when you must connect to existing water or air systems. The connection is usually problematic because the systems may or may not be constructed, and function, as they were originally designed.
WHALEY: Using existing ceiling spaces is by far the most difficult because you cannot coordinate between disciplines how the equipment will be located, you are stuck with a number of existing conditions.
BERRY: Renovations are clearly the most difficult. Existing drawings are never complete enough to show everything above ceilings. They involve many field visits, with a lot of lifting of ceiling tiles to try to determine what’s up there, before designing modifications to the systems or adding new ones. The job would be much less difficult if the entire ceiling could be removed before design begins. But that’s living in a dream world.
SP&M: What are the most common problems?
NELSON: Some common problems involve subcontractors who hang equipment from a lay-in ceiling. Or, the fire protection contractor running piping within inches of an electrical junction box. There are contractors who hang fan coil or heat pump units without spring isolation, or in a way that it touches the building structure, allowing vibration to reverberate into the space.
WHALEY: Probably the most common problem is dealing with equipment not fitting exactly where it is shown on drawings, and those changes that have to be made in the field. Another problem is cable tray needing to change levels, or even to be discontinued for a length of space because of lack of room.
BERRY: I would have to say unanticipated low beams, ducts, pipes, conduits, etc., that were not shown on original drawings or discovered in the tile lifting exercise are the most common problems.
SP&M: What is the most important thing to keep in mind when dealing with this space?
NELSON: The main thing to keep in mind is that saving of a few dollars in the construction budget, by not allowing adequate space above the ceiling for the services, always will cost more in the long run due to construction changes and conflicts. It would be great if every service above a ceiling could be coordinated in the construction document stage. In reality, this does not and cannot occur because some of the services are designed by the subcontractor at the job site and changes are made to accommodate a specific subcontractor’s work methods and schedule.
WHALEY: This space is valuable to almost every trade and if coordinated early in the design process, all equipment can usually fit. One solution that works well is coordination drawings. If the construction budget will allow, the specifier can make the all of the contractors do coordination drawings showing the proposed routing of all equipment above the ceilings. After the drawings are done, all of the equipment can be put on one drawing to look for serious conflicts. That way, problems can be found before anything is installed.
BERRY: First of all, if the project involves renovation, be patient when unforeseen conditions arise. The client has the right to be less patient if he was willing to pay a higher fee and allotted the proper amount of time in the schedule to thoroughly investigate existing conditions before the designing began.
In new construction, be prepared to pay for the extra materials needed to achieve adequate space above the ceilings. You must allow for all the systems to fit, at the very least, and have the room for the required system maintenance for the life of the building, at the very best. If you skimp on the budget for adequate ceiling space, be prepared to get what you pay for.
Above the ceiling is sacred space for data, voice and video cabling distribution. It is customary that special-systems cabling is the last piece installed. Proper coordination, however, is required when mechanical units occupy the most space (by far) and, once installed, cannot to be moved. Consequently, technology planning and design are critical at the outset of the project.
The number and size of conduits directly affects the amount of space needed above the ceiling to distribute data, voice and video cabling. EIA/TIA standards govern conduit size relative to the amount and type of cable that can be pulled through it (i.e., bending radius for fiber optic cable).
In addition to conduits, cable tray is often used as a flexible alternative in which to lay special systems cable. Cable tray is an efficient way to distribute a variety of cable. It varies in width and typically runs the length of hallways.
A relatively new phenomenon that is happening above the ceiling is the installation of wireless receivers and network electronics. With the advent of wireless technologies, wireless receivers are placed above the ceiling to provide omni-directional radio frequency coverage within a certain zone of a school. The wireless receiver requires a 120-volt power outlet and a connection to a hub or switch via an RJ-45 cable. Proper placement above the ceiling is critical to minimize any interference with other electronic or metallic materials or systems.
Network electronics are now being installed with ceiling tile systems. Decentralized infrastructure is a trend in educational technology. Such electronics as 10/100 megabit switches are being installed in classrooms.
Instead of "bolting on" the switch somewhere within a classroom, ceiling tile and technology manufacturers have combined their efforts to design a ceiling tile that can house a switch and drop down for easy access by technology staff. The switch then accommodates the copper cabling in the classroom and is linked via fiber back to the appropriate telecommunications closet. Once again, proper coordination above the ceiling is required to accommodate all of the technology cabling requirements that are now part of every educational facility.
John Burk, Ph.D., is a senior associate with the DLR Group and works out of their Phoenix office.