Open plenum vs. dropped ceiling: The debate over life cycle cost
Calculating the tradeoffs between cost and performance can be tricky.
While suspended, lay-in ceilings have long been the norm in commercial design, the open-plenum ceiling has become trendy and economical, particularly in office and retail environments. However, calculating the tradeoffs between cost and performance can be tricky.
Very little data exists comparing suspended ceilings with open ceilings on the basis of cost and performance. The most recent study came from the Ceilings & Interior Systems Construction Association (www.cisca.org) five years ago. In the study, office and retail spaces were modeled in Chicago, Charlotte, Oklahoma City, Orlando, and Phoenix to reflect the differences in energy costs, climate, and installation costs. Initial construction costs were determined using RSMeans data; annual operating costs for HVAC, lighting, and maintenance were calculated according to Building Owners and Managers Association data.
The study found initial construction costs for suspended ceilings to be 15-22% higher in offices, and 4-11% higher in retail spaces. However, total energy savings for lay-in ceilings vs. open plenums were 9-10.3% in offices and 12.7-17% for retail. A 10.5% energy reduction qualifies buildings for a LEED EA credit, and a 14% reduction is good for two points.
The study attributed the energy performance advantage of suspended ceilings to the use of a return air plenum with low static pressures and fan horsepower vs. ducted air returns with higher static pressures and fan horsepower in open-plenum systems. In addition, return air plenums more efficiently remove heat from lighting systems and reduce the AC load. Suspended ceilings also offer about 20% higher light reflectance, thereby reducing lighting costs.
For more information, see: http://www.cisca.org/files/public/LCS_brochure_rev_9-08_lo-res.pdf.