Project Title:

Underfloor Air Distribution Cost Analysis Model

Addressing industry needs for an accurate method for comparing the costs of UFAD and conventional HVAC systems.

Status (updated 7/25/2007): Ongoing

Funding sources: CBE Industry Consortium, Research Grants

Project Objective

Develop a detailed underfloor air distribution (UFAD) cost model to allow for comparisons between UFAD and conventional systems, and evaluation of alternative UFAD system designs.

Significance to Industry

Initial and life-cycle costs are major drivers in decisions regarding building mechanical systems. Accurate initial and life-cycle cost information is crucial to providing a sound basis upon which UFAD systems can be compared to alternatives. However this information is not readily available due to the multiple design factors that come into play in the design and integration of UFAD technology. A rigorous method is needed by the building industry to allow comparisons between standard overhead systems and the numerous UFAD design options now available.

Research Approach

CBE first conducted a preliminary UFAD cost study using input from industry partners. This initial study, completed in 2001, focused on first-cost comparisons and the development of an analysis framework. The result was a first-cost breakdown of major elements in the base building and tenant improvement work for three different UFAD office building prototypes. The study compared the UFAD building prototypes against a traditional overhead system, using a cost estimating database and other information supplied by industry partners. This and subsequent work demonstrated that several key factors affect the cost differential, and that the initial cost of UFAD systems could be comparable to, or slightly higher than, that of conventional systems.

The final research scope, funded by the U.S. General Services Administration (GSA), is a multi-year study to be conducted in three phases. In the first phase CBE investigated the cost analysis methods employed by several CBE industry partner firms. Based on the results of this investigation and the previously developed framework, we created an analysis methodology and cost model structure. In the second phase, CBE studied alternative building and system designs to validate the model using data collected from completed projects. Detailed elements of each cost component were identified and reviewed with professional cost estimators. The model is now able to predict a range of costs for those elements of a building that are affected by an underfloor system, and will allow for a comparison of underfloor to conventional systems.

The final phase of the project was the development of a model for life-cycle cost analysis. For this phase CBE gathered additional information related to the life-cycle costs, including commissioning, operations, energy, and churn. The final life-cycle analysis will be conducted using the UFAD EnergyPlus simulation program to generate energy data for UFAD buildings.

Publications and Reports

Webster, T., C. Benedek, and F. Bauman, 2006. Underfloor Air Distribution (UFAD) Cost Study: Analysis of First Cost Tradeoffs in UFAD Systems. Report to U.S. General Services Administration, September.

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Webster, T . 2005. Research Overview of the UFAD Cost Analysis Study. Berkeley, CA, October. (PDF)

CBE UFAD Test Facility

The costs of UFAD buildings are dependant on the integration of systems, architecture, and interior design.

CBE UFAD Test Floor

The UFAD cost analysis model allows for detailed comparisons of multiple design options.