This paper explores the existing literature on indoor environmental quality (IEQ) evaluation models and proposes a new weighting and classification scheme. Studies that attempt to provide IEQ assessment of commercial buildings through a scoring system are reviewed and critiqued. Objective and subjective evaluation methods and correlations are discussed. The use of assessment categories (classes) in IEQ models is critiqued and an argument is proposed against their adoption. IEQ weighting schemes are summarized and compared against a newly developed scheme based on 52,980 occupant responses in office buildings. A binary assessment classification scheme is proposed in alignment with the ASHRAE/CIBSE/USGBC Performance Measurement Protocols for Commercial Buildings.

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This paper describes the development of a simplified calculation method for design cooling loads in underfloor air distribution (UFAD) systems. The simplified design tool is able to account for key differences between UFAD and traditional mixing overhead (OH) systems. These include: (1) difference between design day cooling load profiles, (2) impact of a thermally stratified environment for UFAD vs. well-mixed for OH, and (3) impact of heat transfer (temperature gain) in underfloor air supply plenums. The new design tool allows the use of a familiar load calculation procedure for OH mixing systems as input to the UFAD design tool. Based on 87 EnergyPlus simulations, four regression models have been developed to transform the OH cooling load into the UFAD cooling load, and then to split this total load between the supply plenum, zone (room), and return plenum. The regression models mainly depend on floor level, and position (interior or perimeter) and orientation of the zone under analysis. Although considered in the analysis, supply air temperature, window-to-wall ratio, internal heat gain, plenum configuration, climate, presence of the carpet and structure type do not strongly influence the developed models. The results show that, generally, UFAD has a peak cooling load 19% higher than an overhead cooling load and 22% and 37% of the total zone UFAD cooling load goes to the supply plenum in the perimeter and interior, respectively.

The installation of a raised floor system can change the thermal behaviour of the building by reducing the interaction between the heat gains and the thermally massive concrete slab. In this study, the influence of the raised floor on the summer design day zone cooling load profile is evaluated for an office building located in San Francisco by using the whole-building energy simulation program, EnergyPlus. The zone cooling load profiles and the thermal performance with and without the raised floor are compared and analyzed. The effects of structure type, window-to-wall ratio and the presence of carpet on the thermal behaviour of the raised floor are also investigated. The results show that the mere presence of the raised floor largely affects the zone cooling load profile and the peak cooling load over the range of -7% to + 40%. The most significant parameters are the zone orientation, i.e. the exposure to direct solar radiation, and the presence of floor carpeting. If carpeting is present, commonly used in U.S. office buildings, the overall impact on zone peak cooling load is reduced, ranging from 0 to 5% greater for the raised floor than without it. Without carpet the peak cooling load is 4% greater with raised floor than without it in the north zone, 22% in the east and west zones, and 12% in the south zone.

In this paper, an EnergyPlus model was used to simulate the operation of a novel integrated HVAC system. This system combines an underfloor air distribution system with a cooled radiant ceiling slab. A cooling tower supplies water to pre-cool the structural slabs during the night and early morning period. The paper compares the performance of this system to both a typical overhead system and a typical UFAD system in the cooling season for the Sacramento, California climate. When compared to the overhead system, the integrated UFAD/Radiant system shows a 22-23% reduction in total energy consumption during the peak cooling months (June to August) and a 31% reduction in peak hourly electricity demand. When compared to the UFAD system, these reductions are 21-22% and 24% respectively. An investigation of the simulation results showed that the integrated UFAD/Radiant system also improves occupant thermal comfort and reduces thermal decay issues in the underfloor plenum.