Influence of raised floor on zone design cooling load in commercial buildings

Abstract

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.

Simplified calculation method for design cooling loads in underfloor air distribution (UFAD) systems

“…The cooling load profiles for the two systems are different. The main reason for the difference between the overhead system and UFAD is the thermal behaviour of the raised floor [9]. The HVAC system is operating from 5:00 to 19:00.…”

“…The amount of energy generated in the building or entering the building is the same for the two systems but the amount that the HVAC system has to remove is different because, for the OH system, part of the energy is accumulated in the slab during the day and is released at night when the system is off. In the UFAD system the presence of the raised floor reduces the ability of the slab to accumulate heat, thereby impacting the cooling load, as described by Schiavon et al [9]. Table 3.…”

“…Schiavon et al [9] showed that the presence of the raised floor affects the cooling load profiles, therefore it is possible that the cooling load profile of UFAD is different from the cooling load profile of a building ventilated by an overhead system (also called mixing ventilation). Moreover, the presence of stratification affects the heat exchange in the zone and this may also affect the cooling load profile.…”

Dynamic Energy Modeling of an Experimental Building Equipped With an Underfloor Air Distribution (Ufad) System

“…Although the results of these researches regarding UFAD systems are available, most of them are focusing on the application of this system in commercial building and under cooling operation (Schiavon et al, 2011;Bauman et al, 2006;Schiavon et al, 2010;Alajmi and El-Amer, 2010). The researches regarding the application of UFAD systems in residential dwelling and/or under heating operation are very limited.…”

Comprehensive approach to modeling and simulation of dynamic soft-sensing design for real-time building energy consumption

“…Various techniques are used to select influential variables for soft sensors which fall under three groups: wrapper methods, filter methods, and embedded methods. The main influential variables, for example, relative compactness, 21 building location climate, 22 surface area, roof area, wall area, 23 and window orientation, 24 should be divided into two aspects: the physical materials of buildings and local meteorological conditions; furthermore, the physical materials can be represented by thermal inertia, which is reflected in the historical thermal loads. These factors make the relationship between Environmental Protection Board (EPB) and its influential variables quite complicated.…”