People frequently cite a number of benefits related to underfloor air distribution (UFAD) systems—more flexibility, better indoor air quality, comfort, energy efficiency, and reduced lifecycle costs. These benefits may be realized in practice, however much depends on the system design, building use, climate, and other factors. The focus of this paper is to describe each of these benefits briefly, discuss what is required to take advantage of these potential benefits, and note what is commonly observed in current practice.

This paper reports on a modeling study to investigate the primary pathways for heat to be removed from a room with underfloor air distribution (UFAD) under cooling operation. Compared to the standard assumption of a well-mixed room air condition, stratification produces higher temperatures at the ceiling level that change the dynamics of heat transfer within a room as well as between floors of a multi-story building. A simplified first-law model has been used to estimate and compare the relative magnitudes of the heat being removed from a room through two primary pathways: (1) heat extraction via warm return air exiting the room at ceiling level or through the return plenum and (2) heat entering the underfloor supply plenum either through the slab from the floor below or through the raised floor panels from the room above. Surprisingly, it is shown that up to 40% of the total room cooling load is transferred into the supply plenum and only about 60% is accounted for by the return air extraction rate. The implications for the design and operation of UFAD systems are discussed.

Building loads are calculated using hourly weather tapes from the nearest available first-order weather station, or from data summarized from such tapes. These weather stations are ofter remote from the building site, and in different terrain. The climate experienced on site may be significantly different from that on the weather tape, and as such a result the energy use simulated for envelope-dominated buildings can contain substantial error.

A program is described that modifies hourly weather tape data to make them more closely approximate the climate found on building sites. The program is eventually intended to be used by designers, engineers and researchers, who will input both local climate data and a description of the building site's physical surrounding in order to make the data transformations. The method is only partially tested and is still under development.

In this paper, the approach used to modify hourly weather data is discussed, the method of user input is presented, and the individual algorithms are summarized. Future refinements to the program and validation studies are outlined.