office building

The work presented in this paper was done in 1997 as a final thesis in mechanical engineering, supervised by TRANSSOLAR Energietechnik GmbH in cooperation with the Institute for Thermodynamics and Heat Technology (ITW), University of Stuttgart. The contents of the work is the investigation of natural ventilation through window openings (single sided and cross ventilation) in an existing office space. Both measurements and computer simulation have been conducted.

Air conditioning is widely used in the office building sector in the French Mediterranean region. Though often a «sine qua non» for renting office space, there is however a widespread feeling that operating and maintaining air-conditioning systems can be troublesome (unreliability, regulation and maintenance difficulties, non uniform comfort conditions, high prices are frequently lamented).

The present paper investigates the potential of night ventilation techniques when applied to full scale office buildings, under different structure, design, ventilation, and climatic characteristics. The approach of this study includes the use of both experimental data and theoretical tools in order to determine the impact and the limitations of night ventilation regarding the thermal behavior of various types of office buildings.

OFFICE is a research project partly funded by the CEC dealing with the passive retrofitting of office buildings to improve their energy performance and indoor working conditions. The project is coordinated by the University of Athens with the participation of organizations and research institutes from eight European countries. The aim of the project is to develop global retrofitting strategies, tools and design guidelines in order to promote successful and cost effective implementation of passive solar and energy efficient retrofitting measures to office buildings.

This paper describes the methodology used in the Design and Evaluation Group in the project OFFICE - Passive Retrofitting of Office Buildings to Improve their Energy Performance and Indoor Working Conditions' funded by the European Commission under the JOULE III Programme. The objectives of the OFFICE project are to promote passive solar and energy efficient retrofitting measures in office buildings.

A comprehensive concept for an energie and comfort orientated retrofitting is realised for an office high rise building ,,BS 4" (on campus at Braunschweig Technical University). This master plan will take the form of a research and developement projekt; a pilot realisation will be carried out on the 10th floor.

Natural ventilation can be a part of a strategy for a good indoor air quality. It can also be a way to realise night time ventilation during warm periods. In this latter case, the aim is to cool down the thermal mass of the building to obtain a better thermal comfort during daytime. Night time ventilation requires high ventilation rates and sufficient accessible thermal mass. The ventilation openings have to be well designed to avoid undesirable effects like rain, pollution and burglary.

At Hermann-Rietschel-Institute systematic tests of the limits for the ventilation with openable windows are under way. The parameters temperature distribution and air velocity are the most attended values. Window ventilation in office buildings has limits in application. An open window can remove cooling loads out of the room. With one window and a room with a depth of 5 m, the maximum cooling load is about 20 to 30 W/m2. These limits are determined by air velocities within thermal comfort.

Using isothermal full-scale experiments and 3-dimensional CFD simulations it is investigated how normal office furniture influences the air movements in a mixing ventilated room. Two different types of inlets are used in the experiments and a set-up with normal office furniture is made. The set-up is simulated with one of the inlets where a volume resistance represents the furniture. The jet under the ceiling is investigated and it is found that the normal office furniture does not influence the air movements in the upper part of the room.