PR1997

The U.S. Environmental Protection Agency is seeking to improve the thermal quality of newhomes, most of which are being built in the sunbelt by large building development companies.Low-infiltration production (tract) homes need ventilation systems that satisfy the low-costpriority of the builders as well as the safety, health and low operating cost expectations ofhomeowners.

The performances of self regulating natural ventilation devices (devices of which the openingsection varies as function of the pressure difference across the device) strongly depend on thetype of building and its leakage characteristics. In like manner, the climatic conditionsstrongly impact on the achieved ventilation rates. As a result, it is not possible to express thepotential benefit of self-regulating natural ventilation devices in an unambiguous way. This isnot contributing to a good understanding of the potential of such devices in daily practice.

The concept of 'build tight - ventilate right' requires minimising air infiltration through theenvelope of a building and then providing adequate ventilation in a controlled manner tosatisfy the fresh air requirements of occupants. This paper describes a simple-to-use designtool (PC based and in spreadsheet format) for predicting the airtightness of office buildingenvelopes either at the design stage or before a major refurbishment.

Evaporative cooling is an interesting alternative to conventional compressor refigerationsystems for air-conditioning. However, the use of evaporative cooling presupposes all-airsystems and is, to a large extent, limited by ambient conditions as well as the settled demandson the indoor climate. High outdoor humidity levels have a great influence on the supply-airtemperature achievable, i.e. cooling loads possible to meet. One way to reduce the influenceof these limitations is to use desiccant cooling, i.e. to dehumidify the ambient air before theevaporative stages.

We examine conditions under which the natural forces of wind and buoyancy may beharnessed in order to provide ventilation for cooling. Steady-state, displacement flows drivenby combined buoyancy and wind forces are simulated at small scale in the laboratory using aPerspex box to represent a generic room or single-spaced building. Density differencesnecessary to simulate the stack effect are produced using fresh and salt water solutions. Windflow is simulated by placing the box in a flume tank; the flume produces a flow of water pastthe box and this flow is used to represent the wind.

Solar control devices placed in front of large building openings disturb air flow and theradiation transfer. Although solar radiation transfer through obstructed openings is arelatively well researched area, very little information is available regarding the air flowperturbations and daylighting alterations created by external solar control devices. Thepresent paper reports a series of experiments aiming at investigating natural ventilationand daylight phenomena associated with the use of specific shading devices.

NiteCool was developed under the Energy Related Environmental Issues in Buildings(EnREI) DOE Programme and is designed especially for the assessment of a range of nightcooling ventilation strategies. The program is based on a single zone ventilation model and isconfigured to analyse a 10m x 6m x3m cell of an office building. It is intended to be used atthe early stages in the design process to help the designer to make informed decisions on theconstruction, opening configuration and operation of the building.

There are certain conditions which are of interest when designing for natural ventilation ofcommercial buildings. These are:- summer cooling- indoor air quality in winter- night-time cooling.For the first two conditions it is necessary to determine the distribution of open areas to givethe desired distribution of flow rates. Since one is dealing with openings whose position andbasic geometry are known, the problem is relatively simple compared to general ventilationproblems.

In this paper the energy impact of natural cross ventilation is examined conducting a set of crossventilation experiments in a well insulated apartment of a 5-storey building. The experimental resultscompared with simulation results derived from the combined use of the multizone air flow modelCOMIS and the thermal model Suncode.A 24-hour lasting natural cross ventilation experiment was conducted, to monitor thermal comfortventilation mainly during the day and night time cooling ventilation.

There are a number of methods available concerning with distribution of air in buildings. Within control research, one can find new control algorithms which have not yet been used in practice. These new algorithms open the possibility of developing andimplementing of new demand controlled ventilation systems.In a building the internal air motions are due both to differences in temperature andpressure differences caused by the ventilation system.