Ventilation and air conditioning systems mainly use fossile primary energies as gas, oil and coal for the heating and cooling processes. Air conditioning means heating and humidifying the supply air during the winter season and cooling and dehumidifying the supply air in the summer season. For these summer operations the supply air in general is cooled down lower than the dew point in order to dehumidify the air by condensation. Afterwords the supply air is reheated again to reach the required temperature level for room inlet.

User experiences of the workings of a ventilation system have often been pretty disheartening. Draughty, too hot, noisy, too stuffy are some of the verdicts which in many cases have been confirmed by objective measurements. Often the complaints are due to the air flows not being appropriate to the room. This in turn can be due to adjustment difficulties or to the flow balance in different branches of the system being affected by residents tampering with the supply or exhaust air terminal device settings.

A Test House at EA Technology, Capenhurst, has been refurbished to provide a ventilation test facility. The house was required to meet the following requirements: - A high standard of air tightness - Insulation to current Building Regulations or better - Incorporation of several ventilation systems - Comprehensive instrumentation The original timber frame front and rear facades of the house were replaced with brick and block construction. All internal floors, ceilings and partitions were replaced and the external walls replastered.

The aim of the study was to identify methods for the renovation of ventilation systems in domestic buildings which are 3 - 8 storeys high. Three typical buildings were selected and the problems in ventilation were examined. The designers made their proposals for repairs and the research team analyzed the solutions and made improvements. The special problems compared with new buildings included less airtight building envelopes and leakages in existing ventilation ducts.

The "Passivhaus Darmstadt-Kranichstein" is a 4 unit terrace house with an extremely low total annual energy consumption of less than 32 kWh/m² of living area, thereof about 12 kWh are needed for room heating /Feist 1994/. The determinig factors for the low consumption are the superinsulation, airtightness of the thermal envelope in combination with a highly efficient VAV ventilation system, and an improved window construction. The "Passivhaus" therfore is a typical example of an improved low energy house.

The paper is presenting experience from a several year long time of operation in a group of apartment buildings in the Stockholm area, Sweden, having an extremely low energy usage, less that 110kWh/(m2.year), electricity supply to the building services included. The system solution used has a very low pressure drop in the exhaust ducts. Every exhaust point is connected to an individual duct leading to a fan chamber in the attic. The pressure in that chamber is kept constant.

This paper shows preliminary results of 18 out of 30 inspected ventilation systems in low rise, low energy residential buildings. We propose a method for the assessment of energy efficiency of ventilation systems. The majority of the inspected exhaust systems fulfills the conditions for the demanded air flow rates and energy efficient operation. However, typically the distribution of airflows to the rooms of the supply zone is rather weather dependent due to insufficient airtightness of the buildings and large stack heights.

After a short description of the physical phenomena involved, unified expressions are worked out describing net airflow and net heat flow through large vertical openings between stratified zones. These formulae are based on those of Cockroft for bidirectional flow, but are more general in the sense that they apply to situations of unidirectional flow as well. The expressions are compatible with a pressure network description for multizone modelling of airflow in buildings. The technique has been incorporated in the flows solver of the ESP-r building and plant energy simulation environment.

In order to reduce the heat loss from buildings it is common to increase the thickness of insulation in the building envelope.The consequence of this action is more expensive buildings. Building regulations in countries with cold climate require U-values far the envelope which results in thicker and therefore often stronger constructions than needed for structural capacity. Another strategy to save energy has been to reduce the ventilation rates in buildings.

This paper presents the results of a monitoring programme on a medium sized educational building which has had the external walls re-clad. The objective behind the re-cladding was to improve the durability of the building and to improve the thermal performance. The objectives of this work were to establish the viability of the calculation techniques used to simulate the ventilation, thermal and moisture performance of the re-cladding system. The results have shown that there is a good agreement between the methods currently being used and the actual performance.