VC

This paper investigates the dynamic cooling performance of a novel system combining natural ventilation with diffuse ceiling inlet and thermally activated building systems (TABS). This system is tested in the lab under three climatic conditions representing typical seasons in Denmark, including a typical winter day, a typical day in the transitional season and a typical summer day. The corresponding dynamic control strategies have been designed for these three cases in the measurements.

A novel HVAC system combining natural ventilation with diffuse ceiling inlet and thermally activated building systems (TABS) has the ability to fulfill the requirements of cooling and ventilation in future Danish office buildings. In order to study the cooling performance of this system, a test chamber is constructed in a way to represent the characteristics of an office room. Twenty cases are tested under steady-state conditions, including ten cases without ceiling panel and ten cases with ceiling panel.

Many post-occupancy comfort studies of energy renovated residential buildings have documented elevated temperatures above comfort levels, not only during the summer period but also during the shoulder months. The main focus in renovation projects is on heat savings while the risk of overheating is not considered.

Buildings constructed before 1979 in Denmark are responsible for 75% of the total energy consumption of the sector. However, many post-occupancy comfort studies of energy renovated dwellings have documented elevated temperatures not only during the summer period but also during the transition months. Ventilative cooling can be an energy-efficient solution to avoid overheating in energy renovated residences.

In many post-occupancy studies of renovated houses elevated temperatures have been documented. This article presents in which situations overheating need to be addressed and which renovation measures are causing this need. The analysis contains representative houses from central and north Europe. Both dynamic and static overheating assessment criteria are used.

In the PSO project 345-061, a novel system solution combining natural ventilation with diffuse ceiling inlet and thermally activated building systems (TABS) has been proposed for cooling and ventilation in Danish office buildings. Due to the application of diffuse ceiling inlet, cold outdoor air can be supplied into the room without any risk of draught even in the extreme winter. This means that natural ventilation is available even in winter and it is beneficial to reduce the energy consumption for buildings with cooling demand in cold seasons.

This paper presents a comparative study based on CFD simulation between the performance of Impinging Jet Ventilation (IJV) and Mixing Ventilation (MV) systems in providing indoor air quality and thermal comfort for a mechanically ventilated occupied large open plan office (floor-to-ceiling height > 5m). Large spaces differ from spaces with standard heights because of the significant upward stratification.

Ventilative cooling can be used as a passive cooling measure to reduce the cooling energy demand of buildings. It can be used during the day, directly removing excessive heat gains, or during the night (i.e. night flush), in which cold outdoor air flows through the building and cools down the indoor air volume and subsequently the thermal mass of the building. Night flushing reduces the indoor air temperatures at the beginning of the next day and the cooling demand over the day.

The outdoor climate is changing and the airtightness and insulation levels of residential buildings are improving. During the warmer season this can lead to overheating problems, especially when the house is situated in urban areas. In order to reduce overheating problems, ventilative cooling can be used to keep the indoor conditions at a comfortable level. Natural ventilation is not always a feasible solution, for the risk of burglary, and when the outdoor temperatures are not suitable for cooling the house, for instance in urban heat islands. 

In school and office buildings, the ventilation system has a large contribution to the total energy use. A control strategy that adjusts the operation to the actual demand can significantly reduce the energy use. This is important in rooms with a highly fluctuating occupancy profile, such as classrooms and open offices. However, a standard rule-based control (RBC) strategy is reactive, making the installation 'lag behind' in relation to the demand. As a result, a good indoor climate is not always guaranteed and the actual energy saving potential is lower than predicted.