PR2019

Infiltration is an uncontrolled contribution to ventilation in a building and can contribute significantly to the total ventilation rate, particularly in older, leaky, dwellings which can rely on infiltration to provide adequate indoor air quality. However, as explored in this paper, using a whole house airtightness metric to characterise ventilation rates can fail to identify low ventilation rates in specific rooms. 

Indoor air quality is the chemical, physical and biological properties that indoor air must have to not cause any negative impact on occupants’ health and provide comfort: feel fresh, pleasant and stimulating. 

Installing Natural Ventilation (NV) system in office buildings leads to the reduction of energy consumption of heating, ventilation and air conditioning (HVAC), which accounts for approximately 50% of total in an office building in Japan. However, it is difficult to estimate the NV performance before its completion, because the NV system is easily affected by the outdoor environment. Thus, its design method is not yet established.

Building energy simulation (BES) and Airflow network (AFN) programs generally incorporate wind pressure coefficients (Cp) estimated from secondary sources, namely data bases or analytical models. As these coefficients are influenced by a wide range of parameters, it is difficult to obtain reliable Cp data. This leads to uncertainties in BES-AFN models results, especially for naturally ventilated building studies, where air change rate which strongly depends on Cp, is a key value for thermal comfort and energy consumption results.

This study aims to experimentally evaluate the influence of the combination of a supply only ventilation, called here positive input ventilation, and innovative active air vents on the Indoor Air Quality of a house. The positive input ventilation draws fresh air from the outside, filters and pre-heats it before blowing it in living areas. Active air vents are small motorised damper set up in upper parts of windows that can move according to local pollutants measurements or according to the measurements of the other active air vents in the house.

Guaranteeing high indoor air quality and high degree of user satisfaction at the same time is one of the challenges when improving the energy efficiency of a building. Current non-residential buildings mainly use mechanical ventilation systems to ensure high air quality. Mechanical ventilation systems are known for minimising heat losses but at the same time lead to higher installation, operating and maintenance costs. Furthermore, mechanically conditioned rooms may lead to the sick building syndrome caused by the lack of operable windows.

The mainstream of air-conditioning system for medium and small sized buildings is conditionally air mixing ventilation with ceiling cassette unit of packaged air conditioner (PAC), however, it may bring a high cold-draught risk to occupants, due to the direct drop of the supply air jet. To solve this problem, the air mixing ventilation system can be improved into an air based radiant air-conditioning system by stretching the non-flammable membrane under the ceiling with PAC, thus the cold-draught of PAC could be substantially eliminated and the indoor environment could be improved easily.

Recently in Japan, many buildings introduce packaged air-conditioner (hereinafter, this is called “PAC”) as an air conditioning equipment. Most of the PACs can change the direction of supply air blown from the unit and the “Swinging Mode” can change airflow direction periodically as one of the airflow direction setting of PAC. Before constructing the building, appropriately predicting the indoor environment (e.g. temperature distribution or air velocity distribution and so on) is important for indoor environment design.

The present paper describes the design improvement of a single-room ventilation unit. This ventilation system presents many advantages, however, several drawbacks exist. The first one is the acoustic disturbance. As the facilities are directly installed within the rooms, the fans’ noise may create discomfort. Furthermore, in the cold or temperate climates, condensation or frost may appear. A dedicated management should then be implemented. Finally, as the system is not centralized, communication between the different units is required to ensure the global system efficiency.

The purpose of this paper is to summarize the status of promising low carbon building services solutions fitted for a low emission building stock in urban areas.