Parameters for Designing Ventilated Spaces

The success of a ventilation system in buildings relies upon the design and the performance of its elements (Moghaddam et al. 2011). These include climate, function, geometry, orientation, layout of internal spaces, façade design and control and settings (Goncalves and Umakoshi 2010). Other factors contributing towards success include incorporating efficient HVAC equipment, heat recovery techniques and shading devices (Azarbayjani 2010). It is recommended that these parameters be optimised based on environmental principles and architectural rules to influence the overall building performance (Voss et al. 2007), as these elements determine energy requirements in a building, which in turn can enhance energy savings (Goncalves and Umakoshi 2010). The current study focuses on improving ventilation efficiency in office buildings due to the inclusion of a skycourt. In addition, it investigates comfort in the skycourt. Therefore, parameters that affect the ventilation performance in skycourts as ventilated spaces

should be considered. These can influence the thermal conditions in skycourts, which in turn impact on the energy demand of the buildings.

Several studies found that orientation, height, length, depth, size and form are the most effective elements in building energy performance, when considering ventilation. In addition, air openings’ characteristics influence the ventilation performance (Table 2-8). However, there are few studies that investigated the effects of skycourt attributes on both the building energy performance and skycourt interior environment.

Table 2-8. Studies exploring design parameters of ventilated spaces

Year Research Findings Reference

2018 Orientation

Glazing area and distribution

(Kosir et al. 2018)

2018 Orientation

Glazing area and specification

(Delgarm et al. 2018)

2017 Orientation Envelope properties

Attributes of adjacent spaces Shape and type

Glazing area

(Wang et al. 2017)

2015 External surface area Adjoining spaces

(Tabesh and Sertyesilisik 2015)

2014 Season Skycourt type

(Taib et al. 2014)

2015 Air inlet openings characteristics (number, position, size and location)

(Moosavi et al. 2015)

2014 Height

Width and length

(Cantón et al. 2014)

2012 Height Type of glazing Wall thickness

(Al-Masri and Abu-Hijleh 2012)

2011 Space dimensions Height

(Ai et al. 2011)

2010 Location of skycourts (Taib et al. 2010)

2010 Building form Orientation

Internal spaces configuration Arrangement of internal space Façade (Goncalves and Umakoshi 2010) 2009 Height Size (Zhang et al. 2009)

2006 Orientation of skycourt (Jahnkassim and Ip 2006)

For example, in a study that investigated the thermal comfort of different types of skycourts (sky-roof, skycourt and sky-balcony) during wet and dry seasons in a tropical climate, it was found that there is a significant difference between these skycourts in terms of mean air temperature and radiant temperature. The middle skycourt between floors is the most comfortable thermal zone, followed by the sky-roof and the sky- balcony. The skycourt has the highest mean value of air velocity of 0.67 m/s, while the sky-roof has the second highest value of 0.58 m/s (Taib et al. 2010). In addition, there was an impact of weather conditions on the performance of the three spaces. The average temperature during the wet season in these spaces is lower than the average temperature during the dry season (Taib et al. 2014).

The orientation plays an important role in the performance of skycourts. For example, skycourts located on western facades in tropical Singapore could act as thermal-buffer areas that reduce the impact of solar radiation and glare, which in turn affect the energy consumption. In addition, this location can reduce noise and high wind speed penetration. It was found that changing the orientation and the location of skycourts in a simulated model of Mesiniaga tower decreases the energy use in the building (Jahnkassim and Ip 2006).

The number of sides that open up in skycourts influences the thermal comfort of occupants. It was argued that a skycourt with four sides that open up provides more optimum conditions than a skycourt with two sides that open up in summer, and vice versa in winter, in the Hong Kong climate. The higher air speed provides a good thermal comfort in summer, but poor thermal comfort in winter (Mak et al. 2005). Inlet air openings have an impact on the thermal performance of spaces; it affects the airflow and the air distribution. Outlet openings are important to enhance ventilation (Moosavi et al. 2015).

Other studies found that the central narrow form and the rectangular higher length to width ratio are more effective for ventilation than the square shape (Aldawoud 2013; Moosavi et al. 2014).

2.3.4 Summary

A mechanical ventilation system is preferable in high-rise buildings, particularly offices. However, this approach is connected with high energy consumption for cooling or heating the supply air.

Ventilation mechanisms, requirements, air distribution systems, assessment process, and parameters that are commonly adopted for developing ventilation strategies in buildings have been discussed. This provides a theoretical background to define the basic principle of the proposed ventilation strategy in the present study.

The displacement air distribution system is widespread in office buildings due to ventilation effectiveness compared to the mixing system. Spatial and geometric configuration of ventilated spaces influence ventilation effectiveness in these areas. These features comprise orientation, height, area, length, and depth of the space, in addition to air openings inside these spaces. Climate has a great effect on this issue; therefore, ventilation strategies should be investigated in different seasons.

Defining the most effective and efficient ventilation system is considered a difficult task. Energy efficiency and comfort due to thermal conditions and air quality in ventilated spaces are the main indicators for ventilation performance. Therefore, these factors will be explained in detail, in the following section.