From the literature studied, it can be seen that the temperature reduction study among the six literature has several degree Celsius difference from one another. This may take account of many considerations that cause the result come out with the discrepancy. In order to discuss several factors influenced the result to be consistency, 3 key aspects that influenced when studied the evaluation of vertical green system on reduce heat outdoor environment.
First, systems classification is important while made comparison study review by previous studied data. In order to compare research results, the types of system used of vertical green should be clear.
Second, climate influence is one of the biggest factor that affected the result. This is due to the climate conditions will directly affects the thermal performance of the building, and the VGs operation will be influence in term of the specific aspects of plants such like the species, growth rate and plant transpirations.
The plants species has mentioned above is the basis of different typologies of VGs use different plants species, and this fact must be taken into account when studying their thermal behaviour. In Green Walls, herbaceous and shrubs species (occasionally climbing plants) are the most common, usually well adapted to local climatic conditions, and always evergreen.(Gabriel,2014) While for Green Façades, climbing plants are usually used due to they can be evergreen or deciduous, fact that can affect significantly their performance throughout the year, from the thermal point of view.
Furthermore, a study show that the variation in cooling capacity between GWs with three plant species also demonstrates the effect of physical characteristics of vegetation on temperature reduction. It is argued that leaf density or LAI is the key factor in determining the cooling capacity of GWs as it positively correlates to the shading effect of GWs. The results of this experiment show that the plant with the highest value of LAI, C. hyssopifola H.B.K, had the best performance in temperature reduction; however, a plant with an LAI of 3.65, T. urvilleana, performed better than E. cochinchinensis with an LAI of 3.85. This means that LAI cannot be the only factor used to explain thermal performance influences from LW plants. Subsequently, the selection of LW plants for a cooling effect should not focus only on the foliage density but also the leaf size. Plants with a high value of LAI and a small-medium leaf size are the most suitable species for achieving the combined effects of shading and heat loss. (Sasima, 2016)
4.3 Case study
The 6 storeys proposed boutique hostel with waterfront features to Klang River is located at the Kuala Lumpur city centre. According to the climate, location and culture of the design proposal, 3 buildings nearby KL that closest to the design consideration are chosen to compare and find out the closest green façade system that is fulfil the design consideration requirements of the boutique hostel.
The first building Le Nouvel is a high rise Serviced Apartment with two 50 levels tower which located at centre heart of KL. Where the next building Flora by Crossroad Hotel is a low rise building, 5 storeys building with approximate 20 meters height is located at 3-5 minutes’ walk distance from the proposed boutique hostel. The last building chosen, Digi Data centre is 4 storeys height technology operation centre.
The common similarity of 3 buildings with the proposal is they are in tropical climate, which most the time hot and humid weather. At the same time, greenery treatment are chose to apply at the façade of the building.