tool was introduced by the authorities for potential owners of buildings to facilitate the improvement of energy efficiency of their buildings. However, compliance is on a voluntary basis and it is not currently compulsory for owners of buildings to apply for the Green Building Index. The other issues related to ACMV include the environmental stewardship of the refrigerant used, noise pollution and safety issues during the construction phase.
Design Guidelines and Best Practices
In Malaysia, due to the hot and humid tropical climate, air-conditioning system design is critical in ensuring thermal comfort and providing indoor air quality for the occupants. To achieve this, a reasonably accurate estimation of the cooling load is of paramount importance in ensuring thermal comfort to occupants and maintaining environmental stewardship. To deal with the aforementioned design issues, the ACMV design methodology, equipment selection and specifications have to be in line with good engineering practice, and give due regard to the following criteria:
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Simplicity of design and installation.
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Ease of operation and maintenance.
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Energy efficiency and impact on the environment.
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System flexibility and adaptability.
The following standards and guidelines are generally applicable in the design of an ACMV system:
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American Society for Heating, Refrigerating, and Air Conditioning Engineers( ASHRAE) Standards [ 3 ].
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Malaysia Standard MS 1525:2014 [ 4 ].
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JKR’ s Guideline on Air Conditioning System Design [ 2 ].
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Uniform Building By-Laws.
Malaysia Standard MS 1525:2014 recommends acceptable indoor conditions for comfort cooling to be designed as follows:
( i) Recommended dry bulb temperature = 24 ° C ― 26 ° C.( ASHRAE Standard: 20 ° C ― 24 ° C)
( ii) Recommended relative humidity = 50 % ― 70 %.( ASHRAE Standard: 40 % ― 60 %)
( iii) Recommended air movement = 0.15 m / s ― 0.50m / s.( ASHRAE Standard: same)
The recommended outdoor air condition is 33.3 ° C DB and 27.2 ° C WB as stated in MS 1525:2014.
According to the Jabatan Kerja Raya( JKR) Guidelines for Air Conditioning System Design, engineers have to propose an air-conditioning system according to the cooling load required to serve the peak load of the building. The type of a suitable air-conditioning system should be selected according to Table 1. If a different type of system is selected, it must be justified.
Two common practices for cooling load estimation are:
1. Estimation of cooling load using computer software such as the Carrier E20 programme [ 5 ] with detailed inputs. This approach is commonly applied in large scale projects, in some cases after a client’ s request. Many M & E consultants use their self-developed cooling load spreadsheet which is very similar to E20 but very practical and user friendly.
2. Estimation of cooling load using check figures and rule of thumb [ 6 ] for common buildings and structures. It is often used for the purpose of design verification.
The check figures and rule of thumb approach provides a practical and time-efficient method for industry players. The check figures are especially helpful when it comes to verifying the design of an ACMV system for existing and common buildings and structures. Compliance with the check figures is important in order to avoid over sizing.
When engineers are required to design something that is not listed in the check figures table they need a detailed input from the E20 programme to estimate the cooling load. The check figures are not accurate enough unless the engineers run the E20 programme in detail. The cooling load calculation is based on cooling load temperature difference( CLTD) method. The five
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