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LCQ10: Condensation problem caused by the use of air-conditioners in public housing units
     Following is a question by the Hon Paul Tse and a written reply by the Secretary for Transport and Housing, Mr Frank Chan Fan, in the Legislative Council today (October 25):


     Over the past few years, my office received several complaints from residents of public rental housing estates (including Wang Tau Hom Estate, Upper Wong Tai Sin Estate, Lower Wong Tai Sin Estate, Lok Wah (North) Estate, Lok Wah (South) Estate, Lower Ngau Tau Kok Estate and Tak Tin Estate), members of the owners' corporations of some Home Ownership Scheme courts and representatives of property management companies of some housing estates, which are located in Kowloon East.  They suspect that there are design defects in the prefabricated building components used in public housing (e.g. the air-conditioner hoods are very close to the ceilings of the units).  When the air-conditioners in those units have kept running for a long time, the temperature of the floor of the units on the upper floor will drop below the indoor temperature, thus causing condensation on the floor of the units on the upper floor (condensation problem).  It has been reported that some elderly residents slipped and fell due to the slippery floor of their units and were sent to hospital for treatment.  Mouldy and deformed flooring as well as electricity leakages from electrical appliances have also occurred in some units.  The problem showed no improvement even though the residents concerned have adjusted, on the instruction of the Housing Department, the direction of the air vanes at the air outlets of their air-conditioners.  In this connection, will the Government inform this Council:

(1) of the number of complaints involving condensation problem received by the authorities in each of the past five years;

(2) of the other actions, apart from issuing advisory letters to residents causing condensation problem to the units on the upper floor, that the authorities have taken to follow up such complaints;

(3) as some residents and veteran members of the construction industry have alleged that the inherent design defects in the prefabricated building components used in public housing (e.g. the air-conditioner hoods being too close to the ceilings or the floors, and the floor slabs being too thin) have caused condensation problem in various housing estates, whether the authorities have conducted an analysis on the differences between private residential buildings and public housing in terms of the positions of the air-conditioner hoods as well as the thickness of and the materials used in the floor slabs, and whether such differences have led to the more frequent occurrence of condensation problem in public housing than in private residential buildings; if so, of the details; if not, whether the authorities will conduct the relevant analysis immediately;

(4) given that the Chief Executive has, in her recently delivered Policy Address, recommended to regularise the Green Form Subsidised Home Ownership Pilot Scheme (GSH), whether all of such housing will be constructed using prefabricated building components; whether the authorities will study ways to revise the design of the prefabricated building components, such as thickening the floor slabs as well as widening the distance between the air-conditioner hoods and the floor slabs, so as to prevent condensation problem occurring in GSH units completed in future; if no such study will be conducted, how the authorities ensure that condensation problem will not occur in the relevant units; and
(5) as the Secretary for Development has, after his visit to Guangdong in August this year, indicated that the Government was studying the introduction of the construction technique of "modular construction" with an aim of speeding up public housing construction, whether, in view of the prefabricated building components being alleged to have design defects, the authorities have plans to improve the design of and the materials used in the prefabricated building components before introducing the technique, so as to avoid the occurrence of condensation problem?



     Having consulted the Development Bureau, a consolidated reply to various parts of the question raised by the Hon Paul Tse is as follows:

     Generally speaking, the problem of moisture condensation occurs under various circumstances and conditions.  For example, if there is a substantial difference in temperature between the flat using air-conditioning and the flats on its upper or lower adjacent floors, the flat with a higher room temperature will be prone to moisture condensation at its floor or ceiling.  This situation is also more likely to occur in weather with relatively high humidity.
     As regards the complaints on condensation problem from residents of public rental housing (PRH) units under the Hong Kong Housing Authority (HA), estate offices of the Housing Department (HD) will arrange staff to inspect the affected units and the lower floor units after receiving complaints, and encourage tenants to take various improvement measures, such as adjusting the air louver of the air-conditioner to a horizontal or downward facing angle, setting the air-conditioner to a higher temperature, setting the operation mode to air swing for a uniform cooling effect, shortening the usage time of the air-conditioner, using substitute products such as electric fans or, exhaust fans etc., and maintaining good indoor ventilation for lowering the temperature and minimising the temperature difference between the upper and lower floor flats, with a view to mitigating the condensation problem.  At the same time, HD staff will suggest the affected tenants to open windows, turn on electric fans, exhaust fans, dehumidifiers or air-conditioners at suitable times in order to regulate room temperature and humidity.  Most condensation problems can be resolved by the cooperation among neighbours.
     Before summer, HA will also post notices in PRH estates and issue estate newsletters to remind tenants to use their air-conditioners properly.  Besides, HA will disseminate such information through Estate Management Advisory Committees, Mutual Aid Committees, estate offices and property management companies, with a view to enhancing tenants' understanding of this problem.

     In the past five years, the number of complaint cases on condensation problem in PRH estates under HA is as follows:
Year 2013 2014 2015 2016 2017
(up to Sep 30)
Number of cases 1 030 1 140 1 990 2 860 3 000
     Member's question mentions about the relationship between precast units design and condensation problems in some estates.  As a matter of fact, apart from Lower Ngau Tau Kok Estate which adopted precast floor slab, all other estates mentioned in the question adopted another construction method (i.e. in-situ concreting for floor slabs).
     HA has all along been improving the design and construction of public housing developments.  HA will take on board views collected from residents' surveys as well as suggestions from other stakeholders on such design and construction.  HA will also study the use of new technologies or materials, including the unit prefabrication technology.
     The design of floor slabs for HA's public housing developments (including PRH, Home Ownership Scheme or Green Form Subsidised Housing developments) is essentially the same as that of private housing developments in the sense that both must comply with the relevant regulations and Codes of Practice (CoPs) such as Building (Construction) Regulations, CoP for Fire Safety in Buildings, CoP for Structural Use of Concrete, CoP for Precast Concrete Construction, etc.  Thickness of floor slabs is designed on the basis of the requirements of their span length, loading and fire protection.  In terms of construction works, HA has over 20 years of experience in using precast concrete slabs.  Such technology has also been widely adopted by the construction industry in Hong Kong for many years.  The construction of precast slab has to comply with the above-mentioned CoP for Precast Concrete Construction published by the Buildings Department.  Therefore, there is no difference between the structural quality of precast and in-situ concrete slabs.
     HA has all along been taking a proactive approach to incorporate suggestions from various stakeholders on the design and construction methods of public housing developments.  For example, since 2015, HA has enhanced the Modular Flat Design and increased the floor-to-floor headroom from 2 700 mm to 2 750 mm.  In response to residents’ needs, the air conditioner platforms in the living rooms have also been enlarged to 750mm wide and 680mm high. 
     In recent years, Hong Kong has been beset with the challenges of high construction cost and shortage of labour.  Therefore, the Government has been proactively promoting wider adoption of advanced technology and innovative construction methods to enhance productivity and cost-effectiveness.  Following the earlier visit to Guangdong by the Secretary for Development and the Secretary for Transport and Housing, the Government indicated that we would consider introducing Modular Integrated Construction (MiC) in Hong Kong by promoting and leading the adoption of MiC in the construction industry through pilot schemes in public projects.  The Innocell project and the student residences project of the University of Hong Kong at Wong Chuk Hang are pilot projects which are now under planning and design.
Ends/Wednesday, October 25, 2017
Issued at HKT 14:55
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