Sustainable Building Services Design

for Affordable Social Housing in Hong Kong

Ir. C.K. LEUNG Senior Building Services Engineer Hong Kong Housing Authority HKSAR, China ck.leung@housingauthority.gov.hk

Senior Building Services Engineer, Ir. Stanley W.K. TANG, Hong Kong Housing Authority, HKSAR, China, waikuen.tang@housingauthority.gov.hk Building Services Engineer, Ir. Roger Y.K. LEUNG, Hong Kong Housing Authority, HKSAR, China, roger.leung@housingauthority.gov.hk

Summary The Hong Kong Housing Authority (HA) develops and implements a public housing programme which seeks to achieve the Hong Kong Government's policy objective of meeting the housing needs of people who cannot afford private rental housing. Approximately 30% of the Hong Kong population is now living in public rental housing units. The HA plans, builds, manages and maintains different types of public housing, including rental housing estates, interim housing estates, and transit centres. In addition, the HA owns and operates some flatted factories and ancillary commercial and other non-domestic facilities. In the context of public housing development, the missions of the HA are to provide affordable quality housing and other housing related services to meet the needs of the customers in a proactive and caring manner; and to ensure cost-effective and rational use of public resources in service delivery and allocation of housing assistance in an open and equitable manner. This paper will focus on some of the measures that realize quality living in affordable social housing through sustainable building services designs to achieve enhanced cost-effectiveness, usability, reliability, maintainability, environmental friendliness and social responsibilities. Keywords: sustainable, housing, building services, design, renewable, energy, carbon emission

1. Public Housing in Hong Kong In 1953, a serious fire in Shek Kip Mei squatter area marked the beginning of the government’s involvement in the construction of multi-storey resettlement buildings. To cope with the increasing needs of housing in the territory at that time, the then Public Works Department built Government Low-Cost Housing in the 1960s for low income families. To address the accommodation need of a sharply increasing population, the Government announced the Ten-year Housing Programme in 1972. The Hong Kong Housing Authority (HA) was established in 1973 to oversee public housing issues of Hong Kong. Currently about 30% of the total Hong Kong population lives in public rental housing units. The Housing Department (HD) is the executive arm of the HA to discharge her statutory responsibilities which include, inter alia, the provisions, operation and maintenance of building services installations for public housing.

2. The Missions of the Hong Kong Housing Authority

The mission of the HA is to provide affordable quality housing and other housing related services to meet the needs of the customers in a proactive and caring manner. It is also to ensure cost-effective and rational use of public resources in service delivery and allocation of housing assistance in an open and equitable manner. The four core values of the Authority, viz. Caring, Customer-focused, Creative, Committed (the 4 C’s) are manifested in the continuous pursuit of improvement of the design and provision of building services installations at public housing estates to achieve enhanced cost-effectiveness, usability, reliability, maintainability, environmental friendliness and social responsibilities. We provide affordable quality housing incorporating sustainable considerations to balance the economic, social and environmental needs and concerns of our stakeholders in housing development and management programmes in pursuit of performance excellence and harmonious living environment.

3. Building Services Installations - an Indispensable Element for Quality Housing

While the mission of the HA is to provide quality housing, quality building services installations are integrated and indispensable to meet this mission. In a densely populated metropolis like Hong Kong, public housing buildings are, without exception, reaching out for the sky to compete for as much space as possible. Today, a typical public housing building would be a 41-storey high-rise building accommodating several hundred residential units. In the context of quality building services designs for high rise domestic buildings, all factors including safety, usability, reliability, maintainability, cost-effectiveness, environmental friendliness, rational use of public resources and social responsibilities have to be carefully considered and balanced before coming up with a design.

4. Design for Sustainability Energy conservation in Hong Kong has received increasing attention over the years. This is a crucial element in sustainable development and helps combat global warming. As a general design principle, all the building services installations are designed to achieve a high level of energy efficiency. Moreover, we have made it mandatory that all new building services designs shall fully comply with the requirements of Hong Kong’s Building Energy Codes since their first promulgation more than a decade ago. The compliance of the Codes is only made mandatory in 2011. Today, we have received over 300 energy certificates covering various building services systems including lift and escalator, air-conditioning, electrical and lighting installations. Over the years we have been exploring into various technological fronts of system designs and equipment efficiency in a bid to improve customer satisfaction as well as further reducing our buildings’ carbon footprints. In this paper, we will find detailed delineations of our recent efforts in achieving our sustainable design objectives through the exploration and adoption of green engineering initiatives. These include green lighting design; energy efficient building services equipment, renewable energy, hygienic refuse handling, hybrid ventilation, improved water supplies, water conservation, uninterrupted lift service, carbon emission estimation and energy audits. 4.1. Green Lighting Design As lighting energy forms a substantial part of the total energy consumption of a building, energy efficient fluorescent lamps have been used extensively in our building projects. We have been working closely with lighting suppliers and conducting trials to source luminaries and lamps of higher efficacy that can suit our applications. The design principle is to deliver the required levels of lighting performance in terms of illuminance, uniformity, colour rendering and glare, yet cost-effective and easy to maintain, while complying with the relevant statutory requirements.

In 2008, the new edition of Design Manual for Barrier Free Access was released which has presented great challenges to building services engineers. The manual specifies a minimum illumination level of 85 lux along communal passageways in buildings to take care of persons with special needs. When compared with our original design illumination level of 50 lux, the adoption of the new requirements would lead to almost doubling the communal lighting energy consumption and hence associated CO2 emission. To reduce the environmental impact of the new design requirement, a new lighting control system allowing two levels of illumination was developed in 2009. The new design comprises two sets of lightings provided along the communal passageways (Fig. 1). One set is constantly powered to provide a minimum illuminance of 30 lux at floor level for typical corridor and staircase and 50 lux for typical lift lobby. The other set is normally switched off as standby. With different means of control, the resultant illumination level could be raised to 85 lux by switching on those standby lightings for an adjustable period (e.g. 10 minutes) as depicted below – (a) For tenants coming out from lift cars on their way to their flats, they can simply press the

manual switch in the lift lobby to turn on the standby lightings in the lift lobby area, and then press another manual switch at the entrance of corridor to turn on the standby lighting in the corridor to lit their ways to their flat units.

(b) Tenants coming out from staircase can use the manual switches provided at each entrance of staircase to turn on the necessary lighting on their way to the designated flat units.

(c) For tenants coming out from their flats, they can turn on the standby lighting of the corresponding corridor and lift lobby by pressing the designated button on their doorphone handsets in their flat units.

(d) For the control of staircase lighting, a motion sensor will be provided on each standby lighting fitting to turn itself on upon detecting any person entering the covered zone.

Avoiding prolonged holding of the standby lighting along a corridor at the ON condition, the system would time out the lighting of the triggered zone after a pre-set lapse of time. Lighting in the vicinity of windows is controlled by timers and photocells to achieve greater and effective use of daylight. By adopting the new lighting control system, it is estimated the HA can help reduce 86 tons of CO2 emission per domestic block per annum.

P

P

P

P

P

LEGEND

P MANUAL PUSH BUTTON

LIGHT FITTING TO PROVIDE

BASIS ILLUMINATION LEVEL

LIGHT FITTING TO ELEVATE THE

ILLUMINATION LEVEL TO 85 LUX

Fig. 1 - Typical Domestic Floor Lighting Layout Plan

4.2. Exploring the Use of Energy Efficient Equipment Keeping pace with the use of new technologies, the HA has been conducting trials on the use of more energy efficient building services installations. Our aim is to apply these energy efficient measures on a wider scale into new housing projects. (a) Previous trials include compact fluorescent lamps (Photos 1a & 1b), photocell sensor controls (Photo 2), the wider use of electronic ballasts (Photo 3), T5 fluorescent tubes, nano reflectors, LED/self-luminous exit signs and solar/wind powered lightings. Most of these initiatives have been included into our lighting design provisions for general applications.

Photos 1a & 1b - Compact Fluorescent Staircase and Corridor Light

Photo 2 –Photocell Sensor Control Photo 3 – Electronic Ballasts

(b) VVVF (Variable Voltage Variable Frequency) drives and high efficiency permanent magnet gearless traction systems (Photos 4a & 4b) are being used in lift installations to reduce energy losses.

Photo 4a - Gearless Lift Traction Machine Photo 4b - Lift Control Panel using VVVF Drive

4.3. Promoting the Use of Renewable Energy Renewable Energy (RE), based on inexhaustible natural resources, includes solar light, wind power, biomass, geothermal, wave action, hydro and tidal power, etc. Among the alternatives, the potential of harnessing solar and wind energies is higher for Hong Kong’s environment. While understanding that, based on today’s RE technologies, the cost effectiveness of harnessing and applying solar or wind power to generate electricity is still low; nevertheless, HA has endeavoured to try out these emerging technologies in some of our residential blocks and commercial centres as well as external areas in a bid to evaluate its effectiveness and prepare ourselves in readiness for wider application of these technologies in the future. (a) PV Power Generation System Echoing the government’s initiatives and policies for sustainable development, we have completed a renewable energy pilot project in the form of a grid-connected photovoltaic (PV) system for the redevelopment of Lam Tin Estate Phases 7 and 8. The PV system provides part of the electricity consumed by the building’s common facilities, in turn reducing the demand for electricity from the power company. The system converts sunlight directly into electricity. Approximately 248 m2 of mono-crystalline silicon PV panels, chosen for their high energy conversion efficiencies, have been installed on the roofs of three residential blocks and part of the covered walkway of the development. Maximising power generation, the PV panels have been carefully sited to take the daily intensities of sunlight, as well as the shade cast by nearby buildings, into account (Photos 5 and 6).

Photo 5 - PV Panels Photo 6 - BIPV Panels as Skylights

In addition to the conventional electrical power supplied by the power company, the PV system is connected directly to the building’s power distribution network as a secondary power source. The grid-connected design obviates the need for power storage batteries, resulting in lower installation and maintenance costs and, more importantly, the elimination of adverse environmental effects caused by the disposal of rechargeable batteries. With a capacity of 33 kW, the electricity generated is conditioned and fed into the building power supply system for immediate use within the common areas, for corridor lighting, lifts, water pumps, etc. The annual electrical power contributed by the system is estimated to be 32,300 kWh, around 8% of the annual electricity required for the common facilities in one residential block. (b) Renewable Energy Powered Lighting Aiming to promote energy savings and educate tenants at the same time, we have installed a small number of solar and wind power lighting systems in new estates (Photos 7 & 8) together with a few Solar Energy Generation Systems in estates where the situation allows.

Photo 7 – Vertical Axis Wind Turbine Photo 8 – Hybrid RE Powered Light Poles

(c) Solar Water Heating System Further promoting the use of solar energy, a solar water heating system has been incorporated as a trial in a large commercial centre in Yau Tong Phase 4 project scheduled for completion in 2011. It comprises two sets of vacuum tube type solar water heater, one storage type electric water heater (providing supplementary heating during cloudy sky conditions or night time), connecting pipework and a thermostatic mixing valve. The system will provide hot water supply to a baby care room. It is estimated to save 3500 kWh of electricity, equivalent to an annual reduction of 2450kg of CO2 emission. 4.4. Hygienic Refuse Handling Enhancing health and hygiene in our public housing estates, we have been providing two types of cost effective refuse handling systems for public housing developments completed since 2005. These two systems, the Central Compactor System (CCS) and Distributed Compactor System (DCS), have been designed to cater for the refuse handling needs of estates with diverse populations. CCS is used in estates with a daily refuse output of 5 tons or more. The Food and Environmental Hygiene Department (FEHD) then arranges for a special truck to collect the sealed refuse storage containers. In estate where the population is lower and where the daily refuse output is less than 5 tons, DCS is used with FEHD collecting the refuse by conventional Refuse Collection Vehicles (RCV). (a) A CCS comprises the following major components (Fig. 2) – 1. A storage chamber with motorised gates connected to the bottom of refuse chutes in each domestic block correctly controls the volume of refuse loaded into each 660-litre (660L) refuse storage bin before transportation to the refuse collection point (RCP). 2. A central refuse compactor inside the RCP receives and compacts the refuse from the 660L storage bins to one-third its original volume for storage in sealed refuse storage containers. 3. The sealed refuse storage container, designed for quick loading onto the FEHD collection vehicle, is transported to a refuse transfer station or landfill. (b) A DCS consists of a small-scale compactor connected to the bottom of each refuse chute to automatically compact the refuse received to half its original volume and to partially squeeze out any waste liquid before loading the refuse into a 660L bin for subsequent removal to the RCP for storage (Fig. 3).

Fig. 2 -Central Compactor System (CCS)

Fig. 3 - Distributed Compactor System (DCS)

4.5. Adoption of Energy Efficient Hybrid Ventilation System Centralised air-conditioning systems are commonly used in Hong Kong’s shopping centres to provide a comfortable environment for tenants and shoppers. However, they also consume large amounts of energy. According to the latest energy end-use survey released by the Electrical and Mechanical Services Department, the energy used for space air-conditioning accounted for around 37% of the total energy consumed in retail buildings in 2008. It is therefore essential to adopt innovative methods to reduce the consumption of this energy. At the same time, with the cooler and drier weather experienced in autumn and winter, the demand of air-conditioning falls and natural ventilation is more than sufficient to provide a pleasant and comfortable environment. Hybrid ventilation systems are therefore ideal – with a suitable design and control algorithm to

Central Compactor System

switch the air conditioning system into natural ventilation mode, substantial savings in energy can be achieved. We therefore installed our first hybrid ventilation system in the shopping centre at our Eastern Harbour Crossing Site Phase 6, which was completed in 2010. This hybrid system provides three operating modes – natural ventilation, free cooling (fan-assisted) and air-conditioning. The hybrid ventilation modes will be controlled and monitored by a Central Control and Monitoring System (CCMS) by continuously comparing the indoor and outdoor environmental conditions. Temperature and humidity sensors in the public circulation zone monitor indoor conditions whilst an anemometer, rain sensor and outdoor air temperature sensors monitor outdoor conditions. When outdoor temperature and humidity levels satisfy design conditions based on internal thermal comfort criteria, the natural ventilation mode comes into operation and automatic windows are opened. If the outdoor air conditions do not meet the pre-set thresholds, either the free cooling or air-conditioning come into play. 4.6. Uninterrupted Water Supply - Twin Roof Water Tanks In the past, regular interruption of water supply was inevitable due to periodic cleansing of water tanks as required by legislation. Twin roof water tank design was developed jointly with the Water Supplies Department of the Hong Kong Government to provide uninterrupted water supply to tenants and foster a more user-friendly living environment. As the name implies, the roof water tanks are divided into two tanks each with individual inlet, outlet and level control devices (Fig. 4). One of the twin tanks can be plugged off for cleansing or repair whilst the other tank continues to provide uninterrupted water supply to tenants at all times. When compared to the single roof water tank configuration, the twin-tank design has provided three distinct advantages during cleansing of the water tanks: (a) uninterrupted water supply to the tenants; (b) elimination of possible contamination of water supply to the tenants; and (c) reduction in water wastage during tank cleansing. Though technically feasible, implementation of such innovative design would not be made possible without the agreement of Water Supplies Department (WSD). Working towards the common goal of achieving quality living, WSD issued Circular Letter No. 4/2007 to give a green light to the implementation of twin roof water tank design. The amended waterworks requirements enable the adoption of twin water tank supply to not just housing estates, but the whole territory. The first HA’s project with twin-tank design was completed in May 2009.

Fig 4 - Twin Roof Tank Schematic Photo 9 – Pressure Tanks

4.7. Improved Fresh Water Pressure and Energy Efficient Pumping Design Indirect fresh water supply system is commonly used for high-rise buildings. Fresh water from town mains is pumped to the roof storage tank and then supplied to tenants by gravity. In the past, there were complaints from our tenants living on the top floors about “low” water pressure. The

complaints might be caused by unstable operation of their gas water heaters due to high pressure loss of the water mixers and shower heads; or the tenant’s desire for a “stronger” water stream. With a view to ensuring customer satisfaction, a fresh water booster pump system comprising centrifugal water pumps and pneumatic pressure vessels was introduced a decade ago. The minimum fresh water supply pressure at the cold water inlet of gas water heater has since been increased to 1.7 bar (Photo 9). With the advance of technology we see opportunity for further improvement. We have just completed a study on the application of Variable Frequency Drive (VFD) for the booster pumps with success. By varying the speed of the pump motor, the energy-efficient VFD can respond quickly and efficiently to the varying water demand by maintaining a stable water supply pressure at the draw-off points under all operating conditions. Moreover, the number and capacity of pneumatic pressure vessels can be substantially reduced, reducing plant space requirement. From now on, this new design feature has been incorporated for all our new fresh water booster pump systems. 4.8. Uninterrupted Lift Service As a statutory requirement, periodic inspection, testing and certification (PITC) for electrical

installations in residential blocks is required. During the process, power supply to the lifts and thus

lift services is inevitably disrupted (Fig. 5). This is particularly inconvenient to the elderly and

physically challenged tenants living in a high-rise building of 40 storeys or more. To alleviate the

incovenience to them while complying with the statutory requirement, we have developed an

enhanced system so that minimum lift services can still be maintained during PITC of switchboard

cubicles.

In the new design, power supply to the lifts is

supplied from two separate supply

switchboards instead of one. Each of these

lift supply switchboards is fed from both the

general supply and the essential supply

through automatic changeover contactors

(Figs. 6 & 7). With such arrangement,

maintenance of these two separate lift supply

switchboards can be carried out alternately.

Fig. 5. - Original Design (Maintenance Mode)

Fig. 6. – New Design (Maintenance Mode 1) Fig. 7. - New Design (Maintenance Mode 2)

4.9. Energy Audits

In 2010, we conducted energy audits on six strategically selected domestic blocks to identify

potential energy management opportunities (EMOs) of the major communal energy consuming

systems. Apart from the formulation of energy management plans which are applicable to similar

types of our existing housing stock, the recommendations of the audits also help validate the

sustainable design approaches currently adopted in our new buildings for better energy utilisation. In order to compare the energy performance of different types of standard domestic blocks built in

the last few decades by HA, the selected block types comprising one Cruciform Block (1977), one

Double H Block (1980), one Harmony 1 with Annex Block (2001), two NH1 Option 6 Blocks (2008)

and NH1 Option 6 with Annex Block (2008) represent a typical portfolio of our housing stock.

Through the collection of historical operation data, energy bills, in-situ measurements and surveys,

detailed evaluation of the installed building services equipment and comprehensive analysis of

yearly energy consumption data, we have successfully identified the major communal energy

consuming systems of these domestic blocks and their respective potential EMOs. The EMOs

recommend replacing conventional ballasts with electronic ones, T8 florescent tubes with T5 and

conventional motors with higher efficiency models, for those blocks built in or before 2001.

4.10. Carbon Emission Estimation (CEE)

Recently, the HKHA has taken a further step in devising a carbon emission estimation methodology

to gauge at design stage the holistic carbon emission of new public housing developments. The

methodology focuses on the major aspects of construction materials and building operations which

have implication on carbon emission, reduction and absorption from cradle to grave for a building

life of 100 years.

Six aspects of construction materials and processes have been identified in the methodology (Fig.

8) : (1) Materials Consumed during Construction, (2) Building Structure, (3) Communal Building

Services Systems, (4) Renewable Energy, (5) Planting and (6) Demolition. For Aspects 1 and 2,

the materials include concrete, reinforcement bars, steel formworks and timber formworks. For

Aspect 3, the electricity consumptions of all communal building services systems are considered.

For Aspects 4 and 5, carbon reduction by renewable energy, say grid-connected PV system, and

carbon absorption by trees taller than 5m are taken into account. For Aspect 6, the energy for

building demolition and transportation of debris to landfill site is considered. Carbon Emission

figures of our standard New Harmony One Block and the latest buildings in our new public housing

development at Kai Tak Site 1A have also been estimated and adopted as benchmark figures for

new design blocks. This CEE methodology is a useful design verification tool for controlling carbon

emissions due to the embodied energy of construction materials and building structure and the

operational energy of building services systems at design stage.

Fig. 8. Methodology for Carbon Emission Estimation

5. Conclusion The above is a concise delineation of our recent efforts and results in ensuring quality living in affordable social housing through quality building services designs. Though we foresee unprecedented challenges ahead in our development of building services installations, yet with our pursuit for sustainability excellence, we are confident that, with the joint efforts and support of stakeholders, we can create new platforms for sustainable building services designs.

6. References [1] Building Department, HKSAR Government, 2009, Design Manual - Barrier Free Access 2008 [2] Electrical and Mechanical Services Department, HKSAR Government, 2010, Hong Kong

Energy End-use Data 2010 [3] Hong Kong Housing Authority, 2010, Annual Report 2009/10 [4] Hong Kong Housing Authority, 2010, Sustainability Report 2009/10 [5] Water Supplies Department, HKSAR Government, 2007, WSD Circular Letter No. 4/2007 [6] Electrical and Mechanical Services Department, HKSAR Government, 2009, Code of

Practice for the Electricity (Wiring) Regulations [7] Environmental Protection Department, HKSAR Government, 2010, Guidelines to Account for

and Report on Greenhouse Gases Emissions and Removals for Buildings (Commercial, Residential and Institutional Purposes) in Hong Kong

[8] Electrical and Mechanical Services Department, HKSAR Government, 2007, Guidelines on Energy Audit