2 

The Proposed Heating and Cooling System in the CH 
Building and its Impact on Occupant Productivity 
Lu Aye and Robert James Fuller (University of Melbourne) 

ABSTRACT 

Melbourne's climatic conditions demand that its buildings require 
both heating and cooling systems. In a multi-storey office building , 
however, cooling requirements will dominate. How the internal 
space is cooled and ventilation air is delivered will significantly 
impact on occupant comfort. This paper discusses the heating 
and cooling systems proposed for the CH2building. The paper 
critiques the proposed systems against previous experience, both 
internationally and in Australia. While the heating system employs 
proven technologies, less established techniques are proposed 
for the cooling system. Air movement in the shower towers, for 
example, is to be naturally induced and this has not always been 
successful elsewhere. Phase change material for storage of 
"coolth" does not appear to have been demonstrated previously 
in a commercial building, so the effectiveness of the proposed 
system is uncertain. A conventional absorption chiller backs up the 
untried elements of the cooling system, so that ultimately occupant 
comfort should not be compromised . 

Keywords: heating, cooling, occupant productivity, performance, 
thermal comfort. 

INTRODUCTION 

The heating and cooling of buildings has a long history. Active 
heating systems began with cave dwellers, who lit open fires for 
warmth and light in their rock caverns. More advanced heating 
systems were adopted by civilizations such as the Romans, who 
operated furnaces below their buildings and ducted the hot gases 
to upper level rooms to provide warmth. The hypocaust, as it 
was known , has found a modern day equivalent in the form of 
advanced fabric energy storage systems such as the Termodeck™ 
system. The provision of cooling in buildings has always presented 
designers a greater challenge. Early cooling systems made use of 
natural draft and evaporative effects, and this knowledge is being 
revisited today as building designers strive to provide cooling that 
does not incur a heavy environmental cost. 

Heating and cooling systems have become obligatory in most 
modern office bu ildings. Aside from issues of occupant comfort 
and expectations, some believe that the productivity of workers 
is related to the temperature and humidity of their working 
environment. A new commercial building, currently under 
construction in Melbourne, Australia, is hoping to demonstrate 
that it is possible to achieve a high quality office environment 
simultaneously with much reduced energy consumption. CH 
is in the heart of the city's central business district. This study 
assesses whether the heating and cooling system proposed for 
the CH2building provides the necessary thermal conditions for its 
occupants. This study begins with an overview of the requirements 
for thermal comfort in terms of temperature, humidity and air 
movement. The heating and cooling system proposed for the 

CH2building is then described and evaluated in terms of previous 
experience, both in Australia and overseas. Finally, the thermal 
conditions likely to be created within the CH2building are briefly 
reviewed against the current research literature on productivity. 
Since the office is still under construction, no measured data 
from the building is available to verify performance. Therefore the 
proposed design has largely been evaluated using a selection of 
the design consultants' documentation and refereed literature in 
international journals. As the building is still being constructed, 
design changes made subsequent to this evaluation are obviously 
not considered. 

THERMAL COMFORT 

While the human species can tolerate extremes of temperature 
for prolonged periods of time, this is not the choice or expectation 
of today's office workers who will tolerate a much smaller range 
of thermal environmental conditions (temperature, air velocity 
and relative humidity). A widely accepted definition of thermal 
comfort is "that state of mind that expresses satisfaction with the 
thermal environment" (ASHRAE, 1992). Many factors (physical , 
physiological, and psychological) determine whether an individual 
perceives their environment to be comfortable. The purpose 
of any conditioning system is to create the local environment 
that will minimize feelings of thermal discomfort. In general, this 
means maintaining the body temperature within a certain narrow 
range with low skin moisture content. The ASHRAE Standard 55 
"specifies conditions or comfort zones where 80% of sedentary or 
slightly active persons find the environment thermally acceptable." 
Summer and winter clothing levels are assumed to be 0.5 and 
0.9 clo respectively (1 cio is equal to overall equivalent thermal 
resistance, R value of 0.16 m2C/W). For a woman, the summer 
clo value is the equivalent of wearing a knee length skirt, a short 
sleeved shirt, panty hose and sandals, while for a man, the winter 
clo value is roughly the equivalent of wearing a suit with a short 
sleeved shirt. 

The boundaries of the comfort zones can be expressed as a 
function of operative temperature and the relative humidity (RH) 
of the surrounding air. As a result, the comfort zones in summer 
and winter are defined by two quadrilaterals superimposed on a 
psychrometric chart, as shown in Figure 5 of ASHRAE (2001). 
Broadly interpreted , in winter a range of 20-24.5°C and 85-20% 
RH can be tolerated. As the temperature rises , the RH must be 
lowered to maintain thermal comfort. A similar picture is evident 
in summer, but with an extended range, based on the assumption 
that the occupants will wear lighter clothing. Thus in summer, the 
thermal comfort range varies from 22.5-27°C with corresponding 
RH levels of 80% and 20% respectively. There is a small overlap 
between summer and winter zones. In the middle of each of the 
zones, a person would experience their environment in a neutral 
way, but at the boundaries sensations of slight warmth or coolness 
would occur. 

32 The Australian Journal of Construction Economics and Building [VoI5, No 2] 



- -

The above boundaries may be extended if the building relies on 
the adaptive response of its occupants. The theory, advanced 
by researchers (e.g. de Dear and Brager, 2001) is that building 
occupants will adapt their behaviour, based on surrounding 
conditions, and hence tolerate wider extremes in a building's 
internal environment. The expanded comfort zones should result 
in energy savings. These ideas are particularly suited to buildings 
such as CH2, which use a range of non-conventional technology 
and where natural ventilation might also be used. The designers 
of the CH2 building, however, have proposed a climate-controlled 
office, rather than an adaptively controlled one, principally because 
they do not believe it would be feasible to open windows during 
the day due to the building's inner city location. The heating and 
cooling system of the CH2 building has been designed to maintain 
office air temperatures in the range of 21-250C and provided this 
is achieved with acceptable levels of relative humidity, the building 
should satisfy most occupants in terms of thermal comfort. 

Air movement is important in a closed environment for a number of 
reasons. These include replenishment of oxygen and the removal 
of odours, but air movement is not essential for thermal comfort, if 

Evaporative cooling lowers 

UHU UUH 

-

a thermally neutral environment is provided in terms of temperature 
and relative humidity. For air speeds of 0.25 ms·1or less, thermal 
acceptability is unaffected in neutral environments (Berglund and 
Fobelets, 1987, cited in ASHRAE, 2001). 

HEATING AND COOLING SYSTEMS 

The main hardware components of CH 2's conditioning system are 
shown schematically in Figure 1. Thermal modelling by consultants 
of the CH2 building indicated that heating should not be required 
(AEC, 2003b). The passive design principles adopted plus the 
heat generated by the people, equipment and lights have been 
predicted to produce a cooling load even in winter, rather than a 
demand for heating1. However, the fresh air introduced into the 
building via the displacement ventilation system will need to be 
heated on days when the outside air temperature is below 20°C. 
For this reason and to cover any direct heating requirements, a 
heating system is to be installed, which uses exhaust heat from the 
co-generation plant. 

Shower towers 

Phase chan ge materia l 
heat store 

-
Conditioned air 
to occupied space 

Radiant cooling panels Absorption chiller 
Boilers and Cogen -

un it 

(source: Kenton , 2004) 

Figure 1: Schematic of early heating and cooling system originally proposed for the CH 2 building 

The cogeneration system, using a gas-fired micro-turbine, will 
produce electricity for the CH2 building. It has been estimated 
that approximately 1OOkW of the heat generated by the plant will 
be recovered and used either for direct heating or to drive the 
vaporization process in the absorption chiller. Despite the potential 
to operate with a high overall efficiency (85-90%), the use of small 
combined heat and power (CHP) systems in buildings is relatively 
new. Alanne and Saari (2004) have reviewed the status of small­
scale CHP systems for this application. In their assessment of 
micro-turbines, high costs and low electrical efficiency, particularly 
in the part-load condition , are the main disadvantages of the 
technology. Their low noise, weight and vibration level, and small 
space requirements are the main advantages. In a comparison 
with other small CHP technologies, namely fuel cells, reciprocating 
and Stirling engines, gas micro-turbines were not considered to be 

the most technically compatible with office buildings. Reciprocating 
engines and fuel cells were considered to be superior. According to 
a government funded study in Australia, small (up to 300kW) high­
speed reciprocating gas engines were likely to be the most efficient 
and financially viable way to provide power and heat to buildings 
(SKM, 2001). 

In the CH2 building , heat will also be recovered from the air 
exhausted from the offices using a heat exchange system. It has 
not been possible to assess the heat recovery system, since no 
details have been made available. However this is a conventional 
technology and should work effectively if properly designed and 
operated. Waste or recovered heat will be distributed into each 
level by finned convective heaters "set into the floor near the 
windows" on the north and south sides of the building . The concept 

1 The energy required annually for space and water heating for most of a surveyed 31 commercial buildings in Melbourne was found to be between 130-310 MJ 
m-2 (PGA, 1997), so this modelling prediction may be overly optimistic. 

The Australian Journal of Construction Economics and Building [VoIS, No 2] I 33 



is that the warm air from these heaters will create "a barrier of 
warmth around the external walls to prevent the cold air coming 
in" (AEC, 2003d). Assuming that some convective heating of the 
inside surface of the window also occurs, the adverse radiant effect 
of cold windows will also be reduced . 

For much of the year, the design simulations indicate that cooling 
will be required. During the daytime, it is proposed that chilled 
beams and ceiling panels provide cooling for the occupants in 
the main office zones (Figure 2). The intention is that the cooling 
and 'shower' towers will primarily produce the cool water for 
these panels at night. This 'coolth ' will be stored in phase change 

piped la ~.e change f I 
plant lot r.-cooling 

.... 19degC 
16de C 'liliiii .......... • ' • .. I- .... " .... ,. .................... ,. 


.. ...g............ IJ... .. .. .. .. .. .... .. ...... ........................... . 

piped from ~.e change
plant 

thermal mass 
Passive coofing: 
thermal mass in 

concrete slab dur­

ing daytime absorbs 

excess heal from llie 

space. 


chilled ceilings ----+ -t---O 
Active coo~ng: 
chilled c ..~ing panels 
absorb radiated heat 
frem equipment and 
occupant • . 

Radiant cooling d... 

seends into the worl<· 

space at areund 18 

deg C. 


COOLING - OFFICES 

(Source: CoM, 2004) 

material (PCM) and used to chill the water circulated through the 
beams and ceil ing panels during the day. An absorption chiller will 
be used as a back-up cooling system, in the event of insufficient 
capacity in the primary system. During the night-time, it is 
proposed that heat accumulated in the building fabric be removed 
by 'night purging'. This technique uses the diurnal temperature 
difference of the outside ambient air to flush unwanted heat stored 
in the building 's thermal mass during the day with cooler night-time 
air. This purging will be achieved by natural ventilation assisted 
by wind-driven extractor turbines. Since some components of the 
cooling system are unconventional, a more detailed description of 
these is presented below. 

.......... • 


1---t--t--low .enerQY
equlpmeJ'\ t 

significant energy 
savings by use of 
low en<lrgy equip­
ment and lighting 

Figure 2: Schematic overview of cooling system operation in CH 2 building 

COOLING SYSTEM COMPONENTS 

Phase change material 
A critical component of CH2's cooling system is the PCM. The 
function of the PCM is to store 'coolth ' transferred from the 
exit water of the shower-cooling tower combination at night. In 
the storage process, it is intended that the PCM will be cooled 
sufficiently to change phase and solidify from its previous liquid 
state. During the daytime, a closed loop will circulate water through 
the PCM to the chilled beams and ceiling panels, thus providing 
cooling to occupants. Throughout the day, the PCM will release its 
'coolth ' through this process and be returned to a liquid state by the 
evening, so that the process may be repeated the following night. 

The use of PCMs in buildings is not new. Solar researchers have 
investigated their potential as an alternative to the traditional , 
but more bulky, thermal storage media i.e. water and rock (e.g. 
Morrison and Abdul-Khalik, 1978). A number of buildings have 
been built using PCMs and Duffie and Beckman (1991) describe 
some of the results of these installations. In recent times , phase 
change research has focussed on the impregnation of building 
materials themselves to overcome the problem of the large 
areas required if the PCM is to be melted by direct solar radiation 

(Khudhair and Farid, 2004). In general, PCMs have been used to 
store excess heat and thus experience in the way proposed for the 
CH2 building is limited. Zalba et al. (2004) evaluated an air-based 
PCM cooling system designed for a residential building. The 
PCM used had a phase change temperature interval of 20-24°C. 
Although their simulations and experiments indicated the feasibility 
of using PCMs for cooling, the difference in operating temperature, 
heat transfer medium and application limits the relevance of this 
research to the CH 2 application. 

The PCM for the CH 2 building is currently being developed by the 
supplier (Environmental Process Systems Ltd, UK) and will be a 
low (15°C) melting point material. The PCM is reportedly a mixture 
of non-toxic salts and organic compounds (AEC, 2003c). The CH2 

system has been designed to supply a daily cooling load of 4539 
kWh , i.e. 25% greater than the estimated cooling load. The PCM 
will have a latent heat value of approximately 210 MJ m·3 and 
therefore at least 78 m3 of PCM encapsulated in the (proposed) 
0.1 m diameter polypropylene tubes will be required. The life 
expectancy and chemical stability of PCMs are the critical issues, 
which determine their viability. The PCM to be used is a new 
material under development and therefore no long-term operating 
experience is available. 

34 The Australian Journal of Construction Economics and Building [VoI5, No 21 



Chilled ceilings and beams 
Chilled ceiling panels, fixed to the curved ceiling in the offices, 
have been sized to cater for the internal cooling 102ds generated 
by occupants, lighting and equipment. The chilled panels cover 
35% of the curved ceiling. Chilled beams are to be located in front 
of the windows around the perimeter of each office zone. Their 
function is to cater for the loads generated by direct solar gain and 
heat conducted through the windows. The radiant temperature of 
the panels is designed to be 18°C, achieved by pumping water 
at 16°C through the panels. The shower/cooling tower-PCM 
combination will produce this chilled water. The internal cooling 
loads in the central office zone are estimated to be 35.5 Wm'2 
for 95% of the time. The air temperature design criteria for this 
zone is 21-25°C, but since the panels will provide radiant cooling, 
the objective of the system is to achieve a maximum resultant 
temperature of 23°C. 

In the UK, chilled ceiling panels are generally believed to be 
capable of dealing with cooling loads of 40-50 Wm'2. When 
cooling loads exceed these levels, perimeter chilled beams are 
recommended and then capable of handling loads up to 80 Wm-2 
(DlE and MGW, 2001). Chilled ceilings and beams are used 
in combination with displacement ventilation in 60-80% of UK 
applications (DlE and MGW, 2001). The effectiveness of this 
cooling strategy on occupant comfort has been demonstrated at 
the UK's Building Research Establishment (BRE) by Alamdari et 
al. (1998). These authors introduced air at 19°C into a test cell 
at the rate of 3.5 air changes per hour (ACH'1 ) or 2.6 I S'1 m,2 at 
ground level. The air temperature and airflow rate were determined 
by thermal comfort rather than air quality requirements. Some 
downward convection was determined, but upward convection was 
dominant in the vicinity of the occupants. A 90% or better occupant 
satisfaction was predicted . 

Similar positive results in terms of occupant comfort were obtained 
in other experiments conducted in the UK using a 16.2 m2and 2.8 
m high test room (Hodder et aI. , 1998). In this case, the supply 
air mass flow rate was set at 3 ACH,1 and its temperature was 
set at 19°C, as in the BRE experiments. The air supply rate in 
the CH2building is to be 1.5 I S'1 m,2 or 1.9 ACH,1 , assuming a 
2.9 metre average ceiling height, and the supply air temperature 
is to be 20°C. Based on the UK experiences, the chilled ceiling­
displacement ventilation combination may not be able to meet 
comfort requirements because the displacement airflow rate is 
lower and supply temperature is higher. 

Shower towers 
A novel feature of the cooling system is the five shower towers. 
These are lightweight fabric tubes, 1.4 metres in diameter and 
8 m in height, fixed to the outside facade of the south side of 
the building . In theory, when fine droplets of water are sprayed 
vertically down the towers, the momentum of the falling water 
entraps a certain volume of air, which establishes a flow of air 
down the towers. Any evaporation of the droplets cools the air, 
water and internal surfaces of the towers. It is intended that during 
the daytime the cooled and humidified air will be directed into 
the ground level retail spaces. At night-time, any cooled water 
collected at the base of the shower towers will be directed to the 
cooling towers. 

Givoni (1994) claims to have developed the shower tower to cool 
outdoor rest areas for the '92 EXPO in Seville, Spain. A search of 
the literature, however, indicates that the concepts employed in the 
shower towers are not new. Bahadori (1985) provides an analysis 
of Baud-Geers, which are the traditional wind towers used in Iran. 
The wind towers rely on the use of baffles to force wind down the 

tower, and while not part of the design for the CH2shower towers, 
the performance of these systems is of interest. The traditional 
Baud-Geer had a number of disadvantages and Bahadori (1985) 
lists these and analyses a system modified to overcome these 
drawbacks. One of the modifications is the provision of a wetted 
surface to evaporatively cool the induced air. The author provides 
charts estimating the dry bulb temperature of the air leaving the 
evaporative cooling column for given inlet conditions (ambient dry 
bulb, relative humidity and wind velocity) for various tower heights. 
Figure 5 of Bahadori (1985) shows that for a wind velocity of 5 
ms-1and ambient conditions not dissimilar to a summer day in 
Melbourne (25°C and 33% RH) , the dry bulb temperature leaving 
the evaporative cooling column is approximately 16°C for a 10 m 
high tower. The condition of the air at 35°C for a 9 m high tower is 
likely to be 90% RH and approximately 20°C. 

Pearlmutter et al. (1996) provide a theoretical analysis and 
experimental experience with a direct evaporative cool tower 
(DECT) used to cool a 500 m2glazed courtyard located in the 
middle of a multi-use complex in Israel. Following some prototype 
testing, the authors found the cooling potential for a natural draft 
system was low and hence they chose a mechanically drafted 
system. The effective height of the tower was 10 m and had a 
diameter of 3.75 m. The fan-forced air flow induced in the tower 
was 20,000-25,000 m3 h'1 i.e. had a velocity of 0.5-0.63 m S'1. It 
was found that the maximum cooling power of the system was just 
over 100 kW. Water consumption was 1-2 m3 d-1. The ability to 
cool the water as well as the air depends on a number of factors. 
The diameter of the drops sprayed into the tower and the length 
of time they spend in the tower are two key parameters. No final 
water temperatures were reported but the authors noted "the 
excess water collected in the pool beneath the tower is cooled 
considerably, and if more efficiently utilized could potentially 
increase the system's effectiveness" (Pearl mutter et aI. , 1996). 

In Austral ia, shower towers have been installed at the 1500 m2 
Interactive learning Centre at Charles Sturt University on its 
Dubbo Campus in NSW (CADDET, 2002). located in the central 
space of the building, the four 8.8 m high towers use two water 
spray systems. large droplets are sprayed into the tower at the top 
and smaller water particles are then misted into the air just prior to 
its entry into the occupied space. Some measurements taken at 
the building suggest the system is performing poorly (Yeo, 2004). 
Flow into the building at the time of the measurements was only 
8% of the design flow, resulting in much reduced cooling capacity. 
This occurred on calm days. On windy days, airflow direction in the 
towers was upward i.e. reversed and consequently provided no 
cooling at all. 

To date all installations and analysis of shower towers has been 
performed for climates with high dry bulb temperatures and low 
relative humidities. In the three summer months (December, 
January and February) in Melbourne, the average dry and wet 
bulb temperatures during office hours (8am to 6pm) is 21.9°C 
and 15.9°C respectively (Roy and Miller, 1981). The exit air 
temperatures and airflow rate from an 8 m shower tower with a 
water flow rate of 15 I min,1 can be predicted using the expression 
developed by Givoni (1994). For the above dry and wet bulb 
temperatures, an exit air temperature of 16.5°C is predicted, which 
will be adequate to cool the retail space on the ground level, as 
proposed. The predicted airflow rate would provide approximately 
4 ACH,1 for the retail spaces. During the night, the function of the 
shower towers is to precool the water entering the cooling towers. 
A 0.5-1 .0oC reduction in temperature is anticipated. As mentioned, 
no data could be located to substantiate this expectation, but 
according to Pearlmutter et al. (1996) considerable cooling occurs 
and so this estimation appears to be reasonable. 

The Australian Journal of Construction E(onomics and Building [VoIS, No 2] I 35 



Cooling towers 
There will be two Baltimore Air Coil RCT series counter-flow 
cooling towers installed at the CH2 building . Their main purpose 
is to reduce the temperature of water at night to the level where 
freezing of the PCM occurs. In the three summer months 
(December, January and February) in Melbourne, the average dry 
and wet bulb temperatures during non-office hours (7pm to 7am) 
is 17.90C and 14.50C respectively (Roy and Miller, 1981). The 
manufacturer has claimed that an exit water temperature of two 
degrees above the ambient wet bulb temperature can be expected. 
To freeze the PCM a temperature of below 15°C is required 
and therefore it appears the cooling towers will not achieve this 
temperature, even if the water has been pre-cooled by the shower 
towers. This conclusion agrees with the consultant's analysis, 
which found that the cooling towers could only be used for nine 
days over the three main summer months to freeze the PCM (AEC , 
2003c). The absorption chiller will therefore be the main source of 
cooling during the summer months. The cooling load in the three 
summer months is estimated to represent approximately 36% of 
the total annual cool ing load of the building (AEC, 2003c). 

Night purging 
Night ventilative cooling or night purging has the potential to 
reduce cooling loads where there is sufficient diurnal difference in 
ambient air temperatures. Outside air is drawn into the building at 
night and heat is transferred to the moving air as it passes through 
the building. The effectiveness of night purging is a function of the 
airflow rate, surface area and thermal effusivity, the final factor 
being the root of the product of the conductivity, density and 
specific heat of the building material (van der Maas and Roulet, 
1991). In the CH2 building , the movement of air is to be induced 
by natural means and assisted by wind-driven extraction vanes or 
turbines. When the outside air temperature is below the concrete 
ceiling temperature, windows on the north and south facades will 
be opened automatically to allow outside air to be drawn in . The 
thermal mass of the exposed concrete ceilings will absorb some 
of the daytime heat gains and the cooler outside air will remove 
some of this heat at night as it moves through the building . Design 
calculations indicate that the use of night purging can reduce the 
daily cooling load requirement of the CH 2 building by approximately 
14% In summer (AEC, 2003a). 

Blondeau et al. (1997) conducted a series of experiments in a 
three-storey office building in France to investigate the impact 
of nocturnal cooling on energy consumption and its effect on 
occupant comfort. In their building, outside air was induced by 
mechanical, rather than natural, ventilation. Purging began at 9 
pm and continued until 8 am. The required airflow rate was the 
equivalent of 8 ACH·1, which agreed with the finding of Agas et 
al. (1991). As in the CH2 building , the windows were kept closed 
and shutters restricted thermal gains during the daytime. Internal 
temperatures could be reduced to within 2-4°C of the minimum 
ambient temperature and the temperature of the air in purged 
rooms was 1.5-2.00C lower than the reference room. These results 
were obtained for an average outdoor temperature range of 
8.4°C, which Blondeau et al. (1997) believed was unfavourable2. 

When translated into cooling energy needs, savings of 25% were 
predicted for a set point temperature of 24°C. 

Similarly high air exchange rates were used by Birtles et al. (1996). 
In a simulation study, rates of 5-15 ACH·1 were used. It was found 
that the higher the air exchange rates the lower resulting internal 
temperature. Increasing from 5 to 15 ACH·1 reduced the internal 

temperature by 1.50C during the daytime. At the lowest ACH·1, the 
internal temperature was at least 2.00C lower than the 'no purge' 
case. Purging temperature was set at 16°C. The effect of thermal 
mass on peak temperatures was also investigated. High mass 
interiors reduced peak daytime temperatures by 1.5-2.00C. 

Ventilation by natural means (i .e. the stack effect) can be achieved 
but obviously without the reliability of a fan-forced system. Van 
der Maas and Roulet (1991) carried out an experimental study of 
natural ventilation study on a three storey building and developed a 
simple algorithm to predict exit air velocities knowing the inside­
outside air temperature difference, the inlet-outlet opening area 
ratio and the height between inlet and outlet. Application of this 
algorithm, however, may be inappropriate in this case because 
of the indirect air path in the CH 2 building. Van der Maas and 
Roulet's model did predict that heat removed from a building could 
be maximized by increasing the surface area and the thermal 
effusivity of the exposed materials. 

In the case of the CH 2 building, the area of the ceiling has been 
increased by approximately 10% by adopting an undulating profile. 
Surprisingly, however, the consultants found little difference in 
cooling loads when external walls of concrete, aerated concrete 
and plasterboard were compared (AEC, 2003a). The thermal 
effusivity of concrete is approximately 1864 J m·2 K1 S·05, which 
is over five times higher than plasterboard. Their finding appears 
to contradict the research relevant to night purging. The fresh air 
entering a typical perimeter zone was calculated to be 4.2 kg S·1 
(on average) or 12600 m3 h·1(AEC, 2003a), which is the equivalent 
to approximately 4.1 ACH ·1 . This level of ventilation is lower than 
the overseas researchers cited believe is appropriate for effective 
night purging . 

COMFORT AND PRODUCTIVITY 

While avoiding uncomfortable internal environmental conditions 
would appear to be commonsense and may produce a happier 
workforce, the gains made from making marginal changes in those 
conditions are much less certain . The weak link between thermal 
comfort and productivity is acknowledged by the designers of the 
CH2 building (AEC, 2003d). In assessing the potential productivity 
gains resulting from CH2's indoor environment, only the research 
conducted in offices has been used in this study. Similarly, only 
aspects of the indoor environment related to this study (i.e. 
temperature, humidity and air movement) are considered. 

In a discussion following a series of papers investigating the 
impact of the building environment on indoor productivity (Lorsch 
and Abdou , 1994), the first author stated that "there is no direct 
link between worker satisfaction and productivity, nor is discomfort 
(emphasis added) always linked to nonproductivity." The authors 
also state that "although there is a preponderance of opinion that 
improving the work environment leads to productivity, quantitative 
proof of this statement is sparse and controversial. " A sample of 
the research literature confirms this view. 

Fisk and Rosenfeld (1997) review the literature "on the linkage 
between thermal environment (primarily air temperature) and 
selected indices of work performance." These authors state that 
although there is substantial evidence of an association between 
work performance and air temperature, ... ... not all studies 
found such associations" and not all studies showed a positive 
association between comfort and productivity. For example, 

2 In Melbourne, it is 7.50C, based on the long term average temperatures at 5arn and 3pm in the three summer months (December, January and February). 

36 The Australian Journal of Construction Economics and Building [VoIS, No 2J 



one study cited found that 18-49% more typewriting work was 
performed at 20DC compared to 24DC. Other studies of mental work 
performance (but not necessarily in offices) showed that reading 
speed , memory and learning performance also might improve 
at temperatures outside of the traditional comfort range. Slight 
thermal discomfort appeared to increase arousal , according to Fisk 
and Rosenfeld (1997). 

A study of call centre workers, however, showed that a reduction 
in workers' talk time, i.e. an increase in their productivity could be 
achieved by increasing the airflow rate from 5 to 10 I S ·1 p.1 at an air 
temperature of 24.5DC. This result indicates that the adverse effect 
of a higher air temperature on their activity could be ameliorated by 
increasing air movement (Tham, 2004). Other studies (e.g. Fang et 
aI. , 2004) of office workers, while "confirming the observed impact 
of temperature and humidity on perceived air quality .. ... . " found 
that "performance of office work was not significantly affected by 
indoor air temperature and humidity". 

Leaman and Bordass (1999), using occupant surveys from 11 UK 
buildings over a 15-year period, arranged possible factors affecting 
productivity into four clusters. Only the first of these clusters 
i.e. 'personal control' includes factors relevant to this study. 
Perceptions of personal control were measured by the average 
of five variables, namely heating , cooling, lighting, ventilation 
and noise. Of these, noise was most strongly associated with 
productivity, which perhaps confirms the decision to keep the 
windows of the CH2 building closed during the day. Leaman and 
Bordass (1999) state that in "study after study, people say that 
the lack of environmental control is their single most important 
concern, followed by lack of control over noise." In the CH2 

building, occupants have only control over the air movement 
through the displacement air inlet vents , so by this measure it may 
be concluded that they will not perceive significant productivity 
benefits from the heating and cooling systems. 

CONCLUSIONS 

The heating and cooling system for the CH2 building will use some 
novel technologies and concepts such as shower towers, PCM and 
natural night purging. However, these innovations are supported 
by more conventional technologies such as an absorption chiller, 
evaporative cooling towers and waste heat recovery. Properly 
engineered, these latter systems should ensure that thermally 
comfortable environmental conditions are achieved in the CH2 

building. 

A review of the technologies proposed to provide cooling against 
previous experience indicates that the displacement ventilation 
airflow rate is low compared to overseas experience, although the 
cooling loads predicted are in the same range. While evaluation of 
the shower towers using empirical formulae indicates that useful 
temperatures and airflow rates may be obtained, Australian and 
overseas experience indicates that reliance on natural air flow is 
inadequate. The shower-cooling tower combination cannot be used 
to produce useful temperatures in summer and the absorption 
chiller must be used. Although design calculations indicate that 
approximately 64% of the cooling load occurs in the non-summer 
months, the wisdom of incorporating cooling technologies that 
cannot be used during the main period of continuous and peak 
cooling demands and that are unproven is questionable. Natural 
ventilation for night purging , while effective in favourable ambient 
conditions, does not achieve the air exchange rates found 
necessary in overseas studies. 

Because the indoor conditions chosen for CH2 are within the 
accepted range of comfort zones for a climate controlled building, 

productivity is unlikely to be increased by the air temperature and 
humidity. The small level of control offered by the vents in the 
displacement ventilation system does not constitute significant 
control over individual environments, which has been cited 
as the single biggest concern of workers. Finally, it should be 
remembered that in terms of office worker productivity, ... "HVAC 
and IAQ are rated well below such items as privacy, interpersonal 
communications and relationships, office arrangement and 
managerial attention" (Lorsch and Abdou , 1994). 

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38 The Australian Journal of Construction Economics and Building [Vol 5, No 2] 



CITY OF MELBOURNE RESPONSE 

In their research paper into CH2's heating and cooling systems, 
Aye and Fuller raise a host of interesting questions about the 
success of green technologies worldwide and how they might 
operate in CH2. 

Some of these points have been and continue to be critical 
issues for the CH2 team. Other pOints have been superseded 
by design changes made since Aye and Fuller completed their 
research in early 2005. Several more points relate to examples 
in other buildings that at first blush appear to be relevant to CH2 

but on closer examination are like comparing apples with pears 
- interesting but ultimately not the same thing at all. 

For instance, Aye and Fuller compare CH2 's shower towers with 
traditional Baud-Geer wind towers in Iran and a shower tower 
system at Charles Sturt University in Dubbo, Australia. Neither of 
these systems can be compared directly to CH2• For instance, the 
Baud-Geer relies on wind as well as a wetted surface. However, 
the CH2 towers, based on the passive downdraught evaporative 
cooling concept, rely on momentum from water droplets, not mist, 
falling under gravity. 

Conversely, the authors discount comparisons with other phase 
change material (PCM) systems when a connection clearly can be 
made. They argue PCM materials traditionally are used to store 
excess heat, not "coolth", and thus the CH2 system is "untried" 
and cannot be seen to have been successful elsewhere. On the 
contrary, CH2 's PCM system most certainly does store excess 
heat. The issue here is merely a naming issue: "cooling material" 
or "heat-absorbing material" - call it "half a dozen" or "six", the 
process is identical. It is on these mistaken assumptions the 
authors have based their comments questioning the choice to use 
these environmental technologies in the building. 

Elsewhere, Aye and Fuller appear to criticize CH2 's cooling towers 
for being useful only on nine days during the three summer 
months. Rather than being a failing, this is a reality that is clearly 
understood by the CH2 team, which measures the towers ' worth 
by their effectiveness during the other nine months of the year 
and has built in additional green measures to help during summer. 
For instance, for maximum financial and environmental efficiency 
the electric chiller will be used only at night when it will have most 
effect. During the day the recovered-heat absorption chiller will be 
used. 

The authors make repeated comments about the "sparse and 
controversial" link between thermal comfort and productivity and 
make a point of mentioning the CH2 team acknowledges this. They 
highlight a 1994 study that found no direct link between worker 
satisfaction and productivity. However, what is not pointed out is 
the broad range of CH2 features that - read collectively rather than 
individually - may well make profound changes in the ability of 
staff to be healthy, effective and productive at work. 

Agreed, being able to adjust an air vent under the floor will not 
alone make healthy and satisfied workers. However, the thermal 
comfort provided by cool surfaces rather than refrigerated 
recycled air, a personal supply of air that has minimal mixing with 
colleagues' air, the use of materials with low emissions, adjustable 
lighting, access to outdoor areas, plentiful emission-absorbing 
plants and a host of other features must, in concert, make 
significant and substantial inroads into this area, which has the 
potential for such lucrative gains. 

Perhaps the most important point to be learned from this paper 
by Aye and Fuller is that the ongoing discussion about the use of 
green technologies will continue to be spirited for a great deal more 
time. Scepticism will remain until there are plentiful case studies, a 
cornucopia of academic papers and a great many CH2s. 

The Australian Journal of Construction Economics and Building [Vol S, No 21 I 39