Tom Beckerling Natural Ventilation

8/11/2019 Tom Beckerling Natural Ventilation

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Faculty of Engineering, Computing and Mathematics

Feasibility of Natural Ventilation

in the Mechanical Engineering

Building

1


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Project Summary

In pursuit of UWA sustainable development goals, this study investigates the possibility of using

natural ventilation in the Mechanical Engineering building at the university's Craley campus! "he

building currently uses a number of mechanical heating, ventilation and cooling #$%AC& systems

hich offer some opportunities for improved energy efficiency! "o study the eisting building and

services, a model of the building has been created using state of the art thermal simulation and

analysis softare! A selection of natural ventilation schemes have been modelled in order to study

the feasibility of replacing, or reducing the energy consumption of, the mechanical ventilation

currently used! "his report describes the modelling pro(ect and discusses the results of the

feasibility study conducted!"he scope of or) for this pro(ect, as stated at the outset, has proved to be somehat over

ambitious! "he compleity of the softare chosen for the tas) has sloed don the pace of the

modelling tas)! While *+ +esign tudio is an ecellent pac)age and it leverages the poer of the

Energy-lus to ensure high .uality hole building simulation, it is at an early stage of development!

$ence it is poorly documented and suited more to eperienced professionals! "his has sloed the

progress on the basic models hich must be made before .uality investigations of possible

alterations to the building can be made! "o deal ith this reality, it has been proposed to reduce the

scope of the pro(ect and focus on investigating the feasibility of natural ventilation for the

mechanical engineering building as constrained by the local climate and the building!

Acknowledgements"han)s to /eraldine "an, "ony $umphries, Angus "avner, Mar) -itman, $elen Whitbread, Alistair

0obertson!

School / Section name

The University of estern !ustralia

M""", #$ %tirling &igh'ay, Cra'ley ! ("")

Tel *(+ (- """"

Fa. *(+ (- """"

Email email/u'a0edu0au

Web www.xxx.uwa.edu.au

C12C3% 4rovider Code5 ""+6(7


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Table of Contents

-ro(ect ummary!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ac)noledgements!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!2

-lanned -ro(ect cope !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 3

0evised -ro(ect cope!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 3

4iterature 0evie5Case tudies!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 6

Case tudies!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!6

City of Melbourne's Council $ouse !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!6

/rove $ouse at "hames %alley University!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!7

8ion 9ational -ar) %isitor Centre Utah!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:

;uilding +escription !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Modelling oftare!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 12

*+ tudio!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!12

*pen?*AM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 12

Energy-lus!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!12

Model Inputs!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!12;uilding /eometry!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 13

Construction and Materials!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!13

Windos and hading !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 13

;uilding Use and *ccupancy!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 16

chedules!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 16

*ccupancy!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!16

4ighting!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 17

Electric E.uipment!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!17

Windo %ent chedule!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 17

"hermal Comfort chedules !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1:

Activity !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1:Clothing !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1:

Air velocity !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1:

Wor) Efficiency !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1:

Ideal 4oads $%AC !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1:

Airflo 9etor) !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1:

Infiltration !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1


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0esults!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1

Input %erification!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 1

Cooltoer!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

hading!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Comparative tudies!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!>

ummary +iscussion!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! >

Conclusions!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! >

0eferences!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! >>

2


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Planned Project Scope1! Complete audit of eisting mechanical services in building including Chilled ater loops,

additional heat5cool services, ducting, fans, diffusers etc!

! Identification of possible natural ventilation schemes in building #consult ith ?acilities

Management 5 $%AC engineer&

>! Create a computer model of the Mechanical Engineering building and its mechanical service

2!%alidate the model ith actual data #energy consumption etc&

3! Model various natural ventilation schemes6! Investigate additional energy efficiency measures #e!g indo insulation films& to supplement

natural ventilation proposal

7! Analy@e the model and select the most favorable alternatives

:! *utline costs of proposed scheme and compare to energy savings estimated

Mechanical Engineering building

Revised Project Scope0eferring to the planned pro(ect scope above, the planned revision of the scope ill be

1! Unchanged

! Unchanged

>! Unchanged

2! After discussions ith ?M, it as decided not to proceed ith this!

3! ?eer of the proposed options ill be investigated, rather than fully implemented models for

each of the options, the modelling ill focus on the feasibility of an ideal natural ventilation

scheme !

6! Modelling reduced solar gain is still planned!

7! 0eplace this element ith a discussion of ho to implement the modelled scheme in the eisting

building!

:! Cost of the imageI9B film can be found


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Grove House at Thames Valley University/rove $ouse at "hames %alley University in the UB underent a substantial renovation to

implement a natural ventilation scheme! "he main features of the scheme being a passive stac) and

facade ventilation system, the use of nightcooling and solar panels for electricity generation!

Windos ere replaced to include air inlet grilles to ventilate a plenum space ad(acent to the

internal floors! Air flos along the

thermal mass of the concrete slabs

and is dran into stairells hich

serve as passive stac) devices here

air is dran out at the rooftop! "he

scheme is fundamentally similar to

the one implemented in the

Melbourne Council building,

hoever, the facade deals ith the

security issue of openable indos!

"he system re.uires airspace ad(acent

to the internal floors continuous to the

stairells! "o apply this scheme to the

UWA Mechanical Engineering

building, etensive or) ould be re.uired to provide such a continuous space for airflo! In the

buildings core, there are three stairells hich could provide the necessary vertical spaces! A lac)

of ceiling space in the building is the other main hindrance to applying such a scheme!

7

Figure 1: Night cooling at Melbourne's City Council Building

Figure 2: Facade Ventilation devices


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Zion National Park Visitor Centre Utah

"he final case study eamined is the 8ion 9ational -ar) %isitor Centre in Utah! "he local climate

dry and mild, ith arm summers, similar to -erth's! "he %isitor Centre is a landmar) pro(ect for

passive design! "he )ey features of the building are its open plan, ith high indos oriented to

catch the inter sun and eclude the summer sun, a cooling toer using ater evaporation to

provide a lo energy source of temperature and humidity control and trombe alls to provide

passive heating in inter!

"he %isitor Centre provides an eample of an ideal implementation of passive design and natural

ventilation! It highlights the potential of passive design features hen incorporated into the building

design from its inception! "he relevance of this case study to the Mechanical Engineering building

at UWA is the use of cooling toers combined ith lo openings for inta)e air and high openings

for ehaust air! "he climate in -erth dictates that some source of cooling ill #most li)ely& be

needed to maintain comfortable conditions! Cooling toers may be able to provide this cooling at a

lo energy cost!

:

Figure 3:Photo of the Visitor Centre shoingcooling toer and high indos for e!haust air

Figure ": #he $assive design features of the Visitor Centre


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Building Description"he mechanical engineering building at the University of Western Australia's Craley campus is a

large spraling building! It consists of nine main bloc)s and to lecture theatres! "he core of the

building consists of the A,; and C bloc)s! -eripheral to this core, there are several large or)shop

and laboratory area, hich are generally large spaces ith high ceilings! Each building is divided on

its east est aes by a central corridor! ;oth the south and north facades are gla@ed, ith the

northern facades generally having more internal blinds shading the rooms on that side! "he building

as constructed in the 1


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Eisting !eating" ventilation and cooling system"he core of the Mechanical Engineering building is serviced by a variable air volume #%A%& $%AC

system that as retrofitted to the building in 1


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Local climate"he etent to hich natural ventilation can provide a comfortable internal environment is dictated

largely by the local climate! "o achieve the necessary fresh air ventilation rates Fneed to set up A

fresh air re.uirementsG and maintain cool indoor air temperatures during long hot summer periods

are often conflicting re.uirements! "he etent of this conflict varies ith the seasons and ith

climate! In temperate climates, the outdoor conditions ill coincide ith satisfactory thermal

comfort for a considerable proportion of the year! In hot humid climates there is a small proportion

of the year hen outdoor air can be used to ventilate an indoor space ithout raising the

temperature to an uncomfortable level!

"hus an assessment of the local climate is a necessary starting point for a discussion of the

feasibility of any natural ventilation scheme!

"he climate in -erth, WA is classified as dry ummer sub tropical under the Boppen classification

and is characterised by dry and hot summers and mild inters! +uring the armer months, the local

eather is dominated by high pressure systems bringing dry easterly inds! "his summer pattern is

accompanied by a seabree@e! Which, hen it occurs, brings a cool change in the afternoons! As

initial modelling and advice from ?M sho that the Mechanical ;uilding does not often re.uire

heating, the focus throughout this study is on the ummer conditions and the availability of cooling

measures!

"he annual trend of minimum and maimum temperatures is shon in figure ?I/U0E! ummer

maimums in the high >='s are typical, ith cool evenings being the norm! Winter maimums in the

high teens, and minimums above free@ing are typical! What is also apparent in the figure belo is

that the diurnal variation through the year is relatively constant! +uring the milder seasons, this

translate into a reasonable level of night cooling potential!

11

Figure *( Monthly &ini&u& and &a!i&u& te&$eratures

8anuary February March !pr il May 8une 8uly !ugust %eptember 3ctober November 9ecember !nnual

"

$

+"

+$

6"

6$

#"

#$

Temperatu

re:C;


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"he prevailing ind is detailed in figure ?I/U0E belo! "he figure shos the prevalence of the

southesterly ind in the afternoon, providing a reliable coolchange to most hot days!

"he sea bree@e is a southesterly ind hich generally pic)s up by mid afternoon and can travel

inland further than the metro area! "o .uantify the possible cooling effect available from the sea

bree@e, eather data for the past < years from the -erth Airport as analysed! ;ased on a rough, but

reasonable definition hich states that a sea bree@e occurs if

the ind direction is beteen 1:= 7=

the ind strength is 3 )nots or greater #!3m5s&

the daily maimum as above 3C

With a total of 362 days of ind and temperature data for the past < years there ere 77 days

ith a sea bree@e beteen 1pm and 1am, a mean value of about :, or 1 day in three! "here

ere >>6 out of 362 days here the ma as above 3 and there as no sea bree@e!

"he climatic cooling potential, epressed in degreehours as calculated for a building temperature

of >C and the average C-- value for each month of the year is shon in figure ?I/U0E belo!

1

Figure +: ,ind -oses for Perth's seasons. (thin)bric)(co&(au


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"he lo C-- values for the hot months of +ecember, January, ?ebruary and March, #less than

2=Bh& mean that there is limited potential for nightcooling in these months!

#ptions and #pportunities

/uided by this evaluation of the local climate and by the case studies discussed, a number of naturalventilation and passive design features ere investigatedK

1! 9ightcooling through openable indos

! Windo films applied to eisting indos

>! *perable shading devices

2! +aytime cooling ith Cooltoers

"hese options provide an opportunity to reduce the energy consumed in cooling the Mechanical

Engineering building! "he building and the climate provide some constraints on the degree and

nature of these opportunities! Using the thermal simulation and analysis methods that are consistent

ith the process of environmentally sustainable design, the feasibility of these options ere

investigated!

1>

Figure /( Cli&atic Cooling Potential

8anuaryFebruary

March!pril

May8une

8uly!ugust

%eptember3ctober

November9ecember

"

6"

-"

("

"

+""

+6"

+-"

Climatic Cooling 4otential

9egree


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$odelling So%tware

ODS Studio

"he modelling and analysis softare used for this pro(ect

as *+ tudio! *+ +esign tudio brings together several

opensource pac)ages including ;lender a >+ design tool,

Energy-lus the building simulation and analysis tool

developed by the U! +epartment of Energy and 9ational

0eneable Energy 4aboratory, *pen?*AM a

computational fluid dynamics pac)age and other pac)ages

not used here #-itman, =1&

"he building geometry is modelled in ;lender! $ere the

building's physical properties, its floorplan, construction

materials etc are represented! *+ tudio translates these

properties into the form re.uired for Energy-lus! "his is encapsulated in the I+?, hich is a tet file

containing a description of the buildings surfaces, construction materials, shading, $%AC system,

internal loads #people, lights, electricity&, the schedules on hich the building operates #e!g times

hen it is occupied, times hen the $%AC is on and off& and other re.uired details! Energy-lus

ill simulate this building over a given period and sub(ect to an eternal environment described in a

eather file!

OpenFOAM

?urther modelling inputs are available by passing the building geometry to *pen?*AM and

running C?+ simulations, for eample to eamine the pressure distribution on the building facade

under the action of ind! +ue to time constraints, etracting the pressure distribution data from

*pen?*AM as not achieved!

EnergyPlus

Energy-lus is one of the most highly validated thermal modelling tools available! It is also

opensource hich means no licensing fees are necessary to use it! ?urther, it is very elldocumented and supported!

$odel &nputsIn order to construct a useful thermal model of the building, a considerable amount of input data

as re.uired! "his data consists of information hich can be broadly categorised intoK

1! ;uilding geometry

! Construction and materials

>! Windos and shading devices

2! ;uilding use and occupancyK patterns of building occupancy and use!

12

Figure 0: n i&age of the &odel. dran in Blender


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3! $eating, ventilation and cooling system #$%AC&

3! 4ocal eather conditions!

Building Geometry

"he geometric and $%AC information as gathered from architectural and mechanical plans!

+iscussions ith "ony $umphries from ?acilities Management ere also a very useful source of

information on the building and $%AC operation! "he architectural draings provided the starting

point for the model of the building! Well over >== draings ere provided by ?M! "hese draings

include original plans from created by the +epartment of -ublic Wor)s in the 1


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Building se and Occupancy

With the eclusion of the building shell, the building use and occupancy is probably the most

important aspect of the energy model! "he thermal load hich a $%AC system must meet comes

from to categories, eternal and internal gains! "he main eternal source of heat is solar gain!

"here are four main internal gains consideredK people, lights, electric e.uipment and infiltration!

Each of these internal gains has an associated schedule according to hich the thermal load varies!

"hese schedules and their pea) values are described belo!

Schedules

Occupancy

"he occupancy levels have been set by

specifying area per person! Consistent ith

typical office space densities, this is set at 1

person per 1= s.uare metres! Energy -lus

calculates internally the number of people in a@one from the floor area! "he pea) occupancy

level then varies according to the schedule in

figure ?I/U0E to the left! "his schedule is

typical of an office space, here levels fluctuate

through the or)ing day, ith a lull around

lunchtime!

16

Figure 1: so&etric vie shoing eastern facade ith shading in yelloFigure 11: so&etric vie shoing eastern facade ithout shading

Figure 11

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Lig!ting

"he lighting levels are set at a level consistent

ith a typical office space, of 1=W5m!

Energy-lus calculate internally the total

lighting poer in a @one from the @one floor

area! "he lighting levels fluctuate through the

or)ing day according to the schedule shon

in figure ?I/U0E to the left! 4ighting levels

are set at @ero over ee)ends and holidays!

Electric Equipment

E.uipment levels, accounting for the heat

generated by e.uipment such as computers,

des)top lamps, photocopiers etc, is accountedfor by specifying an e.uipment level of

approimately >===W per @one! "his level

fluctuates according to the schedule shon in

figure ?I/U0E!

Window Vent Schedule

"he openable indos operate on a schedule hich accounts for occupancy and temperature!

+uring occupied hours, the indos can be opened hen there is a temperature benefit to doing so!

"he indo vent schedule sets a limiting temperature of 1!1 degrees! When the temperature in a

@one is above this setpoint and the temperature indoors is higher than outdoors, the indos are

opened! "his corresponds to a common sense approach to indo venting! It allos for cooling

bree@es to ventilate interior spaces! When the outdoor temperature is belo this set point, hich

17

Figure 12

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forced ventilation! A simple Airflo 9etor) as implemented, to capture the effect of ventilation

through openable indos and crac)s in the eternal facades! In order to manage the compleity of

this simulation module, the settings ere ta)en from eample files detailing the ventilation of a lo

rise, rectangular building! "he Airflo 9etor) re.uires details on each surface of the building, in

order to calculate the effect that a ind, from any direction, ill have on the pressure distribution

over that surface! Initially, the scope of the pro(ect included modelling the building in *pen?*AM,

in order to etract the coefficient arrays necessary for the Airflo 9etor) settings! $oever, the

this step proved too complicated to solve in the available time! ?or an idea on the level of detail

re.uired, each eternal surface, of hich the model has about ==, needs an array of 1 values,

detailing the effect of a ind from an array of directions, >= degrees apart! In order to calculate

theses 1 values, the model must be placed in a simulated ind tunnel, the ind applied, and thepressure distribution calculated! "hen the pressure over the area that each eternal building surface

occupies mus be calculated and ;ernoullis e.uation solved to etract the ind pressure coefficient

value! "his ould mean that 1 C?+ simulations ould need to be run, ith each run needing over

== calculations! *bviously, this process ould need to be automated, yet doing so ould have

been very time consuming! "he alternative as to accept the approimation provided by assuming

the building as rectangular! "his ill result in some errors to the pressure distributions calculated

internally in Energy-lus! $oever, the air change rates inspected sho reasonable values and for

the level of accuracy in the model as a hole, the approimation as decided to be acceptable!

Infiltration

?or the passive model, the Airflo 9etor) is disabled! In order to achieve a comparable level of

night cooling, a design level of infiltration is set! "his level is set according to a schedule that

replicates the behaviour of the Airflo 9etor)! +uring the armer months, 9ovember to April,

infiltration levels of 1= AC$ occur overnight, dropping to 1 AC$ during the day! +uring the cooler

months, the infiltration level is a constant 1 AC$!

Assessment Criteria"o assess the effectiveness of the various natural ventilation and passive design features

investigated, some criteria must be chosen by hich to (udge them! "he criteria chosen are

discussed belo!

#ndoor !emperatures

"he most direct and simple criteria for (udging the effectiveness of the various options investigated,

is to compare the resulting air temperatures! As there are over = @ones in the building model, one

@one is chosen to conduct most of these comparisons!

#n"iltration and &entilation )ates

"he fresh air rates delivered by natural ventilation are set by Australian tandard A166:! ==!

"he re.uired fresh air rate set by "able 2! for lo activity levels is 345s per person! At a typical

office density of 1=mN per person, this e.uates to =!45s5mN or =!===mN>5s5mN of fresh air!

1


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"his level of fresh air inflo can be used as a rough guide as to the rate of inflo due to the

infiltration modelled ith the Airflo 9etor) through surface crac)s!

"he typical air change rate for an office or public buildings is =!> =!3 Air changes per hour, AC$!

Fref thisG! Air Changes per $our is the a flo rate measurement! It indicates the flo rate at hich a

room's volume of air is replaced in one hour! "his doesn't mean the air in the room is entirely

replaced by fresh air, hether this occurs depends on the effectiveness of the inflo and outflo of

air in the room! It simply indicates a rate of flo of outside air into a room si@ed volume of the

period of time of one hour!

"hese to rules of thumb are used to verify the rates of infiltration and ventilation in the models!

Cooling $oads

"he relative energy efficiency of the natural ventilation schemes investigated is found by comparing

the loads re.uired to maintain a heating set point of 1C and cooling set point of 2C! Using the

Ideal 4oads $%AC system available in Energy-lus, these loads are found for each of the models!

"he Ideal 4oads calculations in the Energy-lus simulation state this energy in Joules, hich is

converted to )Wh, for every hour of the year simulated!

!hermal Com"ort

"he community epectation of comfortable internal environments has arisen as a cultural

conse.uence of the prevalence of mechanical cooling of buildings! 0esearch into thermal comfort

conducted in the 1 Cold

! Clothing insulation Cool

>! Air temperature 1 lightly cool

2! 0adiant "emperature = 9eutral

3! Air speed 1 lightly arm

6! $umidity Warm

> $ot

"hese factors are the ob(ective variables hich allo a .uantification of the more sub(ective notion

=


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of 'hot' or 'cold' ! "o capture the more sub(ective measure of a person's sensation of that

environment, the A$0AE thermal comfort scale is used! "his provides a numerical scale to match

to the sensation of 'hot' and 'cold'! "he -redicted mean vote calculates the number hich := of a

typical group of people ould choose on this scale given the environmental variables at the time!

Comfort ranges can be selected, for eample, the A$0AE standard sets the -M% range to =!3 to

=!3! ee figure ?I/U0E, hich relates to := of occupants being comfortable!

"he ability of people to adapt to their local climate is an important consideration in thermal

comfort, hich is somehat overloo)ed by the ?anger predicted mean vote method! "he effect of

local climate is accounted for in the standard effective temperature#E"&, a measure of thermal

comfort detailed by @o)olay #@o)olay, 1


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of AC$! Eamining a typical @one for the average and maimum infiltration value verified an

average of =!>


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Comparative Studies"he second broad category of analyses underta)en ere comparative studies! "hese studies can

further be placed into one of three investigations

1! Closed versus *pen building

! 9arro versus Epanded thermal comfort criteria

>! %arious indo films

0 Closed versus #pen +uilding

In this first study, the baseline model, in hich the building has an Ideal 4oads $%AC netor) and

an Airflo 9etor) simulating openable indos #or an ideal cross ventilation scheme& iscompared to a model ith the same input ecept that the indos remain closed at all times! "hus,

comparisons are made beteen a building in hich all heating and cooling is done by a mechanical

system and a building ere the mechanical system is supplemented by night cooling and a indo

opening rule hich states, in basic terms, that the indos are opened hen there is a temperature

benefit from doing so!

"he goal of this study is to investigate hether openable indos can reduce the re.uired cooling

loads!

"he method used to determine an anser to this .uestion is to implement openable indos! "he

baseline model is varied by adding an Airflo 9etor) to allo for night cooling of the building!

"he results dran upon to anser this .uestion are the indoor air temperatures and the Ideal 4oads

Cooling energy re.uired to meet the cooling set point! ?igures belo sho the indoor temperature

in a typical @one during a ee) from each season of the year, corresponding plots of the re.uired

cooling loads and finally these to data sets in one plot! "his last plot helps to sho ho the night

cooling effect reduces the cooling load re.uired and also to sho that there are periods in the year

hen simply opening indos ill lead to comfortable interior conditions, bypassing the use of the

mechanical system entirely!

It is important to note that in these to models, the Ideal 4oads $%AC system does not have an

economy mode! "he economy mode ould reduce the energy used to cool the building, by

increasing the flo of outdoor air into the @one hen the outdoor air is belo the indoor air

temperature! An economy mode should be standard on any modern $%AC netor) that attempts toachieve reasonably efficient operation! While it decreases the cooling energy re.uired, it

nonetheless using the mechanical systems fans, ducting and associated electrical e.uipment! It

thus doesn't solve the common sense contradiction of using a mechanical system to ventilate a

building hen simply opening indos and alloing the bree@e to do free cooling!

>


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Figure 1%

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"6+) "+5""5"""6+) ")5""5""

"6+) +@5""5""

"0"$0"

+"0"+$0"6"0"6$0"#"0"#$0"

Temperature Comparison for Closed and 3penable indo's

%ummer

one Mean !ir Temperature, 3penable indo's one Mean !ir Temperature, Closed indo's

Temperature:C;

Figure 1*

"$"++6 "65"""$"++6 ++5""

"$"++6 6"5"""$"6+6 "$5""

"$"6+6 +-5"""$"6+6 6#5""

"$"#+6 "5"""$"#+6 +@5""

"$"-+6 "65"""$"-+6 ++5""

"$"-+6 6"5"""$"$+6 "$5""

"$"$+6 +-5"""$"$+6 6#5""

"$"(+6 "5"""$"(+6 +@5""

"0"

$0"+"0"

+$0"

6"0"

6$0"

#"0"

Temperature Comparison for Closed and 3penable indo's!utumn


Tempera

ture:C;


25/33

Figure 1+

"@+- "65""5""

"@+) +-5""5"""@+- +-5""5""

"@+$ "65""5""

"@+$ +-5""5""

"@+( "65""5""

"@+( +-5""5""

"@+@ "65""5""

"@+@ +-5""5""

"@+ "65""5""

"@+ +-5""5""

"@+) "65""5""

"0"

+"0"

6"0"

#"0"

Temperature Comparison for Closed and 3penable indo'sinter


Temperature:C;

Figure 1/

"@+- "65""5"""@+- +(5""5""

"@+$ "(5""5"""@+$ 6"5""5""

"@+( +"5""5"""@+( 6-5""5""

"@+@ +-5""5"""@+ "-5""5""

"@+ +5""5"""@+) "5""5""

"@+) 665""5""

"0"

$0"

+"0"

+$0"

6"0"

6$0"

#"0"

Temperature Comparison for Closed and 3penable indo's

%pring


Tempera

ture:C;


26/33

re 10

"6+$ "+5""5"""6+$ ")5""5""

"6+$ +@5""5"""6+( "+5""5""

"6+( ")5""5"""6+( +@5""5""

"6+@ "+5""5"""6+@ ")5""5""

"6+@ +@5""5"""6+ "+5""5""

"6+ ")5""5"""6+ +@5""5""

"6+) "+5""5"""6+) ")5""5""

"6+) +@5""5""

"0"

+"0"

6"0"

#"0"

"0"

+"0"

6"0"

#"0"

-"0"

Cooling ?oads and Temperature

2deal ?oads Total Cooling Energy:>h;, 3penable indo's 2deal ?oads Total Cooling Energy:>h;, Closed indo's


9ay&our

g

gy:

;

Temperature:C;

re 2

"$"++6 "65"""$"++6 ++5""

"$"++6 6"5"""$"6+6 "$5""

"$"6+6 +-5"""$"6+6 6#5""

"$"#+6 "5"""$"#+6 +@5""

"$"-+6 "65"""$"-+6 ++5""

"$"-+6 6"5"""$"$+6 "$5""

"$"$+6 +-5"""$"$+6 6#5""

"$"(+6 "5"""$"(+6 +@5""

"0"

60"

-0"

(0"

0"

+"0"

+60"

+-0"

"0"

$0"

+"0"

+$0"

6"0"

6$0"

#"0"

Cooling ?oads and Temperature

Closed and 3penable indo's, for !utumn 'ee>

2deal ?oads Total Cooling Energy:>h;, 3penable indo's 2deal ?oads Total Cooling Energy:>h;, Closed indo's


9ay&our

g

gy:

;

Temperature:C;


27/33

"his investigation found the encouraging result that there is a clear temperature and cooling load

benefit in the openable indos scenario and thus leads to further investigating the feasibility of a

naturally ventilated building! "o anser the .uestion of hether such a building could provide a

comfortable internal environment, the second comparative study investigates the thermal comfort

critera

1arrow versus Etended t!ermal com%ort criteria

"he second set of comparisons involve studying a model of the building ithout a mechanical

means of heating and cooling! "he goal of this study is assess hether such a building could

provide a comfortable internal environment! "o basic models, ith the Ideal 4oads $%AC systemremoved, are compared! "o parameters, clothing insulation and air velocity levels, ere varied

and the narro A$0AE standard as etended to account for these factors and for effect of

adaptation to the local climate!

"he results dran upon to ma)e these comparisons areK histogram data of thermal comfort as given

by predicted mean vote values for all occupied hours of the year, scatter plots of temperature and

humidity conditions and the comfort range as given by the tandard Effective "emperature method!

Discussion

"he A$0AE "hermal Comfort tandard provides a narro definition of comfort range as being

-M% values beteen =!3 and =!3! "his is illustrated for to clothing insulation levels as shon in

figure > "his is a very narro criteria and it is difficult for passive designs to achieve!

An epanded criteria is beteen 1 to 1 on the A$0AE "hermal Comfort scale! ;ased on this

epanded thermal comfort criteria, the results from the to models compared are shon in figure

?I/U0E, over the page! Using a constant clothing insulation level of 1clo and a constant air

7

Figure 21: #he 45- #her&al Co&fort -ange


28/33


29/33

Passive Building

A source of cooling can be provided by a Cooltoer! A cooltoer uses the evaporation of ater to

provide a flo of cool air to a space! As the 8ion 9ational -ar) %isitor Centre case study shos

#see ?igure &, this type of system is effective in hot, dry climates and can provide a reliable sourceof cooling ith very lo energy consumption #only a ater pump is necessary&

/iven the results found, hich have shon that the natural ventilation options investigated ould

need to be supplemented by some source of daytime cooling, a system of Cooltoers has been

modelled! "his is despite the author's opinion that the system as modelled is not practical! "his is

because they ould re.uire significant vertical space and retrofitting ducting to the building interior

to distribute cool air at lo velocity! 9onetheless, a model as implemented in hich these

practicalities are ignored and the cooling potential available from a Cooltoer is delivered to each

thermal @one in the building model!

=

>1

Figure 2+

%ilver !7 $" ?o' E%ilver !7 6$ ?o' E

%entinel - Mil Clear 3%%terling 6"

"

6"

-"

("

"

+""

"

"06

"0-

"0(

"0

+

#$

+-0-

@

+-0@

$@

@@06

+

@(

"0#@ "0##

"0)

"0(@

$+

6+0

)

660$

%olar Energy Transmitted TD Total %olar Energy 1eected

Thermal Energy Transmitted EmissivityG Visible ?ight Transmitted D

Figure 2/

Cooling:Mh; &eating:Mh;

"

+""

6""

#""

-""

&eating and Cooling ?oads for Various indo' Films

3utside eatherable %ilver6$ %ilver$" %terling6"

Energy:Mh;


32/33

Summary Discussion

While the climate provides a rather limited potential for night cooling, the results sho that an ideal

cross ventilation scheme can reduce the energy re.uired to cool the building! When cooling is

needed the most, in the hot months of +ecember, January, ?ebruary and March, the climatic cooling

potential is around 13degreehours, ell short of the 1==degreehours considered necessary for a

viable night cooling strategy #Artmann et al, ==7&! $oever, this measure doesn't account for the

cooling effect of the sea bree@e and still leaves open the opportunity to utilise night cooling, or

perhaps an allday cooling scheme, during the mild months! "he results of the investigation into a

building ith no mechanical cooling system sho that the internal conditions ould be comfortablefor a significant proportion of the year! "his is true for the narro definition that only a modern

high energy consumption $%AC netor) can provide and also by any reputable measure hich is

broader than this! "he results of a study of cooling provided by a lo energy evaporative system

using Cooltoers shos that an acceptable level of comfort is possible for most of the occupied

hours, approimately beteen 7= and := by the to methods discussed! $oever, this system

of cooling ould not be practical to implement and may result in humidity levels that some people

ould not find comfortable! ?inally, the results of the indo film analysis sho that a applying a

indo film to the eisting gla@ing can reduce the cooling energy re.uired by up >= !

Conclusions

"here are several conclusions to dra from this investigation into the feasibility of natural

ventilation in the Mechanical Engineering building! ?irstly, any scheme must account for the local

climate hich provides some potential for night cooling in the mild months, but demands some

additional source of cooling in the summer months! econdly, any scheme must deal ith the

constraints of the building's layout and geometry! "he prospect of effectively ventilating a space

ith many interior partitions is a challenging one! "hirdly, it is possible to improve the energy

efficiency of the building by enhancing the shading, by one or both of adding operable shades and

indo films to the eisting gla@ing!

>


33/33

References

O! "riantis PEnvironmental strategies in retrofitting of educational buildings Q "he integrated

approachR in International Conference P-assive and 4o Energy Cooling7=< for the ;uilt

EnvironmentR, May ==3, antorini, /reece

"he +epartment of the Environment and Water 0esources PE+ +esign /uide *ffice and -ublic

;uildingsR ==7 Melbourne

Australian tandards

Artmann, 9!,Ma@,$!S$eiselberg,-! ' Climatic potential for passive cooling of buildings by nighttime ventilation in Europe', Applied Energy %ol! :2, pp 1:7Q=1, ==7

Malhotra, ==>, '"he )noledge application gap in information systems research and education

and their .uest for the dependent variable',nfor&ation -esources Manage&ent 7ournal, vol! 16,

no! , pp! 17! Available from -ro.uest! F17 ?ebruary ==2G!

#+epartment of Industry, "ourism and 0esources ==6&

+epartment of Industry, "ourism and 0esources ==6, ;eing -repared for an Influen@a -andemic a

Bit for mall ;usinesses, /overnment of Australia, Available from

Thttp55!innovation!gov!au! F: ?ebruary == -erth

Documents

Tom Beckerling Natural Ventilation