Computed energy consumption for new and existing high-rise residential buildings: suggested norms and potential reductions

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Computed Energy Consumption for New and Existing High- Rise

Residential Buildings : Suggested Norms and Potential Reductions

Latta, J. K.

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COPiPUTED EmR# CONSUMPTIOH

FOR NEW AND EXISTING HIGH RISE RESIDENTIAL BUI LDlEJGS SUGGESTED NORMS AND POTENTIAL REDUCTIONS

J.K. Latta

A model apartment b u i l d i n g was developed based upon existing surveys

of such b u i l d i n g s and computer slmlations carried out to deterdne the

independent effects of climate and size on its energy consumption. Tbe

Meriwether Energy System Analysis program used

had

t h e s e r e s u l t s , data were developed which enabled a norm to be derived far

the energy consumption of any high rise apartment building at any location in Canada. The p o s s i b l e reductions fn energy consumption that w a d d result from the implementation of some fnexpensive modifications in the four

When work started in 1916 an the preparation of a code for energy

conservation

in

facets of the design to the best advantage. Under any such code, both the required performance, and the method of verifying that the level of perfor-

mance has been achieved, mst

be

To

any given building. This is co-mmonly referred to as the _{energy budget,} and is given as a quantity of energy per year for each unit that defines building s i z e ; usually t h i s is gross floor area but t h e number of apartraents

was found to be preferable w i t h residential occupancies- This quantity will

vary with the occupancy. The Standing C o d t t e e on Energy Conservaf ion in

Buildings, set up undec the Associate Committee on the National Building Code, established Vser Task Grwps to ensure that the energy budgets w e r e

r e a l i s t i c . Studfes were carried out an of Eice buildings, schools, and high rise residential bufldtngs.

Unfortunately, the secand basic requirement of a performance type of

code

-

-

The h s o c i a t e Committee thue decided that it could not issue a performance code a t this t'lmo. A prescriptive code, the Measures for Energy Conserva-

tion in Hew Buildings, had been i s s u e d in 1978 and is currently being revised, Oa the ather hand, the Associate C o d t t e e recommended that the results of the work on energy budgets should be publtshed by DBR to advfse designers

and

for

coaventional energy conserving d e s i g n s .

It

that

with

This publtcation Is one of three giving suggested norms of the energy consumption of offices, schools, and hdgh rtsc r e s i d e n t i a l buildings. The term "energy budget" has been avoided because of f t s association with a mandatory requirement.

INTRODUCT EON

Energy consumptfon of apartmeor buildings, eqreesed as energy used

either per square e t r e of floor area or per apartlment, shms a great

variation between buildings, even in the same location and subject to roughly _- t h e same weather conditions.

Table

surveys by varfws organizations

in

Lion of apartment b u i l d i n g s , Consumption

ranges

~ ~ / ( A p t * a ) t o a minimum of 39 ~ J / ( A p t d a ) .

In many countries a t t e m p t s have been made to develop norms for

reasonably attainable levels of

eaerw

s t b l e v a l u e s , at l e a s t f o r the destgn a€ new buildings. Recause b u l l d t n g s

l a s t a Long t l m e , d e c a d e s i n most casca and mlllenta I n t h e u l t i m a t e , it IR

probably more important to get reaeonable L e v e l s of c o n a m p t i a n for e x i s t i n g b u i l d i n g s . Unfortunately, thfa 1s IRIIC~I more d i f f i c u l t : rhan detexmlning what

I s reasonable for new buildings; u s u a l l y one reaorta to h t s t o r i e a l d a t a and

p o s s i b l e reductions £ram that l e v e l of consumption.

This Note presents the results of sow Canadian studies of energy

consmnption o f apartment buLldings and g i v e s

a

reasonable, but not necessarily optimum, level for new buildings. It also

gives some indication of reductions

in

be

EHERGY CONSUMPTION OF

MEW

The energy consumption mf a building is normally considered t o include

.l energy required to maintain conditions s u i t a b l e for human occupancy and

provide f o r normal human activity, but t o exclude e n e r a required for

some production process carried out: w i t h i n the b u i l a n g . In an apartment building there is no such production process and so all the energy required

far heatlng, cooling, operating elevators, ventf latirtg arid lighting p l u s

that used by the renants €or cooking, lighting and operating domesEic appliances, mid be included.

Butlding energy cansumption is affected by a multitude of factors,

including weather, amount

sf

effrteient d e s i g n p o s s i b l e , Many combinations of these factors w i l l give a

low energy consumption and not all of them will be applicable in a l l cases.

In

have

energy conserving practice when determining a reasonable l e v e l of energy

consumption f o r a new building. The requir-nts of the Measures for

Enerw

Conservation in New Buildings, published

in

innovative features should achieve a much lower value, as rnar~y are r aportedly dai ng.

On the other hand some factors are beyond the control of the d e s i g n e r

and these shauld also be taken i n t o account fa determining a reasonable

level of energy consumption for a given building. For this study, the t w o variables assumed t o be outside of the c o n t r o l of the designer werle the

climate and the size of

the

Methodology

The methodology used was t o "calibrate" the computational method by

comparing the computed energy consumption of fmr existing buildirtgs wfth

their known consumption. One of the four buildings w a s then .chosen as

representing a t y p i c a l a p a r t e n t building and the computer were

modified so that they represented a building that m e t the requirements of the Measures far !Suer= Conservatfon in New Building6

1978~.

used as a modal building for studying the effects of clfmate and s i z e treated as independeht variables. N b a t t e q t was made to investigate the tnceractton between them, Details of the study3 are glven -In Appendix A.

The mdel butlding w a s a 21 storey building contathing 231 apartments

and w a s considered to

be

in

ventilatiorl

a i r

supply to the corridor

and

i n f i l t r a t e at

the

lower

the upper floors

as

with

bufldings. Air infiltrated into and was exhausted from

the

spar tment"

.

It was concluded t h a t the energy consumptloa of an aparrtlbent b u € l . d i n g

could be divided i n t o four categories: kenant use., butldtne; s e r v i c e s ,

apartment heatimg and garage heating. Tenant Use

T h i s includes a l l the energy used within an apartment for lighting, cooling, operaZion og t e l e v i s i o n s e t s , refrigerator and small appliances as

well as that used for heating dnmestic hot water and for cooking. Bnilding Services

Building services comprise all those items needed to operate the

building other than the replacement of heat l o s t to t h e outsfda. Included

are exterfor lighting, lighting of public spacks, and the operation of elevators, fans and pumps, and c l o t h ~ s washers and dryers. Swiaming p o o l s

and saunas also come in t h i s category but are kept separate since they are

The energy required for some i t e m , such as corridor lighting, w i l l vary w i t h the number of apartments; for others, such as lobby lkghring, it

will not.

Apartment Heating

Although there is no physical connection between them, in Montreal t h e

sum of the i n t e r n a l and solar heat galns over the year was roughly equal to

the conductive heat losses through the envelope, The balance between these two factors In other loeattons was not investigated but since the Measures specify that the thermal resistance of the envelope s h a l l vary with the s e v e r i t y of the climate, probably the difference between

them is

large. Thus the heating requtrement of an apartment building depends

prtmarity on the amount

OE

1s coattolled by the ventilatfon system3 and so is reLated t o the number of apartments rather than to the overall dimensfons of the building.

With a constant rate of ventilation per apartment and a constant inside

temperature, the heating requirement can be expressed as a linear r e l a t i o w

ship with degree days.

It

Garage Heating

The garage heating requirement a l s o varies linearly with the degree

days but equals zero t o approximately

1250

Determination of the

Enerm

New Buildin&s

The energy norm for a gPven building should be expressed In terms of energy d e l i v e r e d t o the building

since

t o rhe calculated norm. Thus, account must be caken of the seasonal

eEEiciencies of t h e various itma of conversion equipment, which can be taken as 100% €or e l e c t r i c i t y bat only about 70X or less for o i l or g a s .

Heating requirements can be met using gas, o i l , or electricity, but e l e c t r i c i t y is used almost exclusively for a l l other requf renwnts. Heating is required For domestic hot water and the g w i d n g pool in addition to the apartment and garage heatlng, so t b calculated energy requirement for rhese items must be divided by the seasonal efficiency

of

conversion

to dertve an energy norm i n terms o f delivered energy,

The energy norm for a given b u t l d l n g can be obtained by determining t h e energy requirement for its various components {from Table 2), dividing each by the appropriate seasonal efficiency of the equipment and adding the resulting quotients. An example of the use of t h i s is given in Table 3,

Table

4 g i v e s

several locations i n Canada both wlth e l e c t r i c heat: and w f t h o i l _{or gas}

heat. Comparing the values for recorded energy consumption glven in Table 1 wlth the n o r m f o r t h e Location shaws t h a t t h e minimum v a l u e s are o f t e n

lower, indicating that; the norms are reasonably attainable. On the locller hand, the average values are well above the norms in most cases, indtcatlng

that a considerable amount of energy c o d d

b~

bu-flt t o the n s m , The exception to this is the average masumption of the e l e c t r i c a l l y heated Ontario Rousing Corporation buildings in Ottawa. These buildings do nor have garages and the supply and exhaust ventilation faos are operated for a total of m l y n i n e hours p e r day, with an additional low

temperature shut-off- Wbile by no means Xdentical, this is similar t o

Variation 4 i n Appendix l3, where the bathroom exhaust runs continuously but the c o r r t d o r supply and the kitchen exhaust operate for a t o e a 1 nf six: hoar:: per day. Under Montreal weather condlt$ons, that v a r i a t i o n saved 2 1 - 6

GJ/(Apt-a) relative to the norm where the fans run cantCnuousLy. D e d u c t i n g

t h i s savFng, and the

8.4

b u l l d i r ~ g in Montreal gives a f i e M norm of 46 _{GJ/(Apt*a), which I s less than} the consumptlon of a l l but three of the O t t a w a buildings. OtLawa has 4674 Degree Days Celsius and Montreal

4472,

ENERGY CONSERVATION IN EXISTING RUTWIHGS

In

are

new

reducing energy consumption in existing buildings was investigated by

artalyaiug the

four

scheduling Che recirculation of domestic hot watrer, i n s t a l l a t i o n of law flow

shower heads and faucet aerators, reducing the garage temperature and the lightlng of p u b l i c space-

The results of the various analyses (Appendix A) fndicated

that

consumption of the b u i l d i n g could be reduced by between 8 and 14% through

the implementation of

l o w

any given building, Actual target values of energy consumption €or existing b u i l d i n g s have not been determined and i t may not be p o s s i b l e to d e t e r m i n e

representative values because o f the great variation 111 f a c t o r s tllat can

reasonably be changed in e x i s t i n g b u i l d i n g s . There are, however,

substantial energy savings t o be made by implementing energy conserving

procedures which can be fdentified

by

1, A.H. Elrdahdy. Annual Energy Consumptf.on Data of Apartmat: Buildings,

N a t i ~ n Z i l Research Council of Canada, Division o f Building Research, Buildfng Rsearch Note Wo. 181, Ottawa, 1982.

2, Measures For Energy Conservation i n New Bulldings 1978, Associate Committee on the N a t i o n a l Ruildtng Code, National Research Council

of

Canada, fittawa, 1978. W C C Nn. 16.574.

3 . Slone, C h a l i f o u r , Marcotte, et A s s . , 4 Srudy of the E f f e c t s of S o m e Parameters on

the

for National Research Counctl of Canada, Division of Building Research, O t t a w a , 1980.

4. J.K. Latta- A Field Study of Infiltration-Induced Variati,ona in the Heating of Apartments, National Research Council of Canada, D i v i s i o n of B u i l d i n g Research, Building Research Note

No.

5. L- Jones. The Analyst as a Factor in the Prediction af Energy

knsrmop t i o n . Second International CII Symposium on Energy Conservation in the Built Environment. Copenhagen, 1979. 313-321. NRCC 18488.

4 . Energy Conservation ImpLLcations a f Master Metering, Vnlume 1 6 2.

Y I d w e s t Research K n s t Ltutc, October 1975.

7. Ontario R e s i d e n t t a l and Commercial Energy Demand Study, Ontario Ministry

of Energy, Toronto, 1978.

8 . How you U s e the Energy you Use, Conserve Energy Publication, Ontario Hydro, O t t a w a , 1976.

9. C.Y. Shaw and

G.T.

Caused by Wind and Stack Action of T a l l Buildings, National Research

TABLE I . SUMMARY

OF

APARTMENT BU I LDXNGS

Energy Consump tion

Sample

CJ/

Group Size Maximum Minimum Average

Ontargo Boustng 1975

Corporation (Toronto] 1976 1977 1978

O n t a r i o Hydro

Apartments (~ontreal Area) Ontario Housing 197

7

Corporation (Ottawa) 13

1978

l ~ e e Discussion.

TABLE 2. COMfONENT ENERGY RBQUXRIEMEMTS

Tenant Use

Lights

,

Building Services Canstants

1

swimming pool requiremnc

Variable with number of apartments

SO Apartments 12.6 G J / ( A p t - a )

100 Apartments

10.8

200 Apartments 7.9

G J / ( A ~ ~ - ~ )

300 Apartments 6.8 GJ/(Apt* a)

400 Apartments 6.5 G J / ( ~ p t * a )

Intermediate values can be o b t a i n e d

by interpolation

Heating Requirements

ApartmenL [U.0085 X (DDC)] GJf(Apt0a)

Garage

[0.0026

-

TABLE 3. EXAMPLE

The energy norms Eot the model building

in

and one garage space per apartment, but: without a s w i d n g p o o l , can be

computed as fallows, both for an a l l electric building and for a gas heated

building, assuming a seasonal efficiency of 70% for the gas f f r e d e q u i p e n t .

Energy Requirement

G J I

B

Variables (by interpolatton) = 7.6

%eatfng - Apartment 0.0085 x

4472

-

4472)-3.24

Total 75.5 99.3

'rhRLE _4. ENERGY CONSUMPTION N O W FOK TiiE MODEL APARThfENT BUILDING*

DDC G J I _{( A p t - a)}

ALI Electric O i l or Gas Heating

Vancouver 3005 Edmonton 5590 Regina 5 9 2 1 WFnnipeg 5887 Toronto 6082 Montreal

4472

The energy consumption of any building is a£ fected by a number of factors: weather, materials used fn its construction, type of mechanical and electrical s y s t e m installed, number of hours of occupancy during whf c h condftioned space I s necessary, nrethod of operation, and quality oE

maintenance. Same of these the designer can control, others he cannot. The effect of this great variety of factors is

shown

in

enerw consmption of about 200 apartment buildings across Canada, which had

energy consumptions ranging from 305 GJ/ [Apt. a) t o 39 GJ/ (Apt. a). With such

a variation, the effect

oE

could not be determined by examining existing consumptions; computer

evaluation of the effect of selected variables

was

wlth the analyst because oE differences i n judgement as to the cfirrect inplit: values. The energy aaalysis program used to derive the energy coosumpelon formulae was "calibrated" by matching the calculated energy consumptions of

our buildings with

their

consumption of a model bullding.

It

affected the energy consurrrption of a model bufldtng t y p i c a l of most new

buildings in i t s d e s i g n and operation, would also Indicate the way they would affect the enerm consumption of any n e w building.

The procedure then was to select four extstfng apartr~ent b u i l d i n g s with knawa energy cansumptiom and to simulate their performance using the

Meriwether Energy Systems Analysis program. Because documentation of

operational procedures was, at b e s t , minimal, it was

d l £

o p e r a t i n g procedures were determined by c l o s e examination of the data given by the operator and any discrepancies were discussed w i t h him. Where data were n o t available, a reasonable method of operation was assumed.

Attempts were also made to match the monthly energy consumption. Thls

proved d i f f i c u l t as w e l l , and may have been due in p a r t to actual energy

consumption values n o t being recorded on the calender months. Some

adjustment t o them became necessary* When the c a l c u l a t e d annual consumption

was within 5% OE that retarded, and any major v a r i a t i o n s in monthly values

could n o t he eliminated by further crlnputation because of the impassibtl-lty nf determtolng appropriate i n p u t v a l u e s , the program l r ~ p u t s Mere c o n s i d e r e d

acceptable.

The characteristics

of

be

bedroom and

6Z

this

d e s c r i p t i o n exactly but one of them, alkhmgh of 2 1 storeys, was reasonably close. Since the s i z e of the building was to be varled during the course

of

a

with

i e

_as

cequt rements of the Measures for Energy Conservation

in

,

were modified as

if

b u i l d i n g were made to determine the ef Eects of changes in c l i m a t e and s i z e

an its energy requirements.

The energy requf remnts of the building were separated into four categories: tenant use, b u i l d i n g services, apartment: heating and garage heating. Tenant use includes all electrical energy for lfghting, cooking,

telev&sien and small appliances, and energy used for domestic water. To select a r e a l i s t i c average value for tenant electrical use, the i n d i v i d u a l e t e c t r i c t t y constunptlans for one buildlng with individual lwtering w e r e

examLi~ed and reports artd publications oE t h e Midwest Reseprch 1nstltute6, the Ontario Minis t r y of energy7, and Ontario ~ y d r o ~ were consulted.

Building serflees Include f i g h t h g of lobby, corridor, exterior and p u b l i c spaces, laundry facilities, e l e v a t o r s , pumps, supply

aud

A p a r t m n t heating includes the heating required t o offset transmission and infiltration loads as well as energy used t o condition the a f c supply to the

corridor, The garage load includes

r k

The energy consumption of a building is normally given in term!$ of the

energy d e l i v e r e d t o the h l l d i n g , s i n c e this is what is recorded at the meter. This quantity will vary n o t only wlth the _construction of the

building but with the type of conversion equipment used, particularly the heating equipment. Buildings that are otherwise i d e n t i c a l will require dffferent quantities of d e l t v e r e d energy depending upon whether they use

e l e c t r i c i t y for heating as opposed t o oil or gas, because of their dtfferent conversion efficiencies within the buildlrtg. To overcoue t h i s problem in the development of energy narms, the required output of the conversion

equipment, rather than the fnput, was conputed. S u i t a b l e adjustment Eactors could then be applLed t o the hearing requirements ta allow Enr the

efffciency of the equipmedt.

A major p o r t i w of the heating requirement of a building is that needed to heat the ventilation and infiltration a i r passing

through

a p p l i e d for relatively leaky walls w i t h openable wi~~dows and ttghter tnterior d i v i s i o n s . In addition, a f i e l d study considered variations

in

heating requirements with height4

.

induced by stack effect and d u d pressures was overridden by the demands of

the bathroom and kitchen exhaust fans. Thus the quantity

of

through an apar.t:mnt

is

Attention was

then

towards

c w l d be made

the

are

are

the

from

The model building, with its basic ventLlation system of an air supply

of 35 L/s to the corridor and a total exhaust from the apartments of 7 1 L/S, was then used to examfne the energy requirements under the weather

conditions of Vancwver, Saskatooa, Montreal and S t . John's, N f l d . The computer inputs were adjusted for each location in conformity w i t h the r e q u i r e n t s of the Measures2. The height of the bulld3ng was a l s o varied between

7 and 35

P i n a l l y , the p o t e n t i a l for energy conservation in existing apartment

buildings was investigated by analysing the effects of reasonable changes that could lx implemented

In

A1

TABLE AL Reductions in Energy Cansumption as a Result of Low Cost Enerey Conservation Pieasures.

Six

Montreal.

Cooservation measures implemented

1. Domestic hot water temperature reduced from 51°C t o 46°C 2. Domestic hot water recirculation shut o f f from

11:W

7:00 a . m ,

3, Central kitchen exhaust fans run only from

7:3Q

-

-

4. C e n t r a l t o l l e t exhaust Eans s h u t o f f Prom L1:00 p.m. - 7 : 0 0 a - m , Usage Tenant But l d i n g services Heating apartment Garage As found, modif i c a t i a n s

,

GJI

TABLE A2 Reducttons in Energy Cansumption as a Result of L w C o s t Energy

Cowervation Measures. 21 Starey Building, 252 Apartmnts, M n t real.

Conservation measures implemented

1. Domestic hot

water

2 . Domeetic hot water recirculation shut off from

1l:OO

3. Toffet exhaust fans

shut

4,

-

7:CQ

5. Corridor supply fan shut o f f from 9 : 0 0 p.m.

-

6 . Kitchen exheast rebalanced to 35 L/S per apartment from

47

p e r apartment

7. Corrido=' supply reduced t o

_{24 L/S per}

apartment

8 . Swimmiag pod1 supply untt shut off from 10:00 p.m.

-

9,

LO.

Usage Building services Resting apartment Garage After As found modifications

TABLE

A3

LOW

Conservation measures implemented

I . Domestic hot water temperature reduced from 60°C to 46°C

2. Domestic hot water recirculation shut off from 11:QO p.m.

-

3. Central kitchen exhaust fans

run

-

11:OQ a.m.

-

-

4. Central t o i l e t exhaust fans shut off from midnight to 7 : 0 0 a . m .

5 . Corridor supply operated on same time schedule as kitchen

e x h a ~ s t f a n s

6 . Corridor supply reduced to 24 L / s per apartment f r o m 35 L/S per apartment

7.

8. Corridor, lobby and exterior lighting reduced by 1SX 9 . Garage temperature reduced from 21°C t a 1O0C1

Usage Tenant Ruildlng services Heating apartment Garage Total As found GJ/(Apt*a) Mter modifications GJ/(Apt*a) % reduction

TABLE

A4

Conservation Measures. 10 Storey Building, 227 Apartments, Montreal.

Conservation measures implemented

1. Domestic hot water temperature reduced from 60°C to 46°C

2. Doraestic hot water recirculation shut off from 11:00 p.m. - 7:00 a.m.

3. Central kitchen exhaust fans run only from 7:30

-

-

-

4. Central toilet exhaust fans ,shut off from midnight to

7:QO

5. Garage temperature reduced fr- 21°C to 1 0 ° C -

Usage Tenant Building services Heating apartment Garage As found GJ/ (Apt a) After modifications G J / ( A ~ ~ * a) X reduction

REDUCTIONS I N ENERGY CONSUMPTION

IN

LOCATED

IN

VENTILATIOM

The vent2lation system in the model building supplied fresh air to the

corridors at a rate of 35 L / S per apartment and exhausted stale a i r from the

kltchen and bathroom of each apartment a t a cmbined rate of 71 L/s. The

difference of 36 L / s per apartment is considered to be mde up by infiltra-

tlan. Various changes to this basic method of ventTlat1on were fnvestigated t o determine _{t h e i r effect on the energy c o n 8 u q t i o n}

_of

Basic Case

S u p p l y to the corridor of 35 L/S running for 24 hours per day. Exhaust from che k i t c h e n of 47 L / s and the bathroom of 24 L/S running for 24 hours p e r day.

Variation 1

As per the basic case, with the addlrion of an air-to-air heat

exchanger with a 50X efficiency to preheat

the

Variation 2

As per the basic case, but with the exhaust discharging into the garage, which I s maintained at 13°C.

Variation 3

Supply t o the corridor reduced to 28 L / s per apartraent and exhausts from the kitchen and bathroom reduced to 38 L/S and 19 t / a per apartment tespect i v e l y

.

Variation b

As per the basic case, w i t h time scheduling of the corridor supply and k i t c h e n exhaust so that, they run far a t o t a l of fi hours per day. The t o i l e r exhaust ran continuously

-

Variation 5

Supply t o the corrldor &f 17 L/S per apartment running continuously- Exhaust froa the kitchen and bathroom with small individual fans operating on demand only, i . e., when the room was occupied.

RESULTS

Variation Saving, GJ/(Apt*a)

1 8.6

.2 7 - 9