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Canadian experience regarding the preparation of energy budgets for
office buildings
Ser
TH1
N21d
no.
919
cop.
2
National Research
Conseil national
1
Council Canada
de recherches Canada
.*
CANADIAN EXPERIENCE REGARDING
THE
PREPARATION
OF
ENERGY BUDGETS
FOR OFFICE BUILDINGS
by
G.F.
Bounssa,
J.K.
Latta,
A.J.
Thornson,
S.
Housch and
R
Monteyne
Reprinted,
with
permission,
from
Proceedings, Second International
CIB
Symposium on
Energy Conservation in the Built Environment
Session
4,
Copenhagen 1979
DBR
Paper
No.
919
Divioion of Building
R
d
This publication i s being distributed by the Division of Building R e s e a r c h of the National R e s e a r c h Council of Canada. I t should not be reproduced i n whole o r jn p a r t without p e r m i s s i o n of the original publieher. The Di- vision would be glad to be of a s e i s t a n c e in obtaining such permieeion.
Publications of the Division m a y be obtained by m a i l - ing the a p p r o p r i a t e r e m i t t a n c e ( a Bank, E x p r e s s , o r P o s t Office Money O r d e r , o r a cheque, m a d e payable t o the Receiver General of Canada, c r e d i t NRC) t o the National R e e e a r c h Council of Canada, Ottawa. K1A
OR6.
Stamps a r e not acceptable.
A l i s t of allpublications of the Division i s available and m a y be obtained f r o m the Publications Section, Division of Building R e s e a r c h , National R e s e a r c h Council of Canada. Ottawa. KIA OR 6.
CLMdian experience regarding the preparation of energy W q e t s for office buildings
-. .- . .
by G.P: Bourassa, Yon& s Associates ~td., 1905-7th Ave., Regina, Canada. J.K. L.tta, Research Officer, Division of Building Rasearch, National
Research Council of Canada, Ottawa, Canada.
A.J. ThoPwn, Yon& 6 Associates, Ltd., 19057th Ave., ~ a g i n a , Canada.
8 . Houmh and R. Monteyne, Vinto Engineering Ltd., 10950-119 Street, Edmonton, Canada.
--1-~_1--1----__-__11---I---
S u m a r y . An extensive apalytical study of the energy consumption of Curadian office buildings was c m i s s i o n e d by the National Researchcouncil of Canada as part of an effort to establish energy budgets for buildings with various occupancies. The results show that climate and shape can be allowed for by means of simple formulae; that size is not important but height is because of its effect on infiltration. The effect of the period of occupancy needs to be studied further. Significant reductions can be made in the energy c o n k p t i o n of existing buildings without major capital expenditure.
. . . . . . . - . . - - - - . .. . . - . .
L'expdrience canadienne en ce qui regarde la preparation de budgets d'6nargie pour lee immeublee B bureaux
IIIC--L-_~___llfC---l--l--l---ll--
par
C.F.
Bourasra, 'Yoneda 6 Associates Ltd., Regina, Canada.J
.K.
Latta, htional Rerearch Council of Canada, Ottawa. Canada. A.J. Thornson, Yoneda 6 Arrociates, Ltd.. Regina, Canada.8 . H o w c h and
R.
Montayne, Vinto Engineering Ltd.. Edmonton, Canada.----llr-3---d----r--u---l----r---
Mrurl. Una Ltude analytique pours6e de la consommation d'anergie dansles immeublaa
A
bureaux canadlens a 6tf commend€e par le Conseil national de rrcharchar du Canada dana la cadre d'un effort visant B itablir desbudgets ~nargttiquer pour des bgtiments B usages divers. Lee risultats dimontrent qu'on paut tanir compte du climat et de la forme B l'aide de formules miuplor at qua la grandeur n'est pas importante, mais que la hauteur l'est & caul. da l'effat rur l'infiltration. L'effet de la pCriode d'usage doicL t n
m a o r e btudi6 plus longuement. Des riductions significatives de la C O n 8 0 ~ t l 0 n d'6nergie der bstiments existants peuvent Ztre rialisies sans Reand dlboura€ da capital.---
Canadian experience regarding the preparation of energy budgets for off ice buildings
---CIL--
-About one third of the energy consumed in Cuuda is used in buildings for hating, cooling, lighting and ventilation. In the past, when energy was oheap, buildings were designed and operated with little consideration for the a ~ o u n t of energy they used. Thus, reduction of the energy consumption of buildings can play an important role in any program of energy
c o n a m t i o n . To assist building designers and operators in their endeavors to achieve this reduction, it is desirable that the reasonable level of consmption be established for any building. This energy budget could than become the norm to which different buildings and designs could be compared and, if need be, made mandatory.
It is inherent in the concept of a performance type of specification or o d e that the designer be left free to balance the effect of various featurem of a building to the best effect. Thus, tha effects of only thome itemo that are largely outside his control need be allowed for when aatting energy budqats. The type of occupcmcy is much an item and this paper prementr the remults of an extensive mtudy carried out for the Division of Building Research, National Research Council of Canada, by the arlociated firms of Vinto Engineering Ltd., and Yoneda 6 Asoociates Ltd.,
of the effectm of climate, sire, shape and period of occupancy on the W e n E y conmrrmption of offioe buildings. In addition, the potential for raduoing the energy consumption of existing buildings through the
application of lorcost energy management procedures was alao investigated. A r W i e v Of the available information about the energy connrption of 0ffioe building8 revealed no discernable pattern. This is not really murpriming in view of the lack of attention paid to the subject in thepast and the tr-ndoum variety of designs of building. To determine theeffect
of various factors on a building's requirerent for energy, reliance must therefor* b. P l a c d upon computer simulations. As is reported elsewhere (12
m a r , the v a r i a b i l i t y of t h e r e s u l t s obtdined, with d i f f e r e n t roaputer program and d i f f e r e n t a n a l y s t s applying t h e same program t o t h e sane building, makes it v i a l t h a t these s i a u l a t i o n s be corroborated by collp.riwn with t h e energy c o n s u p t i o n of a c t u a l buildings. mehoQ1ogy
Th p r o c d u r e adopted vas f i r s t l y to e s t a b l i s h t h a t the computer prograr rnuLd give r e a l i s t i c r e s u l t s by using it to simulate four representative e x i s t i n g buildings covering a wide range of energy consumptions [620 t o 3100 &T/(n2-year)] with d i f f e r i n g mechanical systems and subjected t o widely varying c l i a a t i c conditions. The one considered to be = S t
representative of contemporary o f f i c e buildings i n Canada was modified to
camply with c u r r e n t building standards and idealized operating procedures ( d e a c r i k d in t h e Canadian "Measures f o r Energy Conservation i n New
Buildings 1978," (2) and in ASH= Standard 90-75. I t was then used a s a lod.1 building i n studying t h e independent e f f e c t s of climate, s i z e . Shape and hours of use. Finally, t h e o r i g i n a l four buildings were examined from tho point of view of an ownet, and a l l reasonable energy conservation m a r u r e s t h a t such an m e r could adopt were applied to see vhat e n e r w budget w u l d be appropriate i f e x i s t i n g buildings were to be upgraded.
?our locations, Vancouver, S a s h t o o n , Montreal and St. John's, were used i n rtudying tho e f f e c t s of climate. The e f f e c t s of s i z e , s h a p and ocoupurey w r e studied under t h e c l i m a t i c conditions o f Edmonton, which
h a one of tho c o l d e s t c1Laat.s of any major c i t y i n Caruda. Energy ~ ~ g l o n t m s u r e s m n sirnulatad f o r climates a t the l o c a t i o n s of t h e a a t \ u l buildings i n Edmonton, Regina, Vancouver and S e a t t l e .
C o n f i m t i o n of t h e v a l i d i t y of the simulation technique
X c o n g r r i s m of t h e rooordad energy consumptions of t h e four buildings and
Ch* aomputed consumptions f o r tho corresponding year and locations showed t h a t it -8 paasible t o obtain agreement within 210 par cent. Further, i t war poS*ible t o match olosely t h e i r month by month energy use. The major problanr encountered i n simulation were associated with temporary manual alterOtion8 of t h e way t h e s y ~ t e m operated th.t could not bc simulated i n t h e program, and monthly v a r i a t i o n s In u t i l i t y d a t a r e s u l t i n g from non- o m s i r t e n t periods batmen meter readings. Despite these d i f f i c u l t i e s , t h e b r i w e t h e r ESA Cornputor Programs were found t o give reasonably acourat* simulations of a c t u a l buildlnq operation over a wide range of onerqy consumption levels.
climate
four location*, having different climate canditions. and to reflect current building practice in these areas, e.g., single glazing in Vancouver and double glazing in Saskatwn. Its operation for a full year was then simulated. The hypothesis that enerqy consumption per unit of gross floor area increases as heating degree days increase was confirmed and the follwing linear ekpresssion was found to best represent the results:
Y = 0.064X
+
38 2 where Y = heating requirements in W/(m 'year)X heating degree days at 10.0 degrees Celsius base.
It vas also determined that energy consumption per square metre and gas c o n s ~ ~ p t i o n correlated with heating degree days, but that electrical consraption was not related.
With respect to cooling, the linear regression best fit was as follows:
Y1 = 0.160X1
+
21 (2)2 where Y1 = cooling requirements in MJ/(m .year)
X1
-
cooling degree days exceeding 12.8 degrees Celeius as a base. It W8S also found that tho total gas and electrical conslnnptions were not related to the cooling degree days, but that the fan electrical consumption was.A multiple linear regression was performed on the variables, heating and aooling degree days, with the following equation providing the best prediction :
Y2 = 0.07X2 + 0.18X3
+
695 2whore Y2
-
energy consumption in w / ( m *year)X2 = heating degree days below 10.0 degrees Celsius
X3
-
cooling degree days exceeding 12.8 degrees Celsius. The cooling and heatins degree days accounted for 83 per cent of the variation in energy consumption for samples tested.aiao
-
The roof of an office tower forms a relatively small part of the total building envelope, and in the model building it was largely covered by a mochinical penthouso that was not maintained at the same conditions as the reat of the building. Thus, it was considered that the effect of the roof War n*gliqible and that the size of the building could conveniently be M i f i e d by changing the number of storeys without altering the ratio of onvelope-to-floor aroa. Five sizes of building were simulated, ranging
2
in aqua1 increments from one of three storeys with 3056 m of floor area to 2
war-all energy consumption per unit area of floor increased with building si&e whmn the envelope-to-floor area ratio rerained constant. As a representative buildinq cannot be considered airtight, however, allowance for infiltration was included and therefore a third variable was actually introduced. A linear regression test confirred that the increase in infiltration rate, principally due to stack effect. accountedfor 9 9 p e r c e b
of tAe increase in energy consumption. Further, tha increase in over-all
energy c o n q t i o n was caused by the increased heatinp energy requirement only; other constituent requirements remained constant.
shape
In contrast with the size manipulations described, wherein the envelope-to- floor area ratio was held constant with increasing floor area, the shape mnnipllations required the total floor area to remain constant while the envelope-to-floor area ratio was varied. Simulations were carried out on variations that were considered feasible (e.g., representative of COntWI- porary building practice). The manipulations ranged, therefore, in varying increments f m m three storeys, having an envelope/floor ratio of 0.49, to 36 storeys, having an envelope/floor ratio of 0.78.
Typically, there is a substantial difference in the U value of roofs and Walls, 80 that in order to utilize the envelope-to-floor area ratio as a ua.ure of shape the effect of differing thermal transmission propertiesof walls and roofs had to be eliminated. This was done by using an "adjusted" onwlopo/floor ratio in which tho roof area is reduced in the ratio of the 0 v a l w s for tho roof and walls.
[d
x roof a m ]+
a l l areaadjumtod t/F m (4)
floor u e a
Utili~ing adjumted E/F tatiom, the linear repression best fit curve was as followr I
Y3
-
1 8 6 0 ~ ~+
310 (5)2 whore Y j
-
onorgy consumption in M / ( m *year)Xq
-
adjustod envelope/floor ratio.The b i g h t of the buildinq varied, hoGever, from 3 to 36 storeys and, as
for
size mnipulationm, infiltration was a significant factor in the variation in energy consumption.That shape and infiltration rate per square metre are related is not surprising. Both are calculated on the basis of the length, width, height and area of the building. Thus a change in shape will result in a change in infiltration rate per square metre of floot area. The sizemanipulation
indi~ated that a 220 per cent increase in infiltration resulted in a 13 par cent increase in enerqy conswtion. In the shape manipulation the infiltration rate increased 860 per cent (3.7 times as much as for size) while energy consmption changed 102 per cent (7.8 times as much as for size). Thus, although infiltration should be taken into account when predicting energy consumption, the envelope-to-floor area ratio also has a significant effect on energy consumption.
Size/shap interaction
Them is an interaction between the two variables of size and shape and, in gmeral, the envelope-to-floor area ratio of a large building will be smaller than that of a small building. As plan dimensions increase, the floor area increases more rapidly than does the wall area, and as extra storeys are added the roof area becomes progressively a smaller fraction of the total envelope area.
A. has baen shown by the investigatioh of the tim variables of size and
ahape independently, changes in energy consumption are largely, if not atirely, caused by changes produced in the rate of infiltration. Thus, additional manipulations were carried out and all the results analysed to determine the interdependent effects of the three variables of size, shape
and
infiltration.A multiple linear regression produced the following relation:
Y4
-
1 1 2 0 ~ ~+
610x6+
500 (6)2
where Y4
-
energy consumption ink / ( m
.
year)X5
*
adjusted envelope-to-floor area ratio2
X6 infiltration rate in L/(s0r of floor area.
I f one adopts an awpaqe value of 0.5 for the envelope-to-floor ratio from
4 praatical range of 0.3 to 0.8, and an average infiltration rate of
2
0.26 L/(s-m ) of floor area, then an indication of the relative importance of the two parameters can be abtained frcm equation (61, which gives
Y4
-
562+
171+
500 = 1233 ~/(m'*~earlF m m this it appears that the infiltration component, 171,is approximately one third the value of the shape component, 562.
Hours of occupancy
Another parmeter that was expected to influence energy consumption ~ignificantly was hours of occupancy. Operating profiles for 8, 12 and 16 h0Urs per d a y were estahlishd, patterned on contenporary building
Opration, and 5, 6 and 7 days per week (including holidays) of occupancy wore Studied. The matrix of hours per day and days per week did not, ~vOr, include a11 possible combinations.
hLing into account both variables, a multiple linear regression a l y s i s resulted in the following relations:
Y5
=
2.95+
59.7X8-
222 ( 7 ) 2Y5
-
energy consumption in W / ( m 'year)X7 = days of operationper year (betwen 252 and369
X8
-
hours of operation per day (between 8 and 16) Enorgy amnagamantTho final p h w of the study involved application, by simulation, of a logical onorgy n u r u g m n t program to the four representative buildings m01.ct.d for the first portion of the study in order to ascertain potential
saving. in energy consumption. It appeared appropriate that the proposed rovimions to building systems should be categorized according to expendi- t u n , in that the usual approach to energy management for most building ovners is to identify firstly the changes involving minimal or no cost and to prrteue less enthusiastically those requiring significant expenditure. Thus the revisions were grouped in categories of "No Cost" and "Minor Cost" for tho purpose of simulation.
Starting from the base energy consmption of each building, the No Cost (e.g., negligible capital cost of adopting the measures) items were shula-
tad as a group to establish a new base energy,cons\rmption. Following this, tho Minor Cost items were simulated in order of increase in cost.
Tho -sums identified are operation and control oriented as opposed to thome th&t rmuld i n v o l ~ u t e n s i w system changes. They involved shutting off equipmnt and lights where not required, reset space temperatures during unoccupied period., revised conditions for temperature hnd humidity in wcupird rnp.com, control of the supply air temperature according to the Sp.90 dawnd and the ambient air temperature, changes in lighting levels, roauctlon in tho temperature of domestic hot water, reduced air flow rates and minimum permisriblo quantities of outside air, the use of outsida air for cooling and lover chiller condenser water temperature.
Tho ramults Of the various simulations have indicated clearly that si(~ific8nt onergy savings can b. achieved through l w expenditure
revi0iMs. The reduction in over-all energy consumption for the buildings studid indicated reductions of 44 to 50 per cent, resulting from applica- t i M of Na Cost itms. Applications of Minor Cost revisions provided
further uvings, leading to a t o m 1 saving in the order of 60 per cent of ovcrr-all en- consumption.
I t .pp.ars rrclmnable to conclude that a comprehensive study of possible .n*W aaving pmcedures will provide significant results, although the
d i r e c t e f f e c t of each p a r t i c u l a r measure w i l l vary f r m b u i l d i n g to build- i n g and between a r e a s with d i f f e r e n t climates.
Conclusions
This study has been d i r e c t e d towards providing guidance t o standards v r i t i n g bodies regarding the f a c t o r s t h a t should be taken i n t o account in
s e t t i n g energy c o n s ~ t i o n l e v e l s . I t was a l s o designed t o d e f i n e how energy budgets should be a d j u s t e d to take t h e s e f a c t o r s i n t o account. I t
has had considerable success i n achieving both of t h e s e g o a l s , but has a l s o arposed a r e a s t h a t r e q u i r e f u r t h e r study. I n p a r t i c u l a r , t h e i n t e r - dependence of t h e f a c t o r s needs to be examined s o t h a t methods can be devised of s e t t i n g an energy budget f o r any o f f i c e building i n any location i n Canada. Similarly, when consideration i s being given to improved energy m n a g e m n t in e x i s t i n g b u i l d i n g s c a r e must be taken to ensure that t h e complicated i n t e r a c t i o n of v a r i o u s b u i l d i n g systems does n o t cause a measure t h a t reduces energy consumption under one set of circumstances t o incraamr it under another. Within t h e e l i m i t a t i o n s some conclusions can
ba drawn.
Climate i m of grmat importance, a s was to be expected. I t s e f f e c t can raamonably be allowad f o r on t h e b a s i s of heating and cooling degree days. Thema should, however, be based on 1 0 ' ~ f o r h e a t i n g and 1 2 . ~ ~ ~ f o r cooling r a t h e r on t h e conventional North American f i g u r e of 1 8 . 3 ~ ~ .
The study, a; conductad, of t h e e f f e c t of s i z e d i d n o t show t h a t
mi.., por ma, is important. I t d i d show t h a t height has g r e a t influence bocauma of t h e e f f e c t s of i n f i l t r a t i o n . Even so, s i z e should not be d i d m m a d , i f only k c a u s e of i t s e f f e c t on t h e envelope-to-floor a r e a
ratio.
I n f i l t r a t i ~ vas a s i g n i f i c a n t f a c t o r i n the study o f t h e e f f e c t s of mhap., am axpresmad by t h e r a t i o of envelope-to-floor area. I t vas not. howvar. the dominant f a c t o r and shape was shown to be of g r e a t e riBI$-Ort.ncm. I f i n f i l t r a t i o n i s c a l c u l a t e d s e p a r a t e l y , t h e combined e f f e c t . of . h a p and i n f i l t r a t i o n can be allowed f o r by means of a simple equation. I n f i l t r a t i o n is not, howaver, a d e s i r e d f e a t u r e , occurring l a r g e l y through unintanded opaningm, whereas height is fundamental i n its e f f e c t on the mhck e f f e c t t h a t a f f e c t s t h e degree of i n f i l t r a t i o n . Thus height should b. allowed f o r when energy budgets a r e s e t and i n f i l t r a t i o n should not.
Th. e f f e c t Of hour8 of occupancy on t h e energy consumption of t h e build- ing i 8 o f s i g n i f i c a n c e only when comparing t h e measured energy consumption of th* building i n use with e i t h e r a c a l c u l a t e d f i g u r e o r t h e measured conamption f o r a d i f f e r a n t period (when t h e use may have been d i f f e r e n t ) .
per year of occupancy have-considerable effect on energy consumption. There are, however, many factors such as different profiles of daily use and different periods of use in s w m e r and winter that have not been studied. Thus the results can only give an indication of the probable effect of changes in period of use.
It is not possible to generalize with respect to the reduction in energy consllmption that can be achieved in existing buildings, but improvements over present levels have been shown to be possible without incurring major costs for building revisions. It is possible that a consumption of
2
1200 MJ/(m .year) could reasonably be attained by office buildings of size and shapa similar to those studied, used for the same period of time as the &el building, and subjected to climatic conditions similar to those of -ton.
References
1. L. Jones, The Analyst as a Factor in the Prediction of Energy Conoumption. To be presented, Second International CIB Symposium on Energy Conservation in the Built Environment, 28 May
-
1 June 1979.2. Measures for Energy Coneenration in New Buildings 1978, Associate Cormittee on the National Building Code, National Research Council of Curart., Ottawa, 1978.
8non WcW. Vanainp Ihrlcahy Reilly A~o&etes. Dublin, Ireland: BuilQing operation offers masaive opportunities for conservation. Is W67 a c t i v e
in
this we.?Chsrleo Ficner. Dspartnmnt of Enerm, Mines and Resources. Ottawa, Canada: The identified attainable energy consumption is over three times as high an that Of other buildings which have been C ~ n s t ~ c t e d at no increase in c a p i t r l coat. Thie points out a clear intideqwcy of the approach for dewloping realistic. economicalLy justified, budgets for new office building..
Rourassa and Lattat
Tha author. are in full agreement with
nr.
nulcahy that there are great opportunities for reducing the energy conamption of existing buildinqs and, as tha etudy h u shown, that great savinqs can be achieved without the aqmnditurs of large s u m of mney. Purthermore, as it will be many years yet before new energy efficient buildings will replace a significant numbar of existing buildings, it is desirable that this should beemphasized just as much as the minimum energy consumption that can be obtained with new construction.
The study was therefore designed to do two things: on the one hand, to explore the significance of factors such as climte and size on a
building's need for energy so that meaningful comparisons can be made between different buildings and appropriate allowances made for these
factors; on the other hand, to study'the reduced energy consumption that might reasonably ba attained by existing buildings. It was as one outcome of this second aspect of the study that the figure of 1200 MJ/(m2.year) was given as a gener~lized.tarqet figure. It is not intended as an energy bUdget for new buildings. Of the four existing buildings studied the existinq energy cons%mtptio~ and the c-uted reduced consunptione are as follan t
Building Energy Consumption r Reduction
~ ~ / ( m 2 - ~ e a r )
Existing Reduced
A 880 880 0
Building A wan already an efficient building and there was nothing more thAt could reasonably be dona. Reductions of about 60r from the existing COnsumptions of tha other three buildings were shown to be possible according to theoretical analysis. It is not known whether such nductions can be achieved in practice. Six buildings that,had
conmarvation measures appliad to them by another authority achieved actual rductions of between 1.2% and 50.21, with an average of 23%.
With reSpeCt to nav buildings, further work carried out by the study t a m follouing subairsion of the draft paper to CIB consolidated all of
the st* simulations into the following over-all formula from vhich an energy budget for an office building in Canada can be calculated.
Y
-
0.0709X1+
0.154X2+
652X3+
1090X4+
2.675X5+
58.24X6-
1127.6 *re Y-
e s t a t e 8 over-all energy consrnption in megajoules per squarem t r e per year
X1
-
heating Degree Days below 10°C X2 = cooling Degree Days above 12.8OCX,
-
infiltration in litres per second per square metre of floor areaX4
-
E/P Ratio (adjusted) X5-
days of uso per year X6-
hours of use par dayThis formula assumen that the factors studied are independent variables; interaction between them has not been studied. Applying it to a range of buildings
in
various locations in Canada, operating for 10 hours per day for 252 days per year (5 days per week leas holidays) gives energy budgets ranging from 620 ~ ~ / ( m ~ . ~ e a r ) for a large low building in Vancouver to 1150 ~ / ( m ~ . ~ e a r ) for a small building in Winnipeg. The poor envalope-to- floor ratio affects the small building adversely.Thoro v a l w s m y be related to the known energy consumptions of 159 offico building. at various locations across Canada. These ranged from a high v a l w of 5390 ~ / ( r n ~ - ~ e a r ) to a low of 580 ~ / ( r n ~ - ~ e a r ) , with an avorag. of 1980 ~ / ( r n ~ . ~ e a r )
.
Am Hr. Ficner sayr, there h a m been several claims that same buildings haw k.n designed to use no more than 400 HJ/(m2.year), but it is not yet
eloar that much a law value has been achieved in actual operation, nor is it 010rt that these lar values have been achieved without increasd cost.
Such buildings are usually very big (over 100,000 r 2 in floor area), have
8- f o m of heat rocowry system, and are often heavy users of electrical
Onotgy. Thor. is nothing wrong with big buildings from the standpoint of m e r w conridrrations, but they are as yet the exception rather than the
nOm. Heat recovery systems should, of course, be encouraged. The &p.ndmnw upon electrical energy is, on the other hand, open to debate. wfticularly vhon one considers the quantity of fossil fuel that may be
n o a d d to generate it.
Tho Us. of tho .bow formula to determine an energy budget for a 20-atoroy building of 93,000 m2 floor area in Toronto gives a value of
700 HJ/(mZ.year). That a building in the Toronto area of roughly the same size, using heat recovery and similar energy conserving techniques, is currently operating at 690 ~ / ( m ~ - ~ e a r ) must surely be a remarkable coincidence in view of all the possible reasons for variation. It gives dame confidence, hwever, that the approach used in this study does lead to realistic results.
