Publisher’s version / Version de l'éditeur:
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
Proceedings of the 2nd International CIB Symposium on Energy Conservation in
the Built Environment, pp. 313-321, 1979
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. https://nrc-publications.canada.ca/eng/copyright
NRC Publications Archive Record / Notice des Archives des publications du CNRC :
https://nrc-publications.canada.ca/eng/view/object/?id=b46ce1b9-165f-4b2f-b878-dea24dfea7d3
https://publications-cnrc.canada.ca/fra/voir/objet/?id=b46ce1b9-165f-4b2f-b878-dea24dfea7d3
NRC Publications Archive
Archives des publications du CNRC
This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
The analyst as a factor in the prediction of energy consumption
Ser
I
~ 2 1 d
National R-arch
Consell national
no.
920
I
$
Council Canada
de recherches Canada
THE
ANALYST AS
A FACTOR IN THE PREDICTION
OF
ENERGY CONSUMPTION
by L
Jones
Re~tintcd, with permission, from
-
Proceedings, Second International
CIB
Symposium on
Energy Conservation in the Built Environment
Session
4,
Copenhagen 1979
p.
313
-
321
ANALYZED
DBR Paper No. 920
DivLion of Building Research
This publication is 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. It shouldnot be reproduced in whole o r in p a r t without p e r m i s s i o n of the original publisher. The Di- vision would be glad to b e of a s e i e t a n c e i n obtaining s u c h permission.
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 to the R e c e i v e r G e n e r a l of Canada, c r e d i t NRC) to t h e National R e s e a r c h Council of Canada, Ottawa. K1A OR6. Stamps a r e not acceptable.
A l i s t of a l l publications of the Division i s available and
m a y be obtained f r o m the Publications Section, Division of Building Research. National R e s e a r c h Council of Canada, Ottawa. M A OR
6.
---3---,---&---
, Th. a n a l y s t a s a f a c t o r i n t h e p r d i c t i a n o f energy c o n s m p t i o n
by L. Jones, Research O f f i c e r , ~ i v i s i o n o f Building Research, National Research Council o f Canada, Ottawa KlA OR6, danada.
Smmary. With t h e g o a l of producing a workable, performance-type b u i l d i n g u m t q y c o n s a r v a t i o n code, t h o D i v i s i o n o f Building Research, National R a n a r c h Council o f Canada, is t r y i n g to d e v i s e a s u i t h b l e , p r a c t i c a b l e m a n s of v e r i f y i n g c m p l i a n c o w i t h a n energy budget. l W 0 methods a r e under consideration^ measuring t h e annual f u e l cansuf8ption o f a b u i l d i n g i n u s e
ar a n w r g y w l y s i a . I n o r d o r t o cluck the s u i t a b i l i t y o f ccmpliance by anorgy a n a l y s i s , 22 c o n m l t u r t s were coaaiss&onsd to c a r r y o u t energy u u l y - 8 o f a h y p o t h e t i c a l Ust b u i l d i n g . The r e s u l t s show l a r g e ~ r i a t i o n a i n p r u l i c t e d energy consumption.
-III-Ic.L---I-IIC---
L ' w l y s t a : Un f a c t e u r dans l a e r g d i c t i o n d e l a consomaation d'8nergie
-II--
-Ram-6. Dam l e b u t de produire un code dl€conomie d l € n e r g i e p r a t i q u e , baa6 s u e 3o rendamsnt, l a Division d e s recherches s u r l e bstiment du C o n m i l n a t i o n a l do recharches envisage de m e t t r e a u p o i n t des m y e n s a d ( p w t s e t e x i c u t a b l e s de v & r i f i e r l a conformit6 avec un budget d'gnergie.
OIur m6ehoder s o n t consid&r€es: mesurer l a consommation de combustible
urnumllm d'un b6timent en usage ou une analyee Snergstique. Afin de c m t r 8 l e e l a conformit6 de l ' a n a l y s e d e l a consommation d 'gnergie, 22 c m r u l t a n t s on 4 t 6 chergds d ' e f f e c t u e r d e s a n a l y s e s de l a consommation d'6nergie d'un batiment d ' c s s a i hypothbtique. Lee r € s u l t a t o b o n t r s r e n t de l r a a d a & c a r t s de p r 6 v i s i m de
l o
consomnation d ' i n e r g i e .---13L----.r---rr-.----It---1--11-I-r---
The a n a l y s t a s a f a c t o r i n the prediction of energy consmption
-1---------------1-------------------------------------=-----
-Introduction
The Division of Bliilding Research of t h e National Research Council of
Canada i s c u r r e n t l y dweloping a performance-type energy conservation
standard f o r buildings. The concept of such a standard a s ganerally w d u s t o o d i s t h a t a building of given type and location is a l l o c a t e d annual energy allowance o r energy budget.
Unlike a p r e w r i p t i w standard, such a s Wpurrs f o r E n e r ~ ~ o n a e r m t f o n i n Icw Buildings (1). a performance standard d i c t a t e s t h e energy a l l ~ r ~ l C % not t h e means of achieving it.
Although a r a t i o n a l method to generate budqets (2) has been proposed t h e r e remains the question of compliance; how can the a u t h o r i t y with r e s p o n s i b i l i t y f o r implementing a code (standard) be assured tlnt a progooed building w i l l use no a o r e energy than i t s a l l o t t e d allowance?
Tvo routes a r e generally considered as possible means of ensuring
-1 $am. 1
(a) through t h e apprao.1 of an energy a n a l p i s f o r t h e building, o r
(b) by measuring t h e a n n u l f u e l consumption.
The f i r s t method i s t y p i c a l of e x i s t i n g building code enforc-nt mathods where plans a r e f i r s t checked t o ensure t h a t they meet c u r r e n t 1 . g i s l a t i o n before a building permit is g r a t e d . In s i m i l a r way, i f this
u t h a d of canpliance with a performance enerqy conservation code is .boptad, t h e building developer o r h i s agent would be expected to o f f e r dwwnontary evidence t h a t t h e projmsed building would meet the energy budget. This implies t h a t an acceptable method of p r e d i c t i n g energy We is available. Further. a l l techniques t h a t a r e t o be considered
rn
aooept.bla i n showing cmtpliurce with an energy budget should produce equivalent remulte. Howaver, mmy s t u d i e s such a s th.t c u r i a d o u t in 197l
by Autmated Prccedures for Engineering Consultants Inc. ( 3 ) a d current work with the International Energy Agency have shown that differing techniques of energy prediction, i-e., different computer programs. cannot
ba relied upon to prodcce the same result for a given building. In many
u u o these differences are of such a magnitude that it would be
unrealistic to accept all such calculation procedures as being suitable for judging the projected energy use of a proposed building.
One possible sol.ution to this problem is to certify program as acceptable by rating them against a standard or benchmark program. TkiS
is the method adopted by the State of California. Inherent in such a
method is the assumption that various analysts using the sa6m program will
obtain equivalent results. To establish whether it is reasonable to d e
such an assumption, a projeet was undertaken by the Division of Building
Research to determine the degree of consistency of energy analyses carried out by practicing consulting engineers.
Tuanty-tw consultants, all of whom had recently accessed the neriwther
m r g y Systems Analysis Program, were asked to use^ that program to predict
the energy use of a hypothetical building. A specification for the
building was written based on the building specification used in ehe
International Energ.] Agency's cornpar4 son of computer program* (4)
.
Thecon-t of the specification was changed, however, in an attenpt to *teatn
the user, not the program, and wan written in such a way as to present the conoultu\ts with problems similar to those they w u l d encounter in
practice. In general this was achieved by specifying the physical
chractoristics of the building and the heating, ventilating a ~ ¶ air-
conditionfng systems; all items where engineering judgement or calculation
-8 required were left to the discretion of the analyst.
In an attempt to avoid problems in interpreting the specification and to
mnnurm that the spcification was complete, consultants were first asked
t o compile their input data set and to relate any problems of interpreta-
tion or missing data to DBRlNRC. All thesyenquiries were dealt with on a
d.pto-day basis and the outcome of any discussion was immediately circu-
lated Lo all the cdnsulkants involved in the project. The actual running
of the computer program was not authorized until all these problems had been eliminated.
Calculated annual consumptions
P i w a s 1 and 2 show the annual heating and electricity consumptions for
th. tent building as calculated by the 22 consultants plus an additional
2 0 7 18 C
.
16z
(1
1 4 C 05
1 2*
10 Z 0 U B-
C 4z
=
2 0 1 5 10 15 20 25 A N A L Y S TFigure 1 . Building heating consllmptions a s c a l c u l a t e d by t h e various a n a l y s t s 2 0 r
;
I8 C3 16 Z 0 14-
C 1 2z
3*
10z
0 u 8 > + 6-
u L 4 C:
2 2 LU 0 1 5 10 IS 3 J 25 A N A L Y S TFigure 2. Building e l e c t r i c i t y consumptions a s calculated by the various a n a l y s t s
Clearly consistency of results was not achieved: based on median values (which should not necessarily be construed as the "correct value") there is a range of +lo6 per cent to -46 per cent for heating and f30 per cent for electricity consumption. Of the 25 analyses, 16 did not fall within the 210 per cent of the median heating value; 7 did not fall within +lo per cent of the median electricity consumption.
Inspection of the various analyst's input data identified several probable causes for the large variation in results. These included several errors in the use of the proqram, wide differences in approach, e-g., from a simple one thermal block simulation to a complex multi-zone model, and large nmerical differences in precalculated values such as peak
infiltration rate. The highest peak infiltration rate, for instance. was almost 9 times the lowest.
To quantify the effect of individual differences on the over-all energy prediction, several parametric runs were made by the author based on a reference model and utilizing, with each parametric run, specific input data as used by one or more of the other analysts. The reference model consieted of a single t h e m 1 zone; for the parametric runs only air-side system simulations were made. The reference model results are identified as numbe!r 25 on Figs. 1 and 2. For example, to determine the effect of building weight on the final results, two parametric runs were made substituting the highest and lowest values of heat storage factor assumed by the various analysts (570 and 80 k.J/~~.rn~) in place of the original reference model values. The results of this, together with several other p r m t r i c runs, are qiven in Table I which shows the sensitivity of the program to various input changes for this test building. The results mhould pot be construed as nocessarily applying in general nor predicting actual building psrformance.
Couunonts
If the energy consumption estimates presented in Fig. 1 are typical of
what can be expected from the industry, it would appear unsuitable to use a ~ l y a i s as a rational basis for verifying compliance with an energy code, unless the quality and/or consistency can be significantly improved. The problem is compounded if we consider the use of several prediction methods
komputer programs) which would introduce the possibility of wider or more numerous variations in predicted energy consumptions. It would certainly be unrealistic to accept computer energy analysis as prima facie evidence of a building's energy performance without carrying out some fonn of checking procedure.
The alternative is to verify compliance by rneans of measurement and reporting of energy consumption of the building in use. This method isnot generally favoured although technically it offers the better solution as the measured fuel consumption is a tangible measure not only of the building's potential energy performance, but of the efficiency with which it is operated. Such a route, however, demands that the building
designer be able to predict the actual energy use of a building with sufficient accuracy that the consumption can be brought below the budgat value. Such an analysis necessitates simulating all the vagaries of actual building performance which is far more difficult than an analysis
using a predefined set of operating characteristics. Conclusions
This work has shown that the energy analyst is a significant factor in the prediction of building energy consumption as several analysts using the same energy analysis program will probably not produce similar results.
This paper is a contribution from the Division of Building Research, National Research Council of Canada, and is published with the apprwal of the Director of the Division.
References
1. Measures for Energy Conmervation in New Buildings 1978. Associate Connittee on the National Building Code, National Research Council of Canada. (NRCC NO. 16574.)
2. Jones, L. Energy Budgets for New Construction. To be published in
Enargy and Buildings.
3. Spielvogel, Iavrance G., P.E., Comparison of Energy Analysis Caplputar Programs. ASHRAE Transactions 1977. Vol. 83, Part 2.
4. AyreS, J.M., Standard Test Building Specifications for IEA Colllpati~ln of Building Energy Analysis Computer Programs. Prepared for the United Stataa Energy Research a d Development Administration, 22 July 1977.
5. Reference Manual for the Energy Systems Analysis Series, Departwnt of Public Works, Canada, July 1978.
TABLE I. Results of parametric runs
Percentage Differences froin Reference Model, for Parametric Runs Base Heating Cooling electric 2
Infiltration parametric runs
-
Winum infiltration +28 -2 <1-
Minimum infiltration -6 <1 <1-
Using a constant infiltration ratebased on combined wind and stack action calculated at average annual
outside temperature and wind speed. <1 <1 <1 (Reference model used a 'stack action'
infiltration simulation.) 3 Solar parametric runs
-
Highest solar gain-
Lowest solar gain +14 -18 < 1-
Window blinds up all year (down in -9 +15 <l reference model)-
Window blinds up but solar loadslagged4 (gains appear as instantaneous -11 +8 <1 loado in the reference model)
-
A# above with window blinds down-
h a n m i s s i o n of absorbed solar radiation by opaque parts of envelope is added 5(not considered in reference model). -3 + 3 <1 Lighting parametric runs
-
Highest lighting use -10 +10 +15-
Lowest lighting use +11 -4 -16-
Lighting heat gain lagged4 (gains appear <1 -10 < 1 a5 instantaneous loads in the referencemodel)
-
L o w s t percentage of lightinq gain toreturn air -15% (60% in referencemdel) -7 +14 <1
-
Highest percentage of lighting gain toTABLE I. Results of parametric runs (cont'd)
Percentage Differences from Reference Hodel, for Parametric Runs
.
Base Heating Coolingelectric 2 Heat storage factor6 parametric runs
-
Highest value used-
570 ~J/OC.~' +15 -3 11 (14 used in reference model)-
Lowest value used-
80 k3/'~.m 2 -27 +2 el- - -- - - - - . - -
7
Stored load key parametric runs
-
7-hour pick up for stored loads -12 -1 <1 ( 3 used in reference manual)- -- - -
Receptacle (small power) parametric r&s
-
Highest usage -9 +14 +6-
Lowest usage +3 -3 -4Reating and cooling coil
-
effect of limited capacity 8-
Lowest heating coil capacities -24-
.-
-
Lowest cooling coil capacities - -7 2-
- -- - -
Ventilation rate parametric runs
-
Highest rate-
Lornmt rateComplax multi-zone model
-
27 zone model. transmission of absorbedsolar included, all loads lagged +11% -19% -2% Notea to Table I
-
l ~ l t h o u g h come percentage changes in cooling are large, the over-all effect on t h e total electricity consumption is somewhat less; the chillers only contribute around 6 9 to thc total electricity estimate for this building. 2 ~ a s s olectric includes consumption by fans, lights, elevators and
mimcellaneous equipment.
3 ~ h e program offers an option of infiltration simulationsr for 'stack action' the infiltration is varied with outside ambient temperature.
Notes to Table I (Cont'd)
4
In the program's simplest f o d solar and internal heat qains appear as insta~taneous loads
- options are available to simulate the time lag
effect.he
transmission of absorbed solar radiation by opaque parts of the envelope is normally not considered, i.e., straight air-to-air heat transfer is simulated. A facility to simulate the solar component is available.%eat storage factor = function of the density and specific heat of the structure and furnishing.
'A key indicating the distribution of the pick-up load for stored load. See Ref. 5 for explanation.
%nlimited coil capacity was called for in the specif icatlon
