Ž .Energy and Buildings 31 2000 189–193www.elsevier.comrlocaterenbuild

Indices for estimation of energy conservation in space heating

Vladimir Stepanov a,), Natalia Starikova a, Tatiana Stepanova b

a Irkutsk Technical UniÕersity, 83 LermontoÕ Street, Irkutsk, 664074 Russian Federationb Siberian Energy Institute, Russian Academy of Sciences, 130 LermontoÕ Street, Irkutsk, 664033 Russian Federation

Received 18 April 1998; accepted 8 March 1999

Abstract

The paper presents a method for estimating the energy use efficiency and energy reserve conservation in space heating. The concept oftheoretical energy conservation potential is introduced. Estimate of the value of a minimum required heat consumption, which takes intoaccount climatic conditions and sanitary-hygienic standards, is used. Calculations illustrating the elaborated methods have been done forIrkutsk as an example. q 2000 Elsevier Science S.A. All rights reserved.

Keywords: Energy conservation; Space heating; Heat consumption

1. Introduction

Energy conservation in space heating is a critical energyproblem in Russia. By the statistical data about 40% offuel is consumed for space heating and ventilation. Morethan half of it is used for heating of dwelling houses. Sucha situation is due to severe climatic conditions in themajority of regions of the country. The heating period, as arule, lasts 7–8 months, and even the whole year in thenorthern regions, such as Yakutia and Magadan region.

Besides, energy for heating is consumed very ineffec-tively. Experts consider that in heat supply and ventilationsystems the overconsumption of energy is 25–30% of thenormative values because of their unadjustment, buildingimperfections and other reasons.

For analyses of the energy consumption, the energy useeffectiveness index is defined as the consumption of heatŽ . 2fuel for heating of 1 m of the building area, i.e., thevalue of energy input which is known as a specific con-sumption. Usually the estimation procedure of this factor ismaking possible to compare energy consumption for thispurpose in the country with the relating factors in othercountries which have a similar climatic conditions. Thedata from Scandinavian countries are taken most often assuch a reference standard. However, these conditions, as arule, are not entirely alike. Many Russian regions wherethere are many large and small towns and settlements and

) Corresponding author. Tel.: q7-3952-464959; Fax: q7-3952-462796;E-mail: root@isem.seirk.ru

dozens million of people live, have no any analogues.Besides, the difficulty of such a comparison with foreigncountries lies in differences not only in climate but alsobuilding standards, requirements to microclimate insideaccommodations, etc.

It is well known that the better the heat insulation of abuilding, the less energy is required for its heating, andvice versa. A compromise is determined on the base of theoptimization analysis. The result depends on cost of fueland energy, building materials, labour, their ratio, produc-tion of new materials and new types and constructions ofexternal building surfaces.

The above mentioned indicates the impossibility toestimate energy use effectiveness for space heating bycomparison, since all the parameters are different: climaticcharacteristics, building standards, requirements for insidemicroclimate accomodations., etc. Therefore, a system ofobjective indices should be elaborated for this purpose,taking into account high energy consumption of this sphereand necessity to reduce it.

2. Method applied

Since the 80s, the thermal protection level for buildingshas considerably been improved by application of newinsulating materials, optimal architecture and layouts. As isknown, glass has the lowest coefficient of heat-transferresistance among the elements of external surfaces. There-fore, at present an attempt is made to decrease an area of

0378-7788r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved.Ž .PII: S0378-7788 99 00013-4

( )V. StepanoÕ et al.rEnergy and Buildings 31 2000 189–193190

window openings. In the 60s the glazing ratio reached75%, in the recent decades there is a tendency of its reduceto 20–25%. A new Russian standard recommends that thevalue should not be higher than 18%.

Thus, the heat insulation standards, adopted in a countryfor residential and public buildings, determine some nor-mative value of energy consumption for their heating in

Ž .the given climatic zone Q . A great number experimentsn

testify that actual energy consumption considerably ex-ceeds the normative one. From the results of full-scaletests the actual air permeability of windows in residentialbuildings is 3–7 times higher than asked in the nationalstandards. Besides, the butt joints of panels used forconstruction have, as a rule, resistance for heat transfer R0

on the average by 20% lower than it must be according togiven in the standard.

Therefore, the actual heat consumption Q exceeds to aac

considerable extent the normative values because of a lowquality of construction and inadequacy to the regulationsfor maintenance of buildings and operation of heat supplysystems and equipment. Different measures directed atelimination of these shortcomings lead to some reductionof the actual consumption.

Thus, both the normative and actual energy consump-tions on space heating are reduced in due course byintroduction of all possible energy conservation measures.The curves of their changes are shown in Fig. 1a. Thetheoretical limit for reduction of both the normative andactual energy consumptions on heating is some value ofthe minimum necessary energy consumption for the con-sidered climatic zone—Q . It corresponds to somemin

idealridealized process of heating and can be used as thereference level for estimation of energy conservation in thecountry, in this sphere. The principles for formation of theidealized analogues and determination of the minimumnecessary energy consumption for space heating are the

w xfollowing 1 :1. The process aims to provide minimum necessary condi-

tions for life and work of people.2. These conditions depend on the sanitary-hygienic stan-

Ž .dards norms by their lower limit.3. The minimum heat demands should not depend on

technical characteristics of buildings, their structure,Žarchitectural appearance and laying out building mate-

rials and types of external surfaces, orientation in space,.etc. .

4. The minimum heat consumption for space heatingshould taken into account climatic conditions in differ-ent regions and populated points.The heat energy required for space heating is deter-

mined essentially by its consumption to compensate heatlosses through an envelope of buildings. Theoretically, theheat consumption for heating should be equal to zero with

Ž .very perfect heat insulation of a building R ™` and the0

absolute absence of air infiltration through untightness ofbuilding envelope.

Fig. 1. Graphic notion of the concepts of theoretical potential and reserveŽ .of energy conservation in space heating a during functioning under

Ž .building standard conditions; b when the building standard conditionsare changed.

However, such extreme idealization does not reflect thepurpose of a building, in which people have to live andwork, as they cannot be in a building without fresh airexchange. Hence, the assumption on the absolute absenceof air infiltration in an idealized analogue is not right.

Besides, an idealization of the space heating process isuseless, when heat loads of a building are equal to zero.There are hygienic-indoor air quality standards which limitthe carbon dioxide content in the air. During heatingperiods the fresh air supplied into residential or publicbuildings should be obviously warmed up. The minimumheat consumption for this purpose is determined, on onehand, by the temperature inside the building, and on theother hand, by the value of an outdoor temperature. Thefirst is established by sanitary standards depending on thefunction of a building. The second depends on the climaticzone, where a building is located. If the annual outdoor

( )V. StepanoÕ et al.rEnergy and Buildings 31 2000 189–193 191

Ž .temperature curve t t is known, the minimum heatout

consumption on heating of such an idealized residential orpublic building is determined by expression:

tendU rQ s 1yg c V t y t dt , 1Ž .Ž .Ž . Hmin reg a fa in outt beg

where V U —the normative volume of fresh air, m3rh; t ,fa beg

t —the time of beginning and end of the heating period,end

h; g —a heat regeneration coefficient, i.e., a share ofreg

removed air heat, which is extracted by heat recovery3 rinstallations; c —the specific heat capacity, Whrm 8C; ta in

Ž .—the rated normative air temperature inside a building,8C; t —the outdoor temperature, 8C.out

If the average outdoor temperatures at some time inter-Ž .vals are known for example, the average monthly ones ,

the minimum heat consumption can be calculated by theexpression:

nU rQ s 1yg c V t y t Dt , 2Ž .Ž .Ž . Ýmin reg a fa in out ii

is1

where n—the number of time intervals; Dt —the durationi

of interval i, h.Ž . Ž .As one can see from expressions 1 and 2 , there are

possibilities for heat regeneration of the removed air heat.Based on the Russian conditions, introduction of the coef-ficient g as though increases the process idealization ex-tent, because air heat of residential buildings has not beenrecovered for the present. However, in many countries thesituation is quite different.

Ž . Ž .Thus, using expressions 1 and 2 , one can calculatethe minimum yearly heat consumption for heating andventilation of residential buildings per person dependingon the sanitary standards and climatic conditions only.Besides, the minimum exergy consumption for space heat-ing can be estimated by multiplying the energy consump-tion by the coefficient of heat capacity for work

w s1yT rT , 3Ž .q 0

where T —the air temperature inside accommodations, K;0

T—the heat carrier temperature, K.w xAccording to the elaborated method 2 , suitable for any

energy consumption sphere, the difference between Qac

and Q in year t is the theoretical energy conserÕationminŽpotential in space heating in the current year—P Fig.t

.1a :

P sQ yQ . 4Ž .t ac mint

The total energy conserÕation reserÕe owing to imple-Ž .mentation of a certain list of measures during years t y t1 2

is the difference between actual consumption in years t1

and t :2

RES sQ yQ 5Ž .1 – 2 ac ac1 2

If the standards on heat insulation of buildings areobserved completely, the energy conservation measuresshould be looked for outside this sphere, for example,

installation of devices for the ambient temperature controlŽ .inside houses or improvement of the efficiencies ofheating appliances, i.e., in the interval from Q to Q .ac s

Further increase of heat consumption for space heatingcan be achieved only by improving the heat-protection

Ž .characteristics of buildings Fig. 1b . As a rule, introduc-tion of new standards is caused by a large number ofeconomic indices and, in the first place, rise of energyresources prices. As a result, Q and Q for newlys ac

constructed buildings will be lower than in the previousperiod. However, in this case the efforts are also requiredto lower heat consumption.

Reconstruction of existent buildings can be made, fortheir heat protection characteristics to be comparable to the

Ž .new standards the dashed line in Fig. 1b .Based on the principles for elaboration of an idealized

analogue for space heating, Q is measured in GJ permin

person for the heating period. The normative and actualenergy consumptions are determined, as a rule, in GJrm2

of the building area. Therefore, to compare them with theŽ .minimum necessary theoretical consumption, such an

indicator as housing provision in the region or locality—F,m2rperson should be used. Thus,

Q sq F , 6Ž .ac ac

where q —the specific actual heat consumption on heat-ac

ing of 1 m2 of the overall area during the heating period,GJrm2.

Inasmuch as the energy conservation reserve is esti-mated for some interval D t, when the planned measureswill be introduced, the indicator F can also change duringthis period. Hence, the coefficient asF qF shouldt tqD t

be applied to reduce the variants to be compared to theequal provision with housing.

For practical application of the method the minimumnecessary heat consumption on space heating and hotwater supply for all regions and localities of Russia, forwhich the climatological characteristics are available, arecalculated. Table 1 presents these indicators for sometowns as an example.

Table 1Ž .Minimum necessary theoretical annual energy consumption for space

heating for some towns in Russia per person

Town GJ

Oymjakon 5.698Urengoy 4.205Salehard 3.956Irkutsk 3.046Novosibirsk 2.915Syktyvkar 2.758Vladivostok 2.218Moscow 2.216St. Petersburg 2.140Kislovodsk 1.502Sochi 0.623

( )V. StepanoÕ et al.rEnergy and Buildings 31 2000 189–193192

The existence of minimum necessary energy consump-tion enables the objective index of effectiveness, similar tothe efficiency in thermodynamics to be determined. In ourcase Q can substitute the useful energy in numerator.min

The efficiency calculated in this way is relative. Moreover,the minimum necessary consumption can be correlatedwith both the normative and the actual heat consumption.In the first case, the normative efficiency which corre-sponds to the accepted building standards is determined. Inthe second case it is the actual efficiency.

In conformity with the above discussed the energyefficiencies of space heating are:

h s sQ rQ ; h ac sQ rQ 7Ž .en min s en min ac

The energy efficiencies can be estimated similarly:

h s sE rE ; h ac sE rE 8Ž .ex min s ex min ac

Here E , E and E —the exergy values in heat con-min S ac

sumption, the minimum necessary, normative and actualones, respectively.

It should be noted that the numerical value of efficien-cies depends on the chosen idealized analogue. Therefore,to use these indices and to put them in practice of researchand design works, it is necessary to enlist many experts fordiscussion of the problem to approve the generally ac-knowledged standard regulations on parameters of theidealized analogue. It is possible to come to an agreementabout the common limiting values of thermal resistancesfor elements of external surfaces for the ‘idealized build-ing’ for all regions of the country. These resistances shouldapparently be larger than the required heat transfer resis-tance R r , but at the same time not obligatorily equal to the0

infinity, as it is taken by us. Introduction into the expres-sion for Q of the regeneration coefficient of air heatmin

removed from residential buildings and estimation of itsvalue should also be discussed.

In such a case the minimum necessary energyrexergyconsumption will be a very convenient normative index

depending on only climatic conditions and sanitary stan-dards. The effect attained due to realization of the mostsignificant energy conservation measures can be estimatedby increasing the energy and exergy efficiencies. Hence,there is a possibility to connect the theoretical potentialand reserve of energy conservation with the efficiency ofspace heating.

3. Calculations

To illustrate usefulness of the suggested method thecalculations have been done for the multi-storey residentialbuilding with centralized heat supply in Irkutsk. The nor-mative heat consumption on space heating for this type ofbuildings on the average is 1.25 GJrm2 or about 18.75

w xGJrperson by preceding building standard 3 . The actualheat consumption is estimated at 1.62 GJrm2 or 24.30GJrperson. Using these values and the minimum neces-sary heat consumption for the Irkutsk climatic conditions,we determined the theoretical potential and the reserve ofenergy conservation and also the normative and actual

Ž .energy efficiency in heating Table 2 . The normative heatw xconsumption for a new standard 4 for heat insulation of

external surfaces is shown for comparison. Whereas theprevious standards had to ensure the normative energyefficiency h s s16.21%, the new ones have to increase iten

to 21.75%.Besides, we tried to estimate the potential and reserve

of energy conservation by putting two measures into prac-tice whose realization could give the greatest effect.

It is known that glass has the lowest heat transferresistance among elements of external surfaces. Therefore,at present an attempt is made to decrease the area of lightopenings, as far as requirements to the natural illuminationlevel inside buildings allow. Besides, transition to three-layer and even four-layer glazing of windows is performedin the countries with severe climatic conditions.

Table 2Ž .Theoretical potential and reserve of energy conservation in space heating in Irkutsk multi-storey building, centralized heat supply , GJrperson per year

Index Heat consumption Theoretical potential of Reserve of energy h , %en

on space heating, Q energy conservation, P conservation, RESt

Ž .1 Minimum necessary consumption 3.04Ž .2 Current stateactual consumption 24.30 21.26 – 12.50

Žnormative consumption by building 18.75 15.71 – 16.21.standard of the preceding period

Žnormative consumption by new 13.98 10.94 – 21.75.building standard

Ž .3 Energy conservation measurestransition to three-layer one from 20.25 17.21 4.05 15.01two-layer glazingimprovement of thermal resistance 16.16 13.12 8.14 18.81of external surfaces of buildingscombined realization of both measures 12.11 9.07 12.19 25.11

( )V. StepanoÕ et al.rEnergy and Buildings 31 2000 189–193 193

In Irkutsk, as in most of regions of Russia, windowswith two-layer glazing and separate sashes are widespread.One of the main requirements to windows as elements ofexternal surfaces is their resistance to air permeability.Conversion of multi-storey buildings to three-layer glazingin wooden or plastic separately-doubled sashes ensuresreduction of heat losses not only by increasing reduced

Ž redresistance to heat transfer of windows R increases from0Ž 2 . .0.39 to 0.55 m 8C rW ,but also by considerable reduc-

tion of air infiltration through them.Total reduction of the annual heat consumption per

dweller of such buildings is about 17% of the existentlevel which leads to increase in the energy efficiency ofthe heating system of multi-storey buildings from 12.50%

Ž .to 15.01% Table 2 .Ž .The study shows that the bulk of heat to 45–50% is

lost through walls. Nevertheless, the large-scale construc-tion of housing is realized using one-layer concrete panelseven in Siberia. Sharp increase of thermotechnical charac-teristics of walls can be attained by multi-layer construc-tions with an effective warmth-keeping lagging. In thiscase the actual resistance to heat transfer is 3.0–3.5 timeshigher compared with the existing standards.

Increase of the required resistance to heat transfer ofexternal surfaces of multi-storey residential buildings in

Ž red Ž 2 . w x.Irkutsk to a new standard R s3.8 m 8C rW 4 could0

result in heat saving of about 34% of the total existent heatconsumption. The energy efficiency of heating increases in

Ž .this case to h s18.81% Table 2 . The energy conserva-en

tion reserve for combined realization of the two measuresis presented in Table 2. The estimates show that the heat

saving in heating by introduction of both measures couldexceed 6.5 PJryear or amount to about 270,000 tceryearof primary energy resources.

4. Conclusion

The energy conservation potential introduced by us isthe theoretic value that is technically unattainable. But itsvalue is to help in qualitative analysis of the situation. Thecloser the energy conservation reserve to its potential, themore complicated and expensive will be the improvementof space heating effectiveness. The theoretical potentialincludes all possible ways of saving: change of buildingstandards, improvement of quality of construction andmaintenance, increase of the efficiency of heating appli-ances, etc.

In the present research we did not touch the issue of theeconomic efficiency of energy conservation measures. It isa separate important problem.

References

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Ž .logy and geophysics in Russian , Gosstroy, Moskva, 1985.w x4 Change No3 in Sanytary standards and regulations 11-3-79 ‘‘Building

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