EFEKTÍVNOSŤ VYNALOŽENÝCH FINANČNÝCH PROSTRIEDKOV PRI DODATOČNOM ZATEPLENÍ BUDOV THE EFFECTIVENESS OF GIVEN FINANCIAL RESOURCES FOR THE ADDITIONAL THERMAL INSULATION OF BUILDINGS EFEKTÍVNOSŤ VYNALOŽENÝCH FINANČNÝCH PROSTRIEDKOV PRI DODATOČNOM ZATEPLENÍ BUDOV THE EFFECTIVENESS OF GIVEN FINANCIAL RESOURCES FOR THE ADDITIONAL THERMAL INSULATION OF BUILDINGS

33 K O M U N I K Á C I E / C O M M U N I C A T I O N S 2 / 9 9 Súčasný rozvoj materiálovej základne a technológií umožňuje rôznym spôsobom zlepšiť tepelnoizolačné vlastnosti existujúcich obalových konštrukcií budov. Jednotlivé spôsoby sa medzi sebou okrem iného líšia i životnosťou. Príspevok sa zaoberá hodnotením dodatočného zateplenia z pohľadu návratnosti vynaložených finančných nákladov vo vzťahu k jeho životnosti. Uvádzajú sa tu základné výpočtové vzťahy a ich grafické znázornenie slúžiace pre posúdenie ekonomickej efektívnosti.


Introduction
Securing thermal ratios suitable for the workplace or for technological processes is an important condition for the operation and derived value of a building . Current energy costs are an incentive to reduce energy consumption in the heating of buildings. The augmentation of heat-insulating properties of existing packing covering of these buildings can help to fulfil this requirement.
The augmentations of heat-insulating properties of these constructions have technical and economical limitations .This contribution aims at improving and realizing cost effective heatinsulating properties of packing construction in a building.

The borders of economical effectiveness
The basic heat-insulating property of circumferential constructions is their thermal resistance. The size of thermal resistance determines heat thermal transmittance k (W. m -2 .K -1 ) which influences the heat-insulating properties of circumferential construction in the calculation of thermal loses of the building (according to STN 060210). Therefore, a higher thermal resistance of circumferential constructions has a direct influence on the decrease of the energy consumption of the heating.
Vzťah (1) môžeme zjednodušiť do tvaru: Analyzujme teraz vzťah životnosti dodatočnej úpravy steny zvýšením jej tepelnoizolačnej schopnosti a diskontnej miery investora. making of the heating system and the expenses for heating decrease. We regard wall constructions (at which the sum of noticed expenses is smallest) as the best solution for this economical problem.
We usually use the method of current value (at the course according to STN 730549) for all expenses (the expenses for the making of the building and expenses connected with the construction service and building heating) applied at 1 m 2 of exterior wall construction and calculated to one instant in time (usually the time when the building is finished).
Working expenses which consist of periodical annual outlay are calculated at current value and together with the investment of the initial cost make the base of thermal-economical appreciation.
Generally, we can expect that those circumferential walls which don't take the expenses for their making and the expenses for the heating into account are thermal-economical. This appreciation is regarded as crucial in the case when thermal resistance of the wall is higher than the required smallest allowed thermal resistance R (m 2 .K. W -1 ) determined by the normative rule for climatic area in which the building is located.
Suppose , that we give financial resources K (Sk) for the making of additional thermal insulation . The savings at thermal energy given through heating system into the building correspond with these financial expenses. These savings represent an annual decrease of heating expenses of about ⌬m (Sk). Additional correction of the constructions -warming will be afterwards economical and thermal-energetic effective if in the time of service life of this construction, corrections have reached the savings ⌬m (Sk) equal to or higher than the given financial resources for its making. We can express this connection as follows: in which i -is average rate of capital expense for the investment (discount rate of investor %) n -is the rate of the years in which we gain annual decrease of the expenses about ⌬m (Sk) We can simplify the relation (1) to the form : And now let's analyze the relation of service life of additional wall repair by the augmentation of its heat-insulating ability and discount rate of the investor.
Hodnota koeficientu h podľa vzťahu (3) je potom 12,3. Po dosadení do vzťahu (2) získame nasledovnú podmienku: na dodatočné zateplenie uvažovanej budovy je výhodné každé technické, The source for financing the investment is an important item because discount rate (of the investor ) goes on it. Because it is not the same whether the investor finances the investment from their own financial sources or he does the work by dint of financial resources gained from the credit or special endowments.
Suppose the service life of building objects is 77 years from the time when their were built. The service life of the heating system is approximately half in comparison to the service life of the building. It means that after 38 years it is necessary to count on financial expenses for the reconstruction of heating system. It can be seen from experience that the service life of making the additional repairs for the improvement of heat-insulating properties of circumferential construction can be in the maximum range up to 77 years. We determine from the graphic illustration the relation (3) which is on Fig. 1. marginal values of economical effectiveness of given financial resources for the decrease of thermal losses of heated building in connection with concrete discount rate of the investor i (%) and the rate of the years during which we exploit this additional correction.
The increase of the prices of thermal energy in a selected period is not taken into account in the graphical illustration on    (2) we achieve the following condition: every technical, technical -working rate which doesn't cost more than 12.3 multiple by it enabled annual savings ⌬m (Sk) at the heating is effective at additional thermal insulation of the selected building.
If we debate theoretically limitless service life of additional thermal insulation it means that we gain (in time limitless stretch the saving ⌬m (Sk) annually then the coefficient h (in the equation (3)) will come closer to the value h Х 1/ i. We gain the value h = 12.5 with the offered rate i = 8 %. This value is different only a little bit from the value which we gain for 50 years service life.
Current conditions in the realm of energy supply can be characterized by the condition of market liberalization. The energy contractor usually acts (in this liberalized surrounding) at the changing needs of the customers by price structuring. The price structure in the first case corresponds to the interests and the needs of the energetic system and in the second case to the demands of the customers. The goal of this price politics is to act efficiently in the following realms: G To influence the demand and supply. To take (at the price system) the interest of the state as also the interest of the producer and distributor of the energy (or the consumer) into account. G To control the demand for the energy because any endowments into the energy prices lead to wrong habits of the users at the energy consumption. G The energy prices must reflect the expenses of the production, distribution and proper profit. The expenses covered by energetic companies (with proper profit) will secure also the resources for the state budget. G The energy prices must secure the ability of mutual competition of particular fuels among themselves everywhere where it is possible. Particularly in the case of electricity, natural gas and the heat for the building heating.
Every country in its own politics already has a strategy for the achievement of noticed goals. We consider the first stage valid till the year 2000 as the so-called "balance of price levels". It is the balance of low level of loss prices to the level of profit prices. In the second stage till the year 2002 a new rate system will be made. The third stage after the year 2003 will be the time of the enforcement of standard price regulation.
The EU council accepted in the realm of price development in energy the guideline no. 90/377/EEC about the process at the improvement of the transparency of the prices: of gas and electricity charged to the final consumer. Its measure will be valid in the states of the membership of EU from February 1999. We are going to write here (for the consumption) the energy prices from the year 1996 in different countries Fig. 2. The price of electric energy in Slovakia according to this belongs among the lowest of the rated countries.
Hence, we suppose its increase on the prices valid in EU. We presume that the price increase of electric energy in the time horizon till the year 2002 as follows: the year 1999 about + 33 %, about + 4 %. The determination of energy prices (which will go on mutual changeability of particular fuels as electricity, natural gas and the heat produced by central sources for the building heating) is supposed.
It can be seen from the noticed reasons that the time course of annual energetic savings ⌬m will not, in these conditions, be constant because the prices for the energy increase annually. Originally considered savings ⌬m will then increase about ⌬m (1 + r x ), where r x is the coefficient of price increase of the energy which can be different every year. This fact (is its time sequence) is noticed in chart no. 1.

Time expression of inconstant annual savings from
Tab. 1. the reasons of expenses reduction for the heating. cientom nárastu r (%). Dodatočné zateplenie bude potom energeticky efektívne, keď výška financií K (Sk) vynaložených na jeho vyhotovenie bude nižšia prípadne rovná výške dosiahnutých úspor podľa [5] nasledovne: čo možno upraviť do tvaru: Vo vzťahu (6) We suppose for simplification that the energy prices will increase in every year of the thermal heating exploitation by the same increase coefficient r (%). The additional thermal insulation will be energetically efficient when the size of finances K (Sk) given for its making will be lower or equal to the size of achieved savings according to [5]as follows: this is possible to rewrite into the form: in which d ϭ The mutual connections (among the average measure of financial expenses at additional thermal insulation, the time of benefit exploitation from additional thermal insulation and the coefficient of annual increase of the energy price for the heating) are written in equation (6). Suppose, the average annual increase of energy price in the same way as our previous reflection for the years 1999-2002 about r =15 % and the average measure of capital expenses of the investor i = 8 %. If we take (at these conditions) the benefit from additional thermal insulation only in the years 2000, 2001 and 2002 then every investment (for the improvement of heat insulation) will be advantageous (for the investor) which does not cost more than 3.4 multiple by it caused annual reduction of the expenses for the heating. Túto hodnotu možno od-čítať z grafického znázornenia vzťahu (6) pre uvažované podmienky. Ak budeme brať úžitok z vynaloženej investície na zateplenie pri nezmenených a konštantných hodnotách r (%), i (%) počas ľubovoľného dlh-šieho obdobia, môžeme z obr. č. 3. odčítať podmienku pre vhodnú výšku investície na dodatočné zateplenie uvažovanej vykurovanej budovy.

Literatúra
Recenzenti: J. Zajac, J. Svrček This value can be seen from the graphical illustration of equation (6) for the mentioned conditions. If we take the benefit from given investment for the thermal insulation at the same and constant values r (%), i (%) during any longer time, we can see from Fig. 3. the condition for suitable investment size for additional thermal insulation of that heating building.

Conclusion
If we take the increase of the prices of consumed energy for the heating of the building into account, its consequence will be the requirement for increased financial expenses for the improvement of heat insulation of this building. If we use the following calculation simplification: G The price for the consumed energy for the building heating will be in time constant or will change negligible r = 0%. G We will presume unlimited life service of additional thermal insulation during the building's existence.
We can say on the strength of this one economic condition that every improvement of heat insulating properties for which we must not give more financial resources than 1/i -multiple by it enabled annual savings for the heating is efficient.