INFLUENCE OF THERMAL INSULATION AND VENTILATION SYSTEM ON HEAT CONSUMPTION IN A SINGLE-FAMILY HOUSE

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1 INFLUENCE OF THERMAL INSULATION AND VENTILATION SYSTEM ON HEAT CONSUMPTION IN A SINGLE-FAMILY HOUSE Ewa Zarzeka-Raczkowska, Andrzej Raczkowski, Piotr Redosz Państwowa Szkoła Wyższa im Papieża Jana Pawła II w Białej Podlaskiej, Politechnika Lubelska, Collegium Mazovia Innowacyjna Szkoła Wyższa w Siedlcach (POLAND) e.zarzeka-raczkowska@pollub.pl, araczkowski@mazovia.edu.pl, Abstract Ograniczenie zużycia energii cieplnej jest jednym z działań dążących do wdrażania zasad zrównoważonego rozwoju w budownictwie. Sposobem ograniczenia zużycia energii jest przede wszystkim zwiększenie izolacyjności przegród budynku poprzez zastosowanie odpowiedniej grubości materiałów termoizolacyjnych do ich ocieplenia oraz ograniczenia zapotrzebowania ciepła do podgrzewu powietrza wentylacyjnego. W pracy wykonano analizę wpływu izolacyjności ścian zewnętrznych i wentylacji na zużycie energii cieplnej w domu jednorodzinnym. Przyjęto sześć wariantów obliczeniowych zakładających grubości izolacji ścian zewnętrznych od 6 cm do 20 cm oraz zastosowanie wentylacji grawitacyjnej lub mechanicznej. Zwiększenie izolacyjności ścian zewnętrznych wpłynęło na ograniczenie zapotrzebowania na energię do ogrzewania od 16% do 19% w zależności od przyjętego wariantu. Zastosowanie wentylacji mechanicznej z odzyskiem ciepła pozwoliło na zaoszczędzenie dalszych 25% - 29%. Zmniejszenie rocznego zapotrzebowania na energię do ogrzewania było największe dla wariantu VI w stosunku do wariantu I-go i wynosiło 39%. Oszczędności związane ze zmniejszeniem rocznego zapotrzebowania na energię do ogrzewania były największe również dla wariantu VI, ale różne w zależności od paliwa zastosowanego do wytwarzania energii cieplnej. Prosty czas zwrotu inwestycji przedstawiony w wariantach od I do VI zależał przede wszystkim od kosztów inwestycyjnych i kosztów zaoszczędzonej energii i różnił się zasadniczo w zależności od źródła ciepła. Keywords: termomodernizacja, wentylacja mechaniczna, rekuperacja, Introduction Limitation of heat energy consumption is one of the efforts running to introduce the ideas of the sustainable development in building branch. Sustainable development idea relies on providing civilization development type which satisfies the needs of the current generation

2 without the decrease of the future generations chances to satisfy their needs. Limitation of heat energy consumption is connected to the reasonable application of the energetic sources and reduction of pollutants emission to the atmosphere and for the particular person is a cost reduction for energy production. The most effective way of energy demand limitation is the increase of insulation parameters of the external barriers of the building using a suitable dimensions of the insulation materials. Another solution is to use the mechanical ventilation system with heat recovery instead of the traditional gravitational system and finally reduction of heat leakage bridges. The result of such efforts is energy storage inside the rooms and thus decrease of heat demand to support suitable indoor air parameters. Particular attempts of energy demand limitation of the house may cause several problems connected with selection of suitable insulation dimension and type of the applied ventilation system without going to the extremes. Moreover, there may be asked a question - what investments should be made to get quick money back from the heat demand decrease. To make the choice possible it is required to be aware what influence on heat demand have the above mentioned factors. The aim of this work is to determine the external barriers insulation and ventilation influence on energy consumption in a single-family building. Theory Heat energy is used in the houses to warm the rooms. Energy demand may differ essentially - depending on the house construction type of insulation and ventilation system. The most important parameter describing the energy effectiveness of the building is the seasonal factor of heat energy demand E. Qh 3 E kwh/ m (1) V Where: Q h heat energy demand in a standard season [kwh/a], V capacity of the heated part of the building [m 3 ]. Heat energy demand of the house (Q h ) is a difference between heat losses (through barriers and ventilation) and utilized internal and sun heat gains. This value is described by the following formula: Where: h Q Q Q Q (2) Q pz - heat loses through the external barriers, Qv - heat losses caused by ventilation, Qsw - sun heat gains through windows, Qi - internal heat gains, - factor of heat gains efficiency, (Byrdy C. 2009). Q pz v sw i

3 According to the Polish Ministry of Infrastructure Regulation from 12 April 2002 about technical criteria for buildings and their localization, a particular house and its systems should be designed to keep heat energy consumption on a possibly low level. Optimal energy consumption for the single-family houses is established when the seasonal factor of heat energy demand E is below the criteria value E 0 or the external barriers satisfy the heat insulation requirements. E 0 value depends on the building shape factor A/V where A is the total area of the external barriers, V is the net capacity of warmed part of the building. On the basis of the calculated value of the A/V coefficient E 0 factor can be determined as: E 0 =29kWh/(m 3 a) when A/V 0,20; E 0 =26, A/V kwh/(m 3 a) when 0,20 < A/V < 0,90; E 0 =37,4 kwh/(m 3 a) when A/V 0,90. Heat energy consumption depends on the amount of the heat which is lost from the building and is replaced by cold air which must be warmed. Heat is lost through external barriers to the external environment (Koczyk 2000). Percentage average shares of heat loses by particular parts of the traditional building are presented in Fig. 1. Fig. 1. Percentage share of particular building elements in heat loses As it is noticeable in fig 1, the greatest heat losses are caused by ventilation. In a traditional house its share varies between 30-40% of total heat losses and is the result of hygienic minima support which relies on supplying of fresh and thus cold air. The greater amount of cold air delivered, the greater heat energy consumption is required to heat the ventilation air. Properly designed ventilation is a very important element of human health care and thermal comfort of indoor air. Water vapor, stinks, carbon dioxide and other contaminants are removed by ventilation with hot air. They are replaced by fresh air which is required to keep suitable comfort parameters of indoor air (Pełech 2008, Opaliński i in. 2003). The ventilation process replacement of warm air by the cold one, results in the room cooling and increasing in heat energy demand. In this case, heat energy consumption is caused by the need to warm cold ventilation air, because air exchange process removes about 30-40% of the whole energy consumed by the single-family house. That s why it is very important to elaborate a suitable solutions of ventilation system to minimize the cold air

4 influence which would not increase the heat energy consumption but still provide the constant inflow of fresh air to the rooms. Other solutions which would provide energy savings are the following: decrease of heat exchange during periods with less air exchange requirements for example when all inhabitants fall asleep or are outside. It is possible to save about 50% of energy. Second solution relies on installation of a heat recuperator in a ventilation system. It is a device applied in a mechanical intake-exhaust ventilation system which constantly warms the air flowing into the building. Methods The object of the analysis was heat consumption in a single-family house located in third climatic zone of a winter season. To realize the aim of the article, three different parameters of the insulation and three variants of ventilations systems were assumed (Wysocki 2008). Table 1. Building technical data Climatic data: Climatic zone: Designed external temperature θ e : Annual average external temperature θ m,e : Meteorological station: Actinometric station: III -20 C 7,6 C Siedlce Mikołajki Default data for calculations: Type of a building: Single-family Type of building construction: Average Type of system heating: Convectional Decrease in heating: No decrease Building geometry: Building level ordinate: -0,25 m Building geometry: Default floor ordinate Lf: 0,00 m Ground water ordinate: -3,00 m Default height of the floor H: 3,20 m Default height of the room Hi: 2,94 m Ground floor area Ag: 144,40 m 2 Ground floor perimeter Pg: 63,13 m Building statistics: Heated area of a building Ah: 285,1 m 2 Heated cubature of the building Vh: 848 m 3 Number of floors: 2 Number of rooms: 20 Calculation were conducted using the non-commercial Purmo OZC software. The most important input data are presented on table 1. In the first variant, treated as basic variant, it was assumed that the external barrier, consists the typical layers with the thermal insulation dimension 6cm and satisfies the regulations about the maximal available value of overall heattransfer coefficient. In the first variant ventilation works in a gravitational system. Other variants assume presence of thicker insulation layer and application of gravitational or

5 mechanical ventilation system. The considered variants and the parameters characterizing them are presented in table 2. Table 2. Variants of calculations External barriers Overall heattransfer Variant insulation coefficient Ventilation type (polystyrene width) U [W/(m 2 K)] I 6cm 0,265 Gravitational II 12cm 0,190 Gravitational III 20cm 0,137 Gravitational IV 6cm 0,265 Mechanical intake-exhaust with heat recovery V 12cm 0,190 Mechanical intake-exhaust with heat recovery VI 20cm 0,137 Mechanical intake-exhaust with heat recovery The details about applied ventilation systems are presented in tables 3 and 4. Table 3. Gravitational ventilation data Default data about ventilation: Type of ventilation: Gravitational Compensating air temperature θc: 20,0 C Ventilation calculations results: Infiltrating air Vinfv: 128,8 m 3 /h Average number of air changes n: 0,6 Inflowing ventilation air Vv: 510,8 m 3 /h Average temperature of inflowing air θv: -20,0 C Table 4. Mechanical ventilation data Default data about ventilation: Type of ventilation: Intake-exhaust Compensating air temperature θc: 20,0 C Ventilation calculations results: Infiltrating air Vinfv: 128,8 m 3 /h Air mechanically delivered. Vsu: 569,2 m 3 /h Air mechanically removed Vex: 569,2 m 3 /h Average number of air changes n: 1,0 Inflowing ventilation air Vv: 826,8 m 3 /h Average temperature of inflowing air θv: -0,7 C Results and discussion Conducted calculations enabled heat losses determination by the particular elements of the building, seasonal heat demand Q h and coefficient of annual heat demand (EA and EV) (Bonca i in., 2000). It also enabled to determine the costs of investment expenditures to rise

6 the building according to the assumed variants, costs of object s exploitation connected to building heating. Finally it was elaborated the economical analysis for the particular variants. Fig. 2 presents comparison of heat demand for all calculation variants. According to the predictions, application of the thicker insulation of the external barrier causes the decrease in seasonal heat energy demand for about 16% in case of gravitational ventilation and insulation width of 20cm, and 17% in case of mechanical ventilation and the width of insulation 20cm. Application of the mechanical ventilation system causes the reduction of the seasonal heat energy demand depending on the insulation width for about 26% in case of the insulation width of 6cm to about 29% in case of 20cm width insulation. Fig. 2. Seasonal heat energy demand Fig. 3. Annual income connected to the decreased heating energy consumption comparing to the Variant Number I

7 Fig. 3 presents the comparison of annual heat energy savings. The greatest savings were obtained for variant Number VI with the best thermal insulation of external barriers and application of the mechanical system of ventilation without any dependence to the applied source of energy. Fig. 4. Simple Payback Time comparing to the Variant Number I Simple Payback Time (SPBT) of the investment relying on the increase of the insulation layer dimension and installation of the mechanical system of ventilation is estimated as a time period after the investments of variants between II and VI will be balanced by the savings from the decreased heat energy demand comparing to the variant Number I. The analysis was conducted under assumptions that the source of heat energy was a boiler powered with natural gas or wood. Significantly greater costs of energy from natural gas combustion caused that SPBT for that source is much shorter comparing to wood and its maximal value for variant number III is 9.4 and is equal to 7.3 for variant number VI. For wood as a source of energy, time of payback is longer 25 years for variant number III and 19.2 for variant number VI. This results show no necessity of object renovation in case of application of wood as a energy source. Conclusions The increase of width of external barriers insulation influenced the limitation of heat energy demand at the level of between 16 and 19% depending on assumed variant. Application of the mechanical ventilation system with heat recovery enabled further savings between 25 and 29%. The decrease of annual heat energy demand was the greatest for the variant number VI and comparing to the variant number I was about 39%. Savings dependent on the decrease of seasonal heat energy demand were also the extreme for variant number VI but were different depending on the applied source of heat energy.

8 Simple Payback Time (SPBT) of the investments presented in variants I-VI mostly depended on the investment costs and savings. It differed significantly depending on type of the energy source. In case of the natural gas combustion, it seems to be to most economical to apply the variant number VI. Despite the fact that SPBT value was not the shortest it was comparable to the variants number IV and V. In case of wood as an energy source no investments would bring savings in short term of investment. References 1. Bonca Z., Lewiński A. (2000), Termorenowacja budynków mieszkalnych. Aspekt techniczny i ekonomiczny, IPPU MASTA, Gdańsk. 2. Byrdy C. (2009), Ciepłochronne konstrukcje ścian zewnętrznych budynków mieszkalnych, Politechnika Krakowska im. Tadeusza Kościuszki, Kraków. 3. Koczyk H. (red.) (2000), Ogrzewnictwo. Podstawy projektowania cieplnego i termomodernizacji budynków, Wydawnictwo Politechniki Poznańskiej, Poznań. 4. Opaliński S., Rabczak S. (2003), Wentylacja grawitacyjna, Oficyna Wydawnicza Politechniki Rzeszowskiej, Rzeszów. 5. Pełech A. (2008), Wentylacja i klimatyzacja- podstawy, Oficyna Wydawnicza Politechniki Wrocławskiej, Wrocław. 6. Wysocki K. (2008), Docieplanie budynków, Wydawnictwo i Handel Książkami KaBe, Krosno.