The modifications to the requirements on energy savings and thermal insulation of buildings in Poland in the years 1974-2021

Residential and public buildings use for heating more than 40% of the total energy consumption in the European Union. Therefore, this paper discusses the modifications to the building energy standard, which is currently in force. It is based on the requirements included in the Polish technical building regulations and standards. The proper energy-saving police have been implemented to this kind of consumers to diminish the energy consumption. The analysis pertains to the values of heat transfer coefficients of building partitions as well as the indexes of the energy demand for various types of buildings. The analysis was conducted between 1974 and 2013. Moreover; the changes within this range, which will come into force in 2014 and will continue to 2021, which act in accordance with the technical requirements suitable for buildings, were also discussed. Furthermore, minimal thicknesses of insulation materials which enable meeting this requirements of a heat transfer coefficient for building partitions, were examined in the article.


Introduction
Energy-saving policy applied for buildings has significant global impact.Energy consumption in buildings in developed countries comprises 20%-40% of the world final energy consumption [1].What is more, about 63% of the total energy consumption in the European buildings sector is also used in residential buildings [2].
Indeed, there are a lot of technical and social possibilities to reduce energy consumption in existing buildings; for instance, described by Ueno et al. [3] and by Ouyang and Hokao [4], who proposed improving the occupants' domestic energy consumption through education about energy saving behaviour.
But to reduce the energy consumption in future buildings, designers should choose the proper heating system and the source of its energy supply [5][6][7]; what is not naturally the fundamental and the cheapest version, and is not very often used in the final version of the project after consultations with investors.
From another side, energy savings polices, which are obligatory, may significantly contribute to energy savings, what was also described in [8][9][10][11][12].This situation may be seen in Poland (see Fig. 1), where the energy consumption per one person declines to a greater extent in comparison to EU27.Fig. 1.Energy consumption in households per one person in Poland and EU27 [13] Therefore, the objective of this study was to show energy-saving policy used in Poland since 1974.What is more, it is also a prospective policy for 2021 treated as exemplary influence of energy policy on the energy conservation, which is on the top of commonly accepted energy hierarchy.

Energy-saving policies in Poland
During the design of a new building or the modernisation of an existing one, it is necessary to take the building energy standard requirements into account since they are frequently defined as requirements for a building in terms of its energy consumption.For over 30 years, the energy saving alterations have been introduced to the binding standards [14][15][16] or technical building regulations [17,18].Firstly, the changes referred only to maximal values of heat transfer coefficients (marked with 'k' then 'K' and finally 'U' expressed in [Wm -2 K -1 ] for the opaque and transparent partitions.In 1998, the regulation which aimed at supporting thermomodernisation investments [19,20] was passed together with the executory order [21], which showed that thermomodernised buildings should have better thermal insulation parameters than the newly built ones.Furthermore, in 2002, additional requirements were introduced on the maximal (boundary) value of the index of seasonal heat demand for heating.Such an index (marked with E and expressed in [kWh m - 3 year -1 ]) showed only building demand for usable energy; and thus, it should be calculated in accordance with Polish Standard [21].The boundary value (marked with E 0 ) depended on the building shape coefficient (marked with A/V, where A in [m 2 ] was the total sum of the area of all partitions separating the heated space from the outdoor air, the unheated space and ground, calculated by the external outline, V in [m 3 ] -net cubic volume of a heated part of building).In 2008, the requirement concerning the building demand for nonrenewable primary energy was introduced to the domestic regulations.It determined the maximal value of annual index calculation of the demand for heating, ventilation, cooling, warm water preparation for residential buildings.When it comes to other buildings, there is also a demand for the built-in lighting.This index is marked with EP, and its value is expressed in [kWh m -2 year -1 ].Formulas allowing for the calculation of its boundary values for, a socalled, reference building depending on its function, shape coefficient and cooling facilities, are stated in the technical building regulations [17].The requirements for the thermal insulation of building partitions were implemented simultaneously with the introduction of E and EP; and additionally, in 2008 together with the thermal insulation of conduits, fittings and fixtures in installations.In 2002, the provisions which referred to the energy efficiency of fixtures and keeping the energy demand in a building at a reasonably low level, were introduced for the first time in the Decree of the Minister of Infrastructure [17].
The affiliation of Poland to the EU caused the necessity to implement the Directive 2002/91/EC known as "The energetic characteristics of buildings."In Poland, it was realised by the introduction of modifications to the Building Code Act as well as the executive regulation [23] and changes to the regulations [17,21].The obligation to perform the energy characteristics of a building at the stage of its design, opening, sale or lease was imposed the 1 st of January, 2009.The uniformed methodology to determine the integrated building energy characteristics as well as draft the energy certificates in accordance with uniformed formulas presented in the Decree of the Minister of Infrastructure [23] came also into force.Furthermore, the obligation to conduct periodic inspections of boilers and air conditioning installations; not only in terms of their technical state, but first and foremost, due to the efficiency to generate energy and the correctness of choice of power capacity adapted to the building demand.In the modified technical building regulations [18]; effective from January 2014; the schedule for the years 2014-2021 was established.When it comes to its requirements on the thermal insulation of partitions and EP index, they are even more strict.

Opaque partitions
The maximal values of heat transfer coefficients (U) for various types of opaque partitions, effective in accordance with technical building regulations at particular periods, values binding during the preparation of energy audits used for obtaining thermomodernisation funds and the requirements (valid since January 2014, in accordance with Decree of the Minister of Infrastructure, Construction and Maritime Economy [18], are presented in Table 1.It demonstrates progressive changes and the extent to which the requirements are tightened within this scope, for the inside temperature of a heated room or with the difference between the heated and unheated space of at least 16°C.1.00 1.00 1.00 -( 1) -( 1) -( 1) -( 1) - (1)   (1) -not determined, (2)-without requirements

Windows, balcony doors and exterior doors
Similarly to the item 2.1.2,the maximal values of heat transfer coefficients (U) of windows and balcony doors are displayed in Table 2; whereas, in the case of exterior doors they are presented in Table 3.The tables illustrate continuous changes and the extent to which the requirements for various types of buildings, allowing for different internal temperatures and a climate zone, are tightened.

The index of usable energy demand (E)
In April 2002 [17], the requirement referring to the index boundary values E 0 (seasonal demand for thermal energy to heat a building) was introduced for the first time to the regulation "concerning technical requirements, which buildings and their locations should comply with" for multi-family and multi-apartment buildings as well as for a single family building.The index boundary values E 0 is calculated according to the dependencies presented in Table 4 (E 0 * is given for 2.5 meters of room clear height) and by taking the shape coefficient of building (A/V) into account.When it comes to the calculations of E index, the Polish Standard [22] was valid.The requirements of regulation on energy savings and thermal insulation were assumed to be fulfilled for a single family building if the building partitions complied with the requirements of heat transfer coefficients (U) or E value did not exceed E 0 value; whereas as for multi-family and multi-apartment buildings, the requirements of E and U should be met.In the case of a public utility building and manufacturing building, it was sufficient to meet the requirements of U.Such provisions were in force until November 2008.

The index of the demand for nonrenewable primary energy (EP)
In November 2008, together with the regulations compulsory to perform the energy characteristics of a building, the provisions on determining the boundary index values of the demand for nonrenewable primary energy EP expressed in [kWh m -2 year -1 ], entered into force.The buildings were divided according to the two criteria i.e. the function and the occurrence of a cooling installation.While determining EP index, the energy for different purposes should be taken into consideration depending on the building adherence to a given group, which is presented in Table 5.  where: Af -heated usable area, Af,c -cooled usable area Whereas, the provisions enabling the determination of the boundary values of EP index are shown in Table 6.It should also be stated that as for a reconstructed building, it is permitted to increase these values no more than 15%.These regulations were in force until the 31 st of December, 2013.Nevertheless, as in the case of tightening the requirements of heat transfer coefficients U, stringent requirements concerning the boundary values of EP index and the modifications to the manner of its calculation were introduced since the 1 st of January, 2014.The modifications and their time schedule are demonstrated in Table 7.

A case study
This case study compares the boundary values EP according to still valid technical building regulations to the values which have come in force in January 2014.Three types of buildings were selected to the analysis: a multi-family building, a nursing home and an office building.The characteristic parameters of the buildings are shape coefficient of a building (A/V e ) equal to 0.6, heated usable area (A f ) equal to 1000 m 2 and area of external walls calculated by the external outline of a building (A w,e ) equal to 1300 m 2 .It was also assumed that the whole area (A f ) is cooled (when a cooling installation occurs in a building).All calculations on this section are performed in accordance with the Decree of the Minister of Infrastructure, Construction and Maritime Economy [18], EN ISO 13790 [24] and EN ISO 6946 [25].
The results of this analysis are shown in Table 8 and in Figure 2. By contrast, the modification of thermal insulation of building partitions is based on continuous decrease in the maximal values of heat transfer coefficients (U) of these partitions.As a result, in new building or while reconstructing existing ones, there is a necessity to apply bigger thickness of traditional insulation materials or to replace them with materials with lower heat conductivity coefficient ( ).The minimal thicknesses of insulation materials for various values, for sample U values in initial condition and target U values consistent with valid technical building regulations, are presented in Table 9 for the external wall, and in Table 10 for the flat roof.Moreover, the difference in the trade thickness of insulation ( d) between current requirements and target ones in 2021, was calculated.

Conclusion
Energy-saving policy used in Poland since 1974 and proposed to 2021 is the good example of influence of energy policy on energy conservation.
From the analysis conducted, it appears that in the considered period, substantial decrease of heat transfer coefficients (U) occurred for several times in Poland.When it come to the technical building regulations, in force since January 2014, further limitations of this parameter are imposed.
The boundary value of the demand index for nonrenewable primary energy EP decreased considerably for different types of buildings.
The modifications introduced impose meeting both requirements of U and EP, not only U or only EP as it was so far.The limitation on the value of U coefficients forces the application of bigger thicknesses of thermal insulation for sample partitions i.e. 7 cm or 5 cm for an external wall, and 12 cm or 15 cm for a flat roof depending on the heat conductivity coefficient of an insulation material.All the described modifications to thermal insulation cause the reduction of heat consumption in a building which leads to the limitation of carbon dioxide emissions into the atmosphere.Consequently, such a phenomenon contributes to the realisation of the Polish Energy Policy premises.
operating time above 2500 h/year EP value residential buildings without cooling: EP = EPH+W residential buildings with cooling: EP = EPH+W C other buildings without cooling: EP = EPH+W L other buildings with cooling: EP = EPH+W C L

Table 1 .
The values of heat transfer coefficient for the selected building partitions

Table 2 .
The values of heat transfer coefficient for windows and balcony doors

Table 3 .
The values of heat transfer coefficient for exterior doors

Table 4 .
[17]boundary values E0 according to the Decree of the Minister of Infrastructure[17]

Table 5 .
Criteria for the division and types of energy demands of a building

Table 6 .
The determination of index value EP according to the Decree of the Minister of Infrastructure, 2008 Af -heated usable area, A -total area of partitions separating heated part from outside air, ground, and the unheated part, Ve -heated cubic volume, A/Ve -shape coefficient of a building, Aw,e -area of external walls calculated by the external outline of a building, Af,c -cooled usable area, Vcw -unitary daily consumption of water per one reference unit [dm 3 day -1 ], bt -dimensionless time of the use of warm water system per annum, a1 -share of area Af per one reference unit, PN -electric power reference [Wm -2 ], t0 -time of lighting use per annum [h year-1 ]

Table 7 .
Requirements on EP according to the Decree of the Minister of Infrastructure, Construction and Maritime Economy (2013) in force since 01.01.2014

Table 8 .
Sample boundary values of EP index

Table 9 .
The minimal insulation thickness for an external wall

Table 10 .
The minimal insulation thickness for a flat roof