Impact of U-Values in Evaluation of Implemented Energy Efficiency

Measures and Energy Savings in Public Buildings in Context of Kosovo

Legislation

KRESHNIK MUHAXHERI, BLETA BERISHA MUHAXHERI

Department of Energy Efficiency,

University for Business and Technology,

Magjistralja Prishtine - Ferizaj - Rrethi te QMI, Prishtina,

KOSOVO

Abstract: - The purpose of this paper is to articulate the immediate need for review and improvement of

Kosovo Building Regulations and Codes in the field of implementation of EE measures and specifically

reducing U-values for all building envelope elements, to be comparable to European Standards, and present a

specific contribution for EE measures in public building stock in Kosovo as the real potential for huge energy

savings.

In this paper the results of the several years’ long research on the impact of implemented energy efficiency

measures in the 70 selected public buildings are presented, in light of calculated U-values with a brief

description of the constituent elements of the building envelope and their corresponding U-values, such as

external walls, windows, doors, floors and roofs, comparing their impact in the phases before and after the

implementation of Energy Efficiency measures.

A building designed to use the minimum quantity of thermal energy for heating and cooling to achieve a

healthy environment and thermal comfort is considered an Energy Efficient building. The U-values of the

building envelope are the dominant factors in its thermal performance and play an important role in reducing

the energy consumption of buildings. Many studies confirm that in cold climates, from the total annual energy

consumption for heating and air conditioning of public buildings, approximately 50% of the energy is

consumed through the heat transmission of the building envelope.

The achieved results after implementation of EE measures have shown significant improvement of U-values for

both opaque parts of building envelope and belonging fenestration compared with the referent values set in

Kosovo Technical Regulation which is actually in use for designers in Kosovo.

Depending on wall thickness and installed insulation achieved, results of U-values for external walls were 0.31-

0.35 W/m2K, much lower than recommended in old technical Regulations, lower than recommended by

ANA_IAE, but still higher than values from Finish and Norwegian building codes. Calculations have shown

that in the case of implementation of improved U-values according to the Finish building code the impact of

walls on U-values in overall energy savings is around 36.86%.

Windows and doors look the sensitive part of the building envelope and show that it is more than the required

strengthening of requirements in future Kosovo Building code reducing the U-values for doors and windows at

0.8 W/m2K. Analysis has shown huge improvement and potential increase of energy savings with 55.25 % for

part of fenestration.

Detailed analysis of the collected U-values data for roofs has shown that there is sufficient space for

improvements in Building codes and it is a highly recommended change of existing criteria and at least

application of the values from EU building codes. With this change, potential energy savings in part of roof

covers might be 44.24%.

Working as an EE expert in Kosovo Energy Efficiency Agency (KEEA) and World Bank (WB) and European

Union (EU) projects, the author has identified the necessity of improvement of actual Kosovo legislation in the

field of EE policies for public buildings, addressing the importance of the appropriate building envelope’s

thermal insulation to reduce its thermal losses and stipulating the impact of the U-values in the evaluation of

implemented energy efficiency measures and energy savings in public buildings.

The overall energy savings with applied EE measures and potential energy savings in case of improvements of

Kosovo Technical Regulation according to recommended standards and EU countries’ experiences are

presented in a separate table showing economic net savings, an average payback period and overall potential

reductions of CO2 emissions.

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DOI: 10.37394/232015.2023.19.2

Kreshnik Muhaxheri, Bleta Berisha Muhaxheri

E-ISSN: 2224-3496

Volume 19, 2023

The presented results indicate a recommendation for further studies that may include other building typologies

and may disclose additional differences between the energy performance criteria in the analysed building

codes.

Key-Words: - U-values, building codes, public buildings, EE measures, energy savings.

Received: August 25, 2022. Revised: September 2, 2022. Accepted: September 10, 2022. Available online: September 28, 2022.

1 Introduction

This paper aims the review the results of achieved

U-values of building envelope and fenestration after

implementation of EE measures and to compare

with actual regulation and codes and standards as

well [1,3,27,28]. Moreover, the overall energy

savings with applied EE measures and potential

energy savings in case of improvements of U-values

in the future Kosovo Technical Regulation,

according to recommended standards and EU

countries’ experiences, are presented in a separate

table showing economic net savings, an average of

payback period and overall potential reductions of

CO2 emissions.

In Kosovo, as in most other countries, the energy

with which the buildings are supplied as well as the

activities in them, constitute an important part of the

total energy consumption. According to the Energy

Balance published by the Ministry for Economic

Development, the primary energy supplied in

Kosovo was 2,524.32 ktoe for 2020, which

represents an increase of 15.6% compared to 2010

[30]. The final energy consumption for 2020 was

1,441.5 ktoe. In many cases, this means an increase

of 30% in total fossil fuel consumption and almost

50% in total electricity consumption.

From this overall consumption, more than 50% is

needed for covering thermal losses through building

and the use of building materials with low

significantly reduces the inefficient use of energy

keeping the required level of thermal comfort [4].

The inefficient use of energy is one of the main

concerns not only for Kosovo but for the region as a

whole. Primary energy consumption per unit of

GDP (GDP-Gross Domestic Product) is

significantly higher than in EU countries (13 times

higher than in Germany, 10 times higher than in

France) [WB Statistics].

During the post-war years, Kosovo has made

attempts to regulate the legal framework in the field

of Energy Efficiency, starting with the Law on

Energy No. 2004/8 in 2004. Later continued with

the Law on Electricity No. 03/L201, Law on the

Energy Regulator No. 03/L-185 and Law on Energy

No. 03/L-184 which replaced the old version of the

same Law from 2004! Law no. 06/L-079 establishes

the legal framework necessary to promote and

improve energy efficiency in Kosovo with the aim

of defining energy efficiency targets and achieving

these targets through the implementation of energy

efficiency measures. Moreover, this Law is

supposed to be accompanied by EE plans, national

strategies, national objectives, targets and policy

measures in the field of energy efficiency.

As a result of close cooperation with the former

Ministry of Environmental and Spatial Planning

(MESP) author worked in the transposition of EU

Directive 2010/31/EU on Energy Performance in

Buildings Kosovo, in 2016 issued Law no. 05/L-101

on Energy Performance in Buildings. This important

Law is partly in accordance with Directive no.

2010/31/EU on the Energy Performance of

Buildings; Directive 2012/27/EU of the European

Parliament and the Council on Energy Efficiency

According to the obligations of the law, the Ministry

has drafted and enforced several regulations and

codes for the implementation of the EPB law.

Taking into account that since 2021, all new

buildings must be nearly zero-energy buildings

(NZEB) and since 2019, all new public buildings

should be NZEB [7,20,21,25], this indicates the

need for significant review and amending of actual

Kosovo legislation and accompanying regulations

which can lead to benchmarking and improvement

of the U-values as impacting factor in the evaluation

of EEM and energy savings in public buildings [29].

The basis of this study is the WB and EU-funded

projects of implementation of Energy Efficiency

Measures in public buildings in Kosovo, which

since 2012 has involved the energy-efficient

refurbishment of 70 public buildings across Kosovo

(administrative buildings, schools and hospitals).

The purpose of this investment was to encourage

more effective use of energy across Kosovo with the

major goal to implement energy efficiency

improvement in public buildings and the verification

of energy cost savings [1,13].

The detailed review of all U-values of building

envelope elements in light of actual EU standards

and recommended criteria from the developed

countries has shown great potential for energy

savings and CO2 reduction. [8,9,10,11]

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Some studies recommend doing comparisons of

building energy performance criteria which may

facilitate benchmarking of such criteria [6]. For

example, benchmarking of Energy Performance of

Buildings Directive applications in different

countries, or issuing the new version of a national

building code and/or regulation, comparing it with

its older regulations and codes versions, as is the

case in Kosovo.

Old Technical Regulation on Thermal Energy

Saving and Thermal Protection in Buildings issued

in 2009[18], regulates technical requirements for

thermal energy saving and thermal protection, and

U-values for envelope components. Requirements

relate to both new building projects, and existing

buildings adoption and reconstruction projects with

internal heating temperatures of more than 12ºC.

Despite all the shortcomings, this Regulation with

few improvements [31] is still in force and

frequently used by designers. Knowing that building

codes and regulations are considered to be an

effective policy tool to reduce energy use in

buildings [6,20,21,22], this significantly increases

the need for regulation of building codes adopting

experiences from neighbouring countries and

similar climates in European countries. Having in

mind the actual energetical situation in Kosovo and

worldwide, and the booming construction industry

in Kosovo, improving the energy efficiency of the

public buildings and in general building stock is

highly impacted by a variety of legislative measures

and improvement of actual legislation and building

codes in the field of energy efficiency. This

improvement can have a powerful economic and

social impact.

2 Results and Discussions

Since 2016 Kosovo is attempting to establish

legislation and required regulations [32], with

provisions for the energy performance of the

buildings with a further goal to reach nearly zero

energy consumption building [24,25,26]. To achieve

the goal and fulfil the requirements of the European

legislation [20,21,22] a further attempt should be

focused on interventions in codes such as lower U

value limits in the opaque building elements of the

building envelope and fenestration [2].

The transmission of heat from the exterior to the

interior is one of the main mechanisms used for the

calculation of heat losses of all audited buildings

[5]. Understanding the energy performance of the

building envelope was crucial for determining the

amount of energy that was required for heating and

energy savings. Therefore, once the building was

characterized, the heat transfer through the main

materials along the outer perimeter was calculated

for all building opaque envelopes and fenestration.

The unit for determining heat losses through the

materials of the building envelope elements defined

in this paper as the U-value is used during the

project analysis as a criterion for determining the

energy performance of buildings. The U-value

determines how well an element of the building

envelope conducts heat from one side to the other,

or how much heat is lost through a given element of

the building envelope. These values are

deterministic standards used in building codes to

specify minimum Energy Efficiency values for

walls, windows, doors, floors and roofs as building

envelope elements. The U-values also determine the

energy efficiency of the materials in a component or

part of the building. A low U-value defines high

energy efficiency. Combined, windows, doors, walls

and roofs can absorb or lose heat and, as a result,

energy consumption for cooling or heating

increases. For this reason, the minimum values for

achieving the energy efficiency of these components

of the building envelope should be set and

harmonized in the future revised building codes, to

be comparable with Energy Performance of

Buildings Directive (EPBD) recommendations.

Analysis of the energy consumption for all 70 public

buildings before and after implementation of EE

measures is done including potential net energy

savings in case of improvement of building

envelopes U-values. Based on these results are

recalculated economic net savings and overall

reductions of CO2 emissions.

The required energy for heating in the winter period,

needed to maintain the designed temperature

difference to fulfil comfort criteria, can be

calculated by the following equation:

𝑃 = ∆𝑇 · ∑𝑈ᵢ 𝑆ᵢ

Where is:

∆𝑇 temperature difference between inner and outer

environment

U thermal transmittance for specific envelope

element

S calculated area

The given equation, of course, is an approximation,

because the temperature difference between the

starting point and ending point gives a difference in

form of sensible heat, stored in building materials

[10,12,13,14].

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Table 1. Results of implemented EE Measures

OVERALL RECAPITULATION

Energy consumption before implementation of EE measures

51,248,451

kWh /year

Energy consumption after implementation of EE measures

33,429,687

kWh /year

Net energy savings after EE measures

17,818,764

kWh /year

Potential Net energy savings- U values in future Regulation

10,110,367

kWh /year

Potential Overall Net energy savings-after EE measures and applied new

regulation

27,929,131

kWh /year

Economic net savings

18,064,136

€

Net savings

5,161,182

€/year

Investments in EE measures

18,680,487

€

Overall potential reductions of CO2 emissions

20,303

[ton CO2/year]

Average payback period/total investments

3.5

years

With possible improvements of Kosovo Technical

Regulation related to the decreasing of U-values for

all opaque building envelope elements and

fenestration as well, by EU standards and EU

countries regulations surveyed public buildings in

Kosovo will reduce overall energy consumption by

an additional 10,110,367 kWh/year which means an

improvement from 56,74%.

In the continuation of this chapter, the results of

measurements and calculations of U-values for each

separate element of the building envelope before

and after the implementation of Energy Efficiency

(EE) measures will be presented, as well as

discussed and presented in relevant tables and

diagrams [1,15,16,17]. Moreover, a brief description

of the constituent elements of the building envelope

and their corresponding U-values, such as external

walls, windows, doors, floors and roofs, is given,

comparing their impact in the phases before and

after the implementation of EE measures.

For comparison, U-values extracted from the two

different countries’ building codes, Finland and

Norway, [6], were used and presented in various

diagrams, while their impact on the reduction of

energy consumption is calculated based on the

recommendation of the Finish code compared with

the Kosovo Technical Regulation.

Comparing the energy performance criteria used in

different national building codes may provide

opportunities to learn from different strategies for

improving building energy performance and may

facilitate actions towards such harmonization of

Kosovo national codes.

2.1 External Walls

The most important element of the structure of the

building must undoubtedly be the external wall. The

external wall must be structurally strong, stable and

durable, resistant to climatic conditions and

humidity, heat transfer and the impact of sound

from the external environment [2,9,13].

The main purpose of using energy efficiency

measures in selected public facilities was part of the

strategy proposed by Kosovo Government

institutions, as a general solution to the problems

related to the use of conventional energy in

buildings. For this purpose, the author has

systematically analysed the different constructions

of external walls, identifying their U-values and

comparing them with the values recommended in

the Technical Regulation on Thermal Energy Saving

and Thermal Protection in Buildings of the Republic

of Kosovo (TRTES) [18,31] and those

recommended by the International Energy Agency

(ANE-IAE) for the best performance of buildings,

as well the U-values extracted from the three

different countries building codes, Finland and

Norway[6].

For the selected 17 public buildings located in

Pristina, the U-values of the walls before the

implementation of the measures are spread over a

wide range from 0.45W/m2K to 3.63 W/m2K, while

the worst case was in the Technical Faculty in

Pristina. A wall with the lowest U-value was

identified in the newly reconstructed hospital

building, so in that building and a few others, there

were no further interventions on the external walls

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since the U-values were within the framework of the

planned values.

After the implementation of the EE measures, the

U-values have changed inherently way and with

this, the consumption of thermal energy has also

been proportionally reduced. U-values after

measures have reached levels from 0.25W/m2K to

0.57 W/m2K, which are again lower values than

recommended (0.60 W/m2K) by ANA_IAE (The

Eurima Ecofys VII study 2007), but lowest U-values

very similar to Finish building code at 0.220

W/m2K, and higher than Norwegian building code

at 0.180 W/m2K.

Table 2. Structure of the external walls of public buildings

EXTERNAL WALL TYPES AND THEIR THICKNESS

External wall

type

Thick clay

blocks,

plastered -

without

thermal

insulation

with

plastered

blocks,

insulated

with perlit

of 4cm

multi-layered,

brick facades and

eternite tiles

containing

asbestos, inside

plasterboard

with blocks

and

plastering-

without

thermal

insulation

with multi-layered

clay blocks, EPS

and plastering on

both sides

of concrete,

without

plastering and

without

insulation

thin from

solid

bricks,

facade

bricks,

plastered

on both

sides

Total

Number of

buildings

Wall thickness

25-30 cm

38 cm

25 cm

38 cm

25 cm

38 cm

The analysis of the construction structure of the

external walls shows that they also depended on the

construction period. For the 25 schools with solid

brick walls built in the period 1950-1980, the U-

values before implementation of EE measures were

between 1.12 W/m2K, for only a few schools with

external walls of 50 cm thickness, till 1.37 W/m2K,

for most of these schools with the thickness of the

outer walls of 38cm. After the implementation of

the measures, the walls in these schools have

reached values between 0.31-0.33 W/m2K, lower

than recommended by ANA_IAE, but still higher

than values from Finish and Norwegian building

codes.

Our analysis has shown that in case of

implementation of improved U-values according to

the Finish building code the impact of walls U-

values on overall energy savings is around 36.86%.

The U-values identified before the EE measures

implementation for the other 26 schools, built with

external walls from perforated blocks, of 25 cm

thickness, without thermal insulation, built in the

period 1980-2004, have values from 1.80 W/m2K in

most cases, and up to 1.92 W/m2K, in rare cases,

when the walls have been plastered. After the

implementation of EE measures in these buildings,

the U-values of the external walls were in most

cases around 0.35 W/m2K. In the two schools in

which the external walls were previously

reconstructed, the U-values calculated with the

thickness of the insulation placed reached the values

of 0.35 W/m2K, therefore the intervention was not

foreseen.

The following diagram in Fig.1, presents the

average values identified before and after the

implementation of EE measures.

Fig. 1: U-values for external walls of public buildings compared with standards and codes

0,5

1,5

2,5

3,5

Min average Max. Min average Max. Kosova Norway Finland

Before After Regulation / codes

W/M2K

U values for walls

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It is characteristic that on the external walls with a

thickness of 50 cm, no big differences were

observed in the achieved U-values (0.31-0.35

W/m2K), compared to the external walls with a

thickness of 38 cm and 25 cm, since the same

thickness of thermal insulation of 8 cm, was

installed. This articulates the need to optimize the

thickness of the thermal insulation, depending on

the type and thickness of the external wall.

Another factor that has been identified during the

implementation of EE measures is the avoidance of

thermal bridges to achieve the correct U-values after

the implementation of the EE measures. This has

been achieved through the complete insulation of

the vertical facades, including the elements of pillars

and beams, architraves and elements around doors

and windows, balconies, consoles and other critical

building elements. It was found that the transitions

from the facade to the roofs were a critical part that

should be treated with care.

In the following Fig.2 are given U-values for

external walls for all buildings before and after the

implementation of the EE measures.

Fig. 2: U-values for external walls for all analysed public buildings before and after EE measure

2.2 Windows

In many of studies of the impact of energy

efficiency measures in public buildings and their

energy requirements have been treated as a black

box, leaving room for architects and engineers to act

on improvements [2,9,11]. The role of the window

is not explicitly specified, but the treatment was

holistic and integrated as a combined effect of

energy efficiency measures in the building

envelope, such as higher levels of thermal

insulation, better windows and better sealing, high-

quality spacers, heat recovery from flue gases, etc.

In separate studies, the importance and role of

windows in public buildings have been addressed

[9]. It has been found that the cooling energy needs

in the summer period are influenced by the glazing

size, orientation, ventilation rate, internal thermal

load and light penetration. On the other hand,

heating requirements are mainly influenced by the

degree of ventilation, climatic zone, orientation and

type of glazing.

However, the annual heating is mainly influenced

by the windows’ U-values and not only by the solar

transmittance. Thermal comfort is largely influenced

by glazing [23]. In the summer season, the size of

the glazing and the transmittance of solar energy are

important parameters, while the size of the glazing

and the U-value are important for the thermal loads

in the winter season. With this motivation, the

author has approached the detailed analysis of all

types of windows in the treated public buildings and

the possibility of intervention within the EE

measures, not forgetting the need for significant

revision of the current regulation and codes.

The window U-values highly depend on the

characteristics of the frame, glazing and their

current condition. The standard window U-value

calculation includes the average U-value of the glass

(window frame value (Uf), and the linear

transmittance due to the combined thermal effect of

the glazing, sealant and frame (Ψg value).

The European standard EN ISO 10077-1, Part 1,

defines the calculation of windows U-values based

on the four components of the overall transmittance

- the thermal transmittance of the glazing, of the

panels, of the frame and the linear thermal

transmittance of the frame and glazing connections.

The reference values to compare the U-values for

windows before and after the implementation of the

EE measures are referred to the European standards

0,00

0,50

1,00

1,50

2,00

2,50

3,00

3,50

4,00

(W/m2K)

U values ( Walls) for Public buildings

U-value before (W/m²K) U-value after (W/m²K)

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for windows in the public sector, EU member states

codes, as well as the Technical Regulation of

Kosovo, mentioned above.

In the school buildings, the U-values of the

windows before the implementation of EE measures

varied from 2.5-5.2 W/m2K; of which in 2 schools it

was 2.5 W/m2K, in 4 schools it was 2.8 W/m2K, in

28 schools it was 3.5 W/m2K, in 6 schools 3.8

W/m2K, in 7 schools it was 4.0 W/m2K, in 3 schools

4.5 W/m2K, and in the last 4 schools it was 5.2

W/m2K.

Table 3. U-values for window- before and after implementation of the EE measures and compared with

standards

. Description

U-values

before the

measures

[W/m2K]

U-values

before the

measures

[W/m2K]

U-values

after the

measures

[W/m2K]

U – values

according to

Kosovo

Technical

Regulation

[W/m2K]

U – values

according

to the 2017

Finish

building

code

[W/m2K]

U – values

according to

the 2017

Norwegian

building

code

[W/m2K]

17 public buildings in total

1.8-4.5

≤ 1.8

≤ 1.2

≤ 0.8

7-without implemented EE

measures

1.8

10- Complete new

1.4

53 school buildings in total

2.5-5.2

≤ 1.8

≤ 1.2

≤ 0.8

4–without implemented EE

measures

2.5 - 2.8

8-complete renovation

2.2 - 2.8

11–New and complete reparation

30–Complete new

The U-values of the windows after the

implementation of EE measures have been

substantially reduced, varying from 1.8-2.8 W/m2K.

In 30 schools completely new windows have been

installed and in 11 others the old windows have

been partially replaced with new ones with a U-

value of 1.8 W/m2K.

Collecting all U-values for new and repaired

windows for all 70 public buildings and comparing

them with the data from the Finland building code

we have concluded that is more than required

strengthening of requirements in future Kosovo

Building code reducing the U-values for doors and

windows at 0.8 W/m2K. Analysis has shown room

for huge improvement and potential increase of

energy savings with 55.25 % for part of fenestration.

The following diagram in Fig. 4 describes best the

average U-values of windows of public buildings

before and after implemented EE measures,

compared with Kosovo Regulation and two EU

states’ building codes.

Fig. 3: U-values for windows for all analysed public buildings

Min Average Max. Min Average Max. Kosova Norway Finland

Before After Regulation / codes

W/M2K

U values for windows

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2.3 Doors

As with the windows, the U-values of doors depend

on the characteristics of the frame, glazing and their

current condition [2,9,10,14]. The standard door U-

value calculation includes the average U-value of

the glazing (Ug), the U-value of the door frame (Uf),

and the linear transmittance due to the combined

thermal effect of the glazing, sealant, and frame

(value Ψg).

The European standard EN ISO 10077-1, Part 1,

defines the procedure of the calculation of U-values

for doors based on the four components of the

overall transmittance - the thermal transmittance of

the glazing, of the panels, of the frame and the linear

thermal transmittance of the frame joints and

glazing.

The reference values to compare the U-values for

doors before and after the implementation of the

measures are referred to the European standards for

windows in the public sector, national codes of two

EU states, as well as the Technical Regulation of

Kosovo, mentioned above.

In the 17 selected public buildings, the Audit Report

has identified the U-values of the existing doors,

which ranged between 1.8 W/m2K in the three

public buildings in which no intervention was

planned and from 2.80 W/m2K to 4.50 W/m2K in

the other group of buildings in which the

intervention was carried out with the complete

replacement of doors, replacement of glazing or

door joints and handles to reach the required level of

U-values < 1.8 W/m2K according to the criteria of

the Technical Regulation for Thermal Energy

Saving of Kosovo.

In cases when the complete replacement of the

doors was required, the U-value reached the level of

1.40 W/m2K, lower than recommended by TRTES,

but higher than Norwegian and Finish building

codes, while in the facilities where there were no

interventions, it remained at 2.80 W/m2K, higher

than recommended by Regulation as initial

reference.

In school buildings, U-values for doors varied from

2.8 – 5.2 W/m2K; of which 9 schools had a U-value

of 2.8 W/m2K, in 23 schools it was 3.5 W/m2K, in 6

it was 3.8 W/m2K, in 7 schools it was 4.0 W/m2K, in

6 schools it was 5.0 W/m2K, and in 2 schools was

5.2 W/m2K.

After the implementation of the EE measures, the

U-values of the doors changed a lot depending on

whether the measures were implemented or not, and

varied in the values of 1.8 -2.8 W/m2K; of which in

47 school’s new doors with a U-value of 1.8 W/m2K

were installed, in 3 schools there were small

interventions in glazing and sealing and gloves and

the U-value reached 1.8 W/m2K while in 3 schools

without EE measures the doors have remained as

before with a U-value of 2.8 W/m2K.

Table 4. U-values for doors- before and after implementation of the EE measures and compared with standards

Description

U-values

before the

measures

[W/m2K]

U-values

before the

measures

[W/m2K]

U-values

after the

measures

[W/m2K]

U – values

according

to Kosovo

Technical

Regulation

[W/m2K]

U – values

according

to the

2017

Finish

building

code

[W/m2K]

U – values

according

to the 2017

Norwegian

building

code

[W/m2K]

17 public buildings in total

1.8-4.5

≤ 1.8

≤ 1.2

≤ 0.8

3-without implemented EE measures

1.8

1- Complete repaired

2.8

1.4

13- Complete new

2.8

1.8

53 school buildings in total

2.5-5.2

≤ 1.8

≤ 1.2

≤ 0.8

3–without implemented EE measures

2.8

3-complete renovation

1.8

30–Complete new

1.8

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The following diagram in Fig. 5 clearly describes

the average U-values of doors in public buildings

before and after implemented EE measures,

compared with the actual Kosovo Regulation and

two EU states’ codes.

Fig. 4: U-values for doors for all analysed public buildings

2.4 Roofs

By definition, the roofs are the constructive

elements of the envelope of the building which close

the building from the upper part to protect it from

climatic conditions - rain, snow, wind, sun,

temperature changes, etc. [12]. The analysed public

buildings have different constructions and based on

the technical solutions, EE measures have also been

proposed to reduce heat losses and reduce energy

consumption.

Thermally poor, uninsulated roof constructions,

have been identified in some buildings, such as

sloping roofs with wooden timbers and concrete

beams, without thermal insulation and leaking

during rains. In some others, the flat roofs are

covered with a sloping roof as a superstructure to

avoid rain penetration, but in the thermal aspect,

they are very weak. In hospitals, other roof

structures have been identified - sloping with

concrete and on the side parts, bricks with holes.

The coverings of these buildings have also varied—

from asbestos sheets to uninsulated metal sheets.

Table 5. Types of roof covers

Type of roof covers

Clay tiles

Metal sheet

Asbestos

Bitumen tiles

Flat roof

Total

Public buildings

Fig. 5: Types of roof covers for all analysed public buildings

In 17 selected public buildings, different U-values

of the roof constructions have been determined by

the type of construction of the roof, covering, and

thermal insulation has been identified and differs

from the value of 0.39 W/m2K for the student

dormitory building, which is a new building with

the pitched roof with a small slope, with thermal

insulation of the thickness of 10 cm covered with a

corrugated sheet, up to the value of 4.37 W/m2K for

the roof of the Faculty of Dentistry as a pitched roof

Min Average Max. Min Average Max. Kosova Norway Finland

Before After Regulation / codes

W/M2K

U values for doors

Clay tiles Metal sheet Asbestos Bitumen tiles Flat roof Total

Type of roof covers

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covered with corrugated metal sheet without thermal

insulation.

In school buildings, similar to findings from

different studies [19], different U-values have been

identified depending on the type of construction and

the period of construction, and they vary from 1.1

W/m2K for roofs with the construction plate

"Avramenko", to 2.04 W/m2K, 1.1 W/m2K for the

"Monta" construction, and values of 3.3–4.0 W/m2K

for structural concrete slabs without thermal

insulation and with an average U-value for school

roofs of 2.6 W/m2K.

Based on the recommendations from the Kosovo

Technical Regulation, the buildings were designed

so, that the U-value of the roofs after the

implementation of the EE measures should be <0.7

W/m2K! In all public buildings, this objective has

been achieved, moreover, in 17 public buildings, it

reaches the lowest value of 0.36 W/m2K for

reconstructed objects and up to 0.60 W/m2K for the

roofs without EE measures.

After the implementation of EE measures in most of

the school buildings, the U-value has been improved

up to 0.2 W/m2K, except in cases where the roofs

have met the criteria according to the Kosovo

Technical Regulation. The table below shows

significant differences between some achieved U

values after implementation of EE measures and

recommended U values by Technical Regulation,

and is very similar to the U values from EU states’

building codes. This indicates the necessity for

improving the building codes impacting directly

buildings’ energy efficiency. The achieved U-values

after a complete renovation and/or for new roof

constructions were between 0.17-0.2 W/m2K, much

lower than recommended by Kosovo Technical

Regulation and very similar to Finish and

Norwegian Building Codes.

Table 6. U-values for roofs- before and after implementation of the EE measures and compared with standards

Description

U-values

before the

measures

[W/m2K]

U-values

before the

measures

[W/m2K]

U-values

after the

measures

[W/m2K]

U – values

according to

Kosovo

Technical

Regulation

[W/m2K]

U – values

according

to the

2017

Finish

building

code

[W/m2K]

U – values

according to

the 2017

Norwegian

building

code

[W/m2K]

17 public buildings in total

1.47-4.37

≤ 0.7

≤ 0.18

≤ 0.13

3-without implemented EE

measures

0.39-0.60

14- Completely repaired

1.47-4.37

0.20

53 school buildings in total

0.4-3.80

≤ 0.7

≤ 0.18

≤ 0.13

3–without implemented EE

measures

0.4-0.5

43-complete renovation

0.17

30–Complete new

0.20

Through detailed analysis of the collected U-values

data for roofs in all 70 public buildings, these new

and partially repaired, we have concluded that there

is sufficient space for improvements and it is a

highly recommended change of existing criteria and

at least application of the values from Finish

building code. With this change, potential energy

savings in part of roof covers might be 44.24%.

The following diagram in Fig. 6 clearly describes

the average U-values of roofs in public buildings

before and after implemented EE measures,

compared with Kosovo Regulation and two EU

states’ codes [6,10,17,18].

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Fig. 6: U-values for roofs for all analysed public buildings

2.5 Floors

In many of reports of the International Energy

Agency and studies related to the energy

performance of buildings [3,12] it is confirmed that

floors as a constructive part of the building, can be a

great source of energy savings as part of the

building envelope. Qualitative and careful insulation

of the floors in public buildings can significantly

affect thermal energy savings. Floors can be

designed in different ways and techniques: as

concrete slabs and prefabricated slabs on typical

floors, somewhere there were raised floors where

cables and technical equipment are placed, and

concrete floor monolith connected with walls, which

is usual in basements. These types of constructions

were the basis for applying the final floor layers for

floors in schools and public buildings to increase

their thermal performance. In schools, we found

damaged wood flooring, hardwood flooring on

gymnasium floors, and ceramic tiles in corridors and

sanitary parts of buildings, while in public buildings

situation was improved with better quality floors

from laminated wood, Vinyl Composition Tiles

(VCT), linoleum and sometimes even covered with

carpets. The problem of humidity is a very sensitive

issue that should be handled more carefully. On the

floors of public buildings, significant deficiencies

were observed in terms of thermal insulation and

finishing materials. Despite these remarks, for

financial reasons, the implementation of EE

measures for floors has not been recommended for

most buildings. Therefore, the U-values before and

after the EE measures in most of the 17 public

buildings are still far from the criteria defined by the

Technical Regulation and European norms,

especially compared to the codes of European

countries. The weak structural details were the

connections between the finishes and angles of the

floors and the external vertical walls which were

usually presented as thermal bridges.

The U-values in these public buildings, before the

implementation of the EE measures, ranged between

0.63-0.91[W/m2K], while in most of the buildings,

they remained the same after the implementation of

the measures and in the range between 0.55-2.91

[W/m2K] even though the values of recommended

according to the Kosovo Technical Regulation were

<0.65 [W/m2K].

In the school buildings, the U-values before EE

measures, varied between 1.0 – 2.3 [W/m2K],

depending on the structure of the floor layers. In 25

schools, the new floor has been installed, but only in

12 of them, the thermal insulation has been

extended. The U-value of these floors before the EE

measures was 1.72-2.3 [W/m2K], while after the

implementation of the EE measures these values

reached values 0.93-0.96 [W/m2K].

More than 42 public buildings were left without EE

measures on floors because of a lack of investments.

Our internal analysis for both public buildings and

schools has shown the need for both technical and

economic analysis when a decision for EE measures

for floor refurbishment is required. The solution

should be feasible and the Finish building code is

quite rigid.

0,5

1,5

2,5

3,5

4,5

Min Average Max. Min Average Max. Kosova Norway Finland

Before After Regulation / codes

W/M2K

U values for roofs

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Table 7. U-values for floors- before and after implementation of the EE measures and compared with standards

Description

U-values

before the EE

measures

[W/m2K]

U-values

before the EE

measures

[W/m2K]

U-values

after the EE

measures

[W/m2K]

U – values

according to

the Kosovo

Technical

Regulation

[W/m2K]

U – values

according to

the 2017

Finish

building code

[W/m2K]

U – values

according to the

2017 Norwegian

building code

[W/m2K]

17 public buildings in total

≤ 0.7

≤ 0.18

≤ 0.10

14- without implemented EE measures

0.63-2.91

2- Finalized floor with thermal

insulation

1.21-2.97

0.54-0.57

53 school buildings in total

≤ 0.7

≤ 0.18

≤ 0.10

28-without EE measures

1.0-2.30

1.0-2.3

13–New PVC floor without thermal

insulation

2.3

2.1

7- New PVC floor with thermal

insulation

1.72-2.3

0.93-0.96

The following diagram in Fig.7 describes the

average U-values of floors in public buildings

before and after implemented EE measures,

compared with Kosovo Regulation and two EU

states’ codes.

Fig. 7: U-values for floors for all analysed public buildings

3 Conclusion

Findings from this study project, undoubtedly show

that, both from the early design phase and from the

phase of later building main renovations, energy

savings can be greatly influenced by the correct

design of the building envelope and the proper

selection of building envelope materials with low U

values. This suggests a necessity for significant

review and strengthening of actual building codes

and regulations in Kosovo. This approach must be

holistic, especially related to the Kosovo Technical

Regulation on Thermal Energy Saving and Thermal

Protection in Buildings, reviewing not only actual

recommended U-values, but also new building

requirements which should be in line with

requirements that since 2021, all new buildings must

be nearly zero-energy buildings (NZEB) and since

2019, all new public buildings should be NZEB. In

this context, to produce comparable evaluation

values, the standard input data for climate, building

and thermal comfort should be provided in detail in

future building codes.

It is confirmed that after the implementation of the

EE measures, the U-values of all building envelope

elements, external walls, windows, doors, roofs and

floors have changed inherently way and with this,

0,5

1,5

2,5

3,5

Min Average Max. Min Average Max. Kosova Norway Finland

Before After Regulation / codes

W/M2K

U values for floors

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the consumption of thermal energy has also been

proportionally reduced. In some cases, much lower

values are reached compared with the Kosovo

Technical Regulation and/or recommended values

by ANA_IAE (The Eurima Ecofys VII study 2007).

Our findings suggest a potential for more

demanding energy performance criteria in the

Kosovo building code and regulations. To achieve

this goal, it is recommended to consult building

codes and regulations of neighbouring countries,

because as we presented in this paper, EU countries,

in our case Finnish and Norwegian building codes

have relatively very strict requirements on the

energy performance of the building envelope.

Achieved U-values for external walls, after

implementation has changed essentially, and are

close to the EU standards and much better than

Kosovo Regulation, but the thickness of the thermal

insulation needs to optimize depending on the type

and thickness of the external wall.

U-values for windows and doors for all 70 public

buildings after implementation of EE measures are

compared with EU standards and we have

concluded that is more than required strengthening

of requirements in future Kosovo Building code

reducing the U-values for doors and windows at 0.8

W/m2K.

Although investments in the implementation of

measures for roofs have been limited, we have

concluded that there is sufficient space for

improvements and it is a highly recommended

change of existing criteria and at least application of

the values from the Finish building code. With this

change, potential energy savings in part of roof

covers might be 44.24%.

The achieved U-values after a complete renovation

and/or for new roof constructions were between

0.17-0.2 W/m2K, much lower than recommended

by Kosovo Technical Regulation and very similar to

Finish and Norwegian Building Codes.

Contrary to the importance of EE measures impact,

the investment on public buildings floor remained

the weakest part of the project, because of a lack of

investments. It is highly recommended that in future

studies this part of the building envelope should be

seriously improved and U-values changed to be

close to the EU standards.

Presented results in tables and diagrams show great

potential for energy savings through the

strengthening of criteria for U-values in future

technical regulation and Building codes and are very

useful for practical applicability for designers and

building constructors. Implementation of these new

criteria will significantly improve energy savings

and increase construction quality reducing building

system energy costs.

Decreasing the U-values in a technically and

economically feasible way for all building envelope

elements will significantly impact reducing of

overall energy consumption in public buildings.

Results from our study show an energy reduction

from 56.74% for the overall consumption of 70

public buildings and schools in Kosovo, reducing

proportionally CO2 emissions through more

strengthening of the building codes and in alignment

with international standards.

Presented findings are done for a limited number

and types of public buildings, and taking into

account that we in KEEA (Kosovo Energy

Efficiency Agency) and KEEF (Kosovo Energy

Efficiency Fund), in recent years, have implemented

EE measures in hundreds of public buildings, it is

highly recommended to made new holistic studies

which may include other building typologies and

may disclose additional differences between the

energy performance criteria in the analysed building

codes.

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

The authors equally contributed in the present

research, at all stages from the formulation of the

problem to the final findings and solution.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

No funding was received for conducting this study.

Conflict of Interest

The authors have no conflicts of interest to declare

that are relevant to the content of this article.

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(Attribution 4.0 International, CC BY 4.0)

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