FACULTY OF ENGINEERING AND SUSTAINABLE DEVELOPMENT
Department of Building Engineering, Energy Systems and Sustainability Science
Meghdeepa Choudhury
2020
Student thesis, Advanced level (Master degree, two years), 30 HE Energy Systems
Master Programme in Energy Systems
Supervisor: Alan Kabanshi Assistant supervisor: Arman Ameen
Examiner: Abolfazl Hayati
Pre-renovation considerations for a Swedish single-family house
Analysis of energy saving potential
i
Preface
I remain indebted to the Almighty to have bestowed upon me all the opportunities which led me to be the person I have become today, for all the energy in me to withstand the obstacles I faced throughout this short journey of my life. I am thankful to my in-laws who have granted me every keys to access higher education. I remain obliged to all the wonderful teachers and supervisors I came across starting from my school days who have constantly tried to guide me through the right track.
My report was revised until it reached perfections by my respected examiner Abolfal Hayati for which I remain indebted to him. I would like to thank my supervisor Alan Kabanshi who has given me an opportunity to work in this interesting project, allowed me the freedom to express my opinions and also provided me with reference paper to ease my thesis job. From the writing of the research proposal to the smallest details in the thesis work, his guidance has been remarkable. I also remain thankful to my co-supervisor Arman Ameen who has helped me with the IDA ICE software. Thanks to his wonderful and easy to learn YouTube tutorials which have enabled me to design the building model step by step. Finally, I would like to express my gratitude towards the department of Energy systems where international students like me are welcome to enhance their knowledge on energy systems with emphasis on sustainable development.
ii Abstract
According to United Nations 7th sustainable development goal, increased use of fossil fuels in energy accounts for around 60 percent of total global greenhouse gas emissions and in order to debacle this crisis of global warming, the European Union aimed to reduce energy use by 32.5 % within 2030 by improving energy efficiency. Whereas, the Swedish energy goals include reducing energy use by 50% in 2030 compared to 2005 and at producing 100% electricity from renewable sources by the year 2040. In the year 2018, the housing and service sector contributed to 40 per cent of the total final energy use in Sweden according to energimyndigheten. For this reason, energy conservation in the residential sector is given a priority. Furthermore, the emissions from old houses are much higher compared to that of newly built homes, which demonstrates higher scope of introducing energy efficient renovation measures in Swedish buildings. During the year 1965 to 1976, there was an enormous construction work to build up single family housing areas in Sweden under the million homes program which are now in need of renovation. Therefore, an old single-family villa from million homes program was selected for the purpose of energy efficient renovation.
There are different environmental certification systems to assess energy performance of a building which are commonly expressed in terms of kWh/m2 and year. Among them, the seven energy classes from A to G was chosen for building rating in this project. The aim was to improve the current energy rating of the house from D without compromising the indoor air quality and cost effectiveness. At the same time, objective was also set to increase the amount of green energy as fuel for electricity production in the building. At first, a literature review was performed to observe the renovation strategies previously applied in similar projects. A study of the construction used for the million homes villas was also conducted to assess the original construction of the reference villa in Valbo. The research was conducted with the help of energy simulation software IDA ICE and LCC software BELOK Totaltool. The theory behind the application of these software in this project was analyzed in the beginning. Then, the building model was created with the help of building floor plan. The input parameters were set according to the standards of FEBY and Boverket regulations. After forming a base model for the existing construction of the building, different sensitivity analyses were performed with various renovation measures for one month or for one year. The results obtained from the sensitivity analysis helped in choosing the most energy efficient measures for renovation. Then the economic analysis of the model was conducted to investigate the most cost-effective measures. Later on, these expensive measures were omitted from the renovation plan to yield both energy efficient and cost-effective renovation of the villa. Next, the indoor air quality and green footprint in the building were compared before and after renovations. The results indicated that, it was possible to maintain good indoor air quality and increase green energy footprint in the building when the building rating was changed from D to B. In the end, the simulation results were compared with that of the literature review. It was found that both the qualitative and quantitative results have common realizations. Overall, it was possible to reduce the energy consumption in the house by 46.82%.
Key-words: Renovation measures; Million homes program; Single family houses; Pre- renovation consideration; IDA ICE; Cost effective; Green footprint in building; Indoor air quality; 1.5 storey villa
iii Nomenclature
Symbol Description Units
Eheaing Energy needed for space heating kWh
Qtotal Total heat losses kW
DH Heating degree hours during 1 year hour
EDHW Annual use of DHU kWh
EHWC Annual losses from circulation of hot water kWh
u Heat transfer coefficient W/m2.K
U Overall heat transfer coefficient W/m2.K
A Area of the building part m2
ɳ Efficiency (%)
q Air flow m3/s
ρ Density Kg/m3
Cp Specific heat capacity J/kg. K
a Annual precipitating SEK
ri Internal rate of interest %
n Number of years years
Bo Initial investment SEK
RH Relative humidity %
q Annual price increase %
Atemp Heated floor area of a building (greater than 10°C) m2
A0 Present value of annual precipitating amount SEK
iv
Abbreviation Description
IEA International Energy Agency
UN United Nations
IPCC Intergovernmental Panel on Climate Change
WBSD World Building council for Sustainable development BELOK Energimyndighetens beställargrupp för lokder
LED Light Emitting Diode
COP Coefficient of performance
LEED Leadership in Energy & Environmental Design
EP Energy Performance
BBR Boverkets byggregler
SVEBY Standardized and Verified Energy performance in buildings
MP Million Homes program
IDA ICE IDA Indoor Climate and Energy
DHW Domestic Hot Water
HWC Hot Water Circulation
IHG Internal Heat Gain
KPR Kapprum (cloakroom)
WC Water Closet
KLK Klädkammare (walk-in-closet)
GSBL G, LB
Ground Source Borehole Loop Wardrobes
v
List of figures
Figure 1: Final energy use in the residential and service sector TWh, 2017 (Source:
International Energy Agency). ... 1
Figure 2 Identification of Million homes program (Source: Kempen et.al, 2005) ... 3
Figure 3: Single family houses of 1970s built on flat land (Source: Så byggdes Villan: villaarkitektur från 1890 till 2010. ... 4
Figure 4: Sketch of Valbo villa ... 5
Figure 5: Floor plan of ground floor ... 6
Figure 6: Floor plan of upper floor ... 6
Figure 7: System boundary of delivered energy. Source: Virtanen et al. ... 10
Figure 8: Side view of the building body ... 14
Figure 9: Front view of the building body ... 15
Figure 10: Building model with solar installations ... 17
Figure 11: Flow chart of renovation method ... 18
Figure 12: Sectors incurring loss in the building ... 21
Figure 13: Sensitivity analysis for windows ... 22
Figure 14: Energy requirement for different shadings ... 22
Figure 15: Sensitivity analysis with drop arm awning and markisolette ... 23
Figure 16: Sensitivity analysis with doors ... 23
Figure 17: Sensitivity analysis with roof types ... 24
Figure 18: Sensitivity analysis with different wall constructions ... 24
Figure 19: Sensitivity analysis with internal floors and slabs ... 25
Figure 20: Sensitivity analysis with different VAV systems ... 25
Figure 21: Sensitivity analysis with thermal bridges ... 26
Figure 22: Sensitivity analysis with AHU components... 26
Figure 23: Sensitivity analysis of different heat pumps ... 27
Figure 24: Sensitivity analysis of Solar PV system ... 28
Figure 25: Basic components of solar thermal system. Source: EIA (2019) ... 28
Figure 26: Sensitivity analysis with Solar thermal system with and without storage tank ... 29
Figure 27: Sensitivity analysis of different combinations with heat pump ... 29
Figure 28: Sensitivity analysis with occupancy ... 30
Figure 29: LCC of measures ... 32
Figure 30: IRR graph ... 33
Figure 31: Delivered energy overview before renovation ... 36
Figure 32: Delivered energy overview after renovation ... 37
Figure 33: individual impact on electric heat by different renovation measures ... 38
List of tables Table 1: Energy classification for buildings ... 2
Table 2: Recommended specific energy use for new buildings ... 3
Table 3: Construction pattern of 1970 houses ... 4
Table 4: Specifications of the house ... 5
Table 5: Most profitable renovation measures ... 8
Table 6: U values of building parts used for base model ... 16
Table 7: Calculated energy efficiency of the house before and after renovation ... 31
Table 8: Mean air age of the building before and after renovation ... 34
Table 9: Amount of carbondioxide in different zones before and after renovation ... 35
Table 10: Relative humidity of different zones before and after renovation ... 35
vi
Table of contents
1. Introduction ... 1
1.1. Background………...……..……….1
1.2. The literature review………..…….……….7
1.3. The Aim………..……….………8
2. Theory ... 10
2.1. Energy balance in buildings………..……….10
2.2. Energy performance of buildings……….………..11
2.3. Cost effectiveness……….………..12
3. Methods ... 14
3.1. Simulation………..14
3.1.1. Simulation of the base model...…...15
3.1.2. Simulation of the renovated building………17
3.2. Economic analysis and energy performance……….………….18
3.2.1. Economic analysis……….………18
3.2.2. Energy performance of the building……….……….……19
3.3. Limitations……….…………....19
4. Results ... 21
4.1. Analysis of the base model ………..….…….21
4.2. Sensitivity analysis……….…………30
4.3. Implementation and analysis of feasible renovation measures……….……….…30
4.3.1. Energy rating and economic analysis………31
4.3.2. Indoor air quality……….……..33
4.3.3. Green footprint……….….…35
5. Discussion………37
6. Conclusions………..………40
Reference………...41 Appendix A ... A1 Appendix B ... C1 Appendix C ... C1 Appendix D,E,F ... F1
1
1 Introduction
1.1.The background
Today’s energy world is proceeding towards a new historic revolution when the requirement for clean and low carbon energy has become inevitable. According to the United Nations, energy accounts for around 60 per cent of total global greenhouse gas emissions and thus contribute to climate change. In order to debacle this crisis of global warming, it is necessary to lower the overall nonrenewable energy consumption in the world.
The European Union goals were aimed to reduce energy use by 20 % within the year 2020 and by 32.5 % within 2030 by improving energy efficiency. Out of the total share of final energy use, renewable energy sources should hold 20% and 32% within years 2020 and 2030 respectively.
Whereas, the Swedish energy goals include reducing energy use by 20% in 2020 compared to 2018 and 50% in 2030 compared to 2005. By the year 2040 Sweden aims at producing 100% electricity from renewable sources (Swedish Energy Agency 2019).
The present trend in growing energy demand shows a significant rise in building energy use around the world (BP, 2020). The UN (2019) has reported that “the buildings and construction sector accounted for 36% of final energy use and 39% of energy and process-related carbon dioxide (CO2) emissions in 2018”. In the year 2018, Sweden had a total final energy use of 373 TWh of which, the housing and service sector contributed to147 TWh, which corresponds to just under 40 per cent of the total final energy use (energimyndigheten, 2019). According to the report of International Energy Agency 2018, in the residential sector, space and water heating accounts for 70% of the total energy consumption and the rest is consumed by household appliances, lighting and cooking. Fig.1 shows most of the energy in residential and service sector is utilized in required electricity. “The growth in the number of buildings and services has been offset by the improved energy efficiency in buildings and heating systems, which has stabilized total consumption”-IEA (2019).
Figure 1 Final energy use in the residential and service sector in Sweden TWh, 2017 (Source: The Swedish Energy Agency).
2
A newly built home emits 0.86 tons per year, whereas, the old house produces an average of 1.6 tons per year (IPCC, 2007). According to WBSD (2007), single family residences use more energy compared to multifamily houses in developed countries. Bhattacharjee (2016) found that “the single- family residences built during the “Million Program” and earlier has higher energy consumption per square meter area in comparison with new buildings”. Moreover, occupant’s thermal comfort is worse in older homes than in newly built homes. This poor indoor environment also causes health problems to the residents. In order to address such problems, it is convenient either to replace an old home to a new one or renovate it. Power (2008) has suggested that renovation would be one better option than demolition since demolition of old houses increase the risk of CO2 emission.
Bhattacharjee (2016) showed that in adopting energy efficient strategies for renovation of houses, cost-effectiveness puts higher impact on house-owner’s preferences.
According to the National Board of Housing, Building and Planning, there are different environmental certification systems to assess energy performance of a building. At present, these are being administered by two organizations, namely: Swedish Green Building Council and Swan Ecolabel. The two most common certification systems include LEED (recognized internationally) and Miljöbyggnad (used at a national level). Energy performance is expressed in terms of the unit kWh/m2 and year.
In the year 2014, energy classification was introduced in the certification in order to easily compare the energy consumption of different buildings. There are seven energy classes from A to G which determine the energy performance measures of the building in question. The classification criteria can be found in the table below.
Table 1: Energy classification for buildings Energy classes from A to G
A EP is ≤ 50 percent of the requirement for a new building.
B EP is > 50 - ≤ 75 percent of the requirement for a new building.
C EP is > 75 - ≤ 100 percent of the requirement for a new building.
D EP is > 100 - ≤ 135 percent of the requirement for a new building.
E EP is > 135 - ≤ 180 percent of the requirement for a new building.
F EP is > 180 - ≤ 235 percent of the requirement for a new building.
G EP is > 235 percent of the requirement for a new building
The requirement for a new building has been defined in the BBR as Buildings specific energy use.
It is the ratio between the building’s energy use (purchased energy supplied to a building for heating, comfort cooling, hot tap water and the buildings property energy) to the area enclosed by the inside of the building envelope of all storeys including cellars and attics for temperature-controlled spaces, intended to be heated to more than 10 ºC. For dwellings with electric heating, BBR has determined different values of specific energy use on the basis of three different climate zones in Sweden as indicated in the table below.
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Table 2: Recommended specific energy use for new buildings
Climate zone I.
(Counties of Norrbotten, Västerbotten,
Jämtland.)
II.
(Counties of Västernorrland, Gävleborg, Dalarna
and Värmland.)
III.
(Counties of Västra Götaland, Jönköping, Kronoberg, Kalmar, Östergötland, Södermanland, Örebro, Västmanland, Stockholm, Uppsala, Skåne,
Halland, Blekinge and Gotland.) The building’s
specific energy use [kWh per m2 Atemp and year]
95 75 55
The EP value found in the energy classification is known as primary energy number. In the words of Gustafsson et.al, (2017):
“In the European Union’s Energy Performance of Buildings Directive, the energy efficiency goal for buildings is set in terms of primary energy use. In the proposal from the National Board of Housing, Building, and Planning, for nearly zero energy buildings in Sweden, the use of primary energy is expressed as a primary energy number calculated with given primary energy factors.”
According to the Swedish Research Council Formas (2011), a Delegation for Sustainable cities was set up by the Government in 2008, which included several projects, among which, the Million Homes Program (MP) was in charge of transforming the existing townships, particularly those developed during the 1960s and 1970s. Those buildings were called The People´s Home that came into being as the result of a combination of political will, functionalist and modernistic ideas for architecture. The primary purpose was that the citizens should have the right to good dwelling at a low price.
Figure 2 Identification of Million homes program (Source: Kempen et.al, 2005)
The figure above shows the number of inhabitants per neighborhood type in the year 2000.
Currently, such homes constitute one third of Sweden´s present building stock and most of them are now in need of renovation with increased energy efficiency. It can be seen that during the year 1965 to 1976, there was an enormous construction work to build up single family housing areas.
4
Figure 3: Single family houses of 1970s built on flat land (Source: Så byggdes Villan:
villaarkitektur från 1890 till 2010.
The figure above shows some examples of villas designed during the 1970s. The construction of such villas followed almost some common features. Following are the features of villas forms during the period 1971 to 1980 as demonstrated by Ekström and Blomsterberg (2016).
Table 3: Construction pattern of 1970 houses
➢ Number of storeys One and a half storey house
➢ Angle of roof Ridged roof inclined to 45° angle
➢ Roof construction Made up of roof trusses with intermediate insulation
➢ Wall construction Stud framework, intermediate thermal insulation and plastic vapor barrier
➢ Eaves Sharply projecting eaves
➢ Balcony On gable side of the house
➢ Façade structure Facades made up of bricks on ground floor and wood panel on upper floor
➢ Ventilation system Ventilation system changed from passive stack in the beginning to mechanical ventilation
The process of renovation is much more complicated and riskier than new construction in terms of decision making, planning and execution. Housing owners face a task which is urgent and highly complex in terms of meeting regulation and demand (energy, conservation, accessibility, or tenants
‘participation), economic return of investment, safeguarding social values and creating long-term sustainability (Thuvander et al., 2013). Hence, some pre-renovation considerations must be made through research to help the house owners make the convenient decisions. In the words of Karin et al., (2015):
“Particularly regarding renovation of buildings, where interdisciplinary is important but also creates constrains, there is an urgent need of a comprehensive knowledge base and quality model taking into account research and practical experience.”
Reference building:
The house of interest, a single-family house located in Valbo (Gävle), is part of the building stock that was built in 1976 and was lastly renovated in 2005. It has an energy efficiency rating of D. The
5
heating demands of the house (domestic hot water and space heating) are covered by direct electricity and has an annual energy use of 132.12 kWh/ (year.m2).
Figure 4: Sketch of Valbo villa
The figure above shows a simple sketch of the side view of the building scaled 1:100 where the roof is tiled by angle of 45 degrees. The detailed specifications of the building can be found in the table below.
Table 4: Specifications of the house Criteria Specifications
Building type Detached house
Number of storeys 1.5
Year of construction 1976
Year of renovation 2005
Manufacturing company Faluhus AB
Latitude 60.64492
Longitude 17.01613
Orientation 45°
Street address Trädgårdsvägen 8, Valbo, Gävle
Country Gävleborg, Sweden
Although most of the houses from million homes program were naturally ventilated, the ventilation system used in this villa was mechanical ventilation with heat recovery. The ground floor of the villa consisted of seven rooms with attached forråd and bastu. Some openings without doors can also be found between different rooms. There is also one staircase inside the building connecting the ground floor with the upper floor.
6
Figure 5: Floor plan of ground floor
Figure 6: Floor plan of upper floor
As seen on the figures above, the upper floor 6 rooms including three bedrooms. The ventilated air is supplied to Sovrum3 and exhaust air is drawn from the WC. There is one balcony in the north- west direction. The length and width of the rooms as well as of the doors and windows have been verified through actual measurements in the building. There was visibly no gap between the ground floor and the ground. The heights of the ground floor and the upper floor were 2.6 and 2.4 respectively. The demand for space heating and domestic hot water were induced by the location and climate condition. However, the total floor area of the building was not the same as the total heated floor area of the building.
The aim for the research was to determine the pre-renovation considerations for this villa by determining the total energy used and total energy delivered to the heated floor area of the building.
This research work associated will open the door to find out the best alternatives for its energy efficient, environment friendly, thermally comfortable and cost-efficient renovation which will in turn enable its owner to undertake suitable decisions on whether it would be profitable for him to renovate the house or not. There will be one good opportunity to explore and apply the findings from different similar research works.
7 1.2.The literature review
Ekström and Blomsterberg (2016) have performed energy simulations for four single family houses from different parts of Sweden that were in need of renovation. The results from their investigation revealed that it is not possible to reach a passive house standard after renovation by using today’s technology as the shape, composition and foundation of the building envelope impose limiting factors on energy renovation. About 65 to 75% reduction in end use of energy was however achievable through their renovation measures. Ekström et al., (2017) then carried out research on the cost analyses. In their report, they have mentioned that the renovation measure of installing an exhaust heat pump was the most cost-effective. They have also recommended the passive house renovation package especially for the houses using direct electric heating as it would yield the most cost effectiveness.
By using actual installations and taking physical measurements, Bernando et al., (2016) showed that converting an existing domestic hot water heater to a solar domestic hot water system in a single- family house of south Sweden can result in a saving of 50% domestic hot water consumption with the return on investment in 17 years. Uriate et al., (2019) showed the influence of vacuum insulation panels on the energy efficient retrofitting of buildings. Brom et al., (2018) found that renovation of single-family houses frequently resulted in lower energy savings when the building envelope insulation is improved. Wang et al., (2015) combined low-temperature heating with all energy demand retrofitting as a package to achieve 55.3% and 52.8% total delivered and primary energy savings, respectively. In this way, different authors have come into different conclusions after conducting their own method of investigations regarding energy efficient renovation of houses.
Besides, according to the literature review performed by Karin et al., (2015), among all publications appearing under “sustainable renovation, the aspect of energy was included in 70 %, economic aspects were treated in 45 % while aspects such as thermal climate and ecologic appeared in less than 20%. Power (2008) showed that perceived thermal comfort level of occupants was not satisfactory after building renovations.
Bonakdar (2017) studied optimal and cost-effective energy renovation of single-family houses in Swedish building stock in which he concluded the following:
❖ For the houses of 1970, renovation measures can reduce the space heat demand up to 28 % in climate zone 1 and up to 25 % in zone 4.
❖ Renovation of the houses built during early 1970s appears to be the more cost-effective compared to 1980s.
❖ Cost-effectiveness is not achieved through the renovation of exterior walls and windows, regardless of the year of construction.
Lucon et.al., (2014) have come across some generalizations from numerous case studies of individual retrofit projects as reviewed in Harvey (2013). Some important ones of these are as follows:
❖ For detached single family homes, the most comprehensive retrofit packages have achieved reductions in total energy use by 50–75%;
❖ In multi-family housing (such as apartment blocks), a number of projects have achieved reductions in space heating requirements by 80–90%, approaching, in many cases, the Passive House standard for new buildings;
❖ In commercial buildings, savings in total HVAC energy use achieved through upgrades to equipment and control systems, but without changing the building envelope, are typically on the order of 25–50%;
❖ Eventual re-cladding of building façades—especially when the existing façade is largely glass with a high solar heat gain coefficient, no external shading, and no provision for passive ventilation, and cooling—offers an opportunity for yet further significant savings in HVAC energy use; and
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❖ Lighting retrofits of commercial buildings in the early 2000s typically achieved a 30–60%
energy savings (Bertoldi and Ciugudeanu, 2005).
A research had been conducted by Levine et al (2017) on the carbon dioxide emission reduction potential for residential commercial sectors considering global renovation records. Some of the important findings from the research include renovation measures with highest potential and a list of cost-effective measures which are given in the table below.
Table 5: Most profitable renovation measures
Measures with lowest costs Measures with highest potential
Increase in solar energy use Heat insulation, insulation improvement, new insulation, windows, wall, shell esp., attic, roof and post insulation
Roof, wall and floor insulation/New insulation, Attic insulation/insulation improvement
BEMS for space heating and cooling Energy star equipment, MEPs for appliances 1999,
Efficient TV and peripheries, Efficient refrigerators and freezers, efficient chest freezers, efficient dishwashers
Heating system fuel switching to gas, solar, biomass, use of District heating and CHP
Standby programs, TVs on mode Retrofit of windows, replacement of windows, window replacement, 3D window glass
New lighting systems, lighting retrofit, lighting best practice
Fluorescent lamps, improved lights, bulbs and appliances
Electricity and gas water heater Improvement of home appliances. Efficient- refrigerators, electric water heater, ceiling fan, AC Individual metering of hot water/water flow
controllers
New HVAC systems
Retrofitted windows, 3D window glass Solar energy use increase, hybrid solar water heaters Electricity demand reductions
Commercial landfill gas Furnaces and shell improvements Ballast program in 2003 Improved building design New building thermal design
Levine et.al., (2017) concluded that “CO2- saving options are largest from fuel use in developed countries and countries in transition due to their more northern locations and, thus, larger potential for heat-saving measures. They added that “efficient lighting technologies are among the most promising measures in buildings, in terms of both cost-effectiveness and size of potential savings in almost all countries”.
1.3.The aim
The thesis project aims at evaluating the theoretical energy savings potential of the house by exploring different energy related measures. The results will increase an understanding of cost- effective options that the building owner can undertake during renovations.
The overall purpose of this study can be subdivided into the following individual objectives.
• Ensure better heating and cooling system and better indoor climate within the house
• Increase the green energy footprint in the building
• Make the renovation cost-effective and
• Improve the efficiency rating of the building
9
The research question addressed in this study was: How is it possible to renovate an old villa to an energy effective building without compromising the indoor environment for occupants and affordability of the house owner?
However, this study was based on different assumptions regarding the actual construction of the building since most of the information regarding the villa in Valbo were collected from similar villas from million homes program. Furthermore, the pre-renovation assumptions regarding occupants clothing, activity level and use of the household appliances could widely differ from the actual scenario after renovations. These facts can cause discrepancies in the results of this study.
The research was conducted based on both qualitative and quantitative approaches. The qualitative approach basically included the literature review and result analysis. Whereas, the quantitative approach included different calculations related to energy simulation and optimization. For the simulation purpose, IDA ICE software was used and for the economic analysis, the Belok Totaltool version 2 was used.
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2. Theory
2.1. Energy balance in buildings
Energy can never be created nor be destroyed. It can only be transferred from one form to another.
Energy balances can only be prepared for restricted spatial areas with clearly defined boundaries.
These boundaries are called the envelope. For buildings, it is called the building envelope. Energy is supplied to buildings in order to achieve a comfortable indoor temperature, to supply domestic hot water and for different operational functions. The heat demand for DHW depends on the amount of hot water used. Whereas, the space heating demand is depending on the varying outdoor temperature, internal heat gain through clothing and metabolism of the occupants, lighting and equipment and different heat losses from the envelope.
Figure 7 System boundary of delivered energy. Source: Virtanen et al.
According to Fleur (2019), the energy balance of a building can be illustrated as follows.
Heat demand: Additional supply of heat is required to compensate for heat losses from the building envelope. A portion of the heat demand is covered by IHGs in the building, that is, from people, appliances and solar radiation. The remaining needs to be supplied from the building’s space heating system. This space heating, Eheating (kWh), can be defined using Equation ⦋i⦌.
𝐸ℎ𝑒𝑎𝑡𝑖𝑛𝑔 = 𝑄𝑡𝑜𝑡𝑎𝑙 × 𝐷𝐻 + 𝐸𝐷𝐻𝑊 + 𝐸𝐻𝑊𝐶 ……….⦋i⦌.
In this equation, Qtotal in kW stands for total heat losses, DH means the heating degree hours during one year (°Ch), EDHW is the annual use of DHW usually expressed in kWh and EHWC denotes the annual heat losses from circulation of hot water and expressed in kWh. Here,
𝐷𝐻 = ∑𝑛 ((𝑡𝑏
𝑖=1 − 𝑡𝑜𝑢𝑡𝑖 ) × ∆𝑡) and 𝑡𝑏= tin - 𝑃𝐼𝐻𝐺
𝑄𝑡𝑜𝑡𝑎𝑙
Where, ∆𝑡 is time in hours, tb is balance temperature, tout is outdoor temperature, tin is indoor temperature and 𝑃𝐼𝐻𝐺is the average power from people, equipment and solar heat gains.
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For any changes that are applied to a building, for example, thermal improvements or increase in the number of equipment, the internal heat characteristics get affected and changes in temperature balance also takes place.
Heat losses: Heat losses in buildings occur in three different ways: heat transmission through the building envelope, air exchange from ventilation of the building, and from infiltration through thermal bridges and air leakages. The total heat losses, Qtotal, can be seen in Equation [ii].
𝑄𝑡𝑜𝑡𝑎𝑙 = 𝑄𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 + 𝑄𝑣𝑒𝑛𝑡𝑖𝑎𝑙𝑡𝑖𝑜𝑛 + 𝑄𝑖𝑛𝑓𝑖𝑙𝑡𝑟𝑎𝑡𝑖𝑜𝑛 ………. [ii]
Where Qtransmission implies the losses from transmission of heat through the building envelope via conduction (W/K), Qventilation is the heat loss from ventilation of the building (W/K), and Qinfiltration
means the losses from undesired air leakage in the building envelope (W/K).
The transmission losses are relied on the thermal properties of the building envelope, and are calculated as per Equation [iii].
𝑄𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 = ∑ (𝑈𝑖 × 𝐴𝑖) 𝑛 𝑖=1 ………. [iii]
Where Ui is the overall heat transfer coefficient of a building part (W/m2 ·°C), and Ai is the area of the building part (m2).
With a view to achieving a good indoor air quality, fresh air is to be supplied to the building via natural or mechanical ventilation. The ventilation losses are calculated according to Equation [iv].
𝑄𝑣𝑒𝑛𝑡𝑖𝑎𝑙𝑡𝑖𝑜𝑛 = (1 − 𝜂) × 𝑞𝑣𝑒𝑛𝑡𝑖𝑙𝑎𝑡𝑖𝑜𝑛 × 𝜌 × 𝐶𝑝 ………. [iv]
where η is the efficiency of the ventilation heat recovery, qventilation is the ventilation air flow (m3/s), ρ is the density of air (kg/m3) and Cp is the specific heat capacity of air (J/kg·°C).
Air leakage occurs in the building envelope through gaps, cracks or holes, and is referred to as infiltration which is driven by pressure differences between the inside and outside the building envelope. It may be calculated as follows.
𝑄𝑖𝑛𝑓𝑖𝑙𝑡𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑞𝑖𝑛𝑓𝑖𝑙𝑡𝑟𝑎𝑡𝑖𝑜𝑛 × 𝜌 × 𝐶𝑝 ………. [v]
Where qinfiltration is the infiltration flow (m3/s) induced by wind pressure, temperature difference, or mechanical forces.
2.2. Energy performance of buildings
The buildings energy performance is determined by adding the supplied normal year corrected energy for 12 months for heating, comfort cooling, hot water and facility electricity and then dividing the sum by the temperature area Atemp.
The buildings energy performance is corrected by subtracting the delivered energy for domestic water heating, which is higher than standard use or adding delivered energy for domestic water heating which is lower than standard use. The value of standardized use is specified for dwellings in SVEBY occupant input data for dwellings. For buildings with electric heating only, the formula for PE number as per Feby 2019 is as follows.
𝑃𝐸 𝑛𝑢𝑚𝑏𝑒𝑟 =⦃ (𝐸ℎ𝑒𝑎𝑡/𝐹𝑔𝑒𝑜) +𝐸𝑐𝑜𝑜𝑙,𝑒𝑙+𝐸𝐷𝐻𝑊,𝑒𝑙+𝐸𝑜𝑝,𝑒𝑙⦄∗𝑃𝐸𝑒𝑙
Atemp
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Where,
PE number = Primary energy number (kWh primary energy/m2, year) Eheat, el = Electricity used for space heating (kWh/year)
Ecool,el = Electricity used for cooling (kWh/year)
EDHW,el = Electricity used for domestic hot water (kWh/year) Eop, el = Electricity used for operation of the building (kWh/year) Fgeo = Geographic correction factor (between 0.9 and 1.6)
PEel = Primary energy factor for electricity (kWh primary energy/kWh) Atemp = Heated floor area of building (heated to more than 10 ◦C) (m2)
2.3.Cost effectiveness:
BELOK's Total Project has been focused on reducing the heating needs of buildings through improvements to building components and installation systems. If the property owner meets the requirements of the investment's profitability requirements, the reduction of energy needs become significant. The following is a methodology for selecting actions and the formation of action packages according to Abel, Filipsson & Sundström, (2012).
❖ Internal rate of return: It is calculated in terms of interest rate (ri) that an investment provides. In other words, it is a measure of return on investment. If an investment Bo SEK gives an annual operating cost reduction of a SEK / year, this means actual interest rate or an internal rate of return is 1. This Internal rate of interest is available from:
a = P (ri, n) Bo
Where, P (ri, n) is the annuity factor and a is the annual precipitating amount.
❖ Discount rate: One way of expressing a company's financial requirements for long- term investments is to determine the size of the interest rate, the interest rate to be used in the assessment of profitability. This can be combined with supplementary governing conditions, but the choice of interest rate is perhaps the most basic instrument to secure it with taking into account the conditions of the company necessary investment discipline. One can then either choose a nominal interest rate, i.e., an interest that does not take into account inflation, or a real interest rate, i.e., a rate that is cleared from its average inflation.
❖ Future relative changes in energy prices: It is reasonable to assume that precisely the energy prices will still rise above average inflation, which should be taken into account when assessing the cost-effectiveness of energy-related measures. Assuming that the annual energy price increase will be q% above the average. The price change applies:
𝑃(𝑟, 𝑞, 𝑛) = a Ao
Where P (r, q, n) is an annuity factor, which also includes a relative price change, a is the annual precipitating amount and Ao is the average inflation.
❖ Impact of useful life: Different energy management measures may have a shorter or longer service life, depending on what it is for action. The service life indicates how many years the operation works purely technically. The useful life is usually chosen shorter than the life, by the advent of new technology, there will be changes due to the change of tenants etc., which leads to especially installations may be replaced before they are worn out. At a given investment with a given return increases the internal rate with the useful life.
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❖ Action package: The basis for decision making for profitability-based long-term investments should normally be deleted from a calculation according to a capital value method, i.e., present value method, annual cost method or internal interest rate method according to the manual of Belok Totaltool. All of these mean that the investment is weighed against the future revenue or cost reductions. Regardless of which of the methods is applied the same result is obtained, provided that all output data is the same and the calculation is performed in a correct way. BELOK's Total Project is based on the internal interest rate (IRR) method. Thus, internal interest rate charts can be used for reporting of energy analysis.
The overall project model briefly means the following:
▪ A thorough inventory is made in the building to be energy efficient conceivable energy saving measures, of which a package of measures is formed as in its whole meets the property owner's profitability requirements.
▪ The entire package of measures is implemented in the current building
▪ As experience feedback, energy consumption after one year is compared with energy data before the package of measures.
❖ Criterion for profitability: The interest rate is the basis for the assessment of an investment.
When applying the interest rate method, the profitability criterion is that the internal rate is higher than the calculated interest rate. As far as energy saving measures are concerned, one can expect a larger future price increase than average inflation. Thus, the interest rate r is replaced by a corrected interest rate r.
rcorrect ≈r-q
❖ Action package in internal rate charts: Once a number of energy saving measures have been identified and their cost calculated and energy savings, all can be inserted as points in an internal rate chart. From each such point one can then insert a line to the origin, where the line's slope thus represents internal rate of return. By arranging all these lines after decreasing slope, the action package, i.e., a package containing the most energy-efficient measures is formed.
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3. Method:
The study was performed by conducting an energy simulation of the building in concern to check the influence of different possible renovation measures in building. For the simulation, the IDA ICE version 4.8 was used as the software. The recommendations from Feby 18 and BBR regulations were strictly followed in this process. The study object of this experiment was an old single family residential building and the only material involved in this study was a personal computer. Since no test persons were involved in this process, there remains no issues regarding ethical considerations.
3.1.Simulation
The research was conducted in different consecutive steps. At first a study was conducted to gain sufficient knowledge on the input parameters to be taken into consideration for the energy simulation of the building. The simulation was performed with the help of IDA ICE 4.8 software for two cases:
before renovation and after renovation. Next, the results were analyzed to compare with the house model before renovation. After analyzing the result with respect to heating, cooling, indoor climate, and green footprint, focus was given on economic analysis and energy rating of the building. The economic analysis was done using the software BELOK Totaltool version 2. Then, the energy rating of the building was calculated according to the regulations from Boverket.
The simulation process with IDA ICE consisted of some steps. At first, the building geometry was formed according to available floor plan of the building. Then input parameters were set in the software keeping in mind the construction used in buildings during the years 60s and 70s. Simulation was made for a period of 1 year. Then, renovations were made to the model by changing different parameters to carry out simulation again.
Figure 8: Side views of the building body
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Figure 9: Back view of the building body
The location of the building was chosen Söderhamn from the software, since the location for Gävle was not available in the software. The climate file of Söderhamn was selected. The wind profile was assumed to be suburban, since the villa was a bit away from the centrum. For holidays, the public holidays of Sweden were used from the IDA ICE file. The orientation of the site was 45° and the building made 60.4492° with the x-axis. The values of pressure coefficients and system parameters were the default values from the IDA ICE software.
In very general terms, where room heating (space heating) might have a COP of 3.5, when heating a hot water cylinder, the COP may be only 2.5 (Cantor, 2020). According to Sveby, the COP of electric heating and domestic hot water were set 4 and 1 respectively. The COP of room unit heaters, that is, electric radiators was 1.
3.1.1. Simulation of the base model:
Ekström and Blomsterberg (2016) made a research on building envelope, material type and thickness for four types of single-family houses in Sweden in which the structure of the villa from Umeå resembled the villa in Valbo. As a consequence, the U values and construction details of walls, roofs and slabs for the simulation were estimated to be the same as that for the villa in Umeå. Bhattacharjee (2016) provided the information regarding construction type and u values for floors and doors of the villa. Since the villa was constructed in 1976, the building code of 1975 was followed for the construction details. However, the ground u-value was calculated according to instructions from BS EN ISO 13370 (See appendix A). The thermal conductivity of soil was taken to be 0.45 m2K/W according to Bhattacharjee (2016). The information for integrated window shading and glazing were taken from Bülow-Hübe (2001). Table 6 shows the construction and u values for different building envelopes that were used to form the base model of the villa.
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Table 6: U values of building parts used for base model
Building part Construction U value
External wall 10 mm plywood + 180 mm mineral wool/stud frame (145+70)×34 mm +13mm gypsum board
0.23
Internal wall 10 mm plywood + 180 mm mineral wool/stud frame (145+70)×34 mm +13mm gypsum board
0.23
Internal floor or foundation Same as ext. floor 0.15
Roof Roof truss 45×195 c/c 1200
mm + 300 mm min, wool
0.15
External floor Chip board, polystyrene and concrete
0.15
Basement wall towards ground
Concrete wall with insulation
0.23
Slab towards ground Concrete slab with coating 2.9
Glazing Triple pane 1.9
Door 70 mm wood 1.5
Integrated window shading Venetian blind between glass panes
Not applicable
The thermal bridges account for 25 % of the heat losses from the building envelope according to Ekström and Blomsterberg (2016)1. However, since the building was lastly renovated in 2005, it was assumed that the thermal bridges were close to good on average and the thermal bridges were defined manually in the software.
The infiltration through the villa was calculated manually and can be found in Appendix C. It was considered that the measured airflow in the single-family house is 0.23 l/sm2Atemp (Bhattacharjee, 2006)2. The calculated value of infiltration was 0.999 l/sm2 at 50 Pascal.
1 Sweden Green Building Council, 2014.
2 Så mår våra hus-Redovisning av regering suppdrag beträffande tekniska utformning. Boverket, 2009.
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A four-person family uses around 3500 - 6500 kWh of energy annually for the domestic hot water (Swedish Energy Agency, 2015). It was assumed that the average annual domestic hot water consumption in the house was 3509 kWh where the distribution system losses were typical and the distribution of hot water use was uniform. It was also assumed that the house contained 4 occupants since, it was a single-family house with four bedrooms. The occupancy schedule is given in Appendix D. It was assumed that occupants were always present in the house except 8 am to 17 pm on workdays. The met values were selected based on activity levels of the occupants according to ASHRAE Fundamentals (EQUA Simulation AB, 2013). It was predicted that high level of activity was performed in the allrum. Energy used for lighting was 292 kWh per year and for equipment was 17999 kWh per year. 5 kW of LED lights of luminous efficacy 80 lm/W were each used for individual rooms. The convective fraction of the lights was 0.78 according to Ahn et al. (2015).
Since the lighting schedule could vary depending on individual preference and habits of the occupants, it was assumed that they remained on between 6 to 8 am in the morning and 3 to 11 pm in the evening (according to default lighting schedule on IDA ICE). The equipment was assumed to be on the living room, kitchen and laundry rooms.
Table 7: Equipment's power in different rooms
Rooms Living room Kitchen Laundry rooms
Equipment’s power 60.04W 2588.5W 1400W
The schedule for equipment was chosen based on the occupancy of inhabitants and can be seen in appendix B. The energy used in domestic hot water, lighting and equipment were chosen in such a way so that their sum equals the total annual operational energy consumption in the building.
The values of heating and cooling set points are given 21 and 26 degrees Celsius according to the regulations of Feby 18. It was assumed that no cooling was needed for the house since summer stays for a short period in Sweden. A standard Air Handling unit was used with heat recovery ventilation system. The type of ventilation system used in the central (exhaust and supply) Air handling unit was Constant Air Volume. The supply air and return air flow in different zones were 0.35 l/s.m2 according to Feby 18. Air was supplied into Sovrum3 and extracted from WC as shown in the building floor plan. The set point for supply air temperature was 16 degree Celsius, effectiveness of heat exchanger and fan were 0.6 and Specific fan power was 1kW/ (m3/s) which are the default values in IDA ICE. The operating schedules for heat exchangers and fans were given the same as air supply schedule. A standard plant was used for the simulation of the base case.
3.1.2. Simulation of renovated building
Figure 10: Building models front view with solar installations
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There was possibility to choose a number of renovation measures to strengthen the old villa.
However, some of these measures could enhance the aesthetic look of the building but increase energy consumption, for example setting tiles on the roof. Some renovations could decrease the need for energy supply in the building but it may not be cost-effective, for example, renovating the foundation. The room temperature can be reduced from 21 to 18 degree Celsius, however, that could cause thermal discomfort. Repairing and demolishing different parts of the building could increase the amount of carbon dioxide in the building. Thus, the method of choosing the renovation measures was quite complicated. A number of sensitivity analyses had been done to understand the effect on electric energy demand in the building. Based on these results, which are found on chapter 4, section 2, a set of renovation measures were chosen for the final simulation that would fulfil the aims of this study. A flow chart describing the methodology of simulation steps is given below.
Figure 11: Flow chart of renovation method
