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ScienceDirect
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Available online at www.sciencedirect.com
ScienceDirect
Energy Procedia 00 (2017) 000–000
www.elsevier.com/locate/procedia
1876-6102 © 2017The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
The 15th International Symposium on District Heating and Cooling
Assessing the feasibility of using the heat demand-outdoor
temperature function for a long-term district heat demand forecast
I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc
aIN+ Center for Innovation, Technology and Policy Research -Instituto Superior Técnico,Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
bVeolia Recherche & Innovation,291 Avenue Dreyfous Daniel, 78520 Limay, France
cDépartement Systèmes Énergétiques et Environnement -IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract
District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the
greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat
sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease,
prolonging the investment return period.
The main scope of this paper is to assess the feasibility of using the heat demand –outdoor temperature function for heat demand
forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665
buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district
renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were
compared with results from a dynamic heat demand model, previously developed and validated by the authors.
The results showed that when only weather change is considered, the margin of error could be acceptable for some applications
(the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation
scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered).
The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the
decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and
renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the
coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and
improve the accuracy of heat demand estimations.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and
Cooling.
Keywords: Heat demand; Forecast; Climate change
Energy Procedia 143 (2017) 73–79
1876-6102 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium & Forum: Low
Carbon Cities & Urban Energy Joint Conference.
10.1016/j.egypro.2017.12.650
10.1016/j.egypro.2017.12.650 1876-6102
Available online at www.sciencedirect.com
ScienceDirect
Energy Procedia 00 (2017) 000–000
w
ww.elsevier.com/locate/procedia
1876-6102 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium &
Forum: Low Carbon Cities & Urban Energy Joint Conference.
World Engineers Summit – Applied Energy Symposium & Forum: Low Carbon Cities & Urban
Energy Joint Conference, WES-CUE 2017, 19–21 July 2017, Singapore
Effect of different renovation actions, their
investment cost and future potential
Anders Avelina , Erik Dahlquista, and Fredrik Wallina
aMälardalen University, Box 883, Västerås SE-721 23, Sweden
Abstract
65% of the buildings in Västerås, situated in the region of Mälardalen, Sweden were built before 1970. It is thus time for
renovation. The situation is the same in most cities in Sweden and Northern Europe. The depth of renovation can be quite
different. In this paper we evaluate some examples where cost is compared to energy saving effect. How to plan renovation to
make use of the available capital in the cities is discussed. As a complement to direct renovation actions also behavior change
with respect to energy is discussed and exemplified. The cost for energy actions in relation to other renovation aspects is
discussed especially for the passive house case in Allingsås, Sweden. The passive house center calculate an extra cost for passive
house standard to be 10 000 €/apartment while an external consultant has the figure 40 000 € of the total cost of 120 000 €. With
this space heating can be 18 kWh/m2.year, or a reduction by 84 % with respect to space heating and 62% for overall heat and hot
water demand. If you use the latter cost figure passive house standard is not motivated from an energy savings perspective while
if using the lower figure it is very interesting. For the other less deep renovations we see that adding more insulation and three
glass windows is motivated if the degradation has been strong, while a simpler renovation may be ok if the outer surface coating
is not too bad. For these less deep renovations we see cost figures of 65 €/m2 respectively 28 €/m2 with reduction of heating and
hot water demand of 56 % respectively 34 %.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the scientific committee of the World Engineers Summit – Applied Energy Symposium &
Forum: Low Carbon Cities & Urban Energy Joint Conference.
Keywords: Renovation; Buildings; Cost; Energy Savings; Passive Houses
1. Introduction
Different renovation actions have been evaluated with respect to energy savings. The renovation of a number of multi-family
houses in Allingsås to passive house standard was evaluated and described in [1] where also a number of other renovation projects
are evaluated with respect to costs and profitability. From the passive house center in Allingsås, complementary information has
been given about the same project in interviews [2]. The energy related costs is reported in [1] to be approximately 40 000 € for a
74 Anders Avelin et al. / Energy Procedia 143 (2017) 73–79
2 Author name / Energy Procedia 00 (2017) 000–000
75 m2 apartment, while the extra specific costs for going from normal renovation to passive house standard is reported to be
approximately 10 000 € per apartment according to Hans Eek at passive house center in Allingsås [2].
This can be compared to the total renovation cost of 120 000 € per apartment including other features not related to energy.
Chigbu [3] describes renovation of villages in Germany as an instrument for renewal generally. Dale [4] has been describing how
renovation was performed in Singapore with it hot climate. Cohen [5] has discussed how to motivate renovations for the board and
financers, while Wallender [6] is discussing costs for different renovation actions generally. Behavior change can reduce energy
use as well. It sometimes is difficult to know if energy reduction is due to concrete renovation actions or due to changed behavior
as renovation gives the tenants awareness of energy aspects, if the real-estate owner performs energy information activities [7-9].
This is especially related to hot water use and household electricity.
The energy for space heating has dropped for each kWh/m2 living area during the last 50-60 years but much less than could be
expected if we look at the much better technology used [10]. It can be interesting to look at some concrete examples of renovation
made during the last few years and investigate what effect those have given.
Table 1. Amount of buildings built in Sweden during different times and average kWh/m2 building area [10]. The % of buildings was made until
2003.
Building year % of buildings kWh/m2
2011-2013 Not available 90
1991-2003 7% 120
1981-1990 10% 130
1971-1980 17% 135
1951-1970 34% 140
1921-1950 20% 150
-1920 12% 160
During the last decades about 2500-3000 units are being retrofitted annually in Sweden. Today 29% of single-family houses
have direct electricity for space heating and hot water while 92% of multi-family houses have district heating. In 2010 52% of all
single-family houses was using heat pump technology, or nearly 1 million heat pumps.
40% of all energy used in Sweden 2013 was for residential and service sector, and almost 41% of this energy was in single
family houses, 31 % for multi-family houses respectively. The remaining 28% of energy is then used in commercial buildings [10].
The energy distribution on different means is not well known, but rough numbers from EU-countries are given by [12]. According
to this report the use of energy in households in Sweden is approximately 58% for space heating, 22% for hot water production,
3% for cooking and remaining 17 % for appliances. Roughly 60% of energy in household are used for heating in EU.
2. Consumption statistics and energy renovation experiences – examples from different cities in Sweden
2.1 Västerås, Sweden
The Västerås is a city with 145 218 inhabitants. According to Statistics Sweden [11] the built area including gardens is 8.2 %
or 7843 ha. 43% of the buildings are detached, single family houses and 48.8% constitutes of apartments in multi-family houses.
The remaining buildings, 8.2 %, is industrial and commercial buildings. Most cities in Sweden have similar conditions as Vasteras
with respect to when houses were built and standard of the buildings and thus Vasteras can represent also many other cities from a
renovation demand perspective. If we look at the whole Sweden there are 4.7 million apartments, from which 2 million detached
houses single family) and 2.35 million apartments in multi-family buildings. The average size of a multi-family apartment is 68 m2
while the average single family house is 122 m2[11]. The size of the households inVästerås is as follows: 17.4 % with 1 person,
27.7 % with 2 persons, 16.7 with 3, 21.3 % with 4 and 15.2 % with 5 or more persons. The total amount of households in Västerås
is about 65 000 units and the square meters for each buildings type is estimated to following: Single family houses:
(Ekv 1); Multi-family houses: (Ekv
2). Potential reduction by some 60%*(1-(50/200) kWh/m2)= 45 % of the total household energy if we extrapolate from the
discussion from Sweden above. This would mean some 3310 x 0.45 = 1490 TWh/y potential saving for heating. Aside of heating
also hot water is a significant cost in apartments. In figure 1 (left) we see how it varies between different apartments in two buildings
in Vasteras. The difference between the highest and lowest consumer is 10 times! The energy use is also about the same for the
Author name / Energy Procedia 00 (2017) 000–000 3
tenants between years 2005 and 2006, except for apartment no 16, where both hot water and electricity has dropped dramatically.
The reasons is due to changed behavior of the tenants, but not known in detail.
Another study was made on electrically heated and non-electric heated detached houses in the Västerås area as well. These are
mainly situated in the country-side of the municipality and do not have access to district heating. The total amount of consumed
electricity were compared in the houses per square meter living area and related to the various number of persons per household
(pph), and with different heating systems. The consumption data are seen in figure 1 (right). It is possible to see that the total
consumption of electricity for direct electric heating and other use is around 160 kWh/m
2
with a small increase when +3 pph are
compared to 1 pph. For those who had installed heat pumps we would expect significantly lower use of electricity, but the reduction
is minor, and the total consumption around 120-130 kWh
el
/m
2
living area, but varying quite a lot. This indicates that a lot of heat
is released also from other appliances making the effect of the heat pump less than expected. In the next group the households have
a combination of electric and other type of heating device like wood-stove or oil. The total electricity demand then decrease to
around 110 – 120 kWh/m
2
. When the heating system is totally without direct electricity the electricity consumption drops
significantly, as it only relates to appliances, but not space heating or hot water production, as these are produced by wood stove,
oil fired boiler or similar.
From these figures we can see that the individual use of electricity varies a lot. This complicates predictions of consumption on
an individual level, but average values still are possible to use for system analysis.
Figure 1. (Left) Hot water consumption in 24 apartments in Vasteras. (Right) Total electricity consumption (kWh/m
2
) for various household size.
2.2 Eskilstuna, Sweden
Lagersberg, Eskilstuna
Before the renovation in the multi-family area Lagersberg, in city of Eskilstuna, the following calculations were made for the
energy use before the actions were made. This is called Base case and was 155 kWh/m
2
at A temp,y. Estimates of what effect
different renovation actions should give on energy use was then made: Improved temperature control 2 kWh/m
2
, 500 mm extra
insulation in attic 4 kWh/m
2
, New base channels for the ventilation 5 kWh/m
2
, Exchange window in kitchen to three glasses 8
kWh/m
2
, Solar power at the roof (151 m
2
) reduced purchased heat 6 kWh/m
2
, Energy glass in 60% of the windows 10 kWh/m
2
,
Individual hot water measurement 12 kWh/m
2
(also charged hot water individually compared to included in the rent earlier),
Insulation of outer walls with 50 mm + plaster 18 kWh/m
2
, FTX ventilation 19 kWh/m
2
. The total reduction from all these measures
should be 83 kWh/m
2
and the energy use after the renovation should be 72 kWh/m
2
compared to the 155 kWh/m
2
before. Some of
these actions are very concrete technical investments while others are more behavioral related. Improved temperature control is a
mixture between technical and behavioral aspects, while individual hot water consumption is almost purely behavioral. Solar power
at the roof does not really improve the actual energy use, but adds additional “internal heat”, which then according to Swedish
regulations right now gives benefits to the overall balance. When we measure the effect of the different actions we only get an
overall reduction figure where technical and behavioral measures are mixed. The quality of the work made by the renovation
company then is difficult to measure exactly as more behavior related aspects may impact significantly. This is seen especially in
the figures from Råbergstorp, where we can see big differences between different buildings where principally the same actions
have been taken. Comparing UC 229 to UC 232 shows a big difference in space heating reduction while the hot water reduction is
the opposite. The total reduction though is similar. As hot water and heat supply by district heating was measured as the total
before, the figures built on assumptions of distribution between space heating and hot water consumption was probably not correct.
By measuring many buildings the overall figures becomes better, but individual variations still exist and influence sometimes quite
Anders Avelin et al. / Energy Procedia 143 (2017) 73–79 75
2 Author name / Energy Procedia 00 (2017) 000–000
75 m2 apartment, while the extra specific costs for going from normal renovation to passive house standard is reported to be
approximately 10 000 € per apartment according to Hans Eek at passive house center in Allingsås [2].
This can be compared to the total renovation cost of 120 000 € per apartment including other features not related to energy.
Chigbu [3] describes renovation of villages in Germany as an instrument for renewal generally. Dale [4] has been describing how
renovation was performed in Singapore with it hot climate. Cohen [5] has discussed how to motivate renovations for the board and
financers, while Wallender [6] is discussing costs for different renovation actions generally. Behavior change can reduce energy
use as well. It sometimes is difficult to know if energy reduction is due to concrete renovation actions or due to changed behavior
as renovation gives the tenants awareness of energy aspects, if the real-estate owner performs energy information activities [7-9].
This is especially related to hot water use and household electricity.
The energy for space heating has dropped for each kWh/m2 living area during the last 50-60 years but much less than could be
expected if we look at the much better technology used [10]. It can be interesting to look at some concrete examples of renovation
made during the last few years and investigate what effect those have given.
Table 1. Amount of buildings built in Sweden during different times and average kWh/m2 building area [10]. The % of buildings was made until
2003.
Building year % of buildings kWh/m2
2011-2013 Not available 90
1991-2003 7% 120
1981-1990 10% 130
1971-1980 17% 135
1951-1970 34% 140
1921-1950 20% 150
-1920 12% 160
During the last decades about 2500-3000 units are being retrofitted annually in Sweden. Today 29% of single-family houses
have direct electricity for space heating and hot water while 92% of multi-family houses have district heating. In 2010 52% of all
single-family houses was using heat pump technology, or nearly 1 million heat pumps.
40% of all energy used in Sweden 2013 was for residential and service sector, and almost 41% of this energy was in single
family houses, 31 % for multi-family houses respectively. The remaining 28% of energy is then used in commercial buildings [10].
The energy distribution on different means is not well known, but rough numbers from EU-countries are given by [12]. According
to this report the use of energy in households in Sweden is approximately 58% for space heating, 22% for hot water production,
3% for cooking and remaining 17 % for appliances. Roughly 60% of energy in household are used for heating in EU.
2. Consumption statistics and energy renovation experiences – examples from different cities in Sweden
2.1 Västerås, Sweden
The Västerås is a city with 145 218 inhabitants. According to Statistics Sweden [11] the built area including gardens is 8.2 %
or 7843 ha. 43% of the buildings are detached, single family houses and 48.8% constitutes of apartments in multi-family houses.
The remaining buildings, 8.2 %, is industrial and commercial buildings. Most cities in Sweden have similar conditions as Vasteras
with respect to when houses were built and standard of the buildings and thus Vasteras can represent also many other cities from a
renovation demand perspective. If we look at the whole Sweden there are 4.7 million apartments, from which 2 million detached
houses single family) and 2.35 million apartments in multi-family buildings. The average size of a multi-family apartment is 68 m2
while the average single family house is 122 m2[11]. The size of the households inVästerås is as follows: 17.4 % with 1 person,
27.7 % with 2 persons, 16.7 with 3, 21.3 % with 4 and 15.2 % with 5 or more persons. The total amount of households in Västerås
is about 65 000 units and the square meters for each buildings type is estimated to following: Single family houses:
(Ekv 1); Multi-family houses: (Ekv
2). Potential reduction by some 60%*(1-(50/200) kWh/m2)= 45 % of the total household energy if we extrapolate from the
discussion from Sweden above. This would mean some 3310 x 0.45 = 1490 TWh/y potential saving for heating. Aside of heating
also hot water is a significant cost in apartments. In figure 1 (left) we see how it varies between different apartments in two buildings
in Vasteras. The difference between the highest and lowest consumer is 10 times! The energy use is also about the same for the
Author name / Energy Procedia 00 (2017) 000–000 3
tenants between years 2005 and 2006, except for apartment no 16, where both hot water and electricity has dropped dramatically.
The reasons is due to changed behavior of the tenants, but not known in detail.
Another study was made on electrically heated and non-electric heated detached houses in the Västerås area as well. These are
mainly situated in the country-side of the municipality and do not have access to district heating. The total amount of consumed
electricity were compared in the houses per square meter living area and related to the various number of persons per household
(pph), and with different heating systems. The consumption data are seen in figure 1 (right). It is possible to see that the total
consumption of electricity for direct electric heating and other use is around 160 kWh/m
2
with a small increase when +3 pph are
compared to 1 pph. For those who had installed heat pumps we would expect significantly lower use of electricity, but the reduction
is minor, and the total consumption around 120-130 kWh
el
/m
2
living area, but varying quite a lot. This indicates that a lot of heat
is released also from other appliances making the effect of the heat pump less than expected. In the next group the households have
a combination of electric and other type of heating device like wood-stove or oil. The total electricity demand then decrease to
around 110 – 120 kWh/m
2
. When the heating system is totally without direct electricity the electricity consumption drops
significantly, as it only relates to appliances, but not space heating or hot water production, as these are produced by wood stove,
oil fired boiler or similar.
From these figures we can see that the individual use of electricity varies a lot. This complicates predictions of consumption on
an individual level, but average values still are possible to use for system analysis.
Figure 1. (Left) Hot water consumption in 24 apartments in Vasteras. (Right) Total electricity consumption (kWh/m
2
) for various household size.
2.2 Eskilstuna, Sweden
Lagersberg, Eskilstuna
Before the renovation in the multi-family area Lagersberg, in city of Eskilstuna, the following calculations were made for the
energy use before the actions were made. This is called Base case and was 155 kWh/m
2
at A temp,y. Estimates of what effect
different renovation actions should give on energy use was then made: Improved temperature control 2 kWh/m
2
, 500 mm extra
insulation in attic 4 kWh/m
2
, New base channels for the ventilation 5 kWh/m
2
, Exchange window in kitchen to three glasses 8
kWh/m
2
, Solar power at the roof (151 m
2
) reduced purchased heat 6 kWh/m
2
, Energy glass in 60% of the windows 10 kWh/m
2
,
Individual hot water measurement 12 kWh/m
2
(also charged hot water individually compared to included in the rent earlier),
Insulation of outer walls with 50 mm + plaster 18 kWh/m
2
, FTX ventilation 19 kWh/m
2
. The total reduction from all these measures
should be 83 kWh/m
2
and the energy use after the renovation should be 72 kWh/m
2
compared to the 155 kWh/m
2
before. Some of
these actions are very concrete technical investments while others are more behavioral related. Improved temperature control is a
mixture between technical and behavioral aspects, while individual hot water consumption is almost purely behavioral. Solar power
at the roof does not really improve the actual energy use, but adds additional “internal heat”, which then according to Swedish
regulations right now gives benefits to the overall balance. When we measure the effect of the different actions we only get an
overall reduction figure where technical and behavioral measures are mixed. The quality of the work made by the renovation
company then is difficult to measure exactly as more behavior related aspects may impact significantly. This is seen especially in
the figures from Råbergstorp, where we can see big differences between different buildings where principally the same actions
have been taken. Comparing UC 229 to UC 232 shows a big difference in space heating reduction while the hot water reduction is
the opposite. The total reduction though is similar. As hot water and heat supply by district heating was measured as the total
before, the figures built on assumptions of distribution between space heating and hot water consumption was probably not correct.
By measuring many buildings the overall figures becomes better, but individual variations still exist and influence sometimes quite
76 Anders Avelin et al. / Energy Procedia 143 (2017) 73–79
4 Author name / Energy Procedia 00 (2017) 000–000
a lot. In table we see the energy used per m2, Atemp for two groups of apartment houses with one sub central for each group. 2010
the private company Pagoden started their renovations in Råbergstorp, Eskilstuna with adding fluffy glass wool at the attics,
approximately 3 dm. This gave a heat demand reduction by some 4-5 %. The district heating system was refurbished so that the
heat was distributed and measured for just a few houses, instead of the whole area as earlier. At the same time the heat distribution
was controlled to each house to keep the temperature at 21 oC, compared to set point 24 oC before. Due to measurement in each
3rd apartment the temperature could be controlled much better than earlier, which made this possible. This was done for all
buildings in Eskilstuna owned by Pagoden. As the measurement position was moved close to the buildings instead of only one
common positions to the whole area, losses in the supply pipes was reduced from Pagoden perspective. It is not known how much
of the total energy savings that is related to this. Exhaust air heat pumps were installed in some buildings 2012-2013. The variation
between the different houses makes it difficult to make clear conclusions on effect of automated temperature control (end of 2011
– beginning of 2012) in comparison to other actions made like refurbishing the plaster and repainting (202 October 2014, 203-204
June 2015).
Four of the houses at Råbergstorp (group 202, Domaregatan 12) were renovated by refurbishing plaster and re-painted. This
was done in October 2013. The total number of apartments is 77 and the living area 7889 m2. Reference measurements have been
made since then. Summer 2014 (June-July) another two building groups (203 with 5469 m2 living area and 204 with 5882 m2
living area) were refurbished in the same way. The district heat (including hot water) used before and after these actions has been
monitored and can be seen in table 3 below. What we can see here is that we had significant reductions in energy from 2012 to
2014 due to the different energy conservation measures, but it is not possible to clearly separate the effects of different actions from
each other. The change in district heating consumption (including hot water) after refurbishment of external walls are about 8.9 %
reduction in building group 202 while building group 203 shows only 1% decrease. The effect from surface refurbishment is too
small to be possible to separate from other aspects like e.g. behavior change. With higher resolution on consumption data and
indoor temperature data it would be possible to better separate between effects from temperature control, heat pumps and improved
insulation levels of external walls. Such small effect as 0-3 % that can be expected from drier walls after repainting would not be
detectable even with better data due to these other uncertainties unfortunately.
Table 2. Specific energy use in kWh/m2, Atemp in Lagersberg
measured in two district heating sub-centrals (UC)
Before renovation After renovation
UC229 UC232 UC229 UC232
Hot water 31 33 30 16
Space heating 106 108 44 63
Building electricity 22 18 16 15
Household electricity 28 28 28 28
Total 187 187 118 122
Table 3 District heating consumption in kWh/m2 at Råbergstorp.
For six groups of buildings energy saving from 2012 to 2013
respectively from 2013 to 2014 has been made.
Building
group
12-13 13-14 -12 -13 -14 Tot area,
m2
202 27.2% 8.9% 209 168 153 7889
203 21.8% 1.0% 196 156 154 5469
204 16.2% 10% 140 130 117 5882
205 22.9% 3.3% 192 153 148 4246
206 20.0% 0.0% 229 183 183 6831
207 22.4% 2.6% 203 162 157 8101
2.3 Brogården, Allingsås – a renovation to passive house standard
In Allingsås, 16 houses built in 1971-73 with 300 apartments (19 500 m2) were renovated to passive house standard during
2008-2014. This included adding 45-50 cm insulation and enhancement to three glass windows with argon between two glasses,
and also a thin silver layer. The U-value then decreased from 1.2 to 0.85 compared to “normal” three glass windows. In some of
the houses also the house was renovated by taking down all previous surface material and putting up 3-storage elements with
insulation (45 cm glass wool), windows and ventilation channels as pre-prepared elements. The ventilation has also new heat
exchangers giving 88% heat recovery compared to “normal standard”. By not needing the normal heat distribution system savings
in installation cost was some 2000 € per apartment, but in return demanded good precision in mounting the wall elements with the
ventilation channels. Also fire protection aspects had to be considered here as well as handicap adaptation. The garden was
refreshed, waste management improved, new washing machines, renovation of stairs and entrances and some more. Altogether the
cost was some 120 000 € per apartment, but only approximately 40 000 €/apartment was related to energy efficiency measures
according to ÅF consultants [1] or 10 000 €/ apartment according to passive house center in Allingsås [2]. Average size of each
apartment is about 75 m2 living area [2] and the heat demand per apartment decreased from 116 to 19 kWh/m2,y. The total
Author name / Energy Procedia 00 (2017) 000–000 5
households electricity, heat and hot water demand went down from 220 kWh/m2, y to 86 kWh/m2,y according to the first
preliminary measurements in 2015.
As in Lagersberg and Råbergstorp the renovations were done last few years. As comparison the normal building cost for a
completely new building today is approximately 200 000€ for an apartment of this size, some 75 m2. The renovation was as said
120 000€ from which some 10 000 – 40 000 € related to the improved energy shell. The 10 000 € gives a pay-back time just from
the energy savings of slightly less than 10 years according to calculations [2]. The renovation activities are as follows: Extra
insulation at walls, 480 mm (glass wool), and 500 mm in attic and 100 mm at floor. All walls were tightened by plastic film. Energy
glass windows with Argon, U-value 0.85 W/m2,K. Installation of FTX system, solar collectors for production of tap water, Heat
exchanger battery for heating ventilation air with district heating. Individual measurement and invoicing in every apartment with
respect to household electricity and hot water. Some other actions were: new outside balconies, increased size /in bathroom, more
varied size of apartments, old “built in” balconies have been transferred into the living rooms, ceramic plates as outer surface
coating, elevators and introduction of broad band. These other costs have not been included in the energy improvement costs.
Before the renovation the apartments consumed 216 kWh/m2 including household electricity. The renovation was expecting a
decrease of total energy to 92 kWh/m2, or by 57%. Before the renovation the total consumption excluding household energy was
177 kWh/m2. From this 20 kWh/m2 building electricity, 42 kWh/m2 hot water and 115 kWh/m2 space heating. After renovation
the expected value was 65 kWh/m2 but the actual measured value was 58 kWh/m2. Including household electricity the
corresponding values after renovation was 92 respectively 86 kWh/m2. This means a reduction by 62%. If we only look at space
heating the reduction was 85%, from 115 to 18 kWh/m2.
3. Economic consideration from renovations and future potential
3.1 Economic considerations from renovations with different methods
What we can see from these renovations is that it is possible to reduce energy for space heating to around 18 kWh/m2 even in
Swedish climate, without costing prohibiting much money to do so. It is still significantly cheaper to renovate to this standard
than to build new apartments. Still, when we reduce the energy for heating new demands show up to be more important to
address like cooling or protection for unwanted heating during summer from sun radiation. We also can see that then electricity
use for appliances etc. becomes more important as they percentage wise becomes much higher.
A short term negative effect of course will be that the reduced heat load also reduces the benefits with combined heat and
power connected to district heating. Still, long term we will go towards reduced energy losses through walls as better technology
is utilized in new buildings.
What is then the potential for energy savings and how should planning be made for the cities when they renovate existing, less
energy efficient buildings? A good tool can be to use simulation including both energy and economic aspects. We can start with
looking at the cost per m2 in relation to energy savings as kWh/m2 living area. In table 4 we see results from our own
investigations [13].
Table 4 Investment costs and energy savings by renovations
Object Investment €/m2 Savings kWh/m2,y
Allingsås passive house standard 133-570 €/m2 62 - 85 %
Lagersberg advanced renovation 65 €/m2 56.5%
Råbergstorp control + paint 28 €/m2 34 %
Assuming starting from 200 kWh/m2 and using two different energy price levels, 0.05 €/kWh respectively 0.07 €/kWh we
can calculate the Pay Back Time. Assuming different life expectancy of the different levels of renovation actions also the pay-
back time divided by life expectancy [13] is of interest. For the Allingsås case we have used the two different investment cost
levels given by [2] and [1] respectively. Which in table 5 refers to two cases of Allingsås. It shows the difficulty to do cost split
calculations when different aspects have to be considered. With the lower investment cost there is no doubt that the advanced
renovation pay-off, why with the higher cost level it is questionable. So here each city will have to make some kind of more
principal decision how to evaluate different aspects.
Anders Avelin et al. / Energy Procedia 143 (2017) 73–79 77
4 Author name / Energy Procedia 00 (2017) 000–000
a lot. In table we see the energy used per m2, Atemp for two groups of apartment houses with one sub central for each group. 2010
the private company Pagoden started their renovations in Råbergstorp, Eskilstuna with adding fluffy glass wool at the attics,
approximately 3 dm. This gave a heat demand reduction by some 4-5 %. The district heating system was refurbished so that the
heat was distributed and measured for just a few houses, instead of the whole area as earlier. At the same time the heat distribution
was controlled to each house to keep the temperature at 21 oC, compared to set point 24 oC before. Due to measurement in each
3rd apartment the temperature could be controlled much better than earlier, which made this possible. This was done for all
buildings in Eskilstuna owned by Pagoden. As the measurement position was moved close to the buildings instead of only one
common positions to the whole area, losses in the supply pipes was reduced from Pagoden perspective. It is not known how much
of the total energy savings that is related to this. Exhaust air heat pumps were installed in some buildings 2012-2013. The variation
between the different houses makes it difficult to make clear conclusions on effect of automated temperature control (end of 2011
– beginning of 2012) in comparison to other actions made like refurbishing the plaster and repainting (202 October 2014, 203-204
June 2015).
Four of the houses at Råbergstorp (group 202, Domaregatan 12) were renovated by refurbishing plaster and re-painted. This
was done in October 2013. The total number of apartments is 77 and the living area 7889 m2. Reference measurements have been
made since then. Summer 2014 (June-July) another two building groups (203 with 5469 m2 living area and 204 with 5882 m2
living area) were refurbished in the same way. The district heat (including hot water) used before and after these actions has been
monitored and can be seen in table 3 below. What we can see here is that we had significant reductions in energy from 2012 to
2014 due to the different energy conservation measures, but it is not possible to clearly separate the effects of different actions from
each other. The change in district heating consumption (including hot water) after refurbishment of external walls are about 8.9 %
reduction in building group 202 while building group 203 shows only 1% decrease. The effect from surface refurbishment is too
small to be possible to separate from other aspects like e.g. behavior change. With higher resolution on consumption data and
indoor temperature data it would be possible to better separate between effects from temperature control, heat pumps and improved
insulation levels of external walls. Such small effect as 0-3 % that can be expected from drier walls after repainting would not be
detectable even with better data due to these other uncertainties unfortunately.
Table 2. Specific energy use in kWh/m2, Atemp in Lagersberg
measured in two district heating sub-centrals (UC)
Before renovation After renovation
UC229 UC232 UC229 UC232
Hot water 31 33 30 16
Space heating 106 108 44 63
Building electricity 22 18 16 15
Household electricity 28 28 28 28
Total 187 187 118 122
Table 3 District heating consumption in kWh/m2 at Råbergstorp.
For six groups of buildings energy saving from 2012 to 2013
respectively from 2013 to 2014 has been made.
Building
group
12-13 13-14 -12 -13 -14 Tot area,
m2
202 27.2% 8.9% 209 168 153 7889
203 21.8% 1.0% 196 156 154 5469
204 16.2% 10% 140 130 117 5882
205 22.9% 3.3% 192 153 148 4246
206 20.0% 0.0% 229 183 183 6831
207 22.4% 2.6% 203 162 157 8101
2.3 Brogården, Allingsås – a renovation to passive house standard
In Allingsås, 16 houses built in 1971-73 with 300 apartments (19 500 m2) were renovated to passive house standard during
2008-2014. This included adding 45-50 cm insulation and enhancement to three glass windows with argon between two glasses,
and also a thin silver layer. The U-value then decreased from 1.2 to 0.85 compared to “normal” three glass windows. In some of
the houses also the house was renovated by taking down all previous surface material and putting up 3-storage elements with
insulation (45 cm glass wool), windows and ventilation channels as pre-prepared elements. The ventilation has also new heat
exchangers giving 88% heat recovery compared to “normal standard”. By not needing the normal heat distribution system savings
in installation cost was some 2000 € per apartment, but in return demanded good precision in mounting the wall elements with the
ventilation channels. Also fire protection aspects had to be considered here as well as handicap adaptation. The garden was
refreshed, waste management improved, new washing machines, renovation of stairs and entrances and some more. Altogether the
cost was some 120 000 € per apartment, but only approximately 40 000 €/apartment was related to energy efficiency measures
according to ÅF consultants [1] or 10 000 €/ apartment according to passive house center in Allingsås [2]. Average size of each
apartment is about 75 m2 living area [2] and the heat demand per apartment decreased from 116 to 19 kWh/m2,y. The total
Author name / Energy Procedia 00 (2017) 000–000 5
households electricity, heat and hot water demand went down from 220 kWh/m2, y to 86 kWh/m2,y according to the first
preliminary measurements in 2015.
As in Lagersberg and Råbergstorp the renovations were done last few years. As comparison the normal building cost for a
completely new building today is approximately 200 000€ for an apartment of this size, some 75 m2. The renovation was as said
120 000€ from which some 10 000 – 40 000 € related to the improved energy shell. The 10 000 € gives a pay-back time just from
the energy savings of slightly less than 10 years according to calculations [2]. The renovation activities are as follows: Extra
insulation at walls, 480 mm (glass wool), and 500 mm in attic and 100 mm at floor. All walls were tightened by plastic film. Energy
glass windows with Argon, U-value 0.85 W/m2,K. Installation of FTX system, solar collectors for production of tap water, Heat
exchanger battery for heating ventilation air with district heating. Individual measurement and invoicing in every apartment with
respect to household electricity and hot water. Some other actions were: new outside balconies, increased size /in bathroom, more
varied size of apartments, old “built in” balconies have been transferred into the living rooms, ceramic plates as outer surface
coating, elevators and introduction of broad band. These other costs have not been included in the energy improvement costs.
Before the renovation the apartments consumed 216 kWh/m2 including household electricity. The renovation was expecting a
decrease of total energy to 92 kWh/m2, or by 57%. Before the renovation the total consumption excluding household energy was
177 kWh/m2. From this 20 kWh/m2 building electricity, 42 kWh/m2 hot water and 115 kWh/m2 space heating. After renovation
the expected value was 65 kWh/m2 but the actual measured value was 58 kWh/m2. Including household electricity the
corresponding values after renovation was 92 respectively 86 kWh/m2. This means a reduction by 62%. If we only look at space
heating the reduction was 85%, from 115 to 18 kWh/m2.
3. Economic consideration from renovations and future potential
3.1 Economic considerations from renovations with different methods
What we can see from these renovations is that it is possible to reduce energy for space heating to around 18 kWh/m2 even in
Swedish climate, without costing prohibiting much money to do so. It is still significantly cheaper to renovate to this standard
than to build new apartments. Still, when we reduce the energy for heating new demands show up to be more important to
address like cooling or protection for unwanted heating during summer from sun radiation. We also can see that then electricity
use for appliances etc. becomes more important as they percentage wise becomes much higher.
A short term negative effect of course will be that the reduced heat load also reduces the benefits with combined heat and
power connected to district heating. Still, long term we will go towards reduced energy losses through walls as better technology
is utilized in new buildings.
What is then the potential for energy savings and how should planning be made for the cities when they renovate existing, less
energy efficient buildings? A good tool can be to use simulation including both energy and economic aspects. We can start with
looking at the cost per m2 in relation to energy savings as kWh/m2 living area. In table 4 we see results from our own
investigations [13].
Table 4 Investment costs and energy savings by renovations
Object Investment €/m2 Savings kWh/m2,y
Allingsås passive house standard 133-570 €/m2 62 - 85 %
Lagersberg advanced renovation 65 €/m2 56.5%
Råbergstorp control + paint 28 €/m2 34 %
Assuming starting from 200 kWh/m2 and using two different energy price levels, 0.05 €/kWh respectively 0.07 €/kWh we
can calculate the Pay Back Time. Assuming different life expectancy of the different levels of renovation actions also the pay-
back time divided by life expectancy [13] is of interest. For the Allingsås case we have used the two different investment cost
levels given by [2] and [1] respectively. Which in table 5 refers to two cases of Allingsås. It shows the difficulty to do cost split
calculations when different aspects have to be considered. With the lower investment cost there is no doubt that the advanced
renovation pay-off, why with the higher cost level it is questionable. So here each city will have to make some kind of more
principal decision how to evaluate different aspects.
78 Anders Avelin et al. / Energy Procedia 143 (2017) 73–79
6 Author name / Energy Procedia 00 (2017) 000–000
Table 5 Pay-back time (PBT) as years respectively PBT divided with life expectancy of the renovation action.
Object Saved kWh/m2.y Saved €/m2.y PBT year Life expect (Year) PBT/Life expect (%)
Allingsås 1 168 8.4 11.8 15.8 11.3 50 32 23
Allingsås 2 168 8.4 11.8 68 48 50 136 96
Lagersberg 113 5.7 7.9 11.5 8.2 30 38 27
Råbergstorp 68 3.4 4.8 8.2 5.8 20 41 29
3.2 Future potential – an example of possible renovation enhancements in Västerås
We have noted that we have approximately 3 730 000 m2 living area in single family houses and 2 343 000 m2 in multi-family
buildings in Vasteras city. There is no reason to renovate the youngest buildings but the older where we have the situation as seen
in table 6. Here we have added the total m2 and energy per year for all apartments for each building age.
Table 6 Building area in m2 for each age group and energy use as GWh/year today before renovation.
Age group % of m2 kWh/m2,y Single-family houses Multi-family houses
Tot m2 tot GWh/y Tot m2 Tot GWh/y
1971-1980 17 135 634100 85.6 398310 53.8
1951-1970 34 140 1268200 177.5 796620 111.5
1921-1950 20 150 746000 111.9 468600 70.3
Before 1920 12 160 447600 71.6 281160 45.0
What we can see generally is that buildings 1971-1980 usually are not needing as deep renovation as those that are older, e.g.
new piping or electric cables are normally not needed, and surface coating may be enough with repainting.
In table 7 it is possible to get an overview of investment cost for the different renovation actions compared to the annual
savings in kWh. If we assume the same life expectancy for all investments, it is more favorable from an economic perspective
with the light renovation compared to the passive house standard.
Table 7 Calculation of Investment cost for different renovation actions and energy savings for these and also the ratio
investment cost divided with annual energy savings in €/kWh.
Age group Passive house Allingsås
133€/m2
Lagersberg
65€/m2
Råbergstorp
28 €/m2
GWh Inv M€ €/kWh GWh Inv
M€
€/kWh GWh Inv
M€
€/kWh
1971-1980 45.71 52.98 1.16 25.82 25.89 1.00 18.28 11.15 0.61
1951-1970 94.80 105.95 1.12 53.56 51.78 0.97 37.92 22.31 0.59
1921-1950 59.75 62.32 1.04 33.76 30.46 0.90 23.90 13.12 0.55
Before 1920 38.24 37.39 0.98 21.60 18.28 0.85 15.30 7.87 0.51
Life expectancy 50 30 20
If we on the other hand include how many years we can expect a certain renovation to be valid, the figures becomes like in
table 8. Investment cost divided with saved energy during life expectancy gives a different value. The least deep renovation at
Råbergstorp is still a little better than the more advanced at Lagersberg but the advanced renovation to passive house standard
when calculating with 133 €/m2 now is much better, while the one calculating with 570 €/m2 is far too expensive to be
competitive (see table 8).
Author name / Energy Procedia 00 (2017) 000–000 7
Table 8 Investment cost divided with saved energy during life expectancy [€/(kWh* years)]
Age group Passive house 133€/m2 Lagersberg Råbergstorp Passive house 570€/m2
€/(kWh*y) €/(kWh*y) €/(kWh*y) €/(kWh*y)
1971-1980 0.023181 0.033419 0.030501 0.099346
1951-1970 0.022353 0.032225 0.029412 0.095798
1921-1950
Before 1920
0.020863
0.019559
0.030077
0.028197
0.027451
0.025735
0.089412
0.083824
Life expectancy 50 30 20 50
How to plan the renovation will be very much up to how much money is available and a judgement on the actual demand on
needs for renovation depth. The simulation made can give advice on how to calculate different alternatives and how to divide
cost for renovation on different aspects like energy, modern outlook, handicap friendly etc. It is obvious that these type of
considerations are of high importance to motivate the actions made.
4. Conclusions
Renovations can be made to different depth. Deeper renovation will cost more, but also save more energy and also last longer.
It is not that easy to measure the impact of each action if many actions are made simultaneously, but also behavior changes are
affecting the total consumption of especially hot water and electricity, but also heat as the set point of indoor temperature is
affecting the total consumption a lot.
How far you should go in your renovation for specific buildings depend on how much money is available, the status of the
building before the renovation and how pay off calculations are made – only based on energy reductions or also including other
aspects than pure energy. This will make a big difference when making decisions.
References
[1] Byman, Karin and Jernelius Sara. (2012) “Economy at renovations including energy improvements”. Report ÅF Infrastructure AB.
[2] Eek, Hans, (2015) Interview about Brogården project, Passive house center in Allingsås, 2015.
[3] Chigbu, U. E. (2012). "Village renewal as an instrument of rural development: evidence from Weyarn, Germany". Community Development
43 (2): 209–224
[4] Dale, O. J. (1999). Urban planning in Singapore: The transformation of a city. Oxford University Press, USA.
[5] Cohen, M. (2013). “10 renovation plans your board probably won't go
for”.http://www.brickunderground.com/blog/2013/09/10_renovation_plans_your_board_probably_wont_go_for. | 10/15/2013
[6] Wallender, L. “Estimated Remodeling Costs,By Home Renovations Expert”
http://homerenovations.about.com/od/legalsafetyissues/a/remodelcosts.htm
[7] Vassileva, I, Wallin, F, Ding, Y, Beigl, M and Dahlquist E. (2011) “Household indicators for developing innovative feedback technologies.”
In proceedings of the Innovative Smart Grid technologies Europe; 2011, IEE PES International Conference and Exhibition on Innovative
Smart Grid Technologies – Europe; pp. 1-7,. Doi: 10.1109/ISGTEurope.2011.6162715.
[8] Vassileva, I, Dahlquist, E, Wallin, F and Campillo J. (2013) Energy consumption feedback devices’ impact evaluation on energy use. Applied
Energy 106 (2013) 314-320.
[9] Vassileva, I. (2013) “Characterization of household energy consumption in Sweden. Energy savings potential and feedback approaches.”
Mälardalen University Press Dissertations No, 129; ISBN 978-91-7485-077-2, 2013.
[10] Wang, Q. (2016). Low-temperature heating in Existing Swedish Residential Buildings: Toward Sustainable Retrofitting (Doctoral
dissertation, KTH Royal Institute of Technology).
[11] SCB, Statistics Sweden (2017). “Household budget survey (HBS) “, http://www.statistikdatabasen.scb.se
[12] Bosseboeuf, D., Lapillonne, B., & Eichhammer, W. (2005). Measuring energy efficiency progress in the EU: The energy efficiency index
ODEX. Proceedings of the 2005 European Council for an Energy Efficient Economy Summer Study, Stockholm, Sweden, 1127-1135.
[13] Campillo, Javier, Dahlquist, Erik, Juan E, Arias, Esteban, Vieites, Vassileva, Iana. (2016) "Building Renovation and Retrofitting Actions for
Improving Energy Efficiency and Attractiveness of Old City Areas." Journal of Settlements and Spatial Planning: 1484-1
http://jssp.reviste.ubbcluj.ro, 2016.
Anders Avelin et al. / Energy Procedia 143 (2017) 73–79 79
6 Author name / Energy Procedia 00 (2017) 000–000
Table 5 Pay-back time (PBT) as years respectively PBT divided with life expectancy of the renovation action.
Object Saved kWh/m2.y Saved €/m2.y PBT year Life expect (Year) PBT/Life expect (%)
Allingsås 1 168 8.4 11.8 15.8 11.3 50 32 23
Allingsås 2 168 8.4 11.8 68 48 50 136 96
Lagersberg 113 5.7 7.9 11.5 8.2 30 38 27
Råbergstorp 68 3.4 4.8 8.2 5.8 20 41 29
3.2 Future potential – an example of possible renovation enhancements in Västerås
We have noted that we have approximately 3 730 000 m2 living area in single family houses and 2 343 000 m2 in multi-family
buildings in Vasteras city. There is no reason to renovate the youngest buildings but the older where we have the situation as seen
in table 6. Here we have added the total m2 and energy per year for all apartments for each building age.
Table 6 Building area in m2 for each age group and energy use as GWh/year today before renovation.
Age group % of m2 kWh/m2,y Single-family houses Multi-family houses
Tot m2 tot GWh/y Tot m2 Tot GWh/y
1971-1980 17 135 634100 85.6 398310 53.8
1951-1970 34 140 1268200 177.5 796620 111.5
1921-1950 20 150 746000 111.9 468600 70.3
Before 1920 12 160 447600 71.6 281160 45.0
What we can see generally is that buildings 1971-1980 usually are not needing as deep renovation as those that are older, e.g.
new piping or electric cables are normally not needed, and surface coating may be enough with repainting.
In table 7 it is possible to get an overview of investment cost for the different renovation actions compared to the annual
savings in kWh. If we assume the same life expectancy for all investments, it is more favorable from an economic perspective
with the light renovation compared to the passive house standard.
Table 7 Calculation of Investment cost for different renovation actions and energy savings for these and also the ratio
investment cost divided with annual energy savings in €/kWh.
Age group Passive house Allingsås
133€/m2
Lagersberg
65€/m2
Råbergstorp
28 €/m2
GWh Inv M€ €/kWh GWh Inv
M€
€/kWh GWh Inv
M€
€/kWh
1971-1980 45.71 52.98 1.16 25.82 25.89 1.00 18.28 11.15 0.61
1951-1970 94.80 105.95 1.12 53.56 51.78 0.97 37.92 22.31 0.59
1921-1950 59.75 62.32 1.04 33.76 30.46 0.90 23.90 13.12 0.55
Before 1920 38.24 37.39 0.98 21.60 18.28 0.85 15.30 7.87 0.51
Life expectancy 50 30 20
If we on the other hand include how many years we can expect a certain renovation to be valid, the figures becomes like in
table 8. Investment cost divided with saved energy during life expectancy gives a different value. The least deep renovation at
Råbergstorp is still a little better than the more advanced at Lagersberg but the advanced renovation to passive house standard
when calculating with 133 €/m2 now is much better, while the one calculating with 570 €/m2 is far too expensive to be
competitive (see table 8).
Author name / Energy Procedia 00 (2017) 000–000 7
Table 8 Investment cost divided with saved energy during life expectancy [€/(kWh* years)]
Age group Passive house 133€/m2 Lagersberg Råbergstorp Passive house 570€/m2
€/(kWh*y) €/(kWh*y) €/(kWh*y) €/(kWh*y)
1971-1980 0.023181 0.033419 0.030501 0.099346
1951-1970 0.022353 0.032225 0.029412 0.095798
1921-1950
Before 1920
0.020863
0.019559
0.030077
0.028197
0.027451
0.025735
0.089412
0.083824
Life expectancy 50 30 20 50
How to plan the renovation will be very much up to how much money is available and a judgement on the actual demand on
needs for renovation depth. The simulation made can give advice on how to calculate different alternatives and how to divide
cost for renovation on different aspects like energy, modern outlook, handicap friendly etc. It is obvious that these type of
considerations are of high importance to motivate the actions made.
4. Conclusions
Renovations can be made to different depth. Deeper renovation will cost more, but also save more energy and also last longer.
It is not that easy to measure the impact of each action if many actions are made simultaneously, but also behavior changes are
affecting the total consumption of especially hot water and electricity, but also heat as the set point of indoor temperature is
affecting the total consumption a lot.
How far you should go in your renovation for specific buildings depend on how much money is available, the status of the
building before the renovation and how pay off calculations are made – only based on energy reductions or also including other
aspects than pure energy. This will make a big difference when making decisions.
References
[1] Byman, Karin and Jernelius Sara. (2012) “Economy at renovations including energy improvements”. Report ÅF Infrastructure AB.
[2] Eek, Hans, (2015) Interview about Brogården project, Passive house center in Allingsås, 2015.
[3] Chigbu, U. E. (2012). "Village renewal as an instrument of rural development: evidence from Weyarn, Germany". Community Development
43 (2): 209–224
[4] Dale, O. J. (1999). Urban planning in Singapore: The transformation of a city. Oxford University Press, USA.
[5] Cohen, M. (2013). “10 renovation plans your board probably won't go
for”.http://www.brickunderground.com/blog/2013/09/10_renovation_plans_your_board_probably_wont_go_for. | 10/15/2013
[6] Wallender, L. “Estimated Remodeling Costs,By Home Renovations Expert”
http://homerenovations.about.com/od/legalsafetyissues/a/remodelcosts.htm
[7] Vassileva, I, Wallin, F, Ding, Y, Beigl, M and Dahlquist E. (2011) “Household indicators for developing innovative feedback technologies.”
In proceedings of the Innovative Smart Grid technologies Europe; 2011, IEE PES International Conference and Exhibition on Innovative
Smart Grid Technologies – Europe; pp. 1-7,. Doi: 10.1109/ISGTEurope.2011.6162715.
[8] Vassileva, I, Dahlquist, E, Wallin, F and Campillo J. (2013) Energy consumption feedback devices’ impact evaluation on energy use. Applied
Energy 106 (2013) 314-320.
[9] Vassileva, I. (2013) “Characterization of household energy consumption in Sweden. Energy savings potential and feedback approaches.”
Mälardalen University Press Dissertations No, 129; ISBN 978-91-7485-077-2, 2013.
[10] Wang, Q. (2016). Low-temperature heating in Existing Swedish Residential Buildings: Toward Sustainable Retrofitting (Doctoral
dissertation, KTH Royal Institute of Technology).
[11] SCB, Statistics Sweden (2017). “Household budget survey (HBS) “, http://www.statistikdatabasen.scb.se
[12] Bosseboeuf, D., Lapillonne, B., & Eichhammer, W. (2005). Measuring energy efficiency progress in the EU: The energy efficiency index
ODEX. Proceedings of the 2005 European Council for an Energy Efficient Economy Summer Study, Stockholm, Sweden, 1127-1135.
[13] Campillo, Javier, Dahlquist, Erik, Juan E, Arias, Esteban, Vieites, Vassileva, Iana. (2016) "Building Renovation and Retrofitting Actions for
Improving Energy Efficiency and Attractiveness of Old City Areas." Journal of Settlements and Spatial Planning: 1484-1
http://jssp.reviste.ubbcluj.ro, 2016.
