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Marianna Rosa Arpano is a former MSc SBPD student, in the Department of Architecture, Oxford Brookes University, Oxford, UK.
Paola Sassi is a senior lecturer and program leader at Oxford Brookes University, Oxford, UK.
A Multi-Stage Approach to Low Carbon
Housing Renovations
Marianna Rosa Arpano, MSc Paola Sassi, PhD
[Oxford Brookes University] [Oxford Brookes University]
[email protected] [email protected]
ABSTR ACT HEADING
In 2009 the European Union approved “Roadmap 2050” to reduce greenhouse gasses by at least
80% below 1990 levels by 2050. In 2012 the Danish Government established to achieve 100% autonomy
from fossil fuels by 2050 by implementing a strategy that included reducing energy demand of existing
housing that accounts for about 40% of the national gross energy consumption. A mass retrofit of the
existing housing stock could lead to 75% reduction of energy use and carbon emissions. However due to
the cost and disruption of retrofits that can radically improve energy performance of buildings,
strategies that address both disruption and cost have to be considered. One such potential strategy
examined in this paper is a staged approach, which involves different elements of a building to be
upgraded over several years, thus spreading the capital cost of the work and enabling the occupants to
remain in their homes. Applied to the Danish context this approach can also benefit from financial
incentives currently in place. Adopting a case study approach in conjunction with IES modelling, a cost
analysis and interviews with industry experts, this research examines the energy savings, capital cost,
cost savings of a selection of energy improvements measures, and the implications of undertaking the
building work on the occupants of typical Danish detached houses built between 1850-1930. It
concludes by proposing a decision matrix for home owners to achieve the most cost-effective and least
disruptive approach to undertaking radical energy upgrades.
INTRODUCTION
Background
In 2009 the European Union approved “Roadmap 2050” to reduce greenhouse gasses “by at least
80% below 1990 levels by 2050” (Roadmap 2050). In March 2012 the Danish Government established a
new, ambitious Energy Policy, to achieve a 100% autonomy away from fossil fuels by 2050. The
strategy adopted to reach such results involves a consistent reduction of the energy demand. According
to the Danish Energy Policy Report (Ministry of Climate, Energy and Building, 2012), the existing
building stock accounts for about 40% of the total energy consumption; more specifically in 2010 the
69% was related to the housing sector, and the 36% to non-residential buildings (IEA, n.d.; Agency
Danish Energy Agency, 2011). Thus, the biggest savings could be achieved by improving the energy
performance of the less efficient housing stock. However, this mass-retrofit meets two barriers,
involving the government and the private owners: one is financial (Kragh and Rose, 2011, p2252) and
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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one is practical (Thorpe, 2010, p.2). The first requires financial help from the government to the private
owners, and second one requires a solution to prevent the occupants from moving to a temporary home.
A multi-stage or “stepwise” (Galiotto et al., 2012) approach to energy efficient retrofits could address
these issues.
Aim of the research
This paper investigated a staged retrofit strategy as feasible solution to finance a national mass
retrofit; to make an expensive housing retrofit more financially sustainable and more practical. Smaller
and less disruptive works carried out in several stages could distribute the total investment in more than
one transaction; they could also allow the occupants to stay in their homes and avoid additional expenses
to rent a temporary accommodation.
METHODS
Due to time limitations this research has focused on a specific category of detached houses, built
between 1850 and 1930. Detached houses were identified as most diffused and the worst performing
housing type; they account for the 52% of the entire housing stock (Statistics Denmark), and for more
than 330,000 units ( 53%) with EPC labels between D and G and a heating consumption requirement
above 240 kWh/m2/yr (Aggerholm et al., 2010)-.
The construction details and materials of the housing type analyzed were sourced from the Danish
report for TABULA Project (Wittchen and Kragh, 2012). The reference retrofit measures used were
collected from a previous research by SBi, the Danish Building Research Institute (Galiotto et al., 2012),
by VTT, the Technical Research Institute of Finland, (Häkkinen et al., 2012) and Larsen et.al (2011).
IES- VE was chosen as dynamic simulation tool to test the effect of several retrofit measures on the
building performance. A 3d model of a real detached house from 1917 and located in Copenhagen was
built in IES. It was used an average floor, window and floor area; average construction, materials and
shape; the U-values, infiltration rate, boiler type were conformed to those specified in the TABULA
project report (Wittchen and Kragh, 2012). The NCM heating, appliances and occupants’ profiles were
used. The details of the model created and the average building described in TABULA are shown in
Table 1.
Table 1. Multi-Stage Plan. Number of Years for Each Stage.
Average building Example building
U-values Area m2
Wall 1.6 W/m2K 1.6180 W/m
2K 88
Roof 0.6 W/m2K 0.5724 W/m
2K 86
Ground Floor 1.5W/m2K 1.6078 W/m
2K 47
Windows 2.7W/m2K 2.7 W/m
2K 15
Door 2.29 W/m2K
ACH 0.45 0.45
Boiler Old non condens. Old boiler Ɛ=55%
Fuel Oil-gas Oil - gas
Area 112 m2
122 m2
Windows area 15.1 m2 15.1 m
2
Wall area 88 m2
Roof area 86 m2
Slab 47 m2
Ceiling Height 2.5 2.1 (basement, first floor) 2.7
(ground floor)
Location DK Copenhagen
Age of construction 1850-1930 1917
Heating
consumption
263 kWh/m2 yr 265 kWh/m
2 yr
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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ANALYSIS
IES modelling
A first series of simulations was carried by introducing one variable at a time in the model’s
building construction; such as wall, slab or roof insulation, new windows, mechanical ventilation,
heating system. All the measures were previously collected from other research. The results were
organized in reduction of the heating consumption (%), the reduction of Carbon Emissions (%), the
grade of disruptiveness and invasiveness of each measure (low- medium and high). Table 2 shows the
percentages of reduction achieved by the measures belonging to the different building’s systems.
Table 2. Heating Consumption (%) and CE reduction (%) of the Building’s System tested in IES-VE.
Measure Heating reduction CE reduction
External wall insulation 51,2% 39,7%
Slab’s insulation 16-20% 12-22%
Mechanical ventilation
combined with
airtightness of
0.15ACH
10% 7%
Windows 5-7% 4-6%
Roof and ceiling
insulation
6-8% 4-5%
Heating system 0% 7%
Cost Analysis
In order to identify the most cost-effective and less invasive measures, it was important to compare
the costs, the savings and their grade of disruptiveness. The comparison was carried only for wall and
slab’s insulation as the measures tested varied for thickness, type of material and strategy adopted
(internal or external insulation).
The prices were found online, and on Spon’s Architects’ and Builders’ Price Book 2013, available
at the University’s Library (Langdon, 2013). The Danish prices were available on V&S Prisdata,
provided by Byggecentrum, with an annual price. For this reason, the labour prices were searched in
Spon’s, while the materials‘ costs were found on the sellers’ websites (listed in the references), and by
asking quotations to the manufacturers.
The external insulation of the wall with demolition of the cavity wall, and cavity insulation +
internal insulation were excluded from the feasible measures because highly invasive and disruptive, less
effective than the external insulation, and more expensive. Thus, the most cost-effective solutions with
the shortest payback period are the insulation of the cavity wall and an additional external insulation,
which can be between 50 and 160 mm., as shown in Fig. 2.
As shown in Fig.3 the ceiling insulation seemed to be most cost-effective than the roof insulation
because it involves a smaller surface to cover, thus lower material costs, but similar savings to the roof
insulation (6% reduction of heating demand in both cases, 4% reduction of CE for 200mm insulation and
5% for 400mm insulation). Also the ceiling insulation can be less disruptive than the roof insulation,
which would involve a disassembly of the roof cover and waterproof layer. Such measure is suggested
only in case the roof needs to be updated because it would solve a problem of thermal bridging in the
junction between the roof and the external wall.
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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Figure 2 Investment, Saving with Waste Heat and Saving with Natural Gas for Wall Insulation
Measures (£).
Figure 3 Investment, Saving with Waste Heat and Saving with Natural Gas for Roof and Ceiling
Insulation (£).
A second series of simulations was run to estimate how much the heating demand could be
reduced, once all the retrofit measures are completed. For this purpose any possible combination of
measures was tested. The ACH used were 0.3 (a medium value); in such old leaky houses a value of 0.25
ACH is hardly achievable. Among 127 simulations the heating demand varied from a maximum of 39
kWh/m2/yr, to a minimum of 20.7 kWh/m
2/yr; both results are lower than the established goal of 44
kWh/m2/yr (Danish energy class 1).
According to the results of all the IES simulations, the multi stage plan should follow the next
order: cavity insulation, external wall insulation, slab insulation, mechanical ventilation, roof and ceiling
insulation, windows and heating system.
However these dynamic simulations cannot considerate the fact that the single measures are part of
a staged plan and cannot preclude further works in the future (Thorpe, 2010).
Interview
For this reason a semi-structured interview was conducted with a NIRAS’ engineer specialized in
energy efficient retrofits. During the interview, the installation of an automatic heating control system
was recommended as first measure on the list, being a cheap and very effective solution. In fact, further
simulations confirmed that.
The time-temperature control and the time control can both lead to a 38% reduction in space
heating demand; while the temperature control only a 10% reduction. The carbon emissions were
reduced by 31% with the first two controls, and by 9% with the third one.
The engineer also evidenced how changing windows can be a priority for the occupants to enhance
0 5000 10000 15000 20000
Ext. Ins. Rockwool 50 mm…
Rockwool 100 mm
Ext. Ins. Rockwool 160 mm…
Ext. Ins. Rockwool 300 mm
Ext. Ins. Kingspan TW55-PIR
Int. Ins. Spacetherm 50 mm…
Savings with Waste Heat Savings with natural gas Investment
0 500 1000 1500 2000 2500 3000
Roof Rockwool 300mm
Roof Eco wool 300mm
Ceiling Rockwool 200mm
Ceiling Ecowool 200mm
Ceiling Rockwool 300mm
Ceiling Ecowool 300mm
Ceiling Rockwool 400mm
Ceiling Ecowool 400mm
Savings with Waste Heat Savings with natural gas Investment
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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the thermal comfort, and avoid air-drafts.
Besides, it was suggested to consider windows and external insulation as a whole package; indeed,
if the external insulation is applied first the windows should be moved to the outer layer of the wall to
avoid thermal bridges. Thus, the windows could be changed when moved, avoiding extra installation
costs.
At last, the mechanical ventilation cannot be considered as measure unless an airtightness test
proves that the infiltration rate is lower than 1,5 ACH50.
The limitations of a multi-stage retrofit were also discussed during the interview. Not all the
construction details can be solved during a multi-stage retrofit (certain thermal bridges) and these
limitations need to be accepted and explained to the owners not to create too high expectations. In fact,
the savings obtained by large scale and less expensive retrofit (nearly 80%) can still make a big
difference in reducing the gross energy consumption and the CO2 emissions of a Country.
Multi-stage plan
Based on these suggestions and considerations the final multi-stage plan was organized in 11 stages
and the measures of each stage were classified in low-medium and high budget (Table 3), The intent was
to produce a flexible scheme that leaves to the single owners the choice of the best measures for their
budget.
Table 3. Multi- Stage Retrofit Plan
Low budget Medium budget High budget
1 Automatic
heating control
Boiler control
Boiler and
time/temperature
control
Boiler, time and
temperature control
2 Cavity
insulation
75mm Phenolic
foam
75mm Eco bead
Platinum
75mm Bio-foam
3 Windows Double-glazing
1.25
Double-glazing low-e Triple glazing
4 External
insulation
50mm mineral
wool, EPS, PIR
100mm mineral wool,
EPS, PIR
160mm mineral wool, EPS,
PIR
5 Roof insulation 300mm Rock
wool, Ecowool
400mm rock wool,
Ecowool
Renovation of the whole
roof and placement of 340-
400mm insulation on the
external side of the roof.
6 Basement
insulation
200mm
Rockwool,
Ecowool,
cellulose
insulation
300mm Rockwool,
Ecowool, cellulose
insulation
400mm Rockwool,
Ecowool, cellulose
insulation
7 Slab insulation 160mm XPS
insulation on top
of the existing
slab
250mm XPS
insulation under the
new slab
300mm XPS insulation
under the new slab
8 Basement
insulation
50mm insulation 100mm insulation
9 Insulation/new
external doors
50mm insulation New insulated doors
10 MVHR High efficiency Most efficient MVHR
model
11 Heating system Gas boiler District heating Ground Source heat pump
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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The list of measures was accompanied by a scheme, shown in Fig.4, with questions and answers
(yes/no) that show which is the first stage to undertake and which should follow. For each stage there is
a corresponding color, that remands to the first scheme of measures.
Figure 4 Guiding Scheme to House owners.
Possibilities to finance energy efficient retrofits
If the financing barrier is to be overcome, the annual cost of energy renovation investment should
at least be equal to the annual savings on energy (Kragh and Rose, 2011), and at the moment, even with
the increased energy price, the payback period for energy retrofits is still too long.
In this research an existing tax deduction was used to abolish or reduce the difference between
investments and energy savings as shown below :
𝐴𝑛𝑛𝑢𝑎𝑙 𝐼𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡 = 𝐴𝑛𝑛𝑢𝑎𝑙 𝐸𝑛𝑒𝑟𝑔𝑦 𝑆𝑎𝑣𝑖𝑛𝑔𝑠 + 𝐴𝑛𝑛𝑢𝑎𝑙 "𝐴𝑟𝑡𝑖𝑠𝑎𝑛 𝐷𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛"
The so called “artisan deduction” consists of about £2000 per salary/yr, to deduce for installation
and craftsmen costs, but not for materials and devices costs (SKAT), which account for half of the total
investment. In this research it is assumed a modification of the tax scheme, allowing the homeowners of
a specific category to deduce also materials and devices’ costs.
Another assumption is that the annual savings on energy are cumulated and saved in a bank
account with exclusive use for the next stage, until the whole retrofit is completed.
In Denmark detached houses are often occupied by one or two families, in which case there could
be two, three or four salaries that could bring £3496-£5244 of tax deduction per year/house.
A scheme showing the investment, the energy and carbon savings and the tax deduction for 1,2,3
and 4 salaries was created to verify the workability of the new “artisan deduction” and the cumulated
energy savings. The final equation is:
𝐴𝑛𝑛𝑢𝑎𝑙 𝐼𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡 = ∑ 𝐸𝑛𝑒𝑟𝑔𝑦 𝑆𝑎𝑣𝑖𝑛𝑔𝑠
𝑛
𝑛−1
+ Artisan Deduction
n=number of the years since the first retrofit stage
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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Where the result is negative, the investment is paid back in the same year of realization, through the
monetary savings obtained by reducing the energy demand and the incentives. When the difference is
positive, the incentives and the monetary savings are lower than the initial investment. In the first case, it
could be possible to carry one or more measures during the given year, depending on how much of the
incentive is left. In the second case the measures too expensive to be paid in one year, should be carried
out in two or more years (i.e. windows can be changed one at a time). Another solution is to wait a
couple of years, save the money not spent for heating, and use it to pay in a single shot the works.
In order to estimate the number of years necessary to carry on the whole retrofit, every time the
difference was negative, a new calculation was done adding the cost of the next measure and the savings
achievable from that. If the difference was still negative the two or more measures could be carried out
the same year.
In all cases the first two steps can be completed in one year. The window replacement can require
one or two years with one salary, and one year for the other three cases. Only with four salaries per
household the windows could be replaced at the same time when adding external insulation. The next
steps can be completed in five years with one salary, for a total of seven years, in case the house is
connected to the district heating; and twelve years if there is a heat pump. In case the salaries in the
house are two, the retrofit could be completed in six-seven years. if there are three salaries four-five
years could be enough to complete the retrofit; four with the district heating and five with a heat pump.
Table 1. Multi-Stage Plan. Number of Years for Each Stage.
1 2 3 4 5 6 7 8 9 10
Year of
retrofit
Automatic
Control
Cavity
Ins.
Window Ext.
Ins.
Roof
Ins.
Slab Door MV Boiler Heating
System
1 salary Yr 1 Yr 1 Yr 2-3 Yr 4 Yr 5 Yr 5 Yr 5 Yr 6 Yr 7 Yr 7-12
2 sal. Yr 1 Yr 1 Yr 2 Yr 3 Yr 3 Yr 4 Yr 4 Yr 4 Yr 5 Yr 6-7
3 sal. Yr 1 Yr 1 Yr 2 Yr 3 Yr 3 Yr 3 Yr 4 Yr 4 Yr 4 Yr 4-6
4 sal. Yr 1 Yr 1 Yr 2 Yr 2 Yr 3 Yr 3 Yr 3 Yr 4 Yr 4 Yr 4-6
Incentives plan to retrofit the detached houses built between 1851 and 1931 by 2030
Supposing the national mass retrofit starts in 2015 detached houses between 1850 and 1930, all the
houses with three or four salaries could be completed in 4-6 years. In 2020 the next stage of the mass
retrofitting could start with the houses built between 1961-1972. By 2027 the first stage should be
concluded and the 11 % of the whole Danish housing stock retrofitted (Fig.5) with 80% energy
reduction. As shown in Fig.69 this group of houses accounts about the 31% of the energy used by
detached houses, so the 80% reduction would be equal to 24% reduction of detached-houses’ energy use.
CONCLUSIONS
This paper has investigated the possibility of using a multi-stage plan to overcome economic and
practicality barriers to energy efficient housing retrofit. The research results have shown that the
integration of dynamic simulations and the practical experience of specialists can lead to multi-stage
retrofit plans for each housing type.
A financing scheme was proposed to equal the annual investment for retrofit, to the derived energy
savings; however, a similar model would be burdensome for the national tax system; which would see
the national tax income considerably reduced. On the other hand, without a significant help from the
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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government, only a few house owners would invest their own savings in such housing retrofit, as “one of
the main barriers in renovation” is “financing” (Kragh and Rose, 2011, p. 2252).
Figure 5 Sample of Mass Retrofit Organization.
Most of them would probably decide to upgrade something, not aware of what they could actually
do to have an energy efficient house. In conclusion this research suggests that government guidance is
essential as government funding schemes. The proposal of recouping a percentage of the monetary
savings achieved by the house holders to help the government to finance the second step could make the
scheme unpopular, if the advantages derived from such help are not well stated. Nevertheless, this
scheme does not require any investment to the owners, which have only to pay upfront.
Educating the householders about the long term and non-monetary advantages is critical to their
acceptance of the scheme. This research has shown how tax-related schemes can encourage retrofit
initiatives and how technical solutions can help reduce the cash flow and capital cost. Other technical
solutions and financial incentives could address these and other barriers to retrofit initiatives and should
be further investigated. In addition, all incentive schemes need to be supported by effective information
and this area could also benefit from further research.
AKNOWLEDGMENT
This paper is based on a dissertation for the MSc in Sustainable Building Performance and Design,
offered by Oxford Brookes University.
We would like to thank those who have taken part in the project, Andrew Ferguson Dunn, Jørgen
Søndermark , Diana Ricco, Hu Du.
2015
year 1
•The "artisan deduction" includes the material costs only for the owners of detached houses built between 1851-1930.
•This housing stock starts being renovated at the same time.
2019-2021
year 4-6
•The houses with 3-4 salaries should be completed.
•The house owner of the renovated houses give a percentage of the annual energy savings back to the government.
2020
year 5
•The "artisan deduction" for the completed houses is back to the original formula.
•Houses built between 1961-1972 start being renovated with the percentage of the savings from the houses already renovated.
2022
year 7
•Most of the houses are renovated if the district heating is preferred to the ground source heat pump.
•As long as the houses are completed the next category of houses is gradually renovated following the previous scheme.
2027
year 12
• 23% of detached houses should be renovated, saving about 80% of the energy.
•11% of the total existing housing stock would be retrofitted.
30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad
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REFERENCES
Aggerholm, S., Engelund, K., Wittchen, K. 2010. Implementation of the EPBD in Denmark. In:
Implementation of the EPBD. Brussels: Publication office of the European Union. pp. III-91-
102.
Capros, P., Mantzos, L., Tasios, N., De Vita, A., Kouvaritakis, N. 2010. EU Energy Trends to 2030.
Update 2009. Publication Office of the European Union. Luxembourg: Publications Office of
the European Union. Danish Energy Agency. 2011. Energy in Denmark 2011. Available at: http://www.ens.dk/en-
us/info/factsandfigures/energy_statistics_and_indicators/annual%20statistics/sider/forside.aspx
(Accessed: 15 April 2013)
Statistics Denmark. Statistics residential housing stock-all Denmark-before 1900 to 2012. Available
at: www.dst.dk (Accessed: 15 April 2013)
Galiotto, N., Heiselberg, P., Knudstrup, M.A. 2012. Examples of Nearly Net Zero Energy Buildings
through One-step and Stepwise Retrofits. In: Passivhus Norden 2012. Trondheim. 21-23
October.
Häkkinen, T., Ruuska, A., Vares, S., Pulakka, S., Kouhia, I., Holopainen, R. 2012. Methods and
concepts for sustainable renovation of buildings. VTT-Technical Research Center of Finland.
Espoo.
Kragh, J., Rose, J. 2011. Energy renovation of single-family houses in Denmark utilising long-term
financing based on equity. Applied Energy, 88. pp. 2245–2253
Langon, D. 2013. Spon’s- Architects’ and Builders’ Price Book 2013. 138th edition. London:
Spon.
Larsen, T.S., Maagaard, S., Jensen, R.L. 2011. Renovation of a detached single-family house into
an energy efficient low energy house. In: 9th Nordic Symposium on Building Physics. Tampere.
29 May-2 June. Tampere University of Technology: Department of Civil Engineering. pp. 305-
312 Ministry of Climate, Energy and Building. 2012. Energy policy report 2012. Available at:
http://www.ens.dk/en-US/policy/danish-climate-and-energy-
policy/Documents/Energy%20Policy%20Report%202012.pdf (Accessed:15 April 2013).
OIS DK. Available at: www.ois.dk (Accessed 15 April 2013)
Roadmap 2050. Available at: http://www.roadmap2050.eu/project/roadmap-2050 (Accessed: 15
June 2013)
SKAT. Artisan deduction. Available at:
http://www.skat.dk/SKAT.aspx?oId=1947018&vId=0&lang=DA
Statistics Denmark. Waste heat prices updated to March 2013. Available in Danish at:
http://energitilsynet.dk/fileadmin/Filer/0_Nyt_site/VARME/Prisstatistik/2013/Prisstatistik_mar
ts_2013.pdf
Thorpe, D. 2010. Sustainable Home Refurbishment. London: Earthscan Ltd. V&S Prisdata. Available at: www.byggecentrum.dk/data-og-software/vs-prisdata/ (Accessed: 28 August
2013)
Wittchen, K.B., Kragh, J. 2012. Danish Building Typologies. Participation in the TABULA Project.
Danish Building Research Institute, Aalborg University.
IEA sustainable building center. Available at: www.sustainablebuildingscenter.org
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