Every day, more than 22,000,000 m³ of hot water are consumed by European homes alone. It is a major source of energy consumption for new housing, and yet 80 percent of this heat ends up in sewers and is wasted. Considering hot water is mostly used in showers, recovering waste heat from shower drains could be a simple way to save up to 70 percent wasted energy and related CO2 emissions.

1. Low hanging fruit in decarbonisation of buildings?
Wastewater Heat Recovery (WWHR) systems
Robert Pintér, European Copper Institute, Green and Healthy Buildings Team
Leonardo ENERGY Webinar, 26 November 2020, 13:00 CET

2. Content
1. INTRODUCTION
2. HOW WASTEWATER HEAT RECOVERY (WWHR) WORKS
a) PRINCIPLE
b) EFFICIENCY
3. CURRENT MARKET SITUATION
4. EVALUATION OF WWHR POTENTIAL FOR DECARBONISATION
a) HOUSEHOLD LEVEL: A SAMPLE CALCULATION OF
ANNUAL ENERGY CONSUMPTION AND EMISSIONS OF A
CHOSEN SHOWER SYSTEM WITH AND WITHOUT WWHR
b) EU-28 LEVEL: ENERGY CONSUMPTION AND CO2
EMISSIONS OF SHOWERS, SAVINGS WITH WWHR
c) 2030 WWHR SCENARIO – ENERGY SAVING POTENTIAL IN
2030 (Renovation Wave)
5. ADDITIONAL BENEFITS OF WWHR SYSTEM
6. POLICY RECOGNITION NEEDED FOR WWHR
| Wastewater Heat Recovery (WWHR) systems2

3. Introduction
• EC: buildings are responsible for
approximately 40 percent of energy
consumption and 36 percent of CO2
emissions in the EU
• New built sector: growing share of energy to
produce hot water, dramatic fall in energy
needed for space heating
• Daily 22 million m3 hot water used in EU
homes
• 80 percent of the heat ends up in sewers
• Up to 70% of energy wasted in shower drains
can be cost effectively and simply recovered
| Wastewater Heat Recovery (WWHR) systems3

4. Growing share of energy for hot water
production (Switzerland)
| Wastewater Heat Recovery (WWHR) systems4
Source: https://joulia.com/

5. How WWHR works?
• No moving parts, no electricity required (mostly)
• A heat exchanger transfers heat energy of wastewater to incoming fresh
water supply and warming it from around 10 up to 30°C
• Why showers?
• Highest consumption of hot water (≈ 80%)
• Hot water demand and drain water available simultaneously
• Easy heat exchange
• Relatively unpolluted wastewater, ideal for heat exchange
• A wastewater heat recovery system could effectively recapture and reuse
instantly up to 70 percent of waste energy, reducing energy consumption
in a cost-effective manner.
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6. Basic Principle
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Fresh water incoming at 10°C preheated to 30°C arriving at the
mixing valve, reducing the need for hot water from the boiler.
For more schemes (individual and
multi-dwelling solutions) see the
White paper

7. Product examples
Horizontal type heat exchangers
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8. Product examples
Vertical type heat exchangers
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9. Installation
Plumber connects:
• potable water in- and
outlets (preheated)
• Drainage out- and inlet
(vertical)
For manufacturers, product
specifications visit:
WWHR Europe
| Wastewater Heat Recovery (WWHR) systems9

10. Product safety
In WWHR systems double-walled heat exchangers are required by EN 1717
“Protection against pollution of potable water in water installations and
general requirements of devices to prevent pollution by backflow”.
Double-walled tubes ensure that domestic hot water and grey water are
reliably separated. Moreover, the standard-compliant leakage gap makes it
possible to detect leakages.
| Wastewater Heat Recovery (WWHR) systems10

11. Efficiency
• The lower the flow rate, the higher the efficiency – the higher the flow
rate – the higher the performance.
• Efficiency, as a percentage of energy gained from drain water varies by
systems used, up to the value of around 70 percent.
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Vertical type heat exchanger with over 60% efficiency.

12. Efficiency
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13. Where to use WWHR
systems?
Residential
• single family houses
• multifamily houses
Non-residential with higher hot water
consumption
• sport facilities, hairdressers, hotels,
swimming pools…
Due to ease of installation ideal for also for
renovation.
| Wastewater Heat Recovery (WWHR) systems13

14. Current market situation
• Europe has the greatest technological lead in the world on this subject,
with 326 patent applications since 2010, which is 70 percent of all patent
applications in the world.
• Together, WWHR systems have already recovered 300 GWh
corresponding to the annual domestic hot water consumption of 17,000
households.
| Wastewater Heat Recovery (WWHR) systems14

15. Acknowledgement of WWHR technology in
national building codes and standards
• France: RT2012 and forthcoming RE2020 where WWHR can contribute to
targets for heat from renewables.
• The Netherlands: WWHR systems are included in the calculation
software for new construction projects as they have a positive bearing
on the energy performance of a building.
This is the case for the existing EPC (energy performance certificate)
regulation. It will also be the case with the BENG (nearly energy neutral
buildings) regulation that will be used from 01 January 2021.
• UK: In October 2019, the Ministry of Housing, Communities and Local
Government (MHCLG) published a consultation on the Future Homes
Standard, regarding changes to Part L of the Building Regulations for
new dwellings. WWHRS is widely recognised as one of the most cost-
effective SAP-listed energy efficiency technologies available, and
proposed changes to Part L in 2020 suggest WWHRS will have an even
bigger impact under the new regulations.
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16. Energy and CO2 emissions calculation of a
sample household
Energy consumption and emissions of shower systems depend on many
variables, e.g. temperature of incoming cold, hot water and shower water
used, shower time, fuel used to heat water (electricity, gas…) size/design of
shower enclosure and flow rate. In our example:
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Shower time: 9 min./shower
Cold water temperature: 10°C
Hot water temperature from the boiler: 60°C
Mixed shower water temperature: 38°C
Flow rate: 9.2 l/min
Number of days: 365
Number of residents per home: 2.30
CO2 emission coefficient (based on Dutch standard NTA8800, “Energy
performance of buildings - Determination method):
Electricity: 0.34 kg/kWh
Gas: 0.183 kg/kWh
WWHR unit efficiency: 56% (market average)

17. Energy and CO2 emissions calculation of a
sample household
In this sample household, with deployment of an average efficiency (56%)
WWHR system, 833 kWh electrical energy and related 283 kg of CO2
emissions can be saved, or consumption of 85 m3 natural gas, equivalent to
153 kg CO2 can be avoided.
37% of energy consumption and CO2 emissions avoided
| Wastewater Heat Recovery (WWHR) systems17
Household Without WWHR Household With WWHR
Household Saving with
WWHR
Hot water
preparation
Energy
demand
per year
CO2
emissions
per year
Energy
demand
per year
CO2
emissions
per year
Energy saving
per year
CO2
emissions
saving
per year
Electricity 2,264 kWh 770 kg 1,430 kWh 486 kg 833 kWh 283 kg
Gas 231 m3/year 414 kg 144 m3/year 262 kg 85 m3/year 153 kg

18. RETURN ON INVESTMENT
• Electricity and natural gas prices vary across
Member States and there is a wide range of
WWHR systems available on the market, so the
exact return on investment needs to be
calculated specifically for each project.
• An average family can save around €50-150
annually on their hot water bill after
deployment of a WWHR unit and this justifies
the investment into this safe, energy efficient,
environmentally friendly, simple, and easy to
install, operate and maintain system with a
long lifespan.
| Wastewater Heat Recovery (WWHR) systems18

19. EU 28 Energy Statistics, 2017
19
Item Value
Energy for domestic hot water preparation 495 TWh
Share of hot water used for shower out of total hot water used in
households (see table below)
80%
Energy for shower hot water in households 396 TWh
Final energy consumption 12 329 TWh
Household's final energy consumption 3 344 TWh
Share of hot water in households final energy consumption 14,8%
Share of hot water used for shower in final energy consumption 3,21%
Use of hot water in households according to JRC report “MEErP Preparatory Study on Taps and Showers” Share
Bath 6%
Shower 80%
Tap, washbasin 7%
Tap, kitchen - drinking/cooking 0%
Tap, kitchen - dish washing 5%
Tap, indoor - clothes washing 2%
Tap, indoor - other uses 0%
Outdoor 0%
Total hot water demand in taps and showers 100%
| Wastewater Heat Recovery (WWHR) systems

20. Energy demand and carbon footprint of
shower hot water in the EU / saving potential
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Type of fuel Share (2017)
Gas 47%
Electricity 19%
Oil and petroleum products 11%
Derived heat 11%
Solid fuels 2%
Renewables and wastes 10%
Share in
heating
shower hot
water
Energy
Demand
Total
(TWh/y)
Saving
potential
with WWHR
(37%)
(TWh/y)
CO2
emission
coefficient
(NTA 8800)
kg/kWh
CO2
emissions
(million
tonnes/y)
Saving
potential
with WWHR
(37%)
(m. t./y)
Electricity 19% 74.89 27.21 0.34 25.46 9.92
Gas 47% 189.91 70.27 0.183 34.75 12.86
TOTAL 264.81 97.98 60.22 22.28
66%

21. 2030 WWHR SCENARIO – ENERGY SAVING
POTENTIAL IN 2030
By 2030:
• Renovation Wave Strategy: 35 million buildings renovated (82%
residential)
• New dwellings: 16 million completed
2030 WWHR scenario:
annual savings in 2030 if WWHR deployment rate is 50%
| Wastewater Heat Recovery (WWHR) systems21
Renovated Newly built
Number of dwellings by 2030 28 700 000 16 000 000
2030 WWHR Scenario – number of dwellings by 2030
(50 percent of dwellings deploying WWHR)
14 350 000 8 000 000
Household annual energy saving (kWh/year)
See household level table
800 800
Total annual energy savings in 2030 (TWh/year) 11.48 6.40
Grand total energy savings in 2030 (TWh/year) 17.88
Grand total energy savings in 2030 (Mtoe/year) 1.54

22. Energy and GHG emissions savings by
Renovation Wave Communication
„The Commission has proposed in the Climate Target Plan 2030 to cut net
greenhouse gas emissions in the EU by at least 55% by 2030 compared to
1990.”
„To achieve the 55% emission reduction target, by 2030 the EU should
reduce buildings’ greenhouse gas emissions by 60%, their final energy
consumption by 14% and energy consumption for heating and cooling by
18%” (compared to 2015)
| Wastewater Heat Recovery (WWHR) systems22
GHG and final energy savings in
buildings
Final Energy
Consumption (Mtoe)
-14% (2030 vs. 2015)
GHG
(Mton CO2-eq)
-60% 2030 vs. 2015)
2015 370 456
2030 (BSL scenario) 334 239
2030 Green Deal (REG scenario) 320 180
Savings needed 50 276

23. Contribution to 2030 targets of the
Renovation Wave – 2030 WWHR scenario
| Wastewater Heat Recovery (WWHR) systems23
Share of WWHR in final energy savings
target of the RW: 3.07%
WWHR contribution (1,54 Mtoe)
Share of WWHR in GHG emissions
savings target of the RW: 8.07%
WWHR contribution (22,28 Mt)

24. Additional Benefits
• Hot water preparation system can be designed smaller
• Reduced capacity of installed renewable systems (photovoltaic, solar
thermal or heat pumps) or renewable energy generated on site can be
used for other purposes than hot water.
• Circular construction: systems have a long lifespan and contain easy to
recycle and highly recycled materials (copper, stainless steel).
• Real time production: the recovery and generation of energy adapt
continuously and in real time with the usage, without over-or under-
production (no storage and control system necessary)
• Aesthetics: systems are integrated into showers, in ducts or technical
rooms, so they are hidden.
| Wastewater Heat Recovery (WWHR) systems24

25. Policy recognition needed for WWHR
Foster use of systems
 EPBD article 2: WWHR to be defined as „energy from renewable sources”.
 EPBD to recognise WWHR as energy source generated on-site in primary
energy factors used for the determination of the primary energy use expressed in
kWh/m2/year with the aim to take contribution of WWHR to energy savings into
account. In the definition of NZEB, recognition is needed that WWHR can reduce hot
water needs.
 EPBD to introduce a building renovation passport (as proposed in the
Renovation Wave) to provide long-term, step-by-step renovation roadmap, explicitly
including WWHR systems.
 EPBD to introduce minimum energy performance standards for existing
buildings (as proposed in the Renovation Wave), to reach a minimum renovation
rate, consider WWHR in calculations
 EPBD to introduce a ‘deep renovation’ standard (as proposed in the Renovation
Wave), explicitly including WWHR.
 RED (or/and EPBD) to introduce requirement to use „Minimum levels of
renewables in buildings” (as proposed in the Renovation Wave), facilitate use of
waste heat at building level, take WWHR contribution into account
Energy
Performance
of Buildings
Directive
Renewable
Energy
Directive
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26. Policy recognition needed for WWHR
Foster use of systems
 Energy labelling: package label for heating systems: possibility to include WWHR as
a subsystem in the label (next to solar collectors, storage tanks, controllers, …)
Ecodesign and
Energy
Labelling
 Article 14 (Promotion of efficiency in heating and cooling): Member States shall
include wastewater heat recovery systems in buildings in their energy efficiency and
renovation programs (Long Term Renovation Strategies).
Energy
Efficiency
Directive
| Wastewater Heat Recovery (WWHR) systems26

27. Locker room showers : one collective
WWHRS or multiple individual WWHRS ?
Case study: Public swiming
pool in Cernay, France.
Built in 2020
34 showers
Hugo Durou, European Association for WWHR, Nov. 26th 2020

28. individual WWHR
260mm
450 mm
460 mm
isometric view
Obox

29. WWHR
showers 1 & 2
cold water
water
heater
cold water
mixer
overflow
drain
WWHR
showers 3 & 4
cold water
mixer
WWHR
showers ...
cold water
mixer
drain
WWHR
showers 33 & 34
cold water
mixer
overflow overflow overflow
individual WWHR
× 17
Obox

30. collective WWHR
grey
water
grey
water
to sewerSupporting poles
Load = 100 kg
black
water
758
753
803mm
147 mm
Obox C

31. collective WWHR
shower room #1
water
heater
mixer
shower room #2
mixer
shower room #3
mixer
drain
WWHR
shower room #4
cold water
mixer
overflow
cold water
Obox C

32. énergie
perdue dans
les tubes avant
Obox C
23%
énergie
perdue parce
que montage
"ballon seul"
26%
énergie
perdue parce
que Obox C n'a
pas 100%
d'efficacité
18%
énergie
récupérée par
Obox C
33%
individual WWHR collective WWHR
Energy lost in pipes before Obox C 27,3 MWh/yr
Energy because preheating only water to water heater 30,6 MWh/yr
Energy lost because Obox C has not 100% efficiency 21,3 MWh/yr
- Energy recovered 39,8 MWh/yr
Energy lost before Obox 16,8 MWh/yr
Energy lost because preheating only water to shower mixer 34,1 MWh/yr
Energy lost because Obox has not 100% efficiency 15,7 MWh/yr
- Energy recovered 52,4 MWh/yr
Energy lost in
pipes before
Obox C
Energy lost
because
preheating only
water to water
heater
Energy lost
because Obox C
has not 100%
efficiency
Energy
recovered
énergie
perdue dans
les tubes avant
Obox C
14%
énergie
perdue parce
que montage
"ballon seul"
29%
énergie
perdue parce
que Obox C n'a
pas 100%
d'efficacité
13%
énergie
récupérée par
Obox C
44%
Energy lost in
pipes before
Obox
Energy lost because
preheating only
water to shower
mixer
Energy lost
because Obox
has not 100%
efficiency
Energy
recovered
× 17

33. Energy recovered 39,8 MWh/yr
Hot water energy reduction -33%
Cost (WWHRS hardware) 8 433 €
Cost (installation) 1 200 €
Payback / ROI 3,3 yr
Energy recovered 52,4 MWh/yr
Hot water energy reduction -44%
Cost (WWHRS hardware) 9 846 €
Cost (installation) 6 000 €
Payback / ROI 4,1 yr
individual WWHR collective WWHR
× 17

34. Robert Pinter, European Copper Institute
robert.pinter@copperalliance.org
Hugo Durou, European Association for WWHR
hugo.durou@ehtech.fr
Thank you
| Presentation title and date34
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