Heating for low to radiators - Purmo
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The guide
the guide to radiators FOR low temperature heating systems
to radiators
for low
temperature
Rettig Belgium NV
heating
DM023030150602 - 02/2012
Vogelsancklaan 250, B-3520 Zonhoven
Tel. +32 (0)11 81 31 41 Fax +32 (0)11 81 73 78
info@radson.com www.radson.com
Every care has been taken in the creation of this document. No part of this document
may produced without the express written consent of Rettig ICC. Rettig ICC accepts
no responsibility for any inaccuracies or consequences arising from the use or misuse
of the information contained herein.why this guide?
Why this guide? This guide aims to give an overview of low temperature
heating systems, their benefits, use, and overall contribu-
tion to lowered energy use across Europe.
It contains contributions from a number of academics
and opinion leaders in our industry, and includes detailed
research into the use of radiators in energy efficient
heating systems.
The guide is intended for use by wholesalers, installers and
planners, to help with making informed decisions about the
choice of heat emitters in new builds and refurbished
houses.
3INDEX
turning
Why this guide 3
Contents 5
A Interview with Mikko Iivonen 6
energy into
1 It’s time to change our way of thinking 10
2 How insulation influences heating efficiency 20
efficiency
B Interview with Professor Christer Harryson 34
3 The increasing use of low temperature water systems 38
C Interview with Professor Dr. Jarek Kurnitski 54
4 Significant proof 58
5 Choosing a heat emitter 72
D Interview with Elo Dhaene 78
6 Benefits to the end user 82
4 5interview with mikko Iivonen | A
Ifigures
turn into
results
As Director of R&D, Research and Technical Standards in Rettig ICC, I am responsible for provid-
ing all our markets with new answers, insights, innovations, products and results. All our efforts
are based on realistic and independent research conducted in close co-operation with leading
industry figures and academics. This has recently included Prof. Dr. Leen Peeters (University of
Brussels - Belgium), Prof. Christer Harrysson (Örebro University - Sweden), Prof. Dr. Jarek Kurnitski
(Helsinki University of Technology - Finland), Dr. Dietrich Schmidt (Fraunhofer Institut – Germany)
and many others. With their help, research and insight, I turn figures into results.
M. Sc. (Tech) Mikko Iivonen,
Director R&D, Research and Technical Standards Rettig ICC
6 7interview with mikko Iivonen | A
Clever heating By investing heavily in research and development, we live European member states are on a fixed deadline to create 20/20/20
solutions up to our promise to provide you with clever heating solu- and enforce regulations to meet Energy Efficiency Goals for
tions. Solutions that make a real difference in terms of cost, 2020 (Directive 20/20/20). This involves reaching a primary
It is possible to comfort, indoor climate and energy consumption. Solutions energy saving target of 20% below 2007 levels, reducing Primary energy
save up to 15% that make it possible to save up to 15% on energy. With greenhouse gases by 20%, and a determination that 20% of saving target of
on energy that in mind, I would like to share with you the results of gross final energy has to come from renewable energies. For 20%, reducing
greenhouse gases
an extensive one-year measurement study conducted by building owners tasked with providing ever more impressive
by 20% and 20% of
Professor Harrysson. The study involved 130 large and small Energy Performance Certificates, it is more important than gross final energy
Swedish family houses and shows that the heating energy ever to choose a heating system that offers proven improve- has to come from
consumption of underfloor-heated buildings is 15-25% ments in energy efficiency - radiators in a low temperature renewable
higher than in radiator-heated buildings. That’s not surpris- system. These targets concern particularly buildings, which energies
ing, but it also shows that the increased energy efficiency consume 40% of the total energy used in Europe.
of modern buildings has once again put low temperature
heating systems firmly in the spotlight. Energy
Excess
consumption
Heat demand
temperature
kWh/
∆T m2a
Because of stricter As you can see in Fig. A.1 and A.2, the design temperatures
o
C 240 of buildings
60 *90/70/20 continues
requirements, the of radiators have decreased over the years in accordance with German Development
to fall.
building envelope the building energy requirements. As building and insulation
50
*70/55/20
* same size radiator
180
becomes easier 40
requirements have become stricter across Europe, the building
to heat
120
30 *55/45/20
envelope becomes easier to heat, since less heat escapes.
20 *45/35/20
Furthermore, with the excellent responsiveness of a radiator
100
10
system, it is now more practical than ever to make the most
0 120 90 60 30 0 W/m2
of heat gains in the home and office. 120 90 60 30 0 W/m2 1977 WSVO84 WSVO95 EnEv02
EnEv09
specific
heat load
specific heat load EnEv12
NZEB
Fig. A.1 Fig. A.2
Radiator design temperatures have fallen Space heating demand – specific heat load diagram
in accordance with the lowered heat loads for approximation purposes
of buildings.
8 9it’s time to change our way of thinking | 1
chapter 1 Energy regulation is a key priority for everyone, particularly
where buildings are concerned. Homes and offices across
Europe are subject to strict regulations regarding energy
Energy regulations
performance, with EU directives EPBD 2002/91/EC and
it’s time to EPBD recast 2010/91/EC requiring certification of energy
consumption levels for owners and tenants. As well as this,
change
European member states are on a fixed deadline to create
and enforce regulations to meet Energy Efficiency Goals for
2020 (Directive 20/20/20).
There are different national regulations across Europe, with There are different
our way of thinking targets for improvement of energy performance agreed in
the EU individually for each of the Member States. Despite
national regulations
across Europe for
improvement of
• Energy regulations > There are different national the varying targets and measurements in each country, the
energy performance
regulations across Europe for improvement of energy overall trend throughout Europe is to reduce levels of
performance energy consumption.
• Renewable energy targets > Strict targets have placed
significant pressure on building owners to reduce
energy use
• Innovation of radiators > Reducing the water content
and placing the fins in contact with the hotter channels
has increased thermal output. With today’s designs, the
material is up to 87% more efficient than in traditional
models
10 11it’s time to change our way of thinking | 1
Examples of As you can see below, and on the following pages, some There is growing public concern about the environment, Examples of
renewable energy targets are incredibly strict, with the underlying trend that and increasing consumer preference for environment- reduction targets
targets the use of renewable energies and reduction of greenhouse friendly products and processes. It is clearly time to
gases has been massively prioritised. re-evaluate the way the heating industry works, as
guidelined by Ecodesign directive ErP 2009/125/EC. Our Our responsibility
responsibility to end-users is to provide the most energy- is to provide the
Finland: from 28.5% - up to 39% efficient and cost-effective way to create a comfortable most energy-
efficient and
France: from 10.3% - up to 23% indoor climate. Although a number of different heating
cost-effective
Germany: from 9.3% - up to 18% solutions are available, there is continuing confusion about way of creating a
UK: from 1.3% - up to 15% which to choose. comfortable
Sweden: from 39% - up to 49% indoor climate
In order for end-users installers and planners to make an
informed choice, it is important that accurate information
Strict targets have This has placed significant pressure on building owners to on heating solutions is made available. As of the use of low
placed significant find ways to minimise their energy use, and not just to temperature central heating systems continues to grow,
pressure on comply with governmental regulations (Fig. 1.1). Across Radson has created this guide to explain the growing role
building owners
Europe, the push towards efficiency is affected by a that radiators have to play in the heating technology
to minimise
energy use number of other variables. Fossil fuel prices continue to rise, industry today.
as the dwindling supplies of oil, coal and gas become
increasingly valuable resources.
12 130,4 100
20
0,2
0 0 it’s time to change our way of thinking |01
1990
1995
2000
2005
2010
2015
2020
2025
1961
1979
1995
2006
2010
2015
2020
2002
Year Year
Building stock average
Fig. 1.1
The Netherlands The Nederlands United Kingdom Denmark Belgium
The Nederlands The Nederlands Denmark Denmark 1,6 United Kingdom
Norway United Kingdom 400 Belgium 100%
kWh/m2
EPC
Roadmap of some coun- 1,6 1,6 400 400The Nederlands 100% 100% Denmark United Kingdom 300
kWh/m2
kWh/m2
EPC
Energy consumption, kWh/m2a
Requirement %
1,4
Primary energy demand-heating, kWh/m2a
EPC
1,6 400 100%
tries towards nearly zero Existing buildings Target values of
kWh/m2
EPC
1,4 1,4 Carbon emission 80
Target values of 1,2 Carbon emission
300 120 250
1,4 Target values
80 of 80 energy consumption
Carbon emission
energy buildings to impro- 1,2 1,2 300 300 1,0
207
relative to 2002
TEK97 Revision
Target relative to 2002 Revision
values of 80
100 200
1,2 energy consumption energy consumption 300 relative to 2002 Revision 60 S
ve the energy performance 1,0 1,0 600,8 165 60
TEK07
energy consumption 200
1,0 TEK2012 80 150
of new buildings. 0,8 0,8 200 200 0,6 130
60
40
0,8 200 TEK2017 60 100
0,6 40 100 40
0,6 0,4 100
0,6 TEK2022 40 Flanders Brussels Valloria
40 20 50
REHVA Journal 3/2011 0,4 0,4 100 100 200,2 65
20
Equivalent thermal insulation requirements Researc
0,4 100 TEK2027 Legal EPB-requirements (Demon
0,2 0,2 30 20
20 0
0,2 0 0 Policy intentions 0
0 0 0 0 0
1990
1995
2000
2005
0
19792010
2015
2020
2025
1961
1979
1995
2006
2010
2015
20162020
2002
2004
2006
0 0 -50
0 0 0
1990
1995
2000
2005
2010
2015
2020
2025
1961
1979
1995
2006
2010
2015
2020
2002
2004
2006
2008
2010
2012
2014
2016
2018
2020
1990
1995
2000
2005
2010
2015
2020
2025
1961
1979
1995
2006
2010
2015
2020
2002
2004
2006
2008
2010
2012
2014
2016
2018
2020
1997
2007
2012
2017
2022
2027
1984
1988
1992
1996
2000
2004
2008
2012
2016
2020
1980
1990
1995
2000
2005
2010
2015
2020
2025
1961
1995
2006
2010
2015
2020
2002
2004
2006
2008
2010
2012
2014
2018
2020
Year Year
Building stock average
Year Year stock average Year Year Year Year Year Year
Building Building stock average Year Year Year
Building stock average
Denmark Norway Germany Deve
The Nederlands Denmark United Kingdom Development of Energy-saving
Norway Development of Energy-saving Belgium
Development of Energy-saving
1,6 Norway
400
kWh/m2
Norway Belgium
100% Belgium Construction Construction Construction 300
EPC
Norway Belgium
Energy consumption, kWh/m a
Requirement %
Primary energy demand-heating, kWh/m2a
Primary energy demand-heating, kWh/m2a 2
1,4 300 Existing buildings 300
Carbon emission
Energy consumption, kWh/m2a
Requirement %
300
Energy consumption, kWh/m2a
Requirement %
1995 Primary energy demand-heating, kWh/m2a
Minimum requirements Minimum requirements120 250
Target values of
Energy consumption, kWh/m2a
Requirement %
2010 Primary energy demand-heating, kWh/m2a
80 Minimum requirements
1,2 Existing buildings 300 Existing buildings 120 Existing120
buildings relative to250
2002
207 Revision (WSVOVEnEV) (WSVOVEnEV) (WSVOVEnEV)
120
TEK97 250
207 207
energy consumption 100 250 200 Solar houses
1,0 TEK97 TEK97 100
207 200 TEK07
200 60
TEK97
100
Solar houses 200 165 Solar houses
100
TEK07 TEK07 80 Solar houses 150 Build
0,8 200 TEK2012 TEK07
165 165 80 165 130
150
80 Building practice 150 Building practice
0,6 130
TEK2012
130
TEK2012
130
40 TEK2012 Development
100
80 of TEK2017 60 150 Building practice
100 Lo
TEK2017 TEK2017
60 TEK2017 100
0,4 100 100
100 100
60 Energy-saving 100
60Low-energy buildings Low-energy buildings
TEK2022 40
100
Flanders Brussels Valloria
Low-energy buildings 50
TEK2022 Flanders Brussels 20
Valloria Flanders Brussels Valloria 65 Equivalent thermal insulation requirements Research
0,2 65 65
40TEK2022
Equivalent
40 TEK2022 50 Construction
65thermal insulation requirementsEquivalent thermal insulation requirements 30Research
40
Flanders 50 Brussels
Three-liter houses
Research
Equivalent thermal
Valloria
TEK2027
Three-liter houses
insulation requirements 20
50 EPB-requirements
Legal
Research Three-liter houses
0
(Demonstration proj
TEK2027 TEK2027
Legal EPB-requirements TEK2027 (Demonstration project) Zero-heating energy buildings
(Demonstration project) Zero-heating energy buildingsPolicy intentions
(Demonstration project) Zero-heating energy buildings
Legal EPB-requirements 0 Legal EPB-requirements
0 30 30 0 20 20
0 20 0 0
30
Policy intentions Policy intentions 0 PolicyPlus-energy
intentions houses Plus-energy houses 0 Plus-energy houses -50
1990
1995
2000
2005
2010
2015
2020
2025
1961
1979
1995
2006
20222010
20272015
2020
20072002
19882004
19922006
19962008
20222010
20272012
20082014
2016
19852018
2020
0 0 0 -50
1997
2007
2012
2017
2022
2027
1984
1988
1992
1996
2000
2004
2008
2012
2016
2020
1980
1985
0 0 0 -50 -50
1997
2007
2012
2017
2022
2027
1984
1988
1992
1996
2000
2004
2008
2012
2016
2020
1980
1990
2000
2005
2010
2015
1997
2007
2012
2017
1984
2000
2004
2012
2016
2020
1980
1985
1990
1995
2000
2005
2015
1997
2012
2017
1984
1988
1992
1996
2000
2004
2008
2012
2016
2020
1980
1985
1990
1995
2000
2005
2010
2015
Year Year Year
Building stock average Year Year
Year Year Year Year Year Year Year Year Year
Development of Energy-saving
Norway Belgium Construction
300
y consumption, kWh/m2a
Requirement %
y demand-heating, kWh/m2a
Minimum requirements
Existing buildings 120 250 (WSVOVEnEV)
207
TEK97 100 200 Solar houses
TEK07
165 80 150
TEK2012 Building practice
130
TEK2017 60 100 Low-energy buildings
14 100 15
Flanders Brussels Valloriait’s time to change our way of thinking | 1
Innovation Radiators have come a long way from the bulky column
Fig. 1.2:
designs of 40 years ago (Fig. 1.2). The early steel panel forms Innovation in steel panel radiators
had a plane panel structure and high water content (A). Next
A
came the introduction of convector fins between the water plane panel structure 1970s
Reducing the channels, increasing their output (B). Over the years, it was with high
water content discovered that the thermal output could be increased by water content
and placing the reducing the water content and placing the fins in contact B
fins in contact with convector fins between
with the hotter channels (C). It wasn’t until the channels the water channels
the hotter channels The volume
has increased were flattened, in the hexagonal optimized form illustrated increasing their output
capacity became
thermal output here, that the contact surface area was maximised and heat C smaller over the
thermal output was increased years, resulting
output fully optimized (D). in less water, less
by reducing water content
and placing fins in contact energy and quicker
with the hotter channels reaction to thermal
heat changes.
D
An innovative welding
technique in combination
with the specific shape of
the radiator inner panel
makes the Radson
radiator unique. present
Radson indeed welds 2
convection fins on each
hot water channel
(2-on-1 principle).
This technique allows
Radson to use smaller
heating elements.
16 17it’s time to change our way of thinking | 1
Up to 87% better Computer simulation has also helped to significantly improve
energy efficiency in recent years: optimising the flow of Fig. 1.3:
Innovation in steel
heating water through the radiator, heat transmission to the panel radiators 70’s
convector fins, and calculating the optimum radiant and
With today’s designs, convected heat to the room. With today’s designs the More channels, more
40oC 45oC
the material convectors and less
material efficiency is up to 87% better than in traditional thermal mass –
efficiency is up to models, yet many people still hold on to an outdated image modern radiators
87% more efficient increase heat output
of radiators that was surpassed decades ago (Fig. 1.3)
than in traditional using less water at the
models same temperature as
traditional models.
35oC
What’s more, there is
an 87% improvement
in material efficiency
in terms of W/kg present
of steel.
43oC 45oC
35oC
18 19HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
chapter 2 Room heat is wasted in two ways: the first is via heat losses
through the building envelope, window, walls, roof etc.
to outside (transmission losses); the second is via air flow
Insulation
to outside (ventilation and air leak losses). The purpose of
HOW INSULATION insulation improvements is to minimise transmission losses
in the most cost effective way.
INFLUENCES A human body emits around 20 l/h CO2 and around 50 g/h
of water vapour. In addition, household activities and
HEATING EFFICIENCY showering bring several litres of additional water vapour
into the room air per day. This makes ventilation air flow
essential; reducing it would have dramatic consequences,
• Insulation > Insulation has always played a major role in as it would cause health problems to occupants or
keeping homes warm and dry contaminate the building (with mould etc).
• The positive impact of changing legislation > Besides
saving energy and reducing costs, the immediate benefit One issue of improved insulation is the increased airtightness
of better insulation is a more comfortable indoor climate of the building. Poor ventilation, increased room humidity,
• Heat gains and heat losses in modern buildings > high CO2 content and construction condensation can all
When the heat losses and heat gains are all factored in, appear as a result. This is why properly insulated buildings
the effective level of energy efficiency can be determined should also be equipped with mechanical ventilation.
• It’s important that the heating system can react quickly
to the incidental heat gains The heat recovered from the ventilation air exhaust can
• The smaller the thermal mass of the heat emitter, then be utilized as an efficient source of energy.
the better the chances of accurately controlling
room temperature
20 21HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
Insulation has Insulation has always played a major role in keeping homes
always played a warm and dry, from the earliest use of straw, sawdust and Fig. 2.1:
major role in Projected heating Heat costs
cork. Today’s modern alternatives, such as fibreglass, mineral in €
keeping homes costs for single
wool, polystyrene and polyurethane boards and foams, have family house:
warm and dry 107.000 €
helped change building methods, encouraging less reliance insulated vs. 100.000
uninsulated.
on the thermal properties of thicker walls and high tempera-
ture radiators.
70.000 €
€86.000 saved Obviously, a well-insulated house is easier to heat than its 50.000
after 20 years 41.000 €
less-insulated counterpart. It loses less heat, and therefore
uses less energy. Fig. 2.1 compares the estimated heating 21.000 €
costs of two family homes - one properly refurbished, 8.000 € 14.000 €
0
the other with no insulation. The important contrast In 10 years In 15 years In 20 years
between the two becomes even more apparent over time,
not renovated
with a staggering €86.000 saved after 20 years.
optimally renovated Source: dena
22 23HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
Fig. 2.2:
Changing German
building insulation
Saving energy and reducing costs were not the only effects The positive
requirements since
1977 of tighter regulations. The immediate benefit of better impact of changing
insulation was a more comfortable indoor climate. Figs. 2.3 legislation
- 2.5 (overleaf) illustrate a room interior as it would be when Besides saving
U-value insulated in line with changing building legislation. As you energy and reducing
window costs, the immediate
can see, the only constant across all examples is the outdoor
U-value benefit of better
temperature, a steady -14 °C. The surface temperature of
external wall insulation is a more
the window in Fig. 2.3 is zero, as the glass is a single pane. comfortable indoor
Pre 77 1977 WSVO 1984 WSVO1995 ENEV 2002 ENEV 2009
U-value window W/m2K 5 3,50 3,10 1,80 1,70 1,30
In order to reach an acceptable 20 °C room temperature, climate
U-value external wall W/m2K 2 1,00 0,60 0,50 0,35 0,24 homes insulated to WSVO 1977 standards had to use hot
Specific heat load W/m2 200 130 100 70 50 35
radiators at 80 °C mean water temperature. Even at this very
Tflow/Trtn °C 90/70 90/70 90/70 & 70/55 70/55 55/45 45/35
high temperature, the walls would only reach 12 °C, resulting
in a large temperature difference and a range of noticeable
In line with energy efficient improvements in insulating cold spots.
methods and effectiveness, legislation has been put in place
to ensure new and renovated buildings conform to increa- Over time, as building regulations changed, indoor Indoor climate
singly strict regulations. Using Germany as an example, here temperatures became noticeably better, as shown in Fig. 2.4.
we can see that since 1977 these regulations have steadily With the widespread use of double glazing came relief from
lowered the permitted levels of heat loss to the exterior. freezing windows and protection from sub-zero temperatures.
Back in 1977, the For homes heated by water-based central heating systems, To reach ideal room temperature, radiators now had to
norm for design one of the more remarkable developments shown here is generate only 50 °C output (average heating temperature),
inlet/return was the inlet and return temperatures of the water. Back in 1977, while walls reached 18 °C, a more balanced midpoint between
almost double that the norm was 90/70 (design inlet/return), almost double the window’s 14 °C and the air temperature of 20 °C. This
demanded under
that demanded under EnEV 2009. Clearly, this shift towards situation improves further still for buildings insulated to EnEV
EnEV 2009
low water temperature heating systems is made possible 2009 towards EnEV 2012 standards.
by the increasing use of effective energy refurbishment.
24 25HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
Fig. 2.3: Pre 1977 temperatures in a standard house (90/70/20 °C) Fig. 2.5 – EnEv 2009 (45/35/20 °C)
* 30
* 30
28 Still Pleasant Too hot
28 Still Pleasant Too hot
26 26
24 tAw= 12oC 24 tAw= 19oC
22 22 Pleasant
Pleasant
20 20
tF= 0 C
o
tA= -14 C
o
19 tF= 17oC tA= -14oC
18 18
17
16 16
Cold and
14 Cold and 14
not pleasant
not pleasant
12 12
tHKm= 80oC tHKm= 40oC
10 inlet= 90oC 10 inlet= 45oC
0 0
10 12 14 16 18 20 22 24 return= 70oC 10 12 14 16 18 20 22 24 return= 35oC
tR= room temperature tR= 20oC tR= room temperature tR= 20 C
o
Fig. 2.4. EnEV2002 (55/45/20 °C) The walls in Fig. 2.5 are almost at room temperature. Even
the windows are warm, despite the freezing exterior. Notice
* 30 that the radiator output now needs only to reach a mean
28 Still Pleasant Too hot
26
water temperature of 40 °C to achieve this ideal scenario
24 tAw= 18oC – 50% less than the same building insulated according to
22 Pleasant the standards of Fig. 2.3.
20
tLuft= -20oC tF= 14oC tA= -14oC
17
18
* Thermal Comfort: There are several standard criteria; here are some:
16
Cold and
• the average value air temperature and mean surface temperature is
14
not pleasant around 21°C.
12
tHKm= 50oC • The difference between air temperatures and mean surface temperatures
10 inlet= 55oC
varies by no more than 3°C.
0
10 12 14 16 18 20 22 24 return= 45 C o • The difference between mean surface temperatures in opposite direction
varies by no more than 5°C.
tR= room temperature tR= 20 C o
• The average temperature between head and ankle heights are less than 3°C.
• The air velocity in the room less than 0.15 m/s.
26 27HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
Old fashioned room Modern insulated room
Fig. 2.6
Illustrates the The increased energy efficiency of buildings during the last Size of radiators
importance of 30 years has enabled the design temperatures of radiators to
insulation.
be lowered. In the illustration, both radiators have the same
In the example approximate dimensions. The desired room temperature
the radiators in both cases is the same. As you can see, in an uninsulated
are the room = 20oC room = 20oC
same size. house, in order to achieve the desired room temperature, the
inlet and return temperatures are much higher than those of
a well insulated house. The advantage is that the radiator in
the modern room can be the same size as that in the old room,
inlet= 70oC inlet= 45oC
due to the insulation resulting in a lower level of heat demand.
return= 55oC return= 35oC
Fig. 2.7
overskydende
Same size temperatur
radiator conforms AT
o
C
Specific heat demand: 100 W/m2 Specific heat demand: 50 W/m2 to changing
living area x heat demand: living area x heat demand: 60 90/70/20
pa
building energy
ne
11 m2 x 100 W/m2= 1100 W 11 m2 x 50 W/m2= 550 W
requirements.
lr
50
System temperature: 70/55/20°C Systemtemperature: 45/35/20°C
ad
ia
Radiator dimensions: Radiator dimensions:
to
70/55/20
Parameters shown
r
40
h 580mm, w 1200mm, d 110mm h 600mm, w 1200mm, d 102mm (Type 22)
22
are the heat
/6
n*= 1.25 n*= 1.35
0
30
output/specific 55/45/20
0x
Q= 1100 W Q= 589 W
12
load and the excess
00
20 45/35/20
Disadvantages of old cast steel radiators: Advantages of current panel radiators: temperature ΔT.
• large water content • small water content 10
(large pump, high electrical costs) • light weight
• bad controllability • optimized for a high heat output 0
(high weight, large water content) • excellent controllability 300 200 100 0 W/m2
• long heat up and cool down time • short heat up & cool down time 235 150 90 50 specifik
varmebelastning
(not suitable for modern LTR systems) • modern look, different models, colours
• old fashioned look and designs for all needs and tastes
• 10 years warranty
*n is the exponent that indicates the change in heat output when room and water temperatures differ from the
values used to calculate θ 0 . The exponent n is responsible for the relation between radiation and convection of
the radiator (this depends on the design). The lower the inlet temperature, the lower the convection.
28 29HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
Heat gains and The energy needs of a building’s occupants include the
Figure 2.8
heat losses demands of their heating system. Fig. 2.8 illustrates of how
energy is brought into the home from its starting point,
Calculation of energy demand
after it is generated as primary energy.
When the heat The energy used by a building depends on the requirements
losses and heat of the people inside. To satisfy their needs, and provide
gains are all factored QS
a comfortable indoor climate, the heating system has to
in, the effective
generate heat from the energy delivered to the building.
level of energy
efficiency can be When the heat losses and heat gains are all factored in, the
QT QI
determined effective energy can be determined. The way that energy is EFFECTIVE
QV
used depends on the efficiency of the heating system and, QE Q H energy
as we have seen, on the level of insulation in the building. primary
energy
QD QS QG
Delivered
energy
Qt – Transmission heat losses
Qv – Ventilation heat losses
Qs – Solar heat gain
Qi – Internal heat gains
Qe, d, s, g – Losses through emission, distribution, storage and generation
Qh – Heat load
30 31HOW INSULATION INFLUENCES HEATING EFFICIENCY | 2
Influence Heat gains are often overlooked when discussing effective Fig. 2.9
of heat gains energy. When electrical equipment is switched on, or
on modern additional people enter the building, or sunlight enters Thermal heating requirement for a living room of 30 m2.
buildings Building standard EnEv 2009, EFH, building location Hanover.
a room, these all raise the temperature inside.
Thermal load at -14 °C = 35 W/m2 = 1050 W
Energy efficiency is heavily reliant on two things: how well Thermal load at 0 °C = 21 W/m2 = 617 W
the heating system can utilize the heat gains and thereby Thermal load at +3 °C = 18 W/m2 = 525 W
reduce the heating energy consumption; and how low the
Average indoor thermal gains
system heat losses are. Average in accordance with DIN 4108-10 = 5 W/m2 = 150 W
Person, lying still = 83 W/person
It’s important that Because modern buildings are more thermosensitive, it is Person, sitting still = 102 W/person
Light bulb, 60 W
the heating system important that the heating system can quickly react to the
PC with TFT monitor = 150 W/unit (active), 5 W/unit (standby)
can react quickly to the incidental heat gains. Otherwise, the indoor temperature Television (plasma screen) = 130 W/unit (active), 10 W/unit (standby)
incidental heat gains can soon become uncomfortable for the occupants Example: 2 people, light, TV, etc. = approx. 360 - 460 W
(which can, for instance, have a negative impact on
A state-of-the-art heat emission system must be able to adjust quickly
office productivity). to the different thermal gains indoors!
32 33interview with Christer harryson | B
HOW TO
TURN
ENERGY INTO
EFFICIENCY
Professor Dr. Christer Harrysson is a well known researcher who lectures on Energy Techniques
at the Örebro University in Sweden. He has conducted extensive research into the energy
consumption of different energy systems, sources and emitters.
Professor Dr. Christer Harrysson lectures at the Örebro University (Sweden)
and is Director of Bygg & Energiteteknik AB
34 35interview with Christer harryson | B
Prof. Dr. Research is one of the most important tools for increasing underfloor heating. In short, our data shows radiators
Christer Harrysson knowledge and obtaining a clear, independent insight into to be 15-25% more efficient than underfloor heating.
the functions of different heating distribution systems. It Measurement data also shows that the 15% difference
also makes it possible to rank the performances of a variety correlates with houses that have underfloor heating with
of solutions. In my research, I studied the energy used by 200mm ESP insulation beneath the concrete floor tiles.
130 houses in Kristianstad, Sweden over a one-year period.
Their electricity, hot water and heating system energy Conclusion The most important and significant finding of this study
consumption were all closely monitored. All the houses were is that designers, suppliers and installers need to apply
built between mid-1980s and 1990, and were grouped in six their skills and provide residents with clear and transparent
distinct areas, with variations in construction, ventilation and information. In addition to that, we found the level of
heating systems. The results were convincing. We recorded comfort to be as important as the calculated energy
differences of up to to 25% in energy use between the performance and consumption of new, but also renovated
different technical solutions in use. buildings. This is something that should be taken into
account not only by project planners and constructors, but
My main objective was to determine the difference between also by the owners and facility managers of new buildings.
energy efficiency of different types of heating systems and
the thermal comfort these systems offer. We compared Note: Houses in the study are directly comparable with
the recorded results of underfloor heating and radiators, the buildings insulated according to the German EnEV 2009
and conducted interviews with residents. We found that regulations.
homes heated with radiators used a lot less energy. In total
– including the energy for the heating system, hot water A complete summary of the research conducted
and household electricity – the average energy consumption by Professor Harrysson can be found at
measured was 115 kWh/m2. This was in comparison to www.radson.com/re/clever
the average use of energy of 134 kWh/m2 in homes with
36 37THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
chapter 3 Thanks to lower heat demand, homes and offices now need
less heating energy to keep them warm. This makes the heat
pump an ideal companion in a modern heating system.
Heat pump
Temperature a few metres beneath the ground is fairly constant
THE INCREASING
throughout the year, around 10°C. Geothermal heat pumps
take advantage of this, with the help of a loop of tubing –
USE OF LOW
the vertical ground loop – buried 100-150m under the soil or
alternatively the horizontal grid closer to the surface. Typically
a water/ethanol mix is pumped through this loop, where heat
TEMPERATURE exchange occurs before the warmed fluid returns to the pump.
From there the heat is transferred to the heating system.
WATER SYSTEMS
Air-water heat pumps are also good alternatives. They can use
outdoor air or/and ventilation exhaust air as a heat source.
Engine
• Heat pump and condensing boiler > Both heat sources Electricity
in modern and insulated buildings are efficient ways to Fig.3.1
Diagram of Heat in Heat out
supply low-temperature water systems heat pump
• Efficiency of heat generation > Both heat sources also Compressor
function perfectly with low temperature radiators
2. Compression
• Energy refurbishment of buildings > Buildings heated
1. Evaporation 3. Condensation
by low temperature radiators systems consume less
total energy than underfloor heated buildings Source:
4. Expansion
• Improving the energy efficiency of older buildings Pro Radiator
Expansion Valve
Programme
is a more effective way of saving more energy Evaporator Condenser
38 39THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
Condensing boiler Traditional boilers had a single combustion chamber enclosed Both heat pumps and condensing boilers are efficient ways Both heat sources
by the waterways of the heat exchanger where hot gases to supply low-temperature water systems in modern and are efficient ways
passed through. These gases were eventually expelled through insulated buildings, making them ideally suited to radiators, to supply low-
temperature
the flue, located at the top of the boiler, at a temperature of which can be used with any heat source, including
water systems
around 200°C. These are no longer fitted new, but in the past renewable energy.
many were fitted in existing homes. Condensing boilers, on
the other hand, first allow the heat to rise upwards through Fig.3.2
Diagram of Waste Gas
the primary heat exchanger; when at the top the gases are condensing boiler Flue
rerouted and diverted over a secondary heat exchanger.
In condensing boilers, fuel (gas or oil) is burned to heat
water in a circuit of piping, which can include the building’s
radiators. When the fuel is burned, steam is one byproduct
of the combustion process, and this steam is condensed
Burner
into hot water. Energy is extracted and heat gained from
this return flow water, before it is returned to the circuit
(fig.3.2). While either gas or oil can be used, gas is more
efficient since the exhaust of the heated water in a gas
system condenses at 57°C, whereas in an oil-based system Air flow Water
this does not occur until 47°C. An additional advantage of
a gas system is its higher water content.
For all condensing boilers, there is significant energy saving
through the efficient use of the combusted fuel: exhaust gas
Radiator
is around 50°C , compared with traditional boilers, whose
flue gases escape unused at 200°C.
40 41THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
Condensing boilers can function in the condensing mode Efficiency of
Fig. 3.3 100 when the inlet water temperatures to the heating network heat generation
Effect of inlet water remain below 55°C. Efficiency increase, compared to a
temperature on
98 standard boiler, is around 6% for oil and around 11% for gas.
efficiency of
condensing boilers.
96
Heat pumps are often assumed to be specific to underfloor Heat pumps
heating, when in fact they also function perfectly with low also function
94
temperature radiators. EN 14511-2 standard describes a perfectly with
low temperature
92 Noncondensing mode simplified method for calculating the seasonal performance
radiators
Boiler efficiency, %
factor, SPF, taking only the heating system inlet water
90 temperature into account. This way of calculation can give
Dew point reasonably accurate SPF values for underfloor heating,
88
where the inlet and return water temperature differences
86
are typically small, often less than 5 K. This simplified
Condensing mode 10% Ex method is not applicable for radiator heating, where the
cess air
84 inlet and return water temperature differences are larger.
For these calculation purposes EN 14511-2 shows an
82 accurate method, also taking into account the return water
Source ASHRAE
Handbook 2008 temperature. In conjunction with SPF is COPa, the annual
80
10 20 30 40 50 60 70 80 90 100 110 coefficient of performance, which describes the heat pump
Inlet water temperature, C o
efficiency, when the season length is one year.
Note: The primary energy need of a condensing boiler
with solar used for heating and warm water resembles
that of the sole water heat pump.
Source: ZVSHK, Wasser Wärme, Luft, Ausgabe 2009/2010
42 43THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
Fig. 3.4 Table of COPa values for different design water The results show that it is highly favourable to use low It is highly favourable
temperatures, combined heating and domestic hot water temperatures with radiators, when using heat pumps as to use low
production, DHW, and heating only. Also shown are the a heat generator. Heat pumps for small houses are often temperatures with
radiators, when
resulting condensing temperatures. The reference building combined with DHW production. When comparing the
using heat pumps
is a modern single-family house in Munich, equipped with combined COPa values, we can see that design water as a heat generator
electric ground source heat pump. COP values are verified temperatures of a typical LTR system (45/35) give around
by laboratory measurements (Bosch 2009). 10% higher heat pump efficiency than the 55/45 system.
The difference between the 45/35 system and for typical
underfloor heating 40/30 system is around 3%, and 9%
Fig. 3.4
Annual Coefficient of Performance: COPa when compared with the 35/28 system.
COPa = Quantity of heat delivered by heat pump divided by the energy
needed to drive the process over a one year period
Fig. 3.5
Design Condensing COPa COPa Water
Radiator return temp.°C
temps temp combined heating only
temperature, when
using the thermostatic +50°C
70/55/20 62.4 2.8 3.0 radiator valve, is lower t
55/45/20 49.2 3.2 3.6 due to the heat gains +45°C
60/40/20 49.0 3.2 3.6 and corresponding
50/40/20 44.0 3.3 3.8 thermostat function +40°C
45/35/20 38.8 3.5 4.1 t return
+35°C
50/30/20 38.7 3.5 4.1
40/30/20 33.7 3.6 4.4 +30°C
35/28/20 30.2 3.8 4.6
+25°C
Electric ground-source heat pump. COPa figures from reference building
(IVT Bosch Thermoteknik AB) +20°C
+20°C +10°C 0°C -10°C -20°C Outdoor
Temp°C
44 45THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
Energy refurbish- In short, buildings heated by low temperature radiator
ment of buildings systems consume less total energy than underfloor heated Fig.3.6 100
5
Focus on old buildings:
buildings, even when using heat pumps as a heat generator. Buildings in figures 23
Buildings heated by Differences of COP values are compensated by the higher and in terms of energy 80
low temperature energy efficiency of the low temperature radiators. consumption,
radiators systems Fraunhofer 2011
consume less total 60
Buildings, particularly residential buildings are currently
energy than 77% of the buildings 95
underfloor heated in a upward spiral of energy consumption. Energy used in in Germany built 40 77
buildings buildings is the biggest single energy consumption sector before 1982 use 95%
in Europe. Logically our energy-saving activities should be of heating energy.
directed at reducing energy use in buildings. Interestingly 20
though, modern buildings (new or well-renovated) are not built after 1982
built before 1982
of newer buildings built after 1982 make up 23% of the 0
country’s total stock, but consume only 5% of the heating amount of buildings use of heating energy
energy. In other words, improving the energy efficiency of
Improving the older buildings is a more effective way of saving more energy.
energy efficiency
of older buildings is
a more effective
way of saving
more energy
46 47THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
A building’s total A building’s total energy balance consists of energy flows
energy balance Fig. 3.8
into and out of the building. Potential cooling energy is not Example of the ventilation and air leaks 36.6% roof 7.3%
consists of energy included in these figures. The energy flows of the example space heating
flows into and out energy balance sun and
building can be defined as follows:
of the building of a multi-storey occupants 25%
building
Fig. 3.7 windows and external doors 24.4%
ventilation and air leaks 30% roof 6% external walls 26.8%
Example of the
total building space heating 50%
sun and
energy balance electricity usage 25%
occupants 20% ground 4.9%
of a multi-
storey building
windows and external doors 20% Out from building/losses Into building/inlet
external walls 22% - Ventilation and air leaks 36.6 % - Space heating 50 %
- External walls 26.8 % - Electricity usage 25 %
space heating and DHW 60% domestic hot - Windows and external doors 24.4 % - Sun and occupants 25 %
electricity usage 20% water to sewer 18% - Roof 7.3 % sum 100 %
ground 4% - Ground 4.9 %
sum 100 %
Out from building/emissions and losses
- Ventilation and air leaks 30 % - Air change rate = 0.5 1/h
- Domestic hot water to sewer 18 % - 35 kWh/m2a These figures are example values for older multi-storey
- External walls 22 % - U = 1.0 W/m2K
- Windows and external doors 20 % - U = 3.5 W/m2K buildings, where the typical demand of space heating energy,
- Roof 6% - U = 0.7 W/m2K including transmission losses and ventilation, is around
- Ground 4% - U = 1.0 W/m2K
sum 100 % - Uw.mean = 1.3 W/m2K 240 kWh/m2a. If we want to make an approximation of other
Into building/inlet house types, we should take into consideration the following
- Space heating and DHW 60 %
- Electricity usage 20 % features: surface sizes, U-values and ventilation air flow
- Sun and occupants 20 %
sum 100 %
rates. For instance, a single-storey house has relatively
much higher losses through the roof and to the ground
If we exclude the DHW energy losses to sewer, which is actually a
potentially huge energy saving source, we can see the figures where than a multi-storey building.
the energy renovation activities are normally focused.
48 49THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
We can make a correlation of space heating demands, Space heating
Fig. 3.9 kWh/m2a, and the specific heat loads, W/m2, based on the energy demand
Space heating available statistics for different German building energy and specific heat
demand - loads
specific heat Heat demand requirement periods.
load diagram for kWh/
m2a
approximation
purposes 240
Let us consider the reference multi-storey building if it is
renovated, and recalculate. Specific heat load in the original
German Development stage can be rated from the diagram Fig. 3.9 at space heating
demand of 240 kWh/m2a. Heat load value is about 120 W/m2.
180 The building envelope and insulation will be improved.
The new U-values of the building elements will be:
120 - External walls U = 0.24 W/m2K
- Windows and exterior doors U = 1.3 W/m2K
- Roof U = 0.16 W/m2K
- Ground U = 0.5 W/m2K
100
Uw.mean =0.40 W/m2K
120 90 60 30 0 W/m2
1977 WSVO84 WSVO95 EnEv02 specific
EnEv09 heat load
EnEv12
NZEB
Development of heat demands and specific heat loads in German buildings.
50 51THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
If there are no surface area changes in the building
elements and the ventilation air-flow rates remain
unchanged as well, we can calculate the influence of
the improved insulation. The transmission losses will be
reduced to 31%, when the area weighted U-values, Uw.
mean = 1.3 W/m2K go down to Uw.mean =0.40 W/m2K.
Thus the ventilation remains unchanged and the total
heat loss reduction will be only 44.3%.
Note: This type of widespread insulation improvement
project is often motivated by a need for better windows
and a more attractive façade or by need of higher thermal
comfort and healthier indoor environment.
The new share of losses will be:
- Ventilation and infiltration 65.1 %
- External walls 11.4 %
- Windows and exterior doors 16.1 %
- Roof 3.6 %
- Ground 4.4 %
sum 100 %
The heat load will be 44.3% smaller than in the original
case. New specific load is about 67 W/m2, and from Fig. 3.9
we can see that the corresponding heating demand value is
about 100 kWh/m2a.
52 53interview with professor dr. jarek kurnitski | b
Iscience
TURN INTO
practice
Professor Dr. Jarek Kurnitski, one of the leading scientists in the HVAC field, is currently
working as top energy expert in the Finnish Innovation Fund, Sitra. As a European REHVA
awarded scientist, he has published close to 300 papers.
Professor D.Sc. Jarek Kurnitski
Helsinki University of Technology
54 55interview with professor dr. jarek kurnitski | b
Bigger is certainly Within the heating industry there is still the myth that any hope for energy efficiency soon fades. A room tem-
not better within low temperature heating systems you need bigger perature difference of one degree correlates to around 6%
radiators. Bigger however is certainly not better. During my energy consumption. Fast response to heat gains and low
comparative research into heat emitters, I found that even system losses are key elements of energy efficient heating
during the coldest winter period, rapidly changing heat systems. Central control leads to overheating in some
output is needed to keep room temperature in the optimal rooms with a consequent energy penalty, which is why my
comfort range. Both systems were set at 21°C, the lowest research recommends the use of low temperature systems
comfort limit and ideal indoor temperature. As you can see to reduce system losses, as well as the use of heat emitters
in Fig. A.1, when internal heat gains of not more than 0.5°C that can be individually controlled. This makes radiators
were detected, the radiator system with its small thermal the obvious choice.
mass reacted quickly and kept the room temperature close
to the setpoint.
However, with the high thermal mass of underfloor heating,
reaction time was much slower when heat gains were
detected. This meant that underfloor systems kept emitting
heat, taking the temperature far above the optimal, with
strong uncomfortable fluctuations. In fact, in order to
keep the room temperature closer to the optimal 21°C,
my research shows that the only solution is to increase
the setpoint for underfloor systems to 21.5°C.
For a lot of people 0.5°C may seem a small number. But
when you apply that per hour, daily, across a whole Winter
heating period, the numbers soon start to multiply and
56 57SIGNIFICANT PROOF | 4
chapter 4 In 2008 the R&D department of Rettig ICC started a new
project. Its aim, to clarify different misconceptions that
persisted in the heating industry. The Pro Radiator Programme
Mikko Iivonen,
Director R&D,
Research and
Technical Standards,
- as we named the project - took us two years. In these two
Rettig ICC
SIGNIFICANT
years we collected three different types of arguments: ‘In
favour of radiator heating’, ‘Against radiator heating’ and ‘
PROOF
In favour of competitive / other heating systems’.
In total we identified 140 claims and theories. After an
initial examination we were able to amalgamate these
into 41 practical research issues to test, analyze and reach
conclusions. To achieve impartial and independent research
results, we asked external experts for their cooperation to
• Professor Dr. Jarek Kurnitski > overall conclusions help us out with this immense research task. Several leading
of my research show that radiators are around 15% international experts, universities and research institutes
more efficient in single-storey houses and up to 10% worked closely together with us. The result was a tremendous
in multi-storey buildings. amount of research data, conclusions and recommendations.
• Professor Dr. Christer Harrysson > under the given
conditions, areas with underfloor heating have, on We also found that the industry was saturated with myths
average, a 15-25% higher level energy consumption and illusions. Although they dominated market discussion,
(excluding property electricity) compared to the these ranged from irrelevant to untrue. The biggest news
mean value for areas which have radiator systems. for us, however, was that all research results showed how
efficiently and effectively radiators functioned in modern
well insulated buildings. Once we had identified these
results, we started a new dedicated research programme,
58 59SIGNIFICANT PROOF | 4
working with the HVAC Laboratory of Helsinki University Both Prof. Jarek Kurnitski and Prof. Christer Harrysson share Academic
of Technology, to examine different heating systems. The their most important findings regarding these specific case co-operation
accurate simulations and function comparisons of all these studies with you in this chapter.
different heating systems confirmed that our earlier results
and conclusions for radiators were correct. All the studies we have referenced in this guide have shown
that energy efficiency can be increased by at least 15%
Concrete data We have already referred to some of our research results in when low temperature radiator systems are used. This is
this guide. For you, however, it’s important to realise that a conservative estimate - some studies show that the figure
our conclusions are based not only on scientific theory, can be even higher. Often the reasons for this are occupant
but also on concrete data from recently-built low energy behaviour; higher room temperatures, longer heating
buildings in the Nordic region. Countries like Sweden, periods, etc.
Finland, Norway and Denmark have been leading the way
in low-energy and high-insulation practices for many years.
This fact, coupled with our work with academics including
Prof. Leen Peeters (Brussels University - Belgium) and
Prof. Dr. Dietrich Schmidt (Fraunhofer Institute – Germany),
means that we can now confidently say that all our results
and conclusions are valid for the vast majority of European
countries. In confirmation of the theoretical savings
outlined in previous chapters, a number of studies from
the same period measured the efficiency of modern
heating systems and compared the energy use of various
heat emitters.
60 61SIGNIFICANT PROOF | 4
Professor The research of Professor Jarek Kurnitski shows that the
Jarek Kurnitski: thermal mass of heat emitters has a huge influence on
Thermal mass and Fig. 4.1. o
heating system performance. Even during the coldest C
Room temperature
Room temperature
energy efficient
Winter period, rapidly changing heat output is needed to response to UFH
heating thermal mass of
keep room temperature in the optimal comfort range. the heat emitter in
Radiator
the Winter season 22.5
In case of The principle of the room temperature response to heat when heat gains
typically do not
fast-reacting gains and losses is shown in Fig.4.1, where two systems exceed 1/3 of the
radiator heating are compared. In the case of fast-reacting radiator heating heating demand
systems with small 22.0
systems with small thermal mass, the heat gains elevate
thermal mass, heat Set point
gains elevate room room temperature not more than 0.5˚C, keeping room UFH
temperature not temperature close to the setpoint of 21˚C. Traditional
more than 0.5°C underfloor heating with high thermal mass fails to keep 21.5
room temperature constant. Research showed that the
setpoint had to be increased to 21.5˚C to keep the room
temperature above the lower comfort limit of 21°C. The 21.0
sheer size of the heat emitter meant its output was lagging
Set point Lowest
behind the heat demand, resulting in strongly fluctuating radiator comfort limit
room temperature and wasted energy.
20.5
0 6 12 18 24 30 36 42 48
Hours
62 63SIGNIFICANT PROOF | 4
Maximising The situation shown in Fig. 4.1 is based on detailed,
heat gains in dynamic simulations of a modern house in Germany. Room Fig. 4.2
modern buildings temperature results for the first week of January are shown Simulated room temperatures, first week in January. Outdoor temperature,
solar and internal and external heat gains are shown on the left.
in Fig. 4.2. Because of the unpredictable nature of solar and
internal heat gains, the performance of underfloor heating 8 Outdoor temperature 2000 Value 23.0
cannot be improved with predictive control strategies. Heat 6 Direct beam radiation
Defused radiation
1800
1.0
4 1600 0.9 22.5
gains do turn off floor heating, but it still radiates heat to
Outdoor temperature C
Solar radiation W/m2
o
2 1400 0.8
0 1200 0.7 22.0
colder external surfaces, such as windows and external walls, -2
24 48 72 96 120 144 168
1000
0.6
0.5
-4 800 21.5
0.4
for a considerable time. This overheats the room. -6 600 0.3
-8 400 0.2 21.0
-10 200 0.1
0.0 20.5
-12 0
At night, when room temperature drops below the setpoint Time, hours 16 18 20 22 0 24 48 72 96 120 144 168
Time, hours
of 21.5°C, it takes many hours before the temperature starts
to increase, despite the floor heating switching on. In fact, External heat gains first week Internal heat gains per day Resulting air temperatures
the research showed that room temperature continued to of January - Weather data.
decrease, which resulted in the need for the elevated setpoint.
Advanced building simulation software, named IDA-ICE,
was used to gain the results described above. This software
has been carefully validated and has proved to provide highly
accurate data in such system comparison calculations.
64 65SIGNIFICANT PROOF | 4
In midseason, heat gains are close to heating needs, which
makes it more complicated to control room temperature. Fig. 4.3
Sunny days in March will increase
Fig. 4.3 shows the performance during two days in March. room temperature fluctuation
Solar gains are significant and outdoor temperature Solar rad
fluctuates strongly. Once again, radiator heating resulted 12
Outdoor temperature
Direct beam radiation
2000
Defused radiation
in more stable room temperature and better utilisation of 10 1800
Value
heat gains. 8 1600
1.0
6 1400
Outdoor temperature oC
0.9
Solar radiation W/m2
4 1200 0.8
Conclusion Fast response to heat gains and low system losses are key -2 1000
0.7
0.6
elements of energy efficient heating systems. Individual 0 800 0.5
1824 1848 1872
temperature control in each room is also highly important, -2 600 0.4
0.3
because heating needs vary strongly from room to room. -4 400
0.2
-6 200 0.1
Central control leads to overheating in some rooms with -8 0 0.0
Internal heat
gains
Internal heat
gains
a consequent energy penalty. For this reason, our research Time, hours 16 18 20 22
recommends the use of low temperature systems to reduce External heat gains Internal heat gains per day. Resulting air
17-18 March - Weather data. temperatures.
system losses, and responsive heat emitters with
individual/room control.
Therefore, we can also conclude that under floor heating
is less effective and less energy efficient, compared to the
results we measured with radiators. As a matter of fact the
overall conclusions of our research showed that radiators
are around 15% more efficient in single-storey houses and
up to 10% in multi-storey buildings.
66 67You can also read
