redwell-studie-uni-thessaloniki-v1.2-2011-en

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REDWELLCOMPARISON STUDY 2010Redwell Infrared-Heater in comparison to conventional Heater

In cooperation with ARISTOTLE UNIVERSITY THESSALONIKI LABORATORY OF HEAT TRANSFER AND ENVIRONMENTAL ENGINEERING

REDWELL MANUFAKTUR GmbH is proud to present the results of the Comparison Study developed by the ARISTOTLE UNIVERSITY THESSALONIKI and wants to confi rm the results herewith.

Hartberg, Dezember 2010© Copying the report is forbidden. Also the usage of parts of the report , especially in connection with wrong and distorted facts is not allowed. (Version 1.2)

General Manager REDWELL MANUFAKTUR GMBH

Am Ökopark 5, A-8230 HartbergPhone: +43 3332 61105offi [email protected]

HELLENIC REPUBLIC LABORATORY OF HEAT TRANSFER AND SCHOOL OF ENGINEERING

ENVIRONMENTAL ENGINEERING Professor Dr.-Ing. Agis M.Papadopoulos

ARISTOTLE Phone: +30 2310 996015 Fax: +30 2310 996012 Thessaloniki, 26/11/10 UNIVERSITY e-mail: [email protected]

MECHANICAL ENGINEERING DEPARTMENT

THESSALONIKI URL: http://aix.meng.auth.gr Ref. No: 385/10 ENERGY SECTION

A preface to the study

The construction branch accounts the most for the energy and resources consumption amongst all

other branches in Europe, whilst it produces significant amounts of demolition waste, without being

very efficient in its reuse and recycling.

A huge potential lies, however, precisely in this situation, as the branch presents the single most

important potential for a sustainable approach of the anthropogenic environment.

It is of interest to notice, that almost forty years after the first oil crisis, space heating demand of

residential buildings remains the most interesting field to save energy. In addition one cannot

neglect to consider the issues of thermal comfort and indoor air quality, which are far more

important today than they used to be thirty years ago, as they are tightly linked to the energy

performance of buildings and, reasonably enough, to their operational expenses.

The evaluation of space heating systems, and therefore also of infrared radiative systems is, in this

line of approach, a necessity.

It is not an easy task, as the evaluation of heating power and efficiency of radiative systems is

depending to a much larger extent on parameters like the quality of the building shell’s thermal

insulation and its thermal storage capacity, as well as on the control and regulation of the systems,

compared to the one of conventional, convective systems. The lack of respective EN standards does

not make this task easier.

The research project „Evaluation of Redwell Infrared Heating Systems”, was carried out in the

Laboratory of Heat Transfer and Environmental Engineering, at the Mechanical Engineering

Department of the Aristotle University of Thessaloniki, funded by Redwell Manufaktur GmbH and in

the period between May 2009 and July 2010. The evaluation was based on a life cycle approach and

on the comparative consideration of the most popular space heating systems.

Considering their energy efficiency, Redwell Infrared heating systems are efficient and effective, as

one can deduce from the comparison between those and conventional systems. Redwell systems

SCHOOL OF ENGINEERING ■ BOX 483 ■ ARISTOTLE UNIVERSITY THESSALONIKI ■ GR-541 24 THESSALONIKI ■ GREECE

rank amongst the leading ones, considering their primary energy demand and their eco‐efficiency

over the systems’ life cycle. The same applies with respect to the operational expenses and the

feasibility of the systems considered, with Redwell systems being highly competitive.

When it comes to thermal comfort, one cannot fail to notice the clear advantage of Redwell systems,

compared to conventional heating systems with convective baseboard heaters, provided that the

building shell is well thermally insulated.

Finally, one can only stress the necessity for a European EN standard on infrared radiative heating

systems, within the umbrella of the space heating systems standard, in order to be able to evaluate

these efficient systems correctly and fairly and in a way conforming to the demands set by

contemporary regulations like the German EnEV 2009.

For the effective co‐operation within this project we would like to thank the managing director of the

Redwell Manufaktur GmbH company, Mr. Michael Buschhoff, as well as the head of distribution DI

Mr. Werner Erhart.

For the elaboration of this study I would like to thank the staff members of our Laboratory and in

particular:

Dipl.‐Ing. Alex Adam (Mr.)

Dr.‐Ing. Dimitrios Anastaselos (Mr.)

Dr.‐Ing. Simos Oxizidis (Mr.)

Dipl‐Ing. Ifigeneia Theodoridou (Ms.)

Thessaloniki, November 2010

Professor Dr.‐Ing. Agis M. Papadopoulos

SCHOOL OF ENGINEERING ■ BOX 483 ■ ARISTOTLE UNIVERSITY THESSALONIKI ■ GR-541 24 THESSALONIKI ■ GREECE

LABORATORY OF HEAT TRANSFER & ENVIRONMENTAL ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING

ARISTOTLE UNIVERSITY THESSALONIKI GR-54124 THESSALONIKI TEL. +30 2310 996015 FAX. +30 2310 996012

Contents

Contents 2

Task 3

Objectives 3

1. Objectively comparable parameters 3

2. Comparison to conventional heating systems 3

3. Re‐definition of a category for REDWELL Infrared Heaters 3

Fundamentals for the calculation 4

1. Norms and regulations 4

2. Methodology of the EnEV 5

3. Expenditure factor for REDWELL Infrared Heaters 5

4. Heating Systems Examined 8

5. Test object 8

Results 10

1. Evaluation of the tested REDWELL Infrared Heaters 10

Energy evaluation 10

Comprehensive evaluation of the different heating systems 10

Most important operational aspects 10

2. Adjusted utilization factors of the different heating systems 11

3. Primary energy use of the different heating systems 11

4. Life cycle Analysis and eco‐efficiency 12

5. Feasibility Study 13

6. Thermal comfort 19

Summary 23

Conclusion 23



3

Task In the context of a research project, our laboratory was asked by REDWELL MANUFAKTUR GmbH to

conduct a comprehensive analysis and test the "REDWELL Infrared Heating Systems" and compare

them to traditional conventional heating systems (direct electrical, oil, gas and heat pump heating

systems). This study should also be considered as a recommendation to the political decision makers

(minister of the environment) and/or European energy offices to view the REDWELL infrared heaters,

based on their excellent overall characteristics, not as an electrical direct heater but as a distinctive,

re‐defined heating system.

Objectives

1. Objectively comparable parameters

The evaluation of the REDWELL infrared heaters is to be made based on the objectively comparable

following parameters:

Efficiency (primary energy demand, capacity and performance, GWP (Global Warming

Potential))

Cost effectiveness (purchase , installation and running costs)

Quality (fabrication, materials, warranties)

Thermal comfort (comparable key figures)

Environmental impact

2. Comparison to conventional heating systems

All parameters analyzed are compared by using the heating systems mentioned below:

Direct electrical heating

Oil fired heating

Gas fired heating

Air‐to‐water heat pump and water‐to‐water heat pump (combined with underfloor heating)

Integrated system featuring hot water preparation by solar thermal systems

Integrated system featuring with photovoltaic system for power generation

3. Re‐definition of a category for REDWELL Infrared Heaters

The laboratory results and practica Microsoft Office Outlook.lnk l field trials show the specific

position of the REDWELL infrared heaters and the necessity of a re‐definition for a completely new

heating system category.



4

Fundamentals for the calculation

1. Norms and regulations

The calculations were carried out based on the following norms and regulations, with their most

important boundary values used being the following:

• EnEV 2009 (Energy Conservation Regulation 2009)

The calculations were made according to the requirements of the EnEV, part 4 (facilities for heating,

cooling and room ventilation technology as well as hot water supply) under consideration of the

default values as defined in appendix 1 (§3 and §9) requirements for residential buildings and 2 (§4

and §9) requirements for non‐residential buildings and based on DIN 4701. The most important

norms and regulations of the EnEV used, are:

DIN V 18599, part 1 to 10, Energy analysis of buildings

DIN V 4108‐6:2003, Calculating the annual heating and annual heating energy use

DIN V 4108‐2:2003, Minimum requirements for thermal protection

DIN V 4701‐10:2003, Energy analysis of heating and ventilation systems

DIN V 4701‐12:2004, Energy analysis of heating and ventilation systems in existing buildings

DIN EN 832:2003, Calculation of the heating energy use, residential buildings

DIN EN ISO 6946:2003, Building components and building elements ‐ Thermal resistance and thermal

transmittance

DIN EN ISO 13789:1999, Specific transmission heat loss coefficient

DIN EN ISO 13370:1998, Heat transfer via the ground

DIN EN ISO 10077‐1:2000, Thermal performance of windows, doors and shutters

EN 13790 Energy Conservation Regulation 13790

Thermal comfort evaluated according to EN‐ISO 7730 and ASHRAE 55

Calculations for climatic conditions of Thessaloniki, Greece

Simulation for climatic conditions of different European climatic regions.

REDWELL Infrared Heater

• Wall system, 900 W output, 90% emitted by radiation, 10% by convection, temperature

differential of 0,5 to 2°C

Convective Systems

• Fuel oil fired system with a feed temperature of 70°C and a 20 °C temperature drop. Mean

annual performance coefficient 85%



5

2. Methodology of the EnEV

The following demonstrates the methodology of the EnEV, the necessity of the expenditure

factor ep and highlights the essential data used.

Figure 1. Methodology of the EnEV (Energy Conservation Regulation)

3. Expenditure factor for REDWELL Infrared Heaters

The expenditure factor ep is determined according to DIN 4701‐10 and is generally determinable

based on standard values. The methods described here allow a consideration of device‐specific key

values which are mentioned in the production manuals.

A part of the research project was to determine, that a REDWELL infrared heater can achieve a

higher output than theoretically possible, regarding the installed electrical power, and this

conforming to DIN. This can only be shown in comparison to conventional convective heating in two

ways:

a) by evaluating the heating of the building shell and the interacting radiation of the walls.

b) by evaluating the better thermal comfort, which leads to a reduction of the air temperature

and therefore lower energy use.

These methods allow a consideration of device‐specific key values, but it is necessary to take into

account that both factors are building‐dependent:

The expenditure factor ep influences the primary energy use, viz.: ep = Qp/(Qh+Qw)



6

1. They depend on the insulation (Um or km).

2. They depend on the surface materials (radiative emission and absorption factors α and ε).

3. They depend on the thermal inertia of the building’s shell.

4. They depend on the ratio of ventilation to transmission losses.

Those four relations can principally be determined mathematically as well as experimentally. It is

necessary to achieve the highest accuracy, but also to provide generally applicable results and not

ones reduced to specific applications. In this sense a combination of measures and calculations has

been used with the aim to sustain the integrated comparison of a conventional convective heating

system and a REDWELL infrared heater with regard to thermal comfort and energy use.

i. A space heating with REDWELL infrared heaters heats surfaces of spatial boundaries as well as

the objects in the room and not directly the air of the room. Compared to this, a convective

heating system heats the total air of the room, which leads to a higher installation power of up to

+32%.

ii. With space heating by REDWELL infrared heaters, the room‐boundary surfaces are heated and

thereby the heat storage capacity of the building elements are exploited and the heat losses due

to ventilation are significantly lower. As a result, the installation power capacity can be rated by

up to 35% lower, compared to conventional, convective heating systems.

iii. As wall surfaces generally have a higher surface temperature, comparable good thermal comfort

conditions occur at up to 3,5°C lower air temperature values, in comparison to the convectional

heating systems. If there is effective regulation of the heater through the air temperature, the

result is a difference between the installation power capacity and the real running time of up to ‐

7%.

iv. As all of these results are strongly determined by the building dependent factors (1) ‐ (4), the

conclusion is that the in‐put generation for the room heating ("factor power in‐put" or "factor

energy expenditure" in the calculation according to EnEV can only be expressed as their

functions. From the arithmetic results one can conclude, that for a typical insulated building

according to EnEV 2009, with a heated volume per heater of up to 100 m³ (ca. 40m²), the factor

power in‐put or expenditure factor ep is valued 0,65. With very well‐insulated buildings (k<0,2

W/m²K) there are ep –values of 0,55 and lower achievable.



7

The simulations carried out resulted in the array of curves depicted in the following figure 2, where

the dependence of the energy efficiency value ep on the in‐put generation (correlates with the

thermal transmittance as relation of the influence of the insulation) and the room’s area ( with a very

sensitive thermostat) has been calculated.

Figure 2. Expenditure factor ep in dependence on the heated surface and the thermal transmittance

In this line of thought the following calculations of the primary energy use and the expenditure factor

for room heating with REDWELL infrared heaters can be approached with the aforementioned

values of power in‐put, corresponding to the requirements of EnEV, in a sound and reliable way.

0,50

0,55

0,60

0,65

0,70

0,75

0,80

0,85

0,90

0,95

1,00

12 15 20 25 30 35 40

Beheizte Flaeche pro Heizkoerper [m2]

0,28 0,3 0,33 0,35 0,4 0,45 0,5

Ein

gan

gsl

eist

un

g

WaermdurchgangskoeffizientHeated area per heater (m2)

Thermal transmissivity



8

4. Heating Systems Examined

The next table (table 1) shows the scenario to be analyzed for the building (construction year 1970).

Table 1. Parametrical analysis ‐ scenario for the study ‐ construction year 1970

Scenario Insulation Windows Conden‐

sing boiler

RED WELL infrared heaters

solar collectors

photo voltaic system

0 Basis (old oil‐boiler) yes yes old no no no

1 REDWELL infrared heaters

EnEv09 EnEv09 no yes no no

2 REDWELL infrared heater + solar collectors

EnEv09 EnEv09 no yes yes no

3 REDWELL infrared heater + solar collector + PV plant

EnEv09 EnEv09 no yes yes yes

4 air‐to‐water heat pump with underfloor heating

EnEv09 EnEv09 no no no no

5 water‐to‐water heat pump with underfloor heating

EnEv09 EnEv09 no no no no

6 direct electrical heating EnEv09 EnEv09 no no no no

7 new oil boiler EnEv09 EnEv09 no no no no

8 new oil boiler + solar coll. EnEv09 EnEv09 no no yes no

9 new gas boiler EnEv09 EnEv09 no no no no

10 new gas boiler + solar collectors

EnEv09 EnEv09 new no yes no

5. Test object

For the life cycle analysis of the building, the CML 2001 method (CML 2 baseline method, 2001) was

used. The calculations were carried out with the software AKZ Simapro (PRé Consultants, 2009)

version 7.1 whereby Ecoinvent Software version 2.1 served as databank. The twin family house is

situated in an urban area, in central Germany, in Frankfurt am Main (figure 3). According to this, the

climatic data of Frankfurt am Main have been used (table 2).

Position "Frankfurt am, Main", [N 50° 2'] [E 8° 36'] required indoor temperature = 19.0 °C

Table 2. Data for the dimensioning of the heating systems Source: "Climate Design Data 2009 ASHRAE Handbook"

maximal

temperature [oC]

day temperature [

oC]

wind speed [m/s] wind direction

heating period ‐10.5 0 3.2 30

cooling period 30.8 10.6 3.7 210



9

Figure 3. Views of the twin family house analyzed

Table 3. Typical building components and their U‐values for a building of the seventies Construction year 1970

Construction component

construction (from outside to inside) U‐values [W/m2K]

external wall • plaster mortar of lime • armed concrete • lime or cement plaster

3,69

cellar ceiling • min. impact noise insulation • concrete pavements, ribbed slab or steal stone slab

1,59

flat roof • lime plaster • steal stone slab tv 600/190 • lime or cement plaster

2,12

inclined roof • lime plaster • wood fibre board • air layer ventilated • support batten • counter batten • roofing

1,51

windows 2‐pane insulating glazing wooden frame without thermal insulation 4,3



10

Results

1. Analysis of the tested REDWELL Infrared Heaters

Energy evaluation

For the optimization of the REDWELL heaters and for the study of the operational scenarios, the

building was dynamically simulated with the software Energy Plus. In practical test runs at a mean

surface temperature of about 95°C on the REDWELL infrared heaters, a constant radiation

percentage of 90% was measured. This occurred by measuring the electric input power and the

resulting difference to the calculated radiation power based on measuring the surface temperature.

This difference represents the convective part of the system.

Comprehensive evaluation of the different heating systems

For the lifecycle analysis of the building the CML 2001 method (CML 2 baseline method, 2001) was

used. The calculations occurred with the software AKZ SimaPro (PRé Consultants, 2009) version 7.1

and Ecoinvent Software version 2.1 served as databank.

The most important operational aspects

Building shell

The building shell was recalculated by achieving the reference values of the EnEV for the thermal

transmittance with the help of an external thermal insulation composite system (ETICS). Based on

this, the external construction elements were insulated, so that the requirements of the EnEV were

fulfilled.

Heating Systems

In each of the different variations the old oil‐fired boiler was replaced by a new boiler (oil or gas fired

one) with better efficiency, or by an electrical direct heating, a hot pump heating or by a REDWELL

infrared heater.

Renewable Energies

To reach the best result regarding energy and environmental efficiency, the heating systems were

combined with renewable energy systems. These are photovoltaic systems to support the

generation of power in operating REDWELL infrared heaters and solar thermal collectors for the

water heating.



11

2. Adjusted utilization degrees of the different heating systems

The results for the building of the year 1970 with regard to the efficiency and utilization degrees are

shown in table 4.

Table 4. Degrees of efficiency and utilization of the systems and the resulting expenditure factors

Scenario

degree of efficiency

degree of utilization

expenditure factor ep

0 Basis (old oil boiler) 0.85 0.85 1.18

1 REDWELL infrared heater 1.00 1.54 0.65

2 REDWELL infrared heater + solar collectors 1.00 1.54 0.65

3 REDWELL infrared heater + solar collectors + photovoltaic plant

1.00 1.54 0.65

4 air‐to‐water heat pump with floor heating 2.5 (COP) 2.5 0.40


3.5 (COP) 3.5 0.29

6 direct electrical heating 1.00 1.00 1.00

7 new oil boiler 0.94 0.94 1.06

8 new oil boiler + solar collectors 0.94 0.94 1.06

9 new gas boiler 0.95 0.95 1.05

10 new gas boiler + solar collectors 0.95 0.95 1.05

3. Primary energy use of the different heating systems

Using the table 5 below, one can see that only new gas‐ or oil‐fired boiler systems achieve a better

total energy requirement then REDWELL infrared heaters. In combination with regenerative energy

systems (solar collectors and photovoltaic) the lowest primary energy use with REDWELL infrared

heaters is achieved. Direct electric heating or air‐to‐water heat pumps consistently achieve between

+20 to +40% higher primary energy use compared to REDWELL infrared heaters.

The primary energy factor, which depends on each country’s energy mix, has an important influence

on the calculation of the heat and hot water requirements. Interacting between this primary energy

factor and the energy expenditure factor, as well as the utilization degree of the system one gets

from the heat demand to the primary energy demand, which is directly comparable between the

different systems.

Qp = (Qh+Qw) * ep .



12

Table 5. Primary energy use basis Germany for the building of 1970.

Scenarios

heat require‐ment QH

primary energy factor

Germany

hot water requirement

Qw

primary energy factor

Germany

primary energy

requirement Qp

kWh/m2a fp kWh/m

2a fp kWh/m

2a

0 Basis (old oil boiler) 327.59 1.15 12.58 2.70 401.4 1 REDWELL infrared heater 152.64 2.70 12.28 2.70 107.2 2 REDWELL infrared heater + solar collectors 113.85 2.70 0.00 74.0

3 REDWELL infrared heater + solar collectors + photovoltaic system

41.54 2.70 0.00 2.70 27.0


341.72 2.70 12.28 2.70 141.6


369.10 2.70 12.28 2.70 110.6

6 direct electrical heating 133.92 2.70 12.28 2.70 146.2 7 new oil boiler 69.51 1.15 12.28 2.70 86.7 8 new oil boiler with solar collectors 50.57 1.15 0.00 2.70 53.6 9 new gas boiler 67.62 1.15 12.28 2.70 83.9 10 new gas boiler with solar collectors 48.38 1.15 0.00 2.70 50.8

4. Life cycle analysis and eco‐efficiency

To get a directly comparable result between the different scenarios, the evaluation factors (costs,

primary energy use and eco‐efficiency) need to be normalised. One can obtain comparable

conclusions according to table 6 only with the right corrector factors. These are defined as a non‐

dimensional value ‐ performance (life cycle) ‐ where the smallest value represents the overall most

favourable heating system. The calculation of the performance (life cycle) is done with the

aforementioned Software AKZ SimaPro (PRé Consultants, 2009) version 7.1 and the data bank

Software Ecoinvent version 2.1. This one takes into consideration the whole life cycle of the systems

used ‐ from production and operation, to maintenance, disassembly and disposal.

Table 6. Results of the eco‐efficiency for the 1970 building

Scenario Primary energy use

GWP (Global Warming Potential)

Performance (life cycle)

kWh/m2a kg CO2 eq ‐

0 Basis (old oil boiler) 401.4 35,320 267.6

1 REDWELL infrared heater 107.2 8,059 89.4

2 REDWELL infrared heater + solar collectors

74.0 5,570 68.1

3 REDWELL infrared heater + solar collectors + photovoltaic system

27.0 2,030 36.8


141.6 8,323 92.3


110.6 10,654 112.6

6 direct electrical heating 146.2 11,000 115.3

7 new oil boiler 86.7 8,618 86.1

8 new oil boiler with solar collectors

53.6 5,124 66.1

9 new gas boiler 83.9 7,040 74.5

10 new gas boiler with solar collectors 50.8 4.547 53.0



13

In table 6 it becomes evident that only the gas‐fired‐heating system (new gas boiler) achieves a

better performance factor of approx. 5% in comparison to the REDWELL infrared heater. All other

heating systems, such as air‐to‐water heat pump, direct electrical heating and oil boiler are

definitively less favourable compared to the REDWELL Infrared Heating System.

5. Feasibility Study

Based on the tables 7 and 8, in which the costs of the different systems are shown both for a

renovation and for a new construction, the feasibility study for these systems was carried out (fig. 4‐

8).

The following marginal conditions represent the base for the calculation of feasibility:

Energy costs status: April 2010, Germany

Inflation rate: 1.5 %

Capital costs: 2.0%

Observation period : 20 years (projection of the operative costs for 20 years)

Saving always relative to the old oil boiler (no additional insulation measurements

considered)



14

Table 7. Cost description ‐ renovation scenario ( in EUR) Scenarios

Redwell heaters

Redwell heater + solar

collectors


collectors + photovoltaic

system

air‐to‐water heat pump

water‐to‐water

heat pump

direct electrical heating

new oil boiler

new oil boiler + solar collectors

new gas boiler

new gas boiler + solar collectors

Investment costs (one‐time)

Heater 14,500 14,500 14,500 18,000 21,000 9,500 4,000 4,000 4,500 4,500

Conduit for underfloor heating

‐ ‐ ‐ 11,500 11,500 ‐ ‐ ‐ ‐ ‐

Installation solar collectors

‐ 12,000 12,000 ‐ ‐ ‐ ‐ 12,000 ‐ 12,000

Installation photovoltaic

‐ ‐ 24,500 ‐ ‐ ‐ ‐ ‐ ‐ ‐

Total investment costs

14,500 26,500 51,000 29,500 32,500 9,500 4,000 16,000 4,500 16,500

Running costs (ongoing)

Plus energy costs photovoltaic system

‐ ‐ 9,100 ‐ ‐ ‐ ‐ ‐ ‐ ‐

Energy costs 0.193 €/kWh

0.193 €/kWh 0.193 €/kWh 0.193 €/kWh 0.193 €/kWh 0.193 €/kWh

0.63 €/l 0.63 €/l 5,5 cent/kWh 5,5 cent/kWh

Maintenance costs ‐ 100 €/year 200 €/ year 100 €/ year 100 €/ year ‐ 150 €/ year 250 €/ year 150 €/ year 250 €/ year

Total running costs

3,132 2,164 ‐6,936 4,140 3,234 4,275 3,044 1,524 2,904 1,335

Total over 20 years ‐88,002 ‐79,649 107,467 ‐129,016 ‐109,751 ‐111,828 ‐78,972 ‐57,634 ‐76,186 ‐53,709



15

Table 8. Cost description – New construction scenario (in EUR) Scenarios

Redwell heater


collectors


collectors + photovoltaic

system

air‐to‐water heat pump

water‐to‐water heat

pump

direct electrical heating

new oil boiler

new oil boiler + solar collectors

new gas boiler

new gas boiler + solar collectors

Investment costs (one‐time)

Heater 14,500 14,500 14,500 18,000 21,000 9,500 4,000 4,000 4,500 4,500

Conduits ‐ ‐ ‐ ‐ ‐ ‐ 8,500 9,000 8,500 9,000

Radiator ‐ ‐ ‐ ‐ ‐ ‐ 4,200 4,200 4,200 4,200

Conduit for underfloor heating

‐ ‐ ‐ 11,500 11,500 ‐ ‐ ‐ ‐ ‐

Heating room + chimney

‐ ‐ ‐ ‐ ‐ ‐ 6,000 6,000 6,000 6,000

Installation of solar collectors

‐ 12,000 12,000 ‐ ‐ ‐ ‐ 12,000 ‐ 12,000

Installation photovoltaic

‐ ‐ 24,500 ‐ ‐ ‐ ‐ ‐ ‐ ‐

Total investment costs

14,500 26,500 51,000 29,500 32,500 9,500 22,700 36,200 23,200 35,700

Running costs (ongoing)

Plus energy costs photovoltaic system

‐ ‐ 9,100 ‐ ‐ ‐ ‐ ‐ ‐ ‐

Energy costs 0.193 €/kWh

0.193 €/kWh 0.193 €/kWh 0.193 €/kWh 0.193 €/kWh 0.193 €/kWh

0.63 €/l 0.63 €/l 5.5 cent/kWh 5.5 cent/kWh

Maintenance costs ‐ 100 €/year 200 €/ year 100 €/ year 100 €/ year ‐ 150 €/ year 250 €/ year 150 €/ year 250 €/ year

Total running costs

2,261 1,560 ‐8,311 2,500 2,368 3,521 2,493 1,358 2,171 1,128

Total over 20 years ‐67,577 ‐65,470 139,756 ‐98,512 ‐89,429 ‐92,140 ‐84,729 ‐73,449 ‐60,477 ‐48,842



16

In the tables 7 and 8 one can see that REDWELL infrared heaters are considerably more cost effective

in the renovation scenario than heat pumps or direct electrical heating systems. Here again only oil‐

and gas‐fired boilers, running on fossil fuels, are cheaper. In the new construction scenario,

REDWELL infrared heaters are by far the cheapest total alternative (purchase and running costs); in

interaction with photovoltaics one can achieve high total returns due to the electricity sales, much

higher than with all of the other heating systems.

The performance reduction of heat pumps, with increasing lifetime has been considered, as well as

the loss of efficiency of all other studied systems. Therefore another important advantage of

REDWELL infrared heaters becomes evident: the constant, maintenance‐free and constant over their

lifetime performance.

Regarding the running costs of the different heating systems for the building, they are shown in the

following figures. Smaller values correspond to better performance and indicate a more favourable

system (fig. 4 to 7).

Figure 4. View of the total investment costs of the heating systems (building from 1970) including building's insulation



17

Figure 5. Feasibility calculation of the investment costs of the heating systems (building from 1970) ‐ renovation scenario

Figure 6. Comprehensive cost overview of the heating systems ( building from 1970) + running costs (20 years) ‐ renovation scenario



18

Figure 7. Feasibility calculation of the investment costs of heating systems ‐ new construction scenario

Figure 8. Comprehensive cost overview of the heating systems + running costs (20 years) ‐ new construction scenario



19

6. Thermal comfort

The thermal comfort in a room is significantly determined by the relative humidity. As a hygienic

compromise of the different requirements, the limit values of 40% and 60% apply in general.

Thereby the following risks are prevented:

reduction of sultriness and at the same time lowers subjection to infections.

reduction of odour nuisance

increased defence of the skin against microbes, avoidance of electrostatic charge and

prevention of mould and fungal growth

To show the interaction between the physiological processes in the body and the physical exchange

with the environment, Prof. Povl Ole Fanger [Fanger 1972] developed in 1969 a

statistic/mathematical method of objectivised presentation of thermal comfort. Hereby, the

fulfilment of thermal comfort is basically seen as an energy service, which has to be provided by the

building and its technology.

Predicted Mean Vote (PMV) & Predicted Percentage of Dissatisfied (PPD)

According to ÖNORM EN ISO 7730 [ÖNORM EN ISO 7730:2006], thermal comfort is defined as the

feeling, which expresses satisfaction with the environmental climate. Dissatisfaction can be

expressed by discomfort of the body on the whole, due to the impact of heat or cold.

Already in the sixties, Fanger developed the so called „Predicted Mean Vote“ from these factors and

through large‐scale laboratory and field trials. This is a value to determine the statistic average vote

of a human group. The heat balance is taken as a basis, as this is frequently done in the technical

sense, and is determined by input meaning heat production and output meaning heat dissipation.

The relationship between PMV and PPD is the fact that, if this balance is equal to zero, the body has

to make no effort to achieve a balance. If this difference differentiates from zero, the organism has to

provide equilibrium and this is felt as discomfort. If the calculation diverges into the negative area, it

means that firstly these conditions are felt as too cold and secondly that the predicted percentage of

dissatisfaction increases. The PPD index reacts in the same way, if the PMV index changes to

positive, the environment is felt as too warm. Figure 9 presents this relationship again, whereby

PMV:"Predicted‐Meam‐Vote" = the predicted mean vote of the climate

PMV: "Predicted‐Percentage‐of Dissatisfied" = predicted percentage of the population dissatisfied

with the climate.

The optimum, means a low number of dissatisfied persons, which according to Fanger is defined by

5% at best, is achieved, if the calculation of the mean predicted vote is equal to zero.



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Annotation Fanger ‐ Skala percentage dissatisfied

cold ‐3 99,1

cool ‐2 76,8

slightly cool ‐1 26,1

neutral 0 5,0

slightly warm 1 26,1

warm 2 76,8

hot 3 99,1

Figure 9. Relationship PMV and PPD and the corresponding feeling according to ÖNORM 7730 [ÖNORM 7730:2006, S.:6]

Figure 10. PMV Rate (year of construction 1970)

Betriebszeit Betriebszeit



21

Figure 11. PPD Rate (year of construction 1970)

In figure 10 of the building of 1970 it is evident that during the heating operation only REDWELL

infrared heaters can be found within the thermal comfort limits, respectively as shown in figure 11,

REDWELL infrared heaters come nearest to the optimum of the 0% PPD‐rate.

Criteria of local comfort

Apart from criteria of statistical comfort, further criteria can be determined to define thermal

comfort. In this context the mean monthly changes of temperature of certain surfaces were analysed

and shown in figure 12. The values correspond to the mean surface temperatures for all floors after

the latest renovation measures for the 1970 constructed building.

Betriebszeit Betriebszeit



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Figure 12. internal temperatures of surfaces of a characteristic cellar wall (year of construction 1970)

One can see that during the operation of the different heating systems, the REDWELL infrared

heaters achieve surface temperatures on the inside wall which are generally by 0,5‐1,5°C higher than

the surface temperature when heating with a new gas‐fired boiler. Furthermore, this curve for

REDWELL infrared heaters is valid for all walls of a room, as opposed to the curves for the gas‐fired

boiler system, which is only valid for the wall area around the heater. All the other wall surfaces are

still significantly colder. This condition contributes considerably to the improvement of thermal

comfort through the operation of REDWELL infrared heaters.



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Summary With regard to energy use, REDWELL infrared heaters are extremely efficient and effective, as one

can see in the comparison to conventional heating systems. When it comes to primary energy use as

well as to eco‐efficiency over the entire life cycle they rank amongst the best solutions. Even in

considering costs and feasibility, REDWELL infrared heaters produce impressive results, compared to

conventional heating systems

Regarding thermal comfort, REDWELL infrared heaters principally have the edge on all conventional

heating systems with convective heaters, provided the building shell is well insulated. Even when

comparing underfloor heating systems with high thermal inertia, the advantages of REDWELL

infrared heaters prevail. Also concerning their fabrication and their resulting durability the REDWELL

infrared heaters are unsurpassed, as they have no moving parts or fluid working medium, whereby

they have practically all modern quality distinctions and test certificates.

The use of REDWELL infrared heaters in well‐insulated buildings fulfils the existing requirements of

the EnEV 2009.

A combination of REDWELL infrared heaters and solar thermal and photovoltaic systems results in

an environmental, economical and energetic optimal overall solution, which outperforms any other

heating system. Especially in the refurbishment of old buildings, the use of REDWELL infrared

heaters is the most economical solution for the building owner. But also in new constructions,

REDWELL infrared heaters definitely represent an economically and ecologically reasonable

alternative to conventional heating systems.

Conclusion The study clearly shows that REDWELL infrared heaters have the absolute edge on other heating

systems such as direct electrical heating and air‐to‐water heat pumps, when considering all

economical and ecological aspects. Furthermore, they can be considered as feasible alternatives to

oil and gas heating, as well. This is the reason why we strongly recommend defining a special

category for Infrared Heaters within the different heating systems, in order to classify them in the

appropriate manner and in accordance with their high performance capacity in the systemic process

of EnEV 2009.

redwell-studie-uni-thessaloniki-v1.2-2011-en

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