Category Archives: BACKGROUND

Experiment set up

In this section the building, its analysed walls, the used measurement equipment and the test sequence are briefly presented. More details about the building and walls are included in (Porcar, 2004).

The building

The building analysed is being used as a workshop at the Plataforma Solar de Almeria (Tabernas, Almeria, Spain).

Its design includes some design strategies intending to save energy maintaining the desired comfort. The aim of these implemented features are the following:

• Overhangs size was calculated to allow solar gain into the room in winter, and to avoid it in summer.

• Windows have been diagonally placed to promote cross ventilation.

The building is being monitored to evaluate the effect of the implemented saving strategies, the degree of comfort achieved and also to validate simulation work.

Figure 1: Monitored building. Left: South fagade with window and overhang. Right: North

and east fagades.

This building is very useful as it allows applying sophisticated analysis tools and due to its simplicity and high degree of knowledge about its construction, it is possible to apply different approaches and to compare their results.

Analysed walls

The opaque walls of the building have been analysed. Figure 2 schematically presents these walls.



v 1



E [——————————————————— 1


3 to 5 cm Concrete

25 cm polystyrene cove

Indoors plaster

8 cm hollow bricks

Air chamber

Projected Polyurethane (2 cm aprox.)

Ceramic block 20X20X40

Indoors and outdoors plaster using mortar (1.5 cm)

North, East and West walls are identical. South wall is also identical except that it has a wider air chamber and also a 2cm polystyrene (PS15) panel attached on the indoors surface.

Figure 2: Constructive schemes of the analysed walls.


The following sensors have been installed:

• Four indoor and one outdoor air temperatures using PT100 four wire connected, protected from solar radiation and ventilated.

• Global horizontal and vertical solar radiation using thermoelectric pyranometers

• Heat flux density leaving the room through the ceiling, south, north and west wall using thermopile based transducers. All of them centred in each wall and embedded on its indoors surface.

• Relative humidity using capacitance transducers.

• Wind velocity sensors using optoelectronic transducers

• Wind direction using resistance based transducers

All these measurements have been read using a datalogger which A/D resolution is 16


Sensors where installed with the constraint that monitoring should not be intrusive and

taking into account that the building was being used as a workshop.

Meteorological sensors were installed near the building.

Test sequence

As it was intended to make compatible the normal use of the workshop with the measurements carried out, no tests strategy has been implemented in this case. However it is usual to use some kind of cooling or heating power to excite the system (Letherman et al, 1982).

In principle the normal use of heating and cooling devices could have been used for this purpose but due to the implemented saving strategies very low heating and cooling were required, so most of the time the building was in free evolution.

As weather conditions were the only external exciting signals available it was decided to use winter data for analysis, where these excitation signals were more powerful. So the following data were used:

Winter: Since the 20th of December 2003 to the 6th of January 2004. These data are graph in data in Figure 3 to Figure 6.

Figure 3: Measured Global Vertical Irradiance.

Figure 4: Measured indoors and Outdoors Temperatures.

Data were read each second, and averaged and recorded each ten minutes.

North and West Walls.



1 1


1 1 1




,1 l’l ll

л л

1 l,: ill II



ll 1

a i’j a

* — V tjjj-w




5 — r



Time (DAYS) — South Ceiling

Figure 6: Measured Heat Flux Density:
Ceiling and South Wall.

Feasibility of a sorption gas heat pump/solar chiller for houses

ir. A. B. Schaap, drs. M. J. de Bruijn, Ecofys, Kanaalweg 16-G 3526 KL Utrecht,

The Netherlands. A. Schaap@Ecofys. nl

The standard solar domestic hot water system (in the Netherlands around 3 m2 collector area and around 100 litre of storage capacity) is developing into a solar combi system with around 6 to 8 m2 of collector area and around 200 to 300 litre of storage volume. This combi system can deliver more than half of the hot water demand of an average single family house and a small part of the heating demand in winter. This system has a big surplus of energy in summer. This surplus can be used for air conditioning in combination with a sorption heat pump. In summer the solar system drives the sorption system to deliver cooling. In winter the sorption system is driven by the auxiliary burner as a heat pump to produce space heating. In this way a very high CO2 reduction can be accomplished, by using the sorption system as well as the solar system all year round. The feasibility of such a system was studied.

The natural gas boiler for space heating and hot water has reached its thermodynamic limit. The efficiency is near to 100 % of the higher heating value. The efficiency on domestic hot water is somewhat lower but this efficiency is rising rapidly.

The industry is searching for ways to overcome the 100 % barrier. There are several solutions for this challenge:

• An electrical compression heat pump.

• A combination of a natural gas boiler with a small electric heat pump.

• A natural gas (micro) combined heat and power system (internal combustion, Stirling or fuel cell)

• A natural gas driven sorption heat pump.

With these solutions the primary energy efficiency can be raised to 120 to 160 % of the higher heating value, by using the exergy of the combustion. All four solutions have their pros and cons and it is in this stage not clear which solution will dominate which part of the market. The general advantage of the sorption heat pump is that the operational costs are related to the costs of the heating fuel (natural gas, oil etc.) and hardly to the costs of electricity as the other three options are.

We are especially interested in a combination of the sorption heat pump with a solar thermal system. This can be accomplished in the following way. In summer the solar system drives the sorption system to deliver cooling (see figure 1). At the same time the solar system produces hot water with the gas boiler as auxiliary heater. The sorption system rejects heat to the ambient. In winter the sorption system is driven by the gas boiler as a heat pump to produce space heating. The sorption system extracts heat from the ambient. Hot water is produced by the solar system, by the sorption system and by the gas boiler. The solar system produces also a small part of the space heating demand. The cooling delivery system in summer can be the same system as the heating delivery system in winter. The heat rejection subsystem in summer can be the same system as the heat extraction subsystem in winter.

The aim of the study was to determine the feasibility of such a system. The market that we are aiming at is the cooling, heating and hot water demand of buildings. The buildings can be subdivided into single family houses and commercial and institutional buildings. We concentrated on the single family houses, because it is the largest market with the largest numbers of one single type of product.

The single family houses can be subdivided into existing and newly build houses and into:

• Detached houses (build apart from each other)

• Terraced houses (build in rows)

• Apartment buildings (in stacks of houses)

In the Netherlands there are about 6 million existing houses and every year about 70,000 houses are build. So with a replacement every 15 years on average, the replacement market is with approximately 400,000 units bigger than the market for newly build houses. Figures 2 and 3 give an overview of a solar sorption system in the summer and in the winter situation.

^ Y Ambient

Figure 2: Solar sorption cooling/gas driven heat pump in summer

We can see that a valve is needed to switch from summer operation (condenser delivers waste heat and evaporator delivers cooling) to the winter operation (condenser delivers heating and the evaporator extracts heat from the ambient). The heat delivery system can be the same system as the cold delivery system (for example floor/wall heating or air heating). The waste heat in summer and the source heat in winter can be delivered/extracted to/from the ambient air, or can be integrated with the ventilation system.

To be able to simulate the solar sorption system we need demand patterns of typical houses over a typical year. In The Netherlands newly build houses have to comply with an energy standard called the EPN (Energie Prestatie Normering). Of course it is allowed to build more energy efficient than the standard. In this way we came to two different typical newly build houses; a reference house build according to the energy standard and a minimum energy house in which the heating demand was reduced to the technical limits.

For the existing buildings we have also chosen two typical cases. The average house according to the Dutch national energy inquiry (BAK) and a big house with a double as high floor area, but the same construction. These four houses form a reasonable cross section of the Dutch single family housing market as a whole. The demand of existing apartment buildings will fit between the reference house and the average house. Newly build apartment buildings fit between the reference house and the minimum house.

With an Ecofys house simulation program we generated hourly values of the space heat demand for these four different single family houses.

Reference house: In 2003 newly built houses have to reach an EP (Energy Performance) value of 1.0 to obtain a building permit. The lower the EP the lower the heating demand (all other aspects equal). The NOVEm single family terraced reference house was chosen (1999 tuinkamer tussenwoning). The house is calculated with the EP calculation program and subsequently with an Ecofys house simulation program using the Test Reference Year for De Bilt to generate hourly values of the space heat demand. The house has a floor area of 111 m2 divided over two stories and an attic. It has a calculated heat demand for space heating of 10.8 GJ/year.

Minimum Energy house: This house has the same dimensions as the reference house. In this case however the heat loss of the house is reduced to the technical limits (thicker insulation and triple glazing). The calculated heat demand is only 5.8 GJ/year for space heating. In this calculation the internal heat production was lowered from 750 W (for the other three houses) to 400 W continuously, because we expect the people in such dwellings

to use energy efficient appliances. If not so the heating demand can even be as low as

1.5 GJ/year (comparable to a passive house).

Average house: This house is based on the heat demand for an average existing Dutch house (BAK 2001). The calculated space heat demand is 35 GJ/year.

Big house: This house has the same construction as the average house only the floor area is increased with a factor of two. This house was added because it can be expected that sorption systems will be first cost effective in houses with a high heat demand. The space heat demand is 64 GJ/year.

И CIE Overcast Sky CIE Clear Sky (June 21st — noon) CIE Clear Sky (Dec. 21st — noon) Figure 8 — Illuminance relative difference obtained with semispecular and specular finishing referred to matt finishing . Assessment and optimisation of a designed daylighting system

The second field of interest in the scanning sky simulator applications concerns the assessment of a specific daylighting system designed for buildings at the design stage.

The analysis is aimed at determining the most suitable solution in order to maximise the entrance of diffused skylight and meeting the daylight factor standard requirements, while screening at the same time direct component of solar light, so as to control overheating and glare phenomena. Forthis kind ofstudies, quantitative and qualitative data are collected for a larger number of conditions with the aim of reproducing to a greater extent daylight variations during the year, within an indoor environment. Consequently, the analysis protocol is based on the simulation of different sky condition (clear, overcast, intermediate), periods of the year (December, March and June) and hours of a single day (from sunrise to sunset), in order to appraise the environmental variations for a minimum and a maximum availability of external natural light, for different weather conditions and periods of the year.

These aims were at the basis of the study carried out for the daylighting design of the new Faculty of Maths, Natural Science and Physics library in Alessandria, which is presently at a design stage. The daylighting system conceived forthe library is a large south-oriented glazed surface equipped with a mobile micro-perforated aluminium louvershade. Quantitative and qualitative analysis were carried out for different louver tilt angles, in order to verify both the effectiveness of the screening effect and the internal availability of daylight during different periods of the year.

A similar procedure was used to assess the aluminium louvered shading system designed for the sky-light for of the new SACMI headquarter in Bologna. In this case, the screen was supposed to be fixed, so different louver tilt angles were tested so as to determine a suitable position representing a fair compromise forthe entire year between screening of direct sun-light and letting diffuse skylight in.

1. Conclusions

The paperdescribes the potential applications ofthe use ofscaled models and artificial scanning sky in the fields of daylighting design and research.

In particulartwo different categories ofapplications are highlighted: the comparison of environmental performances ofdifferent daylighting systems and the optimisation, during the design stage, of a specific daylighting system.

For the first category an exhaustive example, concerning the comparison of lighting environmental performances ofdifferent traditional shading devices, is presented. The systems, designed to ensure an equal energy performance (similar SF for both summer and winter period) were applied to the model of a sample classroom and tested under the artificial sky and sun. Results obtained through the simulations ofdifferent sky conditions and Sun paths showthe differences in the lighting performances, emphasising in particular best results for the horizontal fins and the external light shelf (considering daylight quantity, daylight penetration and uniformity over the cross section as evaluation criteria).

The quantitative and qualitative effect of different shading finishing was also assessed. Specularand semispecularfinishing used for internal light-shelves always produced higher illuminances and contributed to increase daylight penetration towards the rear part ofthe room. Nevertheless such finishing, and in particularthe specularone, created, when reached by direct sun light, high luminance areas on the ceiling, which can be a potential cause of discomfort glare.

For the optimisation of daylighting systems during the design stage, the use of a scanning sky simulatorallowed evaluation ofdesigned systems and comparison ofdifferent solutions: for instance the most effective tilt angle forfixed louvers of a shading device designed fora building skylight could be determined.

In conclusion, from the experiences carried out at the Daylighting Laboratory in Turin it comes out that the use ofscale models under artificial sky and sun is a useful tool for both daylighting design and daylighting research as it allows an accurate simulation ofdifferent daylight conditions (both standard or experimental), a quantitative and qualitative evaluation oflighting environmental performances and definition ofdaylighting systems’ geometric and photometric characteristics.

Guidelines for energy efficient refurbishment of primary schools at Catania (Italy)

Gianni Scudo: Department Building & Environment Science & Technology (BEST), Politecnico di Milano Via Durando 10, 20158 Milano, ITALY Tel.:+39 02 23995729 Email: aianni. scudo@Dolimi. it

Alessandro Rogora: Department Building & Environment Science & Technology (BEST), Politecnico di Milano Via Durando 10, 20158 Milano, ITALY Tel.:+39 02 23995728 Email: alessandro. rogora@polimi. it

Claudia Losa: Department Building & Environment Science & Technology (BEST), Politecnico di Milano Via Durando 10, 20158 Milano, ITALY Email: c. losa@inwind. it

Aim of the research was develop guidelines for the refurbishment of public school buildings in Catania climatic area.

Main objectives of guidelines are to help the planner during his/her work in order to reduce energy heating, cooling lighting compsution improving of the same time the comfort condition inside the classroom.

The research has been promoted by the Catania’s council with the objective to define a program of refurbishment of existing schools. The refurbishment should have considered both the building structure, the energy and the environmental performances of the schools. Aim of the research was to define specific guidelines for the refurbishment of the buildings and the surrounding areas to get the maximum energy and environmental effect at the lowest cost. The problem of comfort inside the buildings, with special attention to summer conditions, has been considered of the maximum importance and has been analysed together with the energy consumption due to heating, cooling and lighting.

The retrofit interventions proposed are based on four elements (indicators of quality):

— current building standards and regulations;

— energy efficiency;

— thermal and lighting comfort (winter and summer conditions);

— building safety.

The research is structured in three phases:

— survey of the schools and use of a computer model to simulate the thermal conditions;

— analysis of energy simulations obtained from the computer model;

— definition of the strategies of interventions.

Laboratory measurements

Evaporation flow rates

When plants are exposed to light they are able to take up carbon dioxide from the ambient air and produce carbohydrates under the use of light energy. The carbon dioxide uptake is accompanied by the loss of water, which is taken up by the root system. Water evaporation leads to a cooling of the leaf surface and produces a microclimate around the plants. The goal of the numerical model developed in the project is to determinate how this microclimate affects the energy balance of the builiding facade. To do so, the water flow rates evaporated by different species under different circumstances have been measured in order to use this

Temp 20 *C 30 "C

—growth chamber glasshouse —±—outdoor

Figure 4: Green layers orthogonal to the facade. Outdoor aspect at the left (by Nature) and indoor aspect at the right (by Arquitectura Produccions).

Figure 5: Evaporation flow rate. At the left, the same species grown in different conditions have different reactions to the same conditions. At the right, reaction of different species to the same conditions.

Figure 6: Global transmissivity and reflectivity Figure 7: Example of Montecarlo ray trac — of Parthenocissus Quenquifolia leafs in sum-ing simulation: Energy absorbed by earch mer and fall. Parthenocissus Quenquifolia leaf after multi­

ple reflexions in a canopy

data for the numerical model. Illustrative results of the experiments are presented in Fig. 5.

The evaporation flow rates depend not only on the plant specie and on the ambient con­ditions, but also on the ambient where the plant has grown. Thus, it will be convenient to repeat some of these measures in actual facades.

Optical properties of the leaves

Figure 8: Experimental set up to obtain data for the numerical models.

The optical properties of the plant leaves (transmissity and reflectivity) have been mea­sured in order to obtain data for the numerical model. Illustrative measures of Parthenocis­sus quenquifolia are presented in Fig. 6.

Lacasa — an Instrument for the Energy Analysis and — Optimisation of Buildings Including Technical Equipment

Solar-Institut Julich / Fachhochschule Aachen Heinrich-MuRmann-StraRe 5, 52428 Julich Tel.: 02461 / 99 -3532, Fax: 02461 / 99 -3570 www. sij. fh-aachen. de, info@sij. fh-aachen. de

K. Schwarzer, M. Werner, T. Hartz, L. Aliaga 1 Motivation

Experience with 20 different commercial simulation programs has been gathered at the Solar Institute in Julich. On the one hand, simulation programs with operator-friendly user interfaces for the design of standard systems are currently available. The advantages here are the short training period required and low price, but with the disadvantage of limited flexibility. On the other hand, there are programs available which offer flexibility in nearly all technical equipment concepts. The disadvantages here are the complicated operating in­structions which often lack clarity, and the long training period required.

Given this background, in 1996 the Solar Institute in Julich decided to develop computer models for solar thermal and conventional heating systems, using MATLAB-Simulink® /1/. At about the same time, and in the same Institute, the basics of a building model, which is the foundation of the toolbox "Lacasa” presented here, were established within the frame­work of both a dissertation and the project Solar-Campus Julich /2/.

Simple 1-D model

Temperature profile at top of panel

Bottom temperature profile

Figure 4. Temperature profiles (horizontal) at top and bottom of cavity for the case of Fig.2.

One-dimensional models for the two double fagade concepts described above have been developed by Charron and Athienitis [4]. Here, a simplified version of these models is employed for the case of Figure 2 in order to study the impact of major parameters such as convective heat transfer coefficient. Considering the fagade with PV as exterior layer we may represent it with the thermal network model shown in Figure 5.

Figure 5. Thermal network model of fagade with exterior PV (assuming isothermal surfaces); node b indicates the back panel interior surface.


The mean air temperature Tma is determined from a differential analysis which finds the air temperature as a function of vertical distance x. It is assumed that the air speed is constant, that is, air it is drawn into the window by a fan in the HVAC system fresh air intake. The actual air temperature T(x) is then used to determine the Tma. This is then employed to find the correct values of Tpv and Tb which are utilized to fine tune the calculations. Considering an element dx in the vertical direction, we have:

M-c-p-dT= W•dx-h-(Tpv — T) + W-dx-h-(Tb — t) (!)

where M = flow rate = V * A (V is average velocity and A is cross-sectional area) and W is width of fagade. Note that the convective coefficient h is an average for both cavity surfaces (in reality it will generally be higher on the hotter surface).

Note that in this simple model we assume equal convective heat transfer coefficient h for both cavity surfaces. The following ordinary differential equation is obtained:


a-—T + 2T= Tb + Tpv dx P


a :=

with Wh

T(x) ■

To —

(T b + T pv)




— X-2

T pv + T b

An exponential variation is obtained for the air temperature as follows:

Tb :

T pv



TmaU b + T rU 3 + T pvU r

U o’T o + U a — Tma + Ur-T b + Spv

The PV and back panel temperatures are obtained as:

where U represents conductance between the various nodes (Uo= A ho, Ur= A hr,

Ua= Ub= A h, and U3 is negligible).

The average surface temperatures predicted with this model for various values of the convective heat transfer coefficient are compared in Table 1. Note that there is significant uncertainty about the value of this coefficient and this team is currently performing CFD studies on this topic. Nevertheless, simple models such as the one presented above are instrumental in studying the fundamentals of the problem. A value of 14 W/m2K was employed for the exterior film coefficient ho (other measurements also confirm this value) and 4.0 for the radiation heat transfer coefficient hr.

As can be seen from Table 1, a value of about 8 W/m2K for h gives reasonably accurate temperature predictions for the air and for the two surfaces. Note that the accuracy of the average velocity measurement is about 5%. The value of the convective heat transfer

coefficient is relatively high because of the short height of the PV panel (about 1m) and as expected h is high near the leading edge of the boundary layer forming on the PV panel.

Table 1. Predictions of 1-D model as a function of convective heat transfer coefficient Incident solar radiation is 989 W/m2, Jan. 26, 2004

Convective heat transfer coefficient h,

W/(m2 0C)

Average temperature of PV panel,


Average air temperature rise between bottom and top of PV, 0C



























Experimental results




The results of an experimental study and a simple analytical model for a double skin fagade with integrated photovoltaic panels are presented and analyzed. Air enters from the bottom part of the fagade through an intake, gets heated as it flows upwards driven by buoyancy and a fan, and finally enters the HVAC system. During the winter, fresh air increases the efficiency of the photovoltaic panels as it flows around them while at the same time it is preheated. Experimental results show that combined thermal-electric efficiency of the system could easily exceed 70% with airflow on both sides of the PV panel.

A major result of the study is estimation of the impact of the convective heat transfer coefficient. For velocities of about 0.6 m/s, an average coefficient of 8 W/m2K (over a height of 1 m) was found to give good agreement with experimental measurements for air temperature rise and for the average temperature of the panels.


The financial and in-kind support of this project from NSERC, ATS, Dept of Natural Resources of Quebec, and CETC-Varennes is gratefully acknowledged.


1. IEA 1999, Workshop on PV/Thermal Solar Systems, Amersfoot, Netherlands, 17-18 Sep.

2. Lloret et al. (1995) The Mataro public library: a 53 KWp grid connected building with integrated PV — thermal multifunctional modules. 13th European PV Solar Energy Conference, Nice, France, pp. 490 — 493.

3. D. Infield, L. Mei, U. Eicker, "Thermal performance estimation for ventilated PV fagades”, Solar Energy, Vol. 76, pp. 93-98

4. Charron R. and Athienitis A. K., 2003, Optimization of the Performance of PV-Integrated Double-Fagades, Proc. of International Solar Energy Society World Congress, Goteborg, June.


At high hydrogen concentrations in the residual medium, the (EIHIS, EIHCIS, MADHM) effects play a positive role of a peculiar safety device against the excessive heat flow during hot time of the day.

These effects perfectly match the present-day concepts in the field of quantum chemistry [42] and classical thermodynamics [43-47]. In accordance with the classification of classical thermodynamics, a chemically active open complicated thermodynamic system has been considered in this review [45]. The set of dissipative processes being considered vividly demonstrates the non-equilibrium ability to serve as a source of ordering through fluctuations. The (EIHIS, EIHCIS, MADHM) effects are the manifestation of self-arrangement in non-equilibrium systems. The discovery of these effects [6,7] shows the non-suitability of the description formalism of similar thermodynamic systems with superinsulation in the field of instability based on the Boltzman principle. During the experiments on reduction of the hydrogen concentration in the vacuum cavity of the filled cryogenic reservoir, the consecutive oscillatory and bifurcation processes of the residual hydrogen pressure variation have been noted.

So some instabilities, secondary bifurcations of time-periodic cycles observed have been noted. These bifurcations in case of a three-molecular models can be obtained analytically.

The investigation conducted has shown that a gradual decreasing of the amplitude of superinsulation heat conduction oscillations occurs at reduction of the residual hydrogen concentration.

Energy Measurements Results

Month and year








EPVS 2-001


ySMAControl Emeasured


September, 2003







October, 2003







November, 2003







December, 2003







January, 2004







February, 2004







Table 1 The results of monthly value of heat and electricity measurement

Monthly values of thermal and electrical measurements in the system described above and the results of a simulation for the period from September 2003 to February 2004 are presented in Table 1. From November 2003, thermal energy for space heating is obtained from a gas heater. But thermal energy for domestic hot water preparation is only partly covered with the gas heater. Diagram in Figure 5 shows monthly values of the fractions in thermal energy supply. It is obvious that the excess of thermal energy produced in solar collectors in September covers the shortage of thermal energy in October. In this case the additional heating from the gas heater is not required. Figure 6 shows the comparison between the simulation and measurements in the pilot project "Solar roof Spansko — Zagreb”.







I 150 100 50 0

User Friendly Heating Systems for Low energy and. Passive Multi Family Buildings

Wolfgang Streicher

Institute of Thermal Engineering, Graz University of Technology
Inffeldgasse 25/B, A-8010 Graz
Tel: +43-316-873-7306, Fax: +43-316-873-7305,

E-Mail: streicher@iwt. tugraz. at, heimrath@iwt. tugraz. at

Additional authors

Thomas Mach, Richard Heimrath, Karin Schweyer, Robert Kouba,
Institute of Thermal Engineering, Graz University of Technology, Austria
Alexander Thur, Dagmar Jahnig, Irene Bergmann,
Arbeitsgemeinschaft ERNEUERBARE ENERGIE, AEE INTEC, Austria
Jurgen Suschek-Berger, Harald Rohracher,

Interuniversitares Forschungszentrum fur Technik, Arbeit und Kultur, IFZ, Austria,
Helmut Krapmeier, Energieinstitut Vorarlberg, Austria


The energy demand of new buildings has been decreased significantly during the last 25 years. This is due to the development of new building materials and building technology. Whereas 10 years ago common windows had a U-value of 3 W/(m2K) today’s U-values are half of this at the same price. Similar developments have been achieved for other building materials which results in a specific energy demand of only one sixth (50 kWh/mPa) of today’s buildings compared to buildings 30 years ago without additional costs. With little higher investment cost the energy demand can be decreased even further.

Low energy buildings (or passivehouses) have different demands for the heating systems than conventional buildings. This paper deals with these demands and an analysis of various heating systems with respect to end-use and primary energy demand, greenhouse relevant emissions, heat delivery costs (including capital costs) and qualitative criteria.

The passivehouse is defined by

Max. 15 kWh/mFa space heat demand (with ventilation system with air heat recovery)

Max. 42 kWh/mPa total end use energy demand including electricity for HVAC and others Max. 120 kWh/mPa total primary energy demand

The main goal was the development of a comprehensive evaluation method for heating systems for buildings insulated according to passivehouse criteria.

This project was financed in the frame of the Austrian Research Initiative „Building of the Future" of the Federal Austrian Ministry of Transportation, Innovation and Technology (BMVIT).