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An intelligent window for optimal ventilation and minimum thermal loss

Final ReportSummary - CLIMAWIN (An intelligent window for optimal ventilation and minimum thermal loss)

The CLIMAWIN consortium, a group of European SME manufacturers and suppliers of windows and ventilation systems, aims to address a major market opportunity regarding energy efficient fenestration systems for renovation of residential and commercial buildings. Specifically, the consortium aims at developing a novel high-performance window with electronic operation of an auto-regulated natural ventilation system and electronic insulating night blind powered by solar power. The envisaged solution is expected to promote a paradigm shift for building renovation in the construction industry from expensive and energy intensive heating / cooling systems to cost efficient, healthy, and energy efficient intelligent windows.

The CLIMAWIN project has focused on establishing the necessary background knowledge in order to set the directions and goals for the development of a new intelligent ventilated window as well as on technical development work of specific technologies, development of window prototypes and on testing of these prototypes. The work and achieved results include the following:

- Investigation of thermal and energy performance of ventilated windows for 15 different glazing configurations, for 4 different climates (Denmark, Germany, France and United Kingdom) and for 3 different window orientations (South, West and North). Based on 9000 simulations two configurations has been identified to perform according to the goals of the project for investigated climates.
- Development of a new window frame system with a U-value below 0,8 W/m2K.
- Guidelines on the selection and use of solar shading devices for improvement of the preheating capacity of outdoor air and improved thermal insulation.
- Development of a CLIMAWIN design tool to assist the SMEs in selecting the optimum designs for customers and to document their expected energy savings.
- Design and construction of fully working ventilation units. Design and documentation of auxiliary items such as non-return valve and thermal actuator drive principle.
- Development of a new zone controller with CO2 measurement capability and capability for integration with communications system. Development of battery charging system including use of PV systems.
- Development of the two CLIMAWIN prototypes where a new ventilation system, a new wireless control system as well as PV energy production and battery storage is integrated.
- A thorough test of the CLIMAWIN prototypes, which documents well-functioning windows capable of controlling ventilation and solar shading according to the control strategies developed.

The project has been very successful. A window configuration has been developed that to a very large extent perform according to the project goals and the tests show that the developed prototype is well-functioning. The SME receives a lot attention and there is a fast growing market interest in the CLIMAWIN product. The potential market for the new CLIMAWIN product has been identified to be 3 million residential windows (0.57 m dwellings) at EUR 3.6bn and 8 million sq. metres non-residential windows (16 000 buildings).

Project context

Green buildings in a European context are buildings that ensure energy efficiency through less energy consumption and increased energy savings. This market is relatively fresh and awareness has risen rapidly in the last decade resulting in an increasing number of initiatives at the national and EU levels to incorporate energy efficiency in all aspects of buildings where permissible. Various national and EU level initiatives have been planned and launched to cost effectively reduce the energy consumption in this sectors. This realisation has prompted all the EU Member States to actively participate in the Kyoto Protocol and zero carbon housing initiatives which aim at CO2 reductions of 80 % by 2020 and achieve energy savings of 20 % by 2020 across the EU. This is reflected in the European Commission's Energy Performance of Buildings Directive (EPBD).

The EPBD was contrived as a compulsory initiative at the EU level and was launched in 2002. All the EU Member States are bound by this legislation and the aim is to completely implement the EPBD by 2020 to achieve energy consumption targets specified by this Directive in the premise of 25 %. Different member states have taken different approaches to implementing the legislation through national and EU level programmes to assess and classify buildings as green. The European Commission has introduced the Green Building programme according to which, for energy certification, the existing buildings have to improve the building by achieving 20 % savings in an upgrade and for new buildings they have to build one that is 25 % more efficient than the current building code in force to acknowledge and appreciate those building users and owners who make an effort towards sustainable construction. Grants, financial aids and tax subsidies are in various stages of being promoted in different nation states for the adoption of energy efficiency standards and to reduce the conflict of interest between builders and dwellers.

The industry's primary answer to increased competitive pressure in terms of innovation efforts has been focused on design, especially with regard to energy-efficiency. The potential for the latter is considerable: Nearly half of European energy consumption is spent on heating and cooling. In Northern Europe alone, approximately 40 % of energy consumption is used for heating. To reduce energy consumption, thermal loss is a key parameter since it accounts for 33 % of the consumption lost through windows and doors. This means that the energy consumption can be reduced 13 % by preventing thermal loss. Moreover, studies by e.g. the project's partners within the window industry indicate that around 70 % of thermal loss happens at night.

While certainly valid and important, the focus on energy efficiency has serious adverse effects. The window industry's response to the problem has been to improve thermal envelopes using better insulation materials in frames, glass as well as reducing air leaks. These concerns have lead to a sealing of buildings, including the installation of fixed pane windows, so as not to interfere with indoor temperature stabilisation attained by mechanical ventilation of air conditioning units. Building occupants' recurrent complaints regarding indoor well-being are referred to as 'sick building syndrome' (SBS) and the symptoms have been reported and found in modern, recently constructed buildings. SBS is a widely recognised phenomenon and an expensive liability when toxins become concentrated inside sealed office buildings. Energy efficient buildings have less exchange of fresh outdoor air - and thus ironically exacerbate the problem. Ventilation represents the most recognised and used method of reducing or eliminating IAQ problems. Ventilation of buildings in general may be done for several reasons, the most important one being to remove or dilute indoor generated pollutants. Ventilation is also needed to reduce the exposure from airborne microbes causing infectious diseases and for humidity control. In addition, natural ventilation nowadays can also be used for so called 'free cooling' - i.e. a way to control temperature through high flow rates so as to remove heat from the building to the outside. According to Säppanen, the developing technologies of natural ventilation and 'free cooling' can improve energy efficiency for a given IAQ up to 60 %.

Advances continue to be made in design and development of windows as suppliers seek to gain a competitive edge via product differentiation and performance improvement. The key driver has been the 'green building' movement, which primarily is concerned with energy efficiency. Since windows and doors constitute 'breaks' or points prone to facilitate thermal transfer in a structure, builders and customers have generally demanded 'tight' arrangements, such as vinyl windows with insulating glass, which seal off buildings. In addition to energy efficiency, other key innovation efforts concern materials research, improved styling and resistance to weather / break-in, simplified installation, greater energy efficiency, and decreased maintenance requirements.

Total global demand for windows and doors was USD 78 billion in 1999 and rose to USD 100 billion by 2004. Demand is, moreover, expected to exceed USD 130 billion by 2010. The annual rate of growth is expected to be around 5 percent - reflecting growth in building construction. Doors and windows each take up about 50 % of total demand - a ratio which has been relatively stable over the past 10 years. Worldwide, residential buildings account for roughly two thirds and non-residential buildings for one third of total demand for fenestration products. The market for windows is largely influenced by raw material costs, legal and regulatory considerations, technological innovations, and pricing patterns.

The industry is highly fragmented and SMEs find it difficult to compete as raw material and operating costs are on the rise. Therefore, the industry's rate of consolidation is expected to accelerate. Moreover, window manufacturing, like for other durable goods, is shifting towards developing countries. Underlying factors are, in particular, rising labour costs, but also the high growth rates of emerging markets. The customer base is dispersed, but end-user markets and applications are well defined. It is therefore relatively easy to substitute items from one maker for those of another supplier whereby local brand loyalty is easily eroded. Leading multinational companies are expanding their presence onto export markets by establishing manufacturing in areas of high growth and/or cheap labour or by acquiring firms already active in those areas.

Despite this significant market size, market depth and continuous growth, European SMEs in the sector are increasingly finding themselves under pressure and facing imperatives for generating new and innovative value propositions to the market.

Project objectives

The CLIMAWIN consortium, a group of European SME manufacturers and suppliers of windows and ventilation systems, aims to address a major market opportunity regarding energy efficient fenestration systems for renovation of residential and commercial buildings. Specifically, the consortium aims at developing a novel high-performance window with electronic operation of an auto-regulated natural ventilation system and electronic insulating night blind powered by solar power. Through in-situ smart sensors and radio frequency based technology (RFBT), the system will optimise, in real time, indoor climate on the basis of parameters such as indoor / outdoor temperature, CO2 and humidity etc., thereby providing better indoor climate and reducing thermal loss.

The envisaged solution is expected to promote a paradigm shift for building renovation in the construction industry from expensive and energy intensive heating / cooling systems to cost, health, and energy efficient intelligent windows. In Europe, only 2 % houses are newly built using green designs. Hence the majority of the old buildings need to be upgraded to meet the European energy efficiency targets. While minimising thermal losses is one crucial method, a pragmatic approach should avoid arresting ventilation completely which leads to suffocating enclosures. Instead, smart ventilation should be allowed maintaining a balance between indoor air quality and energy loss and also minimising energy loss during ventilation, which is the need for most old buildings which constitute the majority of buildings in Europe. Hence, the building renovation sector is a main market for Climawin. In a recent draft of EU's Energy Efficiency Action Plan, a target of renovating 15 million European buildings has been set to cut energy use by 2020.

The project will increase competitiveness of the participating SME manufacturers and their end-users by providing them with an innovative fenestration platform, which:

- significantly improves the energy efficiency of existing domestic and commercial buildings;
- improves indoor ventilation and subsequent improvement of dampness and humidity, a major problem especially in old buildings with lack of ventilation. This is a major cause of microbial growth, human health degradation, and damage to walls and structures;
- optimises, simultaneously with energy improvements, indoor air quality by reducing indoor air pollution (IAP), thus presenting a unique solution to the indoor air quality (IAQ) dilemma in building renovation by decoupling the unfortunate correlation between energy efficiency and poor air quality / sick building syndrome;
- provides radically improved and high return on investment for installation for both residential and commercial end-users.

The SME consortium has the capabilities to produce and market the new product, but lacks the full financial resources as well as the expertise to enable the required technological development. Therefore, the group has identified the research for SMEs programme as the suitable vehicle for overcoming the technological and financial barriers associated with the achievement of the objective.

CLIMAWIN seeks to decouple the window industry's innovation effort in energy efficiency from the conventional trade-off on indoor air quality by offering simultaneous and radical improvements on both parameters - thus effectively bridging the currently conflicting demands of the IAQ dilemma. Recent advancements and discoveries in smart sensor and communication technology drive the CLIMAWIN consortium's aspiration to develop and launch a much needed innovative and intelligent window system for the use in the European building industry.

Through the optimisation of thermal properties and minimisation of night-time heat loss, the intelligent CLIMAWIN system will significantly improve energy efficiency in both residential and in commercial buildings. Despite the window industry's continuous innovation effort, loss of heat and cooling continues to be an important barrier. CLIMAWIN will improve energy efficiency with up to 30 % measured against current offers on the market - representing a large competitiveness gain for the EU companies in the industry - and radically improved environmental and energy effects for commercial and residential end-users.

Project results:

The work in CLIAMAWIN was defined in nine work packages. They are the following:

WP1: Consortium management
Management of the project and coordination to other related research activities. Information about the management work packages can be found in the periodic report.

WP2: Exploitation and dissemination
The work is concentrated on developing a market analysis and business plan, protecting project results and early stage exploitation of the project results and successful market implementation.

WP3: Functional requirements, envelope definition and calculation
The activities is constructed on defining product features required by user and regulation, create definitions of functional requirements, hereunder: ventilation mechanism performance requirements, electronic control system etc. Test programme and various test rig specifications and review manufacturing processes.

WP4: System design and development
The work in WP4 is based on the results of WPs 5-7. Work has been centred on establishing specification and sizing methodology for systems components, establish installation and operational / maintenance methodologies, construct design methodology for complete installation designs. Also, integrate hydraulic, electronic power supply and control requirements.

WP5: Development of ventilation system
The primary task in WP5 has been the development and optimisation of the ventilation grille. Some of the development has been focussing on the air temperature passing the ventilation grille and the optimisation here off.

WP6: Energy optimisation and solar shade / night blind
The activities in this WP have been to develop a new innovation window element that combines solar shading and energy storage. Focusing on both the existing and the new technologies. Analysis of glazing types have also been carried out as this is of the highest importance to the performance of the window.

WP7: Development of control system, devices and software
This WP has been responsible for the development of the wireless communication multi-sensor and actuator system, which will make this window 'one of a kind'. Some of the sub tasks have been to investigate and develop power harvesting / supply and enable coping mechanisms for adverse radio frequency propagation conditions.

WP8: Technology integration and assembly
In this work package all the work come together and the prototype window will be assembled with all the components from the other work packages. This also includes integration of market specific designs. The prototype and concept will be clearly defined in a number of drawings.

WP9: Validation and certification of the ventilated window system
The activities in the work packages have been to test the prototypes and Fraunhofer did that at their facilities. It was also tested to see if it could be certificated according to EU standards.

In the following the results from each work package will be presented.

WP2: Exploitation and dissemination

The objective of this work package was to:

- to identify, assess and, where appropriate, protect all the project results, including assist coordinator with administration and update of the consortium agreement (CA) accordingly;
- to develop an exploitation strategy which will become a firm business plan including routes to market for all project results;
- to identify opportunities for financing of post-project development work;
- to develop a dissemination plan that will enable widespread publication of the project results - after all protection activities have been concluded;
- to disseminate the project results internally between the partners through training workshop in accordance with the consortium agreement.

WP2 was concerned with exploitation and dissemination and related activities of the CLIMAWIN knowledge and products and all tasks are now complete with good results.

Firstly, website(s) for both public information and partner communication were set up and run for the timeline of the project (and beyond). The public website has helped with dissemination and received a substantial number of hits despite not being particularly well optimised for search engines.

One of perhaps the most important actions, the market analysis, was completed at an early stage and turned out to be an invaluable exercise. Surprisingly, it showed that the possible market for CLIMAWIN windows runs to nearly 600 000 dwellings plus 3 million square metres of commercial and institutional windows (i.e. 4 % of the overall window market) which at average sales prices indicates a possible market of up to EUR 3.6 billion, with Germany, France, United Kingdom, Italy and Spain being the most likely target audiences.

A plan for use and dissemination of the projects unique knowledge were completed and also yielded some interesting results. Specific exploitable results that emanated included the prototype products (the pre heating / self cooling heat recovery, adjustable valve and bypass inlet, control systems, power integration as well as the CLIMAWIN concept itself) the test results and an automated configuration tool.

Formal dissemination exercises included field installations of the technologies at the field test site of the Franhaufer Institute as well as a comprehensive range of knowledge transfer activities. These included the second website focused on the capabilities and availability of the window and some test results. Also scholarly and popular articles were published in research and trade publications as well as online and a number of conference lectures have been given. More publishing is expected in the next six months as RTD partners finalise their findings. Similarly, CLIMAWIN was presented at three significant trade shows across Europe during the project and this will continue and intensify in the future.

An application to the add-on demonstration activity (research for benefit of SMEs) programme has been successful and a wide set of in situ demonstrations will be installed under this process in the next two years project.

A business plan for commercial utilisation of the project results has also been completed in this work package and a plan for market exploitation of CLIMAWIN based on the creation of a new company, has been agreed by all SME partners. The idea is that CLIMAWIN will be sold in two ways; as full ventilation windows sets and later, when the concept, is fully established in the market as s set of components sold along with a specification service to a wide range of window companies. Sales are expected to reach EUR 2 million in two years and rise to EUR 10 million by year 6 or 8.

WP3: Functional requirements, envelope definition and calculation

The objectives of this work package was to use market benchmarking to define product features required by user and regulation - including expected operating life time and servicing intervals. Secondly, from technical searches and industrial data to create definitions of functional requirements for the CLIMAWIN. This included requirements to:

a. operating envelope of the window designs including installation factors;
b. ventilation mechanism performance requirements and functionality;
c. solar shading / energy storage / night blind mechanism requirements and functionality;
d. electronic control system and communication requirements and functionality;
e. communication interface requirements for hybrid ventilation and smart building scenario;
f. design needs and product aesthetic appeal.

Finally, the objective was to quantify potential IAQ improvements and energy savings to the end user.

In the work package, the main product features required by a user and the market were identified. Further on this information was expanded with a set of technical requirements to the window, which are based upon functional principles of the window. Window functioning modes were identified as: heating mode (the air is supplied into the room by passing through the air gap) and cooling mode combined with a by-pass flow (the air into the room is supplied directly from the outside, meanwhile the air gap in the window is ventilated, but not connected with the room).

For meeting the requirements to the window in different countries, the information on building regulations in these countries was collected within the work package. Finally, the functional and technical requirements were set. These include:

- ventilation requirements that include requirements to the ventilation valve, to thermal and atmospheric comfort in the room, to air flow rates, to ventilation principle, etc.;
- solar shading / energy storage / night blind requirements;
- control requirements that include ventilation control, blind control, zone control, etc.;
- main control principles;
- requirements to the control system elements such as the type of actuators and their actuations cycle, energy harvesting and energy storing elements;
- control system, where the potential installation cost, potential for integration with home automation systems and system technology requirements were included.

Product design and manufacturing aspects were also evaluated and the requirements to window's visual appearance, installation and modulation requirements were stated. Finally, the preliminary program for testing and CE certification of prototype window was also developed.

WP4: System design and development

Interactions between and results of the four work packages (WPs 4-7) is gathered in this WP for the preliminary window design. The objectives of the work package was to:

- establish specification and sizing methodology for system components;
- produce window system design to meet IAQ, control and energy savings requirements detailed in WP3;
- establish installation and operational / maintenance methodologies;
- develop control strategy and optimisation algorithm;
- construct design methodology for complete installation designs;
- integrate hydraulic, electrical power supply and control requirements and develop applicability to advanced smart building scenarios;
- integrate aesthetic appeal and consumer preferences.

The work and results of the work package included development of a system design methodology. This work was combined of several methodologies. First of all, the calculation tool WIS was chosen for estimation window performance indexes, such as U-value and g-value. Critical and average weather conditions for window thermal and energy performance were described for any climate and finally the sizing methodology for window system components was developed and split into two separate sections: sizing of components:

(1) for indoor air quality; and
(2) for energy efficiency.

The latter one is based on energy balance calculations for various configuration of the glazing system in the window. Besides that a design methodology for installation design was developed, using two energy balance methods of different complexity level.

The design methodology explained above was applied for a pilot study of window glazing system configuration in the Danish climate and it was clearly seen that the chosen methodology is suitable for application in this project. Therefore, a CLIMAWIN design tool was developed to assist the SMEs in selecting the optimum designs for customers and to document their expected energy savings. Resources for the effort needed to develop a CLIMAWIN design tool, which were not planned from the beginning, came partly from WP6.

A window system design was developed to meet IAQ, control and energy savings requirements as specified in WP3. During this development phase, HORN and RUAH also established installation and operational / maintenance methodologies for the CLIMAWIN solution.

Control strategies for selection of operation mode of the windows, ventilation air flow and solar shading control was developed and has been implemented in the control system integrated in the CLIMAWIN prototypes. The window control system can be connected too / exchange information with a building management system if needed and it is possible to store control and performance data on web-databases for analysis and exchange with other systems. An app has also been developed for smart phone control of the window.

By the development of the two prototypes it has been proved possible to integrate a new ventilation system, a new wireless control system as well as PV energy production and battery storage in an attractive window design. And the test by Fraunhofer showed that the prototypes are well functioning and capable of controlling ventilation and solar shading according to the control strategies developed.

WP5: Development of ventilation system

The objectives of this work package were to develop the ventilation system and a new ventilation grill with low pressure losses through the grill, possibility to switch operation mode, possibility for control of inlet air flow, possibility for integration of the grill in the window frame.

Initially preliminary measurements of a prototype window ventilation grill were carried out. These measurements helped to evaluate the pressure losses for air passing through the air gap and the ventilation grill of the window. They also highlighted the needed improvements in ventilation grill technical design and lead to different solutions for motorised grill to be considered.

One of the first solutions for motorised grill was a tube with slots, which is rotating inside a tubular chassis. However, this solution was after some time abandoned because of a high risk of a 'rotating tube' solution to breach an already existing patent.

Therefore the development has to begin from scratch and a second concept model of modular ventilation units developed based on hinged flaps lifted by cams on a common axis. A heating / cooling and a bypass unit was modelled in 3D and produced in a rapid prototyping process (RPT). The material was an epoxy / acrylic resin that is cured to a hard semi-transparent state. Metallic bearings and axles were built in and flap edge sealing strips were added, so the prototypes could demonstrate the working principle reliably. To drive the flap movement through the ventilation states (closed, pre-heating, self-cooling and bypass) a common axle must rotate approximately 100 degrees. For this purpose, a drive unit to sit in line with the ventilation units was also designed, constructed in 3D and modelled by RPT. The RPT drive module was furnished with bearings, axles, racks, gears, and a miniature DC motor and prepared for inclusion of a small PCB decoding the current flap orientation (courtesy of University of Minho). All three units were built in 1:1 size to fit pre-cut slots in one RAUH and one HORN window prototype. The modules were assembled and mounted in the windows on site to test the viability of the concept. The drive unit was integrated with the decoder PCB and a motor driver PCB to form a fully functional flap driver. Whereas most aspects of the ventilation system were found to function well, issues appeared during the assembly of prototypes. Unit-to-window sealing, flap sealing, resistance to wind load, ease of unit interconnection, material selection and general assembly and mounting needed optimisation and further attention.

Based on the experiences obtained from the first prototype a large number of changes were made to the ventilation and drive unit 3D models. It was decided to produce the final prototypes in a more durable material, as the RPT models are prone to warping and cracking and not stable at extreme temperatures. All components were redesigned for four-axis milling in POM block material (Polyacetal / Delrin). The units were updated for a hexagonal axle, flaps weighed down by steel strips, flap and unit sealing with short mohair fabric and thin PE foil. Also the units were designed to snap together instead of screwing. A total of eight heating / cooling units, four bypass units and two complete drive units were milled, assembled and forwarded to HORN, RAUH and University of Minho for inclusion in test installations. 2D dimensioned drawings and complete 3D models were also handed over to the relevant SMEs.

Two different sensor housings were also developed for mounting sensors in the wooden frame (developed in 3D and submitted for milling in POM and Polycarbonate). A non-return valve based on a hinged counterbalanced flap, for installation in the bottom part of the window was modelled in 3D CAD. Several complete sets of fully working ventilation units have been designed, constructed and produced. Auxiliary items such as non-return valve and thermal actuator drive principle has been designed and documented in 2D and 3D drawings.

WP6: Energy optimisation and solar shade / night blind

The objective of this work package is to develop a combined solar shading and night blind and to develop energy optimised solutions for the intelligent dynamic window system. The development goals are a U-value of the window frame of U = 0,8 W/m2 oC, an average night time U-value of the glazing of U = 0,2 W/m2 oC and a solar shading factor of 0,2.

A prototype of a night blind with phase change material was developed as a combined night blind, venetian blinds and phase changing material (PCM) in one product. The PCM was attached to the blind surface on one side, meanwhile the other side of the blind stayed highly reflective. Depending on a season and thermal conditions indoors the blinds can be rotated towards the sun with PCM-side or reflective-side, in order to absorb / reflect solar radiation during the day and to release the heat from PCM towards indoors / outdoors during night.

The performance of this PCM-solution was tested experimentally in the AAU laboratory together with other types of shading devices and with the night blind configuration integrated in a double window with forced ventilated air gap. The fenestration system was placed in a guarded hot box modified to integrate an artificial sun and reproducing conditions of a cold winter night or day with clear sky. The air and surfaces temperatures were measured in several places of the system. Thermal performance of each shading devices and night blinds configurations were then evaluated through heat recovery, inlet air temperature, transmittance heat losses, ventilation heat losses and modified total U-value integrating transmittance and ventilation heat losses.

Six different configurations of the double window have been tested under the same controlled conditions:

- window without shading device and without ventilation of the air gap;
- window without shading device and with ventilation of the air gap;
- window with normal shading device in opened position and ventilation of the air gap. The normal shading device is composed of 95 thin grey aluminium blinds (15 mm x 1100 mm x 0,2 mm). The device is fully deployed and covers the entire glazing surface of the window. The blinds are in fully opened position (horizontal).
- window with insulated night blind in closed position and ventilation of the air gap. The insulated night blind is composed of 110 little hexagonal opaque cells (10 mm x 1100 mm x 14 mm). The curtain is fully deployed to cover the whole glazing surface and block entirely the solar radiations. Each cells are covered with an inside silver coating to decrease the thermal losses by radiation.
- window with PCM blind in opened position and ventilation of the air gap. The shading device is composed of 34 aluminium blades (40 mm x 1125 mm x 7mm). Each blade is filled with phase change material and painted black on one side to get a maximum absorptivity of solar radiations when they are facing the outside and therefore store thermal energy. The blind contain a total of 5391 kg of ethylene based polymer / paraffin wax (Energain DuPont) with a phase transition at 21,7 °C and a total heat storage capacity of 140 kJ/kg.
- window with PCM blind in closed position and ventilation of the air gap. The aluminium reflective surface of the blades is facing the outside and the black side with PCM is facing the inside. When there is no solar radiation anymore, the PCM releases the thermal energy stored during the day into the ventilated air gap and increases the thermal inertia of the entire window.

The experimental study proved the advantage of a ventilated double window used as a passive air preheating system to reduce the heating needs of a building due to ventilation. However, the results also showed that the additional benefits of utilising PCM night blind was far too small to compensate for the extra cost involved and the drawbacks experienced. The results showed that it is an advantage to include a blind / shading device in the cavity as it increases the transfer of heat to the cold air, but a normal aluminium venetian blind or an insulating blind performed almost at the same level as the 'PCM blind'.

In conclusion, the objectives of this work packages related to pane configuration and window frame design has been met. The objectives related to the use of PCM night blind have not been met. There are two main reasons for not achieving the critical objectives. The experiments showed that there was a large temperature gradient in the air gap with low air temperatures in the bottom, which prevented the phase change, and made it impossible to get the full benefit of the material. Secondly, if the amount of PCM should have been increased the weight of the PCM material and the blind becomes too high, the blind will restrict the view too much and the size of the closed blind will also be too large. The weight is very important as the requirement on self-production of energy by PV sets tight restrictions on the power of the motor and the energy use for activating the blinds. It was therefore concluded that the benefits were too small compared to the drawbacks of implementing the solution.

On the other hand, the experiments showed that with a traditional venetian blind many of the benefits regarding preheating of air and improved insulation could be achieved although not to the extent expected in the project proposal.

WP7: Development of control system, devices and software

The main objective of this work package was to develop a wireless communications multi-sensor and actuator system, based on a single or multiple device architecture, that can measure temperature, humidity, luminance, CO2 and other relevant elements, both indoor and outdoor, with very low power consumption. Secondly the objective is to enable the system to drive actuators for solar shading, night blind and ventilation system, according to a set of algorithms in order to assure maximum comfort and excellent power management in the context of a self-powering solution and energy efficient fenestration system. The work package should also investigate and develop power harvesting / supply and software for devices and monitoring of the fenestration system.

The achievements in the work package include:

- creation of data logging software tools to analyse the measurements and decisions taken by the window controller to adjust the ventilation valve and the blind;
- development of a zone controller with CO2 measurement capability and integration with the communication system;
- optimisation and improvements in the system functionality and reliability;
- development of a battery charging system to allow the usage of weaker USB cell phone chargers;
- battery capacity and voltage increased to allow more durability and the operation of more powerful blinds;
- integration of the designed ventilation valve using a digital encoder;
- development and optimisation of the solar charger circuitry;
- development and construction of the final control system prototypes to install in both RAUH and HORN prototype windows;
- successful integration of the electronics in the prototype windows.

WP8: Technology integration and assembly

The objective of this work package is to integrate the developed technologies from the R&D work package in a specific CLIMAWIN window design and to construct the prototype window to be used for the final functional and performance test.

Following the design, construction and manufacture of modular ventilation units, all components were installed in RAUH and HORN window prototype. The windows furnished with ventilation units and control systems were subjected to Fraunhofer test regimens and/or installed at real life test locations.

When developing the drive unit, integration of an orientation decoder PCB was crucial. Decisions regarding the decoding principle and PCB position were made and the drive unit geometry adjusted accordingly. The drive unit and the decoder PCB were assembled and the functionality was demonstrated successfully.

Ventilation units were successfully installed in test windows and the two window manufacturing SMEs has developed their existing windows and designed a new.

Drive unit was successfully designed and produced for integration with the UM decoding PCB. HO has designed a new ventilation window, where all the technical parts are placed in the sash. It was decided to produce the window using glass sample No. 1 with the double pane outside. RAUH has redesigned their Tri-star window to be a Ventilation window. Censors were placed in the construction and connected to the control.

Both at AAU and Fraunhofer, the windows were tested in rigs build into test facilities.

WP9: Validation and certification of the ventilated window system

The objectives of this work packages was to validate and certify the ventilated window system according to EU - standards and new test methods. This includes baseline analysis and demonstration of the functionality of the window system focused on energetic, indoor climate and acoustic aspects as well as validation and certification of the window system according to EU-standards.

The existing test standards for windows according to the product standard EN 1435-1where checked and when necessary adapted to the ventilated window.

Pretesting at a ventilated window with a natural ventilation system has been carried out to get the U-Value in dependence of ventilation properties on two early prototypes of the two window manufacturers of the project in dependence of natural ventilation. The U-Values of two final prototypes of ventilated windows have been measured according to the developed test procedure.

The window properties for ventilation, heat transfer, total energy transport and acoustic tests have been determined. Test reports for these single tests have been compiled for the window manufacturer for the CE certification and marking of their windows.

Tests to demonstrate the performance of the whole window system with preheating of air in the air gap through electronically controlled ventilation valves have been carried out with an installed window at a test house under natural summer conditions. During the testing, the CO2 control strategy was checked as well.

The second final prototype was tested in a double climate chamber under various climate conditions (summer and winter), with and without sun simulation to simulate and test functionality of the whole system.

Besides that transient building simulations have been executed to calculate and simulate the energy balance of a whole house with installed 'CLIMAWIN windows' compared to a German reference house.

The risks using the electronic components as well as the mechanical elements of the windows were assessed and verified. The risk of condensation and moisture problems were tested in the climate chamber.

A TRNSYS/TRNFLOW-model of the ventilated window under the in-situ test environment has been developed and validated with the help of the measurement data. This concept allows detailed computer simulation of the thermal behaviour of the system for different transient climate conditions. The calculations performed shows that the energy demand for heating the supply air of the ventilation system in winter can be reduced by up to about 30 % for German weather conditions with the preheating system of the 'CLIMAWIN-window'. That means that with the chosen boundary conditions the heating demand of a house with CLIMAWIN-windows can be reduced compared with a German Reference House by approximately 10 % for German weather data and approx. 16 % for Danish standard weather data.

The functionality tests in the climate chamber show that the ventilation valves of the window work very well under different climate conditions. Few parts of the control strategy have to be adapted to hot summer conditions. In addition the temperature and humidity outputs of the integrated sensors in the window frame have to be improved. The acoustic measurement results show that the acoustic performance can even reach values up to Rw = 40 dB in closed position of the ventilation system.

Potential impact:

CLIMAWIN will change the construction industry in Europe so that it evolves from a position where each building component (window, wall vent, extract system, power system, BMS) does a different function to one where a single more complex component like this advanced ventilation window will serve many functions (heat recovery, ventilation, day lighting, power production, glare control and automation) simultaneously.

Similarly, it will be a game changer in that it shows that renewable power sources integrated into the component can, with careful attention to capacity, recharge ability etc., can be used to power the moving function of a window, and by extension of other components that would benefit from being more plug and play. This is ideal for non-invasive window replacement only retrofit programmes (i.e. where only a single component is being replaced and the need for hardwiring etc. must be avoided) and usefully comes at when the European construction industry is undertaking a vast switchover from being based on new-build to one where retrofit is the majority activity for the next generation.

Building envelope components that now operate in parallel; (low tech trickle and through the wall vents, high spec glazing and cladding systems, extraction ventilation, and room comfort controls) will become integrated or at least allied.

Within the research community the evolving concept of windows being energy recovery / dynamic devices and the consequent need to adjust how U vales are understood (from the current of a static, steady state proposition to a dynamic time based net yield model) studied and tested will become a necessity. New norms and standard will have to be created and verified. This will find its way into facade and cladding systems also.

Contact details

Project coordinator

Professor Per Heiselberg
Aalborg University
Department of Civil Engineering
Sohngårdsholmsvej 57,
9000 Aalborg, Denmark
Tel: +45-994-08541

Adm. Project Manager

Anne Bock
Aalborg University - Fundraising and Project Management Office
Niels Jernes Vej 10
9220 Aalborg E, Denmark
Tel: +45-994-07584

Leading SME

Poul Horn
HORN Vinduer
Sortebjergvej 2
6640 Lunderskov, Denmark
Tel: +45-755-85087

Dissemination and exploitation leader:

Mr Brian O'Brian
Solearth Ecological Architecture
93 Meath Street
Dublin 8, Ireland
Tel: +35-316-165712

Project webpage: