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11th Nordic Symposium on Building Physics, NSB2017, 11-14 June 2017, Trondheim, Norway
A simple adaptive ventilation controller for mediaeval church The 15th International Symposium on District Heating and Cooling
Veljo Siniveea*, Lembit Kurika, Targo Kalameesb
AssessingTallinn theUniversity feasibility of using the heat demand-outdoor of Technology, Faculty of Science, Ehitajate tee 5, 19086, Estonia Tallinn University of Technology, Chair of Building Physics and Energy Efficiency, Ehitajate tee 5, 19086, Estonia temperature function for a long-term district heat demand forecast a
b
Abstract a
I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
Recherchein&national Innovation, 291 Avenue Dreyfous Daniel, Limay, France communities operating One of the biggest problemsbVeolia encountered heritage objects is excess of 78520 moisture. Religious c Systèmes Énergétiques et Environnement - IMT Atlantique, 4 ruefrom Alfredour Kastler, 44300 Nantes, Francethat in most churches oftenDépartement lack financial resources to fight this problem. Analyzing climate data measurements we show cases positive effect is achieved by passive ventilation – opening and closing windows/doors in proper situations. Unfortunately many churches are actively used only during short periods of time. A low-power ventilation controller wirelessly operating electrical window actuators was designed. Firmware of the device includes setting lowest outside temperature and active Abstract time zone for operating electrical windows etc. Designed device is affordable for small parishes.
District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the © 2017 The Authors. Published by Elsevier Ltd. greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat Peer-review under responsibility of the organizing committee of the 11th Nordic Symposium on Building Physics. sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. Keywords: Indoor climate; Churches; Adaptive ventilation; Controller, Window actuators. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district 1. Problems of unheated mediaeval stone churches in Estonia renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. Most Estonian rural areas change are closed in winterthe time. In unheated churches, one of the most applications dominant The results showedchurches that wheninonly weather is considered, margin of error could be acceptable for some problems very demand high relative humidity throughout the year, creating a high risk for mold and algae growth [1]. (the error was in annual was lower than 20% for all weather scenarios considered). However, after introducing renovation Communities small andupthetorooms the reverends areand satisfactory holdingcombination a divine liturgy every scenarios, the are errorusually value increased 59.5% of (depending on thehouse weather renovationfor scenarios considered). Sunday when it is cold outside.increased Since majority of these big historical value, they are to kept The value of slope coefficient on average withinchurches the rangehave of 3.8% up to 8% and per heritage decade, that corresponds the decrease intothethe number of during heating hours of 22-139h during the heatingChurches season (depending on theAn combination of weather accessible public summer time (The Wayfarers’ project etc). opened main door and is renovation to scenarios Onimportant the other hand, function intercept increased for 7.8-12.7% per decade the considered be the considered). first and most sign of an open church. Unfortunately this practice may(depending not be theon best coupled scenarios). values suggested could be used to modify the function parameters for the scenarios considered, and for the health of the The building. improve the accuracy of heat demand estimations. A typical situation that takes place especially in case of weather getting warmer is that outdoor air contains more
water vapor than indoor air. Open doors let outdoor humidity in, causing an overload of moisture in the building. In © 2017 The Authors. Published by Elsevier Ltd.
* Corresponding author. Tel.: +372-620-3004; fax: +372-620-2020. Peer-review responsibility of the Scientific Committee of The 15th International Symposium on District Heating and E-mail address:under
[email protected]
Cooling.
Keywords: Heat demand; Forecast; Climate change
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of the 11th Nordic Symposium on Building Physics 10.1016/j.egypro.2017.09.674
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addition to very typical moisture sources in Estonian mediaeval churches – soaring moisture from soil, water caused by melting snow or rain that penetrates ceiling or walls. Such excess moisture condenses on the floors and walls of the churches creating good conditions for developing algae, bacteria and mould (Fig.1).
Fig.1. Condensed and hygroscopic water drops on the walls and pools on cold stones cause algae growth in a medieval church in Estonia.
Several strategies exist for fighting condensed water [2, 3]: traditional heating - keeping constant temperature, very expensive in big mediaeval churches conservation heating - keeping constant relative humidity, difficult/expensive at warm days dehumidification of the indoor air - cheaper than the two previous strategies adaptive ventilation - ventilating only when the inside absolute humidity (AH) is higher than outside, suitable in churches with internal sources of humidity [4, 5, 6]. Three first strategies need more or less financial resources that are not feasible for small parishes. Since many parishes are small and communities lack resources even for running existing apparatus, a low power device solving moisture problems is desired. The adaptive ventilation is a good choice. The enormous drying potential of adaptive ventilation is pointed out in a study conducted in Sweden [7].The adaptive ventilation needs some preparation works (tightening the building envelope, installing wires and ventilators), automatic opening/closing of big doors is difficult, permission from the heritage board is needed etc. The controlling of adaptive natural ventilation can be realized by simply manually opening or closing door(s) or window(s) provided that values of absolute humidity in- and outdoors are known. Procedure can be carried out by community members or guides with tourists etc being anyway present in the facility for some activity. Nevertheless in rural churches, community members or guides could not be in church in the needed time or they could not have the needed technical knowledge to operate the airing equipment. Therefore some control system is needed. 2. Adaptive ventilation controller The device for controlling airing in a church described in present paper consists of three main parts (Fig.2): sensor(s) with radio transmitters, radio controlled window actuator(s) a receiver unit capable of analyzing data received from sensors, displaying it, giving (human-readable) recommendations for suggested ventilation modes and controlling the actuator unit(s). The receiver also logs all gathered data to a SD-memory card if such is present. The unit implements a traffic lights display system where small LED lights indicate whether the room should be ventilated (green light on) or not (red light on). Ventilation modes were calculated using data from a transmitter located outside the building and of receivers integrated sensor. Absolute water vapour densities indoors and outdoors are calculated and then compared to each other. Comparison routine has a small user-configurable hysteresis (default value is 0.5 g/m3). If there is more water vapour outside a message is displayed suggesting closing door and/or windows in order to prevent the moisture coming
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in and vice versa. If the difference of humidity is less or equal to 0,5 g/m3 a yellow light is lit on the „traffic light“ display indicating that changing ventilation conditions is recommended but not yet mandatory. Corresponding radio commands are sent to window actuators if they are present. Number of transmitters is presently limited to a maximum of 7 separate nodes. During the tests of the system we used two sensors. It could be difficult to calculate absolute humidity values using readings of relative humidity meter. Therefore a device was designed which calculates ventilation recommendations (to open doors/windows or not) using data from in- and outside climate measurements. Ventilation hints were presented on an LCD display in form understandable to every member of the community (i.e. “suggest opening doors/windows for ventilation” etc). A traffic lights system implemented in the device makes recommended ventilation modes clearly visible from distance. Unfortunately this method does not solve the problem that many churches are actively used only during short periods of time. An improved ventilation controller adding capability to wirelessly operate electrical window actuators was designed. The firmware of the device includes many improvements like setting lowest outside temperature and active time zone for operating electrical windows. The designed controller is a low power device addressing possibilities of many religious communities. The system can be used without window actuators if community members follow ventilation suggestions displayed on main units screen.
Fig.2. Receiver with “traffic lights” indicator, transmitter and window actuator units of „Holy Receiver“ version 2.
2.1. Transmitter unit Temperature/humidity/pressure transmitters could be located anywhere in a monitored building. Typically the places with best conditions are not easily reachable (at the altitude of about 5 meters on northern window in Risti Church). This means that the circuit of the unit has to be optimized for low power consumption (long battery life) and little or no need for servicing. Most of the power is consumed by radio transmitter. There is no way to avoid transmitting data but keeping packets short and intervals of inactivity relatively long helps reducing the power needed (20 ms versus 10 minutes in present design). Radio transmitter is built around a Si4463 chip (by Silicon Labs) operating in a 433 MHz band. Temperature and humidity sensor is a SHT21 device manufactured by Sensirion. This chip returns to sleep after successful measurement cycle automatically and has satisfactory accuracy (about 0,3 °C for temperature and 2% for humidity). Measurement process takes about 30 ms. Air pressure sensor is a BMP180 (IC5) by Bosch. Main controller of the unit is a PIC18F26J50 device manufactured by Microchip featuring extremely low power consumption (Fig. 3). There is a reed switch for transmitter range test and another one that is used for controlling the state of a door or window. Door sensors state and battery voltage are transmitted together with climate data to the receiver unit.
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Fig.3. Circuit of the transmitter unit.
2.2. Receiver unit The main task of the receiver unit (see Fig. 4) is to collect and validate data sent by transmitter units. If system is configured to use radio-controlled actuators, corresponding commands are sent to them. Each actuator replies with its status, board temperature and some less important technical data that can be displayed on screen of the receiver via menu command. The concentration of water vapour is calculated from temperature and humidity readings using a formula [9] optimized in order to make calculations easier for the microcontroller. The receiver has its own temperature and humidity sensor (connected via JP2) for calculating water vapour density inside the building. It is possible to use some radio sensor for indoor climate calculations (via configuration menu). Such sensor could be placed next to some valuable exhibit i.e. an organ or altar painting. LCD screen shows data gathered from outdoor transmitter and internal sensor of the unit (or radio transmitter configured to function as an indoor climate sensor). Messages encouraging user to change ventilation modes are displayed using bigger font. Unit keeps an eye on every transmitter’s battery state and gives an early warning in case of battery failure. In order to conserve power and keep units case cool screen backlight is on full power only during navigation in menus or changes in the state of the SD-card. After 30 seconds of inactivity in user input system reduces backlight power about 90%. Data on display is still readable but power consumption is reduced to 7 mA. The unit has one general propose input and power transistor controlled output. Input could be used to monitor state of some door (in our case the main door of the church was monitored). Output was designed to activate a loud horn thus realising a simple burglar alarm. Alarm can be (de-)activated using a PIN code. The state of input and output is logged together with measurement data to a SD-card if such is inserted. All settings of the unit could be changed via simple menu system accessible only if user inputs a correct PIN-code. This safety feature proved to be useful operating in a public facility. In order to fully implement possibilities of described passive ventilation system up to 7 radio-controlled electric window actuators could be used. Actuator mechanism is controlled by a PIC18F47J13 microcontroller, radio link is built around a Si4463 transceiver chip. In case of actuator jam (freezing, strange objects blocking window movement) controller makes 3 retries before sending an alarm packet.
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Fig.4. Circuit of the receiver unit.
3. Testing in Harju-Risti church The device is under testing in Harju-Risti Church (Holy Cross Church) (Fig.5 left) located in North Estonia. Risti Church was built up of the local limestone by Cistercian monks of Padise Monastery on the 13th and 14th centuries. The main controller is placed on the western wall of the church and outdoor unit is taped to a windowpane of the northern window (Fig. 5 right). Air volume of the church is 2330 m3.
Fig.5. Holy Cross Church in Risti (left) and placements of sensor units in it (right).
The church is not heated and relative humidity is high [8]. It means that indoor temperature in winter period often drops below 0 °C and in spring church walls become colder than outdoor temperature resulting in excess moisture. It is possible to double the exchange of air of Harju-Risti Church by means of opening doors and/or windows. Air exchange rate (measured with tracer gas method [3]) is 0.61h -1 with opened doors and 0.26h-1 with closed doors [8]. If outdoor absolute humidity is +1 g/m3 greater than indoors, ventilation introduces 1.4 kg water per hour. If doors are closed, only 0.6 kg/h is introduced (church is not airtight!). Mean humidity of the indoor air of the church on annual basis is ~0.6 g/m3 greater than outdoors meaning that ventilation should be considered. Nevertheless in cases when water vapor density is greater outside, ventilation should be avoided. Moisture introduced by outdoor air does not distribute evenly in the building but rather tends to condensate on surface layers of walls providing good conditions for algae growth. Let us analyze indoor climate of the church using data from spring time (Fig.6, left). Absolute humidity (AH) of outdoor air is greater than AH inside during periods A, B, C and D. On moment A the main door is opened and indoors AH rises. On moment B the door is closed resulting in AH inside being practically constant. Period C shows that opening door even for a short time results in rapid growth of indoors AH. Same conditions do not apply to moment
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D. The reason is simple: calm weather outside results in zero air exchange providing no ventilation although the door is opened. Demonstrated patterns show that one can control indoors AH of Harju-Risti Church by simply opening and closing doors/windows. Experiment with CO2 yields same results (Fig.6, right). Air exchange rates calculated agree with the ones in literature source [8]. By manually opening or closing windows according to traffic light signals the system can be used without electric window actuators if needed. Traffic light system was warmly welcomed by users in Risti Church.
Fig.6. Influence of ventilation on indoor climate.
4. Conclusion The present paper demonstrates that it is possible to keep indoor climate of rural mediaeval churches under control using adaptive ventilation. A low-cost electronic device based on above described principles was designed, built and is being tested in Harju-Risti Church. Although the reverend claims that indoor climate has significantly improved after tests of the device started, it is difficult to prove it yet. A longer test period should clarify matters. The next step would be connecting the device to some central database. Acknowledgment This research was supported by the Estonian Research Council with Institutional research funding grant IUT1-15 and by the Estonian Centre of Excellence in Zero Energy and Resource Efficient Smart Buildings and Districts, ZEBE, grant TK146 funded by the European Regional Development Fund. Authors wish to thank the reverend of Harju-Risti Church Annika Laats for cooperation and great ideas. References [1] [2] [3] [4] [5] [6] [7] [8]
Kalamees, T.; Väli, A.; Kurik, L.; Napp, M.; Arumagi, E.; Kallavus, U. (2016). The influence of indoor climate control on risk for damages in naturally ventilated historic churches in cold climate. International Journal of Architectural Heritage: Conservation, Analysis, and Restoration, 10 (4), 486−498, 10.1080/15583058.2014.1003623. P. K. Larsen and T. Broström, “Climate control strategies for occasionally used churches: heat, dehumidify, ventilate – or do nothing,“ in Proc. Cultural heritage preservation: EWCHP- 2012, Norway, Norwegian Institute for Air Research , 2012, pp. 124-130. Napp, M.; Kalamees, T. (2015). Energy use and indoor climate of conservation heating, dehumidification and adaptive ventilation for the climate control of a mediaeval church in a cold climate. Energy and Buildings, 108, 61−71, 10.1016/j.enbuild.2015.08.013. Napp, M.; Wessberg, M.; Kalamees, T.; Broström, T. (2016). Adaptive ventilation for climate control in a medieval church in cold climate. International Journal of Ventilation, 15 (1), 1−14, 10.1080/14733315.2016.1173289. Broström, T., Hagentoft, C.-E., & Wessberg, M. (2011). Humidity control in historic buildings through adaptive ventilation: A case study. Proceedings of the 9th Nordic Symposium on Building Physics, Tampere. Hagentoft, C.-E., & Kalagasidis, A.S. (2010). Mold growth control in cold attics through adaptive ventilation: Validation by field measurements. In Buildings XI: Thermal performance of exterior envelopes of whole buildings (p. 8). Florida, USA Hagentoft C-E. and Kalagasidis A. S., “Drying potential of cold attic using natural and controlled ventilation in different Swedish climates “ in Proc 8th International Cold Climate HVAC 2015 Conference, Sweden, Chalmers University of Technology, 2015, vol. 146, pp. 2-7. Arumägi, E.; Kalamees, T. and Broström, T. “Indoor climate in a naturally ventilated unheated medieval church in Harju-Risti, Estonia,“ presented at the 10th REHVA World congress Clima 2010: Sustainable Energy Use in Buildings, Antalya, Turkey, May 9-12, 2010.
