Performance of ventilation in Estonian apartment buildings

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11th June 2017, 2017, Trondheim, Trondheim, Norway Norway 11th Nordic Nordic Symposium Symposium on on Building Building Physics, Physics, NSB2017, NSB2017, 11-14 11-14 June

Performance of ventilation in Estonian apartment buildings The 15th International Symposium on District Heating and Cooling a Alo Mikola Mikolaaa*, *, Targo Targo Kalamees Kalameesaa,, Teet-Andrus Teet-Andrus Kõiv Alo Kõiva

Assessing the feasibility of using the heat demand-outdoor temperature function for a long-term district heat demand forecast a aDepartment

Department of of Civil Civil Engineering Engineering and and Architecture, Architecture, Tallinn Tallinn University University of of Technology, Technology, Ehitajate Ehitajate tee tee 5, 5, 19086 19086 Tallinn, Tallinn, Estonia Estonia

Abstract Abstract

I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc

a

Center Innovation, Technology and Policy Instituto Superior Técnico, Av. Rovisco 1, 1049-001 Lisbon, systems Portugal is In study, the of ventilation and airResearch change -in Estonian apartment buildings withPais different ventilation In this thisIN+ study, theforperformance performance b of ventilation and air change in Estonian apartment buildings with different ventilation systems is Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France ventilation were under analysed by field measurements. 189 apartments from 107 buildings with natural and mechanical analysed by cfield measurements. 189 apartments from 107 buildings with natural and mechanical ventilation were under Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France investigation. Département Airflow and andSystèmes CO22 levels measured in the investigation. Airflow CO levels were were measured in the heating heating period period and and summer summer period. period. The The airflows airflows in in apartments apartments were were estimated estimated using using the the metabolic metabolic CO CO22 method. method. Measurements Measurements were were carried carried out out in in the the kitchen, kitchen, toilet toilet and and bathroom. bathroom. -1 and average airflow per surface The The analyse analyse shows shows that that the the average average air air change change rate rate of of concrete concrete and and brick brick buildings buildings was was 0.24 0.24 hh-1 and average airflow per surface 22). The total exhaust airflow corresponded to the target values of indoor climate category II in area of the apartment was 0.17 l/(s∙m area of the apartment was 0.17 l/(s∙m ). The total exhaust airflow corresponded to the target values of indoor climate category II in Abstract none of of the the apartments, apartments, and in only % of of the the apartments apartments did did it it correspond correspond to to climate climate category category III. III. The The average average air air change change rate none and in only 55 % rate of of -1,, and and average average airflow airflow per per surface surface area area of of the the apartment was 0.3 0.3 l/(s*m l/(s*m22). ). the newly newly built built (>2000) (>2000) apartment apartment buildings buildings was was 0.42 0.42 hh-1 the apartment was District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the In 77 % new apartments, total exhaust airflow corresponded with the target values of indoor climate category II and in 23 %, Ingreenhouse % of of the the gas newemissions apartments, total exhaust airflow corresponded with the target values of indoor climate category II and in 23 %, from the building sector. These systems require high investments which are returned through the heat of climate category III. ofsales. climate category Due to the III. changed climate conditions and building renovation policies, heat demand in the future could decrease, The technical inspection of ventilation The technicalthe inspection of studied studied ventilation systems systems shows shows that that natural natural ventilation ventilation systems systems are are in in poor poor condition. condition. Main Main problems problems prolonging investment return period. have to do with insufficient installation quality of channels and exhaust devices and lack of compensation airflow from air building have to do with insufficient installation quality of channels and exhaust devices and lack of compensation airflow from The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for air heatbuilding demand leakages. The main reason for of the exhaust air is to the low air in leakages. reason for the the reduction reduction exhaust air flows flows was is related related low supply supply air temperatures temperatures in cold cold period. period. forecast. The Themain district of Alvalade, locatedofinthe Lisbon (Portugal), used to as the a case study. The district is consisted of 665 Finally, the principles for the of ventilation systems provide better climate and energy performance, are also Finally, the that principles the renovation renovation ventilation systems to toThree provide better indoor indoor climate energyhigh) performance, also buildings vary inforboth constructionofperiod and typology. weather scenarios (low,and medium, and threearedistrict discussed. discussed. renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. © compared with results from a dynamic heatLtd. demand model, previously developed and validated by the authors. © 2017 The Authors. Published by Elsevier Peer-review under responsibility of the organizing committee of the 11th Nordic Symposium on Building Physics. Peer-review under responsibility of the organizing committee of the the 11th 11th Nordicof Symposium onbeBuilding Building Physics. The results under showed that when only weather change is considered, the margin error couldon acceptable for some applications Peer-review responsibility of the organizing committee of Nordic Symposium Physics. (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation Keywords: Performance Performance of indoor air CO CO22 concentration; natural ventilation, metabolic CO method Keywords: of ventilation; ventilation; indoor air concentration; CO22 method scenarios, the error value increased up to 59.5% (dependingnatural on theventilation, weather metabolic and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and 1. Introduction 1.renovation Introduction scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and The ventilation improve the accuracy of of the heatresidential demand estimations. The performance performance of the residential ventilation systems systems plays plays major major role role in in healthy healthy indoor indoor air air quality quality because because most most

people part of multidisciplinary people spend spend aa significant significant part of their their lives lives at at home. home. Based Based on on the the review review of of scientific scientific papers, papers, aa multidisciplinary group of European scientists have agreed that ventilation is strongly associated with comfort, productivity © 2017 The Authors. Published by Elsevier Ltd. group of European scientists have agreed that ventilation is strongly associated with comfort, productivity and and health health Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating andhealth [1–3]. Considering the importance of ventilation rate as an influencing factor for the quality of indoor air and [1–3]. Considering the importance of ventilation rate as an influencing factor for the quality of indoor air and health Cooling. that outcomes outcomes that may may be be influenced influenced by by indoor indoor environmental environmental quality, quality, more more studies studies would would be be valuable valuable [4]. [4]. Keywords: Heat demand; Forecast; Climate change 1876-6102 1876-6102 © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. Peer-review under under responsibility responsibility of of the the organizing organizing committee committee of of the the 11th 11th Nordic Nordic Symposium Symposium on on Building Building Physics. Physics. Peer-review 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.2017.09.681

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Previous cross-sectional national studies have shown that a significant proportion of dwellings are mainly with low ventilation rates [5–8]. Measurements of ventilation in dwellings exhibit random variations because of the differences in the building technologies, air tightness, occupancy, human behaviour, maintenance, weather, artistry and material ageing. As the topic is multidisciplinary, using probability-based design will give a guide to reliable alternatives and the associated economic analysis. For that purposes, stochastic data is also needed for the performance of ventilation. As the real performance ventilation influences comfort, health and energy use in buildings, the topic is important for the public health and national energy saving purposes. In this paper, the actual performance ventilation in Estonian apartment buildings is presented based on field measurements in different types of buildings with different ventilation principles. Since many of the similar apartment buildings in Eastern and Northern Europe have been built using similar technologies as in Estonia, it is possible to draw conclusions of the entire region. 2. Methods The cross-sectional study about the performance of ventilation was carried out in 189 apartments in 107 different types of apartment buildings. Wooden apartment buildings (45 apartments) built <1940 and concrete apartment and brick buildings built between 1955 and 1990 (83 apartments), had natural passive ventilation. Different structures apartment buildings built after 2000 (39 apartments) had mechanical ventilation. From each building, one to three apartments were selected for the indoor climate study. Typically an apartment was selected from one of the upper floors and the ground floor. Apartments consisted of one, two or three rooms, with a separate kitchen, entry, and sanitary rooms. Exhaust airflows were measured with an anemometer. Indoor air CO2 concentrations were measured with HOBO U12-013 together with TelAire 7001 CO2 loggers. Air change rate in bedrooms was determined based on measurement of the dynamics and level of CO2 produced by the occupants at 10 min. intervals during 2-3 week periods during winter and summer. Based on measurements of indoor CO 2 levels in bedrooms, the air change in bedrooms was estimated according to mass balance equation: Q

C(t )  Cex 

E  t E  (C(0)  C(ex)  )e V Q Q

(1)

where: V - effective volume of enclosure (m3); C - concentration of tracer gas (g/m3); Cex - outdoor concentration of tracer gas (g/m3); Q - internal/external exchange rate (m3/h); t - time (s); E - tracer gas generation (g/h); C(0) - tracer gas concentration at start of decay (g/m3); C(t) - tracer gas concentration at time "t" after start of decay (g/m3). As the CO2 emission varies on a wide scale in daytime, the night period when people are sleeping should be used in air change rate calculations. CO2 emission of adults is taken 13 l/h and the emission of children up to 12 years 6.5 l/h. For assessment criteria we use EN-15251 [9] indoor climate category (ICC) III (acceptable, moderate level of expectation, for old buildings) for old (<1990) buildings and ICC II (normal level of expectation, for new buildings and major renovations) for new (>2000) buildings. The measurement results of CO 2 level are brought out for occupancy time only. The average human presence in apartments during the heating period was 68 % and 55 % in summer period. The air leakage rate of building fabric was measured with the standardised fan pressurisation method [10]. Old wooden apartment buildings were leakier (q50 = 10 m3/(h∙m2); n50 = 13 h-1) than old concrete and brick buildings (q50 = 4.1 m3/(h∙m2); n50 = 5.8 h-1). The new apartments were the most airtight (q50 = 1.7 m3/(h∙m2); n50 = 2.3 h-1). 3. Results 3.1. Indoor CO2 levels and air change rates in apartments The average indoor air CO2 level in Estonian apartments during the occupancy time in the heating period was 1102 ppm and 913 ppm in summer period. In the case of concrete and brick apartment buildings, the average level during



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occupancy period was 1265 ppm. The average CO2 concentration in apartments with natural passive stack ventilation (<1990) was 1225 ppm, and in apartments with mechanical ventilation (>2000) it was 788 ppm, see Fig. 1. During the occupied time in the heating period, the CO2 concentration indoors in old apartments with natural ventilation corresponded to ICC III class 65 % of the cases and in new apartments with mechanical ventilation corresponded to ICC II class 67 % of the cases. During the occupied time in summer period, the CO2 concentration indoors in old apartments with natural ventilation corresponded to ICC III class 79 % of the cases and in new apartments with mechanical ventilation corresponded to ICC II class 67 % of the cases.

Fig. 1. CO2 concentration in apartments during the occupied heating period.

3.2. Airflows in bedrooms The airflow in bedrooms was calculated using the metabolic CO2 concentration by Formula 1, as the average value of seven day periods. The average airflow of panel and brick buildings with natural ventilation was 4.4 l/s (2.9 l/s per person) during the heating period and 6.2 l/s (5.2 l/s per person) in the summer period. The same airflows in wooden buildings with natural ventilation but leakier building envelope were 6.6 l/s (3.7 l/s per person) during the heating period and 7.8 l/s (3.9 l/s per person) in the summer period. In new apartment buildings with mechanical ventilation, the average airflow was 10.7 l/s (7.1 l/s per person) during the heating period and 12.4 l/s (6.0 l/s per person) in the summer period. According to EN 15251 [9] criteria to airflow in bedrooms, 22 % apartments in the old panel and brick buildings with natural ventilation corresponded to ICC III during heating and 44 % during the summer period. In old wooden apartment buildings with natural ventilation the correspondence to ICC III criteria was 37 % during the heating period and 47 % during the summer period. In new apartment buildings with mechanical ventilation correspondence to ICC II criteria was 35 % during the heating period and 31 % during the summer period. The average air change rate according to the metabolic CO2 method is 0.51 h-1 both in summer and winter session in the old panel and brick buildings. In wooden buildings, the air change rate is 0.56 h-1 in the heating period and 0.79 h-1 in summer period. In new apartment buildings with mechanical ventilation the air change rate is 1.1 h-1 in the heating period and 1.4 h-1 in summer. The airflows in bedrooms per person are shown in Fig. 2. It can be concluded that in all three types of buildings the air change in summer period is higher. The main reason for that trend is the possibility to open the windows without compromising on thermal comfort.

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a

b

Fig. 2. (a) Airflow in bedrooms calculated according to metabolic CO2 method during the heating period; (b) Airflow in bedrooms calculated according to metabolic CO2 method during the summer period.

3.3. Exhaust airflows from kitchen, bathrooms and toilets. Exhaust airflows were measured in kitchen, bathrooms and toilets, see Fig. 3. In concrete and brick apartment buildings with natural ventilation, the average exhaust airflow (momentary, during measurement in heating period) was 9.1 l/s, the average total air change rate of apartments was 0.24 h-1, and airflow per floor area of the apartment was 0.17 l/(s∙m2). In only 5 % of the apartments, total exhaust airflow corresponded to the target values of ICC III. In new apartment buildings with natural ventilation, the average exhaust airflow was 18 l/s, the average total air change rate of apartments was 0.42 h-1, and airflow per floor area of the apartment was 0.30 l/(s∙m2). In only 7 % of the apartments, total exhaust airflow corresponded to the target values of ICC II.

a

b

c

d

Fig. 3. (a) Exhaust airflows from old apartments with natural ventilation; (b) Exhaust airflows from new apartments with mechanical ventilation; (c) Total air change rate in apartments per floor area; (d) Total air change rate in apartments per internal volume.



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3.4. Principles for renovation of ventilation in old apartment buildings The main task of the renovation of a ventilation system is to ensure indoor air quality. Regardless of the type of the ventilation system, all rooms of the apartment must have continuous and adequate ventilation airflow. Thereby, fresh air inlets must not cause inconvenience by way of drafts and cooling. The current study showed that natural passive stack ventilation does not provide enough airflow in apartments and does not enable heat recovery. The main problems are related to insufficient installation quality of channels and exhaust devices and a lack of compensation airflow from air building leakages. Measurements in apartments with room based air handling units with regenerative ceramic heat exchangers have shown similar insufficient results because they fail to guarantee a continuous air change in apartments and do not comply with the energy efficiency requirements [11]. Based on current knowledge three main types of ventilation are most suitable for Estonian cold climate [12,13]:  Apartment based supply and exhaust ventilation system with heat recovery, with unit located in apartment, in corridor or staircase.  Centralized supply and exhaust ventilation system with heat recovery, with unit located on roof, pipes located in external wall or in apartment.  Centralized exhaust ventilation system with fresh air radiators, heat pump heat recovery; each apartment has a single exhaust shaft, ventilation unit on the roof, or all apartments have joint exhaust shaft, ventilation unit on the roof. 4. Discussion As ventilation airflows were below standard criteria, and the CO2 level was over criteria, there is something wrong with the current design and installation practice of ventilation. One of the main reasons could be that designers design ventilation airflow, not the real performance. Usually, the side defects, like too noisy ventilation, draft and high energy use prevent using ventilation in design level. Better design, installation and maintenance guidelines are needed to avoid presented errors in the performance of ventilation in future. Mechanical ventilation ensures statistically significantly lower indoor air CO2 level than natural ventilation in old panel and brick or wooden buildings. Natural ventilation does not guarantee sufficient air change rate and thermal comfort. The analysis shows that the ventilation systems of studied panel and brick and wooden buildings need renovation. At the same time, the installation of fresh air valves and retrofitting the other parts of old natural ventilation system does not guarantee the best possible indoor climate in apartment buildings. In dimensioning the natural exhaust ventilation systems, the calculated outdoor air temperature was taken to be +5 ºC. That is the reason why natural exhaust system does not guarantee the sufficient exhaust airflows from apartments even in theory. Another reason for the reduction of the compensation airflow is related to the renovation of building envelopes and replacements of old windows with tighter ones. Based on this study, we can see a trend that in the case of mechanical exhaust ventilation with the fresh air valves in the new buildings, the exhaust airflows are also reduced. Although the average exhaust airflow in new buildings is two times higher than in buildings with natural ventilation, then in many apartments the fans are maintained in minimal possible airflow. Due to the low-temperature airflow from fresh air valves, the airflow is decreased and the CO2 level increases in winter period. Thus, when renovating the natural ventilation systems in old apartment buildings or constructing new ventilation systems, the mechanical supply-exhaust system with effective heat recovery should be preferred, or the compensation air from the fresh air valves should be preheated in the case of mechanical exhaust ventilation with heat pump heat recovery. The best possible solution to raise the supply air temperature of mechanical exhaust ventilation is to use the fresh air radiators. Conclusions The performance of ventilation in Estonian apartment buildings is distressing. The main problems are connected with too low airflow and high pollutant level. Even in new apartment buildings with mechanical ventilation, where airflows are significantly higher, standard criteria are still not fulfilled. The average indoor air CO2 level of all the

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measurements during the occupancy time in the heating period was 1042 ppm, and the average level of occupancy period was 1102 ppm. The indoor air CO2 concentration of old apartments with natural ventilation in the heating period corresponded to ICC III class 65 % of the occupied time and in new apartments with mechanical ventilation corresponded to ICC II class 67 % of the occupied time. During the occupied time in summer period the CO2 concentration indoors in old apartments with natural ventilation corresponded to ICC III class 79 % and in new apartments with mechanical ventilation corresponded to ICC II class 67 %. During the heating period, the average airflow from bedrooms of panel and brick buildings with natural ventilation is 2.9 l/s per person. In wooden buildings with natural ventilation and in case of leakier building envelopes, it was 3.7 l/s per person. In new apartment buildings with mechanical ventilation it was 7.1 l/s per person. The average total air change rate of old apartments with natural ventilation was 0.24 h-1, and airflow per floor area of the apartment was 0.17 l/(s∙m2). The average air change rate of new buildings was 0.42 h-1, and average airflow per surface area of the apartment was 0.30 l/(s∙m2). For renovation of ventilation in old apartment buildings, we recommend quiet supply and exhaust ventilation with effective heat recovery. In addition to calculating required airflows, the better design of the real performance of ventilation system is also needed. Better design, installation, and maintenance guidelines are needed to avoid presented errors in the performance of ventilation in future. Acknowledgements The research has been conducted as a result of the “Nearly-zero energy solutions and their implementation on the deep renovation of buildings, IUT1−15“ (financed by Estonian Research Council). The study utilises the measuring data of the national research projects financed by Estonian Credit and Export Guarantee Fund, by the Ministry of Economic Affairs and Communications and Tallinn University of Technology. References [1] Bornehag CG, Sundell J, Hagerhed-Engman L, Sigsgaard T. Association between ventilation rates in 390 Swedish homes and allergic symptoms in children. Indoor Air 2005;15:275–80. doi:10.1111/j.1600-0668.2005.00372.x. [2] Wargocki P, Sundell J, Bischof W, Brundrett G, Fanger PO, Gyntelberg F, et al. Ventilation and health in non-industrial indoor environments: report from a European Multidisciplinary Scientific Consensus Meeting (EUROVEN). Indoor Air 2002;12:113–28. doi:10.1034/j.1600-0668.2002.01145.x. [3] Hägerhed-Engman L, Sigsgaard T, Samuelson I, Sundell J, Janson S, Bornehag CG. Low home ventilation rate in combination with moldy odor from the building structure increase the risk for allergic symptoms in children. 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