Scholarly article on topic 'Thermal Comfort in a Romanian Passive House. Preliminary Results'

Thermal Comfort in a Romanian Passive House. Preliminary Results Academic research paper on "Economics and business"

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{"Thermal comfort" / "Passiv Haus" / "adaptive evaluation" / PMV / TSV}

Abstract of research paper on Economics and business, author of scientific article — Ioanaudrea, Cristiana Croitoru, Ilinca Nastase, Ruxandra Crutescu, Viorel Badescu

Abstract Thermal comfort is a very important aspect of building design and evaluation. Global current requirement is to reduce energy consumption which results in a preoccupation for low energy buildings. The challenge is to realize comfortable low energy buildings. Romanian climate (Köppen climate type D - temperate continental climate) in known for its cold winters and hot summers. The aim of this paper is to realize a thermal comfort study in a low energy building, an office building Passive House located in Romania, in summer period. For this purpose a field survey has been done in the summer of 2013, comfort parameters were measured inside the building and comfort questionnaires were distributed to the occupants. This paper compares the experimental results with the subjective response and analyzes the distribution of the thermal sensation votes on the building floors. Also, for two days of measurements, an adaptive thermal comfort evaluation is made, using thermal comfort standard EN 15251. Measurements data for one day placed the building in Category I of comfort (high level of expectation) and for the other day in Category II of comfort (normal level of expectation). Possible explanations are discussed in relation with thermal regime of the buildings.

Academic research paper on topic "Thermal Comfort in a Romanian Passive House. Preliminary Results"

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Energy Procedía 85 (2016) 575 - 583

Sustainable Solutions for Energy and Environment, EENVIRO - YRC 2015, 18-20 November

2015, Bucharest, Romania

Thermal comfort in a Romanian Passive House. Preliminary results

IoanaUdreaa*, Cristiana Croitorub, Ilinca Nastaseb, Ruxandra Crutescuc,

Viorel Badescua

aPolytechnic University of Bucharest, Faculty of Mechanical Engineering and Mechatronics, Thermodynamics Department, Spl. Independentei

313, 060042, Bucharest, Romania bTechnical University of Civil Engineering in Bucharest, Building Services Department, 66 Avenue Pache Protopopescu, 020396,

Bucharest, Romania

cSpiru Haret University, Faculty of Architecture, 13 Ion Ghica Str., District 3, 030045, Bucharest, Romania

Abstract

Thermal comfort is a very important aspect of building design and evaluation. Global current requirement is to reduce energy consumption which results in a preoccupation for low energy buildings. The challenge is to realize comfortable low energy buildings. Romanian climate (Koppen climate type D - temperate continental climate) in known for its cold winters and hot summers. The aim of this paper is to realize a thermal comfort study in a low energy building, an office building Passive House located in Romania, in summer period. For this purpose a field survey has been done in the summer of 2013, comfort parameters were measured inside the building and comfort questionnaires were distributed to the occupants. This paper compares the experimental results with the subjective response and analyzes the distribution of the thermal sensation votes on the building floors. Also, for two days of measurements, an adaptive thermal comfort evaluation is made, using thermal comfort standard EN 15251. Measurements data for one day placed the building in Category I of comfort (high level of expectation) and for the other day in Category II of comfort (normal level of expectation). Possible explanations are discussed in relation with thermal regime of the buildings.

©2016 The Authors. Publishedby Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee EENVIRO 2015 Keywords: Thermal comfort; Passiv Haus; adaptive evaluation; PMV; TSV

* Corresponding author. Tel.: +4-074-466-1303 E-mail address: udreaioana@yahoo.com

1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee EENVIRO 2015 doi:10.1016/j.egypro.2015.12.247

1. Introduction

The European Union Directive [1] has been set ambitious targets, such as reducing the energy consumption by 20% until 2020. This Directive, related to the energy performance of buildings, stipulates that by 2020 all new buildings constructed within the European Union should reach nearly zero energy levels. This means that the low energy buildings as Passive Houses need a special attention. The Passive House (Passivhaus) concept was developed in Germany in 1990s by the physicist Wolfgang Feist [2]. The Passivhaus concept was developed for the NorthWest Europe. It starts in Germany and rapidly spreading across Austria and Switzerland. In this country the houses built in the Passivhaus standard proved to be convenient and comfortable [3]. But in 2005, in Europeean project Passive-On [4], a study was undertaken in order to see the applicability of the Passivhaus concept in the East of Europe. There were some problems regarding to the risk of overheating in summer. The author Pfafferott [5] evaluated 12 low energy buildings located in Germany and the evaluation results show that the passively cooled low-energy office buildings provide a good thermal comfort (category I and II according to prEN 15251) in the moderate European summer climate. From the McLeod paper [6] it can find that recent years have seen a rapid movement in the adoption of the German Passivhaus standard as a template for ultra-low energy and zero carbon buildings in the UK. The authors analyzed the overheating risks in Passivhaus dwellings and show that optimization of a small number of design inputs can improve the problem. The study realized by Sameni [7] considers the overheating risk during the cooling season in 25 flats built to the Passivhaus standard over three cooling seasons in Coventry, UK. He found that the level of overheating varies in different flats and it is more related to the occupant's behaviour than to the construction. He found useful to evaluate the overheating risk using an alternative approach, the adaptive thermal comfort model. The results show that the overheating risk is lower for the normal occupants; but higher for the vulnerable occupants.

Human thermal comfort embraces two major approaches, classical model [8] and adaptive model [9]. Classical model, named Fanger model considers that human comfort depends on the quantitative, combined influence of six parameters (air temperature, mean radiant temperature, water vapour pressure, air velocity, closing level and metabolic rate). The adaptive model relates indoor design temperatures or acceptable temperature ranges to outdoor meteorological or climatologically parameters (mean outdoor effective air temperature, mean outdoor air temperature). Thermal comfort inside buildings is evaluated by several standards (ASHRAE 55, EN 15251, EN ISO 7730 [10-12]). Adaptive thermal comfort approach is accepted only in ASHRAE 55 and EN 15251 standards. It is applied only for natural ventilated buildings according to ASHRAE 55 standard and only for free running buildings according to EN 15251. Nicol and Humphreys explained in [13] what a free running building is. It is one in which no energy is being used either for heating or for cooling at the time of the survey. The use of fans to increase air movement does not exclude the building from the free-running mode. In the review paper of Carlucci [14] one can find a comparative description of the comfort categories for adaptive evaluations according to EN 15251 and ASHRAE 55.

From the study of the literature we found that the thermal comfort, especially the adaptive thermal comfort is scared studied in Romanian climate (Koppen climate type D [15] - temperate continental climate) for the buildings realised in the Passivhaus concept. This paper is proposes to realise a adaptive thermal comfort study in this situation, in summer and to find the overheating risk in a Passive House using an adaptive thermal comfort evaluation according to EN 15251 standard.

2. Method

2.1. Studied building description

One can see in Fig.1 a photo of the AMVIC building. It is an office building constructed according to Passivhaus standard in Bragadiru (latitude 44.4°N), a small town 10 km south of Bucharest, Romania.

The Passivhaus concept belongs to Passive House Institut of Darmstadt (PHI). It defines "Passive Houses" (PH) as a building, for which thermal comfort can be achieved solely by heating or cooling of the fresh air, without the need to recirculate it [16]. In temperate climate a building, in order to be certified as a passive one, must fulfill some criteria: Specific Space Heat Demand maximum 15 kWh/(m2y), Pressurization Test Result n50 max. 0.6 h-1, Entire

Specific Primary Energy Demand maximum 120 kWh/(m2y) including domestic electricity. All this criteria can be checked with Passive House Planning Package (PHPP) software [17].

AMVIC is the only one office Passive Building constructed into Romania and it is a ground floor and four levels building, inaugurated in February 2009 [18]. For the exterior walls of the building the U-value is 0.093 W/(m2K) and they was realized using AMVIC constructive system. The building is provided with low-emissivity triple-pane glazing windows with reduced overall heat transfer coefficient (Ug = 0.5 W/(m2K)) and high solar transmission factor (g-value = 0.33). The gross floor area is 2086 m2 and the enclosed volume is 9374 m3. The number was about 33 occupants at the time of measurements.

On the ground floor there is a wide open space where the sales department and the secretary's office are located. In a separated area there is a service room. The first, second and third floor are wide open office areas. On the top floor there are five apartments. AMVIC is well documented [19-21] and it has been monitored for a relatively long time (2009-2013). For the internal heat sources, heating and ventilation systems implemented in AMVIC details are given in [19-20].

Fig. 1. AMVIC office building - South-East façade.

2.2. Measurements surveys

The measurements survey spread over a long period of time in the summer of 2013, lasting from July 9 to August 19, with a total number of 16 distinct days of measurements. In the first part of this period the measurements were undertaken with ComfortSense device and in the second part of the survey it was used, IAQ-Calc™ Indoor Air Quality Meter 7545 made by TSI company, a professional instrument for investigating and monitoring indoor air quality (IAQ).

ComfortSense device is a system for measurement according to International Standard ISO 7730 [12], Fig. 2. The ComfortSense system consists of a main frame with build in A/D converter and USB 2.0 interface. A PC may be connected with this main frame and the measurement probes which are positioned on the system stand. From the PC the operator can communicate with the whole set-up at one time. The measurements procedure consists of replacing the chair of some workstations by the measurement station. The measurement is completed after 5 minutes and the measuring equipment must to be moved to the next work station on the list. The measurements with ComfortSense at AMVIC building took place on July 9 and July 11, 2013. On July 9, measurements were made for ground floor, first floor and a part of second floor. On July 11, measurements were made for the rest of second floor and forth floor. On the third floor the measurement cannot took place because at this level renovations were ongoing. There were undertaken measurements of thermal comfort parameters in a total of 56 posts of measurements. The time used for each measurement was three minutes, sampling step was set at 2.5 seconds. The ComfortSense software computed mean values for all measured data. The measurement period was between 12.30 and 17.30 in the date of July 9, 2013 and between 12.30 and 15.00 in the date of July 9, 2013. The positioning heights of the probes on the

measurement stand of ComfortSense were: for the operative temperature probe - 109 cm, for the humidity measuring probe - 89 cm and for the draft probe - 120 cm (with one exception, reception area, where occupants are standing - 180 cm). The probes mounted on the ComfortSense tripod can be seen in Fig.2 a) and b).

Fig. 2. ComfortSense set-up on its stand inside Amvic building - (a) in a meetings room located on the first floor; (b) in an office located on the

first floor

2.3. Questionnaire about thermal comfort

Simultaneous with the measurements of the environmental variables, people questionnaire surveys related to the thermal comfort were distributed to the workers inside the AMVIC building. In this survey were given 124 questionnaires to people in 16 different days.

The dates requested by questionnaire were: date and time of filling, the floor and the office number, the working place (POST), information about the person who had completed the questionnaire (name, age and sex). For the assessment of the thermal sensation (TSV) the subjects chose an option on the ASHRAE 7-points rating scale, they also chose what thermal preference had at the time of completion, they had to answer about the acceptability of the thermal environment and if to answer they felt some local thermal discomfort. The questionnaire included a checklist with clothing items for the peoples to choose from. They had to specify the activity they had been doing in the last 15 minutes before the moment of questionnaire filling. The filling time for one questionnaire was about 3-5 minutes.

3. Results and discussions

Fig. 3 shows the distribution of the thermal sensation votes, systematized for the entire survey period, between 9 July and 19 August 2013, using the data of Table 1. It represents a long study period situated in the middle of the summer so the results are relevant for this season. The predominant thermal sensation response, for all the building stories is "OK" with a maximum value of 80.6% respondents, founded at the ground floor. As we expected, the thermal sensation vote "increase" from the "cool" sensation to ground floor to the "warm" sensation to fourth floor. We observe at ground floor a maximum number of subjects, 35.7%, which votes "a bit cold", that means a TSV value of -1. It is observe an accentuated distribution of the votes to positive values at the fourth floor. Here are values for all possible positive responses of TSV, "a bit warm" (TSV=1) for 24% of respondents, "warm" (TSV=2) for 16 % of respondents and "hot" for 4% of respondents. The perfect equilibrium between cool and warm is realized at the first floor. Here the number of subjects who voted "a bit cool" is equal with the number of people who voted "a bit warm" and is equal to 9.7%, a small value in comparison with 80.6% which represent the percent of people who vote "OK". At the second floor the thermal sensation votes are centered near "OK", 69%, but with a little inclination to warm zone.

Table 1. Distribution of the thermal sensation votes of every buildings floor for all the measurement period

Number of respondents [%]

TSV Ground fl. First fl. Second fl. Fourth fl.

-3 0.0 0.0 0.0 0.0

-2 2.4 0.0 0.0 0.0

-1 35.7 9.7 6.9 4.0

0 47.6 80.6 69.0 52.0

1 11.9 9.7 20.7 24.0

2 2.4 0.0 3.4 16.0

3 0.0 0.0 0.0 4.0

Fig. 3. Distribution of the thermal sensation votes (TSVs) of every buildings floor for all the measurement period, expressed as percent of

respondents

Predicted mean vote (PMV) index quantifies the degree of discomfort and express the predicted response of a large group of subjects on ASHRAE seven point, psycho-physical scale (+3 hot, +2 warm, +1 slightly warm, 0 neutral, -1 slightly cool, -2 cool, -3 cold). It is an index of prediction and it is computed from measured values. Thermal sensation vote (TSV), represents the real response of the subjects to thermal environment. It is a value specific to each individ and usually it is obtained as a response to a questionnaire.

A systematization of the measurements data, in terms of PMV value and of questionnaires data, in the terms of TSV value is realized in the Table 2. It shows the mean values for each measurement day and each building floor for the thermal comfort indices PMV and TSV obtained to the measurements data, respectiv to the questionnaires data. This analysis is concentrated only on two days, founded in the first part of the summer survey realized at AMVIC building. In these days the measurements were done with the ComfortSense device and the PMV values could be precisely estimated. From the measured values the ComfortSense software computed the PMV value for each conducted measurement. The mean for each value for each building story can be found in the Table 2. As it was possible for each working place (measurement post), a thermal confort questionnaire was distribute to the people who work at that place. The mean for each building story and each measurement day for the TSV value recorded in questionnaire is found in the Table 2 too.

Table 2. Comparison between mean values of thermal sensation votes (TSVs) and predicted mean votes (PMVs) of every buildings floors for the days of measurements

Calendar date

9.07.2013 11.07.2013

Floor TSV mean PMV mean TSV mean PMV mean

Ground fl. -0.38 -0.65 - -

First fl. -0.20 -0.15 - -

Second fl. 0.00 0.13 -0.50 -0.28

Fourth fl. - - 0.78 0.70

The values in Table 2 are plotted in the graphs in Fig. 4. For the first measurement day, July 9, we observe good match between PMV and TSV. A little difference appears on the ground floor. That kind of difference, which means an exaggeration of the thermal sensation from PMV, could be caused by the people adaptive comportment. For the second day of measurement, July 11, a little difference between PMV and TSV votes could be found at the second floor. We looked at the input data for this floor results and observed that only two measurements were available for it so the results are not relevant.

□ PMV

Fig. 4. Comparative distribution of thermal sensation votes (TSVs) and predicted mean votes (PMVs) of every buildings floors for the days of

measurements - a) on July 9; b) on July 11

In the last part of this paper we want to present an adaptive thermal comfort evaluation of the AMVIC building for the two measurement days when ComfortSense device was used. For this purpose we used the evaluation method proposed by the EN 15251 standard. This adaptive evaluation could be applied only for free running buildings at the time of the survey. At the survey time in the AMVIC building operated an earth tube in the day time and in the night time the building was natural ventilated throw the opening of the windows. As results from [7] it would be useful to evaluate the constructions built in Passivhaus standard in adaptive approach. Looking at the results obtained in Table 2 we consider to be useful this kind of evaluation too. So we assimilate the AMVIC building as a free running one at the time of the survey and calculated the exponentially-weighted running mean of outdoor temperature for the measurement days as the standard request.

Trm7 = (Tod-1 + 0.8Tod-2 + 0.6Tod-3 + 0.5Tod-4 + 0.4Tod-5 + 0.3Tod-6 + 0.2Tod-7) / 3.8 (1)

The equation (1) represents the simplified formula given by standard EN 15251 [11] for exponentially-weighted running mean of outdoor temperature (Trm7). It used the average temperatures for seven previous days to the desired one. The exponentially-weighted running mean of outdoor temperature for July 9 and 11 was obtained using Table 1 and equation (1). In order to obtain the daily average of outdoor temperature it had been used daily real-time weather data from EnergyPlus Energy Simulation Software (Real-Time Weather Data) [22]. The used weather data

were obtained for Bucharest INMH. The meteo data file obtained for the requested period contained hourly values of exterior temperature. It had been done daily mean for all hourly values and the results are in Table 4.

33-,-----

19-------------------

18----------1----1--1----1--—

8 10 12 14 16 18 20 22 24 26 28 30

Exponentially-weighted running mean of outdoor temperature (°C)

Fig. 5. Operative temperatures of the surveys, plotted on the EN 15251 diagram for acceptable indoor temperatures in buildings without mechanical cooling (I, II and III correspond to the EN 15251 building categories)

Table 3. Data used for the realization of the graph shown in Fig. 5 (all values are temperatures [°C])

EN 15251

WITHOUT mechanical cooling systems

UPPER LIMIT LOWER LIMIT

CATEGORY I CATEGORY II CATEGORY III CATEGORY I CATEGORY II CATEGORY III

10 24.1 25.1 26.1 18 22.74 21.74 20.74

30 30.7 31.7 32.7 30 26.7 25.7 24.7

WITH HVAC systems

LANDSCAPED OFFICE (open plan office)

8 25.75 26.75 27.75 8 20.75 21.75 19.75

30 25.75 26.75 27.75 30 20.75 21.75 19.75

Comfort Temperature

10 22.1

30 28.7

EXT= exponentially-weighted running mean of outdoor temperature INT=indoor operative temperature

SURVEY 1 _9.07.2013 SURVEY 1_11.07.2013

EXT INT EXT INT

23.02 24.15 23.57 26.57

The operative temperature limits for conditioned buildings were also included in the graph with dashed line, as can be seen in Fig. 5. The category limits for free running buildings are represented with continuous line. The black dashed-dotted line in the graph is the comfort temperature in relation with the outdoor running mean temperature which was the base for deriving the upper and lower comfort zone limits of the EN 15251 diagram [13]. The data used to obtain the graph shown in Fig. 5 are presented in Table 3. According to the diagrams, operative temperature fell within the acceptability range for category I buildings of EN 15251 for date of 11.07.2013 (it is almost on the comfort line) and fell within acceptability for category II buildings for date of 09.07.2013. The explanation for this assessment is the fact that the point corresponding to July 11 is situated at a high level of indoor temperature than the point corresponding to July 9. This is due to the fact that the measurements on July 11 were undertaken at "warm" levels, second and preponderant to the fourth floor than the measurements undertaken on July 9, when the measurements were carried out at ground floor, first floor and second floor.

Table 4. Data used to obtain exponentially-weighted running mean of outdoor temperature according to EN 15251

T-1 [°C] T-2 [°C] T-3 [°C] T-4 [°C] T-5 [°C] T-6 [°C] T-7[°C]

09.07.2013

24.00 23.29 22.75 22.21 22.79 22.50 21.04

coef. 1.00 0.80 0.60 0.50 0.40 0.30 0.20

Trm7 [°C] 23.02

11.07.2013

23.92 24.13 24.00 23.29 22.75 22.21 22.79

coef. 1.00 0.80 0.60 0.50 0.40 0.30 0.20

Trm7 [°C] 23.57

4. Conclusions

In this paper were analyzed the results of a survey realized in summer period in a Passive House built in Romania. Field survey has been done in the summer of 2013, comfort parameters were measured inside the building and comfort questionnaires were distributed to the occupants. For the entire period of study in AMVIC building, the TSV distribution of every building floor over all the measurement period is presented. The responses are centered on "OK" vote and the tendency is from "cool" to "warm" from ground floor to fourth floor. For two days of survey, 9 July 2013 and 11 July 2013, the measurements and questionnaires results, expressed as PMV and TSV indices, are compared. Adaptive thermal comfort behavior is remarked. The building is assimilated to a free running one and an adaptive evaluation is done.

We can conclude that the people behavior in summer, in the AMVIC building, a Passive House with no additional cooling sistem, presents an adaptive behavior. So, adaptive thermal comfort evaluations, as in EN 15251 Standard, can be used.

Acknowledgements

This work was supported by Grant of the Romanian National Authority for Scientific Research, CNCS, UEFISCDI, PN-II-RU-PD-2012-3-0144. This work was also supported by project of the Romanian National Authority for Scientific Research, Sectoral Operational Programme "Increase of Economic Competitiveness" -financed by the European Regional Development Fund, Priority 2 Competitiveness Research -Development and Innovation, D2.2: Investments in RDI infrastructure and related administrative capacity O2.2.1: Development of existing CD and creation of new infrastructure (laboratories, research centers) ID 1883, SMIS-NSRF code 49 161.

Part of this work has been funded by the Sectoral Operational Programme Human Resources Development 20072013 of the Ministry of European Funds through the Financial Agreement POSDRU/159/1.5/S/138963

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