EVALUATION OF THE INDOOR AIR QUALITY IN A SINGLE FAMILY ACTIVE HOUSE

Transcription

1 Topic A8: IAQ and perceived indoor air quality EVALUATION OF THE INDOOR AIR QUALITY IN A SINGLE FAMILY ACTIVE HOUSE Christoffer PLESNER * and Karsten DUER VELUX A/S, Daylight Energy and Indoor climate, Aadalsvej 99, 2970 Hørsholm, Denmark * Corresponding christoffer.plesner@velux.com Keywords: Indoor air quality, natural ventilation, evaluation of indoor climate, openable windows, active house SUMMARY The indoor air quality (IAQ) of the 130 m 2 zero energy single-family Active house Maison Air et Lumiére (MAL) equipped with hybrid ventilation was evaluated where a special focus was on the effects from the natural ventilation system during summer. The evaluation was only based on CO 2 levels and evaluated according to the Active house specifications, 2 nd edition. There was a tendency to improved IAQ in summer using natural ventilation than in winter using mechanical ventilation through lower CO 2 levels. It was shown in the bedrooms, living room and mezzanine that openable roof windows help maintain low CO 2 levels. All the rooms were evaluated and achieved CO 2 levels in category 1-2 (<1150 ppm) during summer for 95% of the time and for the all-year average also achieved category 1-2. The natural ventilation system showed low CO 2 levels and thereby satisfactory IAQ regardless of climate conditions in summer using openable windows without using mechanical energy. INTRODUCTION: Increasingly stricter energy requirements in buildings have caused more airtight and wellinsulated buildings, which in effect require more effective ventilation to eliminate indoor climate issues such as elevated humidity levels, stuffy air and overheating issues. This has put great focus on how to achieve a good indoor climate in low energy buildings. The Model Home 2020 project where five single-family houses were newly built or refurbished between 2009 and 2011 illustrates the vision of how future buildings can be both climate-neutral and comfortable using the Active house principle (VELUX, 2009). In 2011 the zero energy single-family Active house, Maison Air et Lumiére (MAL) with a size of 130 m 2 near Paris was completed as the final of the five houses in the project as seen in Figure 1. The house is equipped with a fully automated hybrid ventilation system that combines the advantage of mechanical ventilation with heat recovery in winter with natural ventilation by controlled openable windows during summer. A family consisting of 2 parents and 2 kids resided MAL from 1st of September 2012 until 31st of August The family were asked to fill out questionnaires regarding the energy, daylight, indoor air quality (IAQ), acoustics and temperature aspects of the house. The answers of interest are the replies about the IAQ.

2 Figure 1. Zero energy single-family Active house, Maison Air et Lumiére (VELUX, 2009) The objective of this article is to evaluate the IAQ for the occupied period with special focus on the effects from the natural ventilation system. It is chosen that only CO 2 levels will be evaluated. A previous article on MAL showed that good thermal comfort was achieved by openable windows which in effect could lower indoor temperatures about 5 C (Peuportier et al., 2013). METHODOLOGIES The evaluation of the IAQ in the house was done by gathering data from the occupied period, September 2012 till August 2013 and was derived from detailed event-driven data logging of the built-in sensors placed in each room of the house. Indoor air temperature, CO 2, relative humidity and outdoor climate data was logged together with the exact opening degrees of all openable windows in the house. The IAQ was evaluated using the Active house specifications, 2 nd edition (Active house, 2013). In terms of winter/summer, the seasons are different from to depending on country and in this article the Danish seasons are used as reference even though the house is located in France hereby defining winter season from December till end of February and summer season from June till end of August (DMI, 2013). The transition periods are present in the all-year graphs in the article but are not evaluated separately. CO 2 evaluation The evaluation of CO 2 is based on four categories, where an additional category 5 is added to evaluate CO 2 levels that are above category 4 as seen in Table 1. An outdoor CO 2 level of 400 ppm is assumed. The requirements of Table 1 should be met for a minimum (min) of 95% of the occupied time (Active house, 2013). In this article, the occupied time is defined as all hours for all rooms excl. bedrooms and defined as night hours for the bedrooms set from 22 in the evening till 6 in the morning. Threshold values for CO 2 are set in this article to better make a comparison between the bedrooms and other rooms as there is a vast difference in CO 2 concentrations in e.g. bedrooms where high levels are achieved during night as the volume per person is often lower. For all rooms excl. bedrooms the CO 2 threshold value is in this article set to category 2 (<1150 ppm) which should be met for min. 95% of the time and for bedrooms set to category 4 (<1600 ppm) which should be met for min. 95% of the night hours. CO 2 concentrations of 1600 ppm is not necessarily a high level for bedrooms as they often exceed this as seen in (CEN, 2005) but is in this article used as basis for evaluating CO 2 levels in bedrooms. As the bedrooms are evaluated for night hours, which are the worst case periods makes the set criteria harder to fulfil than for all other rooms as they are evaluated for all hours.

3 Table 1. CO 2 level according to Active house specifications, 2 nd edition Category CO 2 (ppm) CO 2 (ppm) Category 1 < (outside concentration) Category 2 < (outside concentration) Category 3 < (outside concentration) Category 4 < (outside concentration) Category 5 > (outside concentration) RESULTS AND DISCUSSION: During the occupied period the evaluated rooms in focus are the bedrooms, living room and mezzanine. During this period there has been three periods where no data has been recorded. These periods are illustrated in the yearly temporal maps as in e.g. Figure 3, which are colored white to show a clear distinction. Apart from this all other data is present. CO 2 levels in MAL In this section the IAQ is evaluated using the CO 2 levels in Table 1 for different months and rooms. First the month of June is evaluated for all rooms to get a general overview of how MAL performs during summer. During June it can be seen from Figure 2 that all rooms achieve category 1-2 for min. 95% of the time (red line), with the majority of the time being in category 1 (<900 ppm). The bedrooms are in this article evaluated for night hours only, although are in Figure 2 also shown for all hours for comparison. Overall low CO 2 levels are achieved in June for all rooms. MAL 2013 June All hours All rooms - CO2 Bedroom (1st) B Mezzanine 1 (1st) Bathroom (1st) Bedroom (1st) A Rooms Mezzanine 2 (1st) Technical Bathroom WC Bedroom Cat I (<900 ppm) Cat II (<1150 ppm) Cat III (<1400 ppm) Cat IV (<1600 ppm) Cat 5 (>1600 ppm) Living room Kitchen Entrance 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % of time when CO2 category is valid Figure 2. Categories for CO 2 in all rooms for all hours during June 2013 In Figure 3 the living room is evaluated where it is noted that CO 2 levels are below 1150 ppm when roof windows are open for the vast majority of the year except only short periods from

4 hours in November and December. Overall the natural ventilation system during summer achieves low CO 2 levels below 1150 ppm in the living room. Figure 3. Window opening and CO 2 levels for roof windows in living room CO 2 levels in bedrooms In this section the natural ventilation system in MAL is evaluated to see if low CO 2 levels can be achieved during summer by openable windows. There are three bedrooms which show similar tendencies and for this section only bedroom B on 1 st floor is evaluated, first on a monthly basis in Figure 4 and in a yearly temporal map in Figure 5. In Figure 4 CO 2 levels in both summer and winter achieve category 1-4 for min. 95% of the night hours thereby fulfilling the set requirements in bedrooms. During summer the CO 2 levels are in category 1 for 85-97% of the night hours while in winter only in category 1 for 60-95% of the night hours. This concludes that the CO 2 levels are generally lower in summer with natural ventilation mode than in winter with mechanical ventilation mode. 100% MAL Bedroom (1st) B Night Yearly - CO2 90% 80% % of CO2 category 70% 60% 50% 40% 30% 20% 10% 0% Month Cat I (<900 ppm) Cat II (<1150 ppm) Cat III (<1400 ppm) Cat IV (<1600 ppm) Cat 5 (>1600 ppm) Figure 4. Monthly CO 2 levels for bedroom B (1 st floor) for night hours

5 In Figure 5 a temporal map of bedroom B illustrates that e.g. during the night in July windows are open while achieving CO 2 levels below the set threshold value of 1600 ppm (light green). During summer from June to August windows are open the majority of the time achieving low CO 2 levels below the threshold. Interestingly the ventilation flap in the roof windows are open from July to August from hours, hence also achieving low CO 2 levels (dark green). During winter the roof windows are closed while also achieving low CO 2 levels due to the mechanical ventilation system. These findings underline that open windows and flaps contribute to a satisfactory IAQ by showing low CO 2 levels. Figure 5. Window opening and CO 2 levels for roof windows in bedroom B (1 st floor) In Figure 6 all rooms excl. bedrooms are shown with their corresponding all-year average CO 2 category. The goal is that category 1-2 should be achieved for min. 95% of the time. It is clear that all rooms achieve category 1-2 for 95% of the time thereby concluding that the overall CO 2 levels in MAL are very low. MAL All hours CO2 levels - all year average Mezzanine 1 (1st) Bathroom (1st) Mezzanine 2 (1st) Rooms Technical Bathroom WC Living room Kitchen Cat I (<900 ppm) Cat II (<1150 ppm) Cat III (<1400 ppm) Cat IV (<1600 ppm) Cat 5 (>1600 ppm) Entrance 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % of time when CO2 category is valid Figure 6. All year average CO 2 levels for all rooms and for all hours excl. bedrooms

6 Effect of natural ventilation system by evaluating CO 2 in bedroom B and mezzanine 2 The effect of the natural ventilation system was evaluated in bedroom B and mezzanine 2 on on 1 st floor by looking at the window opening degrees in regard to the CO 2 levels for 3 days in July and 2 days in June. It can be seen from Figure 7 that on the 12 th of July in the morning the rapid increase in CO 2 is due to the closing of the window (green line). It is also evident that when windows are open CO 2 levels decrease as seen during the 9 th of July. This shows that the natural ventilation system can maintain low CO 2 levels and thereby has a positive effect on the IAQ in the in bedroom MAL 2013 Bedroom (1st) B July CO2 & APO levels for 3 days CO2 [ppm] Date and time CO2 APO (window opening) Figure 7. Window opening degrees and CO 2 levels for bedroom B (1 st floor) in July 2013 For the mezzanine 2 it is clear from Figure 8 that when the roof windows are closed during the day the CO 2 levels increase. From around 10:00 each day the windows start opening and consequently the CO 2 levels decrease proving that the natural ventilation system also in the mezzanine works efficiently by maintaining low CO 2 levels. 700 MAL 2013 Mezzanine 2 (1st floor) June CO2 & APO levels for 2 days CO2 [ppm] Date and time CO2 APO (window opening) Figure 8. Window opening degrees and CO 2 levels for Mezzanine 2 (1 st floor) in June 2013

7 Both cases underline that the natural ventilation system helps maintain low CO 2 levels during all of summer in both the bedroom B and mezzanine 2. There is generally a clear tendency that the natural ventilation system works all the time during summer regardless of the climate conditions by achieving low CO 2 levels when needed and in general creating a good IAQ. Comparisons to other literature and answers from questionnaires An investigation has been done in United Kingdom where the Good home alliance (GHA) has gathered examples of measurements from homes of all types with good IAQ (Good home alliance, 2011). To compare results the average CO 2 level from 5 single family houses in the GHA homes built between were compared to MAL. The average CO 2 level for GHA homes was 889 ppm and can be directly compared to MAL, which had a yearly CO 2 average for all rooms excl. bathrooms, toilets and technical rooms of 614 ppm. This comparison shows that MAL has a much lower CO 2 average and thereby performs betters in regard to IAQ than the 5 new built and investigated GHA homes. In a bedroom of 9 m 2 consisting of 2 adults with a min. air exchange of 0,5 h -1 a maximum CO 2 level at equilibrium of 2500 ppm can be expected (CEN, 2005). Making the calculation for a 14 m 2 room CO 2 levels reach roughly 1800 ppm which could be compared to one of the bedrooms in MAL, namely bedroom on ground floor which is 14 m 2 reaching a maximum CO 2 level of 1868 ppm for the one year period showing similar levels, concluding that MAL performs well. The responses from the questionnaires given to the occupants living in MAL should indicate how they feel living in a model home It was stated by the occupants that they did not experience any problems living in the house and when asked what they did to improve the air quality they replied that they would open the roof and façade windows to make draught (VELUX, 2012). Overall the occupants rate the indoor climate in the house as very good. Also the occupants state that their children sleep better in this home than their former, in general experience a better health and have fewer sick days. Overall the feedback from the occupants was very positive and was in accordance with the results found from the measurements. Discussion The three periods of missing data are unfortunate and makes it more difficult to evaluate the IAQ during these times e.g. in most of May, but would probably not change the main findings of this article. Furthermore, by evaluating the bedrooms in the house using night hours it was harder to fulfill the set requirements but the bedrooms managed to fulfill them regardless. CONCLUSIONS: The indoor air quality was evaluated for an entire year from September 2012 until August 2013 in the zero energy single-family Active house, Maison Air et Lumiére using CO 2 as main evaluation parameter. The key issue was to investigate the role of natural ventilation by openable windows based on the requirements from the Active house specifications, 2 nd edition by verifying if category 2/4 was fulfilled 95% of the time in the rooms. The rooms in focus were the bedroom on ground floor, bedroom B, living room and mezzanine 2.

8 The natural ventilation system in MAL showed that the openable roof and façade windows was able to lower and/or maintain low CO 2 levels in both the bedrooms, living room and mezzanine. The bedrooms in the house were evaluated stricter than the other rooms, as the set requirement were based on night hours only. The results showed that in bedroom B during summer the CO 2 levels were in category 1 (<900 ppm) for 85-97% of the night hours, compared to only 60-95% of the time during winter. It was also shown that the bedroom on ground floor reached a maximum CO 2 level of ppm for the whole year, which is similiar to the CO 2 level of 1800 ppm found by calculation for 0,5 h -1. Overall the bedrooms showed lower CO 2 levels in summer using natural ventilation than in winter using mechanical ventilation. The living room had CO 2 levels in category 1-2 for the vast majority of the year, concluding that a satisfactory IAQ was present. When evaluating all the rooms at once during the typical summer month of June, all rooms were in category 1-2 for 95% of the time and for the allyear CO 2 average category 1-2 was also achieved for 95% of the time. The aim of this article was to evaluate the performance of the natural ventilation system in MAL and therefore a comparison was made with 5 new built homes with good IAQ that Good homes alliance (GHA) had investigated. The average CO 2 level for MAL for all rooms excl. bathrooms, toilets and technical rooms was 614 ppm, whereas the average CO 2 level for the investigated GHA homes was 889 ppm, showing that MAL has a much lower CO 2 average and thereby performs betters in regard to IAQ than the 5 new built GHA homes. There is generally a clear tendency that the natural ventilation system performed well by regulating according to the needs of the building while achieving low CO 2 levels in summer thereby creating a satisfactory IAQ. Furthermore the natural ventilation system worked all the time during summer regardless of the climate conditions. Finally the openable windows were able to provide a good IAQ during summer without the use of mechanical energy for air flow. ACKNOWLEDGEMENT Nicolas Dupin from VELUX, France and Peter Foldbjerg from VELUX A/S, Denmark has supported with knowledge on Maison Air et Lumiére and Active house specifications through valuable discussions. REFERENCES VELUX (2009) Model Home 2020 buildings B. Peuportier, K. Duer, C. Plesner and N. Dupin (2013) Evaluation of ventilative cooling in a single family house. Proceedings of AIVC conference 2013 Active house (2013) Active house specifications, 2 nd edition Danish weather institute (2013) CEN (2005) CEN/TR 14788:2005, Ventilation for buildings. Design and dimensioning of residential ventilation systems Good homes alliance (2011) Ventilation and good indoor air quality in low energy homes %20PUBLICATION.pdf Questionnaires on indoor climate given to occupants of Maison Air et Lumiére ( )