Online & Oslo, Norway
21-23 June 2021
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Session 4: Thermal environment in homes
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Assessing the indoor air quality of natural-ventilated bedrooms in renovated Norwegian houses using detailed field measurements
Small wooden dwellings are responsible for more than half of the total energy use in Norwegian buildings. Renovation usually includes a substantial improvement of the air-tightness, which reduces the air change rate due to infiltration. A recent study found that 60% of the Norwegian detached households made no changes to the ventilation system when performing an energy renovation, while only 9% installed balanced mechanical ventilation. The objective of this study is to investigate indoor air quality (IAQ) in window ventilated bedrooms in renovated houses.
Ten bedrooms in six case houses were investigated by measuring temperature, relative humidity, CO2, PM, formaldehyde and TVOC. The window opening angle was also logged with an accelerometer. The measurements were conducted over 2-3 weeks, during March and April. In addition, participants answered a questionnaire about motivation and habits on window opening. The dwellings were renovated single-family houses and terraced houses from 1950 – 80, in Trondheim. All the bedrooms had natural ventilation, and the occupants stated they used to open bedroom windows at night.
Results show that windows were open every night in most of the bedrooms. High CO2 levels were found in only two out of ten bedrooms. In the other bedrooms, the CO2 concentration was at a satisfying level during the nighttime. For some bedrooms, levels were higher during the day, when windows were closed. Six bedrooms had a time-averaged air temperature during nighttime below 18°C.
The work suggests that it is possible to achieve a high IAQ with manual window ventilation, also in energy renovated houses. This is however not guaranteed: not all bedrooms showed acceptable IAQ indicators. These results indicate that many occupants keep the bedroom windows sufficiently open for a good indoor air quality. However, the number of bedrooms investigated is too limited to generalize the conclusions.
Bacterial and fungal aerosols in dwellings with domestic animals: preliminary results
1Silesian University of Technology, Poland; 2Institute of Occupational Medicine and Environmental Health
The aim of the study was to obtain the preliminary properties of bacterial and fungal aerosols in selected city flats with small domestic animals, compared to reference flats (without animals). The research consisted in the simultaneous determination of bioaerosol concentrations in flats with animals and in reference flats with the same building and hygienic characterisctics as flats with animals. The samples of airborne bacteria and fungi were collected using a 6-stage Graseby-Andersen impactor. The species identification of bioaerosols was also carried out. It was found that in homes with pets, the concentration levels of fungal aerosol were only slightly increased, while the concentrations of bacterial aerosol were 2-3 times higher compared to the control (reference) apartments. Moreover, the presence of animals in apartments also influenced the species composition of the bacterial aerosol. In homes with a cat or a dog, a slightly increased proportion (contribution) of Gram-negative bacteria was observed. In turn, in apartments with aquariums with small fishes, there was a significant increase in the concentration of Gram-positive rods (Corynebacteria) and mesophilic actinomycetes (Actinomecytes). It was also observed that in houses with dogs, Staphylococcus intermedius, Propionibacterium avidum and bacteria from the Enterobacteriaceae family are often found, while the strain Plesiomonas shigelloides was found only in the air of dwellings with aquariums.
The risk of overheating and energy demand of new and old Finnish apartment buildings in the cooling season
1Mechanical engineering department, Aalto University, Finland; 2Finnish Meteorological Institute; 3Smart City Center of Excellence, TalTech, Estonia; 4Nanjing Tech University, China
This study has compared the risk of overheating of a new and old apartment building in Finland and aimed to improve the indoor temperature conditions of the new apartment building by means of the passive strategies (sun shading, window opening, and window properties) and an active cooling system. Seven different cases were defined and simulated. Regarding the results, the risk of overheating in the old building is significantly less than in the new building, and using new well-insulated windows with the same old wall construction in the old building, decreases the heating demand but has no significant effect on indoor air temperature. Hence the windows are more important for energy usage but not for the indoor air temperature in the old Finnish apartment building during the summer period. Using openable windows would be the best passive solution for keeping the indoor air temperature of the spaces of the new building within the comfort limits with less than 10% of the time above the recommended temperature limits based on En 15251 standard without any significant increase in heating demand. While using an active cooling system in the living room of each apartment is the only solution that can provide thermal comfort for 100% of the cooling season in all the spaces including bedrooms.
Evaluating the Influence of Ventilation Strategies on Energy Consumption and Indoor Air Quality in Residential Dwellings
1School of Physics & Ryan Institute’s Centre for Climate and Air Pollution Studies, National University of Ireland Galway, Galway, Ireland; 2School of Mechanical and Materials Engineering, UCD Energy Institute, University College Dublin
The International Energy Agency identified that energy efficiency is an important energy resource, highlighting that the "energy use avoided" by IEA member countries was larger than any other single supply-side resource. While there is potential for significant health and well-being benefits associated with improved energy efficiency; it is also documented that if energy efficiency measures are implemented incorrectly, they can have negative impacts on Indoor Air Quality. Regulatory measures need to ensure that multiple objectives are achieved in order to avoid policy failure. A realistic view of the trade-offs (thermal comfort, human health and energy performance) is required, if current policies are to be effective. An integrated approach is required to simultaneously achieve energy efficiency while also maintaining good indoor air quality. With a limited number of exceptions, the vast majority of studies focus on a single outcome at a time (thermal comfort, indoor air quality or energy consumption). The current study utilises a modelling framework that comprises of three existing models: CONTAM, EnergyPlus and IAPPEM. Each model has unique attributes that focus on the temporal and spatial distribution of indoor temperature profiles and energy consumption, dynamic airflow and pressure values, and indoor air pollution. This combined approach assesses both the energy performance and ventilation in energy-efficient dwellings. Simulations focus on assessing the energy consumption, risk of overheating and multiple indoor air pollutants (PM2.5, radon, humidity, CO2, CO, TVOCs). Five different archetypes (bungalow, two-storey dwelling, semi-detached, terrace and apartment) were developed. A matrix parametrisation approach incorporates varying room dimensions, meteorological conditions, ventilation and airtightness characteristics, building thermal characteristics, occupant profiles, outdoor air pollution concentrations and geogenic radon potential. The ventilation and energy performance parameterisation is based on recent updates to the Irish Technical Guidance Document. Simulations will assess the impacts on indoor air quality and energy consumption under i) various retrofits scenarios; ii) current and future climate scenarios; iii) current policies and projected future policy. This study will help in better understanding the relationship between energy consumption, ventilation, temperature, and indoor air quality in highly energy-efficient dwellings. The results will help inform future energy policy recommendations to ensure that the potential benefits, including those to health, are not compromised by the drive to towards improving the energy performance of the building stock.
Subjective assessments of bedroom environment in the heating season in Denmark
1Research Group Building Physics, Construction and Climate Control, Department of Architecture and Urban Planning, Ghent University, Belgium; 2International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Denmark; 3School of Design and Environment, National University of Singapore, Singapore; 4Department of Architecture, Waseda University, Japan
A satisfied bedroom environment is vital for the sleep quality of human beings. Thermal comfort, air quality, acoustic comfort, and visual comfort are all verified to be indispensable for the overall bedroom comfort. However, few studies reported how occupants rate those environmental aspects in their bedrooms. The present study figured out this question by online morning and evening sleep diaries conducted in the capital region of Denmark in the heating season. A total of 169 sets of responses to the sleep diaries from 82 subjects were received. Compared to those who accepted the bedroom environment, the subjects had the highest levels of the unacceptability of noise, following by stuffy air and a hot bedroom. Acoustic and thermal comfort and air quality can be improved for occupants to have a more satisfactory bedroom environment. The present study gives a sight of which aspects should be improved for people to have a better bedroom environment.
The relation between indoor air quality in a bedroom and sleep quality of ageing adults
1Eindhoven University of Technology (TU/e), Netherlands, The; 2VIAC adviseurs, Houten, Netherland, The
The present study examined the effect of the indoor air quality, indicated by CO2 levels, on sleep quality of ageing adults. Bedroom indoor air quality was changed by increasing the ventilation rate with a mechanical ventilation system with heat recovery with the intention to decrease the CO2 levels.
Twenty-two volunteers were studied during four consecutive nights in their bedroom at two different settings of the mechanical ventilation with heat recovery (high and low). During the night indoor air quality was measured continuously (CO2, temperature, and relative humidity), additionally the background noise was measured. Physiological indicators of sleep quality were analyzed using actigraphy (Sensewear). Three different questionnaires (PSQI, GSQS and sleep diary) provided subjective data on sleep quality and the Hope questionnaire provided subjective data on the perception of the indoor climate.
Bedroom CO2 increased rapidly during the night at a low ventilation rate (15 m3/h) to 1409 ±412 ppm, but remained low at the high ventilation rate of 91 m3/h (680 ±106 ppm CO2). At the same time air humidity decreased at the high ventilation rate. The sound pressure level remained low at the low ventilation rate (35 ±2 dB) but increased to 39 (±4) dB at the high ventilation rate. The bedroom air temperature remained stable and did not, as opposed to the other indicators, differ significantly between the conditions.
The sleep quality obtained with the Sensewear was not affected by the change in IAQ. Also no significant difference was analyzed for the PSQI and the GSQS questionnaire. However, the HOPE questionnaire (indoor air quality) had multiple significant correlations with the measured indoor environmental quality. The subjects rated the air fresher but experienced more air draft with the high ventilation rate. The results of the sleep diary (length of sleep and latency) were correlated with the results obtained with the Sensewear.
Characteristics of the subjects appeared to have a significant effect on sleep conditions (age) and on indoor air quality perception (gender). Older people experienced more nightly awakenings, and the depth of sleep was significantly better. Women judged the air quality significantly lower when compared to men.
The resulting CO2 levels and the heating/cooling consumption of apartments with balanced ventilation versus window ventilation
Four apartments have been monitored for an entire year. Two apartments were ventilated with a balanced ventilation system, and two apartments were ventilated by manual opening of windows. CO2 values have been registered as indication of indoor air quality in each living room and the available bedrooms. The opening of windows and doors was registered, from which an airing factor was calculated. The heating and cooling consumptions was also registered for each apartment.
The CO2 levels in all rooms of the apartments with balanced ventilation was lower than the manually ventilated apartments, with less variation between hours and seasons. The percentage of hours exceeding 1000 ppm is below 1% of the year for the apartments with balanced ventilation and 30-60% of the year for window ventilated apartments.
Space heating and cooling use are investigated by energy signatures of the four apartments. The balanced ventilation - including recovery - not only brings a higher indoor air quality, but also a lower heating
(-24%) and cooling use (-50%) as follows from the specific heating slope and specific cooling slope in the energy signatures.
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