Material emission rates: Literature review,and the impact of indoor air temperature and relative humidity

An extensive literature review of research on the impact of indoor air conditions; temperature, relative humidity and surface air velocity on materials emission rates is presented. This paper also presents the results of an experimental work to study the impact of room air temperature and relative humidity on materials emission rates. The results indicate that both the temperature and relative humidity have a significant effect on the emissions from paint and varnish. In the case of varnish, the results were consistent with earlier results. However, the paint results show inconsistent emission behaviour. Further, for both materials, the individual compounds did not necessarily follow the same trend established for the TVOC.     

Impact of Temperature and Humidity on the Perception of Indoor Air Quality

Abstract Sensory responses to clean air and air polluted by five building materials under different combinations of temperature and humidity in the ranges 18-28°C and 30-70%RH were studied in the laboratory. A specially designed test system was built and a set of experiments was designed to observe separately the impact of temperature and humidity on the perception of air quality/odour intensity, and on the emission of pollutants from the materials. This paper reports on the impact on perception. The odour intensity of air did not change significantly with temperature and humidity; however, a strong and significant impact of temperature and humidity on the perception of air quality was found. The air was perceived as less acceptable with increasing temperature and humidity. This impact decreased with an increasing level of air pollution. Significant linear correlations were found between acceptability and enthalpy of the air at all pollution levels tested, and a linear model was established to describe the dependence of perceived air quality on temperature and humidity at different pollution levels.     

Sensory and chemical evaluation of odorous emissions from building products with and without linseed oil

Natural materials of biological origin degrade over time and may emit odorous chemical compounds that can influence the perceived indoor air quality. The objective of this study was to investigate how the perceived air quality is influenced by emissions from building products with linseed oil compared with similar conventional synthetic products without linseed oil. Two types of linoleum, two types of wall paint and two types of floor oil were selected as examples of natural products containing linseed oil. The selected synthetic products were PVC floor covering, a water-based paint, and a synthetic floor oil. The emissions from the products were monitored over a one-year period in small ventilated test chambers. The odorous emissions were evaluated by sensory panel assessments of odour intensity and acceptability and by chemical analysis of the odour-active volatile organic compounds (VOCs) and carbonyl compounds. Odour-active VOCs in the emissions from one floor oil with linseed oil and two pure linseed oils were detected by gas chromatography combined with olfactometry (GC-O) and attempted identified with mass spectrometry (MS). The products with linseed oil influenced the perceived air quality more negatively than the similar synthetic products and the odour was persistent over time. It was found that the products with linseed oil did not qualify for the Danish Indoor Climate Label, because of the persistency of the odour. The results of the GC-O/MS investigations and VOC measurements indicated that an almost constant emission of odour-active VOCs with low odour thresholds resulted in the persistency of the odour. The VOCs probably originated from oxidation products from the linseed oil used as raw material. The study indicates that the acceptability of the emissions from the floor oil was influenced by the linseed oil used as raw material. It is therefore suggested that systematic use of less odorous linseed oils may improve the acceptability of the emission from products with linseed oils. The applied combination of sensory assessment of perceived air quality and GC-O/MS seems to be a useful approach in the effort to eliminate unwanted odours from building products.     

Space conditioning using evaporative cooling for summers in Delhi

The article examines the possibility of space conditioning the interiors of a multistorey office building in Delhi using evaporative cooling in the summer months of April, May and June. The temperature and humidity conditions obtained in a room of the building with direct evaporative cooling are studied by simulation. In this case study, the room is assumed to have a south-facing wall with a window and all other walls, ceiling and floor are interior partitions. The effect of number of air-changes per hour (ACH) from 1 to 40 and fresh-air bypass factor (BPF) 0% to 100% on performance is studied by simulation. The aim is to find whether some combination of ACH and BPF succeeds in keeping room conditions below 80% RH and temperatures between 27 and 31°C, depending on RH. It is found that the desired results are achieved by keeping the ACH and the BPF within certain limits depending on weather conditions. If the temperature and relative humidity of the ambient air are too high then a direct evaporative cooler cannot achieve comfort in the room. Appropriate combinations of ACH and BPF have to be selected to obtain the best results.     

Diffusion‐controlled reference material for VOC emissions testing: effect of temperature and humidity

A polymethylpentene film loaded with toluene is being developed as a reference material to support the reliable measurement of volatile organic compound emissions from building materials using environmental chambers. Earlier studies included the measurement of the material‐phase diffusion coefficient (D) and material/air partition coefficient (K) at 23°C. A fundamental mass‐transfer model can then be used to predict toluene emissions from the reference material at 23°C, serving as a reference for validating chamber‐measured emission profiles. In this study, the effect of temperature and humidity on performance of the reference material was investigated. Reference material emissions were measured at 10, 23, and 30°C and at different relative humidity (RH) levels. D and K at different temperatures and RH were determined using an independent method. Results showed that RH does not significantly affect D and K and had no effect on emissions. However, emissions increased substantially at elevated temperatures due to the relationship between D and temperature. A statistical analysis shows good agreement between model‐predicted and measured gas‐phase concentrations, indicating that the model can accurately predict emission profiles as a function of temperature. The reference material can therefore be applied to a wide range of emission chamber testing conditions.     

Decreased humidity improves cognitive performance at extreme high indoor temperature

In this study, we examined the cognitive performance of subtropically acclimatized subjects at an extreme high indoor temperature and the effect of decreased humidity on the cognitive performance at the high temperature. Forty-eight healthy subjects experienced the three exposure conditions: 26°C/relative humidity (RH) 70%, 39°C/RH50%, and 39°C/RH70% in a climate chamber. During 140-minute-long exposures to each thermal condition, they were required to perform cognitive tests that assess the perception, spatial orientation, concentration, memory, and thinking abilities. Meanwhile, their heart rate, core temperature, skin temperature, blood pressure, and body weight were measured and subjective responses, that is, thermal comfort, perceived air quality, and acute health symptoms were investigated. At the relative humidity of 70%, increasing indoor temperature from 26°C to 39°C caused a significant decrease in the accuracy of these cognitive tests. However, when the relative humidity decreased from 70% to 50% at 39°C, the accuracy of the cognitive tests increased significantly. Accordingly, the physiological and subjective responses of the subjects changed significantly with the changes in indoor temperature and humidity, which provided a basis to the variation in the cognitive performance. These results indicated that decreasing indoor humidity at extreme high temperature could improve the impaired cognitive performance.     

Impact of Temperature and Humidity on Perception of Indoor Air Quality During Immediate and Longer Whole-Body Exposures

Abstract Acceptability of clean air and air polluted by building materials was studied in climate chambers with different levels of air temperature and humidity in the ranges 18–28°C and 30-70% relative humidity (RH). The acceptability of the air quality immediately after entering a chamber and during the following 20-min whole-body exposure was assessed by 36 untrained subjects who maintained thermal neutrality by modifying their clothing. The results confirm the significant decrement of the acceptability with increasing temperature and humidity, as shown in a previous study with facial exposures. The odour intensity was found to be independent of temperature and humidity. A linear relation between acceptability and enthalpy of air was again observed by this experiment. No significant difference was observed between the immediate acceptability and the acceptability during the following 20-min exposure, i.e., no adaptation took place. Both the immediate assessment of acceptability and the assessments during the 20-min exposure were independent of the air temperature and humidity to which the subjects were exposed before entering the chamber. The results further indicate that a notable decrement of the ventilation requirement may be achieved by maintaining a moderate enthalpy of air in spaces.     

The effect of wet film thickness on VOC emissions from a finishing varnish

Finishing varnishes, a typical type of oil-based varnishes, are widely used to shine metal, wood trim and cabinet surfaces in Hong Kong. The influence of wet film thickness on volatile organic compound (VOC) emissions from a finishing varnish was studied in an environmental test chamber. The varnish was applied on an aluminium foil with three different wet film thickness (35.2, 69.9 and 107.3 microm). The experimental conditions were 25.0 degrees C, 50.0% relative humidity (RH) with an air exchange rate of 0.5 h(-1). The concentrations of the major VOCs were monitored for the first 10 h. The air samples were collected by canisters and analysed by gas chromatography/mass selective detector (GC/MSD). Six major VOCs including toluene, chlorobenzene, ethylbenzene, m,p-xylene, o-xylene and 1,3,5-trimethylbenzene were identified and quantified. Marked differences were observed for three different film thicknesses. VOC concentrations increased rapidly during the first few hours and then decreased as the emission rates declined. The thicker the wet film, the higher the VOC emissions. A model expression included an exponentially decreasing emission rate of varnish film. The concentration and time data measured in the chamber were used to determine the parameters of empirical emission rate model. The present work confirmed that the film thickness of varnish influenced markedly the concentrations and emissions of VOCs.     

Simultaneous heat and moisture transfer in soils combined with building simulation

In order to precisely predict ground heat transfer, room air temperature and humidity, a combined model has been developed and conceived to calculate both the coupled heat and moisture transfer in soil and floor and the psychrometrics condition of indoor air. The present methodology for the soil is based on the theory of Philip and De Vries, using variable thermophysical properties for different materials. The governing equations were discretized using the finite-volume method and a three-dimensional model for describing the physical phenomena of heat and mass transfer in unsaturated moist porous soils and floor. Additionally, a lumped transient approach for a building room and a finite-volume multi-layer model for the building envelope have been developed to integrate with the soil model. Results are presented in terms of temperature, humidity and heat flux at the interface between room air and the floor, showing the importance of the approach presented and the model robustness for long-term simulations with a high time step.     

Organic compounds in office environments - sensory irritation, odor, measurements and the role of reactive chemistry

Abstract Sensory irritation and odor effects of organic compounds in indoor environments are reviewed. It is proposed to subdivide volatile organic compounds (VOCs) into four categories: (i) chemically non-reactive, (ii) chemically 'reactive', (iii) biologically reactive (i.e. form chemical bonds to receptor sites in mucous membranes) and (iv) toxic compounds. Chemically non-reactive VOCs are considered non-irritants at typical indoor air levels. However, compounds with low odor thresholds contribute to the overall perception of the indoor air quality. Reported sensory irritation may be the result of odor annoyance. It appears that odor thresholds for many VOCs probably are considerably lower than previously reported. This explains why many building materials persistently are perceived as odorous, although the concentrations of the detected organic compounds are close to or below their reported odor thresholds. Ozone reacts with certain alkenes to form a gas and aerosol phase of oxidation products, some of which are sensory irritants. However, all of the sensory irritating species have not yet been identified and whether the secondary aerosols (ultrafine and fine particles) contribute to sensory irritation requires investigation. Low relative humidity may exacerbate the sensory irritation impact. Practical Implications Certain odors, in addition to odor annoyance, may result in psychological effects and distraction from work. Some building materials continually cause perceivable odors, because the odor thresholds of the emitted compounds are low. Some oxidation products of alkenes (e.g. terpenes) may contribute to eye and airway symptoms under certain conditions and low relative humidity.     

Subjective Indoor Air Quality in Schools – The Influence of High Room Temperature,Carpeting, Fleecy Wall Materials and Volatile Organic Compounds (VOC)

There is a growing concern about indoor air quality (IAQ) in schools. We have studied relations between subjective indoor air quality (SIAQ) and measured IAQ among school personnel (N = 97) in six mid-Swedish primary schools. Information on SIAQ and the psychosocial work environment was measured by a self-administered questionnaire, using analogue rating scales. Indoor exposures were quantified by hygienic measurements. Perception of high room temperature was related to a poor climate of cooperation, fleecy wall materials, and the concentration of volatile organic compounds (VOC), including xylene, limonene, and butanols. Perception of air dry-ness was related to atopy, work stress, poor climate of cooperation, high room temperature, low air humidity, and high VOC concentration, including, limonene, and n-alkanes. Perception of dusty air was related to work stress, the role of schoolteacher, and exposure to 2-ethyl-1-hexanol. No relations were found between SIAQ and CO2, building age, or respirable dust. To achieve a good SIAQ, room temperature should be kept at a maximum of 22°C, and exposure to VOCs and fleecy materials should be minimized. Finally, a sound psychosocial work climate is essential for the perception of a good physical indoor climate.     

Health-Related Evaluation of Building Products based on Climate Chamber Tests

A procedure is developed for assessing the health effects of the emissions from building products. The procedure is based on:

• ? emission rates measured in environment test chambers
• ? a fixed standard room with fixed standard conditions
• ? a maximum acceptable concentration in the indoor air of each of the chemical compounds emitted, I_v a maximum permissible contribution to I_v from building products.

The procedure has two elements: evaluation of the emitted compound alone and evaluation of the compound together with other compounds and indoor air factors. The evaluation includes odour and health effects of the compounds. The procedure has been applied to the emission test results for two building products: a rubber floor covering, and a water-borne acrylic watt paint. Maximum acceptable indoor air concentrations are listed fin-selected chemical compounds emitted by these two materials.     

A performance comparison of passive and low-energy buildings

This paper compares apartments in two residential blocks in Vienna; one passive and the other one low-energy. These blocks were constructed simultaneously in the same location and with comparable building construction features and floor plans. The main difference between the two blocks (other than the higher thermal insulation level in the passive building) lies in the ventilation system: passive buildings deploy controlled ventilation, whereas the low-energy buildings rely mostly on user-operated natural (window) ventilation. We measured indoor environmental conditions (indoor air temperature, relative humidity, and CO₂ concentration) in two units of each block over a period of five months. Additionally, the buildings were compared in view of operation and embodied energy use, CO₂ emissions, and construction costs.     

Monitoring of the building envelope of a heritage house: a case study

The paper describes the long-term monitoring of the hygrothermal performance of the building envelope of a heritage house located in Ottawa. The house, once the residence of two of Canada's Prime Ministers, now serves as a museum. To preserve the historical artifacts within the building, the specified temperature and relative humidity (RH) for the indoor air are 21°C and 35% to 50%, respectively. As the house must also be preserved, there was concern about the effect of the high indoor RH (moisture) on the durability of the building structure. The main objective of the monitoring was to assess the effect of the conditioned air on the building envelope. Selected wall sections and a window were continuously monitored from March 1995 to August 1996. The monitoring included indoor and outdoor conditions and the attic environment. Temperature, RH, surface wetting–drying cycles (from precipitation or condensation), and air-pressure differential were monitored. This paper describes the monitoring approach and results. The results indicated that the brick walls are unlikely to experience internal condensation problems as long as they are subjected to a negative air pressure difference. However, because the building is quite leaky, the negative pressure introduced too much cold dry air from the exterior. It caused localized cold spots with condensation and ice formation on interior of walls and ceiling. Negative air pressure differences are not a solution unless the leakage paths are reduced.     

Evaluating the role of ivy (Hedera helix) in moderating wall surface microclimates and contributing to the bioprotection of historic buildings

The role of ivy (Hedera helix L.) on building walls is much debated, with arguments being put forward for it playing a biodeteriorative role (for example through ivy rootlets exploiting cracks and holes) as well as suggestions that it might provide some bioprotection (for example by the ivy canopy protecting the walls from other agents of deterioration such as frost). We have carried out a year-long study of the influence that ivy canopies play on wall surface microclimates at five sites across a range of climatic settings within England, using iButtons to monitor temperature and relative humidity fluctuations at the wall surface on ivy-covered and exposed walls. Hourly data illustrates a general mediating effect of ivy canopies on both temperature and relative humidity regimes. The ivy reduces extremes of temperature and relative humidity, with the most clearcut differences for temperature. Across all five sites the average daily maximum temperature was 36% higher and the average daily minimum temperature 15% lower on exposed vs ivy-covered surfaces. Differences in the exposure level of studied walls (i.e. whether they are shaded or not by trees or other walls) influenced the degree of microclimatic alteration provided by the ivy canopy. Other important factors influencing the strength of the ivy impact on microclimate were found to be thickness of the canopy and aspect of the wall. A detailed analysis of one site, Byland in North Yorkshire, illustrates the seasonal differences in impact of ivy on microclimates, with insulation against freezing being the dominant effect in January, and the removal of high temperature ‘spikes’ the dominant effect in July. The observed moderating role of ivy canopies on wall surface microclimates will reduce the likelihood of frost and salt deterioration to the building materials, thus contributing to their conservation. Further research needs to be done on other potentially deteriorative roles of ivy before an overall bioprotective role can be assumed, but the significant impact of ivy on wall surface microclimates across England is clear.     

Assessment of the Health and Comfort Effects of Chemical Emissions from Building Materials: the State of the Art in the European Union*

Abstract The promotion of healthier indoor air requires the use of building materials whose chemical emissions are free of toxicity and unfavourable sensory properties. Testing and assessment of chemical emissions are essential in order to identify “safe” materials, and to encourage manufacturers to produce, and the market to adopt, such materials. Various testing and assessment procedures for building materials have been developed in European countries such as Germany, Denmark, Sweden, and Finland. Recently the European Collaborative Action “Indoor Air Quality and its Impact on Man” proposed criteria and a testing procedure for the assessment of VOC emissions from solid flooring materials. The innovative aspects of this proposal are: a procedure for the performance of chemical emissions testing; sensory testing coupled with toxicological evaluation; and a procedure to handle compounds for which toxicological information is scarce or absent. This procedure, after validation and experience from practical use, will probably be extended to other building materials.     

Associations of indoor carbon dioxide concentrations,air temperature,and humidity with perceived air quality and sick building syndrome symptoms in Chinese homes

The indoor environment influences occupants’ health. From March 1, 2018, to February 28, 2019, we continuously monitored indoor temperature (T), relative humidity (RH), and CO₂ concentration in bedrooms via an online system in 165 residences that covered all five climate zones of China. Meanwhile, we asked one specific occupant in each home to complete questionnaires about perceived air quality and sick building syndrome (SBS) symptoms at the end of each month. Higher CO₂ concentration was significantly associated with a higher percentage of perceived stuffy odor and skin SBS symptoms. Higher relative humidity was associated with higher percentage of perceived moldy odor and humid air, while lower RH was associated with a higher percentage of perceived dry air. Occupants who lived in residences with high RH were less likely to have mucosal and skin SBS symptoms (adjusted odds ratio (AOR): 0.73–0.78). However, the benefit of high humidity for perceived dry air and skin dryness symptoms is weaker if there is a high CO₂ concentration level.     

The effect of structures on indoor humidity--possibility to improve comfort and perceived air quality

The research presented in this paper shows that moisture transfer between indoor air and hygroscopic building structures can generally improve indoor humidity conditions. This is important because the literature shows that indoor humidity has a significant effect on occupant comfort, perceived air quality (PAQ), occupant health, building durability, material emissions, and energy consumption. Therefore, it appears possible to improve the quality of life of occupants when appropriately applying hygroscopic wood-based materials. The paper concentrates on the numerical investigation of a bedroom in a wooden building located in four European countries (Finland, Belgium, Germany, and Italy). The results show that moisture transfer between indoor air and the hygroscopic structure significantly reduces the peak indoor humidity. Based on correlations from the literature, which quantify the effect of temperature and humidity on comfort and PAQ for sedentary adults, hygroscopic structures can improve indoor comfort and air quality. In all the investigated climates, it is possible to improve the indoor conditions such that, as many as 10 more people of 100 are satisfied with the thermal comfort conditions (warm respiratory comfort) at the end of occupation. Similarly, the percent dissatisfied with PAQ can be 25% lower in the morning when permeable and hygroscopic structures are applied.     

Sensory pollution loads in six office buildings and a department store

Sensory pollution loads were measured in six non-smoking office buildings with mechanical ventilation without recirculation, and in a non-smoking department store with an air-conditioning system and recirculation. Untrained panels assessed the air quality on normal weekdays with occupants in the buildings, and in the case of office buildings, also on weekends without occupants present. On both occasions the ventilation system was in operation as on a normal working day. Outdoor airflow rate, air temperature, relative humidity and concentration of carbon dioxide were measured. The sensory pollution load from the building (without occupants) was found in offices to be 0.11 ± 0.09 olf/m² floor, which agrees well with the load recommended for low-polluting buildings in CEN CR 1752. This load is only half of the sensory pollution load found in previous investigations in offices and assembly halls where smoking was allowed. The load from building and merchandise in the department store was 0.15 olf/m² floor. A table is provided listing the mean sensory pollution load of the buildings measured in the present and in previous studies carried out in the period from 1988 to 2001 in different types of buildings in Europe. The table covers 120 buildings including offices and assembly halls (with and without previous smoking), schools, kindergartens and a department store.     

Optimizing CO2 emissions from heating and cooling and from the materials used in residential buildings,depending on their geometric characteristics

The objective of this research was to obtain the environmentally optimal design of a building with the following starting conditions: constant constructed surface, constant volume, square floor layout, and a variable number of floors. For this purpose, the study evaluated the impact of CO₂ emissions stemming from the energy needed to maintain the building at a constant temperature of 19 °C in winter and 25 °C in the summer. Furthermore, one of the results was the CO₂ emissions curve from the manufacturing of the materials used in the construction of the building and the building envelope.