This paper predicts the reductions in the indoor mass concentrations of particles attainable from use of filters in building supply airstreams and also from use of stand-alone fan-filter units. Filters with a wide efficiency range are considered. Predicted concentration reductions are provided for indoor-generated particles containing dust-mite and cat allergen, for environmental tobacco smoke (ETS) particles, and for outdoor air fine-mode particles. Additionally, this paper uses a simple model and available data to estimate the energy and total costs of the filtration options. Predicted reductions in cat and dust-mite allergen concentrations range from 20 to 80%. To obtain substantial, e.g. 50%, reductions in indoor concentrations of these allergens, the rate of airflow through the filter must be at least a few indoor volumes per hour. Increasing filter efficiencies above approximately ASHRAE Dust Spot 65% does not significantly reduce predicted indoor concentrations of these allergens. For ETS particles and outdoor fine-mode particles, calculations indicate that relatively large, e.g. 80%, decreases in indoor concentrations are attainable with practical filter efficiencies and flow rates. Increasing the filter efficiency above ASHRAE 85% results in only modest predicted incremental decreases in indoor concentration. Energy costs and total costs can be similar for filtration using filters with a wide range of efficiency ratings. Total estimated filtration costs of approximately $0.70 to $1.80 per person per month are insignificant relative to salaries, rent, or health insurance costs.
It has been suggested that indoor concentrations of ambient particles and the associated health risks can be reduced by using mechanical ventilation systems with supply air filtering in buildings. The current work quantifies the effects of these concentration reductions on population exposures using population-based data from Helsinki and an exposure model. The estimated exposure reductions suggest that correctly defined building codes may reduce annual premature mortality by hundreds in Finland and by tens of thousands in the developed world altogether.
This study defined, derived and calculated the efficiency of electrical energy use in electrically heated windows which may be used for improving thermal comfort near glazing. In a cold climate, a warm glass surface is a unique possibility for thermal conditioning. The effects of surface and outdoor temperatures and the U-value of the window on the efficiency of a heated window were analyzed. The calculated results were compared to previously measured ones. The efficiency of a common heated window with a U-value of 1.1 W/m 2 K was about 78% at an outdoor temperature of −10 • C. The highest efficiency of 89% was calculated for a highly insulated window. Efficiency was proportional to the outdoor temperature and practically independent of the inner surface temperature of the window, the effect of which was less than 1%. The correlation of the calculated efficiencies shows that efficiency is primarily dependent on the U-value of the unheated window and can be expressed with very good accuracy for engineering purposes by a simple linear equation of the U-value. The results show that heated glazing is an efficient method for thermal conditioning when properly used.
Limited knowledge is available about building envelope and ventilation system interactions with consequent effects on indoor climate. To take such effects adequately into account in design and construction of buildings, solid scientific data explaining the significance of the phenomena studied are needed. We have demonstrated that moisture exchange has evidently enough importance to be taken into account in future building simulation tools.
The objective of this study was to assess the effect of air humidification and temperature on thermal comfort in sedentary office work. A blinded twelve‐period cross‐over trial was carried out in two similar wings of an office building, contrasting 28–39% steam humidification with no humidification, corresponding to 12–28% relative humidity. The length of each period was one working week. The study population was 169 workers who judged their thermal sensations in a weekly questionnaire. The percentage of dissatisfied was lowest when the air temperature was 22 °C. At 22 °C an increase in relative humidity raised the mean thermal sensation only slightly. At 20 °C when the air was humidified there were fewer workers who judged their air temperature as being too low. On the other hand, at 24 °C humidification increased the percentage of workers who judged their air temperature to be too high. The percentage of dissatisfied increased rapidly when the air temperature was outside of its optimum value, 22 °C. The percentage of workers complaining about draft increased when the air temperature was lower than 22 °C. Thus we consider that the temperature range from 20 to 24 °C during wintertime may be too wide without individual temperature control from the point vzew of thermal comfort. We recommend that the air temperature should be kept between 21 and 23 °C if no individual control is available. The best solution would be individual temperature control permitting adjustment of the temperature at 22 ± 2 °C.
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