Jari Palonen’s research while affiliated with University of Helsinki and other places

Aims: The aim was to study health and academic performance of school children and indoor environmental quality in Finnish elementary schools. Study design: Cross-sectional study. Place and Duration of Study: Data were collected between March 2007 and April 2008. Methodology: As a part of a national testing program, all sixth grade students in a random sample of 334 schools were tested for mathematics. Health questionnaires were administered for the same students. Data from school buildings were collected by questionnaires from school principals. Additional data were collected by on-site-inspections and measurements from a sub-sample of schools. The resulting database comprises of multi-level information on elementary schools, and student health and learning outcomes. Results: After adjusting for student background variables, those who had never experienced high indoor temperatures in classrooms had 4.0% (95%CI 0.4-7.4) higher percentage of correct answers than those who experienced it daily. Students who did not miss school days due to respiratory infections had 1.1% (95% CI 0.1-2.2%) higher percentage of correct answers in math test than those who had not. Other significant associations were observed between math achievement and both headache and difficulties in concentration. Conclusion: Math achievement was associated with missed school days due to respiratory infections, headache and difficulties in concentration, and indoor temperatures perceived too high in the classroom. In the future, more detailed analyses are needed to assess the role of these health symptoms in relation to the effects of classroom IEQ on learning outcomes.

The effects of reduced summer indoor temperature, through renovation of an HVAC system, on symptoms, perceived environment and productivity in an office building are investigated. Measurements of indoor parameters, perceived environment and productivity were conducted over two successive summers. Two floors of the office building were renovated during the wintertime. The renovation mainly consisted of cooling the supply air, installation of cooling ceilings in about half of the office rooms, and distributing supply air to all office rooms. An indoor air questionnaire assessing current symptom intensity, including questions on self-estimated work efficiency, was presented to employees on five days each summer. The measurements taken during the summer before the renovation showed that indoor temperatures rose above thermal comfort levels (maximum temperature 31.4°C). When the temperature rose above 25°C, neurobehavioural symptoms and the percentage of those dissatisfied with the indoor air quality increased, and self-estimated work efficiency decreased statistically significantly. After the renovation, thermal indoor comfort was achieved, and the percentage dissatisfied with the temperature and indoor air quality remained at a low level, i.e. 2–4 per cent. Objective productivity measurements conducted with a few employees performing solo work showed a 4.4 per cent improvement of work efficiency in the summertime.

This paper focuses on classroom ventilation. We investigated schools and their ventilation systems, and measured ventilation rates in spring and summer 2007 from a total of 60 schools (108 classrooms) in Southern Finland. The oldest schools were built in the beginning of 1900's and the newest were built in the last 10 years. Some 10 percent of ventilation systems were still in their original state, and almost 15 percent of schools had passive stack ventilation. Substantial variation was observed in the ventilation rates per student and per floor area. Air flow rates per floor area were between 0.4 and 5 l/s per m 2. The median value was 2.0 l/s per m2. Air flow rates per student were between 1-20 l/s per student. The median value was 4 l/s per student.

Unlabelled: In this study, we simulated and measured the effect of permeable and hygroscopic lightweight structures on indoor air quality (IAQ) and thermal comfort in a cold climate. The potential effect of hygroscopic mass was assessed with the simulation of extreme cases, where permeable and hygroscopic lightweight structures with unfinished surfaces were compared with impermeable and non-hygroscopic ones. Measurements were conducted in 78 rooms of 46 newly built detached timber-framed houses and analyzed according to hygroscopic surface materials and envelope permeability. From the simulations, it was shown that permeable and hygroscopic structures considerably improved perceived air quality in summer, when a ventilation rate of 6 l/s pers. in the non-hygroscopic case corresponded roughly to 4 l/s pers. in the hygroscopic case. However, window airing and furnishing will reduce this difference in practice. Both simulated and measured results showed that permeable and hygroscopic structures significantly reduced peak indoor relative humidity levels and daily changes in relative humidity, but had no long-term effects. Measured results also indicated that completely non-hygroscopic houses did not exist in reality. Practical implications: 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.

Two similar blocks of flats for people with respiratory illnesses were built in the year 2000 and followed during years 2001-2005. The buildings have clean and effective ventilation system and low emitting building materials. The buildings have centralized supply and exhaust air system, either demand or user controlled. The results showed the benefits of demand controlled ventilation compared with user controlled because in the latter case occupants do not adjust ventilation as much as expected. The design process of demand controlled ventilation in apartment buildings is much more complicated and has more risk to fail than conventional ventilation systems.

Unlabelled: Urban PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 microm) is associated with excess mortality and other health effects. Stationary sources are regulated and considerable effort is being put into developing low-pollution vehicles and environment-friendly transportation systems. While waiting for technological breakthroughs in emission controls, the current work assesses the exposure reductions achievable by a complementary means: efficient filtration of supply air in buildings. For this purpose infiltration factors for buildings of different ages are quantified using Exposures of Adult Urban Populations in Europe Study (EXPOLIS) measurements of indoor and outdoor concentrations in a population-based probability sample of residential and occupational buildings in Helsinki, Finland. These are entered as inputs into an evaluated simulation model to compare exposures in the current scenario with an alternative scenario, where the distribution of ambient PM2.5 infiltration factors in all residential and occupational buildings are assumed to be similar to the subset of existing occupational buildings using supply air filters. In the alternative scenario exposures to ambient PM2.5 were reduced by 27%. Compared with source controls, a significant additional benefit is that infiltration affects particles from all outdoor sources. The large fraction of time spent indoors makes the reduction larger than what probably can be achieved by local transport policies or other emission controls in the near future. Practical implications: 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 1.1W/m2K 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.

A mass-balance model, as well as data on particle-size distributions, filter efficiencies, and particle-deposition rates were used to estimate reductions in indoor concentrations of different particle types attainable with the use of filters in HVAC supply-air streams. In addition, the energy and total costs of various filtration options were estimated. The resultant data were analyzed in detail.