Mihkel Kiviste

Indoor thermal environment, air exchange rates, and carbon dioxide concentrations before and after energy retro fits in Finnish and Lithuanian multi-family buildings

Impacts of energy retrofits on indoor thermal environment, i.e. temperature (T) and relative humidity (RH), as well as ventilation rates and carbon dioxide (CO2) concentrations, were assessed in 46 Finnish and 20 Lithuanian multi-family buildings, including 39 retrofitted case buildings in Finland and 15 in Lithuania (the remaining buildings were control buildings with no retrofits). In the Finnish buildings, high indoor T along with low RH levels was commonly observed both before and after the retrofits. Ventilation rates (l/s per person) were higher after the retrofits in buildings with mechanical exhaust ventilation than the corresponding values before the retrofits. Measured CO2 levels were low in vast majority of buildings. In Lithuania, average indoor T levels were low before the retrofits and there was a significant increase in the average T after the retrofits. In addition, average ventilation rate was lower and CO2 levels were higher after the retrofits in the case buildings (N=15), both in apartments with natural and mixed ventilation. Based on the results, assessment of thermal conditions and ventilation rates after energy retrofits is crucial for optimal indoor environmental quality and energy use.

Effect of massive outer leaf of an insulated cavity brick wall on heat loss

The availability of coherent long-term measured data on climatic variables and building parameters forms the basis for predicting, analyzing, and simulating the heating or cooling energy demand on buildings. This article analyzes measured 4-year data considering the test building with an insulated cavity brick wall with a massive outer brick leaf. The results show that the solar radiation and the thermal inertia of massive outer leaf of a wall have a significant effect on the heat loss and energy consumption of the buildings throughout Finland and Scandinavia. Based on the average outdoor air temperatures, the nominal calculated heat losses could be overestimated. For more accurate heat losses, the outdoor surface temperature should be applied as a boundary condition. The measured results were verified with finite element method.

Analysis of hygrothermal parameters in Finnish and Lithuanian multi-family buildings before and after energy retrofits:

This study focuses on analyzing temperature- and moisture-related parameters based on data from 45 Finnish and 20 Lithuanian multi-family buildings. The data consist of two rounds of 2-month data-logging (1-h interval) of indoor temperature and relative humidity at two locations: one representing average occupied zone and the other one nearby the coldest spot of the building envelope. Between the two rounds of data-logging, 37 buildings from Finland and 15 buildings from Lithuania underwent retrofits, aiming to improve their energy efficiency. Measurement data were coupled with outdoor data from national weather stations, based on which a temperature factor (fc) and excess indoor moisture content (Δv) were calculated. Based on the results, fc was significantly higher in Lithuanian case buildings after the retrofits, whereas no significant differences were observed in Finnish buildings. In addition, Δv was significantly lower in Finnish case buildings after retrofits, whereas an opposite trend was seen in the Lithuanian buildings.

Occupant satisfaction with indoor environmental quality and health after energy retrofits of multi-family buildings: Results from INSULAtE-project

BACKGROUND Driven by climate change mitigation, EU countries are committed to improve energy efficiency of their building stock by implementing the energy performance of buildings directive (EPBD). Should higher energy efficiency result in better indoor environmental quality (IEQ), this policy could also be seen as an opportunity to improve public health across Europe. OBJECTIVES This paper focuses on the assessment of the effects of energy retrofits on occupant satisfaction with IEQ and health in multifamily buildings. METHODS Data on occupant satisfaction with IEQ and health were collected from the occupants of 39 Finnish and 15 Lithuanian multifamily buildings (an average of five apartments per building, one adult per apartment) both before and after energy retrofits (such as improving thermal insulation, windows, heating and/or ventilation systems). Parallel to the data collected from the occupants, data on several IEQ parameters, including temperature, temperature factor, and air change rate, were collected from their apartments. Moreover, data from seven Finnish and five Lithuanian non-retrofitted control buildings were collected according to the same protocol. RESULTS Occupant satisfaction regarding indoor temperature was associated with both retrofit status (OR 5.3, 95% CI 2.6-11.0) and measured IEQ parameters (indoor temperature OR 1.4 per 1 °C increase, temperature factor OR 1.1 per 1% increase, and air change rate OR 5.6 per 1/h increase). Additional positive associations were found between retrofit status and occupants reporting absence of upper respiratory symptoms (OR 1.8, 95% CI 1.1-2.9) as well as not missing work or school due to respiratory infections (OR 4.1, 95% CI 1.2-13.8), however, these associations were independent of the measured IEQ parameters. CONCLUSIONS There seems to be a strong subjective component related to the observed changes in occupant satisfaction with IEQ and health as a result of energy retrofitting in buildings. Further studies are needed to verify the actual mechanisms, as well as possible long term effects.

Internal moisture excess of residential buildings in Finland

In Finland, the indoor air conditions of 171 single-family buildings and 49 apartments in multi-family buildings have been studied in large research projects in collaboration with Tampere University of Technology and Helsinki University of Technology. This article deals with the results of moisture excess studied in these single-family buildings and apartments. Continuous field measurements up to 28 months enable to include two consecutive heating seasons in the analysis of the internal moisture excess. The higher 10% critical level during the cold period (Te ≤ 5°C) was between 3.4 and 4.9 g/m3 in Finnish heavyweight and lightweight single-family buildings and between 2.4 and 3.6 g/m3 in apartments of multi-family buildings. During the warm period (Te ≥ 15°C), the corresponding values were between 0.3 and 2.6 g/m3 for single-family buildings and 0.5 and 1.5 g/m3 for apartments. The number of occupants and the airtightness of different groups of external wall did not have influence on the average values of moisture excess. Slightly better ventilation air change rates were measured in apartments of multi-family buildings, where also the air change rates from supply–exhaust ventilation systems generally fulfilled the Finnish guideline value. The design values of moisture classes in EN ISO 13788:2012 were found difficult to apply for Finnish residential buildings. The upper limit value of humidity class 2 of EN ISO 13788:2012 is suitable for apartments in Finnish multi-family buildings, but too low for Finnish lightweight and heavyweight single-family buildings. Applying the design values of Finnish guidelines would be justified for the studied buildings almost at the full range of outdoor temperatures.