Endrik Arumägi

Hygrothermal performance of internally insulated brick wall in cold climate: A case study in a historical school building

Interior thermal insulation is frequently one of the only possible solutions for thermal upgrade of the building envelope where the external appearance cannot be changed. In this study, four insulation materials were used in a case study in a historical school building in in situ test walls. The indoor climate in the test room was controlled to simulate the typical dwelling with high moisture load. The temperatures, relative humidity, and heat flows were monitored over 9 months to analyze the hygrothermal performance of four different insulation materials. The hygrothermal performance of insulation materials during drying and wetting periods are presented. Moisture test reference year was used in working out possible energy-renovation solutions. The results show that timing of the renovation works is a matter of consideration to avoid the hygrothermal risks inside the renovated wall assemblies. The results show that in all the cases, thermal comfort can be improved by increasing the inner surface temperature and decreasing thermal conductivity. However, in some cases, the risks of mold growth and interstitial condensation were present inside the retrofitted wall assemblies. Computer simulations of the wall assemblies with moisture reference years under different humidity loads concluded that all solutions are suitable for future analysis.

The Influence of Indoor Climate Control on Risk for Damages in Naturally Ventilated Historic Churches in Cold Climate

ABSTRACT This article analyzes the indoor climate that creates risk of damages in naturally ventilated churches in the cold climate of Estonia. Indoor temperature and humidity were measured over a one-year period and the results were analyzed on the basis of damage functions: mold growth, risk of cracking and fracturing of wooden objects, and delamination of the gesso layer of panel paintings. In unheated churches, one of the most dominant problems was very high relative humidity throughout the year, creating a high risk for mold and algae growth. Churches may need background heating to avoid freezing during a long cold winter that causes low surface temperatures of massive walls during the spring–summer period. It was found that mold risk was significantly lower in heated churches than in unheated or intermittently heated churches. The risk of mold growth was not decreased by the use of intermittent heating. In heated churches, overheating (room temperature >+10ºC) causes a RH below 50% during cold periods, and the favorable period for irreversible response of panel paintings was significantly longer, so there is a higher risk that the gesso may crack or delaminate. From the point of view of the cracking and fracturing of wood, indoor climate conditions are in the safe range for most of the year.

Impact of linear thermal bridges on thermal transmittance of renovated apartment buildings

AbstractRenovation of old apartment buildings is a topic of current research interest throughout the Eastern Europe region where similar typology is derived from the period of 1960–1990. Thermal bridges, essential components of the transmission heat loss of a building, have to be properly evaluated in the energy audit during current state-of-the-art situation as well as in the comparison of renovation solutions. Resulting from field measurements and calculations, we propose linear thermal transmittances Ψ of thermal bridges for four types of apartment buildings: prefabricated concrete large panel element, brick, wood (log), and autoclaved aerated concrete. Our results show that thermal bridges contribute 23% of the total transmission heat loss of a building envelope before renovation. After renovation thermal bridges account for only 10% if windows are repositioned into additional external thermal insulation and balconies are rebuilt as best practice. Inversely, impact of the thermal bridges might be up t...

Airtightness, Air Exchange and Energy Performance in Historic Residential Buildings with Different Structures

Abstract Old buildings that represent and maintain historic values often have poor indoor conditions and energy efficiency. The aim of this work was to evaluate the influence of building structures on airtightness and energy performance of certain historic building types. In this study on-site measurements, dynamic simulation and questionnaires were used. Significant differences between the levels of the airtightness of the historic houses exist in the studied region. No statistically significant correlation was found between the structure types and the envelope tightness. The typical air leakage places of the studied houses were at the junctions of the envelope structures. Measured air exchange rates indicated that the level of ventilation is insufficient in some of the houses while some are too leaky. If the airtightness of the naturally ventilated house is improved, the acceptable ventilation rate has to be guaranteed. Tightening the envelope and moving from natural to mechanical ventilation was the most effective way to improve the indoor conditions and energy performance.

Design of the first net-zero energy buildings in Estonia

In Estonia, comprehensive regulation establishes the methods for calculating the indoor climate and energy performance of buildings to prove their compliance with minimum requirements. The definition of a nearly zero-energy building and a net-zero energy building, and the methodology for the calculation of the energy performance of the buildings in Estonia are explained. The problems and results of the design process of the first zero-energy building in Estonia are described through a case study. The current study showed that it is possible to reach zero-energy building levels in Estonia by careful and detailed designs of the energy performance of a building. More thorough analyses are needed in the very first stage of the design to find suitable solutions and possible compromises between architecture and energy efficiency. In any case, well-insulated buildings, effective building service systems, and local electricity production on-site is needed for zero-energy building. Finally this article discusses the problems and limitations of the regulations influencing the motivation and actions needed to achieve zero-energy buildings. The study shows the influence of the different parts of the building on the balance of the energy consumption and utilization, and on the energy performance of the building to achieve zero-energy building status.

Indoor hygrothermal condition and user satisfaction in naturally ventilated historic houses in temperate humid continental climate around the Baltic Sea

Indoor climate and user satisfaction were analysed by field measurement and a questionnaire in 67 traditional rural houses in Estonia, Finland and Sweden. Our findings showed that the indoor climate in all the investigated historic rural houses needs improvement. The room temperature was mainly too low during winter. Leaky houses had also a larger vertical temperature difference. The relative humidity in the unheated and periodically heated houses was high during winter and caused risk for mould growth in 17% of all houses and 33% of unheated houses. Significant differences of indoor humidity loads in different houses were revealed depending on the living density and usage profile. During the winter period, the design value of moisture excess was 4–5 g/m3 and the average moisture load was 2–3.5 g/m3. The indoor humidity load in historic houses was similar to that in modern houses. The results of the questionnaire showed that main problems were related to unstable or too low temperatures. At the same time, inhabitants rated the overall indoor climate as healthy and no statistically important relations were found between average indoor temperature and complaints about too cold or too warm indoor temperatures.

Cost-Effective Energy and Indoor Climate Renovation of Estonian Residential Buildings

Renovation of the existing residential building stock is a key factor in the future of building energy savings in Estonia, as the replacement rate of existing stock is only 1–2% per year. This research analyses the energy-efficiency and economic viability of the energy renovation of dwellings. Individual energy-saving measures and renovation packages were composed for reference buildings to analyze cost-optimal energy-efficiency levels. The research uses the methods of large-scale field studies as well as computer simulations to analyze the energy performance of dwellings in Estonia.