Impact of ETICS on Corrosion Propagation of Concrete Facade

AbstractThe durability of reinforced concrete facades is an important field of research as the majority of dwellings in Northern and Eastern Europe were constructed 30–50 years ago. Recent condition assessments of the façades have indicated damage related to carbonation induced corrosion. Moreover, the problem might escalate since the future climate scenarios predict a significant increase of CO2 in ambient air being a driving force for carbonation.Assessment of residual service life of concrete facades is a complex phenomenon with a high level of uncertainty. A validated method used in this study combines dynamic hygrothermal simulation tool Delphin and existing corrosion models. Corrosion propagation consists of the time needed to concrete cover cracking and further expansion of a crack up to a width of 0.3mm as a limit criterion. Additional exterior thermal insulation (mostly ETICS) is applied to existing dwellings as a renovation scenario in order to decrease the heat loss, improve thermal comfort and prevent the degradation mechanism e.g. carbonation induced corrosion. Hence, reinforcement corrosion before and after installing ETICS with mineral wool, EPS or PIR has to be evaluated. Impact of boundary conditions, e.g. wind-driven rain in addition to material properties, and built-in moisture was included.The results indicate that corrosion propagation after carbonation has reached the reinforcement, is three to six years depending on the ratio of concrete cover depth against the reinforcement diameter. While applying ETICS, corrosion accelerates for a short period of time up to one year. Temperature inside the wall rises above +10°C throughout the year, meaning no more freeze-thaw damage. Corrosion of reinforcement in carbonated concrete after applying ETICS is so slow, that no cracking will develop. Drying out moisture or vapour diffusion from indoor air is not able to propagate corrosion of reinforcement in carbonated concrete

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

Renovation 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 to 34%, depending on the wall insulation thickness. We have also found that the relative percentage of thermal bridges after renovation increases and the negative impact of the thermal bridges of certain junctions cannot be compensated with thicker wall insulation. Results obtained in this paper are useful for energy audits. First published online: 13 Jun 201

Case-study analysis of concrete large-panel apartment building at pre- and post low-budget energy-renovation

The paper presents a case study analysis of low-budget renovation of a typical concrete large-panel apartment building. Focus is on the measurements and analyses of energy consumption, indoor climate, CO2 concentration, air leakage rate, thermal transmittance of thermal bridges, and thermal transmittance of the building envelope before and after the renovation. Results indicate that the renovation project was generally successful, with delivered energy need de­creasing by 40% and heating energy need decreasing by 50%. However, some key problems need to be solved to achieve full energy efficiency potential of the renovation works. Those critical problems are the performance (thermal comfort, heat recovery) of ventilation systems, thermal bridges of external wall/window jamb and economic viability. Currently, a major renovation is not economically viable, therefore financial assistance to the apartment owners’ associations is required to encourage them to undertake major renovations. First published online: 01 Jul 201

Rakennusten energialaskennan testivuosi 2012 ja arviot ilmastonmuutoksen vaikutuksista

Tiivistelmä Ilmaston lämpeneminen vaikuttaa rakennusten lämmitys- ja jäähdytysenergian tarpeeseen. Tässä tutkimuksessa muodostettiin rakennusten energialaskennassa Suomessa käytettävät uudet sääaineistot, tuotettiin ilmastoskenaarioiden avulla rakennusten energialaskelmiin soveltuvat tulevaisuuden sääaineistot ja arvioitiin rakennusten energiankulutusta vuoden 2030 muuttuneessa ilmastossa Rakennusten energialaskentaa varten kehitetty uusi testivuosi (TRY2012) korvaa aiemmin käytetyn testivuoden 1979. Uuden testivuoden tunnittaiset sääaineistot energialaskennan vyöhykkeillä I–II, III ja IV muodostettiin Vantaalla, Jyväskylässä ja Sodankylässä vuosina 1980–2009 tehtyjen säähavaintojen perusteella. Testivuoden kunkin kalenterikuukauden sääaineistot valittiin sellaiselta vuodelta, jonka aikana kyseisen kuukauden sääolot olivat mahdollisimman lähellä ilmastollista keskimääräistilaa. Käytännössä kalenterikuukausien valinta tehtiin tilastollisella menetelmällä tarkastellen lämpötilaa, kosteutta, auringon säteilyä ja tuulen nopeutta. Näitä neljää säämuuttujaa painotettiin sen mukaan, kuinka paljon ne vaikuttavat Suomessa rakennusten lämmitys- ja jäähdytystarpeeseen. Tyypilliselle uudispientalolle ja toimistorakennukselle tehdyt simuloinnit osoittivat, että lämmitys- ja jäähdytystarpeen kannalta tärkein säämuuttuja on ulkoilman lämpötila, mutta kesällä auringon säteilyn vaikutus on suunnilleen yhtä suuri. Tutkimuksessa arvioitiin myös ilmastonmuutoksen vaikutuksia. Ilmastomallien tulosten pohjalta laadittiin tilastollisilta ominaisuuksiltaan vuosien 2030, 2050 ja 2100 arvioitua ilmastoa vastaavat tulevaisuuden testivuosien sääaineistot. Vuoden 2030 tienoilla vuoden keskilämpötilan arvioidaan olevan paikkakunnasta riippuen 1,2–1,5 astetta korkeampi kuin TRY2012:n perusteella. Talvella keskilämpötila nousee noin kaksi astetta ja kesällä vajaan asteen. Lämpötilan vaihtelevuus pienenee talvipuolella vuotta noin 10 %. Auringon säteilyn väheneminen talvella ja keväällä, tuulen vähäinen voimistuminen marrashelmikuussa ja ilman suhteellisen kosteuden pieni kasvu loka–huhtikuussa otettiin myös huomioon tulevaisuuden testivuosia laadittaessa. Lopuksi arvioitiin ilmastonmuutoksen vaikutuksia rakennusten energiantarpeeseen nykyisiä rakentamismääräyksiä noudatettaessa. Laskelmissa esimerkkinä käytetyn pientalon tilojen ja ilmanvaihdon lämmitystarve vähenee vuoteen 2030 mennessä noin 10 % ja jäähdytystarve kasvaa 17–19%. Toimistotalon lämmitystarve on vastaavasti 13% pienempi ja jäähdytystarve 13-15 % suurempi kuin nykyisessä ilmastossa. Kaikkiaan rakennusten kokonaisostoenergiankulutus vähenee vuoteen 2030 mennessä 4–7 % ilmaston muuttumisen takia.Abstract: The ongoing climate change is expected to affect the energy demand for heating and cooling of buildings. Building energy consumption is often assessed by simulation algorithms that require hourly meteorological data. For this purpose, weather observations from the year 1979 have previously been used in Finland as a reference. Here, we describe a new test reference year, TRY2012, that was constructed by using weather observations at three measurement stations (Vantaa, Jyväskylä and Sodankylä) during 1980–2009. TRY2012 consists of weather data for twelve months that originate from different calendar years, each month having weather conditions close to the long-term climatological average. The months for TRY2012 were selected using Finkelstein-Schafer parameters for four climatic variables (air temperature, humidity, solar radiation and wind speed); these parameters were weighted depending on how important individual climatic variables are for the building energy consumption in Finland. Calculations for two example buildings, a detached house and an office building, indicate that the most influential climatic variable for annual energy demand is air temperature. In summer, solar radiation and air temperature are of broadly equal influence. We also assessed the influence of human-induced climate change on typical weather conditions for the years 2030, 2050 and 2100. Multi-model mean estimates from 7 to 19 global climate models, together with the TRY2012 weather data, were used to construct artificial meteorological data for the future. The projected reference year TRY2030 is 1.2–1.5ºC warmer than TRY2012, with the lower end of the range corresponding to Vantaa in southern Finland and the higher value to Sodankylä in the north. Seasonal mean temperature is projected to increase by about two degrees in winter and by slightly less than one degree in summer. The variability in temperature will diminish in the winter half of the year by about 10 %. In addition, the projections include decreases in solar radiation in winter and spring, slight increases in wind speed in November-February, and small rises in relative air humidity in all seasons except summer. Utilizing the reference years TRY2012 and TRY2030, we calculated the mean monthly and annual energy consumption for the two example buildings in the current and projected future climate. Based on the simulations, the heat energy consumption of spaces and ventilation will decrease by 10% for the detached house and by 10–13% for the office building, whereas space cooling electricity will increase by 17–19% for the detached house and by 13–15% for the office building. Because electricity for cooling relative to the total delivered energy is minor, the total energy consumption of the example buildings is projected to decrease by 4–7% by 2030

Indoor hygrothermal loads for the deterministic and stochastic design of the building envelope for dwellings in cold climates

In this study, several years of field measurements of indoor hygrothermal loads in 237 dwelling units are analysed. Moisture excess is calculated from hourly values of temperature, and relative humidity measured both indoors and outdoors. Air change rate and moisture production in bedrooms are calculated on the basis of carbon dioxide measurements. It is found that indoor temperature profiles differ depending on whether a building has central heating, a stove or combined heating system. The determined average moisture excess value, 2.8 g/m3 with a standard deviation of 1.6 g/m3 for cold periods, can be used in stochastic calculations. Critical values for moisture excess at the 90th percentile, ranging from 3–8 g/m3, depending upon occupancy rates, can be used in the deterministic analysis. Averages and weekly maxima of moisture excess in the study are reported at different percentiles. Considerable deviations from the EN ISO 13788 standard are discovered, concerning the breaking point depending on outdoor temperature and moisture excess during the summer. The average and critical moisture production in bedroom is presented and insufficient ventilation determined based on measurements. During the heating period, the air change rate is relatively stable while moisture production levels increase along with the dropping outdoor temperature. Two indoor temperatures and three humidity models with different levels of detail and influencing factors are proposed. Temperature and humidity loads derived using the proposed models can be used to determine the indoor hygrothermal boundary conditions for the building envelope of dwellings in cold climates.acceptedVersionPeer reviewe

Indoor climate loads for dwellings in different cold climates to assess hygrothermal performance of building envelopes

This study tests the performance of an EN ISO 13788 occupancy modified model for indoor temperature and humidity in dwellings by comparing the model to the measured indoor temperature and relative humidity in Canada. The performance of EN ISO 13788 occupancy modified model is tested in 13 outdoor climates and compared to the simplified approach given in the ASHRAE 160 standard. It was found that the Estonian modelâ s proposed indoor temperature profile works reasonably well in accordance with the measured indoor temperatures in Vancouver, Canada, which are dependent on outdoor climate; on the other hand, the ASHRAE 160 indoor temperature profile might not be the best for cold climates. Drawbacks were noted concerning the humidity loads given as a simplified approach in the ASHRAE 160 with the suggestions for the possible future renewal. A new approach for selecting the indoor humidity load for dwellings in cold climates is proposed.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

A method to develop energy activated ETICS

We propose a method for developing an Energy Activated External Thermal Insulation Composite System (En-ActivETICS) for smart building envelopes that guarantees the required performance, durability, and service life of the building. The En-ActivETICS combines the traditional ETICS with phase change material (PCM) and flexible photovoltaics (FPV). These combined materials will become multifunctional, playing the roles of thermal insulator, heat accumulator, and energy generator with PCM lowering the temperature of FPV and therefore, increasing their efficiency. The En-ActivETICS is a new step in the development of building facade technology enabling to achieve a component that is classified as a functional material. The main result reported in the paper is the proposed method, which improves the existing technical approval guidelines for ETICS, entitled ETAG 004, when thermally activated components are added to the system. The method proposes research activities necessary to determine whether the novel wall system is in line with the essential requirements set to a building by the Construction Products Regulation. When tested according to the proposed method, a wall system should be comprehensively tested and technically documented active thermal insulation system that is aimed to give better building performance in terms of indoor environment, energy efficiency, and aesthetics