Browsing by Author "Velashjerdi Farahani, Azin"

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Adapting Nordic Buildings for Enhanced Summertime Resilience in the Face of Climate Change
(2024) Velashjerdi Farahani, Azin
School of Engineering | Doctoral dissertation (article-based)
In the face of escalating climate change impacts, understanding the resilience of buildings to extreme weather events, particularly in cold climates, is crucial for mitigating risks to human thermal comfort and well-being. This thesis addresses this issue by investigating the resilience of different buildings to climate change and its associated hot summers in Nordic climates. Through a combination of field measurements and simulation studies, the research assesses indoor overheating risks, energy consumption, and power demand in different building types, while also exploring the relationship between indoor and outdoor temperatures during heatwaves. The findings reveal significant challenges posed by high overheating risks in residential buildings, particularly in older ones in comparison to the newer ones designed based on the latest building codes. The study highlighted the effectiveness of passive strategies in mitigating risks. However, results showed that there is a need for mechanical cooling systems in residential buildings to ensure comfortable and healthy indoor temperatures during current and future heat events. The needed cooling electricity was shown to be considerably small compared to other energy consumptions in the buildings. Additionally, the study identifies strong correlations between indoor and outdoor temperatures during the hot summers that weakened during the prolonged heatwaves. This highlights the complex and dynamic nature of these relationships under different environmental conditions and emphasizes the importance of considering extreme heat events in the design and operation of buildings in cold climates. In office buildings, all-air and air-water systems were found to perform equally in terms of cooling energy consumption and indoor temperature conditions under a changing climate. While the maximum cooling power demand would be higher with the all-air system (ventilative) during extreme weather conditions. However, the cooling electricity increased up to 47% in the future average climate and up to 128% in the future extreme climate with the air-water system, and up to 51% in the future average climate and 108% in the future extreme climate with the all-air system by 2050 depending on the CO2 emission scenario.
Dimensioning of the cooling system in Finnish office buildings using the new cooling design days for the current and future climates
(2022) Velashjerdi Farahani, Azin; Jokisalo, Juha; Lestinen, Sami; Korhonen, Natalia; Jylhä, Kirsti; Kosonen, Risto
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This study aimed to investigate the dimensioning cooling power demand in the current and future climate in office buildings, using the new cooling design days for Finland. The results showed that, depending on future climate scenarios, the dimensioning cooling power demand will increase by about 5–13% and 7–17% with the air-water and all-air system, respectively.
DIMENSIONING OF THE COOLING SYSTEM IN FINNISH OFFICE BUILDINGS USING THE NEW COOLING DESIGN DAYS FOR THE CURRENT AND FUTURE CLIMATES
(2022-03-15) Velashjerdi Farahani, Azin; Jokisalo, Juha; Lestinen, Sami; Korhonen, Natalia; Jylhä, Kirsti; Kosonen, Risto
A4 Artikkeli konferenssijulkaisussa
This study aimed to investigate the dimensioning cooling power demand in the current and future climate in office buildings, using the new cooling design days for Finland, which have been chosen using SFS-EN ISO 15927-2 standard. Therefore, two cooling systems, the all-air, and the air-water are compared in size and performance for the new design days with a 1% risk level in the current climate and future scenarios. The dimensioning of radiant cooling panels for the air-water system and the airflow rates for the all-air system are conducted. Moreover, the dimensioning cooling power demands are compared to the peak cooling power demand for the whole summer using TRY 2012. The results showed that depending on future climate scenarios, the dimensioning cooling power demand will increase by about 5-13% and 7-17% with the air-water and all-air systems, respectively.
The effect of local thermal sensation on overall thermal sensation in older people under warm conditions: a chamber room study
(2022-08-31) Chen, Minzhou; Velashjerdi Farahani, Azin; Kosonen, Risto; Kilpeläinen, Simo; Lestinen, Sami
A4 Artikkeli konferenssijulkaisussa
Global aging and climate warming have made scholars begin to pay attention to the thermal comfort of the elderly. The deterioration of the function of body organs and systems caused by aging affects the thermoregulatory system of the elderly, resulting in a narrowing of their thermoregulatory range. To ensure their thermal comfort, personalised thermal comfort systems can be used, for example. When designing a system or selecting equipment, the impact of local thermal sensation on the overall thermal sensation needs to be considered. Most of the existing studies are based on young people, however, the local thermal sensation of the elderly may not be consistent with that of the young. This study recruited 26 Finnish older adults to conduct a series of human thermal comfort experiments under warm conditions in a climate chamber. The local and overall thermal sensations of the elderly were analyzed, and the weights of the influence of different parts on the overall thermal sensation of the elderly were obtained. The study found that the head and torso had a greater impact on the overall thermal sensation in a warm environment.
Huonelämpötilan pysyvyys ja aktiivisen jäähdytyksen tarve tulevaisuuden ilmastossa
(2021) Kosonen, Risto; Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Jylhä, Kirsti
A4 Artikkeli konferenssijulkaisussa
Tämän tutkimuksen tavoitteena on laskennallisesti selvittää, kuinka asuinkerrostalossa huonelämpötila ja jäähdytyksen tarve muuttuvat tulevaisuuden ilmastossa. Tutkimuksessa analysoitiin uusien ja 60- luvun asuinkerrostalojen lämpenemistä nykyisessä (TRY2020) ja tulevaisuuden ilmastossa (TRY2050). Lisäksi tutkittiin vuoden 2018 erityisen lämpimän hellekesän (HWS2018) ja siihen pohjautuvan ennustetun tulevaisuuden hellekesän (HWS2050) merkitystä asuinrakennuksien ylilämpenemiseen. Tutkimuksessa selvitettiin lisäksi olohuoneeseen asennetun jäähdyttävän ilmalämpöpumpun tehokkuutta ja energiankulutusta sekä nykyisissä että tulevaisuuden ilmasto-oloissa. Tulokset osoittavat, että uuden rakennuksen maksimilämpötila oli alhaisempi kuin vanhojen rakennuksien johtuen pienemmästä ikkuna-alasta ja paremmasta aurinkosuojauksesta. Nykyilmastossa uusien ja vanhojen rakennuksien maksimilämpötilat olivat noin 32 oC ja 35 oC. Sen sijaan keskimäärin kesäkaudella uuden rakennuksen lämpötila on korkeampi kuin vanhassa rakennuksessa. Hellekesän 2018 aikana tutkittujen rakennusten maksimilämpötilat nousivat jopa 35-38 oC:een. Tulevaisuuden ilmastossa (TRY2050 ja HWS2050) huonelämpötilat nousevat tästä vielä noin 1 oC:lla niin normaalikesän kuin hellekesän arvoihin nähden. Olohuoneeseen asennettu ilmalämpöpumppu on ainoa tutkittu ratkaisu, jolla voidaan pitää kaikkien huoneiden lämpötila alle 26-27 oC sekä nykyisessä että vuoden 2050 ennustetussa ilmastossa. Koneellinen jäähdytys lisää sähköenergian kulutusta tutkituissa kohteissa enimmillään vain 4 kWh/m2,a.
Intelligent building envelope solutions in Finnish new and old apartment buildings
(2022-05-22) Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Jylhä, Kirsti; Ihasalo, Heikki; Ketomäki, Jaakko; Kosonen, Risto
A4 Artikkeli konferenssijulkaisussa
This study investigated the effects of intelligent building envelope solutions (automated blinds, openable windows, and awnings as well as electrochromic windows) in Finnish old and new apartment buildings. Moreover, the results are compared to the passive solutions (manual blinds and solar protection windows). The main goal was to compare the performance of each solution in improving the indoor temperature conditions in Finland’s current climate. Thus, the solutions were simulated with the usage of a mechanical cooling system in the living room to see the effects on both the energy demand of the buildings and indoor temperature conditions in the warmest bedroom. Furthermore, indoor temperature conditions were analyzed in the warmest bedroom of the new building without an active cooling system, as well. According to the results, electrochromic and solar protection windows are the solutions with the lowest cooling electricity consumption in the old building. However, in the new building, the lowest cooling electricity consumption is for the case with the automated openable windows and the next effective solutions are solar protection and electrochromic windows. Considering the results of indoor temperature conditions, the combination of solar protection windows and manual blinds is the most effective solution in the old building. While automated openable windows have the best performance in the new building with or without the active cooling system. Overall, passive solutions are more effective in both the old and new apartment buildings except for automated openable windows in the new building.
OVERHEATING RISK OF APARTMENTS IN THE HELSINKI REGION DURING THE HOT SUMMER OF 2021
(2023) Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Jylhä, Kirsti; Kosonen, Risto
A4 Artikkeli konferenssijulkaisussa
During heat waves, room air temperatures without cooling can raise health risk levels. Therefore, it is important to study the actual room air temperatures in residential buildings during hot summers. In this study, the hourly indoor temperatures of 6057 apartments during the hot summer of 2021 were measured and analyzed in the Helsinki region. These apartments are different in size and age. The results showed that the indoor temperature in 96% of the apartments exceeded 27 C,, 34% exceeded 30 C, and around 5% of them exceeded 32 C. The results showed a significantly high risk of overheating in most of the apartments despite differences in room number and age.
Performance assessment of ventilative and radiant cooling systems in office buildings during extreme weather conditions under a changing climate
(2022-10-01) Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Jylhä, Kirsti; Kosonen, Risto; Lestinen, Sami
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The buildings’ HVAC system design and indoor conditions are affected by climate change. This study aimed to investigate the effects of climate change on office buildings’ cooling system design and indoor temperature conditions in the Nordic cold climate. Thus, two types of mechanical cooling systems, the all-air (ventilative) and the air-water (radiant), are designed in a new office building by using new cooling design days (1% risk) of the current and future climate of southern Finland. Moreover, dynamic simulations of energy and indoor conditions are performed using different average and extreme climate scenarios. The results showed that the dimensioning cooling power demand with the current climate design day (1% risk level) in the all-air system is higher than in the air-water system by about 18% and it increases significantly when using future climate design days depending on the climate scenarios. The annual maximum cooling power demand in the current and future average climate is below the current climate dimensioning power for both systems. While during extreme weather conditions of the current and future climate, it is higher than the current climate dimensioning power for both systems. Despite the increase in cooling power demands, the dimensioned cooling system using the current climate design day can provide a thermal comfort level of category I of EN16798-1 in all the spaces during the current and future average climate, and category Π during the current and future extreme weather conditions. Thus, ventilative and radiant cooling systems equally perform under a changing climate.
Rakennusten kosteusvauriot ja ylilämpeneminen muuttuvassa ilmastossa – RAIL
(2023-01-11) Lahdensivu, Jukka; Pakkala, Toni; Pikkkuvirta, Jussa; Räsänen, Aapo; Alastalo, Santtu; Karvonen, Anne; Täubel, Martin; Pekkanen, Juha R.; Juntunen, Miina; Velashjerdi Farahani, Azin; Jokisalo, Juha; Kosonen, Risto; Jylhä, Kirsti; Lanki, Timo; Leino, Olli; Kollanus, Virpi
Commissioned report
Tutkimuksessa tehtiin laskennallisia tarkasteluja ulkoseinärakenteiden rakennusfysikaalisesta toimivuudesta nykyisessä ja projisoiduissa tulevaisuuden ilmastoskenaarioissa. Lisäksi laskennallisella mallinnuksella tarkasteltiin ilmastonmuutoksen vaikutuksia rakennusten ylilämpenemiseen ja lämpöviihtyvyyteen. Rakennusten kosteusvaurioiden ja niihin liittyvien mikrobien yhteyttä ihmisten terveyteen tarkasteltiin kahdella systemaattisella katsauksella. Korkeiden kesäajan lämpötilojen vaikutusta terveyteen nyt ja tulevaisuudessa arvioitiin epidemiologisin sekä vaikutusarvioinnin menetelmiin. Tehtyjen tarkastelujen perusteella suurin osa Suomessa yleisesti käytössä olevista ulkoseinärakenteista pärjää myös muuttuvassa ilmastossa. Homehtumisriski nousee sellaisissa ulkoseinärakenteissa, jotka päästävät viistosadetta lävitseen, pidättävät vettä rakenteen huokosverkostossa (tiili, läpäisevä betoni) ja tuuletus on heikkoa. Palvelutalojen sekä asuntojen laskennalliset ja havaitut lämpötilat nousevat korkeiksi jo nykyisessä ilmastossa. Pelkät auringonsuojausratkaisut eivät ole riittäviä pitämään huonelämpötiloja riittävän alhaisella tasolla, vaan sen lisäksi tarvitaan myös aktiivista jäähdytystä erityisesti helleaaltojen aikana. Jäähdytys tulisi kohdistaa rakennuksiin, joissa asuu ikäihmisiä, sillä heillä terveysriskit ovat suurimmat. Ilman lisätoimia tulevat korkeiden lämpötilojen terveyshaitat huomattavasti lisääntymään Suomessa jo lähitulevaisuudessa väestön ikääntyessä.
The risk of overheating and energy demand of new and old Finnish apartment buildings in the cooling season
(2021) Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Kosonen, Risto
A4 Artikkeli konferenssijulkaisussa
This study has compared the risk of overheating of a new and old apartment building in Finland and aimed to improve the indoor temperature conditions of the new apartment building using the passive strategies (sun shading, window opening, and window properties) and an active cooling system. So that seven different cases were defined and simulated. Regarding the results, the risk of overheating in the old building is significantly less than in the new building, and using new well-insulated windows with the same old wall construction in the old building, decreases the heating demand but has no significant effect on indoor air temperature. So that the windows are more important for energy usage but not for the indoor air temperature in the old Finnish apartment building during the summer period. Using openable windows would be the best passive solution for keeping the indoor air temperature of the spaces of the new building within the comfort limits with less than 10% of the time above the recommended temperature limits based on EN 16789-1 standard without any significant increase in heating demand. While Using an active cooling system in the living room of each apartment is the only solution that can provide thermal comfort for 100% of the cooling season in all the spaces including bedrooms.
Simulation analysis of Finnish residential buildings’ resilience to hot summers under a changing climate
(2024-04-01) Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Jylhä, Kirsti; Kosonen, Risto
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This study evaluated how residential buildings in Finland's cold climate withstand hot summers under climate change. The buildings' responses to outdoor temperatures, overheating, energy consumption, and cooling power demand were investigated with the actual data of the hot summer of 2018, and its projected conditions for 2050 and 2080 under the highest Representative Concentration Pathway. The results revealed that lightweight structured detached houses reacted about two times faster to outdoor temperatures. The new apartment and the new elderly house, constructed according to the latest Finnish building code, showed slower responses and lower indoor temperatures during current and future hot summers with no degree hours above the Finnish health limits of 30 °C/32 °C. Conversely, the old non-renovated apartment building and elderly house built in the 1970s–80s experienced higher indoor temperatures. Their indoor temperature surpassed 30 °C/32 °C even in the current climate. Although passive solutions reduced indoor temperatures effectively, hot summers necessitated active cooling systems. The cooling energy and power demand in the old buildings were higher compared to the new ones. However, the cooling electricity consumption was considerably small compared to the heating and total energy consumption in all the studied buildings. It was projected to increase in future climates by 40–160 % depending on the building type and climate scenario.
Thermal comfort and energy demand of a Finnish detached house in a changing climate
(2021) Velashjerdi Farahani, Azin; Jokisalo, Juha; Korhonen, Natalia; Kosonen, Risto
A4 Artikkeli konferenssijulkaisussa
This study investigated the effects of passive strategies (orientation, thermal mass, window opening, and window properties) and the usage of an active cooling system on indoor temperature conditions and energy demand of a detached house in Finland in current and future climatic conditions (2050). So that nine different cases were defined and simulated. Regarding the results of passive strategies, in the current climate, using openable windows would be the best solution for keeping indoor air temperature of the spaces. While using an active cooling system in the hall of the upper floor is the only studied solution that can provide thermal comfort in the other spaces such as the warmest bedrooms, in the whole time of the cooling season in both current and future climate. In the future climate, the heating demand decreases way more than the amount of increase in the cooling demand but providing thermal comfort in the spaces will be challenging.
Toteutuneet kesäaikaiset huonelämpötilat helsinkiläisissä kerrostaloissa
(2021-10-26) Jokisalo, Juha; Pajunen, Sami; Kravchenko, Ilia; Kilpeläinen, Simo; Kosonen, Risto; Velashjerdi Farahani, Azin; Korhonen, Natalia
A4 Artikkeli konferenssijulkaisussa
Tässä tutkimuksessa selvitettiin, kuinka korkeita toteutuneet kesäaikaiset Huonelämpötilat ovat helsinkiläisissä kerrostaloasunnoissa ja onko kohteiden rakentamisvuodella vaikutusta huonelämpötiloihin. Tutkimuksessa analysoitiin noin 6000-8000 kerrostaloasunnon kesäaikaiset huonelämpötilat, jotka on mitattu vuosien 2018 – 2020 aikana IoT mittareilla käyttäen yhden tunnin aikaresoluutiota. Asunnot sijaitsevat kaikkiaan 690 eri kerrostalossa, joista vanhimmat on rakennettu ennen 1950-lukua ja uusimmat 2010 luvulla. Tulokset osoittavat, että eri asuntojen väliset lämpötilaerot ovat varsin suuria, mutta kuumimpien hellejaksojen aikana merkittävä osa asunnoista ylilämpenee. Erityisen kuuman hellekesä 2018 aikana huonelämpötila ylitti 27°C yli 150 astetuntia lähes 80%:ssa tarkemmin analysoiduista noin 1100:sta asunnosta. Saman hellekesän aikana vähintään noin 3% kaikista mitatuista noin 6000 asunnosta ylitti Sosiaali- ja terveysministeriön asumisterveysasetuksen toimenpiderajan 32°C. Analysoidussa aineistossa rakentamisvuoden vaikutus tutkittujen asuntojen ylilämpenemiseen 27°C ja sen ylittävien huonelämpötilojen osalta on suhteellisen pieni. Mutta vuosien 2004-2012 aikana rakennetuissa kohteissa 25°C ja 26°C huonelämpötiloja esiintyy hieman muita ikäryhmiä enemmän.