| 1. |
- Bournas, Iason
(author)
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Association between Perceived Daylit Area and Self-reported Frequency of Electric Lighting Use in Multi-dwelling Buildings
- 2022
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In: LEUKOS - Journal of Illuminating Engineering Society of North America. - : Informa UK Limited. - 1550-2724. ; 18:1, s. 83-102
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Journal article (peer-reviewed)abstract
- This paper examines the association between daytime electric lighting use and perceived indoor daylight availability in residential spaces. In addition, occupant preferences were evaluated, in particular which rooms are prioritized in terms of daylight availability. The study deployed a questionnaire survey that was carried out in typical multi-dwelling apartment blocks in Malmö, Sweden (Latitude: 55.6 °N). Occupants were asked to report how often they use electric lighting during daylight hours (EL) in their kitchen, living room and main bedroom, and how much of the floor area they perceive as adequately daylit (DA) throughout the year. Responses EL and DA were measured in seven-point semantic differential scales, and were correlated (Spearman) to evaluate their association for different room groups. Groups were based on age, room function, façade orientation, balcony obstruction and fenestration geometry. In addition, occupants were asked which room they would choose if there had to be one underlit room. Results indicate that EL is strongly associated with DA in the overall room sample (rS = −0.588, p <.01, n = 225). The association is persistent across room groups of different characteristics, with the Spearman rank correlation coefficient ranging between −0.4 and −0.8, and not differing significantly between groups. In terms of preferences, a significantly high proportion of participants would choose the bedroom if there had to be one underlit room (62%, p <.05), while the kitchen was selected by only 5 out of 108 respondents.
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| 2. |
- Bournas, Iason
(author)
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Chapter 12: Introduction to lighting simulations
- 2019
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In: Daylighting and lighting under a Nordic sky. - 9789144125770 ; , s. 371-404
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Book chapter (other academic/artistic)abstract
- This is one the 13 chapters included in the book titled "Daylighting and Lighting under a Nordic sky". The chapter focuses on daylight simulation for buildings. It begins with the fundamental elements existing in every daylight simulation scenario, i.e. the scene geometry, the sky model, the ground, the areas of interest, the space usage and the simulation engine. The reader is introduced to different daylight simulation techniques developed over the past decades, and which are deployed in available simulation tools today. Eventually, procedures to conduct annual daylight simulations are presented, alongside the implications of different methods and aspects of daylight simulation control.
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| 3. |
- Bournas, Iason
(author)
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Daylight compliance of multi-dwelling apartment blocks : Design considerations, evaluation criteria and occupant responses
- 2021
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Doctoral thesis (other academic/artistic)abstract
- This thesis examines the daylight compliance of residential spaces, in particular apartments in multi-dwelling building blocks, and provides knowledge that may prove useful for the development of future daylight criteria for dwellings. The implications of design choices on daylight compliance of spaces and the effect of daylight criteria on the level of compliance are at the core of this work. Daylight simulations were performed to evaluate a large sample of representative apartment buildings according to past and present daylight criteria. Self-administered questionnaires were also used to investigate occupant preferences and subjective impressions of daylight conditions in the dwellings. The simulations and questionnaires divide this work into two parts, which are connected on the basis of the same study object: multi-dwelling buildings.The first part includes a review of daylight regulations in Sweden from the time the term “daylight” first appeared in 1960. It proceeds with compliance testing results for a large sample of multi-dwelling blocks, evaluated according to the current Swedish daylight compliance criteria. Several criteria commonly used internationally are assessed for the same spaces, to evaluate compliance differences when using different criteria. The review concludes that there has been no significant progress in Swedish daylight regulations since 1975, when the basis for the current daylight factor criterion was first formulated. It also argues that the current geometric criterion has limitations due to spatial implications deriving from its formulation. The compliance testing results indicate that Swedish daylight criteria have not been successful in safeguarding daylight access for residential spaces historically, especially in denser urban areas, perhaps because they were expressed as “general recommendations” instead of “mandatory provisions”. To this end, several buildings built prior to the introduction of daylight criteria, and built only by architectural intuition, perform better than regulated buildings. A more detailed assessment of the investigated rooms using additional criteria indicated which building types perform better overall, which geometric attributes are more significant for compliance, and the effect of urban density on compliance.The second part includes results from a questionnaire survey carried out in the city of Malmö, the third largest city in Sweden. The questionnaires were distributed in buildings of the same block typologies as the buildings evaluated via simulations in the first part of this research. This second part concerns daylight perception, electric lighting use, and occupant preferences with respect to daylighting among room types. The questionnaire rating scales were validated for their suitability as a form of measurement for daylight surveys. The reported electric lighting use was compared between different room types, geometries, and facade orientations to evaluate whether there is less use of lighting in rooms with specific characteristics. The relation between reported daylit area and electric lighting use was analysed to assess whether daylight availability can yield reductions in electric light use, to what extent, and under which conditions. The survey also revealed clear occupant preferences, indicating the room types where daylight availability is prioritised.
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| 4. |
- Bournas, Iason
(author)
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Daylight compliance of Swedish residential blocks according to past and current performance criteria
- 2019
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In: PROCEEDINGS of the INTERNATIONAL CONFERENCE on CHANGING CITIES IV : Spatial, Design, Landscape & Socio-economic Dimensions - Spatial, Design, Landscape & Socio-economic Dimensions. - 9789609922692
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Conference paper (peer-reviewed)abstract
- The importance of daylight to occupants’ health and wellbeing has been extensively documented, as well as its role in reducing electric lighting use. As a result, most countries have today some form of regulatory framework, specifying minimum daylight requirements for built spaces. The present Swedish building code (BBR – BFS 2011:6) includes general recommendations for daylight provision of residential spaces, which stipulate a minimum window area relevant to the floor area or a minimum point daylight factor within rooms “inhabited more than temporarily”. Currently, policy makers in Sweden are considering the possibility of updating the current regulation, in light of the new European Daylight Standard (EN-17037), recently adopted by the Swedish Standards Institute. The challenges for policy makers include the extensive ongoing development of housing projects and the resulting impact of urban densification on daylight levels. Given this context, this paper investigates the compliance of residential developments, located primarily in Stockholm, for different daylight performance criteria. A sample of 10.888 rooms belonging to 3.151 apartments in 25 multi-family urban blocks was selected to represent different construction eras and major architectural typologies in Swedish urban planning history. All rooms were assessed by Radiance simulations according to the current Swedish regulation, the EN-17037 standard and other, commonly used, international compliance criteria. Results indicate that the implementation of different daylight criteria deem different building typologies better or worse performing, depending mainly on urban density and building height. A consistent finding is that all evaluated developments achieve lower compliance rates when standard 17037 is applied. Finally, policy implications on design and compliance are discussed, along with the necessary future investigations.
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| 5. |
- Bournas, Iason, et al.
(author)
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Daylight regulation compliance of existing multi-family apartment blocks in Sweden
- 2019
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In: Building and Environment. - : Elsevier BV. - 0360-1323. ; 150, s. 254-265
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Journal article (peer-reviewed)abstract
- This research investigates the daylight regulation compliance of existing multi-family housing developments located primarily in Stockholm (Lat.: 59,33 °N), Sweden. A representative sample of 54 buildings consisting of 10.888 individual rooms was modelled according to archived documentation drawings and evaluated by use of Radiance simulations, to test their compliance with the current Swedish daylight regulation. The studied buildings were selected according to their relevance to major architectural typologies of Swedish urban planning history (1926–1991). The assessment was based on a point Daylight Factor scheme (DFP), which stipulates that a specific point in a room should achieve a Daylight Factor DFP ≥ 1%, for the room to be sufficiently daylit. Results indicate that specific architectural typologies consistently yield poor DFP levels compared to other ones. A moderate correlation was found between the density of surroundings and the percentage of compliant rooms per housing development. Finally, the results indicate the existence of distinct periods during Swedish urban planning history, when daylight performance of multi-family houses was affected by different planning practices. Future investigations are under development to evaluate the occupants’ perception of daylight in their apartments, to help define new daylight performance indicators and benchmarks for Swedish households, taking into consideration the limitations of the daylight indicator embedded in the current regulation.
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| 6. |
- Bournas, Iason, et al.
(author)
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Daylight utilization in buildings : Analysis of existing conditions and development of improved rules and metrics
- 2018
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Reports (other academic/artistic)abstract
- This is the report of the work carried out for project "Dagsljusanvändning i byggnader" of the Swedish Energy Agency, project number 41816-1. This research provides background scientific information on the daylight performance of multi family apartment blocks located in Stockholm, and Örebro, Sweden. A sample of 54 buildings that consist of 10 888 individual rooms was evaluated using advanced daylight simulations. The studied buildings were selected based on their construction year and building typology in order to represent the existing building stock built in the previous century (1926 – 1991) as truthfully as possible. All simulations were performed including the existing surrounding urban context. Results show that specific building types consistently yield poor daylight conditions compared to other typologies. Furthermore, the study investigates the rate of complying rooms, apartments and buildings according to the current point Daylight Factor requirement (DFp) of the building code, and proposes new indicators that can be used instead. An average Daylight Factor (DFavg) requirement is proven to be misleading at building level, as rooms located on higher floors influence the average score for the building. At room level, it is shown that there is a high correlation between DFp and the median Daylight Factor (DFmedian) across a grid of points within the whole room area. The same compliance rates are also found by using a daylight requirement at apartment level, instead of room level. Results show that a median Daylight Factor requirement across an apartment area or which considers all but one room of the apartment yields the same percentage of successful outcomes as the current room-based compliance.
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| 7. |
- Bournas, Iason
(author)
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Daylight utilization in the dense Swedish city : Benchmarks, metrics and tools securing good daylighting, low energy use and user acceptance
- 2017
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Conference paper (peer-reviewed)abstract
- Scientific Poster titled “Low-energy daylit dwellings in the dense city - Benchmarks, metrics and tools securing good daylighting, low energy use and user acceptance”, Velux Academic Forum, Berlin, 2 May 2017. This dissemination illustrates the research questions and key aspects of a PhD research project regarding daylight utilization in Swedish apartment blocks, which was initiated in February 2017. The overall aim of the PhD research is to provide findings to help update current regulations and certification systems according to user acceptance, health and the well-being, all while accounting for the Swedish urban fabric and the different architectural choices.
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| 8. |
- Bournas, Iason, et al.
(author)
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Energy efficient and moisture safe row houses in Sweden
- 2015
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In: Proceedings of the 31st PLEA conference.
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Conference paper (peer-reviewed)abstract
- This project consists of a thorough study of an energy efficient and moisture safe row-house, located in the Nordic climate of Sweden. Climate and site analysis, building scale design decisions and finally the evaluation and optimization of its energy performance were different steps of a holistic process aiming at the architectural quality, energy efficiency, comfort and the well-being of users. The final house design is addressing the spatial requirements of the on-going population increase, that is imminent in the developing countries, but while doing so, it exerts minimum impact on environmental resources and avoids ecological damage. The passive house standards had to be reached by applying passive heating strategies to reduce the heating demand. Increasing thermal insulation thickness and thermal mass elements in the house had a significant role in reducing heat loss and keeping the house warm in winter nights. Other passive house standards, U-values of envelope elements as well as the window-to-wall area played an important role. The moisture risks had to be avoided and the wooden construction proved to function well under the climatic conditions. An innovative method of timing the shading and nighttime natural ventilation was included as a passive strategy for natural cooling. Time period, position and type of shading was optimized according to hourly data and the correlation of internal and solar gains, and their impact on the operative temperature. To ensure summer wind cooling, the interior spatial distribution and circulation areas were designed to exploit the stack effect and cross ventilation by the opening of specific windows. A water retention technique was achieved by coupling recirculated hot water with electrical water heater. The overall energy intensity would finally be assessed and further minimized by the use of an active photovoltaic system on the roof, to exploit the renewable energy of the sun.
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| 9. |
- Bournas, Iason, et al.
(author)
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Energy renovation of an office building using a holistic design approach
- 2016
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In: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 7:September 2016, s. 194-206
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Journal article (peer-reviewed)abstract
- This paper presents a holistic approach to perform energy renovations of office buildings. A real case study is used to demonstrate how different software can be used to facilitate the work of architects and engineers during different design stages. Initially, the moisture safety of the building is coupled to its energy performance to define the optimum insulation level. The new interior layout is based on an initial daylight study, rather than on architectural intuition. On a second stage, shading and natural ventilation are studied to eradicate any cooling demand, while the interdependence between heating energy and daylight is assessed for the use of light-wells. To demonstrate the trade-offs between visual control and electrical lighting, different shading systems are examined for a cellular office. Finally, two alternate HVAC systems are analyzed to investigate whether passive standards can be achieved with an all-air system and/or a hydronic system.
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| 10. |
- Bournas, Iason, et al.
(author)
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Innovative solutions for good daylighting and low energy use in multi-family dwellings: MKB Greenhouse, Malmö, Sweden
- 2017
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Reports (other academic/artistic)abstract
- This is the report of the work for project Dagsljuskrav i miljöcertifierade byggnader" of the Swedish Energy Agency, project number: 39682-1. The study was focused on the energy use and daylight conditions in the multi-family building Greenhouse located in Malmö, Sweden. The aim of the study was first to analyze and develop innovative design solutions for multi-family dwellings with good daylighting and low energy use thereby solving the conflict between these two aspects. The second objective was to validate the simulation tools normally used in the practice of a large architectural office (White architects). The third objective was to verify the adequacy of the current minimum daylight factor requirement in relation to subjective assessments by building inhabitants of Greenhouse. These objectives were met by using a research method based on measurements, advanced lighting and energy simulations and subjective assessments. The results indicate that the simulations allow predicting the measured values with a reasonable accuracy. The results also show that the presence of a glazed sunspace and balcony has a significant impact on daylighting indoors, reducing the daylight factor by at least 50% in adjacent spaces under overcast sky conditions. The simulations also validated the relevance of having larger window sizes on the south orientation, intermediate sizes on the east and west orientations and smaller sizes on the north orientation, when highly insulated windows are considered. However, overheating issues need to be addressed at the early design stage with provision of efficient solar shading protections. The study also shows that daylighting is generally preferred over electric lighting by the inhabitants and that although the highest daylighting level criteria was used for the certification of the building, a significant portion of tenants found the daylight level to be ‘neither bright nor dark’ or ‘dark’, which was an unexpected result. Overall, the research allows establishing relations between measurements, simulations and subjective assessment.
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