Analysis of daylight factors and energy saving allowed by windows under overcast sky conditions

Acosta, Ignacio; Muñoz, Carmen; Campano, Miguel Ángel; Casas, Jaime Navarro

doi:10.1016/j.renene.2014.12.017

Cited by 77 publications

(42 citation statements)

References 19 publications

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“…Carrying out a holistic characterisation of systems based on all of these factors is time-consuming, and choices are often dependent on which parameters are selected and used for the respective analyses. However, a widely used design parameter amongst architects and daylight-consultants is the Daylight Factor (DF) [41]. This express the ratio of daylight present in a room compared to the exterior daylight level under an overcast sky [42,43].…”

Section: Assessing Shading System Performancementioning

confidence: 99%

Solar Shading in Low Energy Office Buildings - Design Strategy and User Perception

Grynning

Lolli

Wågø

et al. 2017

Journal of Daylighting

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The objective of this paper is to investigate the visual comfort and quality of daylight in modern office buildings in the Nordic climate. A study of various daylight-related aspects and qualities was carried out for three different office buildings, using a combination of quantitative and qualitative methods. The focus was on a combination of user perception of daylight quality and assessment of the daylight amount and quality, by using the daylight factor (DF) and useful daylight illuminance parameters. Previous studies and experiences from construction examples indicate that users, in general, complain about lack of manual control of systems and too low daylight levels, even if the requirements in the building codes are satisfied. Furthermore, they complain about control algorithms of the shading devices, which cause undesired automatic opening and closure of such devices. Thus, causing disturbances and irritation amongst the users. Hence, interviews with key personnel in a modern and architecturally acclaimed office building were carried out in addition to an in-depth analysis of previous surveys of a zero-energy office building. It was found that automatic moveable shading can be regarded as a source of discomfort. This is due to the lack of manual-control override possibilities, which causes disturbances due to the system moving up and down. In one of the offices, the users disabled the exterior shading system. However, the external fixed shading and the internal manually operated roller blinds were found to be satisfactory. The results from a previous study showed that the users in the Marche building are in general satisfied with the daylight. One of the main reasons for this, according to the users, is that they have manual control of the shading system. Manual control of the shading systems is preferred by users in the office buildings studied. Daylight simulations showed that the external fixed shading system combined with internal shading give satisfactory DFs and an even distribution of the daylight levels in a south-facing office. According to the users, the external fixed shading is a good system for south facing offices, when local glare issues can be solved by interior roller shades. The DF gives information of the daylight distribution, which in certain cases might be adequate. However, this is not enough as a descriptor for user comfort, as other factors such as manual control possibilities and glare discomfort are not included.

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Section: Assessing Shading System Performancementioning

confidence: 99%

Solar Shading in Low Energy Office Buildings - Design Strategy and User Perception

Grynning

Lolli

Wågø

et al. 2017

Journal of Daylighting

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“…It is estimated that artificial lighting can contribute 20-35% to the overall energy consumption of a building. With the correct positioning of the glazing, the energy savings of the lighting can reach 7% when 10% of the façade is glazed and we consider the threshold illuminance of 250 lx [7]. Artificial lighting consumes a large share of energy, especially in office buildings.…”

Section: Parametric Study Of a Family House For Different Orientationsmentioning

confidence: 99%

Different Aspects of Windows in Buildings

Obrecht¹,

Leskovar²,

Premrov³

et al. 2017

WIT Transactions on Ecology and the Environment

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Windows are an important part of the building envelope. They are important for the energy performance of a building, since they enable passive solar gains, reduce the need for artificial lighting and enable natural ventilation. Passive design strategies are important to enhance the performance of buildings without active systems. The passive solar gains of buildings depend on the orientation of the glazing, the glazing type, the micro location and the form of the building. A study of a single family house with different deviations from the main glazing façade, that differ from the main cardinal orientation, is presented. For each case, the optimal glazing point and the optimal glazing area were examined. A southern orientation remains the most optimal for the chosen climate of Ljubljana. Buildings create an artificial environment with restricted access to daylight. To compensate natural light, artificial lighting sources are installed in the building. To illustrate the influence of windows on the energy performance in an office, the needs for artificial lighting were observed. The energy demand caused by the electricity consumption of artificial lighting is substantial, so the positioning of windows and the visual transmittance are of great importance. Beside the size of the window, its form and height plays an important role. Windows also affect the well-being of the occupants. Most of these effects are connected with providing light, natural ventilation and communication with the outside world. These aspects are also present in sustainable building certification schemes. An overview of the health-related topics presented in different certification schemes connected to windows has been made. We have compared different certification schemes in how they deal with issues of light.

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“…Additionally, some studies use simulation models to predict the effects of particular factors on the lighting use, such as glazing, room surface reflectance and location (Acosta, Munoz, Campano, & Navarro, 2015;Krarti, Erickson, & Hillman, 2005), control settings (Garg & Bansal 2000;Reinhart, 2004;Roisin, Bodart, Deneyer, & D'Herdt, 2008) and the use of light pipes (Vasilakopoulou, Synnefa, Kolokotsa, Karlessi & Santamouris, 2016).…”

Section: Lighting Energy-use Studiesmentioning

confidence: 99%

“…By setting this against the savings data quoted in earlier studies, it was possible to reconsider the level of saving using manual switching as the baseline. The simulations considered by Acosta et al (2015) covered a very large number of combinations of different variables; for this comparison one case has been considered: square window, centrally positioned, filling 60% of the façade, with the room placed at 50 latitude and assuming 8 am start. Notes: *includes external light shelf.…”

Section: Selected Comparisons Using Hunt's Estimation Of Manual Contrmentioning

confidence: 99%

Energy saving claims for lighting controls in commercial buildings

Lowry

2016

Energy and Buildings

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Lighting systems consume a significant proportion of the energy used in commercial buildings, and the control of lighting use is an important determinant of the energy performance of buildings. A review and meta-analysis of lighting energy studies in commercial premises is undertaken to investigate difficulties with reported energy-saving claims for popular lighting control methods. Earlier studies have indicated that in some installations automated controls may save very little energy if they are replacing manual control. However, even where manual control would be a reasonable expectation, such as in private offices, it has been common practice to report saving in energy compared to the lights being used throughout the working day, which leads to overstatement of the energysaving potential. However, generally, user behaviour cannot be reliably predicted, which makes it difficult to quantify properly the benefits of adding automatic controls. It is argued that savings should instead be quantified with reference to published norms for lighting use in commercial buildings.

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Analysis of daylight factors and energy saving allowed by windows under overcast sky conditions

Cited by 77 publications

References 19 publications

Solar Shading in Low Energy Office Buildings - Design Strategy and User Perception

Solar Shading in Low Energy Office Buildings - Design Strategy and User Perception

Different Aspects of Windows in Buildings

Energy saving claims for lighting controls in commercial buildings

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