Applied Mechanics and Materials Vol. 824

Abstract: To compute energy demand based on the reference years hourly averages of external variables are often generated in the smooth form. On the other hand, daylight should be evaluated in a shorter interval because human eyes perceive light in the moment of its occurrence. This study shows alternative to the description of annual daylight conditions based on statistic characteristics mean and median to create Daylight Standard Reference Year for Bratislava. Both methods are presented as contribution to the development of daylighting engineering. Authors are interested in lighting engineering to ensure satisfactory luminous environment at workplaces and in buildings for housing and recreation. Good daylighting in interiors is also related to the reduction of electricity consumption for lighting. This paper presents method for generation of daylight standard reference year DSRY based on one minute data measured at CIE IDMP stations. This reference year can be applied for evaluation of daylighting in the specific locality.

Abstract: Lighting conditions in buildings are verified by experts on a daily basis. Such verifications may be done at several phases in various ways. In the field of daylighting, it is common to make an assessment within the pre-design and in-design phases of a construction work throughout calculations, only rarely by measurements. This approach is the opposite of artificial lighting design, which is done within the in-design phase by calculations and is verified by measurements in post-realization phase. The verification of artificial lighting design is required by the building and public health authority otherwise buildings cannot be approved to use. In the field of daylighting, measurements could be performed as well, nevertheless those are often problematic because regulations usually require fulfilments of the daylight factor which can be determined only under CIE overcast sky. Howbeit, both artificial lighting and daylighting measurements are influenced by many errors, e.g. errors of light measurement instruments, measurement conditions, measurement methods and human factor. The paper is focused on this aspect of lighting design, more specifically on the daylighting measurement errors.

Abstract: If researchers measure illuminance with illuminance meters, they should apply meters appropriate quality, with known accuracy and type of uncertainties. Therefore the test measurements should be performed before carrying out experiments. Illuminance measurements applied in research require using calibrated photometric heads because sensors measure various illuminance levels due to degradation in time. Accuracy of every measurement is influenced by errors of instrument construction and of measuring procedure. During preparation of experiment and its carrying out should be these errors reduced at the most. This paper discusses influence of illuminance quality, importance of the photometric heads calibration on the Daylight Factor measurements.

Abstract: Daylight factor is one of the physical parameters affecting indoor environmental. We can determine this factor in many ways. The main ways are computational methods, in situ measurements and finally measurements in architectural models. Measurements in models enable us comparison both measurements under real sky and under artificial sky. We can study changes in internal conditions - the colors and variability of the interiors and potential variability of window openings. Using of mini - photometer head in measurements enable us to give precision quality of design daylight in interior and validate computational methods for the real space.

Abstract: Quality of the indoor environment is determined by physical and psychophysical factors. People spend in the interiors most of the time during the day. Therefore indoor visual, thermal and acoustic effects are important for their health and work productivity. Visual environment can be evaluated in term of daylight availability, spatial luminance distribution and access to sunlight. Unless availability of sky/diffuse light can be considered for window design because of low intensities, the direct sun radiation with its original wavelength composition and high intensity is important for health and stimulation of human body organs in moderate climatic zones. To evaluate access to sunlight, there is necessary to determine the sun position on the sky, dimensions of envelops and windows as well as orientation of significant apertures and potential impact of external obstructions. Sun rays reaching the window surface can or cannot penetrate into the interior. This depends on the angle of sun beam incidence, orientation and dimensions of the aperture, thickness and structure of the envelope. Angle in which incident rays penetrate in the interior is so called acceptance angle. Angle in which incident rays are not causing insolation of interiors or cannot penetrate through the window glazing is so called dead angle. This paper analyses and discusses the meaning and dimensions of the dead angle.

Abstract: Daylighting is one of the key parameters of internal environment generation in buildings. This parameter determines creation of suitable conditions for visual activities in internal spaces and contributes to human well-being and comfort. Daylight is also the primary stimulus for synchronizing the human circadian photobiological system. Traditional parameters and criterions based explicitly on photopic vision have been critically re-evaluated and basic principles of circadian photometry have been developed in theoretical level. Nevertheless daylighting has often been neglected or left out from the main design proposals, which are usually just focused on covering basic needs for vision tasks represented barely by the illumination limits on working plane. Because the amount of light entering the eye is the most important for circadian entrainment, the illuminance recorded on a vertical plane, at eye level, is more significant for human biological system. This paper deals with the comparison of internal horizontal and vertical illuminance recorded in 3 models of room, inserted in simulation program Radiance and illuminated by three types of lighting devices, i.e. window, light-pipes and permanent supplementary artificial lighting represented by the combination of window and light-pipes. Achieved data also express the influence of a workplace position on the amount of illuminance entering the eye according to the direction of the incoming daylight from windows in side-lit room.

Abstract: Examination, design and control of internal light conditions in permanently occupied spaces belong to important actual architectural issues. Especially in offices, workplaces can be often situated far from window. As the new medical facts were emerging during last decade, the significance of the non-visual human response on light, also known as circadian efficiency of light has been rising [1]. Biological stimulation of light depends on quantitative and qualitative properties of light, which penetrates directly into the human eye in contrast to visual stimulation depending more on the amount of the light reflected from the observed surfaces. Inappropriate selection of spectral filter in windows or internal coloured surfaces may significantly decrease potential light biological stimulation and may reflects in higher rate of Sick Building Syndrome (SBS) occurrence, which is connected to Seasonal Affective Disorders (SAD). The paper describes two experiments done in real conditions, focused on the effect of internal coloured surfaces and the influence of tinted glazing on daylight spectral characteristics in three deep space model rooms exposed only to natural daylight. Deeper positions with sensor`s orientation toward window and side wall were selected. The position of sensor representing the eye of sitting person and especially its orientation regarding to window proved noticeable different rate of biological stimulation`s efficiency in comparison with same level of horizontal illuminance on working area.

Abstract: Photovoltaic glazing is a relatively novel type of glazing material, suitable for application in nearly-zero energy buildings. As a special type of building integrated photovoltaic (BIPV), it generates energy from solar radiation and ensures the performance characteristics of building envelope. This paper presents a combined approach of evaluation of luminous characteristics of glazing based on photopic and circadian action spectra. Measurements were performed on 6 photovoltaic glazing samples with amorphous silicon solar cells. The samples differ in type of spacing and rear glazing colour. The results have shown that PV glazing with coloured glazing should be used with caution, especially in rooms with high daylighting requirements. Obtained results can be used during designing process to evaluate impact of PV glazing on visual comfort.

Abstract: Daylighting simulation programs use different methods and algorithms for illuminance calculations in buildings. It is widely known that results of different lighting simulation programs does not have to be the same for two or more identical rooms. Hence CIE issued Technical Report 171: 2006 which presents test cases to assess the accuracy of lighting computer programs. However, these test cases are simple and the accuracy of daylighting computer programs can be different for more complex cases. The purpose of this paper is a comparison of differences in the results computed by various daylighting simulation programs for selected test cases according to CIE 171: 2006 and for more complex cases.

Abstract: Building performance simulation is traditionally used to support the building design process. However, it can also be used during building operation phase by providing relevant data to building automation systems. We refer to monitoring and metering data generated by computational simulation (virtual) models as data from virtual sensors. Virtual sensors, if reliably and effectively incorporated, can expand the reach of real sensors. A continuous supply of virtual sensor data can support near real-time representation of both primary environmental variables (e.g., air temperature, relative humidity) as well as complex performance indicators (e.g., thermal comfort indices, visual glare). Such information, especially in large multi-zone buildings, would be otherwise expensive to obtain from real sensors due to high capital costs of the sensors, their installation, networking, and maintenance. Virtual sensors can increase the resolution of sensory information, as they imply little monetary expenditures and are not limited in view of numbers and location.Conventional building energy simulation uses a model of the building and creates boundary conditions using historic weather data and predefined schedules for lighting and equipment load. This method is suitable for evaluation of building designs but not suitable for monitoring and control processes during building operation phase, as such processes usually require actual real-time information regarding boundary conditions. Thus, capability to automatically update simulation model's boundary conditions in real-time using monitored data is required. Toward this end, a supervisory software application is developed, in Java programming language, to implement and illustrate the concept of virtual sensors using Radiance simulation program. This application creates virtual illuminance sensors in Radiance model and then automates the process of regularly updating simulation model's external and internal boundary conditions (solar irradiance, state of electrical lighting elements) by using real-time monitored data from on-site weather station and building management system (BMS). As a result, the simulation kernel can continuously generate virtual sensor readings that can be utilized by building monitoring and/or control systems. This paper discusses the general architecture of the application, to further illustrate the concept of virtual sensors. Moreover, it discusses the accuracy of virtual illuminance sensors by comparing their output with monitored illuminance data in realistic test scenarios.