'Climate connectivity' in the daylight factor basis of building standards

This paper describes a proposal for a daylight standard for CEN countries. It is now widely accepted in the research community, and increasingly so amongst practitioners, that the standards/guidelines for daylight in buildings are in need of upgrading. The essence of the proposal is that the `target' for daylight provision should be founded on the availability of daylight as determined from climate files. The proposal is in fact a refinement of an approach originally described in a CIE document from 1970, and which appears to have been largely overlooked since then. The proposal states that a design should achieve a target daylight factor at workplane height across a specified percentage of the relevant floor area for half of the daylight hours in the year, where the target daylight factor is based on the provision of 300 lux. A key feature of the refinements are the formulation of the methodology such that the likelihood for misinterpretation and `game-playing' is greatly reduced, if not eliminated altogether. The method, founded on cumulative diffuse illuminance curves, could be introduced relatively swiftly since it requires only modest enhancement of existing daylight prediction tools. In addition, the proposal will provide a sound `footing' for eventual progression to evaluations founded on full-blown climate-based daylight modelling

Prescribing for Daylight: Can We Account for the Disparate Measures Within A Unified Framework?

The potential for a building design to provide daylight for general illumination was, until very recently, evaluated using only the daylight factor, i.e. a ratio of internal to external illumination under a single standardised overcast sky. Other known effects of daylight, such as the occurrence of visual discomfort which is more likely to occur during non-overcast conditions, were assessed or estimated by other means, often relying more on the skill of the experienced lighting designer than by use of a repeatable set procedure. In the last few decades there has been a gradual increase in awareness of the non-visual effects of daylight/light received by the eye Webb (2006). The quality and nature of the internal daylit environment is believed to have a significant effect on human health in addition to general well-being and worker productivity. Demonstrating compliance with various guidelines at the design stage is an ever increasing concern. For daylight this is invariably carried out nowadays using simulation rather than scale models. After many decades of reliance on the daylight factor as the sole quantitative daylight metric, there has been an explosion of activity in daylight modelling research which has delivered numerous new techniques, approaches and metrics. This paper describes various end-user requirements - both current and emerging - for daylight modelling and discusses how these might be accommodated within a single modelling framework

Transmission Illuminance Proxy HDR Imaging: A New Technique to Quantify Luminous Flux

A technique to measure arbitrarily complex luminous fluxes across large areas is presented. The technique is founded on high-dynamic range (HDR) imaging technology and can be achieved using a standard consumer digital camera and everyday materials such as printer-grade white paper. The same approach can also be used to determine the direct and diffuse components of illuminance. The technique has been named transmission illuminance proxy - high dynamic range imaging or TIP-HDRI

Neutral Daylight Illumination with Variable Transmission Glass: Theory and Validation

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Climate-based Daylight Performance: Balancing Visual and Non-visual Aspects of Light Input

This study uses a domestic dwelling as the setting to investigate and explore the applicability of daylighting metrics for residential buildings, including the formulation of metrics for nonvisual effects. The simulation approach used to generate the performance data from which the metrics are derived is called climate-based daylight modelling (CBDM). This approach delivers predictions of various luminous quantities using sun and sky conditions that are derived from standardised annual meteorological datasets. Although there are uncertainties regarding the precise calibration, there is now sufficient empirical data to parameterise models that also simulate the non-visual aspects of daylight, e.g. for circadian entrainment and a general sense of "alertness". For these non-visual aspects, vertical illuminance at the eye was predicted using a modified climate-based daylight modelling approach. In the paper, we consider what relation there might be between the three aspects of daylight provision and if these relations appear to be complementary or conflicting in nature: for task; to reduce electric lighting usage; and, for non-visual effects. The implications for future building guidelines for daylighting are also discussed

Daylighting Metrics for Residential Buildings

It is now widely accepted that the standard method for daylighting evaluation - the daylight factor – is due for replacement with metrics founded on absolute values for luminous quantities predicted over the course of a full year using sun and sky conditions derived from standardised climate files. The move to more realistic measures of daylighting introduces significant levels of additional complexity in both the simulation of the luminous quantities and the reduction of the simulation data to readily intelligible metrics. The simulation component, at least for buildings with standard glazing materials, is reasonably well understood. There is no consensus however on the composition of the metrics, and their formulation is an ongoing area of active research. Additionally, non-domestic and residential buildings present very different evaluation scenarios and it is not yet clear if a single metric would be applicable to both. This study uses a domestic dwelling as the setting to investigate and explore the applicability of daylighting metrics for residential buildings. In addition to daylighting provision for task and disclosing the potential for reducing electric lighting usage, we also investigate the formulation of metrics for non-visual effects such as entrainment of the circadian system

Turkish D-light : accentuating heritage values with daylight

Historic buildings have their own cultural identity, which is often related to their aesthetic qualities such as period characteristics (geometry, size, colour, form and shape), materials and construction. Daylight is one of the primary elements contributing to the distinctiveness of the visual environment of many historic buildings, but is rarely considered as one of the components that shape the character of a building when adaptive preservation schemes of historical buildings are planned. Many historic buildings were originally designed to accommodate activities different to their new use and preserving the quality of daylight that originally contributed to their visual identity is a challenging task. Maintaining the ‘day-lit appearance’ of a building can be particularly problematic if the building is to be used as a museum or a gallery owing to the artefacts’ conservation requirements. This work investigated the opportunities of maintaining the original ambient conditions of renovated historical buildings while meeting the required daylight levels of the proposed new use. The study utilised an annual daylight simulation method and hourly weather data to preserve daylight conditions in renovated historic buildings. The model was piloted in a Turkish bathhouse situated in Bursa, Turkey, that is currently under renovation. The simulation model produces 4483 hourly values of daylight illuminance for a period of a whole year using the computer program Radiance. It is concluded that daylight characteristics should be taken into account when developing a renovation scheme. With increasing pressure on valuing historic buildings in many parts of the world, the work reported here should be beneficial to those concerned with the conservation and adaptive reuse of historic buildings. The study findings could also be useful to those interested in predicting potential energy savings by combining daylighting and electric lighting in historic buildings

Double-Peaked Low-Ionization Emission Lines in Active Galactic Nuclei

We present a new sample of 116 double-peaked Balmer line Active Galactic Nuclei (AGN) selected from the Sloan Digital Sky Survey. Double-peaked emission lines are believed to originate in the accretion disks of AGN, a few hundred gravitational radii (Rg) from the supermassive black hole. We investigate the properties of the candidate disk emitters with respect to the full sample of AGN over the same redshifts, focusing on optical, radio and X-ray flux, broad line shapes and narrow line equivalent widths and line flux-ratios. We find that the disk-emitters have medium luminosities (~10^44erg/s) and FWHM on average six times broader than the AGN in the parent sample. The double-peaked AGN are 1.6 times more likely to be radio-sources and are predominantly (76%) radio quiet, with about 12% of the objects classified as LINERs. Statistical comparison of the observed double-peaked line profiles with those produced by axisymmetric and non-axisymmetric accretion disk models allows us to impose constraints on accretion disk parameters. The observed Halpha line profiles are consistent with accretion disks with inclinations smaller than 50 deg, surface emissivity slopes of 1.0-2.5, outer radii larger than ~2000 Rg, inner radii between 200-800Rg, and local turbulent broadening of 780-1800 km/s. The comparison suggests that 60% of accretion disks require some form of asymmetry (e.g., elliptical disks, warps, spiral shocks or hot spots).Comment: 60 pages, 19 figures, accepted for publication in AJ. For high quality figures and full tables, please see http://astro.princeton.edu/~iskra/disks.htm

Climate fluctuations and the spring invasion of the North Sea by Calanus finmarchicus

The population of Calanus finmarchicus in the North Sea is replenished each spring by invasion from an overwintering stock located beyond the shelf edge. A combincation of field observations, statistical analysis of Continuous Plankton Recorder (CPR) data, and particle tracking model simulations, was used to investigate the processes involved in the cross-shelf invasion. The results showed that the main source of overwintering animals entering the North Sea in the spring is at depths of greater than 600m in the Faroe Shetland Channel, where concentrations of up to 620m -3 are found in association with the overflow of Norwegian Sea Deep Water (NSDW) across the Iceland Scotland Ridge. The input of this water mass to the Faroe Shetland Channel, and hence the supply of overwintering C. finmarchicus, has declined since the late 1960s due to changes in convective processes in the Greenland Sea. Beginning in February, animals start to emerge from the overwintering state and migrate to the surface waters, where their transport into the North Sea is mainly determined by the incidence of north-westerly winds that have declined since the 1960s. Together, these two factors explain a high proportion of the 30-year trends in spring abundance in the North Sea as measured by the CPR survey. Both the regional winds and the NSDW overflow are connected to the North Atlantic Oscillation Index (NAO), which is an atmospheric climate index, but with different time scales of response. Thus, interannual fluctuations in the NAO can cause immediate changes in the incidence of north-westerly winds without leading to corresponding changes in C. finmarchicus abundance in the North Sea, because the NSDW overflow responds over longer (decadal) time scales