Immeuble Bureaux Issy-les-Moulineaux - WELL


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IES Consulting provided daylight modelling services for the WELL Building Standard Credit 54 Circadian Lighting Design.

Key Facts

  • WELL Building Standard Credit 54 Circadian Lighting Design

IES Consulting provided daylight modelling services for the WELL Building Standard Credit 54 Circadian Lighting Design on this newly proposed commercial office block in Paris. The office design included ribbons of recessed windows to provide solar protection.

Firstly a VE model of the office facility was created in the Virtual Environment, and this was followed by RadianceIES simulations of an examplar floor to investigate the credit potential. The assessment involved a design day modelled across a series of time steps with results then used to build a daily performance profile of incoming light lux levels. The spaces were modelled to test if natural daylight was sufficient to exceed a 70 lux threshold across 75% of the R+2 floor space for a minimum of 4 hours per day. 70 lux was determined to be the necessary daylight level in conjunction with an artificial light source to meet the Equivalent Melanopic Lux (EML). A design day in March and December would indicate typical and worst case conditions in conjunction with their sky types, respectively sunny and cloudy.

The results indicated on this building there was insufficient daylight to top up the artificial lighting system in floor R+2 to meet the WELL credit requirement. March offers a typical profile in the 60% range helped by the sunnier sky but under an assumption of a cloudy sky the December scenario was in the region of 20% lower. The analysis demonstrated an afternoon increase in lux levels due to the solar angles and building geometry, therefore morning times were preventing satisfactory daylight levels.

Credit 54 Circadian Lighting Design:

Light is one of the main drivers of the circadian system, which starts in the brain and regulates physiological rhythms throughout the body’s tissues and organs, affecting hormone levels and the sleep-wake cycle. Circadian rhythms are kept in sync by various cues, including light which the body responds to in a way facilitated by intrinsically photosensitive retinal ganglion cells (ipRGCs): the eyes’ non-imageforming photoreceptors. Through ipRGCs, lights of high frequency and intensity promote alertness, while the lack of this stimulus signals the body to reduce energy expenditure and prepare for rest.

This feature promotes lighting environments for circadian health. The biological effects of light on humans can be measured in Equivalent Melanopic Lux (EML), a proposed alternate metric that is weighted to the ipRGCs instead of to the cones, which is the case with traditional lux. Tables L1 and L2 in Appendix C show how to calculate the EML of individual lamps and larger spaces.

Melanopic Light Intensity for Work Areas

At least one of the following requirements is met:

  1. Light models or light calculations (which may incorporate daylight) show that at least 250 equivalent melanopic lux is present at 75% or more of workstations, measured on the vertical plane facing forward, 1.2 m [4 ft] above finished floor (to simulate the view of the occupant). This light level is present for at least 4 hours per day for every day of the year.
  2. Electric lights provide maintained illuminance on the vertical plane of equivalent melanopic lux, greater than or equal to the lux recommendations in the Vertical (Ev) Targets for the 25-65 category in Table B1 of IES-ANSI RP-1-12. For example, Reception Desks are provided with 150 equivalent melanopic lux from the electric lights.

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