**Magda Sibley**

Sheffield School of Architecture, The University of Sheffield, Arts Tower, Western bank, Sheffield S10 2TN, UK; m.sibley@sheffield.ac.uk or sibleym3@gmail.com; Tel.: +44-7930-988-8193

Received: 11 August 2018; Accepted: 28 October 2018; Published: 31 October 2018

**Abstract:** This paper provides the first study of vernacular daylighting provision in Moroccan heritage public bathhouses in order to rehabilitate it for experiential authenticity, energy saving and improved users' well-being. The analysis of a representative sample of 13 still working hammams reveals recurrent patterns of oculi numbers and configurations. These consist of one to three rows of eight circular roof openings (oculi) of 18 to 20 cm diameter, arranged along the roof vault of each bathing space. The ratio of total roof openings' area to internal floor area rarely exceeds 2%. Synchronised measurements of horizontal illuminance on the roof and inside the bathing spaces in a case study hammam were conducted in July and August 2016, after rehabilitating all roof oculi. Recorded levels indicated that maximum horizontal illuminance never exceeds 60 lx. The calculation and plotting of daylight factor based on real data reveal levels under 2% and a sudden decline in the hot room early afternoon due to steam accumulation. The paper provides the first benchmark of vernacular daylight rehabilitation in Moroccan heritage hammams and the illuminance it affords. It introduces an innovative combination of historical, architectural and building science methodologies that can be extended to other heritage building types.

**Keywords:** hammam; oculi; vernacular roof lighting; energy saving; well-being; daylighting rehabilitation; authenticity; horizontal illuminance
