Assessing Urban Chromatic Contagion

A Quantitative Index and an Epidemiological Approach to Prevent Visually Disruptive Facade Interventions

Bibliographic Data

ID22136830
AuthorsMaialen Sagarna Aranburu (0000-0001-7409-030X, University of the Basque Country), María Senderos-Laka (0000-0003-4016-7991, University of the Basque Country), Juan Pedro Otaduy-Zubizarreta (0000-0002-9796-6543, University of the Basque Country), Ana Azpiri Albístegui (0000-0001-8759-1533, University of the Basque Country), Fernando Mora-Martín (0000-0003-1791-0329, University of the Basque Country), José Javier Pérez-Martínez (University of the Basque Country), Mireia Roca-Zeberio (0000-0003-3374-3989, University of the Basque Country)
Year2026
Volume10
Issue7
Pages340
Publication date2026-06-23
Open AccessYes
TypeARTICLE
VenueUrban Science (JOURNAL)
Journal identifiersISSN: 2413-8851 • E-ISSN: 2413-8851
PublisherMDPI AG (PUBLISHER • IT)
DOI10.3390/urbansci10070340
OpenAlexW7165615002
LanguageEN
References cited40

Façades play a decisive role in shaping the visual and symbolic character of historic urban environments. Recent European funding schemes promoting energy-efficient retrofitting have accelerated interventions on building envelopes. Although aligned with decarbonization objectives, these processes are generating significant chromatic and material transformations that risk eroding the visual coherence and cultural sustainability of consolidated urban areas. In the historic Ensanches of San Sebastián, the replacement of traditional envelope systems with new cladding solutions is leading to the loss of the architectural style of some facades and altering their materials, textures, and colors. A progressive “contagion effect” has been identified, whereby dissonant chromatic schemes—often associated with the proliferation of so-called “zebra blocks”, residential buildings with façades clad in alternating black and white stripes that have proliferated in recent urban developments—are replicated across adjacent buildings, gradually weakening spatial continuity and the genius loci of the neighborhood. In response to this phenomenon, this research develops a systematic methodology to analyze, quantify, and anticipate chromatic transformation in consolidated urban fabrics. The study combines historical morphological analysis, classification of architectural periods, and chromatic mapping of recent façade interventions. Based on this framework, a CARI, Chromatic Alteration Risk Index is proposed to evaluate the potential impact of façade alterations on urban chromatic coherence. Drawing on an epidemiological framework, the methodology enables the identification of critical transformation clusters, the assessment of contagion dynamics, and the definition of regulatory thresholds for color and material interventions. By integrating perceptual criteria, urban morphology, and spatial distribution patterns, the study moves beyond descriptive diagnosis and offers a transferable tool for municipal planning. The proposed approach supports the proactive regulation of façade rehabilitation processes, balancing energy efficiency objectives with the preservation of collective memory, material identity, and urban sensory quality. This study proposes a quantitative model of “urban chromatic contagion” to assess how façade color interventions propagate within a neighborhood. We define the Chromatic Integration Percentage (CIP) and the Chromatic Alteration Risk Index (CARI) of the analyzed area. Results indicate that poorly regulated façades show higher chromatic dissonance (low CIP) and act as contagion hotspots, while a clear risk gradient emerges: highly protected buildings present lower risk, whereas mixed typologies and recent rehabilitations concentrate higher CARI values. The model supports preventive urban color management by identifying areas at risk before visible alteration

Chromatic scale · Cladding (metalworking) · Facade · Perception · Psychological intervention · Architecture and Computational Design · Urban Design and Spatial Analysis · Urban Green Space and Health

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Open DOIOpen Access