Wood perception in daylit interior spaces: An experimental study using scale models and questionnaires

Abstract

This paper explores the impact of daylit wooden environments on human perception and well-being. Several studies have shown that the use of wood in furniture, interior surfaces, and decoration helps create warm, bright, and pleasant ambiences, enhancing psychological well-being and comfort when compared to other materials. The main objective of this research was to assess the effects of different colors, finish, and ratio of wooden surfaces combinations on human perception. More specifically, participants compared simultaneously five different interior wooden scale models of room environments under the natural light of the northern hemisphere in terms of their appreciation, visual comfort, and well-being. The survey involved 80 participants with an exploratory questionnaire in order to compare and classify the different models. Conclusions showed a preference for clear, bright, and warm models for cognitive and small-scale tasks. Darker models in terms of reflectance and lighting ambiences were the least preferred, especially for women.

Full Article

Wood Perception in Daylit Interior Spaces: An Experimental Study Using Scale Models and Questionnaires

Geneviève Poirier,* Claude M. H. Demers, and André Potvin

This paper explores the impact of daylit wooden environments on human perception and well-being. Several studies have shown that the use of wood in furniture, interior surfaces, and decoration helps create warm, bright, and pleasant ambiences, enhancing psychological well-being and comfort when compared to other materials. The main objective of this research was to assess the effects of different colors, finish, and ratio of wooden surfaces combinations on human perception. More specifically, participants compared simultaneously five different interior wooden scale models of room environments under the natural light of the northern hemisphere in terms of their appreciation, visual comfort, and well-being. The survey involved 80 participants with an exploratory questionnaire in order to compare and classify the different models. Conclusions showed a preference for clear, bright, and warm models for cognitive and small-scale tasks. Darker models in terms of reflectance and lighting ambiences were the least preferred, especially for women.

Keywords: Color; Wood; Visual perception; Scale model; Real sky; Daylighting; Ambience; Wood finish; Architecture; Environmental psychology

Contact information: École d’architecture de l’Université Laval, 1 Côte de la Fabrique, Québec, G1K 7P4, Canada; *Corresponding author: genevieve.poirier.9@ulaval.ca

INTRODUCTION

In architecture, the choice of materials for structure as well as for interior finishes constitutes a key phase in the design process, whether for the space functionality and building lifecycle, or for the creation of the desired interior ambience. Natural materials such as wood reduce the carbon footprint of constructions, either for their durability or their recycling and reuse potential. However, when selecting construction materials for interior surfaces, economy often takes precedence over environmental, energy-efficient, or perceptive advantages. Moreover, scarce research is available to determine the real impact of interior surfaces on human perception and comfort, and how people appreciate an interior space depending on its material, finish, color, and emplacement.

Natural materials such as wood could potentially enhance psychological well-being as well as comfort when used as interior surfaces. Kellert et al. (2008) addresses the notion of biophilia, which is the natural and inherent inclination of humans to associate with nature and untouched environments. This dependence on nature reveals mankind’s evolution, which took place in natural environments: “We are much more adapted to natural than built settings. Being in nature is like going home, genetically (Gifford 2007).” Contact with natural light as well as a direct view of a natural scene, are part of the so-called “restorative” architecture that reduces stress and enhances well-being and comfort (Bell et al. 1996; Gifford 2007; Kellert et al.2008; Steg et al. 2012; Burnard et al. 2015). Moreover, access to natural light has been demonstrated to produce an impact on occupants’ mood and overall psychological state, while the photo-biological effect of natural light has an effect on circadian cycles, alertness, and arousal of the occupants (Van den Wymelenberg and Inanici 2009; Arsenault 2012; Borisuit et al. 2015). Kellert et al. (2008) defines some environmental features in restorative design that favours connections between natural and built environments, such as the use of natural colors, integrating natural elements such as fountains or rivers, windows allowing contact with air, natural light and exterior views, plants, and the choice of natural materials.

Several studies compared materiality to validate the predisposition of humans to prefer natural elements. Burnard et al. (2015) compared samples of building materials to classify them from natural to artificial, with participants from three different countries. Less processed materials (wood, brick, stone) were considered the most natural, and these results were similar from one country to another. Although this study classified wood as a natural material, the comparison was performed using samples; other studies examined the impact of wood for real spaces. Rice et al. (2006) compared several photographs representing various spaces decorated with diverse finishes and styles, from natural to synthetic or industrial materials. The results showed that the most popular spaces were naturally daylit and offered natural views. Moreover, the preferred spaces were predominantly composed of wood furnishing and surfacing. Participants considered those spaces as “natural”, “inviting”, “relaxing”, “comfortable”, “rustic”, and “warm” compared with “cold” and “modern” in photographs characterized by the absence of wood (Rice et al. 2006). However, research on perception using photographic comparison was previously recognized as limited in terms of precision (Lau 1972). It is also complex to isolate the real impact of the material on perceived satisfaction since the photograph collection consisted of a large array of variables such as ceiling height, number of windows, presence of plants, color, and materiality of the walls and floors, etc.

Other studies assessed the specific impact of wood materiality on psychological well-being, comfort, and stress reduction by comparing physical spaces that were modified in various ways to ascertain behavioural and physiological differences in response to the environment or psychological tests (Tsunetsugu et al. 2007; Ohta et al. 2008; Fell 2010). Fell (2010) compared four identical office spaces apart for their furniture and the presence of plants. The results demonstrated that the presence of wood furnishing reduces occupants’ stress levels, thus inducing more comfort. Wooden furniture offered stress reduction effects similar to those observed during human exposure to natural settings. Ohta et al. (2008) also compared wood to other materials in hospital rooms. The results show that cortisol levels (stress hormone) measured were significantly higher in the conventional room, while the questionnaire results show that the room redecorated with wooden panels was considered more thermally comfortable by occupants, even if ventilation, temperature, and moisture level of both rooms were identical throughout the study. Finally, Tsunetsugu et al. (2007) clarified the effect of wooden interior spaces on physiological health as well as visual comfort, when modifying the amount of wooden surface on walls and floor of three rooms (0%, 45%, and 90% of wooden materials). The measured physiological data showed a significant change of physical responses depending on the wood ratio in the room. Furthermore, the questionnaire results show that the most relaxing and comfortable room consisted of wooden material for 45% of its surfaces.

Wood is thus considered as a “natural” material and generally preferred over other materials. Its use in furniture as well as for walls and floor surfaces creates “restorative” interior ambiences that are warm, pleasant, reduce stress, and enhance psychological well-being and comfort. Nevertheless, wood is available in a remarkable diversity of shades and finishes that create ambiences varying from dark to light and from warmer to colder tones (Jafarian et al. 2016; Poirier et al. 2016). Colors of interior surfaces have an impact on emotional well-being and mood of inhabitants (Chain et al. 2001; Küller et al. 2009; Jalil et al. 2012; Kujisters et al. 2015; Huebner et al. 2016). Therefore, wood finish colors could potentially create ambiences that would modify inhabitants’ perception of the space. Wood surface position (ceiling, floor, walls) as well as its surface to space ratio can additionally create various ambiences that could potentially affect human perception and satisfaction. Finally, in real settings, natural light creates various visual ambiences throughout the day depending on the varying sky conditions and sun path.

The systematic comparison of five wooden scale models different in terms of wooden surface finishes, ratio, and emplacement was conducted by Poirier et al. (2016) based on the results of a previous study (Jafarian 2016). In summary, models with south-east openings were analyzed and compared in terms of hue, brightness, and contrast under the exact same weather and daylighting conditions. Weather data were collected according to cloud cover, cloud thickness, and illuminance. The results showed that sky cloudiness and sun altitude have an impact on visual ambiences: as morning sun fully entering into the scale models created warmer atmospheres, afternoon clear sky without direct sun penetration created colder ambiences, similar to ambience under overcast skies. Furthermore, the interior finish color had a considerable impact on visual ambiences. Yellowish oaked models created warm atmospheres, changing throughout the day and in relation to weather conditions, while grayish models tended to be colder, creating dull and unchanging atmospheres. However, if those studies evaluated the impact of natural lighting diversity on various wooden spaces, inhabitants’ visual perception and satisfaction of these spaces were not studied.

The main objective of this research was therefore to explore the effects of different colors, finishes, and ratio of wooden surface combinations on human perception. More specifically, the research involved simultaneous comparison of five different interior wooden scale models by participants under the natural light of northern latitude in terms of their appreciation, visual comfort, and well-being. Previous research by the authors (Poirier et al. 2016) suggested that the diversity of ambiences created by natural light throughout the day should affect color perception and helped formulate this research’s hypotheses. The main hypothesis states that respondents should perceive and evaluate differently the different wooden scale models. Specific hypotheses state that questionnaire results for participants experiencing spaces under overcast skies and clear skies should show clear differences. Moreover, the remarkable diversity in terms of light and hue, which can be found in the five models, should allow diverse reactions and appreciation levels from participants. The use of an original and specially devised questionnaire allowing qualitative and quantitative assessments adapted to the research context should also allow more comprehensive conclusions.

EXPERIMENTAL

Experimental Settings and Scale Models Description

The light quality of Quebec city (46°49’N) is representative of a Nordic city, characterised with the presence of cold temperatures, ice formations, snow cover, and various types of skies throughout the year. Data collection took place in Laval University School of Architecture parking lot for practical reasons. It offers a South-facing and generous open space, allowing skylight to enter the models’ windows during morning and early afternoon. Figure 1 (right) illustrates the experimental settings featuring five scale models aligned in a south-east orientation for simultaneous visual comparison.

Physical models used in this exploratory research on ambiences were built at a 1:10 scale, determined as relevant since it was demonstrated to produce similar results to a 1:1 scale model in terms of luminous patterns and visual ambiences quality (Lau 1972; Lam 1977). The models were constructed by professional technicians of the Industrial Chair on Ecoresponsible Wood Construction (CIRCERB) under specifications and design established by Jafarian (2016). The selection of the scale model configurations is presented more specifically in previous research (Poirier et al. 2016). The scale models are made with different combinations of wooden panels, using three different colors namely cape cod gray (a gray, neutral, and cold finish), oak (a yellow, warm, and bright finish), and dark walnut (a brown, dark, and neutral finish). Each wooden panel is found in two types of finish: high gloss (90°) and low gloss (12°). White panels are made from white and mat painted melamine. The glass chosen for the models windows is a standard doubled glazing (3 mm clear, 12.7 mm air, 3 mm clear, 80.4% VT) with a neutral color since previous studies prove that this type of glass produces realistic ambience and has less influence on the interior atmosphere (Pineault 2009; Arsenault 2012). Figure 1 (left) shows an observer looking through the scale model’s viewing aperture, in the exterior context.

Fig. 1. Observer looking inside the model (left). Experimental settings with the five scale models aligned in the parking lot, South-East-facing, with observers (right).

The selection of the spatial combinations of wooden panels focuses on the potentialities of finishes to enhance a wide array of architectural ambiences rather than the deterministic validation a unique variable. The selection allowed more flexibility in the use of a combination of variables, while color, gloss, and position are modified simultaneously. Five combinations were chosen according to results from Jafarian (2016) and a pilot study by Poirier et al. (2016). Conclusions of the pilot study determined the research constants:

• Each model should include a wooden floor since it corresponds to the surface where wood is most frequently located or expected;
• The centered front facing wall should be painted white to produce a relatively uniform reference point in terms of light reflection and hue; and
• The space should include a proportion of wooden surfaces situated between 35% and 85%. Figure 2 shows the selection and concepts of each physical model that were observed and compared by the participants.