Tanzanian survey upends assumptions on sustainable building material choices

Construction professionals in Tanzania rank environmental performance above cost when choosing materials for residential buildings, according to a survey-based study that challenges a long-standing assumption about decision-making in developing countries. The research, published in the journal Architectural Intelligence, surveyed registered architects, engineers and quantity surveyors in Dar es Salaam and Dodoma and found that material environmental impact, ecosystem protection and waste management topped the list of priorities, ahead of every economic consideration.

The finding matters because the built environment is a major contributor to climate change. The study cites figures showing that the construction sector accounts for roughly 39 percent of energy-related carbon dioxide emissions and 36 percent of global final energy consumption, with building materials alone responsible for about 11 percent of annual emissions. Life-cycle assessments have suggested that strategically substituting high-carbon materials such as cement and steel with alternatives like stabilised earth blocks, bamboo composites and recycled aggregates could cut project-level emissions by up to 40 percent while maintaining structural performance.

The research team, led by Constant Mahame with colleagues including Geraldine J. Kikwasi, Modest M. Baruti and Olukanni O. David, built the study on an earlier systematic review that had identified 19 factors influencing sustainable building material selection across environmental, economic and socio-cultural dimensions. That review, however, could not say which factors mattered most in any specific context, and it offered no operational tool for translating the factors into practical guidance. The new study set out to close both gaps in Tanzania, a rapidly urbanising country where housing demand is rising sharply.

The researchers distributed a structured questionnaire to 326 registered construction professionals and received 156 usable responses from architects, engineers and quantity surveyors with residential project experience. The sample was drawn from a registered population of 2,115 professionals across the two cities, with the required sample size calculated using Cochran’s formula at a 95 percent confidence level and a 5 percent margin of error. Respondents rated each of the 19 factors on a five-point importance scale, and the team computed a Relative Importance Index for every factor within a triple bottom line framework covering environmental, economic and socio-cultural dimensions.

The instrument proved highly reliable. Cronbach’s alpha for the overall 19-item scale reached 0.974, well above the 0.70 threshold conventionally treated as acceptable, with the individual environmental, economic and socio-cultural dimensions each scoring above 0.94. All items showed strong corrected item-total correlations, and none warranted deletion. The rankings that emerged were striking: all seven environmental factors exceeded the high-importance threshold, with index values ranging from 0.838 to 0.906, and material environmental impact achieved the highest score of all 19 factors at 0.906, followed by ecosystem protection at 0.873 and waste management at 0.872.

Economic factors occupied the middle ranks, from ninth to fourteenth place, though all five still reached the high-importance classification with index values between 0.783 and 0.832. Notably, life-cycle cost, which encompasses initial investment, operations, maintenance and end-of-life disposal, ranked above simple affordability, suggesting that these formal-sector professionals think in terms of total cost of ownership rather than first-cost optimisation alone. Market availability and accessibility was the highest-ranked economic factor at 0.832, reflecting practical realities in a market where supply chains for sustainable alternatives remain fragmented and specialised materials may need to be imported.

Socio-cultural factors clustered at the bottom of the rankings, with six of the seven falling between index values of 0.719 and 0.781. The clear exception was health and safety of users, which ranked seventh overall at 0.840, above all economic factors and most environmental ones. The authors attribute this to the dual character of health and safety as both a social concern and a regulatory requirement, enforced in Tanzania through the Occupational Health and Safety Act of 2003. Participatory factors fared worst, with stakeholder involvement scoring 0.719 and collaboration and knowledge sharing 0.746, and these factors also drew the widest disagreement among respondents, with the highest standard deviations in the dataset.

The survey also revealed a knowledge-experience paradox. Some 78.2 percent of respondents rated their knowledge of sustainable building materials as good or better, yet 23 percent had never worked on a project using such materials, and only 12.2 percent reported extensive experience of more than 15 projects. Most respondents preferred that sustainable materials be considered at the design development stage, at 41.7 percent, or integrated across the whole life cycle, at 37.2 percent, with almost no support for starting at construction or later phases. The authors note that self-reported knowledge may be vulnerable to overconfidence, and that the dominance of conventional materials continues to limit opportunities to apply alternatives regardless of awareness.

Translating the rankings into practice, the team developed a weighted evaluation matrix organised as a flowchart for early-stage material selection, positioned as a pre-multi-criteria decision-making tool for the schematic and concept design stages, when material specifications are first formulated and substitution remains feasible without cost penalties. Within the framework’s three domains, the 12 high-importance factors, comprising all seven environmental factors, three economic factors and two socio-cultural factors, function as mandatory gating criteria that a candidate material must satisfy; failure on any one disqualifies it. The remaining seven medium-importance factors contribute to a weighted composite score within their domain, using each factor’s index value as its weight, and the composite must reach at least 0.60. The framework deliberately relies only on information already available in early design, such as material costs, basic performance specifications and socio-cultural compatibility, rather than data requiring laboratory testing or specialist databases.

The authors are careful about the limits of their findings. The rankings rest on self-reported importance ratings, which may partly reflect socially expected priorities rather than actual selection behaviour, and high internal consistency does not rule out acquiescence in responses. The sample covers registered professionals in two cities and excludes the substantial informal construction sector, which may prioritise factors differently. The descriptive approach identifies perceived importance but does not quantify trade-offs or optimise choices, so factor weighting and threshold calibration remain unresolved. The authors recommend applying formal multi-criteria methods such as the Analytic Hierarchy Process and validating the framework through case-based applications, including testing whether these priorities transfer to other developing-country residential construction sectors. They also suggest policy steps flowing from the findings, including requiring environmental performance documentation in public procurement and building participatory competencies into professional training, since the marginalisation of stakeholder engagement points to a specific gap in current technical curricula.

Subject of Research: Empirical prioritisation of sustainable building material selection factors among construction professionals in Tanzania

Article Title: An empirical framework for sustainable building materials selection in residential construction: evidence from Tanzania

Article References: Mahame, C., Kikwasi, G. J., Baruti, M. M., & David, O. O. (2026). An empirical framework for sustainable building materials selection in residential construction: evidence from Tanzania. Architectural Intelligence, 5(1), Article 22. https://doi.org/10.1007/s44223-026-00132-8

Image Credits: AI Generated

DOI: 10.1007/s44223-026-00132-8

Keywords: sustainable building materials, Tanzania, residential construction, Relative Importance Index, triple bottom line, life-cycle cost, construction professionals survey, decision-support framework, environmental impact, health and safety, developing countries, embodied carbon