Historical and future LCA insights on tiny houses vs conventional housing typologies in Denmark

• Timeseries carbon footprint of tiny houses, apartments, and houses from 1970 to 2050. • Temporally adjusted LCA (future and past) with foreground and background scenarios. • Assessment of both ambitious and pessimistic future scenarios. • Importance of using a per-person functional unit to emphasize reduced consumption. • Tiny houses have lowest climate impact in 2035–2050, if access to district heating. The building sector is a significant contributor to global greenhouse gas (GHG) emissions, necessitating sustainable solutions informed by robust environmental assessments. Given Denmark’s goal of reducing GHG emissions in 2030 by 70% compared to 1990, it is relevant to investigate the potential in the sector of residential buildings. This study evaluates the historical and prospective life-cycle greenhouse gas emissions of tiny houses, apartments, and single-family homes in Denmark using temporally adjusted (prospective and historical) Life Cycle Assessment (LCA). The analysis also considers the evolution of heating technologies, revealing a slowing rate of improvement, which underscores the urgency for complementary solutions. Historical data (1970–2020) and future scenarios (2035, 2050) were modeled under Shared Socioeconomic Pathways (SSP). The study brings novelty to the field by being the first to combine historical and prospective analysis, providing new perspectives on decision support. These insights can aid policy-makers in enabling green transition of Danish houses and supporting the development of tiny house movements. Results indicate that tiny houses currently outperform other housing typologies due to lower embodied energy and material use. While operational energy emissions across typologies converge by 2050, tiny houses maintain an advantage with significantly lower embodied impacts. If supported by green technologies such as district heating and ground-source heat pumps, tiny houses could achieve approximately half the GHG emissions of apartments by 2050. However, as renovations improve the energy efficiency of existing building stock, the relative benefits may decline. A key finding is the necessity of shifting the sustainability assessment metric from “per square meter” to “per person,” reflecting the critical role of consumption patterns. Tiny houses exemplify this shift, assuming half the living space per person and enabling significant reductions in material and operational energy demands. This underscores that technological advancements alone are insufficient to meet sustainability goals without behavioral changes and reduced consumption. To realize the potential of tiny houses as a transformative housing solution, urgent policy support for green heating technologies is essential. By coupling historical insights with future projections, this study provides valuable guidance for shaping policies that break free from outdated paradigms and foster sustainable practices in the built environment.