Turning Low-Density Neighbourhoods into Climate Assets

Building cities inward rather than outward is widely promoted as a sustainable planning strategy—one that limits sprawl, protects green areas, and makes better use of existing infrastructure (Næss et al., 2020). Yet for many municipalities, translating this ambition into day-to-day planning decisions remains difficult. While Finland’s Land Use and Building Act (1999) commits planning to sustainable development, it provides limited guidance on how to implement these goals in low-density, single-family housing areas, which continue to dominate much of the urban landscape. Here, planning choices matter. Housing typologies strongly shape the amount, quality, and function of residential greenery (Leppänen et al., 2024). Detached housing areas can either intensify surface sealing, biodiversity loss, and climate risks—or, if planned strategically, become key sites for nature-based stormwater management, habitat connectivity, and climate adaptation (Tahvonen, 2018a; 2018b). Although tools such as green factor requirements, limits on impermeable surfaces, and the 3–30–300 rule are increasingly cited in policy discussions, their uptake across Finnish municipalities remains uneven, particularly in single-family housing areas where implementation is most challenging. Against this backdrop, the ILPI project positions housing typology as a concrete and scalable policy lever for embedding sustainability goals into everyday planning practice. By linking typology to participatory, practice-based planning, municipalities can move from abstract sustainability targets to spatially specific and enforceable solutions. This blog outlines how housing typology can function both as a diagnostic tool and as a guiding framework for the sustainable densification of detached housing areas—offering planners and decision-makers a practical way to turn sustainability commitments into on-the-ground action. Housing typology is a way of understanding housing based on its physical form, layout, and relationship to its surroundings—not by ownership, tenure, or social group. For planners, typology offers a practical language for identifying recurring housing forms and comparing how they perform in different contexts. In the ILPI project, housing typology is used as a diagnostic/anayltical planning tool. As shown in Figures 1 and 2, a standard 200 × 200 metre area is analysed by breaking it down into blocks and plots, and by identifying the housing types built on each plot. Key surface areas—buildings, paved and impermeable surfaces, roads, lawns and meadows, and tree-covered areas—are calculated alongside estimated resident numbers. The aim is not perfect precision, but comparable and decision-relevant data that allows different housing types to be assessed side by side.

Each typology is presented as a typology card, combining spatial and quantitative information in one clear format. The card includes:
(A) an isometric view showing building heights and massing;
(B) a simplified plan of the area;
(C) an aerial image paired with a street-level view; and
(D) key land-use figures, such as floor area, sealed surfaces, green areas, and tree cover, as well as efficiency indicators at plot, block, and area level.

Building on the typology analysis, the spatial arrangement of housing forms is assessed to identify scalable design principles that support green infrastructure continuity. One key finding is that the alignment of private backyards across adjacent plots can create continuous ecological corridors at the block scale. These corridors strengthen urban biodiversity, improve nature-based stormwater management, and measurably increase green factor performance. Embedding such layout principles in local planning frameworks enables municipalities to translate high-level EU sustainability objectives—such as biodiversity protection and climate adaptation—into concrete, plot-level implementation (see Figures 3 & 4).

As households prioritise low-maintenance yards, hard surfaces increasingly replace greenery, weakening climate adaptation at the neighbourhood scale. The policy response is clear: planning and zoning must make green plots work as public infrastructure, aligning household decisions with collective environmental gains. The ILPI project shows that sustainability tools only become effective when they are developed together with those who use them. Close collaboration between researchers and municipalities—here, Pori and Joensuu—was essential to grounding research in local realities and turning abstract sustainability goals into workable planning tools. This co-production approach ensures that new tools are not only evidence-based, but also practical, adaptable, and ready for implementation. Finally, the typology study presented here is proposed as a concrete planning tool for the smallest yet most decisive scale—the plot—supporting the systematic enhancement of green factors, the reduction of impermeable surfaces, and the application of the 3–30–300 rule in everyday zoning and densification practice.

Author: Hossam Hewidy, DSc (Architecture), Senior Lecturer

The author would like to thank Lecturer Tommy Lindgren and Research Assistant Tiia Lassila, members of the Aalto University research team in the ILPI project, for their valuable contributions to the typology study.

References 

Leppänen, P. K., Kinnunen, A., Hautamäki, R., Järvi, L., Havu, M., Junnila, S., & Tahvonen, O. (2024). Impact of changing urban typologies on residential vegetation and its climate-effects – A case study from Helsinki, Finland. Urban Forestry & Urban Greening Volume

Næss, P., Saglie, I.-L., & Richardson, T. (2020). Urban sustainability: is densification sufficient? European Planning Studies, 28(1), 146–165. https://doi.org/10.1080/09654313.2019.1604633

Tahvonen, O. (2018a). Adapting Bioretention Construction Details to Local Practices in Finland. Sustainability, 10(2), 276-. https://doi.org/10.3390/su10020276

Tahvonen, O. (2018b). Scalable Green Infrastructure—The Case of Domestic Private Gardens in Vuores, Finland. Sustainability 10, no. 12: 4571. https://doi.org/10.3390/su10124571