Simulation-Based Assessment of Urban Heat Island Mitigation Strategies on Energy Performance and Adaptive Thermal Comfort in Vietnamese Row Houses

Overview

This article summarizes published research on how the urban heat island (UHI) effect influences cooling energy and indoor thermal comfort in Vietnamese row houses, and how building performance simulation can be used to assess mitigation measures. It does not report new simulations. Only one of the cited studies deals directly with Vietnam (Hanoi); the others come from Europe, the United States and the wider humid tropics and are included for method and context.

Row houses and the urban heat island

Row houses (nhà ống, "tube houses") are narrow, deep buildings that share party walls with their neighbours and have openings mainly at the front and sometimes the rear. A study of Hanoi cites an estimate that about 69% of the building stock in Vietnam is made up of 3-5 storey row houses (Parkes, 2013, as cited in ¹). The same study notes that a warmer urban climate is expected to make thermal comfort by natural ventilation harder to achieve in these buildings, pushing occupants towards air conditioning ¹.

The closed, attached arrangement of row houses also makes it difficult for wind to enter, especially in small units. A systematic literature review on wind flow in row houses in the humid tropics found that most building performance research has focused on public buildings, with little specific work on row houses. Elements such as stilt floors, stairwell voids, air wells, facade ventilation and roof openings were identified as under-researched ².

Evidence from Hanoi

Trihamdani and colleagues combined urban climate simulation (WRF) with building simulation (TRNSYS) to evaluate UHI effects on a row house in Hanoi ¹:

Implementation of the Hanoi Master Plan 2030 was predicted to increase the number of hotspots and raise air temperatures in built-up areas by up to 2-3°C.
The large, centralized green spaces proposed in the master plan were found to be less effective in reducing UHI than smaller but equally distributed green areas of the same total size.
If a row house in a rural area becomes part of the urban area as the city expands, its indoor operative temperature was predicted to increase by up to 1.6°C.
After implementation of the master plan, the cooling load was predicted to increase by up to 179%.

These results come from one simulation study and depend on its scenarios and building model, but they indicate that urban form and green space distribution can matter for row house comfort and energy use.

Mitigation measures and simulation methods

Mitigation can act at the urban scale and at the building scale:

Urban scale: Work on Central European cities assessed UHI mitigation scenarios in an urban modelling environment, ranked the measures by their effect on urban climate indicators, and calibrated the simulation against on-site weather station data for a control area in Vienna, Austria ³. The Hanoi study similarly tested the layout of urban green space ¹.
Building scale: An EnergyPlus study of residential reference models in Miami, Baltimore and Chicago found that energy conservation measures such as cool coatings, heat pumps, additional insulation and energy-aware occupant behaviour strongly reduced heat emissions from buildings to the ambient air, although these reductions were not always proportional to reductions in energy use ⁴. Cool roofs, green roofs and facade greening are other building-scale measures commonly discussed for hot climates; their performance in Vietnamese row houses has not been established by the sources cited here.

For a simulation study of row houses in Vietnam, typical ingredients would include a weather file that reflects urban rather than rural conditions (for example from coupled urban climate modelling, as in ¹), a model of the attached row house with realistic openings and party walls, natural ventilation and air conditioning schedules, and comfort metrics suited to naturally ventilated or mixed-mode buildings, such as an adaptive comfort model.

Considerations for Vietnam

Planning and building scales interact: The Hanoi results suggest that how green space is distributed across the city affects the conditions individual row houses experience ¹.
Ventilation design is under-studied: The row house wind-flow review points to stairwell voids, air wells and roof openings as research gaps ².
Local evidence is limited: Quantified savings from cool roofs, green roofs or facade greening in Vietnamese row houses need dedicated studies, ideally validated with field measurements.
Practical constraints: Structural capacity, maintenance, water for irrigation and cost will affect whether green roofs and facades are feasible for individual households.

Conclusions and research needs

Available evidence indicates that UHI can raise indoor temperatures and cooling loads in Hanoi row houses, and that urban green space layout influences the result ¹. Building-scale mitigation measures have been studied mainly outside Vietnam ⁴. Research needs include building-level simulation of mitigation measures for Vietnamese row house typologies in several cities, ventilation elements suited to narrow attached houses ², calibration against measured data ³, and cost analysis under local conditions.