In the survey, carried out by Lisboa E-Nova – Lisbon Energy and Environment Agency, 63.2% of respondents reported sometimes feeling thermal discomfort inside their homes in winter and 56.5% in summer.

Around a quarter of participants reported feeling this discomfort often, in both seasons, according to a statement summarizing the main results of the survey of the population residing in Lisbon aged 25 or over, conducted at three different times (summer 2022 and 2023 and winter 2023).

Participants in difficult or very difficult financial situations reported feeling too cold or too hot at home more often, with more than a fifth (22.0%) reporting not having the financial capacity to keep their home at a comfortable temperature during the winter months, a higher number than Eurostat's for Portugal (20.8% in 2023).

Among the most common problems in homes identified by the people interviewed are poor insulation of windows or doors and the presence of humidity and fungus/mildew. In summer, it becomes impossible or difficult to ventilate houses.

The research also points to a relationship between the period of construction of the house and thermal discomfort, which is more present in older houses (pre-1960), typically without insulation.

In winter, 95.3% of participants use some type of low-efficiency electric heater, with central heating being an option for only 6.7%, and only a fifth of the sample indicated having double glazing at home.

A third of the people interviewed reported having air conditioning installed at home, but only 13.1% use it whenever they need to.

More than a fifth of the people interviewed indicated that the cold at home affects the quality of their sleep – a percentage that rises to more than half in the summer –, in addition to making it difficult to study, read or write and use a computer.

Around 30 to 40% of people interviewed had never heard of support programs to improve housing energy efficiency, warn the authors of the survey, highlighting that "a detailed vision" is essential for the development of effective public policies.