While some people turn up the heating in their homes during the cold winter months to even warmer than in summer, others value indoor air quality more than temperature. Martin Thalfeldt, a researcher in the Nearly Zero Energy Buildings research group, Programme Director of Indoor Climate and Water Technology, and Associate Professor, belongs to the latter group. He shares his thoughts and experiences to encourage and inspire members of the university community to adopt more sustainable everyday habits. In January, the focus of the Sustainability Months is on heat and light – that is, buildings' energy.
What principles guide how you manage heating, ventilation and lighting in your home across different seasons?
Our family lives in an apartment where heating can be regulated with thermostats and fresh air is supplied by an apartment-based heat recovery ventilation unit. During winter, we maintain an indoor temperature of around 21–22°C; in spring we turn the room thermostats down to the minimum and increase them again in autumn. Ventilation generally runs continuously, but this winter I have reduced the daytime airflow to prevent relative humidity from dropping too low. Lighting is used as needed, although we occasionally need to remind the younger members of the family to switch off lights in rooms that are not in use.
In summer, when it starts to get hot, we keep the windows open. However, airing only cools the apartment and its structures if the outdoor temperature is lower than indoors. Air movement cools us because our bodies are warm and we sweat. Building structures do not sweat and during heatwaves draughts tend to heat rather than cool the apartment.
What motivates you to consider air quality in addition to indoor temperature?
The simple answer is good health and sleep quality. Personally, I can clearly feel the effects of poor ventilation in the mornings. There is also a degree of professional bias involved. In my indoor climate course, students measure air quality in their own homes and many discover how poor the conditions are in their bedrooms. As a result, they genuinely change their window-opening habits and achieve a better quality of life.
In addition to their homes, students measure indoor climate conditions at school and at work. Based on their presentations, I have made suggestions to our real estate department. But overall, air quality in auditoriums is quite good and there is no significant negative impact of polluted air on learning outcomes.
Many people prefer to wear short sleeves indoors even in winter, while in summer they step into cooled spaces. How do you cope with changing temperatures?
I must admit that at home I am comfortable wearing light clothing at 21–22°C and, for reasons of convenience, have not taken the initiative to lower it further. The associated “energy cost” would likely be greater than any real energy savings achieved. I have not particularly noticed excessive cooling in Estonia, but overheating does occur.
Share one good energy-saving tip for those who cannot adjust the indoor temperature in their homes.
If it is not possible to adjust the indoor temperature at home, then this option should be created, as such solutions have been standard practice in building construction for decades and are reasonably priced. The potential energy savings, as well as the benefits for health and quality of life, are substantial and the payback period can be measured in months rather than years.
Measure the sustainability of your lifestyle using the lifestyle test here.
Learn how to contribute to reducing your environmental footprint on the Sustainability Months page, in TalTech’s Green Guide, and in the Government Office’s Green Behaviour Toolkit (in Estonian).