THERMAL TRANSFORMATION: Indoor environmental retrofitting with passive solutions

PhD project by Mette Boisen Lyhne

In contemporary Danish renovation practice, the energy consumption of houses is a major focus. However, it is shown that a significant energy reduction results in new challenges regarding the thermal environment. This Ph.D.-project intends to investigate how future retrofitting can improve the thermal environment and comfort by taking into account the specific house type, original architectural properties and passive solutions.

In Denmark, an average of 16 hours a day is spent within the home. Therefore, the indoor environment of our houses is of utmost importance to our health and well-being.

Foto: Anders Sune Berg / Realdania By og Byg

While energy retrofitting can alleviate some problems with the indoor environment, it has simultaneously introduced new problems. Research has recently revealed a shift in challenges regarding the thermal environment in Danish houses over the past decades. A survey by Realdania and Bolius shows that houses built before 2000 typically have problems with draught and cold, whereas houses built after 2000 tend to have the opposite problem – overheating.

This problem is also current in energy-retrofitted houses. Here it usually occurs due to a highly sealed, insulated façade – a renovation procedure that often requires installation of a mechanical ventilation system.

So-called passive solutions, such as natural ventilation systems, typically control heating and cooling and thus have an impact on the indoor environment and thermal conditions. At the same time, they can minimize energy use. However, only limited research has focused on the potential of using passive solutions to improve the indoor environment.

This Ph.D.-project investigates whether there are passive solutions to be (re)found in the houses of the past, such as architectural features that can improve the thermal environment. The focus will be on four types of Danish single-family houses from the 20th century; murermestervillaen, funkishuset, statslånshuset and parcelhuset.

They were all built before energy requirements were implemented and thus do not live up to today’s standards in terms of energy use. Therefore, they are most likely next in line for energy retrofitting. The four house types will form the basis of a case study, in which different architectural features will be analyzed and their relevance to the thermal environment will be discussed.

The project seeks to unfold the potential of passive solutions and thus provide inspiration for future retrofitting focusing on the indoor environment.