Rising temperatures are leading to an increase in the cooling demand of buildings. Electrochromic (EC) glazing can be a promising solution for controlling solar heat gains while maintaining outdoor views. This paper presents the results of the monitoring of prototype panels of a novel type of inkjet-printed EC glass under real use and weather conditions in a small office building in the Netherlands. This building contained two identical west-facing meeting rooms of which one was equipped with EC triple glass IGUs and the other with normal triple glass IGUs. Each room was equipped with local heating/cooling units of which the energy use was monitored, and with an extensive environmental sensor network. Sensor and calendar data was fed into an energy balance model for each of the rooms for the entire measurement period, allowing to correct for differences between the two rooms with respect to heat losses and gains and use conditions. The results of the monitoring showed that in the meeting room with EC glass IGUs, the heating demand increased by 34% in Jan.-Mar. 2024 while in Sept. 2023 the cooling demand decreased by 3%. The main reason for the increase in heating demand was found to be the lower g-value of the EC glass IGUs in clear state as compared to the normal IGUs. The almost similar cooling demand was a result of a trade-off between the lower direct solar transmittance of the EC glass IGUs and the heating up of the absorptive layer inside the IGUs. Furthermore, an experiment with participants showed that in general in dark state, satisfaction with view clarity, daylight colour and daylight availability was higher for the EC glass IGUs. In transparent state, no significant difference was perceived between the EC glass IGUs and standard IGUs, except for view clarity.

Postwar terraced houses, built en masse for the European middle-class, remain a major consumer of energy, significantly affecting the performance and quality of the residential stock. Prêt-à-Loger is a net zero energy refurbishment (NZER) concept addressing 1.4 million postwar Dutch terraced houses and possibly some other 30.6 million spread throughout NorthWestern Europe. By applying an integrated external renovation system (called “the skin”), the house becomes energy neutral while at the same time the living quality and the durability of the house are improved, and extra space is added. This non-invasive renovation project competed at the Solar Decathlon Europe 2014, winning five prizes, among which the first in sustainability. Despite the easy and fast applicability, the financial aspect still presents a serious barrier for large-scale implementation of this and other energy neutral renovation concepts. The research summarised in this paper firstly identifies the economic factors that can boost the investment in energy neutral refurbishments, on the basis of interactions with public and local authorities, private companies, research institutes and end-users. Secondly, it studies the economic potential of the NZER and the relative importance of the identified factors with Monte Carlo simulations. Different cases are considered to address the situation of single homeowners as well as housing associations needing to refurbish multiple dwellings. The increase of total rent after renovation for the housing association case and the energy prices for the homeowner case are the most influential factors together with the capital expenditures; the maintenance cost and increase of property value are also relevant elements that can be affected by the right design choices. For the Prêt-à-Loger solution, for instance, a higher increase of property value is registered in comparison to other energy neutral renovation concepts. These findings provide an important support and inspiration for designers and decision makers operating in the field of deep energy retrofit.

There are many smart technological solutions on the market for the zero energy refurbishment of the current building stock. The Delft University of Technology developed a zero energy renovation concept addressing 1.4 million postwar Dutch terraced houses: Prêt-à-Loger. By applying an integrated external renovation system (called the skin), the house becomes energy neutral while at the same time the living quality and the durability of the house are improved. This non-invasive renovation is designed to be applied to multiple houses. The project competed at the Solar Decathlon Europe 2014, winning five prizes, among which the first in sustainability. However, the team did not stop there; research continued in order to apply the concept in practice.

Despite the easy and fast applicability, the financial aspect still presents a barrier for large-scale implementation. This paper addresses the economic factors that can activate the investment on energy neutral house refurbishments. It summarizes the outcome of one-year interaction with public and local authorities, private companies, research institutes and end-users. The conditions created today by local subsidies and regulations for investments to take place are also addressed. Finally, the aspects that increase the value of the house, stimulating the investment are analysed.