# Monitoring a Pre-Normative Multi-Family Housing Case-Study in a Mediterranean Climate
## 1 Introduction  
The current housing stock is responsible for almost 40% of the global amount of energy used in the European Union and a third of CO\({}_{2}\) emissions. Sixty-one percent of the existing Spanish residential stock [1] was built before the first mandatory regulation on thermal conditions in buildings NBE-CT 79 [2]. This code was supposed to be applied to every new construction, regardless of the final use. Limitations concerning U-values of the thermal envelope, depending on the different climate zones, were established, except for the windows. Moreover, the global heat transmission coefficient of buildings was also defined; this relies on the building's compactness and the energy system used for heating. The transposition of Directive 2002/91/CE motivated a legislative change through the establishment of the Basic Document on Energy Saving from the Spanish Technical Building Code (CTE DB-HE1). This document provided new requirements for the building's thermal envelope, by limiting U-values for the opaque elements and for the transparent elements and stating limitations for the modified solar factor of the windows. Subsequently, due to the modifications driven by Directive 2010/31/UE, the Basic Document on Energy Saving, DB-HE1 2013, was updated in order to comply with the aims of Horizon 2020. Previous existing housing stock failed to comply due to insufficient thermal insulation in buildings' envelopes. This indicates deficient environmental behavior regarding present energy standards,which results in an excess in energy consumption and CO\({}_{2}\) emissions for the maintenance of a minimum level of indoor comfort and habitability in the dwellings. Hence, European [3] and Spanish [4] energy policies treat the retrofitting of existing building stock as a major issue, especially concerning housing due to its potential for improvement. Current residential stock has already been the focus of several studies related to its environmental performance thanks to its potential in energy savings. These studies: examine classification methods of the housing stock; study in situ data collection by monitoring environmental parameters and electricity consumption; analyze the composition of thermal envelopes and carry out research into the impact of user behavior on the energy and environmental performance of a dwelling. The classification and characterization of building facades [5] and typologies [6] has enabled the analysis of the existent casuistry and their knowledge; therefore, the constructive system that belongs to a city, a region or a country can be represented, and useful tools have been developed that can be used to seek and propose the optimal retrofitting solutions that are suitable for each case [7]. The proposal of standard solutions and their applications has also been analyzed in several studies, at a national level in the Spanish residential stock [8], as well as in other international locations [9; 10; 11; 12], under various environmental and climate conditions. These aspects have an impact on the energy performance of buildings, and therefore, there is a need to establish similar guidelines to intervene in buildings that share the same climate zones at the European level [13]. Retrofitting strategies that aim to revise the state of the art of passive cooling and thermal dissipation in existing buildings and their contributions towards improvements in indoor air quality and the reduction of energy demand have also been considered as suitable for implementation to resolve the deficiencies in this social housing stock [14; 15]. The acknowledgement of the current state of these residential buildings constitutes a key element when considering any kind of intervention in buildings. There is a shortage of information on environmental variables and on energy demand extracted from field tests undertaken in real use and operative conditions, especially in Mediterranean areas.