Difficulties in the energy renovation processes of district heating buildings. Two case studies in a temperate climate

 

1. Introduction

To achieve a low-carbon economy and low carbon cities in 2050, it is essential to take into account building stock since it involves 40 % of the world's total energy use and 30 % of CO2-emissions (Statistical Office of the European 

In this way, a lot of countries have had a strong focus on the energy efficiency of new buildings during the last few decades. However, the building stock is relatively old and the replacement rate is low: for example, in Spain –where this study is developed– it is estimated by the INE that 70% of the housing stock to be used in 2050 has already been built and between 63% and 76% of the existing housing stock was built before the first energy demand regulations of buildings NBE CT-79

Therefore, the energy rehabilitation of buildings is essential, and in order to guide these processes, the European policy framework aims to create the conditions and guidelines for improving the energy efficiency of existing and new buildings . Research analysing the energy efficiency and renovation of buildings is typically focused on single buildings . However, due to the increasing complexity of the infrastructure regarding generation, distribution and use of energy, the single building perspective can lead to sub-optimization for the community or society as a whole. Furthermore, focussing on entire neighbourhoods could be beneficial through economies of scale, higher levels of efficiency in relation to use of resources, minimization of waste  and the greater potential they have for implementing renewable energies . Nevertheless, systems as complex and large as District Heating (DH) involve long rehabilitation processes in which barriers and challenges can appear. Because of that communities of neighbours cannot want to carry out this type of process. In particular, some social groups (those with low-income, renters, or the elderly) experience more barriers for undertaking a building retrofitting due to factors such as upfront costs, “presentism” thinking, split incentives, disruption and lack of control 

2. Methodology

The methodology carried out includes the study of the energy rehabilitation project and the analysis of the situation after completing the rehabilitation process of the envelopes.

2.1. Case studies description

The selected case studies are located in Pamplona, a city in the North of Spain. Both buildings were built in 1971, that is, before the first Spanish regulation on energy saving NBE-CTE-79. so they were built without insulation in the thermal envelope (see envelopes’ original characteristics. They were selected because both belong to two different District Heating and are representative of two residential block typologies of this period in Spain: linear block (S1) and high-rise building (T2). Both buildings were rehabilitated within the context of the Efidistrict Fwd project promoted by the Government of Navarra and the public housing company, NASUVINSA

lthough the neighbour's profile is varied, almost half of them are people over 65 years old and retired, with one or two persons per dwelling. Almost 50% of them are the first generation of people who lived in these buildings built in the 1970 and dwellings are all privately owned.

2.2. Climate

Pamplona has a Cfb climate (according to Koppen-Geiger classification), temperate without dry season, "oceanic" type. Following data from the 1980-2010 climate series of the Spanish State Meteorological Agency (AEMET) the average annual temperature is 12.7°C: January is the coldest month with a monthly average of 5.2°C and a monthly average minimum of 1.4°C, and August is the warmest month. According to the same climatic series, the annual average relative humidity is 67%: December and January are the wettest months (with a monthly average of 78% RH) and July and August are the driest months.

2.3. Typology and distribution

Case study S1 is a building in linear typology between two blocks and with 5 floors (Ground floor+4). It is configured with 2 dwellings per floor with double orientation (8 dwellings in total per block), and commercial areas on the ground floor. The main orientation is Northwest (NW) and the secondary orientation to a semi-opened courtyard is Southeast (SE). The heated area of each dwelling is 70.10 m2 and its layout consists of kitchen (K), living room (LR), bathroom (T), three bedrooms (BR) and a balcony