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Energy and environmental rehabilitation of the Amara neighborhood in San Sebastián.
In this post we will make a summary of a study carried out by Aurea Consulting and Factor 4 for the energy and environmental rehabilitation of the Amara neighborhood in San Sebastián, and which is part of the Plan to Combat Climate Change, within the II Action Plan Local of the Local Agenda 21 and the commitment made by the city of San Sebastián to reduce its CO2 emissions by 20% by 2022.
Objective of the rehabilitation study.
It is intended to know the environmental and social problems that energy renovation entails in this neighborhood of San Sebastián with the purpose of developing strategies to promote energy rehabilitation in the city from the analysis of a representative building that allows extrapolating the results obtained to the rest of the neighborhood. The most notable aspects of this study include the following points:
Current state of the analyzed building.
A block is analyzed that presents some characteristics of the envelope, number of floors, construction quality, layout of patios, orientation etc … very widespread in the neighborhood and therefore is considered representative. Among these similarities, it stands out that they are buildings built before 1980 and with practically no minimum thermal insulation. In the first part of the study, the characteristics of the climate of San Sebastián are analyzed, considering that it has a mild climate, very rainy but without extreme temperatures in winter or summer. To evaluate the current state of the building, energetically speaking, it is modeled and simulated and on the other hand a data collection is carried out in situ.
Modeling and simulation:
To make the three-dimensional model of the building, its geometry and construction characteristics were defined using Designbuilder Energyplus, in order to estimate the annual energy demand of the building, which was about 70 Kwh / m2. The results concluded that the demands of the houses on the first and last floors were notably higher than around double to triple that of a house located on an intermediate floor and about 15% lower in the houses facing south in relation to the facing north.
The study of solar radiation as well as wind and pressure was also carried out, which demonstrate the negative influence exerted by the surrounding buildings on the sunlight received and also the parts of the building most exposed to the wind. With the LIDER program it was found that its demand did not comply with the demand limitation of DB HE 1 of the Technical Code, since it was 128% above that of the reference building and an energy rating D was obtained with the Calener VYP program.
Data obtained in situ.
In order to support the results obtained in the simulation and verify the most deteriorating areas of the thermal envelope that allow detecting the points susceptible to improvement, we proceeded to collect information in situ, as is done in an energy audit, resorting to the following actions:
Analysis and study of energy billing.
In this way, the real energy consumption was obtained from the bills so that, comparing them with those obtained in the simulation, they were quite approximate figures.
Monitoring in homes.
Temperature and humidity sensors were installed in the different rooms of the building's dwellings in order to compare them with the results obtained in the theoretical simulation from the monitoring data. With this analysis, it was possible to verify the existing decompensation in the winter months between the houses facing North and those facing South, as well as that between houses with upper and lower floors and those with intermediate floors.
Thermography.
The thermography allowed to detect the areas of the facade with thermal bridges and those where the energy losses are greater, highlighting that the greatest losses were located at the junctions of the facades with pillars and slabs, as well as the areas or facade panels where the niches for placing radiators under the windows.
Improvement proposal for the building.
Envelope improvement.
The recommended thermal insulation thicknesses are between 6 to 8 cm. on facades and from 9 to 12 cm. on decks.
The great effect produced by glass in intermediate plants stands out in the study, since a reduction in energy consumption of between 10 to 20% is achieved, being enough to replace it with a double glass without having special characteristics such as a low emissive.
The recommended position of the insulation to reduce thermal bridges concludes that it is more efficient when placed outside because in this way the temperature of the enclosure is kept closer to that of the interior environment, avoiding the appearance of possible condensation.
Adopting the minimum improvements required to comply with the ordinance, that is, placing 3 cm. insulation on the facade, 8 cm. on deck and 6 cm. on the ground, together with the replacement of the glass with a double 4-12-4 glass, allows achieving energy savings of up to 60% in some homes.
Improvement of facilities.
The most important deficiencies found in the building after the on-site tests include, on the one hand, the lack of thermal insulation of the uprights in the distribution network, and also in the DHW pipes inside the homes. Likewise, a significant diversity of models and degrees of age is detected in the emitters and due to the lack of knowledge of the users in the operation of the radiators, an imbalance in the flows in the homes is generated due to lack of adjustment of the holders of the amounts.
Most important conclusions of the energy rehabilitation
The most efficient solution is to incorporate thermal insulation through a sheathing on the outside, which eliminates thermal bridges and reduces the possibility of condensation, obtaining adequate thicknesses of 6 to 8 cm. on facades and from 9 to 12 cm. in roofs with reasonable amortization periods, so that any intervention must be carried out globally at the community level. Therefore, Incorporating energy criteria into a rehabilitation pays off almost immediately due to the significant savings achieved. The great difficulty in this case is to promote the rehabilitation of non-insulated buildings that are not planned to be carried out in the short term.
As indicated in the study, the use of low-emission glass is not justified for the climate of San Sebastián, especially on facades with greater sunlight since solar gains are reduced, (logically this entails a reasonable increase in heating demands of the building that, given the climatic zone in which it is located, is going to harm it considerably).
Regarding the improvement or reform of the heating installations, a joint study with the rehabilitation of the envelope deserves to be carried out. The study recommends replacing the equipment with condensing boilers and incorporating regulation and control systems to improve operation, so that they can be adapted to the reduction of the demands generated by the rehabilitation of the envelope, generating greater economic savings.
