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Zaramaga - social housing renovation challenge in sustainability

A Subliniat Caz February 2017
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The project consists of an energy refurbishment in a social housing block containing 30 dwellings built between the 1950’s and 60’s and located in the neighborhood of Zaramaga in Vitoria-Gasteiz, Spain.

The owner´s housing association, under the technical advice of the department of Urban planning in Vitoria-Gasteiz and collaboration of VISESA (public company for social housing in the Basque Country region) decided to carry out a complete renovation project of energy efficiency improvement related to three main sustainability challenges: building envelope, accessibility and energy systems facilities.


Sustainablity challenges

Building envelope

The transmittance values for the façade, roof and ground slab were greatly reduced with the installation of a thick layer of insulation around the whole envelope. The insulation was placed with special attention to the small constructive elements; forming a continuous thermal insulation skin and, therefore, minimizing thermal bridges. The façade solution consisted of a combination of Neopor EPS external insulation system (120 mm) and a ceramic ventilated facade using mineral wool as insulation (120 mm). The original interior carpentry throughout all the dwellings was conserved, and a second exterior carpentry was placed in line with the new outer thermal insulation. Air tightness was reinforced to avoid the maximum uncontrolled infiltration as the dwellings have been equipped with dual flow ventilation with heat recovery (HRV).



The key issue was to install a lift according to the space limitations of the building. The only possible solution was to demolish the existing stairway and replace them with a smaller, single-file stairway and build a new lift in a new exterior location. This external lift was possible with the cession of public land by the municipality. This land was also used to provide new access from the back street of the building, thus avoiding the entrance steps that exist in the access from the main road. Three lifts were added.


Energy systems facilities

During the initial meetings for the design phase, it was decided to centralize the thermal generation and remove the inefficient individual systems (old gas boilers, LPG and electric heaters). However, the lack of common space and the limited number of dwellings (30), made the installation of central heating economically unviable. In the end, it was decided to maintain an individual heat generation system, but replace them with new highly efficient condensing gas boilers. New systems were also added; photovoltaic panels (3.6 kWp installation on the roof) to reduce electricity consumption in common areas and a ventilation system with heat recovery (HRV) which will help to maintain high indoor air quality while further reducing energy demand.



Cuadrilla de Laguardia, 2-4-6, Zaramaga, Vitoria-Gasteiz, Basque Country, Spain


Project team

Client: Property owner´s housing association of the building (Cuadrilla de La Guardia 2-4-6)

Project management and architect design: Luzyespacio Energía Arquitectura / IMV Arquitectos

Contractor: UTE Sarkys-Lagunketa y Reyco

Support and collaboration: Vitoria-Gasteiz City Urbanism area / VISESA (public company for social housing in the Basque Country Region)


Time schedule

Built: 1960

Renovation design process: 2011 - 2014

Renovation works: November 2014 - September 2015

Monitoring: May 2015 until present time


Building use and area

4-storey social housing building with 30 dwellings

Total: 2,132 m2

Usable Floor Area: 1,833 m2


Construction costs

Global renovation cost (VAT and taxes excluded): 1,258,060 €

Renewable energy systems cost: 13,684 €

Cost of studies: 116,386 €

73.7% of the global renovation cost was funded (

- 559,308 € from subsidies of the Basque Government (REVIVE),

- 206,695 € from subsidies of the Municipality of Vitoria-Gasteiz (barrios oro),

- 116.785 € from VISESA (PIME’S EU project),

- 63,962 € from financing support.


Envelope performance

Existing envelope (U-value average: 1.11 W/m2.K)

The building did not have a basement and its original first floor slab was built over an uninsulated air chamber with ventilation problems. The façade envelope was constructed by a double external closing with a 25 cm brick wall, air cavity and a 9 cm brick wall. The roof over the storage space for individual dwellings, located on the last floor, was built using an inclined reinforced concrete slab and concrete tiles. The beams crossed the air chamber on every floor and finished on the outer brick wall, therefore multiplying the thermal bridges of the building.


Renovated envelope (U-value average: 0.25 W/m2.K)

The aim of the improvements was the installation of a continuous thermal insulation skin around the building. This insulation covers all the envelope, including the façade and the ground slab. The balconies were partially closed and the decision was up to the owners to choose either; to keep the outer space or to incorporate it into the heated area.

The most important change has been the material for covering the enclosure of the stairways. These enclosures were designed to use a composite sheet metal and insulation panel. However, as this material does not guarantee the sealing of joints in the corners, the decision was made to replace it with insulation and corrugated metal sheets.



Details of renovated envelope elements

-External wall façade (U-value: 0.22 W/m2.K). There are two types of added protection and finishing for improving insulation on the existing outdoor façade:

1 - Neopor EPS plates (120 mm thick), or

2 - extruded ceramic ventilated façade with mineral wool (120 mm thick).

In the new outdoor façade corresponding to the elevators, 60 mm sandwich panel modules have been installed. The gallery-balconies are covered by the same sandwich panel thickness and corrugated outer sheets with a lacquered finishing.

-Roof (U-value: 0.19 W/m2.K). The new pitched roof is made from the existing concrete slab, a mortar layer of 1.5 m, 80mm thick mineral wool, galvanized steel fasteners, 60 mm metal sandwich panel lacquered gray .

-Ground floor (U-value: 0.22 W/m2.K). The air chambers for plumbing with an average thickness of 30 cm were filled and insulated with Neopor EPS.

-Windows (U-value: 1.45 W/m2.K). The exsiting carpentry was replaced by double-glazed and low emission windows with thermal barriers and aluminum frames.

-Doors (n.d.)


Energy consumption

The expected energy consumption after renovation* according to Calener VYP software (official tool for energy certification in Spain) is:

-Total primary energy consumption: 25.2 kWh PE/m2.year (before renovation it was 328.4 kWh/m2.year)

-Energy saving in heating and DHW: around 70%

-Energy rating improves from an old ‘E’ (71.7 kg CO2/m2.year)  to an ‘A’ (6 kg CO2/m2.year)


Renewable energy production:  1 % (used solely for electricity consumption in common areas)

(*) The real consumption was monitored from October 2015 until October 2018, in order to have a 3 year period of monitored consumption values to allow for a better analysis of results.


Energy systems

Heating system and Hot water system with condensing gas boiler

As it was impossible to acheive enough space for a centralized system generating hot water and heating for all dwellings, it was decided to replace all existing boilers with high efficient gas condensing boilers. The new condensing boilers provide heating and hot water for each home, and have modulating control.


Ventilation system with heat recovery, allowing natural ventilation in summer

Before renovation, the lack of ventilation, condensation and worsening of health conditions were common pathologies detected in the building. The solution for adding ventilation was to design a heat recovery ventilation system to be installed horizontally in the ceilings. The system is also equipped with a bypass for free cooling in summer to allow automatic cooling, usually during the summer nights.


Solar photovoltaic system

Each entranceway has a photovoltaic solar installation, which is designed to supply some of the communal use (stairs, lighting, HRV system). Each pv installation consists of 5 modules of 245 Wp photovoltaic, with a panel dimension of 982 mm wide and 1,638 mm high.


Building management system

In order to assess the different activities and variations in the building, the control of all the elements is monitored. In the case of ventilation, the obtained values ​​are temperature and relative humidity. In terms of consumption, the monitoring system also controls the consumption of the ventilation system, elevator and PV production. The consumption and insulation measurements are also measured by adding a kilocalories counter in all the boilers of every home. All these values ​​are recorded by probes placed in the building and whose readings are sent daily to the Building Control Laboratory of the Basque Government.


Awards and recognition

Winner of Green Building Solutions Awards 2016 in the Sustainable Renovation Grand Prize category (

Finalist in the European Responsible Housing Awards 2016 (


Additional information

GBCSAwards 2016 video in Spanish (subtitled in English):

Project description:

Case study of the project PIME’S from the CONCERTO initiative. Project  Deliverable 3.1.3 and 3.15 about the building construction ( and project deliverable 2.6.6. about the socio-economic analysis (

Renovation study:

-Before renovation:

-After renovation:

Award labels

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