BRE Scotland led the development of the Refurbished House on the Innovation Park as part of the European ERACO STAR project. This three country project (Belgian Building Research Institute, Passief Huis Platform, Belgium and Lund University, Faculty of Engineering, Sweden are European project partners) focuses on the technical refurbishment of typical dwellings in a Sustainable Thermal Acoustic Retrofit (STAR). The ERACO STAR project aimed to focus on ‘real’ sustainable renovation of dwellings considering the acoustic aspects alongside thermal properties.

In Scotland we replace the housing stock at a rate of less than 1% per year. It is therefore imperative that we improve the performance of the existing housing stock, if we are to achieve the CO2 reduction targets mooted for 2020 and 2050. The Refurbished House will provide a research base for how this can be done most effectively in the future and will provide valuable information on cost and performance of retrofit solutions.

Using historical design information and traditional materials, a full-scale ‘four-in-a-block’ dwelling similar to over 250,000 existing Scottish homes, has been constructed and refurbished. Each of the four apartments (G1, G2, F1, F2) has been refurbished using different approaches, materials and technologies to showcase four options for upgrading (see information on accompanying app).

The actual performance of these retrofit solutions, and the associated cost of the interventions, is currently being monitored and measured to determine effectiveness. A ‘baseline’ model has been created to help identify improvements in each of the four upgrades. This will provide valuable information for the development of a retrofit strategy to tackle the building stock of this type Scotland.

These properties generally referred to as ‘4-in-a-block’ (where there are two flats on the ground floor, and two on the first floor) have been constructed using different building systems across Scotland and are considered to be some of the worst performing apartment building types both thermally and acoustically. Although there are approximately 250,000 of these in Scotland, their build style (1930’s to 1970’s) is similar to cavity block walls found in 3 million dwellings in England.

The project is designed to assess the cost effectiveness of fabric upgrades for this important building style, for walls, windows, roofs and services. Indoor air quality tests, air tightness tests, and acoustic testing has been undertaken as well as detailed thermal analysis from inbuilt thermal sensors, thermography and thermal modelling.

Saltire Society Housing Design Awards

The Refurbished House has received a Commendation in the ‘Housing in Innovation’ category of the Saltire Society Housing Design Awards 2015. The Housing Design Awards reward and advocate innovation and excellence in Scottish house building and place-making.

Refurbished House: BRE Innovation Park @Ravenscraig

A showcase of the Refurbished House at the BRE Innovation Park @Ravenscraig, plus a wider look at the retrofit challenges facing Scotland and the presentation of the new app ‘BRERetrofitLab’.


BRE worked with Kraft Architecture and Hannah-Reed Consulting Engineers to create detailed drawings of the ‘4-in-a-block’ test building. The design is based on historical references with input from Historic Scotland and North Lanarkshire Council. These drawings provided the basis of planning and building warrant applications. BRE appointed Cruden Building and Renewals as the main contractor to oversee the construction of the test building. The ERACO project team, along with the architects, Kraft, and the developers have designed a retrofit strategy for each of the four apartments (G1, G2, F1, F2), which can now be viewed in the Refurbished House on plot 9.

Flat G1 Flat F1 Flat G2 Flat F2
Imposed Restrictions Occupied

Minimal Disruption


Minimal Disruption


No Gas



No Gas

Refurb Approach External Fabric

Basic Heating Upgrade

External Fabric

Full Heating Upgrade

Internal Fabric Internal Fabric
SAP Target 76 82 85 83
Section 7 Target Bronze, 2010 Pass Silver, 2010 Pass
Heating gas combi boiler

gas flue save technology

gas boiler

4m2 solar thermal panels

electric combi heat store

underfloor heating

air source heat pump (ASHP)

cylinder with radiators

Walls cavity fill

external wall insulation

cavity fill

external wall insulation

cavity fill

moisture buffering internal wall insulation

acoustic treatment lining

cavity fill

internal wall insulation (Phenolic and Aerogel)

Loft / Ceiling additional insulation acoustic ceiling treatment additional insulation
Floors insulation to ground floor acoustic treatment to main rooms
Ventilation standard intermittent room fans positive input ventilation (PIV) intermittent individual room heat recovery (kitchen and bathroom) full house MVHR system
Windows (U-value [W/m2K]) 1.2 1.2 1.5 (traditional style) 0.9
Airtightness Target 6.53q50 7.53q50 6.11q50 6.04q50
Additional Features independent living adaptations

interior designed by IKEA

3kW solar PV array


The actual performance of these retrofit solutions, and the associated cost of the interventions, is being monitored and measured to determine effectiveness. A ‘baseline’ model has been created to help identify improvements in each of the four upgrades.

This will provide valuable information for organisations developing a retrofit strategy for similar properties in Scotland.

Although only four retrofit options have been built, a number of others have been designed throughout the project. These additional options are presented in an iPad app, released on 16thJune. The app will allow users to replace or change products within the apartments and see the resulting improvement (or otherwise) in energy performance and the resulting change in costs. This app provides information on additional upgrade options to provide a wider choice of potential upgrading strategies.

In addition to the BRE/ESRU testing that will be undertaken on all the other properties at the Innovation Park @Ravenscraig, Edinburgh Napier University are to conduct air tightness and acoustic tests as part of their involvement in the ERACO STAR project.