Can we upgrade historical buildings? The 5 most challeging retrofit projects in the UK

5. Stirley Community Farm,  Yorkshire

The conversion of this old and damaged barn into an Education centre for the Yorkshire Trusts Shirley Community Farm is a very innovative example of a sustainable retrofit.

The strategy adopted to revive this derelict stone barn involved the design of a super insulated and airtight box within the external shell of the original barn. The inner box features a fibreglass insulated timber frame construction which has the double function of enhancing the thermal performance of the envelope and providing the existing old masonry walls with additional structural stability.

This pioneer approach to retrofit of historical buildings has the potential to lead the way in scenarios where it’s not possible to intervene directly onto the existing shell. The Cre8 Barn has won the UK Passivhaus Awards2015 and has achieved the ambitious Enerphit standard due to its exemplar energy and thermal performance.

4. Erneley Close, Manchester

Erneley close before retrofit, image via Zehnder website

Existing maisonette block, Manchester

The regeneration of Erneley Close concrete frame maisonette blocks into new low energy accommodation proved to be very challenging. The project involved the refurbishment of the decrepit 32 maisonette along with a plan for the re-branding of the entire urban area.

Major issues included thermal bridging at the multiple balconies and walkway, along with structural defaults of the existing concrete frame, which result in a continuous remodelling of the building into the PHPP software for Passivhaus assessment.

The design strategies involved the removal of the outer layer of the cavity walls replaced with a timber-framed layer, removal of existing pitched roofs and garages.  The benefit of having an Airtightness champion on site was essential to the success of the retrofit, which ensured the demanding Enerphit requirements were met.

The vision behind the regeneration of Erneley Close development along with the intent to give a new architectural language to the building was key to this demanding retrofit.

3. Clapham Retrofit, early Victorian townhouse, London

This 170 year old Grade II listed house in South West London had heavy issues with rotten joists, air leakage, damp brick walls and a fire cement roof leaking water.

Additionally, being a four-storey early-Victorian building sitting in a conservation area posed major challenges for an in depth refurbishment of both the timber structure and overall the fabric and its appearance. As result, an initial thorough assessment has taken place through a thermographic survey, u-value monitoring, interstitial moisture gradients and temperatures tests in the external masonry walls.

To tackle the thermal faults of Clapham house it was decided to add a significant amount of insulation to the external walls keeping the envelope ‘moisture robust’ at the same time and allowing it to dry out both inwards and outwards. Twelve different types of insulation were used for the facades depending on the issues that the insulation had to address, therefore thickness and types vary according to orientation and build-up. An air permeability of 0.3 ACH has been achieved through lime plastering masonry walls internally and taping with Intel Plus membranes all the ceiling, joists ends and windows-to-wall junctions.

In 2014 the retrofit of Clapham house has been successfully completed and now the occupants are very satisfied with the thermal comfort of their totally improved home. The building is also the first one to achieve the Association of Environment Conscious Building’s (AECB) Silver Standard for its optimal energy performance.

2. Bloomsbury House, Georgian house, London

Bloomsbury house is  a 1820’s beautiful Georgian terrace house in London that has been used as offices for many years and in need of a in-depth thermal and functional upgrade.

Due to its historical value, both the exteriors and interiors were protected by the local authority conservation officers. The owner was willing to convert the building back to a family house. Additionally, the purpose was to target the Enerphit standard (the passivhaus standard for retrofitted buildings) in order to offset draft issues and poor thermal performance.

Thanks to the optimal form factor of such tall terrace houses, which are compact in shape and with a minimum external wall area, the fabric didn’t need that much of insulation to achieve Enerphit target U-values. However, the ground floor, first and second floors featured historic interiors with ornate cornicing, original woodwork  and marble fireplace which has to be preserved. As result, the strategy adopted involved the use a variety of insulation materials, mainly aerogel and Icynene, which would have suited the different requirements of the fabric. Particularly, the team used vapour open Icynene formula, which is a water blown soft foam that minimise air leakage and increase thermal and acoustic performance while preserving the architectural details.

The chimneys were filled with vermiculite and sealed to reduce air permeability, which ended up being 1.1 ACH, so slightly above the Enerphit target but still a remarkable results for such old building.

This amazing retrofit resulted in an overall space heating demand of 20 kWh/m2a, which means 95 % below the original figure. The energy upgrade of Bloomsbury house has been radical and has set an outstanding precedent for any listed buildings so far, showing that retrofit can be done in historic buildings successfully.



1.  New Court, Trinity college, Cambridge

New Court at Cambridge Trinity College is a 200 year old neo-gothic building old and famous for having hosted some of the most important poets of any time. It has been used as a student accommodation since the 1800′, however in recent times it had draught issues and couldn’t guarantee thermal comfort to its occupants.

The design strategies implemented to improve the efficiency of the building and the comfort of the occupants range from:

  • adding internal wood fibre boards to the external walls; 4mm-thick lime plaster skim, then attaching a 72mm-thick sheet of wood fibre insulation board and a gypsum board on the inner side.
  • Installing MVHR units and hiding them in the roof void of each block; this supplies supply fresh air , which is ducted through the existing chimneys flues and then spread from the fireplace in each room;
  • replacing single glazed windows with double glazed ones with similar appearance ;

The retrofit of New Court represents one of the most significant succefull retrofit of heritage buildings ever, due to the challenges posed by the its architectural features and age. The building is now performing as expected, so the retrofit intervantions undertaken shows that a healthy balance of energy efficiency and preservation of heritage buildings can be achieved.


Links for further reading:

Passive House+ magazine, Issue 20


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