Passivhaus Affiliate

Wrapping up warm in Great Yarmouth

With the built environment responsible for 30% of our carbon emissions in the UK, the need for energy efficient retrofit at scale across the country becomes ever more urgent. Affordable and practical solutions that can help us warm our homes without warming the planet, and at the same time combat fuel poverty, bring health benefits to residents, and ensure the long-term durability and resilience of our housing stock, are vital to our low-carbon future. One possible scaleable deep retrofit solution was demonstrated to an interested audience in Great Yarmouth last week, as PHT member Beattie Passive showed off progress on a 1960s block of flats in King Street, being wrapped up warm in their innovative T-Cosy system. 


King Street Great Yarmouth retrofit site visit September 2019


The project is being undertaken for Great Yarmouth Borough Council, with funding support from BEIS and in partnership with a consortium including PHT member Enhabit, Design Buro and Oxford Brookes University. The grant aims to support innovation in energy efficiency, so essential to meet our decarbonisation targets. After earlier trials in Birmingham and Solihull, the hope is that the T-Cosy system should be further refined to the point where it is capable of being swiftly rolled out on a larger scale across the country. It has the potential to be a fast, efficient and cost-effective solution to the challenge of deep retrofit on a common building typology.


Bridges to cross

King Street balconies and chimneys

With this Great Yarmouth project, Beattie Passive deliberately set out to find challenges for the system. Concrete balconies, adjoining buildings, old chimneys and concrete gutters all mean this old 60s block offered plenty of complexities to resolve. Chimneys have been removed and balconies cut off, to later be replaced with new balconies outside the insulating envelope, fastened with thermally broken fixings.

The resolution of thermal bridges is key to the success of this system. As well as addressing the balconies, the team have also paid attention to heat loss through the ground floor perimeter - a trench is dug around the base of all external walls to a depth of 600mm in order to allow the insulation to be extended below ground level, achieving a floor perimeter u-value of 0.46 w/m²k.

King Street bracket installationCold bridges were also identified at the point where the new skin is fastened to the old building: thermal modelling of the fixings showed a shocking loss of heat. To resolve this, the standard metal brackets have been replaced with specially developed GRP brackets - made from extruded lengths of glass-reinforced plastic that are then cut to size. Once production of these brackets scales up, it will be a simple and cost effective solution for a frequently repeated detail, applicable to all sizes and shapes of buildings.

Beattie Passive have been subjecting their T-Cosy system to rigorous testing processes, to ensure that not only is it capable of hitting EnerPHit targets, but it also has robust defences in case of fire. A simple sprinkler system at the top of the new insulating skin allows it to be flooded with water. In a test, 900 litres of water were emptied into a sample wall build up, fully saturating it in just six minutes. Moisture readings were taken before and after, and once the water had drained out, the insulation recovered to its original properties within 24 hours. In another test, a fire log was inserted into the sample wall and set alight. The fire suppression system did its job, quickly extinguishing the conflagration, and all insulation not in direct contact with the flames was unaffected.


Before and after

King Street Great Yarmouth before and after


Oxford Brookes’ before-and-after monitoring programme for the project encompasses all six flats. It will gather both hard data on relative humidity, temperature and CO2, as well as spot checks on levels of VOCs, and subjective feedback from the residents through surveys and interviews. Already it’s clear that while the flats are of a kind, their residents are not, with a wide variation of habits and preferences, from low occupancy to high occupancy, from preferring warm temperatures to keeping windows open all year round for a fresh and bracing indoor environment. Perhaps fresh air supplied via the MVHR may persuade this particular resident to adjust their habits a little!


Energy performance

Walls and roof u-value:

0.11 w/m²k

Floor perimeter u-value:

0.46 w/m²k

Whole window u-value target: 

0.78 w/m²k

Airtightness target: 


Thermal energy demand target:

<25 kWh/m².yr

Beattie Passive are aiming for EnerPHit certification for the project, and for the system, in the longer term, they’re aiming to be able to achieve this at a low cost of just £45-£50k per home. The system offers the advantage that all work can be carried out with residents remaining in situ, so the disruption and cost of relocation is avoided.


Hear more

To learn more, join us in Manchester on 29 October for Climate Emergency: Mainstreaming Passivhaus by 2030, where Ron Beattie of Beattie Passive and Konstantinos Megagiannis of Enhabit will present the scheme as one of our featured case studies. Discounts are available for those working in Local Authority and Housing Associations. 

UKPHC19 | Climate Emergency: Mainstreaming Passivhaus by 2030 | Tuesday 29 October, Manchester



Further information

Great Yarmouth Retrofit - Beattie Passive Blog

Passivhaus Retrofit

Climate Emergency: Mainstreaming Passivhaus by 2030


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22nd September 2019

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