{"id":754776,"date":"2024-09-24T00:25:35","date_gmt":"2024-09-23T23:25:35","guid":{"rendered":"https:\/\/www.architectsjournal.co.uk\/?p=754776"},"modified":"2024-09-24T09:50:02","modified_gmt":"2024-09-24T08:50:02","slug":"retrofirst-stories-how-ecd-is-deep-retrofitting-occupied-1930s-council-homes","status":"publish","type":"post","link":"https:\/\/www.architectsjournal.co.uk\/news\/retrofirst-stories-how-ecd-is-deep-retrofitting-occupied-1930s-council-homes","title":{"rendered":"Retrofirst stories: how ECD is deep-retrofitting occupied 1930s council homes"},"content":{"rendered":"

With up to 40 per cent of carbon emissions coming from the construction industry, the profession needs to find ways of adapting the type of buildings it designs, and fast. The default option for any project should be to adapt and re-use an existing building, one of the key demands of the AJ\u2019s\u00a0RetroFirst campaign<\/a>.<\/p>\n

Our ongoing series seeks to celebrate the projects that save buildings from ruin or give them a brand new life.<\/p>\n

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Tell us about the project.
\n<\/strong>This is a pilot project for the deep retrofit of 46 semi-detached and terraced houses and one block of four one-bedroom flats, all traditionally built with solid brick walls, dating from the 1930s. The construction budget is \u00a36.48 million and the main contractor is Axis Europe<\/a>.<\/p>\n

The homes are part of Cambridge City Council\u2019s housing stock in Romsey Town near central Cambridge, and all households have volunteered to be part of this pilot project.<\/p>\n

The council put in place an extensive programme of resident engagement to encourage households to sign up and support them along the journey.<\/p>\n

What were the challenges of the existing buildings?
\n<\/strong>Continuity of insulation and airtightness is challenging in any retrofit, and all the more so when the residents will remain in their homes. If you\u2019re doing a new build or gutting and retrofitting an empty house, you have more choice in how to manage airtightness and thermal bridges. Working around an occupied home leads to solutions that can primarily be done from outside. For example, maintaining continuity at tricky junctions such as the \u2018skeiling\u2019 detail meant we ruled out insulating at loft level in favour of insulating at rafter level, to get continuity around the whole external envelope.<\/p>\n

The decision to remove roof tiles, fit membranes and insulation then reinstate the salvaged roof tiles not only solved the essential continuity question but also gave us the larger overhangs needed at eaves and verge for the 200mm external wall insulation (EWI), plus a warm loft for the MVHR ductwork installation \u2013 and it simplified the PV installation. At the time, it felt like a big leap to go from simple loft insulation to re-doing the whole roof, but the multiple benefits justified this decision.<\/p>\n

Had demolition ever been considered for the properties? What is being done to allow residents to remain in the homes while work is under way?
\n<\/strong>As part of the current social housing stock of council, demolition was not considered as it would have meant a long-term decant or rehousing of all residents. Different levels of retrofit were therefore assessed by Cambridge and the consultant team, both in terms of the level of energy performance and in terms of disruption to households. The chosen strategy is a deep-retrofit designed around residents remaining in their homes, other than for the small one-bedroom flats, where a temporary decant was the only realistic option.\u00a0 The energy performance target for the majority of these houses is to Net Zero operational energy as well as near-EnerPHit, with some variation between houses, due to form factor and orientation.<\/p>\n

A pragmatic approach has been taken to minimise disruption to residents while still meeting the ambitious energy performance target. For example, the solid kitchen floors will be insulated externally rather than internally, to avoid taking out kitchens. Both Cambridge and the main contractor, Axis, are working with residents as the work progresses to keep everyone informed and to find the best solutions for managing the sequence and timing of works to suit individual households.<\/p>\n

The installation of subfloor insulation to living and dining rooms will potentially be the most disruptive and ambitious measure, but one that will have a huge impact on heat loss and comfort. We\u2019ve had to communicate these benefits to keep residents on board.<\/p>\n

What have been the main design drivers to get carbon levels down to net zero?
\n<\/strong>While the houses appear pretty similar at first glance, the curving street gives us a variety of orientations and roofscapes, some better for roof photovoltaics than others. As such, the on-site electricity generation varies considerably per house, meaning the rest of the retrofit design has to be very thorough and efficient for all dwellings to reach \u2013 or get as close as possible to \u2013 the net zero operational energy target.<\/p>\n

This has been done by a full external envelope upgrade, combined with MEP replacement developed by Greengauge Building Energy Consultants<\/a>, including air source heat pump, Sunamp thermal store (to make maximum use of the generated electricity), and MVHR for good internal air quality and comfort.<\/p>\n

If we could\u2019ve done one more thing, it\u2019d be adding PV batteries<\/p><\/blockquote>\n

Working together, these measures \u2013 namely building fabric, MEP and renewables \u2013 will drive the homes down to net zero. As noted, the project is focused on putting people first above the building and just its carbon reduction.<\/p>\n

However, if we could do one more thing, it would be adding PV batteries in now to allow the household to make maximum use of electricity generated by the photovoltaics on the roof. These were originally planned but had to be taken out of the project scope for budget reasons, though with the infrastructure in place for these to be added later. That said, the electricity generated by the PVs is used by the heat pumps to charge the SunAmp thermal store, still making good use of the generated electricity.<\/p>\n

\"\"

Front elevation, external wall insulation work in progress \u2013 Cambridge Net Zero Retrofit Pilot Project<\/p>\n\t

Source:Cambridge City Council <\/p><\/div>\n

As a prototype model, have you had to tackle the scheme any differently?
\n<\/strong>Gaining a thorough understanding of the existing performance of the poorly insulated solid-wall homes was a key first step. Investigations carried out by SOAP Retrofit<\/a> included resident surveys, energy bill analysis, airtightness testing and heat transfer co-efficient monitoring. Temperature and humidity profiling was also undertaken to assess the critical issue of condensation and mould risk, which is a real concern for residents.<\/p>\n

The design process included a comparison of several iterations of the design, including full EnerPHit, near-EnerPHit and AECB standards, to fully understand what would be needed to meet Net Zero Operational Energy and to balance levels of disruption with levels of performance.<\/p>\n

The two elements that were scrutinised more than any others were: the floor insulation (there are both suspended and solid floors in these houses); and whether to insulate at loft or rafter level. We used Passive House Planning Package to test out multiple scenarios and combinations and the effect these had on the energy performance of various archetypes.<\/p>\n

Minimising embodied carbon is also critical to achieve wider net zero carbon targets, so existing materials and components are being reused wherever possible, including roof tiles and floor coverings. New materials have also been selected with long-life expectancies and low embodied carbon, including mineral wool, hemp and jute insulation. Evaluation of the project delivery and post-completion monitoring will inform the development of future upgrade works to further homes across Cambridge, supporting the council\u2019s goal to be net zero carbon by 2030.<\/p>\n

What have been the main lessons from the project that you could apply on other developments?
\n<\/strong>It has been a huge and very satisfying lesson to see how a really thorough resident engagement programme has worked to help prepare households for the extensive work to their homes. This level of retrofit does rely on the household understanding the process and knowing what to expect when the work starts, as well as seeing the end-goal of comfortable, warm homes and lower bills.<\/p>\n

This level of retrofit relies on the household knowing what to expect<\/p><\/blockquote>\n

In technical terms, the high energy performance target of this project and the many design iterations to meet it has provided us with a set of data for combinations of fabric and MEP improvements and, as a result, a better knowledge of where small tweaks can have the most useful gains.<\/p>\n

\"\"

Cutaway image of proposed retrofit measures – Cambridge Net Zero Retrofit Pilot Project<\/p>\n\t

Source:ECD Architects<\/p><\/div>\n

For example, the research, design details, U-value and Psi-value calculations for perimeter insulation around both the solid and suspended floors have culminated in a set of information that can be used as a starting point for other house types.<\/p>\n

Checking whether we need to dig up the concrete path around the side of a house to install deep perimeter insulation, or can have shallower insulation and leave the path in place, means the project budget can be allocated where it\u2019s most needed.<\/p>\n

What needs to happen to allow such a programme to be rolled out nationally?
\n<\/strong>Public perception and confidence in retrofit is key. There\u2019s no doubt that most households in a cold home with high bills would love to see their home significantly improved, but there\u2019s trepidation about having contractors carrying out such extensive work both inside and outside the home, especially when it involves unfamiliar materials or equipment.<\/p>\n

A deep retrofit changes the way a house functions<\/p><\/blockquote>\n

A deep retrofit such as this one does change the way a house functions and, if you\u2019ve run your home the same way for 20 years, it\u2019s inevitable there will be concern about everything changing at once. But hearing the same positive messages on retrofit from government, media, local councils, friends and neighbours will help with confidence and trust \u2013 and there are many organisations working towards that goal. That\u2019s the exciting prospect for me.<\/p>\n

\"\"

Form factor and heat demand diagram \u2013 Cambridge Net Zero Retrofit Pilot Project<\/p>\n\t

Source:ECD Architects<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

With up to 40 per cent of carbon emissions coming from the construction industry, the profession needs to find ways of adapting the type of buildings it designs, and fast. The default option for any project should be to adapt and re-use an existing building, one of the key demands of the AJ\u2019s\u00a0RetroFirst campaign. Our …<\/p>\n","protected":false},"author":915,"featured_media":755767,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_oasis_is_in_workflow":0,"_oasis_original":0,"ep_exclude_from_search":false},"categories":[681],"tags":[101050,1155,5950,6196],"yoast_head":"\nRetrofirst stories: how ECD is deep-retrofitting occupied 1930s council homes<\/title>\n<meta name=\"description\" content=\"Marion Gray, senior architect at ECD Architects, talks to the AJ about revamping 1930s housing stock \u2013 while still occupied \u2013 as part of its Cambridge Net Zero Retrofit Pilot Project\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.architectsjournal.co.uk\/news\/retrofirst-stories-how-ecd-is-deep-retrofitting-occupied-1930s-council-homes\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" 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