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When planning retrofit works, stick to the ‘four Cs’
Planning for retrofit projects can be incredibly complex and there’s no one size fits all approach. To navigate costs and timeframes, housing associations need to stick to the ‘four Cs’, writes Colin King, technical lead for retrofit and construction at Sero
Colin King is technical lead for retrofit and construction at Sero
With much of today’s public discourse centred around the forthcoming general election and speculation about a change of government, the huge challenge of retrofitting the country’s housing stock is regularly being overlooked. All the while, housing associations are getting on with the work but it is important they are mindful of potential pitfalls.
It is well known that housing will be a key pillar of the government’s attempts to reach net zero by 2050, given that it currently accounts for roughly 18% of the UK’s carbon emissions. With this in mind, significant effort is being undertaken to explore how to speed up the decarbonisation of the UK’s housing stock, which is renowned as the least energy efficient in Europe.
A lot of energy is being put into grouping properties through a ‘typology’ lens, ie comparing properties with similar characteristics such as whether a property is semi-detached, end terrace cavity wall, or part of a tower block.
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On the face of it, this appears to be a logical grouping and can help forecast likely measures and potential costs. However, when it comes down to physical carrying out of the works, the use of a ‘typology’ approach can misunderstand the pathway that a dwelling has been on since its original construction.
For instance, all participants in the retrofit of buildings, including retrofit co-ordinators, assessors, designers and installers need to account for factors such as added extensions, existing insulation present, replacement windows, upgrades to heating appliances, resident income and occupancy, to name just a few.
All of these factors and more will have a bearing on things like airflow, condensation and temperature. These will, in turn, impact the property’s retrofit requirements, meaning that assessments using a ‘typology’ lens can fail to capture a property’s uniqueness.
What can easily happen is that in the rush to get going on retrofit work, there is a failure of moisture risk management which can have detrimental impacts on the occupant’s health.
A systemic approach that follows the principles of the ‘four Cs’ in moisture risk is essential to head off increases in damp and mould, risk to structure by over optimising thermal performance, and the introduction of technologies that occupants may struggle to operate.
The ‘Four Cs’ are…
Context: understand the context of the building – its condition, location, construction form and occupancy levels, as well as geographical features such as solar gain, wind direction and risk of flooding. All these factors are essential to ensure the building project is understood in terms or opportunities and barriers. The information gathered at this stage is essential for the retrofit designer to ensure the design is compatible with this context.
Coherance: ensure coherence in approach and detailing. Address the connections and penetrations in the building from services and openings, ensure that thermal bridging is addressed and reduced, and that the materials are compatible with the materials the building is constructed of, focusing on any need for a total vapour open approach or a vapour closed approach to moisture management in the fabric of the building.
Capacity: build in capacity in the design and construction phase for mistakes, uncertainties and future challenges.
Caution: ensure that caution is taken in the use, maintenance and aftercare phase where there are ongoing requirements of care and uncertainty of outcomes, and in any circumstances where there is any uncertainty, apply caution and do not over optimise the building to a point where failure is inevitable.
Housing associations are under immense pressure to start in earnest on retrofit work and there is a strong sense of duty and enthusiasm to meet targets. However, it is important to take a long-term view of the work and use a considered approach that accounts for each property’s unique qualities.
The benefits of doing so are two-fold. Firstly, the sector can decarbonise smoothly and on time, helping to meet the country’s wider net zero targets. Secondly, landlords can avoid future issues of damp and mould which would only serve to undermine resident-landlord relationships.
Decarbonisation is a costly process, with the National Housing Federation previously suggesting the bill could be at least £36bn. Not only this, but landlords are working to a tight time scale with a target to make all social homes reach Energy Performance Certificate Band C by 2035. These factors combined underline the importance of getting it right first time.
Colin King, technical lead for retrofit and construction, Sero
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