District Heating and Fabric Upgrade – Listed 1970s Residential Estate

Project Summary

This project involved the development of a long-term heating and hot water solution for a large Grade II listed residential housing estate constructed in the 1970s and served by an on-site energy centre. The estate comprised several major tiered residential blocks together with a range of associated community and commercial buildings.

The existing heating system utilised embedded heated wall pipe coils, many of which were failing and no longer reliable. The brief required the replacement of the legacy heating systems while retaining the architectural integrity of the listed buildings, maintaining resident comfort and future-proofing the estate for low-carbon heat generation.

Scope of Services

Our role included full feasibility, concept and detailed design for the replacement of the heating and hot water infrastructure across the estate. This included:

Options appraisal for replacement heating systems and heat emitters

Design of new district heating distribution pipework and in-dwelling heating interface units (HIUs) to provide individually metered heating and hot water

Replacement and redesign of domestic cold and hot water services

Thermal modelling and assessment of building fabric performance

Development of ventilation and heat recovery strategies to mitigate infiltration losses

Close coordination with appointed heritage architects and conservation specialists to ensure compliance with listed building requirements

Liaison with resident representatives and stakeholder advisors throughout the design process

Key Technical Challenges

The project presented a number of complex technical and stakeholder challenges:

All dwellings were occupied throughout the feasibility and pilot study phases

The original heated wall systems were integral to the building fabric and highly valued by residents

Listed building status significantly restricted service routes, penetrations and visual impact

Multiple building types were connected to the same on-site energy centre, requiring careful hydraulic and controls coordination

The design needed to remain compatible with future conversion to centralised heat pump systems

Design Approach and Solutions

A fabric-first and system-wide approach was adopted. Alongside the new district heating design, detailed studies were undertaken to improve thermal performance through glazing upgrades, insulation to exposed floors and flank walls, and the introduction of mechanical ventilation with heat recovery where appropriate.

New district heating mains and HIUs were designed to provide fully metered services and low visual impact within dwellings. Flow temperatures, system ΔT and plant selections were carefully developed to ensure the network could be converted to low-temperature heat pump operation in the future without major infrastructure replacement.

Pilot installations were implemented in selected dwellings to assess alternative heat emitters and fabric upgrade options prior to finalising the estate-wide solution.