Managed Retrofit

Detailed insight into Retrofit

A Detailed Insight into Retrofit

Introduction

Retrofitting is the process of upgrading existing buildings to improve energy efficiency, sustainability, and overall performance. With domestic properties contributing significantly to the UK’s carbon emissions, retrofitting is essential for meeting Net Zero targets, tackling fuel poverty, and enhancing the living conditions of occupants.

This document provides an in-depth exploration of retrofit concepts, covering:

  • The policy and technical context of retrofit in the UK
  • Retrofit measures and their effectiveness
  • PAS 2035 and compliance standards
  • The Whole House Approach and the Fabric First principle
  • Key risks, best practices, and evaluation strategies
  • Funding schemes and financial incentives
  • Monitoring and long-term performance assessment

The Policy Context of Domestic Retrofit

UK Government Targets & Net-Zero Goals

The UK Climate Change Act (2008) set ambitious targets:

  • By 2035: Reduce emissions by 78% compared to 1990 levels
  • By 2050: Achieve Net Zero emissions

The Scale of the Challenge

  • 27 million homes require retrofit improvements to meet net-zero targets.
  • This equates to nearly 3,000 homes per day from now until 2050.

Fuel Poverty & Retrofit

  • Properties with uninsulated walls have the highest fuel poverty rates (21.8%).
  • Properly insulated homes reduce this rate to 11.5%, highlighting the wider community benefits of nationwide retrofit programs.

Energy Use in Domestic Buildings

Variations in Energy Use Between Dwellings

Each household is unique in terms of:

  • Thermal properties
  • Occupancy levels and schedules
  • Heating and ventilation habits

Typical Energy Consumption Breakdown

In a poorly insulated home:

  • Space heating: 60%
  • Hot water: 24%
  • Lighting & appliances: 16%

Heat Loss Distribution in an Uninsulated Detached Home

  • Walls: 35%
  • Roof: 25%
  • Floor: 15%
  • Doors: 15%
  • Windows: 10%

These figures highlight the importance of improving insulation and heating system efficiency.

Current Retrofit Standards

PAS 2035 Framework

PAS 2035 provides a structured process for achieving high-quality retrofit projects, including:

  • Whole House Approach – Considering how all measures interact.
  • Risk Assessment – Evaluating moisture, thermal, and ventilation risks.
  • Compliance Standards – Ensuring installations meet TrustMark and PAS 2030 requirements.

Additional Retrofit Standards

  • EnerPHit (Passivhaus standard for retrofit) – Focuses on ultra-low energy consumption.
  • UK Net Zero Buildings Standard – Limits operational and embodied carbon.
  • LETI (Low Energy Transformation Initiative) – Aims for a 60-80% reduction in energy use.
  • AECB CarbonLite Retrofit – Includes airtightness, ventilation, and low-carbon heating requirements.

Retrofit Measures

Insulation Improvements

  • Loft Insulation – Reduces heat loss through the roof by up to 25%.
  • Cavity Wall Insulation – Reduces energy loss through walls by up to 35%.
  • Solid Wall Insulation (IWI & EWI) – Essential for properties without cavity walls.
  • Floor Insulation – Prevents heat escaping through uninsulated ground floors.

Heating System Upgrades

  • Gas Boilers (FTCH & Replacement) – High-efficiency condensing boilers.
  • Air Source Heat Pumps (ASHPs) – Extract heat from the air for low-carbon heating.
  • Solar Thermal – Uses sunlight to heat water, reducing reliance on fossil fuels.

Ventilation & Indoor Air Quality

  • Mechanical Ventilation with Heat Recovery (MVHR) – Reduces energy loss while ensuring good air quality.
  • Demand Controlled Ventilation (DCV) – Adjusts ventilation levels based on indoor conditions.
  • Trickle Vents & Background Ventilation – Prevents damp and mould in airtight homes.

Renewable Energy Solutions

  • Solar PV & Battery Storage – Provides renewable electricity for the home.
  • Micro-CHP & Biomass Heating – Low-carbon alternatives to gas heating.

The Whole House Approach & Fabric First Principle

Whole House Approach

  • Ensures measures are compatible and do not cause unintended consequences.
  • Prevents issues such as condensation, damp, and overheating.

Fabric First Approach – The Right Retrofit Order

  1. Fix Building Defects – Repair damp, roofing issues, or structural defects.
  2. Insulate & Improve Airtightness – Prioritise insulation and draught-proofing.
  3. Ensure Proper Ventilation – Address air quality with MVHR or MEV systems.
  4. Upgrade Heating Systems – Install the most suitable heating solution for the new energy demand.
  5. Consider Renewable Energy – Solar PV, battery storage, or other renewable sources.

Risks & Challenges in Retrofit Projects

Common Retrofit Risks

  • Damp & Mould Growth – Due to insufficient ventilation in airtight homes.
  • Thermal Bridging – Areas where insulation is not continuous, leading to heat loss.
  • Overheating – Particularly in well-insulated homes without appropriate shading.
  • Incompatible Measures – E.g., heat pumps installed in homes without prior insulation upgrades.

Mitigation Strategies

  • Conducting thorough moisture risk assessments.
  • Ensuring proper ventilation strategies accompany insulation improvements.
  • Using thermographic surveys to detect heat loss points before installation.
  • Implementing performance monitoring post-retrofit.

Funding & Grants for Retrofit

Available Schemes

  • Energy Company Obligation (ECO4) – Provides funding for insulation and heating improvements.
  • Great British Insulation Scheme (GBIS) – Supports insulation upgrades in homes with poor EPC ratings.
  • Boiler Upgrade Scheme (BUS) – Offers grants for heat pumps and biomass boilers.
  • Social Housing Decarbonisation Fund (SHDF) – Supports large-scale retrofit programs in the social housing sector.

Monitoring & Long-Term Performance

Why Monitoring Matters

Monitoring ensures retrofit measures deliver expected energy savings, comfort, and durability.

Key Monitoring Techniques

  • Energy Use Monitoring – Compares post-retrofit energy consumption to initial estimates.
  • Thermographic Imaging – Identifies heat loss areas and insulation performance.
  • Air Quality Sensors – Measures CO₂, humidity, and ventilation efficiency.
  • Occupant Feedback Surveys – Ensures retrofit improvements align with user experience.

Smart Monitoring Solutions

  • Switchee Smart Thermostat – Tracks heating efficiency and air quality.
  • Aico Ei1025 Sensors – Monitors temperature, humidity, and CO₂ levels.
  • iOptAssets.com – Manages energy performance across housing portfolios.

Conclusion

Retrofitting is a crucial component in meeting climate goals, reducing energy bills, and improving housing conditions. A properly managed approach ensures compliance with PAS 2035, maximises energy efficiency, and prevents unintended consequences. Whether you’re a homeowner, landlord, or housing provider, an effective retrofit plan can significantly enhance comfort, sustainability, and property value.