Whole-House Retrofit Design
Design of domestic energy efficiency retrofit measures that treat the entire building as a single, integrated system. From insulation specifications and ventilation strategies to heating system design and renewable energy integration, our retrofit design service gives you a coherent, technically robust plan that works for your specific property — not a generic one-size-fits-all approach.
Every design we produce considers the building's construction, age, orientation, exposure, occupancy patterns and the interaction between different building elements. This whole-house approach avoids the common pitfalls of piecemeal energy upgrades — such as condensation, mould, overheating and fabric deterioration — that can arise when measures are installed in isolation.
Retrofit Design Services
Our Home Surveyor & Property Valuer Accreditation & Professional Membership
Our Whole-House Retrofit Designs are carried out by qualified surveyors who belong to the professional bodies that set UK property standards. Every report is prepared to recognised guidance and is completely independent, so you can rely on the findings when you buy, sell or value a home.
What Is Retrofit Design?
Retrofit design is the process of specifying and detailing energy efficiency improvements for an existing building so that all the measures work together as a coherent, integrated system. It goes beyond simply picking products — it involves understanding how insulation, ventilation, heating, airtightness, moisture management and renewable energy interact within the unique fabric and context of your specific property. A professionally produced retrofit design ensures the measures are appropriate for the building, will deliver the intended energy savings and will not cause unintended consequences such as condensation, damp, overheating or structural decay.
What It Covers
- Whole-house assessment of the building's current thermal performance, construction and condition
- Specification of insulation type, thickness and location for walls, roofs, floors and any other relevant building elements
- Design of a ventilation strategy appropriate to the building's upgraded airtightness — including background, intermittent and continuous ventilation where needed
- Heating system specification including heat emitter sizing, controls, hot water provision and pipework considerations
- Assessment of renewable energy feasibility — including solar photovoltaic panels, solar thermal, air source heat pumps, ground source heat pumps and battery storage
- A written retrofit design report with clear specifications, construction details and a phased implementation roadmap
What It Does Not Cover
- Carrying out the physical installation of retrofit measures — we design and specify, we do not contract
- A market valuation of the property or an Energy Performance Certificate (EPC) — though we can advise on predicted EPC outcomes
- Testing of existing gas or electrical installations for safety compliance
- Structural engineering calculations for major structural alterations or extensions
- A guarantee that the measures will achieve a specific EPC band — EPC ratings depend on the accuracy of the RdSAP model used by the assessor and the quality of installation on site
When Do You Need Retrofit Design?
Retrofit design is appropriate in a range of situations — and there are some circumstances where it may not be the right service. Here is how to tell.
Suitable For
- Homeowners planning comprehensive energy upgrades
- Period property owners concerned about breathability
- Landlords targeting specific EPC improvements
- Architects and builders who need retrofit design input
Not Suitable For
- Single-measure installations without whole-house assessment
- Properties where no energy improvement work is planned
Not sure whether retrofit design is right for your project? Speak to a surveyor for free, no-obligation advice.
What Is Included in Our Retrofit Design Service
Every retrofit design we produce includes the following core elements as standard.
Whole-House Retrofit Design
A comprehensive design that treats the entire building as a single integrated system. We assess how each measure affects every other — so you avoid the unintended consequences of piecemeal upgrades such as condensation, mould, overheating and fabric decay.
Insulation Specification and Detailing
Detailed specification of insulation type, thickness, thermal conductivity and installation method for walls, roofs, floors and any other building elements. Includes construction detail drawings showing how insulation interfaces with windows, doors, eaves, verges and service penetrations to minimise thermal bridging.
Ventilation Strategy Design
A ventilation strategy designed to match the building's upgraded airtightness. Covers the specification of background ventilators, intermittent extract fans, continuous mechanical extract ventilation (MEV) or mechanical ventilation with heat recovery (MVHR) as appropriate for the building type, occupancy and budget.
Heating System and Controls Design
Specification of the heating system — including boiler or heat pump sizing, heat emitter sizing, hot water cylinder specification, system controls, zoning and pipework considerations. The design accounts for the reduced heat demand after insulation upgrades so the system is correctly sized and efficient.
Renewable Energy Integration Assessment
Assessment of the feasibility and specification of renewable energy technologies — including solar photovoltaic panels, solar thermal systems, air source or ground source heat pumps, and battery storage. We evaluate roof orientation, shading, structural suitability, planning constraints, grid connection requirements and financial payback.
How the Retrofit Design Process Works
From initial enquiry to final design report — clear, structured and transparent.
Initial Consultation
Contact us with the property details and your energy improvement objectives. We discuss your goals — whether it is a comprehensive whole-house retrofit, a phased programme or targeting a specific EPC rating — and provide a fixed-price proposal within 24 hours.
Site Assessment
A qualified surveyor visits the property to carry out a detailed assessment. This includes measuring the building, recording construction types, assessing existing insulation, ventilation, heating and airtightness, taking photographs and gathering all the data needed to produce the design.
Design Development
We develop the retrofit design off-site — specifying insulation systems, ventilation strategies, heating system upgrades and renewable energy options. The design is checked for moisture risk, thermal bridging and overheating risk using industry-standard methodologies and tools.
Design Report Delivery
Your comprehensive retrofit design report is delivered within 10 working days of the site assessment. The report includes specifications, construction details, a phased implementation roadmap and supporting calculations. We remain available to answer questions and discuss the design with you and your chosen contractors.
Why the Whole-House Approach Matters
Retrofitting a building one measure at a time — without considering how those measures interact — is the single biggest cause of retrofit failure. Here is why the whole-house approach is essential.
Insulation Without Ventilation Causes Damp
When you add insulation, you change the way moisture moves through a building. If you increase airtightness without upgrading ventilation, moisture from cooking, bathing, washing and breathing has nowhere to go — and it condenses on cold surfaces. A proper retrofit design sizes the ventilation strategy to match the new level of airtightness, so your home stays warm, dry and healthy.
Heating Must Be Re-Sized After Insulation
A boiler or heat pump that was correctly sized for an uninsulated house may be massively oversized after insulation is installed — leading to short cycling, poor efficiency, higher running costs and reduced comfort. Equally, an undersized system will struggle to meet demand in cold weather. Our design calculates the upgraded building's heat loss so the heating system is sized correctly first time.
Period Properties Need Breathable Solutions
Older buildings — particularly those with solid walls, lime mortar and no damp-proof course — were designed to breathe. Applying modern impermeable insulation systems to a traditional building can trap moisture in the fabric, leading to timber decay, frost damage and long-term structural deterioration. Our designs specify vapour-open materials where appropriate so the building can continue to manage moisture naturally.
Phased Implementation Needs a Master Plan
Most homeowners retrofit in phases — loft insulation this year, wall insulation next, a heat pump the year after. Without an overarching master plan, each phase may be specified to a different standard and the later phases may not be compatible with the earlier ones. Our retrofit design provides a phased roadmap so each stage builds on the last — you can spread the cost while keeping the technical coherence of a single integrated design.
Retrofit Design Questions
What does retrofit design cover?
Retrofit design covers the specification and detailing of energy efficiency improvements tailored to the specific building. This includes: the type, thickness and location of insulation in walls, roofs and floors; the ventilation strategy to ensure good indoor air quality and moisture management; the heating system specification including controls; window and door specifications; airtightness measures; and — where appropriate — renewable energy technologies such as solar panels or heat pumps. Every design considers the building's construction, age, orientation, exposure and the occupants' needs.
Do I need retrofit design or can my builder figure it out?
While many builders are highly skilled, the physics of building performance is complex and the consequences of getting it wrong can be severe — damp, mould, condensation, overheating and even structural decay. A professional retrofit designer with surveying qualifications understands building physics, moisture risk and the interaction between different building elements. A PAS 2035-compliant design gives you confidence that the measures will work as intended and not cause problems later. For government-funded schemes, a professional design is mandatory.
What is PAS 2035 and does my project need to comply?
PAS 2035 is the British Standard framework for domestic retrofit, introduced by the government in response to the failure of earlier retrofit schemes that were delivered to poor standards. It sets out a whole-house, risk-based approach to retrofit design and installation with defined roles — including a Retrofit Coordinator, Retrofit Assessor, Retrofit Designer and Retrofit Installer. If your project is funded through a government scheme such as ECO, the Social Housing Decarbonisation Fund or the Home Upgrade Grant, PAS 2035 compliance is mandatory. Even for privately funded projects, the PAS 2035 methodology represents best practice and forms the basis of our retrofit design work. We can advise whether your specific project requires formal PAS 2035 compliance and, if so, how to meet the requirements.
How much does retrofit design cost?
The cost of retrofit design depends on the size and complexity of the property, the scope of the retrofit measures being considered and the level of detail required. A straightforward retrofit design for a typical three-bedroom semi-detached house starts from around £750 plus VAT. Larger, more complex properties — particularly older buildings with solid walls — will cost more because of the additional complexity involved in specifying appropriate vapour-open systems and managing moisture risk. We provide a fixed-price quote within 24 hours of your enquiry, and the price we quote is the price you pay. For multi-property portfolios and landlord projects, please contact us to discuss volume pricing.
Do you carry out the installation work?
No, we do not carry out the physical installation of retrofit measures. We are an independent surveying and design practice — our role is to assess, specify and design, not to install. This keeps us completely impartial. We have no financial interest in recommending one system over another, no ties to any manufacturer or installer, and no incentive to over-specify measures you do not need. The design report we provide is detailed enough for you to obtain comparable quotes from competent installers. We are happy to review contractor quotes and visit the site during installation to check that the work is being carried out in accordance with the design.
Do you cover my area for retrofit design?
We provide retrofit design services across all seven of our counties: Bedfordshire, Buckinghamshire, Cambridgeshire, Hertfordshire, Northamptonshire, Greater London and Oxfordshire. Our surveyors and designers are locally based and understand the local building stock — from Victorian terraces in London and Edwardian semis in Hertfordshire to stone cottages in Northamptonshire and thatched properties in Buckinghamshire. There are no travel surcharges for any location within our coverage area — the price we quote is the price you pay regardless of where you are within our seven counties.
Get a Fixed-Price Retrofit Design Quote
Free, no-obligation quote within 24 hours. Independent, impartial advice with no ties to installers or manufacturers.