Prioritising a retrofit comes down to choosing between five goals that do not lead to the same work: winter comfort, savings on the bill, moving off fossil fuels, summer comfort and preserving the fabric. The technical order stays the same whichever goal is chosen: secure the envelope first, loft and roof then walls and ground floors, deal with airtightness and ventilation straight after, and only size the generator once the required output has come down. Reversing that order means fitting a heat pump to the pre-works heat loss, so oversized, with short cycling and a degraded seasonal COP. It is also why a work plan is presented to the client by goal, and not by trade.
Priority: secure the building envelope with consistent insulation
Loft and roof: the first lever for cutting heat loss
Heat loss starts at the top. Continuous insulation of unheated or converted lofts, with no gaps left around hatches and junctions, is often one of the first priorities. Aim for an appropriate thermal resistance and take care with the junctions to limit thermal bridges.
Walls and ground floors: choosing the right technique for the building
For walls, external wall insulation reduces thermal bridging and protects the building's thermal mass. Internal wall insulation remains relevant in co-owned buildings or on protected façades, provided you plan for moisture, especially in older buildings. For ground floors, insulating from underneath, in the crawl space, or from above reduces the cold-floor effect.
Airtightness and ventilation: preventing pathologies after works
When you upgrade insulation, air needs to circulate in the right places. Address leaks at joinery and penetrations, then check that the mechanical ventilation system is properly sized and maintained. Otherwise, water vapour gets trapped. Condensation, mould, discomfort.
Priority: modernise the heating system in line with the insulation work
Heat pump, boiler, stove: recommending the right system for the need
After insulation, the required output drops. Your priorities become simpler to sort out: budget, space, use. An air/water heat pump suits houses with a hydraulic network well. A high-performance gas boiler can still make sense as a replacement if the home is connected to the gas network. A wood stove works as a supplement, or as the main heating system for small surfaces, provided you manage fresh air and storage. Aim for a sensible choice, not a race for kW.
Emitters and controls: gaining comfort without oversizing
The generator isn't everything. Check radiators, underfloor heating, flow rates and balancing. Add fine-tuned controls: a programmable thermostat, an outdoor sensor, thermostatic valves. With well-suited emitters, you lower the water temperature, gain comfort, and avoid the oversizing that hurts efficiency.
Anticipating technical constraints: electricity, noise, location, access
Before pricing the job, do a walkthrough of the sticking points. Site constraints to check:
- electrical supply, breaker rating, subscription
- outdoor unit location, neighbours, acoustics
- condensate drainage, penetrations, maintenance and delivery access
Priority: address domestic hot water for quick savings
Heat pump water heater, solar, dual-service heat pump: what to recommend in 2026?
In 2026, to replace an electric water heater, a heat pump water heater is often still a good compromise between cost, space and lower consumption. Solar thermal becomes very worthwhile if the roof is well oriented and usage is regular. A dual-service heat pump (heating plus hot water) mainly makes sense in a comprehensive renovation, when the goal is a single generator with low-temperature emitters.
Loops, pipework, pipe insulation: don't let the kWh slip away
Hidden losses in the hot water network can eat into your gains. Insulate pipes in cold zones, cut unnecessary lengths, and adjust the temperature. On a loop system, control the pump with a timer or demand-based control to limit circulation time.
Matching the solution to actual use: number of occupants, habits, volume
Size the system based on actual use. Number of occupants, baths or showers, morning and evening peaks. A tank that's too big heats for nothing. Too small, and it pushes you to raise the setpoint. Set your priorities, comfort, frugality, self-consumption, then adjust storage and production accordingly.
Priority: aim for a comprehensive renovation to maximise performance and subsidies
Sequencing the trades: the "envelope then systems" method to avoid callbacks
For a comprehensive renovation that holds up, start with the envelope. Insulating the walls, addressing thermal bridges, airtightness and ventilation. You limit defects and rework, and then size the heating and hot water systems on actual needs. The result: fewer callbacks and a better-calibrated installation. That order holds more easily when the works plan is built by objective, from the home to the measures retained.
2026 funding: combining ECO4 and the Great British Insulation Scheme in your recommendation
In 2026, funded measures remain a strong lever, provided the client is guided to the right route and the measures are eligible. Secure the key points: household and property eligibility, a TrustMark-registered installer working to PAS 2030:2023, and the retrofit assessment and design done before installation. To go further, see how the equivalent French schemes are handled. Your recommendation gains financial coherence and avoids bad surprises.
Retrofit assessment and EPC band gains: priorities by objective (EPC, comfort, budget)
The retrofit assessment required under PAS 2035 acts as a roadmap. To aim for EPC band improvements, prioritise insulation and ventilation, then the heating system. For winter and summer comfort, address the roof, walls and solar protection first. For a tight budget, propose a phased plan that keeps a clear direction, with measurable milestones and a target scenario.
Priority: make the site survey and pricing reliable to limit unforeseen issues
Site checklist: measurements, photos, points of attention and notes to record
Before pricing the job, lock down the site's priorities and keep one simple rule. Zero oversights. These findings are recorded during the visit, photos and equipment positions included.
- Measurements: insulated surfaces, heights, possible thicknesses, pipe/duct lengths, unit locations.
- Photos: electrical panel, equipment labels, loft, façades, access, drainage.
- Points of attention: moisture, existing ventilation, access constraints, co-ownership, suspect materials.
- Notes: protections, rework, penetrations, restoration, timelines and contingencies.
Pre-pricing and quotes: presenting clear, comparable scenarios
Offer 2 to 3 scenarios built on the same set of measurements. Compare them with separate line items, clear options and the same assumptions. Add a site contingency line and an indicative subsidy estimate, based on eligibility.
How Argile helps: quick diagnosis, feasibility, scenarios, quotes and subsidies
With Argile, you launch a diagnosis in under 5 minutes, check feasibility (building, climate, constraints), then generate scenarios and a detailed quote. The funding available is worked out automatically to explain the remaining cost to the client, without overpromising. Decide fast, based on consistent data.
