Insulation, heating, ventilation: where should your 2026 renovation start?

Clarify your renovation strategy before starting work

Define the goal: comfort, savings, DPE, escaping an energy sieve

Before signing the quotes, set your compass. Are you aiming for lasting comfort, lower bills, a better DPE, or escaping an energy sieve status. A clear goal avoids scattered work. You might, for example, aim for a DPE class improvement or more stable summer comfort, then align every trade with that target.

Start with an on-site diagnosis: weak spots, moisture, airtightness

An effective renovation starts on site. Identify cold zones, thermal bridges, signs of moisture, ventilation, then air leaks around joinery and hatches. An energy audit or infrared thermography can round out this walkthrough. The idea is simple. Envelope first, then systems, to avoid oversizing a heat pump.

Prioritise according to budget and 2026 grants: MaPrimeRénov', CEE, éco-PTZ

Build a step-by-step plan. Insulate and ventilate, then heat. In 2026, grants like MaPrimeRénov', CEE incentives and the éco-PTZ can be combined under the applicable rules. Check the caps, the eligible measures and the requirement to use RGE professionals. With an estimate of grants from the outset, your budget stays on track.

Follow the right order of work: insulation before heating

Tackle the envelope first: roof, walls, ground floors, joinery

In renovation, start by reducing losses. A well-insulated roof, treated walls, protected ground floors and consistent joinery — that's the foundation. You avoid oversizing the boiler or heat pump, and you gain comfort from the very first winter.

Manage thermal bridges and airtightness: avoiding "small slip-ups" that cost dearly

High-performance insulation isn't enough if air passes through everywhere. Treat the slab-wall junctions, window reveals, hatches, and service penetrations. Good airtightness limits draughts, condensation and mould. These details often make the difference on the bill.

Check the consistency of thicknesses and the continuity of insulation across the whole building

Think continuity. The same insulation level on comparable surfaces, clean junctions between trades, no "forgotten" zones. When the envelope is uniform, heating becomes a simple matter of adjustment. To go further, also keep in mind insulation continuity as a key principle. You can then choose properly sized, durable equipment.

Bring ventilation in at the right time for a healthy renovation

Choose the right solution: single-flow, humidity-controlled, or dual-flow MVHR depending on the home

After a renovation with insulation and tighter joinery, ventilation is no longer a "bonus". A single-flow MVHR is often suitable in existing homes. Humidity-controlled units adjust flow rates according to moisture. Dual-flow MVHR makes full sense if the envelope is well insulated and the ducts can be routed cleanly.

Coordinate the ductwork with insulation: routing, provisions, maintenance access

Plan the ductwork before closing up cladding, lofts or false ceilings. Provide for routing allowances, realistic diameters, and short runs to limit losses. Keep simple access to the unit, the vents and, for dual-flow systems, the filters for maintenance.

Prevent problems: condensation, mould, indoor air quality

Without air renewal, moisture gets trapped in wet rooms, then migrates towards cold surfaces. The result: condensation, mould, and discomfort. Adjust the flow rates, check the air inlets, and explain proper use. Regular maintenance protects indoor air quality over time.

Size the heating once heat loss has been reduced

Resize after insulation: power, emitters, controls

After insulation and air-leak treatment, redo the heat-loss calculation. This is the basis for avoiding an oversized unit. Aim for the right power, then check the emitters. Radiators, underfloor heating, fan coil units. With a well-performing renovation, you often move to low temperature, which also changes the controls.

Weigh up the solutions: heat pump, boiler, hybrid depending on context

Choose based on the required flow temperature, the climate, the electrical supply, the available space and the condition of the hydraulic network. An air-to-water heat pump is often relevant if your emitters accept 35 to 55°C. A condensing boiler can still make sense with gas available and high needs. Hybrid helps when winters are harsh or when high-temperature radiators are kept. Look for the right compromise.

Optimise actual performance: balancing, weather compensation curve, settings and commissioning

Performance is won at commissioning. Do the flow-rate balancing, set the weather compensation curve, cap temperatures, configure the time schedules. Check the key points: bleeding, valves, circulator, sensors. Monitoring over the first few weeks secures stable comfort and avoids callbacks.

Organise your project for a smooth, compliant renovation

Plan the trades: coordination, phasing, checks at every stage

A renovation is won on the schedule. Set out a clear phasing from the quote stage. Demolition, substrate correction, insulation, airtightness, ductwork/pipework, generator, then finishes. Plan a kick-off meeting, a weekly check-in and a sign-off for each trade. At every stage, check insulation thicknesses, vapour-barrier continuity, duct routing, and equipment commissioning before closing up.

Secure compliance and supporting documents: RGE, technical data sheets, sign-off reports, photos

Grants and CEE rely on an evidence file. Keep your RGE certification up to date and consistent with the work carried out. File detailed quotes and invoices, technical data sheets (references, performance), installation instructions, sign-off reports, and any certificates (airtightness, commissioning). Take dated photos before, during and after, with surface markers and treated zones. To go further, also see our advice on the evidence file to secure your applications.

Anticipate bottlenecks in 2026: equipment availability, lead times, inspection requirements

In 2026, expect variable lead times depending on the heat pumps, insulation materials and accessories. Order early, validate equivalences and keep a schedule margin. On subsidised projects, expect more requests for documents and more inspections. Simple, regular traceability avoids callbacks, and so avoids lost weeks.