Efficiency table: distribution on an insulated vs uninsulated network (2026)

Understanding what a heating distribution efficiency table measures

Useful definitions: distribution efficiency, linear losses, primary and secondary network

A distribution efficiency table estimates the share of heat that actually reaches the emitters, relative to the heat leaving the generator. It factors in linear losses, meaning heat loss along the pipes (in W/m), influenced by length, diameter, insulation and the temperature difference with the space being passed through. To go further on this point, see heat loss along pipes. We often speak of the primary network between the generator and manifolds or heat exchanger, then the secondary network to the radiators or the floor.

Why network insulation changes everything: heat loss, temperatures, run time

Correctly insulating the network reduces heat loss in unheated areas (garage, loft, crawl space). As a result, the flow temperature can sometimes be lowered for equivalent service, which also helps a heat pump. Fewer losses also mean a shorter operating duration and more stable returns for the controller.

Common site mistakes: confusing generator efficiency and distribution efficiency

Classic mistake: taking the boiler efficiency or heat pump COP as if everything reached the home. The distribution efficiency table is about the network. Other pitfalls: forgetting uninsulated sections (valves, tappings), neglecting balancing, or reading a value outside the correct temperature regime. In 2026, with lower-temperature systems, these details quickly weigh on the bill.

Insulated vs uninsulated network: comparing efficiencies in real cases

Influence of the route and length: loft, crawl space, unheated rooms

On a distribution network, efficiency often comes down to very concrete details. The longer the route, the more heat losses add up. And when the pipes run through a loft, a crawl space, a garage or a cellar, heat goes straight into cold zones. An insulated network (continuous lagging, treated fittings) limits these leaks, stabilises the temperature at the emitters and avoids overheating the production unit to compensate.

Effect of flow and return temperatures: radiators, underfloor heating, domestic hot water

At a high flow temperature, losses on the pipework increase, especially if the network isn't insulated. And on the generator side, a return that's too hot degrades the gain of a condensing boiler and lowers the COP of a heat pump. High-temperature radiators, long loops, domestic hot water at 55–60°C: everything pushes temperatures up. Underfloor heating, with lower flow temperatures, leaves more margin and is less forgiving of network insulation defects.

Typical renovation cases: 1970s-90s homes, co-ownership buildings, extensions

1970s-90s homes, boiler in the basement and pipes snaking through unheated spaces. The priority is often to insulate the accessible sections before touching the emitters. In co-ownership buildings, uninsulated risers and service ducts create imbalances and "lukewarm" rooms. On an extension, the longer network requires zoning and balancing to keep a consistent flow rate without unnecessarily raising temperatures. To go further on the network's impact, see how distribution efficiency varies by emitter type.

How to read and use the efficiency table to decide on network work

Simple method: identify the loss points and prioritise insulating the critical sections

Start from the efficiency table and note, for each diameter, the linear loss based on the water temperature and the surroundings (heated or not). On your distribution network, rank the sections by length, temperature, and operating time. Treat the basement, garage, loft sections and the generator outlets first. This targets the losses that weigh most heavily on seasonal efficiency.

Choosing the insulation and thickness: points of attention (continuity, thermal bridges, fittings)

Thickness is chosen to reach the targeted performance level, not "by feel." Check temperature resistance, moisture behaviour, and fire reaction. The golden rule is continuity. Elbows, valves, flanges and supports must be lagged with suitable fittings, otherwise thermal bridges cancel out part of the gain.

Costing and client pitch: efficiency gains, comfort, and consistency with a full renovation

Turn the before/after loss difference into kWh then into euros, using a realistic assumption for heating hours. You get concrete gains, plus improved comfort and temperature stability. Present this as a logical building block of a full renovation, with possible grants via CEE depending on the case. To estimate the insulation level to target, you can rely on the concept of optimal insulation thickness.

Distribution, efficiency and grants in 2026: integrating the network into your files

Link with MaPrimeRénov' and CEE: when the network affects the overall energy gain

In MaPrimeRénov' and CEE, the distribution network matters because it affects seasonal efficiency. An uninsulated pipe in a garage or crawl space means "lost" kWh that reduce the overall gain in the audit and simulations. In your files, aim for a coherent whole, not just the generator.

Consistency with the energy audit and scenarios: avoiding "oversizing" a heat pump because of network losses

If network losses are high, the calculated need rises and the heat pump ends up oversized. The audit and scenarios must factor in pipe insulation, balancing and the lowering of the flow temperature. This secures the sizing and limits consumption discrepancies after the work.

Traceability and documents to provide: photos, technical datasheets, mapping of lengths and unheated zones

In 2026, checks remain strict. Prepare simple traceability.

• Before and after photos. Overview, close-ups of specific points.
• Technical datasheets. Fire rating, thickness, lambda value, temperature compatibility.
• Mapping. Lengths, diameters, runs through unheated zones, dated plans or sketches.

With Argile: securing your distribution choices and speeding up costing (without spending a whole day on it)

Quick energy diagnosis: comparing the impact of an insulated vs uninsulated network on overall efficiency in a few minutes

In a few minutes, you test two distribution variants. Insulated or uninsulated network. You immediately see the effect on overall efficiency, losses in unheated spaces and expected comfort. Handy for deciding without redoing the same calculations three times.

Feasibility analysis and constraint mapping: cold zones, technical runs, likely lengths via Open Data

Argile cross-references your site information with Open Data. You spot cold zones, likely technical runs, network lengths to anticipate and points of attention. The result: your distribution choices are more reliable from the very first visit.

Integrated quotes and grants: pre-costing, detailed quote and MaPrimeRénov'/CEE estimate to better sell full renovation

You go from scenario to quote without starting from scratch. Pre-costing, detailed quote, and estimate of MaPrimeRénov' and CEE grants, staying consistent with standardised operations. This gives you a clearer remaining cost to present and makes it easier to sell a full renovation. To frame this process, you can also rely on a digital workflow from technical visit to quote.