Existing radiators can sometimes remain in a heat-pump retrofit, but a universal retention percentage is not a design method. The decision depends on each room’s heat loss and the actual radiator output at the proposed water temperatures. This guide owns radiator assessment; floor-heating design is covered separately.
Emitter output and room comfort
Record radiator manufacturer, type, dimensions and condition. Obtain output data with mean water temperature and room temperature, including any correction method. A catalogue output at a boiler rating condition cannot be carried across unchanged to a lower-temperature heat-pump system.
Matched performance data
Compare each corrected output with the room design load. If a room is short of capacity, consider reducing heat loss, increasing emitter area or using a suitable fan-assisted unit. Check space, sound, electrical needs and manufacturer data rather than assuming one panel type will solve every room.
Hydraulic design checks
Review pipe sizing, pressure losses, pump duty, hydraulic balancing and minimum flow when thermostatic valves close. A buffer or hydraulic separator should solve a documented flow or volume requirement; it can also introduce mixing and losses if used without a clear purpose.
Supplier evidence and responsibilities
Set weather compensation and commissioning readings after installation. Lower flow temperature can improve performance, but no fixed efficiency increase per degree applies to every model and condition. A distributor quotation should include the emitter assessment and specify who owns the final hydraulic design.
Sources and further reading
Before requesting a project quotation
| Check | Information to prepare |
|---|---|
| Project scope | State the country, project type, operating conditions and required delivery date. Identify which decisions still need an installer or designer. |
| Topic-specific evidence | room heat loss and radiator output at the proposed temperatures |
| Responsibility and acceptance | Record who supplies, installs, commissions and services the equipment. Ask which documents and checks are included, and confirm exclusions in writing. |
This checklist helps define a request; it is not a model performance claim, installation design or promise of availability.
Relevant equipment · Request a project quotation — Emitters, hot water and cooling · About Thermovo
Continue your project planning
Heat Pumps and Underfloor Heating: Design Rules for Maximum Seasonal Efficiency · How to Choose a Heat Pump: Six Questions Before You Buy
