Heating column

A heating riser (or vertical pipe) is the vertical pipe that distributes hot water (supply and return) to emitters (radiators, underfloor heating via manifolds) across multiple floors. It is the axis that connects the substation/boiler to each floor, with branch connections at each level, isolation/balancing devices, continuous thermal insulation, and acoustic and fire-resistant features. Its quality determines the temperature difference (ΔT), noise levels, comfort, and energy bill.

Heating column: definition and components

A column can be a two-pipe (most common) or an older single-pipe design. It includes:

- Isolation valves at the base/top and sometimes by level to allow intervention without shutting down the building.

- Balancing : ΔP regulators, control valves or flow meters on connections; bypass at the last level if necessary.

- Air purging : automatic air vents at the top, drain connections at the bottom.

- Supports & expansion : suitable collars, expansion gaps, compensators if large heights.

- Thermal insulation : continuous (including elbows/valves/supports with insulating inserts) to limit losses and overheating of ducts.

- Firestopping : CF penetrations (intumescent sleeves/collars) and airtightness.

- Materials : steel, copper, multilayer (oxygen barrier), stainless steel depending on premises.

- Instrumentation : supply/return thermos, ΔP sockets, sometimes heat meters per column/batch.

Hydraulically, the riser is integrated into a variable flow network (2-way valves + VFD pumps) or a constant flow network (3-way valves, less common); the BMS controls the flow temperature and ΔP. In co-owned properties, heat distributors or individual meters require rigorous balancing of the risers.

Advantages, limitations and points to consider

Interests

• Efficient vertical distribution: few horizontal linear units, limited losses.
• Maintenance is made easier with well-placed isolation devices and drains.
• Measurement and distribution possible by column/batch (remote reading).

Boundaries

• Noises/whistling if ΔP is too high or valves/sliders are incorrectly sized.
• Losses if insulation is inadequate (overheated sheathing/cupboards).
• Neglected expansion = creaking, stresses on crossings.
• Old single-pipe system: imprecise regulation, cascaded radiators.

Points to consider

• Sizing: moderate speeds (erosion/noise), suitable Kvs of the valves, sufficient authority.
• Balancing: ΔP regulator per column, PICV on terminals, preset table.
• Target ΔT: aim for 15–20 K in heating for cold returns (condensing boiler/heat pump more efficient).
• Thermal insulation: treat supports/valves (removable mantles), vapor barrier seals carefully in cold areas.
• Firestop: check each penetration (installation report), seal against air to prevent unwanted chimneys.
• Purging & water quality: upstream purge valves, prior descaling, inhibitor, bottom sieve filters.
• Renovation: switching from single pipe to double pipe or horizontal per dwelling improves regulation and individualization but involves work on ducts/services.
• GTB/VFD: ΔP sensor at the critical point, pressure reset according to valve opening; ΔT monitoring per column.

Anecdote — “A column that has regained its calm in Marseille”

In Marseille, a twin-pipe riser serving six floors was causing whistling noises and lukewarm radiators in the attic. Diagnosis: excessively high pressure difference (ΔP) at peak, oversized valves, and a lack of insulation in the pipe. Actions taken: a pressure difference regulator at the base of the riser, adjustment of the Kvs values ​​of the floor valves, insulating jackets on the valves/supports, and new air vents at the top. Result: silence, consistent temperature difference (ΔT) throughout the entire riser, and cooler return water… with a condensing boiler that finally operated within its optimal range.