Defining clearly what is meant by “cubicle insulation” (and avoiding a habitable-container detour)
Cubicle: booth or lightweight module (technical room, site welfare unit, electrical room), what you are really insulating
On site, cubicle insulation refers to a lightweight prefabricated booth. The most common cases are a technical room (HVAC, pumping, telecoms), a site welfare unit, a modular electrical room or a control module. You are therefore insulating an envelope with little mass, sometimes significant internal gains (equipment) and often intermittent occupancy. This is not a “housing” approach, nor an acoustic or decorative treatment.
Typical envelope constraints: vapour-tight skin, metal framing, sandwich panels
These modules often combine a steel frame with metal-faced sandwich panels. The result is many thermal bridges at corners, angles, frames and floor connections. The outer skin is highly vapour resistant. You therefore need a continuous warm-side vapour barrier, airtightness continuity and condensation control on the underside, especially in mid-season, which is why it is worth mastering dew-point calculation to secure material and assembly choices.
Choosing the right site approach: technical module/intermittent occupancy rather than housing
Frame the need around the actual use. Setpoint temperature, occupancy duration, dissipated power and air change. The most effective solutions are often external wall insulation under cladding to keep the frame on the warm side, or internal insulation using closed-cell materials without an air gap. In both cases, provide mechanical ventilation sized for occupancy and equipment heat gains.
Understanding the thermal defects in a cubicle: thermal bridges, overheating and condensation
Low thermal mass: very rapid temperature swings (summer and winter)
A cubicle is a lightweight envelope. Little mass, so little heat storage. The slightest internal load (people, UPS units, servers) or solar gain makes the temperature rise within minutes. In winter, the same effect works the other way as soon as the gains stop. To quantify it, record temperature drift over 30 minutes, dissipated power and ventilation rate. That is the starting point for a cubicle insulation package that performs in both summer and winter.
Frame thermal bridges: angles, corner frames, stiffeners, thresholds and floor junctions
The metal frame bypasses the insulation. The weak points are almost always angle profiles, corner frames, opening reinforcements, door thresholds and floor junctions. During the technical survey, check insulation continuity, through-fixings and take a surface temperature reading (IR camera or contact probe). These are your thermal bridge zones and condensation risks.
Water vapour: why a continuous warm-side vapour barrier is non-negotiable
The steel skin is highly vapour tight. Without a continuous barrier on the warm side, vapour migrates to the cold sheet and quickly reaches the dew point. The result is trapped water, corrosion, loss of lambda value and underside mould. Install a continuous vapour barrier with returns, sealed laps and treatment of all penetrations (services, boxes, ducts). And size the ventilation to the actual occupancy, not on a rough estimate.
External insulation: the solution that moves the frame to the warm side
Principle: continuous insulation + cladding, and removal of structural “cold lines”
On a lightweight envelope, external insulation is often the best lever for cubicle insulation. You install a continuous wrap (PIR, high-density mineral wool, or an equivalent build-up) followed by a breather membrane and ventilated cladding. The metal frame moves to the warm side. You break the linear thermal bridges of the studs and stabilise the wall temperature, thereby reducing the risk of condensation.
Detailing: corners, angles, frames, penetrations and fixings (limiting thermal bridges)
The gain depends on the junctions. Aim for insulation continuity and “accounted” fixings.
- Corners and angle profiles: overlap detailing, with no bare metal passing through. Use thermal breaks or insulating spacers.
- Frames: return the insulation into the reveals, then airtight sealing at the joinery line.
- Penetrations: airtight sleeves, thermal-break plates and durable sealing.
Underside and floor: addressing condensation and structural performance in service
On the underside, provide a mechanically protected insulation build-up. Add a breather membrane, rodent protection and suitably designed fixings. At floor level, seal peripheral air leaks, protect the insulation from moisture and check compatibility with service loads. Keep sensitive points accessible for inspection.
Internal insulation: closed-cell insulation without an air gap, when outside work is impossible
When to choose it: site constraints, footprint, access, maintenance and safety
This option makes sense when the cladding cannot be touched. No room on site, proximity of plant, secure zones, difficult MEWP access, or a need to keep the outer skin intact for maintenance. In cubicle insulation, you often balance performance against size. Plan for the loss of usable volume, access to equipment and maintenance clearances.
Suitable materials: closed-cell foam (sprayed/applied or boards) and continuity of the vapour barrier
Use a fully-contact closed-cell insulation. Sprayed PU foam or PU/PIR boards with taped joints. No air gap, otherwise you get parasitic convection and cold spots. Since the metal skin is not very vapour permeable, design for a continuous vapour barrier on the warm side. Seal joints with compatible sealant and tapes, and keep continuity to the returns of windows/doors and hatches.
Sensitive points: wall/ceiling/floor junctions and penetrations (cables, ducts, supports)
Heat losses occur at angle sections, floor rails, corners and panel ends. Close off these cold lines before “filling”. For each penetration, provide a sleeve, airtight collar and vapour-barrier reinstatement. Document the inspection: photos, tagging, and tie-in points in your report.
Mechanical ventilation and usage: size for occupancy to secure humidity control
Calculating fresh air by use: continuous occupancy, intermittent occupancy, or peaks
For a lightweight envelope such as cubicle insulation, start from the actual use. Continuous occupancy (guard post), intermittent (technical room), or peaks (meeting room, locker room). Size the fresh air for the maximum plausible occupancy, then reduce it during off-peak periods using a timer, occupancy sensor or CO2 control.
Avoiding the “airtight box” effect: exhaust/supply, air inlets, simple control
With a metal skin and continuous vapour barrier, leakage should not be relied on as an air inlet. Choose a clear strategy. Exhaust-only with dedicated air inlets and under-door transfer, or balanced ventilation if you need pressure control. A simple control with two speeds is often enough if the minimum and maximum flow rates are recorded in the project file. To set those flow rates and choose the terminals correctly, rely on dedicated air inlets and extract grilles.
Commissioning and checks: flow rates, airtightness, dew point and feedback in 2026
At handover, measure the flow rates at the terminals, record the values and check network airtightness. Cross-reference indoor humidity and surface temperature at thermal bridges to identify areas at dew point. In 2026, quality checks increasingly require evidence of commissioning, not just an installation manual.
