Building type
The plant holds the hall at its set point; the envelope decides how hard it works. A continuous closed-cell layer seals the roof, walls and soffits, keeps cooled surfaces above the dew point and, coated, carries the fire classification the strategy asks for.
01What is happening
A data hall is held at a tight temperature and humidity by cooling plant that runs all year. Every gap in the roof, walls and soffits is heat and moisture the plant has to deal with, and every cooled surface that meets warm, humid air is a condensation risk: roof voids over the halls, plant areas, the soffits of raised floors and chilled pipework. Nobody wants water near the racks.
It is not a plant fault. The plant is working against the envelope; fixing the envelope lets it work less.
It is not solved by more cooling. More cooling makes more cold surfaces to condense on.
It is not always the roof. Plant areas, soffits and pipework condense too, and the same layer treats them.
02What is applied
Closed-cell foam is applied from inside to the roof underside, the walls and the soffits as one bonded layer, closing laps, wrapping purlins and fixings and sealing penetrations. It is rigid, its own vapour control, and it does not shed fibres. Where the fire strategy requires a reaction-to-fire classification, the coated system carries it.
Schematic / not to scaleKeyed 1 to 5 below
Profiled sheet, composite panel or concrete. It stays as the weather line.
Dust, loose coating and contamination removed, with the hall's cleanliness regime respected.
Continuous, bonded, over 90 per cent closed cell. λ 0.027 W/mK is the NexSeal LE product figure.
Encapsulated by the application, and still bridges in the calculation.
B-s2,d0 belongs to the coated NexSeal LE and DC315 system, as tested. Technical space usually asks for it.
Applications on this building
The problems it answers: Air leakage and draughts Roof condensation Summer overheating Energy costs
03Working around the building
The clean time to seal a data hall is before the racks arrive. Where the facility is live, the work is planned with the operator under permit, in empty halls, plant areas or roof voids, with containment that keeps overspray and dust away from equipment. Nothing is sprayed over live kit.
Roof, walls and soffits sealed before containment, ducts and racks go in. Penetrations made later are sealed as they are made.
Method statement, permit to work, escorted access and the operator's change control before anyone arrives, to the site's own requirements.
Containment and extraction around the zone, equipment sheeted or excluded, applied thickness and coverage recorded into a QA pack for the file.
04Enverge NexSeal LE
Enverge NexSeal LE is a two component closed cell polyurethane, spray applied directly onto the prepared substrate. As it cures, it expands and sets into one rigid, continuous layer, bonding into corrugations, laps, fixings and awkward junctions without being cut, jointed or mechanically fixed.
That matters because most insulation problems start at the gaps.
Board systems can leave voids at ribs, laps and junctions, and every gap is a potential cold bridge where warm internal air meets a cold surface and condensation forms, hidden behind the insulation. NexSeal LE is applied as one continuous bonded layer, so there is nowhere for that to start: a sealed, stable building envelope that controls condensation, reduces heat loss and protects the structure underneath.
HOLVEM also installs open-cell foam. It is a different product with its own data sheet, specified for different objectives: hybrid build-ups, sound absorption, or where the layer has to breathe. It is not what goes onto a cold sheet or a cold soffit. Open-cell system data · Closed-cell system data
05How we check
A data hall has a set point, not a season. The condensation risk analysis runs with the hall's temperature and humidity inside and the weather outside; the U-value calculation puts a figure on the heat gain the plant no longer has to remove; the fire strategy decides the coating.
The roof, wall and soffit build-ups are checked with the hall's controlled conditions inside and the outside climate through the year, to BS EN ISO 13788 and, where the case warrants it, a transient WUFI analysis to BS EN 15026. It states where vapour would condense and what the layer has to do to stop it.
How the analysis worksThe calculation is done for this build-up to BS EN ISO 6946 with purlins and rails in it, so the reduction in heat gain is a figure the M&E engineer can put against the plant.
U-values and Approved Document LTechnical space usually carries a reaction-to-fire requirement. The coated NexSeal LE and DC315 system achieves B-s2,d0 to BS EN 13501-1 in the build-up tested; the facility's fire strategy decides where it is specified.
Fire performance and coatings