DSEAR, CO2 Recovery & Rooftop Solar on a Brewery

A warehouse roof is a blank canvas: a steel portal frame, a membrane, and nothing underneath but pallets. A brewery roof is nothing of the sort. Beneath it sits a live process plant, CO2 recovery, malt handling, a glycol chiller, a steam boiler, governed by hazardous-area rules that most rooftop solar installers have never had to open. That is not a reason to hesitate. It is the reason a brewery-literate installer earns their keep: the compliance detail is exactly where a generic, roof-is-a-roof quote quietly goes wrong.

Solar only ever attacks part of the problem, and honesty about that is where any serious conversation starts. Around 70% of a brewery’s energy is thermal, the wort boil, hot liquor, raising steam, and photovoltaic panels cannot offset that load directly. It is the roughly 30% that is electrical where solar does its work. Because refrigeration and glycol chilling run 24/7 through fermentation, a well-sized array sees self-consumption of typically 75-90%: nearly every unit you generate is used on site rather than exported. The economics are genuinely good (our cost guide walks the numbers). But the array that delivers them is being installed over a classified process area, and that is where DSEAR arrives.

Why a brewery roof isn’t a warehouse roof

The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) require an employer to assess and control the risk from substances that can cause fire, explosion or similar energetic events, and to classify any area where an explosive atmosphere may occur into hazardous-area zones. Warehouses storing dry goods rarely trigger this. A brewery triggers it in at least two places, and the HSE’s DSEAR guidance is the reference point every specialist should be able to cite.

Malt and grain dust, the genuine explosive atmosphere

Handling, milling and conveying malt throws off fine combustible dust. In sufficient concentration and confinement that dust is a textbook explosive atmosphere, and the areas around grist mills, silos, augers and dust-extraction plant are classified as ATEX dust zones (Zone 20, 21 or 22 depending on how often a cloud is present). Ignition sources are controlled inside those zones, which is precisely why a rooftop DC array matters. Photovoltaic strings are live in daylight, cannot be simply switched off at source, and carry a real DC arc-flash and arc-fault risk. You do not route DC conduit, mount a combiner box, or site an isolator through, above or adjacent to a classified dust zone without a Hazardous Area Classification (HAC) drawing telling you where the boundaries actually are.

CO2 recovery, a different hazard, still a controlled zone

Be precise here, because it is where hand-waved quotes overreach. The CO2 given off in fermentation and captured by a recovery plant is not flammable, the dominant danger is asphyxiation through oxygen displacement, managed with fixed gas detection, forced ventilation and confined-space controls rather than explosion protection. But it still shapes a solar install: CO2 vents, buffer tanks and recovery skids create zones where personnel access is restricted, where you cannot leave an operative working alone above a discharge point, and where roof plant, walkways and inverter positions have to be planned around the release points. A specialist reads the CO2 risk assessment before drawing a single cable run; a generalist finds out on the day.

ATEX zones and where the PV DC can (and can’t) go

The practical output of all this is the HAC drawing. Once you have it, the array design bends to it in three ways. First, routing: DC cabling, string inverters and DC isolators are kept clear of classified zones wherever the roof layout allows, so you never rely on an ignition source sitting inside an explosive atmosphere. Second, rated equipment: where a run genuinely cannot avoid a zone, the kit specified for that stretch must carry the correct ATEX/equipment category for the zone it sits in, you do not fit standard commercial gear and hope. Third, isolation and maintenance access: emergency shutdown, rapid DC shutdown at the array, and safe maintenance routes are all designed so an engineer never has to enter a hazardous zone to isolate the solar system. None of this is exotic. It is simply invisible to anyone who has only ever wired sheds, and it is one of several reasons we push back on the myths that solar on an industrial roof is a commodity job.

Food-safety roof works over an open process

A brewery is a food business. Roof penetrations, mounting rails and cable entries are being drilled and sealed above tanks, lines and packaging halls that are subject to retained Regulation (EC) 852/2004 on food hygiene, and very often to a BRCGS or SALSA audit standard on top. That imposes real constraints a warehouse install never meets: swarf, sealant, offcuts and debris cannot be allowed to reach an open product zone; penetration works are phased so they sit over closed vessels or non-production areas; and the works are scheduled around brewing, cleaning (CIP) and packaging runs rather than dictating to them. Get this wrong and you do not just risk a leak, you risk a contamination finding that threatens the audit certificate the brewery sells on.

F-gas on the glycol plant

Refrigeration is roughly 35% of a brewery’s electricity and the reason self-consumption stays high, so the glycol chiller is central to the business case, not a detail. It is also regulated. The chiller’s refrigerant charge falls under the F-gas regulations: mandatory leak checking, record-keeping, and work carried out only by suitably certified engineers, alongside the ongoing phase-down of high-global-warming-potential refrigerants. For a solar project the rule is simple and firm, rooftop mounting, cable trays and walkways must be designed so they never disturb the condensers, pipework or controls of the F-gas plant, and if any interface with that plant is unavoidable it is handled under F-gas certification, not by a PV crew improvising.

The rest of the survey a specialist actually runs

Three more checks separate a brewery survey from a warehouse one:

• Structural (MCS MIS 3002). Mounting design has to meet the MCS structural standard, and brewery roofs are rarely uniform, historic tower-brewery roofs, insulated cold-store panels over the fermentation hall, and mixed spans all need a proper structural assessment rather than a generic loading assumption.
• Asbestos. Any building predating 2000 may contain asbestos cement sheeting or linings; under the Control of Asbestos Regulations 2012 a refurbishment/demolition survey precedes roof penetrations. Many industrial and historic brewery buildings are squarely in that bracket.
• Fire (RC62). Insurers increasingly treat the RC62 guidance on roof-mounted PV as a de-facto condition of cover. A brewery with a taproom, stored stock and a packaging line carries a real fire loading, so array layout, cable protection and fire-service access are designed with the insurer in mind from the outset, qualitatively, this is about cover staying valid, not a box to tick after the event.

What this means when you pick an installer

None of the above changes the fundamentals: for most breweries solar remains a sound margin-defence move in a brutal market, and you can sense-check the payback yourself with our savings calculator or read the fuller argument on whether solar is worth it for a brewery. What it changes is who you let onto the roof. The right questions to ask are blunt: have you seen our HAC drawing, how are you routing DC around the dust zones, how will you protect the process below during penetration works, and how do you keep clear of the glycol plant’s F-gas circuit? An installer who answers those crisply is worth a premium. One who looks blank should never quote your roof.

If you would like a survey that treats your brewery as a hazardous-process site rather than a shed with a big roof, request a quote with your meter data and roof details. It is also worth checking what funding and reliefs apply before you commit, see our grants and funding page for the current picture on capital allowances and sector schemes.

Common questions

Do the malt-dust and CO2 zones stop us fitting solar?

No. They shape the design, not the decision. A Hazardous Area Classification drawing tells the installer where the classified zones sit; DC cabling, isolators and inverters are then routed clear of them wherever possible, with correctly rated equipment used only where a zone genuinely cannot be avoided. It adds survey and design work, which is the point of using a brewery specialist, but it does not rule out an array.

Is the CO2 recovery plant an explosion risk from the solar system?

The CO2 itself is not flammable, so it is not an explosion hazard, the primary danger is asphyxiation from oxygen displacement, controlled with gas detection and ventilation. The reason it still matters to a solar install is access and layout: vents and skids create zones where personnel and roof plant have to be positioned carefully, so the array is planned around them.

Will installation shut the brewery down?

Rarely a full shutdown. Roof penetration and cabling works are phased around your brewing, CIP and packaging schedule, with food-safety controls (retained Reg 852/2004, and any BRCGS/SALSA requirements) applied so debris cannot reach open product. Expect coordination, not closure.

We’re in a listed tower brewery, does that change things?

Yes. Listed status means Listed Building Consent is required before roof works, and historic roofs need careful structural assessment and asbestos checks. It is very doable, but it is heritage-and-compliance work, not a standard commercial fit, so factor the extra survey time into your timeline.