We build one product, and we would rather it fitted than sold

It is the reasonable first reaction, and it comes from assuming the fabric is doing the structural job that the steel used to do. It is not. The aluminium skeleton takes every mechanical load in the system — dead weight, wind, guy pretension. The duct is a containment membrane and carries nothing.

Once you separate those duties, the containment requirement is much less demanding than it looks: hold gas at negative pressure, resist acid, resist temperature. Coated fabric does all three better than 316L does the acid part, which is why fabric expansion joints and fabric ducting have been standard in industrial gas handling for decades. What is new here is not the fabric. It is putting the structure on the outside so the fabric can be replaced.

The duct element targets a minimum Class E under EN 13501-1, and Option C with the ECTFE liner is rated to FM 4922, the duct fire safety standard. Formal EN 13501-1 testing is scheduled and not yet complete — that is stated on the standards page too.

The design case is different from a domestic chimney fire, because Exostack is specified for process exhaust at defined temperatures rather than solid fuel combustion. If your application has a credible soot ignition scenario, that is exactly the case where we will point you at a rigid refractory-lined stack instead.

Eight to twelve years for Option A, twelve to eighteen for Option B, fifteen to twenty for Option C. Replacement runs from €1,175 for the smallest Option A duct to €11,590 at the top of Option C, plus about four hours of labour.

We put those numbers on the economics page and inside the twenty-year total rather than leaving them for you to find later. The comparison that matters is not against a stack that needs nothing — rigid stainless typically wants relining or recoating around year twelve, and that means a crane and a shutdown.

In Germany the gate is the Bezirksschornsteinfeger signing off under §14 SchfHwG, and every system ships with the documentation pack that requires. The broader answer depends on DIBt national technical approval, which is in progress and not complete.

Being straight about it: if your project cannot proceed without approval in hand today, that is a legitimate reason to specify something else this time. Tell us your programme dates in the enquiry and we will give you an honest read rather than an optimistic one.

The duct is held in a true cylinder by radial cables at every ring level, so it is tensioned rather than loose — it does not behave like a flag. Slender guyed structures are genuinely susceptible to vortex-induced vibration, which is why the structural design includes a vortex shedding assessment to EN 1991-1-4 Annex B, and why that assessment sizes the guy system rather than the other way round.

The calculation is done per project against your actual wind case, not taken from a standard sheet, and it is in the pack you receive.

Minor damage is repairable in place with a patch kit. Serious damage means fitting a new duct, which is a four-hour planned job on a skeleton that never comes down — and it is the same procedure as an end-of-life replacement.

Compare that with a perforation in a rigid stack, which is a hot work repair at height or a section replacement with a crane. The failure mode is not worse here; the recovery from it is considerably cheaper.

The ropes are designed to EN 12385 with a safety factor of 3.0 and the assemblies arrive swaged and proof-loaded rather than made up on site. The annual inspection includes verifying tension on all three with a gauge, which is a thirty-minute rooftop check rather than a specialist visit.

We will not claim redundancy the design does not have. What the design does have is a system light enough that the consequence case is nothing like a 900 kg stack losing its restraint, and an inspection regime simple enough that it actually gets done.

The skeleton is outside the duct and never contacts the flue gas — that separation is the entire design. What it sees is ambient air, the same as every aluminium curtain wall, window frame and roof plant enclosure already on your site.

Where the ambient environment itself is aggressive — coastal, or downwind of another stack — we specify surface treatment for that exposure. It is a question we ask, not one we assume away.

Yes, and most customers do. There is no welding, no hot work, no crane and no lifting plant, so the requirement is two competent people with a working-at-height ticket and standard hand tools. The manual gives torque figures and sequence, and the tensioning tool and calibrated gauge are in the box.

We will attend the first installation on any site that wants us there and train your team while we do it. After that it is genuinely a maintenance department job.

It depends on the duct specification and on where the approvals stand when you order, so a number here would be a guess dressed as a commitment. Ask in your enquiry and you will get the current figure for your specification — including, honestly, the Halar® position if you are looking at Option C.