Conservation & Heritage Issue 50 Winter 2025/Spring 2026 - Flipbook - Page 108
Once you introduce the wrong material or detailing into
a heritage roof, you change its entire behaviour. Moisture
movement, expansion and contraction, corrosion, and even
colour mismatch can all affect how that element performs
and how it weathers over time. In conservation work, what
may seem like a cost saving often leads to higher long-term
repair costs, and sometimes irreversible damage.
There’s a craft dimension too. When installers are trained
in heritage methods, traditional leadwork, correct flashing
detailing, or the use of breathable finishes, the results speak
for themselves. But when untrained contractors attempt
to install conservation features using modern methods or
incompatible materials, the failures may take years to surface,
long after the project has been signed off.
Lessons from ECO4: systems without scrutiny
The hidden costs of “value engineering”
The ECO4 audit results are a warning about what happens
when oversight, competence, and accountability are diluted.
The phrase “value engineering” was once about intelligent
design optimisation. Today it’s often shorthand for “how can
we make it cheaper?”
The retrofit sector has become littered with acronyms,
schemes and certifications that promise quality assurance
but often deliver little more than bureaucracy. Installers
rush to meet volume targets; assessors approve designs
remotely; and contractors under price to win work, relying
on substitutions and short cuts to recover margins. The
outcome is predictable, systemic underperformance.
On a spreadsheet, replacing a bespoke stainless-steel rooflight
with an imported aluminium version might look like sensible
rationalisation. To a client unfamiliar with the materials,
both may appear similar in shape and function. But the
performance differences are profound.
Aluminium, particularly in coastal or exposed locations,
is highly susceptible to corrosion when coatings fail.
Condensation within roof cavities can accelerate degradation,
leading to frame blistering, leaks, and staining. From the
ground, these defects might appear as minor blemishes;
up close, they often reveal serious water ingress and decay
around rafters or plasterwork.
That same pattern occurs in parts of the construction and
heritage sectors whenever decision-makers prioritise upfront
savings over long-term value.
For instance, substituting a properly engineered 316L
stainless-steel conservation rooflight for a cheaper mild steel
or aluminium imitation might trim a few hundred pounds
off a specification. But over the lifespan of the building,
the consequences are clear: corrosion, water ingress, failed
seals, discolouration, and in many cases, replacement within
a decade. In contrast, a correctly detailed and installed
stainless-steel unit can last the lifetime of the building with
minimal maintenance.
It’s a textbook example of what economists call false economy,
and one that the ECO4 report has just demonstrated on a
national scale.
Heritage retrofit demands skill, not shortcuts
True conservation is about more than visual replication.
It’s about respecting a building’s materials, structure, and
performance, and intervening in ways that preserve rather
than undermine them. That demands knowledge, skill and
time.
Unfortunately, those are precisely the things that are hardest
to account for in procurement frameworks designed around
lowest cost. When funding models or tender criteria reduce
heritage retrofit to a tick-box exercise, the industry inevitably
responds with standardised, lowest-price solutions.
Yet, heritage buildings rarely conform to standard. Their roof
pitches, joist spacing, or internal liners might all vary subtly,
meaning that a “standard size” or “universal fit” product
rarely integrates properly. That’s why bespoke manufacturing
remains essential in conservation work. A handcrafted
rooflight, built precisely to fit the existing structure, respects
the fabric of the building and avoids the need for invasive
alterations that compromise integrity.
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