Ask most people where clothes moths live and they’ll point at the wardrobe. Ask a pest controller and they’ll often point at the building itself.
Moth larvae feed on keratin, the protein in wool, hair, feathers and silk. British buildings contain far more of it than most site teams realise, from the hair binding Victorian plaster to the birds’ nests packed into the eaves, and increasingly in the natural insulation being specified for low-carbon work. Renovation disturbs the old sources. Sustainable specification can introduce new ones.
For contractors and renovators, that makes moths worth five minutes of attention. Infestations that “appear from nowhere” weeks after a project completes have a habit of tracing back to something opened up, or built in, during the works.
What Moth Larvae Actually Need
The adults are irrelevant; they don’t feed at all. All the damage comes from larvae, which want three things: keratin to eat, background warmth, and darkness without disturbance.
A building under renovation supplies all three in unusual quantities. Voids get opened and re-sealed. Old organic materials get exposed. Heating goes in, or gets upgraded. And whole areas sit undisturbed for weeks between trades. It’s a better breeding environment than any wardrobe.
The Old Sources: What Strip-Out Uncovers
Period properties in particular tend to hide decades of larval food in the fabric. The usual suspects on an opening-up:
- Birds’ nests. Eaves, soffits, disused chimneys and roof voids collect nests full of feathers and detritus, and abandoned nests are a classic reservoir for textile pests. A loft that’s had decades of sparrow and starling traffic can seed an infestation into the rooms below once works connect the spaces.
- Hair-bound plaster. Lime plasters in older buildings were routinely reinforced with animal hair. Larvae can graze the exposed hair content once walls are opened, and disturbed plaster debris spreads it around the site.
- Buried carpet, underlay and felt. It’s common to find wool carpet or hair felt underlay entombed under later floor build-ups, along with old sound-deadening layers. Perfect, undisturbed larval habitat, sometimes with a live population already in residence.
- Void debris. Decades of accumulated fluff, rodent nest material and dead insects in floor and ceiling voids all carry keratin.
The mistake is treating this material as inert rubbish. Strip a floor with an active carpet moth population and sweep-up alone can scatter larvae and eggs into every room the waste route passes through.
The New Sources: Natural Materials Done Carelessly
At the other end of the timeline, the push toward biobased, low-embodied-carbon materials has put sheep’s wool insulation and other natural fibres back into British buildings at scale, in retrofits especially.
To be clear, this is not an argument against wool insulation, which performs well and has genuine environmental advantages. Reputable manufacturers treat their products against insect attack precisely because moths would otherwise regard a wool-filled loft as a banquet. But the risk management sits in the details, and documented cases of moth problems in wool-insulated homes have made uncomfortable headlines. The pattern in those cases is rarely the branded product itself; it’s untreated or unverified material, offcuts left loose in voids, or poor detailing that leaves fibre exposed and undisturbed for years.
Three habits keep the sustainable option from becoming the infested one:
- Check the treatment. Specify wool and natural-fibre products with certified, durable insect-resist treatment, and keep the documentation with the O&M file.
- Don’t entomb offcuts. Loose trimmings swept into a void are untreated-edge material sitting in ideal larval conditions. Bag them out.
- Detail for disturbance. Exposed, accessible insulation gets checked; fibre buried behind fixed linings never does. Where natural fibre goes into inaccessible zones, treatment certification matters even more.
Good Practice at Strip-out and Closing Up
The cheap wins for site teams are mostly about sequencing and housekeeping:
- Remove birds’ nests, old wool floor coverings, felt and organic debris completely during strip-out, rather than covering over them
- Bag suspect material at source and take the shortest waste route out
- Vacuum voids and floor zones properly before closing up, edges and corners included
- Keep new soft materials, carpets and any stored client furnishings out of the building until dusty works are done
- On handover, tell clients what early moth signs look like: threadbare carpet edges, gritty debris, rice-grain cases, small golden moths at dusk
That last point buys goodwill. An owner who spots activity in month one has a small problem. One who spots it in month twelve blames the builder.
When the Building Already Has an Active Problem
Sometimes an opening-up reveals a live infestation: larvae in old underlay, cases along joist tops, moths rising off a stripped floor. At that point, the worst response is to press on and seal everything behind fresh finishes, because larvae will already be distributed well beyond the visible source and every missed pocket restarts the cycle under the new work.
The right sequence is treatment before reinstatement. A specialist moth removal service can survey the whole property, treat every affected area in one coordinated visit and confirm the infestation is cleared, so the new floors, insulation and finishes go down over a clean building rather than a live one. On occupied refurbishments it also spares the client months of chasing moths through rooms the contractor has just finished.
The Bottom Line
Moths aren’t a construction pest in the way rats or wasps are, which is exactly why they slip through. The industry disturbs their historic habitat every time it opens up an old building, and specifies their food supply every time natural fibre goes in without care.
Strip out organic material properly, verify treatment on wool-based products, clean voids before they close, and deal with live activity before reinstatement rather than after. Do that, and the sustainable, characterful buildings Britain is busy renovating stay that way: full of natural materials, and empty of the insects that eat them.
