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Thermal wallpaper condensation: when a liner belongs

Updated: 21 October 2026

Black spots are on the bedroom wall, and thermal wallpaper looks like the fix. Sometimes a thin liner takes a little chill off the surface. Sometimes it hides a leak. Thermal wallpaper condensation advice starts with which damp you have. Hang steps are on the [how to hang thermal lining paper](/hub/painting-supplies/insulating-wallpaper/sub/insulating-wallpaper-how-to-hang) page, and prices are on the [insulating wallpaper comparison](/hub/painting-supplies/insulating-wallpaper). Peter F. wrote this on 20 October 2026 from GOV.UK, National Energy Action and the Energy Saving Trust. It is not a medical verdict. A qualifying purchase can earn us a commission.

Black spots are on the bedroom wall, and thermal wallpaper looks like the fix. Sometimes a thin liner takes a little chill off the surface. Sometimes it hides a leak.

Our top picks

Wallrock Wallrock Dampstop Thermic

Best overall

Wallrock Wallrock Dampstop Thermic
5.1/10about £11.10
View offer
Erfurt Erfurt Heatsaver

Best value

Erfurt Erfurt Heatsaver
5.7/10about £12.99
View offer
Erfurt Erfurt Graphite Plus

Rank 3

Erfurt Erfurt Graphite Plus
6.2/10about £17.85
View offer
On this page
  1. 1.Condensation is the common pattern
  2. 2.What a thin liner changes
  3. 3.When the roll is the wrong cover
  4. 4.What to do as well as hanging paper

Condensation is the common pattern

Condensation is indoor moisture on a cold surface. National Energy Action describes black spots on cold outside walls, often behind furniture. Penetrating damp arrives as stains after rain. Rising damp is a tide mark, crumbling plaster, and a musty smell low on the wall. A wallpaper roll does not diagnose them. GOV.UK is blunt: wiping mould does not stop it if the surface stays cold and the air stays wet. For a small condensation patch, wipe it, cut the moisture, and warm the room. A liner can sit in that last part. It is not the whole plan. Widespread mould, or a very young, elderly, or unwell person in the house, is a reason to get help. Do not hang over a wet or salty wall. Choosing a type, once the wall is a decorating job, is the buying guide.

What a thin liner changes

Erfurt states 0.05 m²K/W for 2 mm Heatsaver and 0.125 m²K/W for 4 mm Graphite Plus. Those are the maker’s figures, not a percentage off your gas bill. In a mild case less moisture may drop out on that patch. Of 37 Heatsaver reviews, buyers often say a cold wall feels warmer. Nobody gives a measured change in the heating bill.
Wallrock Wallrock Dampstop Thermic

Testsieger

Wallrock Wallrock Dampstop Thermic
5.1/10about £11.10
View offer

When the roll is the wrong cover

Heatsaver is for a cold, dry wall. Dampstop Thermic is for the look of penetrating damp: 500 mm by 10 m, carried about 500 mm past the stain, hung with its own adhesive. In 50 reviews, people who used enough adhesive often say the mark stayed away. The outside fault is still there. It is not a damp-proof course, and it is the wrong roll for a wall that is simply cold. Rising damp, a tide mark, and salts are the stop signs. A foil or a closed foam can hold moisture in historic solid walls that were built to dry. wishFIRE tells you to avoid damp areas. A flame-resistant bullet on a 9 mm roll is not a mould treatment.

What to do as well as hanging paper

Run the extract fan on after the steam stops. Dry clothes away from the cold wall. A trickle vent painted shut is part of the cause. Steady heat matters as much as the sheet, and it still matters after the roll is up. Keep a gap behind large furniture. New spots after the first cold week mean the moisture never left. A 2 mm or 4 mm sheet is the wrong scale for a solid-wall upgrade, which is the insulating wallpaper versus internal wall insulation page. Call a professional for salts, rain stains, mould across a room, or a historic wall.

Common questions

Will insulating wallpaper stop black mould?
It can make a cold surface a little warmer, which can mean less condensation on that patch. It does not stop black mould by itself. GOV.UK’s point is that cleaning the surface does not prevent a return if the conditions stay the same. You still need less moisture and better ventilation. Heatsaver reviews talk about a warmer wall, not about mould disappearing for good.
Should I hang it over mould?
No. Clean a small area of condensation mould, dry the plaster, and only then hang. Papering over active growth hides it. If the mould is widespread, or someone in the home is at higher risk from it, get advice before you decorate. A roll is not a treatment.
How do I tell condensation from penetrating damp?
Condensation favours cold outside walls, steamy rooms, and corners behind furniture, often as scattered black spots. Penetrating damp is more often a stain linked to rain, a crack, or failed pointing. Rising damp is the low-level pattern with a tide mark and damaged plaster. If you cannot tell, do not cover the wall. The Energy Saving Trust sets out those differences for householders.
Is Dampstop for condensation or for a stain coming through?
It is sold for the appearance of penetrating damp, not as the first answer to ordinary condensation. You extend it about 500 mm past the patch and you use its adhesive. A cold dry wall that grows mould in winter is a Heatsaver-type problem, if it is a liner problem at all. Dampstop will not repair the brickwork that is letting water in.
What if I rent?
Do not paper over mould to make a room look lettable. Report damp and mould to the landlord, keep the area clean, and ventilate. A peel-and-stick foam on a damp wall is still a cover-up, and those listings tell you to avoid damp. Paste-the-wall liners also mark the plaster, which many tenancies do not allow.
Can a liner make a solid wall wetter behind the sheet?
It can, if the sheet is a foil or a closed foam and the wall was already passing moisture. That is why rising damp, salts, and historic solid walls are not a casual wallpaper job. A thin liner on a dry modern plaster face, after condensation has been reduced, is a different case. If you are guessing, stop and get the wall looked at.

Related pages

Best insulating wallpaper

Insulating wallpaper

Thermal lining paper: type, coverage, and adhesive

How to hang thermal lining paper: paste, then trim

Insulating wallpaper vs wall insulation, in practice

Sources

Public UK sources and manufacturer pages used for this comparison. Listing prices, stars and review counts are the amazon.co.uk figures saved for this set on 20 October 2026.

  1. Erfurt, Heatsaver 2 mm wall underliner (retrieved 20 October 2026)
  2. Erfurt, Insulating lining paper Graphite Plus (retrieved 20 October 2026)
  3. Erfurt, Understanding fire ratings (retrieved 20 October 2026)
  4. Erfurt, Wallrock Dampstop Thermic (retrieved 20 October 2026)
  5. GOV.UK, Damp and mould in the home (retrieved 20 October 2026)
  6. Approved Document B, volume 1, dwellings (retrieved 20 October 2026)
  7. Centre for Sustainable Energy, Internal solid-wall insulation (retrieved 20 October 2026)
  8. Homebuilding, Insulating wallpaper (retrieved 20 October 2026)