Seven in the Morning, Before the Kettle: Reading the Condensation in a Listed House

If the windows of your listed house have started to stream since the heating came on or the draughts were stopped, the house is usually telling you that the moisture made inside it has lost some of its old ways out. My advice is to seal nothing further for now. Read where the water settles first thing in the morning, give it a route out, and talk to your council before any fan or vent is cut into old fabric.

Last week I wrote about what to ask when the boiler fails. A new boiler, a fortnight of draught-proofing, a winter of keeping the doors shut: each one makes a house warmer, and each one changes how it deals with the water vapour that cooking, washing and sleeping put into the air. The best time to see that is early, before anyone opens a window or puts the kettle on. This is the walk I would take.

7.00: the bedroom window

Start in the room you slept in. Overnight, a closed bedroom fills with damp breath, and the coldest surface in the room collects it. On a single-glazed sash, that surface is normally the glass.

City of York Council's guidance note on historic windows, published in December 2025, puts the principle in one line: "Glazing should be the coldest part of an external wall." A few beads on the lower panes, wiped away at breakfast, are the window doing an old and useful job.

Condensation is not the fault; it is the house showing you where its coldest surfaces are.

So the question on this first stop is not whether there is water on the glass. It is where else the water has gone. Look at the sill, the bottom rail of the sash, the reveals either side, and the corner of the wall behind the curtain. Water that runs off the glass and lies in the joinery, morning after morning, is how sound timber begins to rot. A folded cloth along the sill is a humble tool, and I would use one.

7.15: the bathroom and its ceiling

Next, the room where the first bath or shower has just been run. Many bathrooms in old houses were made out of a bedroom or a dressing room long after the house was built, and some have no extract fan at all. If there is one, check that it actually runs and that it runs for long enough.

Then look up. The ceiling above a bath is where steam goes first, and old lime plaster and its paint will show brown spotting, flaking or a soft, powdery surface long before a wall does.

7.30: behind the wardrobe

Furniture pushed against an outside wall makes a cold, still pocket where air never moves. Pull the wardrobe or the bookcase forward and look at the plaster behind it. Grey or black spotting, or a musty smell, tells you that water vapour has found a surface cold enough to settle on and nothing to carry it away.

The first remedy is simple: move the piece a hand's width off the wall, and leave it there. In my piece on damp myths I warned against sealing a wet wall, and the same thinking applies here. The wall is the victim, not the cause.

7.45: the kitchen and the old fireplace

The kitchen makes more water vapour in an hour than most rooms make in a day. Look at the windows, the back door and the corner above the cooker.

Then look at the fireplaces. An open flue is a slow, steady ventilation route, and many houses have lost theirs to boarding, a gas fire or a sealed register plate. That may have been the right decision for warmth, but the house now has one fewer way of breathing. If a fireplace has been blocked, I would ask whoever did it whether a small, discreet vent was left, and I would not change it without asking the council.

8.00: the room nobody heats

The last stop is the spare room that is shut up to save money. Moist air drifts through a house towards the coldest place it can find, and a cold, closed room is a good candidate. Damp on its walls or a smell in its cupboards is often made somewhere else in the house.

The answer I would try first is modest: a little background warmth and the door left ajar. That is judgement, not a rule.

What the morning usually adds up to

This table is my own reading, not an official one. It is a starting point for a conversation with whoever advises you.

The second row is the one that matters most. York's guidance warns that "Changes to windows can impact on condensation and damp throughout the building", and that where new windows improve thermal efficiency and reduce airflow in damp buildings, "condensation can be transferred to other parts of the building, potentially hidden within walls, and this can lead to rapid decay of historic fabric." When I wrote about draughty windows before winter, sealing the gaps was one of the steps. I still think that is right, and York's note says draught proofing "does not usually require permission". But a house that has been made tighter needs its water to leave some other way, and that is worth planning rather than discovering.

The roof space deserves the same morning look. If you have recently insulated the loft or the rafters, go up on a cold day and check the underside of the roof and the timbers for damp.

Fans, vents and where consent comes in

The obvious fix for a damp bathroom is a fan, and in a listed house that is a change to the building. Bath and North East Somerset Council's page on mechanical ventilation with heat recovery states that listed building consent is required to install an extractor fan or a heat-recovery ventilation system. The same page gives the reason ventilation matters at all: "Excessive moisture levels can lead to condensation and mould and bacterial growth, which can be harmful to historic building fabric and human health, so controlled ventilation is recommended." It also makes a point I find useful when owners worry about draughts: "In draughty homes they are less beneficial because the uncontrolled air provides enough vent."

That is one council's published position, and York is a second council's view on windows. Neither is a national rule. Ask your own council.

The law itself turns on effect. Section 7 of the 1990 Act requires authorisation for works to a listed building "in any manner which would affect its character as a building of special architectural or historic interest" (section 7 of the 1990 Act). GOV.UK's planning practice guidance says the listing normally covers the whole building, "internal and external", and that where there is any doubt, it would "encourage owners and developers to discuss the matter with the local planning authority before submitting any application".

Signs it is time to call someone

Most morning condensation is housekeeping. I would bring someone in when:

• water appears on walls or ceilings rather than on glass
• the smell or the spotting is still there after a fortnight of airing and moving furniture
• decorative plaster, panelling or painted joinery is staining or softening
• you are thinking about new windows, new glazing, fans or vents, because each of those changes how the whole house handles moisture

That last point is where an architect who knows old buildings can help most: looking at the house as one system before any single part of it is changed.

A quieter kind of warmth

An old house was built to share its air with the people in it. Most winters, it needs only a little help, a cloth on the sill and a window opened at the right moment, to carry on doing so.

Speak to Giles if your windows have started to stream and you would like a second pair of eyes: book a conversation, get in touch, call +44 (0)7737 745211, or send a WhatsApp voice note.

Giles Paul Shorter — ARB registered · RIBA Chartered Member · on the RIBA Conservation Register · 17+ years specialising in listed and historic buildings.