Temperature, humidity and why a room feels wrong

There is a settled way of talking about thermal comfort. It is worth asking how much of it survives contact with the detail.

Air temperature is not comfort

Comfort depends on air temperature, the radiant temperature of surrounding surfaces, humidity, air movement, clothing and activity. A room at twenty degrees with cold walls and a draught feels considerably colder than the number suggests.

This is why turning the thermostat up frequently fails to fix the feeling. A thermostat also reports the temperature at one point on one wall, which is frequently the warmest spot in the room and almost never where anybody actually sits.

Cold surfaces pull heat from you

A poorly insulated wall or a large single-glazed window radiates heat away from a body facing it. The effect is why sitting beside a window feels cold even in a warm room.

Insulation, secondary glazing and heavy curtains address the cause rather than the symptom. The same physics runs in reverse in summer, when a wall that has absorbed sun all afternoon goes on radiating heat into the room for hours after sunset.

Humidity cuts both ways

High humidity in warm conditions prevents evaporative cooling and makes heat feel worse. Very low humidity in winter, common with some heating systems, causes dry eyes, throat irritation and static. A cheap hygrometer costs very little and turns a vague complaint into a number.

On an ordinary week, drying laundry indoors is the largest single moisture source in most homes, which is why the damp complaint and the airer in the hallway tend to turn up together.

Draughts are the common culprit

Air movement over skin increases heat loss, so a small draught produces discomfort at otherwise adequate temperatures. Letterboxes, keyholes, floorboards, loft hatches and unsealed skirting are the usual sources.

Put simply, draught-proofing is among the cheapest and most effective home comfort improvements available. The distinction that matters is between a draught and deliberate ventilation, because sealing every air path in a home with fuel-burning appliances or no extraction creates problems considerably worse than the cold.

Damp and mould

Persistent high humidity produces condensation and mould, which is a health matter rather than an aesthetic one. Ventilation, heating and insulation together address it; any one alone usually does not. Mould affecting a substantial area, or anyone in the home with respiratory problems, warrants proper investigation rather than cleaning.

Put simply, in rented homes, damp caused by the building rather than by how it is used is the landlord's responsibility in many jurisdictions, and reporting it in writing is what starts that clock.

None of this is a substitute for talking to a clinician if something feels wrong.

Heating the person rather than the room

A heated throw, warm layers, a hot water bottle and a chair out of the draught raise comfort for a fraction of the energy needed to lift the temperature of a whole room. It works because most of the discomfort is heat leaving the body, and that can be slowed at the body rather than at the air. It is a supplement and not a substitute where cold is severe, because sustained low indoor temperatures carry real risks for older people, infants and anyone with heart or lung conditions.

Where a home cannot be kept warm enough, many countries run assistance schemes and local health or housing services can point to them, which is more use than quietly enduring it.

The takeaway

Find the draught and look at the walls before you turn the thermostat up.

Small and repeatable beats ambitious and abandoned, almost every time.