Why Does My Wall Feel Hot or Cold? A Delhi Guide

Free checks: which wall, which direction, what time

These cost nothing and take a few minutes. They separate an ordinary hot wall from one worth worrying about.

• 1. Work out which way the wall faces. Use the compass on your phone. West and south-west walls take the worst of the afternoon sun in Delhi. South walls take a long steady load. North walls barely warm at all. If your hot wall is the north one, sun is not the explanation.
• 2. Note the time of day it is hottest. A sun-loaded wall peaks in the late afternoon and stays warm into the night, then cools by morning. A wall that is warm at seven in the morning, before the sun has reached it, is being heated by something else.
• 3. Compare it with the wall next to it. Put a hand on two walls in the same room, then on an internal partition. Big difference between an outside wall and an internal one is normal. Big difference between one part of a wall and the rest of the same wall is not.
• 4. Find out what is behind it. Walk round. A kitchen hob, a fridge pushed into a recess, an inverter or battery, a geyser, a chimney duct, a lift shaft, or a neighbour’s kitchen. Each of these heats the wall from the other side.
• 5. Check whether it is the whole wall or one small area. A warm wall is usually a physics problem. A warm patch the size of a hand, especially near a switchboard, socket or light point, is not, and the next sections cover that.
• 6. Check the ceiling too, if you are on the top floor. A ceiling that is warm at night means the roof slab is holding heat, and that changes what is worth doing about it.

Which wall is hottest in a Delhi summer, and why

This is the ordinary explanation and it fits most cases. A wall is a heat store. It absorbs through the day and releases through the evening, and how badly it does that depends on orientation, what is above it, and how it was built.

• West and south-west walls are the worst. They take the afternoon sun when the air is already at its hottest, and the low late-day angle means the sun strikes them almost square on. That is why a west bedroom is uncomfortable at ten at night while an east one is fine.
• South walls take a longer, steadier load across the middle of the day. East walls heat in the morning and then have all afternoon to cool. North walls stay closest to shade temperature.
• Top-floor and terrace-adjacent walls carry the roof load too. An exposed slab bakes all day and radiates downward into the flat all evening. This is why top-floor flats in Delhi run several degrees warmer than the same flat two floors down. Living on the top floor in Delhi covers this in full.
• Single-brick walls with no cavity heat through fastest. Many Delhi flats, balcony enclosures, servant rooms and later additions are built in a single brick thickness with no gap and little insulation. There is simply less mass and no air gap to slow the heat, so the inside face follows the outside face within hours.
• Dark exterior paint and bare concrete make it worse. A dark or heavily weathered exterior surface absorbs more than a light one. Anything that shades the wall — a chajja, a balcony above, a tree, or an external blind — makes a real difference, because stopping the sun before it reaches the wall beats trying to cool the wall afterwards.
• Is it DIY? Partly. Curtains, blinds and keeping windows shut during the day help. Reflective or heat-reflective exterior coatings, terrace treatment and insulation are contractor jobs. Summer heat and cooling tips covers the free and cheap side first.

A wall shared with a kitchen or a boxed-in appliance

If the wall is warm at times that have nothing to do with the sun — while cooking, or overnight, or on a cloudy day — the heat is coming from inside the building.

• A wall shared with a kitchen. A hob running for an hour, an oven, or a wall behind a cooking range warms the plaster from the other side. It rises and falls with meal times, which is the giveaway. The same applies to a wall shared with a neighbour’s kitchen in a flat.
• A fridge pushed into a tight recess. A fridge moves heat out of its own inside and dumps it into the room through the coils at the back and sides. Boxed into a snug alcove with no clearance, it heats the wall behind it and also works harder and runs longer, which makes the wall warmer still. Leaving a proper gap at the back and sides fixes both.
• An inverter and battery. Common in Delhi and often tucked into a cupboard or a corner. Batteries get warm on charge, and an enclosed space traps that heat against the wall. They need ventilation for their own sake as well as the wall’s.
• A geyser, a chimney duct or a hot water line. A storage geyser mounted on a wall, or a duct carrying kitchen exhaust, will warm the surface around it. So will a hot water line buried in a wall while it is running.
• A lift shaft, machine room or common riser on the other side of the wall, in a flat that backs onto one.
• Is it DIY? Mostly yes, and it is mostly about clearance and ventilation: pull appliances off the wall, open up enclosed cupboards, and do not box in anything that gives off heat.

When a warm wall or switch plate is an electrical warning

This is the section to act on rather than read. A switch plate, socket, switchboard or small area of wall that is warm for no obvious reason near electrics is not normal, and it is not something to monitor for a few weeks. Heat at an electrical point usually means a loose connection or a circuit carrying more than it should, and both get worse rather than better.

• Switch off that circuit at the MCB and stop using it. Unplug what is connected to it. Then call a licensed electrician the same day.
• Treat these as urgent alongside warmth: a burning or fishy plastic smell, browning or scorch marks around a socket, a buzzing or crackling sound, a plug that is hot to remove, flickering lights on that circuit, or an MCB that trips repeatedly.
• Do not open the switchboard, tighten anything or investigate inside it yourself. Live circuits are not a DIY area, whatever the video says. This is a job for a qualified electrician, full stop.
• Heavy-load points deserve extra attention. AC points, geyser points, and sockets running an inverter, a microwave or a heater are where undersized wiring and tired connections show up first. Old aluminium wiring and long-serving switchboards in older Delhi flats are common causes.
• Extension boards are a frequent culprit. A warm extension board or a daisy chain of boards behind furniture is a genuine fire risk. See extension boards and plug safety.

Switchboard and socket replacement covers what that repair involves, and home electrical safety tips covers the warning signs worth knowing before they turn into this.

A cold patch in winter, and when to call someone

A cold wall in a Delhi January is normal. A cold patch on an otherwise ordinary wall is worth paying attention to, because it is often the first sign of a damp problem that has not produced visible water yet.

• Why cold patches matter. Damp plaster conducts heat away faster than dry plaster, so a wet area feels noticeably colder than the wall around it before it looks any different. If one patch is cold and the rest of the wall is not, suspect moisture rather than temperature.
• Cold surfaces collect condensation. The coldest surface in a room is where moisture from bathing, cooking and drying clothes indoors settles first. That is why outside corners, walls behind an almirah and window reveals go damp and then grow black speckling while the rest of the room is fine.
• How to check it for free. Feel along the wall on a winter morning and mark where the cold area starts and stops. Then tape a sheet of clear plastic tightly over it for a day: droplets on the room side mean condensation, droplets on the wall side mean water coming through. How to find the cause of a damp wall walks through the rest.
• What helps immediately. Move furniture a few inches off cold outside walls so air can circulate, run the bathroom exhaust a few minutes longer, and ventilate after cooking even in smog season. If black growth has started, read black mould on walls.

When to call someone, and who:

• An electrician, the same day, for any warmth at a switch plate, socket or board, or any burning smell, scorching or buzzing.
• A waterproofing contractor if a cold patch turns damp, if the ceiling stains on a top floor, or if it comes back every monsoon. Start with terrace waterproofing if you are on the top floor.
• A painting or waterproofing contractor for exterior heat-reflective treatment on a west or south wall, or for terrace treatment — and get it done in the dry season, per the best time to paint and waterproof.

Tell them which way the wall faces, which floor you are on, what is on the other side, what time of day it is warmest or coldest, and whether it is the whole wall or one patch. Those five answers save an hour of poking about.