Cooling an open-plan living space

Open-plan living is the layout most modern homes are built or remodelled into, and it is the layout that cooling advice serves worst. Nearly every technique on this site assumes you can close a door.

The standard approach to a hot house is to give up on cooling all of it and win one room. That works because a closed door is a boundary the heat has to cross.

An open plan removes that boundary by design. Whatever you put in it conditions the whole connected volume — which usually includes the kitchen, often a dining area, frequently a stairwell, and sometimes a double-height void.

Three consequences that shape every decision below:

• Your load is larger than the room you are standing in. The volume that has to be conditioned is everything air can reach without opening a door.
• A single point source produces a gradient. One powerful unit at one end makes that end cold and leaves the other end unchanged, because air does not distribute itself usefully across a large space.
• Air movement is not optional here. In a closed room a fan is a comfort upgrade. In an open plan it is the distribution system.

Across the certified ceiling fan field, blade span and efficiency are strongly related — and not in the direction most people assume.

A large fan turning slowly moves more air for less power than a small fan turning fast, because airflow scales with swept area while drag scales sharply with tip speed. In a room that needs air distributed rather than blasted, that is exactly the right trade.

Note the last two rows, though: span raises the floor, design sets the ceiling. The best 60-inch fan at 483.0 CFM per watt beats the best 84-inch fan at 422.2. Buy the largest span the room and the ceiling allow, then choose on certified efficiency within that band — ceiling fans compared in full.

Many open plans have a vaulted or double-height section, which looks wonderful and traps all your warm air at the top where nobody is.

Warm air rises and stays risen unless something moves it. In a double-height space the temperature difference between head height and the top of the void can be substantial, which means you are heating a volume you never occupy.

Two fixes, and they are not alternatives:

• A fan on a downrod, hung down into the occupied zone. A fan mounted at the apex of a vault is too far from people to do anything. It needs to be low enough to move air where bodies are — downrod sizing and fans for high ceilings.
• A route for the hottest air to leave. A high opening window, a roof vent or a whole-house fan gives the accumulated heat somewhere to go rather than merely stirring it — whether a whole-house fan suits your house.

This is the part that makes open-plan cooling genuinely different rather than merely larger.

An oven, a hob, a dishwasher on heated dry and a fridge all sit inside the space you are trying to cool, with no door between them and the sofa. In a traditional layout the kitchen door contains that; here nothing does.

Which makes extraction the highest-leverage appliance in the room. A range hood that actually vents outside removes cooking heat and moisture at source, before it becomes the living room’s problem — range hoods compared and cooling a kitchen.

A recirculating hood that filters and returns the air to the room does nothing whatsoever about heat. It removes grease and some smell, and every joule of cooking energy stays in your living space.

Open-plan spaces are usually built with large glazed elevations or bifold doors, and that glass is the single biggest heat input in the room.

External shading remains the highest-return intervention: an overhang, a pergola, an awning or a tree stops the energy before it reaches the glass. Internal blinds stop it after it has arrived, which is considerably less effective and considerably cheaper — shading and film compared.

Bifolds are worth a specific note. Opening them wide feels like ventilating, and on a hot afternoon it is the opposite — a very large opening to air hotter than your room. Open them in the evening, not at two o’clock.