The short answer
A home office warms up through the day from computers, screens and you, often in a small room with the door shut. Shading, ventilation and cutting equipment heat help, and quiet air conditioning suits rooms that still get too warm.
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Home offices are often small rooms: a box room, a spare bedroom or a corner of another room. You spend long, still hours in them with equipment running, and you often keep the door shut for calls. That combination makes a comfortable temperature harder to hold than in a room you only pass through.
Where the heat comes from
Almost all the electricity your equipment uses ends up as heat in the room, and you add heat too. Rough figures, which vary a lot by model and workload:
| Source | Heat given off, roughly |
|---|---|
| You, sitting at a desk | 100 W |
| Laptop | 15–60 W |
| Desktop computer, everyday use | 50–150 W |
| Powerful computer working hard | 300 W or more |
| Monitor | 15–50 W each |
| LED desk lamp | 5–10 W |
A desk with a computer, two screens and you at it can give off a few hundred watts, all day. In a small room with the door closed, that's enough to push the temperature up noticeably by the afternoon, before any sunshine is counted. A window facing south or west adds more. Why some rooms overheat covers the other causes.
Keeping heat down
- Shade the window. Close blinds on the sunny side before the sun reaches the glass. They cut glare on your screen too.
- Ventilate early. Open the window first thing, while the air outside is cooler, and close it once outside is warmer than in. Leave the door open when you're not on a call so warm air can escape.
- Cut equipment heat. Let screens and computers sleep when you step away, switch off anything you aren't using, and use LED lighting. Where a laptop does the job, it gives off far less heat than a powerful desktop.
- Move what doesn't need to be there. Equipment that runs all day but doesn't need to be beside you, such as a second computer, can often go in another room.
- Use a fan. A desk fan helps you feel cooler, although it doesn't lower the room temperature.
Choosing cooling for a home office
Noise matters in a room where you take calls, and so does where the air goes.
A fan on a low speed is usually quiet, but it only cools you, not the room. A portable air conditioner does cool the room, but its compressor runs in the room with you, so it's usually louder, which you may notice on calls. It also needs a hose through a window.
With a wall-mounted split system, the compressor is in the outdoor unit. Quiet indoor units are often around 19–26 dB(A) on their lowest fan speed, and many systems have a quiet mode that holds the fan at low speed. The guide to how loud air conditioning is compares the figures.
Placement makes a difference over a long working day. A good installer will position the indoor unit so the airflow doesn't blow straight at your desk or chair, and will size the system for the heat your equipment gives off as well as for the room itself.
Heating the office in winter
Most wall-mounted split systems are heat pumps, so the same unit that cools the office in summer can heat it in winter. That lets you warm the one room you're working in during the day without heating the whole house. In heating mode, angling the louvres downwards helps, because warm air rises. Using air conditioning to heat in winter has more on getting this right.
Garden offices
Garden offices are often timber buildings with a lot of glass and little heavy material, so they heat up quickly in sunshine and lose heat quickly in cold weather. Shading the glass and ventilating at the right times matter even more than in the house.
Air conditioning can suit a garden office well, with the outdoor unit close to the building so the pipe run is short. It needs a suitable electricity supply. In England and Wales a new circuit is notifiable under Part P of the Building Regulations, so it's done by an electrician registered with a competent person scheme or notified to building control.
Related guides
- Why some rooms overheatA room overheats when heat gets in or builds up faster than it can escape. The usual causes are sunshine through large or west-facing windows, a roof directly above, heat from people and equipment, and too little ventilation.
- How loud is air conditioning?Quiet indoor units are often around 19–26 dB(A) on their lowest fan speed and louder at higher speeds, while outdoor units are typically 45–50 dB(A) at 1 metre. How loud it seems also depends on where the units are and how hard they're working.
- Which rooms benefit mostBedrooms usually benefit most, because heat makes sleeping hard, followed by top-floor and loft rooms, home offices and sunny living spaces. The best candidates are rooms you use a lot that regularly overheat, rather than every room in the house.
- Using air conditioning to heat in winterChoose heat mode, point the airflow down and give the room time to warm. Most systems keep heating well below freezing, though less efficiently, and pause now and then to defrost the outdoor unit, which is normal.