Awnings, fans and air conditioners: do you know how to combine them?

Awnings to prevent heating

An awning is a piece of fabric that covers part of a building to provide shade and stop heat from building up on the surface. Generally speaking, awnings are installed over windows or on terraces to stop the sun from heating up the floor or the ground in our homes. They are most effective when they cover as much of the building's façade as possible. Awnings don't cool the building, but they do prevent it from getting hot, so they are just as important.

Awnings have been calculated to reduce the temperature of façades by up to 6 ºC, by preventing walls from becoming a high-thermal mass element. Building façades are heated up by direct sunlight and indirect solar radiation from the atmosphere (and even the reflected radiation from asphalt).

Awnings are most effective if they provide around 10 to 14 hours of shade, particularly at night.

Fans to keep the air moving

Have you ever wondered why blowing on soup makes it cool down? It is precisely the same physical mechanism by which you feel colder when the wind blows on a cold day: the speed of the cold air around a warmer object cools it quickly. A fan moves the air around you and cools your body temperature.

When are the effects of a fan most noticeable? When the air around you is cooler than you because of the draught it creates that flows around us. Fans work best when you wear light clothing or have more skin exposed, by increasing a factor called total heat transfer coefficient (U). If you have ever sat outside a bar or café and been sprayed by mist, you will have noticed that the liquid on your skin increases this effect noticeably.

Air conditioning, the last resort against the heat

Air conditioning units utilise a heat pump mechanism to transfer energy from one location to another, a process known as aerothermics which you may be familiar with. There are various mechanisms for delivering aerothermal energy (air through split systems, air through ducts, radiant radiator, radiant floor heating...), but they all work the same way, like a short of heat conveyor belt. In summertime, the conveyor belt takes the heat outside.

Air conditioning, both through air pumping or radiative elements, despite its efficiency exceeding 300%, tends to consume a significant amount of energy. In 2022, the OCU (Spanish Organisation of Consumers and Users) calculated that one hour of air conditioning costs around 0.3 euros, but this cost increases under the following circumstances:

• If the target temperature you aim for inside the home is very low.
• When you increase the volume of air to cool, such as leaving doors open, for example.
• When the temperature outside is high, because it reduces the efficiency of the equipment.

How should I combine air conditioning, fans and awnings?

Awnings are relatively expensive to install, but they do not consume any energy. A ceiling fan is cheap to install, and it consumes very little energy (barely 40W) to work. Air conditioning is more expensive to install, and although maintenance of an air conditioning unit consists of cleaning filters and filling with gas, starting it up makes it the most expensive of all. How can this equipment be combined for maximum comfort and the lowest possible cost?

1. On hot days, before the sun starts shining on windows and façades, roll out the awning. It is important to do this ahead of time, because the awning does not cool the building, it prevents it from getting hot. Sometimes using an awning in time will be enough to avoid having to use the air conditioning a few hours later.
2. Without rolling in the awnings while the sun is still out and before you turn on the air conditioning, if you feel hot you can turn on the fan. However, only use it if you are going to be right under it or next to it. Most fans have speed settings. The higher the speed, the more heat you will lose through your skin. To get the most from your fan, dress appropriately for the heat: light clothing that allows air to flow, short sleeves, open-toe shoes, etc.
3. Without rolling in the awnings while the sun is still out and without switching off or lowering the speed of the fan, if you are still hot, you can switch on the air conditioner. First at a higher temperature, so that you can gradually lower it until you reach a comfortable temperature. When the fan is on, air conditioners can be set as high as 30 °C to achieve a pleasant temperature.

People often switch off the fan when they turn on the air conditioner. That's a mistake because together they are far more efficient than they are on their own. For example, the air conditioner with a fan may have to be set at 23 °C, but if you move the air about with the fan you can set it at 27 °C for the same effect.

Everything indicates that summers will be considerably warmer in the coming years. If you want to save energy, resources or money in the long term, it is advisable to invest now in low consumption solutions such as fans or zero consumption equipment like awnings to increase the effectiveness of other devices like air conditioners.