(Republished: as Luxembourg braces for a heatwave this weekend and MeteoLux has issued an orange alert for the entire country, the advice of Sarah Juchems, Head of the Operational Consulting and Implementation Department at Klima-Agence, is more relevant than ever. A look back at the most effective ways to keep your home cool.)
Temperatures could reach between 33°C and 35°C across the country. In a statement published on 18 June, Luxembourg’s Labour and Mines Inspectorate (ITM) urged people to remain vigilant and highlighted the importance of staying regularly hydrated, wearing light clothing and limiting strenuous physical activity during the hottest hours of the day. It also recommended keeping indoor spaces as cool as possible through the use of shutters, blinds and other forms of solar protection, advice that echoes the recommendations issued by Klima-Agence.
The ITM is also calling on employers to take measures to protect their staff, notably by ensuring access to drinking water, shaded or ventilated areas, and by limiting the most physically demanding tasks during the hottest parts of the day.
With heatwaves becoming more frequent, it’s tempting to switch on a fan or air conditioning as soon as the temperature rises. However, there are several simple steps you can take to keep your home cooler without driving up your energy bill.
Estimates of the Klima-Agence
According to estimates by the Klima-Agence, a pedestal fan used for four hours a day over a four-month period costs around €14 in electricity over the summer. A portable air conditioner used for eight hours a day over the same period can cost around €224, whilst a fixed system connected to a heat pump costs around €112.
To minimise the use of such equipment, Sarah Juchems, Head of the Advisory and Operational Implementation Department at Klima-Agence, shares the most effective tips for getting through periods of extreme heat whilst keeping energy consumption under control.
1. Prevent heat from entering
According to the expert, the most effective way to keep a home cool is to take action before it even starts to heat up. “Once the heat is inside the building, it’s difficult to get it out,” she explains.
The first thing to do is, therefore, to close the shutters, blinds or sunshades before the sun starts beating down directly on the windows. Ideally, you should plan ahead based on your home’s aspect: the sun rises in the east before moving south and then west, which means you need to adjust your sunshades as the day progresses.
Adjustable blinds allow some natural light to enter whilst significantly reducing solar radiation. Curtains can also help, although they are less effective than external shading. “The heat gets trapped a bit between the curtains and the window,” explains Sarah Juchems.
Vegetation can also help to limit overheating. A tree, a climbing plant or vegetation planted in front of an exposed façade absorbs some of the solar radiation before it reaches the glazing. Indoor plants, on the other hand, have very little effect on the room temperature.
For those with motorised shutters, there are also automation systems that can close the sun blinds depending on the amount of sunlight, or remotely via an app.
For those working from home, keeping the shutters closed all day can seem difficult. Sarah Juchems therefore recommends adapting your workspace rather than exposing the whole house to the sun. “You can move to a room that isn’t yet exposed to the sun,” she explains. A west-facing room, for example, will stay cooler in the morning, whilst an east-facing room will be more pleasant at the end of the day. When the sun reaches the room you’re in, it’s best to close the blinds and, if possible, move to another cooler room.
She admits that this solution isn’t always ideal, but it helps to prevent the room from overheating without having to switch on the air conditioning straight away.
2. Air it out at the right time
When it’s cooler outside than inside, you should make the most of it. “You should air the room out, especially in the morning, evening and at night,” advises the expert.
The aim is to create a proper draught by opening several windows or French windows at the same time to let out the heat that has built up during the day. Conversely, leaving a window slightly ajar in the tilted position for several hours is often counterproductive. “That doesn’t really allow for any air exchange,” she points out.
During hot spells, it is therefore best to open the windows wide during the coolest hours of the day, then close them completely when the temperature rises again.
This recommendation also applies to homes fitted with mechanical ventilation. When the outside temperature reaches 30 degrees, the system also draws warm air into the home. The Klima-Agence therefore advises reducing or temporarily switching off the ventilation during the hottest hours of the day and switching it back on at night. Some systems even have a ‘bypass’ mode that prevents the incoming air from being heated further.
3. Limit sources of heat indoors
Even with the shutters closed, certain everyday habits can cause the temperature inside to rise. The oven is one of the main culprits. “You should avoid using the oven when it’s very hot,” advises Sarah Juchems. Hobs, televisions and other household appliances also give off heat when they’re in use.
Lighting also plays a part. Modern LED bulbs generate very little heat, unlike older bulbs, which produced both light and heat.
This trapped heat is a particular problem in newer, well-insulated homes. Whilst insulation effectively prevents heat from entering, it also traps the heat that has built up inside. “Once the heat is inside the house, it doesn’t escape very easily,” the expert points out.
Conversely, older houses with thick walls are not necessarily cooler. These walls simply slow down the build-up of heat. After several days or weeks of high temperatures, they too eventually end up trapping the heat.
4. Use fans and air conditioning wisely
When the heat becomes unbearable, a fan is usually the most economical option. Used for four hours a day over four months, it costs around €14 in electricity over the entire summer season. However, how it works is often misunderstood.
“Ventilation doesn’t lower the temperature; it just circulates the air,” explains Sarah Juchems. The feeling of coolness comes from the movement of air, which helps sweat to evaporate. For this reason, the Klima-Agence recommends using a fan before resorting to air conditioning.
When heating is required, it is best to use it only when rooms are occupied, rather than leaving it on all the time. The temperature difference between indoors and outdoors should also remain within reasonable limits.
“Normally, we’d say the room temperature should be three to four degrees lower,” says the expert. In other words, when it’s 28 to 30 degrees outside, there’s generally no point in setting the air conditioning to 18 degrees. This significantly increases electricity consumption without improving comfort by the same amount.
At night, it is advisable to cool the room before going to bed, then turn the air conditioner down or switch it off once the temperature becomes comfortable.
5. Reduce your water consumption as well
Heatwaves usually lead to an increase in water consumption. Watering plants, taking more frequent showers or filling swimming pools can quickly drive up water usage.
However, a few simple steps can help minimise this impact. When watering, it is best to do so early in the morning or in the evening to prevent evaporation. “If I water during the day, the water starts to evaporate because it’s hot outside,” points out Sarah Juchems.
The water used to rinse fruit or vegetables can also be collected in a container and then reused to water plants, rather than being drained straight down the drain.
The expert also recommends using the dishwasher rather than washing up by hand, which generally uses more water, and only running the washing machine when it is full, using eco programmes where possible.
When it comes to showering, flow restrictors help reduce water consumption without compromising on comfort, thanks to a mixture of water and air that maintains a sufficient sense of water pressure. Finally, when it comes to washing a car, car wash facilities are generally more water-efficient than washing it at home.
