Why Closing Roller Shutters at 6 pm in March Can Raise Heating Costs

But in March, this reflex can cost you real money.

More and more households across Europe are adjusting how they heat their homes according to the time of day – and to electricity and gas prices. One seemingly harmless habit is now under scrutiny: lowering roller shutters as early as 6 pm. What was once considered sound advice for keeping warm can actually become a problem in March. Closing them too soon may block free solar heat and, without you noticing, push up heating bills.

Why the 6 pm roller-shutter rule can backfire in March

In the depths of winter, closing roller shutters early appears perfectly sensible. Darkness falls quickly, outdoor temperatures drop sharply, and every barrier between the home and the cold outside helps. Many people have turned this into a fixed routine: “6 pm, shutters down.”

That routine is no longer well suited to March. Days are longer, the sun is higher in the sky, and it can still provide a noticeable amount of warmth from the afternoon onwards – particularly on south- or west-facing façades. Anyone who automatically darkens every room at 6 pm cuts off a free source of heating.

Anyone who closes their roller shutters too early in March often gives up several hours of free solar warmth and risks higher heating costs.

There is also a psychological element. When a home becomes dark early, people are more likely to switch on lights, feel that they have entered “evening mode” sooner and turn up the thermostat more generously. The supposed money-saving step can therefore have the opposite effect.

How much heat is really lost through windows?

Windows remain a weak point in a building’s thermal envelope. In poorly insulated homes, around 10 to 15 per cent of heating energy escapes through them; in individual cases involving numerous old windows, the figure can reach as much as a quarter of all heat losses. Authorities such as the French environment agency ADEME note that closed roller shutters can significantly reduce heat loss through the glazed area – by up to around 60 per cent across the window surface.

The explanation is straightforward: an insulating layer of air forms between the glass and the roller shutter. It acts like an extra layer of insulation. The window surface feels less cold, draughts are reduced and room temperatures seem more even. As a result, some households can manage with the thermostat set half a degree to one degree lower.

For someone spending around €1,200 on heating each year, using roller shutters consistently can save roughly €40 to €80, depending on the condition of the property. The savings may be greater still in seriously outdated buildings with single glazing and effective roller shutters.

Why open roller shutters are not “forbidden” in March

Many advice guides include recommendations such as: “Close roller shutters as soon as it gets dark.” In midwinter, that is broadly accurate – in many areas, outdoor temperatures are already well below the indoor comfort level by late afternoon.

By March, however, the situation changes. The sun has considerably more strength, the air cools down more gradually in the evening, and south- and west-facing windows in particular can still deliver measurable warmth into the early evening. This is why the old 6 pm habit can feel like an unwritten rule: anyone who follows it rigidly stops their home from continuing to warm up for free.

A flexible approach makes far more sense: close roller shutters when the temperature outside is clearly lower than the desired indoor temperature and direct sunlight is no longer hitting the windows – not simply “because it is 6 pm”.

Typical March scenarios

• Early March, cold northern area: The sun is low, dusk comes early and temperatures are often in single figures. In older, north-facing homes, closing the shutters at 5.30 or 6 pm can be worthwhile.
• Mid-March, mild area, south-facing façade: The sun may warm the living room until 6.30 or 7 pm. Closing everything at 6 pm effectively switches off the free heating source at the window.
• Late March after the clocks go forward: Daylight lasts noticeably longer and evening sun may be possible after 7 pm. A fixed time is then hardly appropriate.

How to find the ideal time to close your roller shutters

The most dependable rule is to watch the thermometer and the position of the sun rather than the clock. Ask yourself two questions:

• Is the outdoor temperature clearly below the temperature you want indoors – for example, 12°C outside and 19°C inside?
• Is direct sunlight still falling on the window, or has it gone?

Only when the answer is “clearly colder outside, with no more sun” does closing the shutters offer its greatest benefit. At that point, the insulating air layer helps retain warmth in the room without requiring you to turn up the thermostat.

For every degree the thermostat is lowered, heating energy demand falls by roughly 7 to 8 per cent. Anyone who saves only half a degree through smart roller-shutter management will already notice it on their bill.

The direction the windows face is another important consideration:

• North- and east-facing windows: These usually receive little direct sunshine in March. A relatively fixed period between 5.30 and 6 pm can make sense here, especially in older buildings.
• South- and west-facing windows: These sides benefit most from afternoon and evening sunlight. It is better to wait until the sun has disappeared completely – often between 6.30 and 7 pm.

Modern roller-shutter technology can do some of the work for you

People who operate roller shutters manually can easily stick to old routines. Motorised shutters and smart controls offer more flexibility. Many systems can be programmed to close earlier in the depths of winter and progressively later in March, adapted to the direction the room faces and its purpose.

One possible schedule is:

Month	North/east side	South/west side
January	approx. 5 pm	approx. 5.30 pm
February	approx. 5.30 pm	approx. 6 pm
March	approx. 6 pm	6.30–7 pm (depending on sunshine)

These time windows do not replace looking outside, but they provide a useful starting point, particularly when no one wants to adjust the shutters manually every evening.

How roller-shutter timing affects your wellbeing

Amid all the debate about heating costs, it is easy to overlook that daylight is an important influence on mood and sleep patterns. In March, many people enjoy the fact that evenings stay lighter for longer. Anyone who consistently darkens their home at 6 pm deprives themselves of this small taste of spring.

Studies indicate that extended brightness in the early evening can help to stabilise the body clock. People feel more active, get through the evening more easily, and feelings of being cooped up also diminish – something that was particularly relevant when working from home. Closing roller shutters later therefore makes use not only of solar heat, but also of additional natural light.

Practical everyday examples

• Living room with a large west-facing glazed frontage: Wait to close the roller shutters until direct sunlight no longer enters the room and it is clearly colder outside. Before then, let the sun contribute to heating the space.
• North-facing bedroom: Here, light matters less than peace, privacy and warmth. On cold days, 6 pm can be suitable, particularly in older homes.
• Children’s bedroom: Light and sleep are closely connected here. Time the roller shutters so that some evening brightness still filters through the curtains, while the room does not become cold.

When closing roller shutters early still makes sense

Despite the drawbacks of a rigid 6 pm rule, closing shutters early remains the best option in some situations: in older properties with draughty windows, in ground-floor flats exposed to views from outside, or on particularly windy days. Anyone who regularly finds themselves sitting beside a window feeling cold should lower the shutters too early rather than too late.

Over the long term, it is worth considering the technical side as well. Well-sealed windows, adjustable ventilation, properly fitted seals and suitable roller shutters all work together. The better the thermal envelope, the more flexible you can be about timing – and the more the March sun can provide its advantages.

Ultimately, there is no rigid prohibition and no magic time. People who pay attention to their thermometer, the sky and their own sense of warmth will usually make a better decision than anyone following a fixed 6 pm reflex.