The 7.45 pm Curtain Trick: Save Energy with Thermal Curtains

With the arrival of spring, many people turn their heating down slightly but continue using it. Yet a straightforward habit offers considerable savings potential: closing your curtains at the right time can keep warmth indoors and noticeably reduce your energy bills. It requires no high-tech equipment, just good timing and suitable fabrics.

The principle behind the curtain trick

The concept is remarkably straightforward. During daylight hours, the sun heats your home for free. Windows receiving direct sunlight in particular can act like a magnifying glass, allowing substantial energy to enter. Once darkness falls, however, the process reverses and heat escapes outdoors through the same glass.

“Closing the curtains at dusk creates an extra thermal layer in front of the window – like thin, flexible insulation.”

In many areas, this point comes at around 7.45 pm in March. That is when outdoor temperatures become noticeably cooler, even though the warmth accumulated during the day could still be used effectively indoors. If curtains and blinds remain open, much of that energy is lost and the heating system has to make up the difference.

Why spring is particularly important

Days become longer in March, the sun sits higher in the sky and its warming effect is stronger. Homes facing south or west benefit especially. However, the heating season is not yet over: nights remain cool and living spaces can lose heat quickly.

By deliberately “trapping” the day’s warmth, it is often possible to reduce the heating by one or two settings. The difference is greater in poorly insulated older properties than in modern homes, but even well-insulated flats can benefit over the course of weeks and months.

How much money curtains can really save

The precise saving depends on several factors, including window quality, insulation standards, the heating system and energy prices. Even so, energy advisers consistently report that deliberately closing curtains and blinds can substantially reduce heat loss through windows.

• Windows are often the weakest point in a building’s thermal envelope.
• Glass transfers cold and heat more quickly than an insulated wall.
• The larger the glazed area, the more energy is lost without protection.

If improved heat retention allows you to lower your heating by only one degree in the evening, average heating energy demand falls by around six per cent. Across a year, a typical household can quickly save sums ranging from the mid double figures to the low triple figures in pounds, simply by changing its evening routine.

Thermal curtains: what they can and cannot do

Ordinary decorative curtains can already make a difference if they cover the window area as fully as possible. The effect is much stronger with purpose-made thermal curtains, however. These usually feature thick, multi-layered construction or an insulating backing.

“Thermal curtains work like an additional soft insulating layer in front of the glass – keeping warm air in the room and blocking cold draughts.”

High-quality versions can cost around £100 per pair. This may initially seem like a significant investment, but it becomes more reasonable when their lifespan is considered: if they reduce heating use for several years, they can often repay their purchase price.

What to consider when buying thermal curtains

• Fabric thickness: The thicker the material, the better its insulating performance.
• Backing: Look for a thermal coating or a lining made from fleece, felt or a similar material.
• Length: Curtains should reach almost to the floor to stop cold air flowing underneath.
• Width: Aim for at least twice the width of the window so that no gaps remain.
• Fitting height: Install the curtain rail as close above the window as possible, preventing heat from escaping at the top.

How to use the 7.45 pm curtain trick every day

At its heart, this is about forming a habit. Once you are used to closing the curtains at a set time each evening, it soon becomes automatic. A few practical steps can help you get started:

• Check the time: When does it actually get dark in your area during March? A useful guide is roughly 7.30 pm to 8.00 pm.
• Set a reminder: Create a phone alarm for the first two weeks.
• Choose an order: Air the room briefly first, then close the windows and finally draw the curtains.
• Adjust the heating: After a few days, test whether the room temperature remains steady when you turn the heating down slightly.

After only a few evenings, you will often notice that the room stays comfortably warm for longer while temperatures outside fall considerably.

A summer bonus: a heat shield instead of heat storage

Thermal curtains are not solely for winter. In summer, their purpose is reversed: briefly air the home through in the morning while outdoor air is still cool, then close the windows and draw the curtains or blinds during the day. This limits the heat entering the home, keeping rooms more comfortable for longer.

This can noticeably reduce peak temperatures, particularly in top-floor flats and rooms with extensive glazing. Anyone who immediately turns to a portable air conditioner on hot days can often reduce its use through careful curtain management, which in turn saves electricity.

Curtains are only one part of the solution – these combinations achieve more

The curtain trick works best alongside other simple measures. Here are some examples:

Measure	Winter benefit	Summer benefit
Close external shutters at night	Further reduces heat loss alongside curtains	Blocks direct sunshine
Apply sealing strips to window frames	Less draught, more even indoor conditions	Protects against flows of warm air from outside
Place a rug on cold floors	Keeps feet warm and subjectively reduces heating needs	Makes walking barefoot more comfortable and reduces the perception of temperature

Each measure delivers only part of the overall effect on its own, but together they can create a clearly noticeable improvement in comfort while reducing energy costs.

Common mistakes that undermine the savings

Some habits reduce the effectiveness of thermal curtains. These include:

• Hiding radiators behind fully closed curtains, as the heat then circulates poorly around the room.
• Arranging curtains decoratively at the sides, leaving large sections of glass exposed.
• Leaving windows on the tilt setting while drawing the curtains, allowing warm air to flow straight outside.
• Choosing short curtains that reach only to the windowsill.

Ideally, the curtain should finish just in front of the radiator or be fitted so that warm air can still flow into the room. In rented homes with awkwardly positioned heating, special rails or brackets can sometimes guide the fabric slightly away from the radiator.

Why this simple trick is especially appealing now

Many households are still feeling the impact of higher energy prices. Major improvements, such as replacement windows or external wall insulation, cost a great deal and cannot be carried out overnight. Using curtains more consciously may seem almost too simple by comparison, yet it has an immediate effect, takes very little effort and can be done in any home, whether rented or owner-occupied.

Once people understand the principle, they often start viewing their windows differently: what should I do in the morning and what should I do in the evening? When should I let in light and warmth, and when should I block them out? Thermal curtains and fixed times such as 7.45 pm are merely tools; the real difference lies in the daily routine.