Multilayer thermal curtains

Made by combining a decorative layer with an internal insulating layer, multilayer thermal curtains are the most common choice for domestic environments. In many cases, they also include a backing layer that protects against ultraviolet rays and direct heat from the sun.

For a multilayer curtain to transition from being merely decorative to an effective element for energy savings, it needs to have a density of 500 g/m² or higher. With this type of curtain, we can reduce the indoor temperature of our home by between 5 and 7 °C, thereby decreasing the electricity consumption of cooling systems.

Blackout thermal curtains

If, in addition to a high level of thermal insulation, you want to block out practically all incoming light from the outside, blackout thermal curtains incorporate an extra layer designed specifically for this effect.

Manufactured from special materials such as PVC or fibreglass, this layer keeps your living room, bedroom or workspace completely dark, providing greater privacy, comfort and even a reduction in street noise.

Thermal curtains for technical and industrial use

While it is less common to find them in residential properties, you have almost certainly seen this type of thermal curtain at the entrance of logistics warehouses, factories or other spaces that require stable indoor temperatures.

Their composition, generally consisting of thick, vertical PVC strips, prevents the entry of heat, excess light and even insects, animals or pollutants into the facility. They serve as an element of both security and energy efficiency that helps keep entire buildings and technical spaces protected.

How thermal curtains work

The effectiveness of thermal curtains relies entirely on the characteristics of the materials used to make them. These materials are carefully selected to reduce temperature transfer from the street into the home and vice versa. As a result, they optimise indoor comfort, leading to subsequent energy savings on heating and cooling.

The multiple layers that comprise them, typically ranging from 3 to as many as 7 in premium models, serve a specific purpose: trapping air within the curtain itself to minimise heat loss and prevent external heat from entering through the window glass.

In winter, they perform the exact same function: they retain the heat generated by your heating system and prevent it from escaping through the windows, while simultaneously acting as a barrier against incoming cold from outside.

When you consider that heating and air conditioning is one of the largest components of residential electricity consumption, and that nearly 13% of the energy used for it is lost through hot and cold air leaks – even with the windows closed – thermal curtains can reduce heating and cooling demand by 40% to 50% and lower the indoor temperature by 4 to 7 °C during the summer.

How much thermal curtains save

To obtain exact figures and determine how much you can save on your electricity bill by using thermal curtains, several factors must be considered: the type, orientation and location of the property, your current heating and cooling system, the quality of your windows and your daily habits.

Although the combination of these factors will alter the final result, the fact remains that installing thermal curtains helps save on heating and cooling, both in summer and in winter.

To give us an idea of the impact of properly insulating household windows, a study conducted by the Institute for Energy Diversification and Saving (IDAE) concluded that applying thermal insulation solutions to a three-storey building, with a floor area of 92 m² per unit, provides an annual overall energy saving of between 5.4% and 8%, depending on the geographical region.

According to the same source, the average annual electricity consumption of Spanish households stands at around 3,500 kWh. Consequently, if we apply the price of €0.128/kWh from Endesa's Light 24h Tariff to this study, the savings generated by high-quality insulation can come close to €40 per year.

Benefits of thermal curtains

Thermal curtains go beyond decoration, offering practical benefits that enhance comfort and energy efficiency thanks to their insulating properties. They also help reduce energy use and can even block outside noise:

Save on electricity and gas bills

• They reduce the need for heating and cooling systems and, therefore, electricity consumption, by minimising heat loss in winter and limiting heat gain in summer.
• They lower expenditure on electricity and gas bills, driving significant energy savings. This is particularly relevant for homes with high heating and cooling costs.
• According to technical estimates, they improve the thermal insulation coefficient by limiting the heat transfer rate (U-value).
• Since they are relatively affordable and require no construction work, the return on investment is much faster than with other insulation alternatives.

Thermal comfort and noise reduction

• They eliminate the 'cold wall' effect near uninsulated glass. This way, they contribute to a more stable and uniform indoor temperature while preventing sudden fluctuations, which enhances overall comfort.
• They also help reduce cold or hot draughts entering the home.
• Their dense fabrics and multiple layers help dampen noise coming from outside the home.

Design and decorative options

• This type of curtain comes in an extensive array of styles and designs, as well as a variety of textures and finishes, ranging from velvet to eco-friendly options made with organic cotton and linen.
• They are highly versatile when styling a property because they seamlessly combine aesthetics with functionality, fitting perfectly into living rooms, bedrooms and offices to blend easily with the decor of the space. 
• They also offer a wide price range, from just €15 for the simplest, most affordable models to over €100 for curtains featuring high technical complexity and premium fabrics.

Limitations of thermal curtains

It is important to keep in mind that thermal curtains are not an infallible solution, nor do they completely replace high-quality structural insulation within the property. For this reason, it is advisable to consider their main limitations before making your choice:

• Correct installation is essential for effectiveness. If the window is not fully covered or gaps remain, insulation will be incomplete.
• They do not serve as a solution for structural insulation issues within the home (such as air leaks through seals, old windows with poorly sealed frames, thermal bridges in walls, floors or ceilings, etc.). In these instances, thermal curtains act purely as a complement.
• Replacing windows and insulating walls, floors or ceilings will always be a more effective solution than relying on thermal curtains. Compared to these major upgrades, thermal curtains are less expensive but also offer more limited performance.

Thermal curtains versus other insulation solutions

To evaluate whether installing thermal curtains at home is the right choice, it is useful to compare them with some of the most common alternatives for window insulation, such as double glazing, draught excluders or roller blinds.

Thermal curtains vs. double glazing

Double glazing involves replacing windows as well as upgrading their frames, fittings and seals. It provides permanent insulation and significantly reduces heat loss or gain – much of which occurs through windows, doors, joints and seals.

For their part, thermal curtains act as a complement to these structural resources within the home. They offer additional insulation but cannot correct thermal bridges or defective windows. Therefore, while extremely useful, they do not achieve the same level of efficiency as properly insulated windows. However, their low cost and ease of installation work in their favour, making them highly attractive as an intermediate solution.

Thermal curtains vs. draught excluders

Draught excluders (sealants for joints, frames, windows or doors) are another simple measure to prevent air currents by sealing gaps and thereby reducing air infiltration. While it does not fully replace proper window or wall insulation, combining draught excluders with thermal curtains improves overall insulation performance.

Thermal curtains vs. roller blinds

Roller blinds are typically lighter and serve a different purpose, as they are focused on controlling light entry or enhancing household aesthetics rather than providing thermal insulation. Although some blinds do possess insulating properties, they generally retain heat or cold less effectively than a thermal curtain, as they feature fewer layers, less insulating material and a lower fabric density. If your objective is to ensure energy efficiency at home, thermal curtains are a much better alternative than standard roller blinds.

Overall, thermal curtains strike a perfect balance. They offer better performance than lightweight curtains or blinds while remaining far more cost-effective than structural renovations. Furthermore, they are fully compatible with draught excluders and other sealing improvements.

How to install thermal curtains correctly

1. For thermal curtains to perform correctly and provide their maximum insulating capacity, we should follow a few recommendations during installation:
2. Position or hang them as close as possible to the window frame – ideally touching the wall or moulding – to minimise gaps where air or heat can escape and to maximise their insulating effect.
3. Ensure that the curtains cover the entire glass surface, extend fully to the floor or windowsill, and overlap in the centre if they consist of two separate panels. This helps reduce draughts.
4. If possible, fit a pelmet or valance at the top of the window. This will limit air circulation behind the curtain.
5. Use them strategically to your advantage. In winter, keep them closed during the night to retain heat inside the home. In summer, close them during peak sunlight hours to reduce incoming heat and maintain a comfortable indoor temperature.
6. Install insulated curtains in high-priority areas such as rooms with single-pane glass, windows facing south, east or west, and balconies or large glass doors.
7. Maintain the curtains periodically by vacuuming them regularly to preserve the properties of the insulation and prevent dust accumulation.

Are thermal curtains worth it?

The answer to this question will depend on various factors, such as the type of property and windows, the climate of the region where the building is located, the habits of each household member and the level of comfort you require.

For example, in a home with inefficient windows or where insulation is lacking in an area where winter cold is not extreme, thermal curtains can be an effective, straightforward solution with a rapid return on investment.

They are also a smart choice for homes with old or poorly sealed windows where replacement is not planned due to cost, but reducing heating or cooling bills is a priority and improved comfort is desired without construction work.

If your home already has efficient double-glazed windows and good overall insulation, thermal curtains become less essential. In that case, they mainly serve as a decorative complement that slightly enhances comfort without dramatically changing energy consumption.

Thermal curtains combine temperature control, savings, style and sustainability in a single solution. They are a smart, accessible and effective way to improve a home’s energy efficiency without renovations. And if you also combine them with the Endesa tariff that best suits your needs, you can get much more value from this accessory, which is as versatile as it is functional, helping you to decrease electricity consumption during peak usage periods and reduce your expenditure on your monthly energy bill.

Frequently asked questions about thermal curtains

Do thermal curtains save money on electricity and gas bills?

Yes. By helping to keep the indoor temperature of the home more stable, thermal curtains save on air conditioning use in summer, while also reducing electricity or gas bills in winter depending on the type of heating system you have installed.

What type of thermal curtain should I choose for my home?

If you want to protect your home's indoor temperature, multilayer thermal curtains are the best option. Within this category, you have a wide range of possibilities regarding fabrics, materials and levels of insulation. If you also want to block out external light, whether from the sun or from streetlights and illuminated signs outside, the recommendation is to purchase blackout thermal curtains.

What are thermal curtains used for?

Thermal curtains prevent outside heat or cold from entering the home through the windows, and they also stop indoor temperatures from escaping outside. Thanks to their multiple layers of thermal insulation, they help provide greater comfort while requiring less energy for heating and cooling.

Do thermal curtains provide savings in summer too?

Yes. Air conditioning accounts for one of the largest components of electricity consumption during the summer, and thermal curtains can help you save the electricity required to lower your home's temperature by between 5 and 7 °C.

Where should thermal curtains be placed?

To achieve maximum efficiency, install thermal curtains on the windows and large glass doors most exposed to external heat and cold, as their glass panes and frames are the primary escape points for the home's indoor temperature.