Curtain Lining Types, Compared

A lining sits behind the face fabric and does the work the face fabric cannot: blocking light, holding heat in, and giving the curtain a fuller hang. The three you will be offered are blackout, thermal, and interlining. Blackout blocks light, thermal holds heat, and interlining adds body and warmth. Most people pick one based on the room, then order the lining to match the face fabric.

Published June 27, 2026. Source: US Department of Energy, energy-efficient window coverings.

What does curtain lining actually do?

A lining is a second cloth hung behind the face fabric, and it earns its keep in three ways. It protects the face fabric from sun fade, which is the main reason even cheap curtains last longer lined. It adds weight, so the curtain hangs in proper folds instead of flapping flat. And it changes how the window performs, blocking light or holding heat depending on the lining you choose. The face fabric you fell in love with is rarely good at any of that on its own.

One number puts the heat side in context. The US Department of Energy says about 30% of a home's heating energy is lost through windows, and that conventional draperies can cut that loss from a warm room by up to 10% when hung close to the glass. A purpose-made thermal lining does more than a plain one. That is why lining is a quiet money decision, not just a finish.

Blackout or thermal lining: which do I need?

Pick blackout for darkness and thermal for warmth, and know that most linings now do a bit of both. Blackout lining is a tightly woven, usually three-layer cloth made to stop light. It is the one for a bedroom, a nursery, or a room with a television, where a sliver of dawn light at the wrong hour matters. Good blackout lining blocks up to 99% of light, though no curtain is truly total, because light still leaks around the edges unless the curtain overlaps the wall.

Thermal lining is built to slow heat rather than light. It has a brushed or lightly coated back that traps a layer of still air between the curtain and the glass, which is what insulates. You feel it most in winter, on single-glazed or draughty windows. The two overlap, so a heavy blackout lining keeps some heat in, and a dense thermal lining dims a room. If you want both, ask for thermal blackout lining and buy it once.

• Blackout stops light. Best for bedrooms and any room you want dark on demand.
• Thermal slows heat. Best for cold rooms, big windows, and old single glazing.
• Thermal blackout does both in one cloth, the usual pick when you cannot decide.

When is interlining worth it?

Interlining is worth it when you want the curtain to look and feel expensive, or when the window is genuinely cold. It is a soft, fleecy layer, often a cotton or synthetic bump, sewn between the face fabric and the lining. That middle layer is what gives a hotel-quality curtain its deep, heavy folds and its dense, sound-softening hang. It also adds real warmth, more than a thermal lining alone, because you have three layers of cloth between the room and the glass.

The catch is cost and weight. Interlining means a third length of fabric to buy and far more hand-work to make, so an interlined pair can cost noticeably more than a plain-lined one. It also makes a heavy curtain that needs a sturdy pole or track. Save it for the rooms that earn it: a formal living room, a draughty period window, a bed you want to feel like a den.

How lining changes your fabric order

Lining is cut to the same number of widths as the face fabric, so a lined pair is roughly two lots of cloth: the face fabric plus a matching length of lining. Interlining adds a third. The important thing is the order of operations. Work out the face fabric first, since it carries the pattern and sets the widths and the repeat, then order the lining to match the width count. Lining has no pattern, so it does not need a repeat allowance, which is the one place it costs less.

The curtain fabric calculator gives you the lining quantity alongside the face fabric, in inches or metric, so you order both in one go. If you have not set your widths yet, start with how to measure for curtains and the fullness and pleat guide. The heading you choose also affects how the lining is attached, so it is worth deciding both together.