What's the difference between 'blackout' and 'room darkening' curtains?

Room darkening curtains typically block 80% to 95% of light through a tightly woven fabric alone, without a dedicated blackout layer. True blackout curtains add a laminated backing, a separate lining, or a very dense triple-weave construction specifically engineered to block light, generally reaching 95% to 99.9%. The terms are sometimes used loosely in product titles, so check the specific stated blocking percentage rather than relying on the word 'blackout' alone.

Do blackout curtains actually save on energy bills?

Yes, to a measurable but modest degree. Brands commonly cite figures around 25% reduction in energy loss through a curtained window, which reflects reduced heat transfer in both summer and winter. The exact savings depend on the window's existing efficiency, the room's sun exposure, and how consistently the curtains are closed during peak heat or cold.

Can blackout curtains be tailored or hemmed to a custom length?

Yes, most blackout curtains can be hemmed by a tailor or with fusible hem tape, the same as any other curtain fabric, as long as the laminated backing is not damaged by excessive heat during the process. For a large discrepancy between the available lengths and the actual window height, hemming a longer length down is usually more reliable than trying to extend a shorter one.

How do I know if a listing's blackout percentage claim is realistic?

Look for a specific stated percentage (such as 98% to 99.9%) alongside a named backing technology (Thermaback, Thermax, or similar branded terms), rather than just the word 'blackout' with no supporting detail. Reviews mentioning the room's actual darkness at a specific time of day are also a reliable secondary signal, more so than the product photos alone.

Blackout Curtains Buying Guide: Backing Types, Sizing, and Care

A complete buying guide to blackout curtains covering backing and construction types, how to size panels correctly, thermal and noise benefits, colorway tradeoffs, and care instructions that extend the life of the blackout backing.

Blackout curtains solve a specific problem, but the category covers a wide range of constructions, price points, and performance levels that all get marketed with similar language.

This guide breaks down what actually differs between products in this category, so a purchase decision can be based on real construction differences rather than marketing terms that sound similar across brands.

Backing and Construction Types

Laminated backing (Thermaback and similar branded names): A foam or acrylic layer bonded to the back of the face fabric during manufacturing. This construction consistently blocks the highest percentage of light, generally 98% to 99.9%, and also provides the most noticeable thermal insulation. The tradeoff is a stiffer, heavier fabric.

Woven-only or triple-weave fabric: A tightly woven fabric without a separate laminated layer, sometimes described as "triple weave" or "three-pass" construction. This typically blocks 85% to 95% of light depending on color and weave density, at a lower price and with a softer drape than laminated options.

Sewn-in lining (Thermax and similar): A separate fabric or insulating layer sewn into the panel during construction, distinct from a laminated backing bonded directly to the face fabric. Performance sits between fully laminated and woven-only construction, often with a more polished finish like a sateen weave.

Layered sheer-and-blackout: A sheer decorative face fabric paired with a blackout lining, giving a softer daytime look. Blocking percentage is typically slightly below a solid blackout panel of the same construction quality.

Sizing Correctly

Total panel width when closed should be at least 2 to 2.5 times the window's width, to ensure full overlap and minimize side light gaps. Mounting the rod 4 to 6 inches beyond the window frame on each side, rather than directly above the frame, closes more of the remaining gap than upgrading the fabric alone would.

For length, measure from the planned rod height down to the intended ending point before choosing a stock length. Most brands offer 63, 84, 95, and 108 inch options specifically because standard lengths do not fit every ceiling height and rod placement.

Thermal and Noise Benefits

Most blackout curtains, regardless of construction type, provide some degree of thermal insulation and noise reduction alongside light blocking, since the same dense material that blocks light also dampens sound and slows heat transfer. Brands that cite a specific percentage (commonly around 25% for both noise and energy loss) are referencing third-party lab testing rather than a purely marketing claim, and this figure is a reasonably reliable point of comparison across brands that publish it.

Colorway Tradeoffs

Darker colors block more light than lighter colors within the same product line, typically by 3 to 10 percentage points depending on construction. This is consistent across nearly every brand in the category. For a room where maximum darkness matters most, choose the darkest available color; for a room where lighter, brighter decor matters more, expect a real tradeoff in blocking performance.

Care Instructions

Wash on a cold, gentle cycle and hang to dry rather than using a hot dryer, which is the most common cause of a laminated backing cracking or separating from the face fabric over time. A light steam or low-heat iron is generally safe for removing packaging creases, particularly on sateen finishes that show creases more visibly than matte fabrics.

Quick Reference

Construction	Typical blocking	Feel	Price tier
Laminated (Thermaback)	98% to 99.9%	Stiff, heavy	Mid to premium
Woven-only / triple weave	85% to 95%	Soft, flexible	Budget
Sewn-in lining (Thermax)	90% to 98%	Moderate, often sateen	Mid-range
Layered sheer-and-blackout	85% to 95%	Soft, decorative	Mid-range