What is a thermal curtain lining?
Updated
A thermal curtain lining is a second layer behind the face fabric, chosen for its effect on heat moving through a window. The Australian Government's YourHome guide says heavy fabrics and several layers of fabric help a curtain insulate, and that closing air gaps around the edges improves performance. Your retailer can talk you through the fit.
The name thermal lining is used for a lining chosen for its effect on heat. A lining is a second layer of fabric behind the curtain's face fabric, so it puts an extra layer between the room and the glass. How much it helps depends on the whole window, including how well the curtain closes it off at the top and sides.
What the Australian Government's YourHome guide says
The Australian Government's YourHome guide says window furnishings such as blinds and curtains can improve the thermal performance of windows, and are especially useful added to existing windows. It says snugly fitted blinds and curtains with pelmets trap a layer of still air next to the window, which reduces convective heat transfer through it. It also says heavy fabrics and multiple layers of fabric help the insulation of a curtain by reducing heat flow between the air in the room and the air next to the window.
For summer heat, the guide says internal blinds are much less effective than stopping the sun's heat from entering the window in the first place. A lining is one part of managing heat at a window, not the whole answer.
Fit and air movement
The guide says to eliminate air gaps around all the edges of the curtain and pelmet to improve performance, and that the benefit is reduced if there is air movement around the curtain. So how the curtain closes off the top, sides and bottom of the window matters too, not only the lining.
How Speedy Blinds fits a separate lining
A separate lining is its own fabric, hung behind the face fabric. At Speedy Blinds the face fabric and the lining are sewn together across the top heading. The sides are connected with tag fasteners, so the two layers hang and move independently, and the bottom of the lining is left to hang freely.
The lining faces the window and takes the sun, which helps the face fabric last. A second layer also gives a light fabric more weight and fuller folds.
What to ask your retailer
Tell your retailer what the room is used for and which way the window faces. Ask which lining they suggest and what it is made of, how the curtain will close off the top, sides and bottom of the window, and whether a pelmet is an option. Ask to see the fabric with the lining behind it.
Other ways people ask this
Does a thermal lining make curtains blockout as well?
Only a blockout lining does. Other linings add body and protection but still let light through. If you want light control as well as help with heat, tell your retailer so they can recommend a lining and show you the fabric with it.
Will a thermal lining keep the heat out in summer?
The YourHome guide says blinds and curtains can improve the thermal performance of windows. For summer heat it says internal blinds are much less effective than stopping the sun's heat from entering the window in the first place, so a lining is one part of the answer, not all of it.
Does the way a curtain fits change how well a lining works?
The YourHome guide says to eliminate air gaps around the edges of the curtain to improve performance, and that the benefit is reduced if there is air movement around the curtain. Ask your retailer how the curtain will close off the top, sides and bottom of the window.
Is the lining attached to the curtain?
At Speedy Blinds a separate lining is sewn to the face fabric across the heading, connected with tag fasteners at the sides and left to hang freely at the bottom.
This answer is general information. For your own windows, your retailer's advice and your order with them come first.