How to Make Thermal Lining Fabric

Drapery designers are enlisting thermal lined fabrics these days. Its insulating properties work well in keeping rooms warmer in winter and cooler in summer. The savings for heating and cooling your home make the investment worthwhile. However, even more savings can be realized if you make your own thermal fabrics for use in window treatments or any other application a shrewd consumer can imagine. Finding inexpensive material is probably the most challenging aspect of this project.

Thermal lining improves the insulating property of curtains by a factor of at least seven.
  1. Learn the roles of conduction and convection in applied thermal dynamics. Concerning windows in a house, a pane of glass will conduct (lose) heat through the pane to the cold outside air. Heated (high energy) air particles naturally seek to move to lower energy states (colder, less energetic air particles). When heat is lost by conduction from the air next to windows, the cooled air then sinks and pulls more warm air against the window. This process, called convection, establishes a continual current that will cool your home throughout the night. One component of the insulating mechanism that blocks these processes is that of a thermal fabric.

  2. Construct a thermal fabric by joining or sandwiching together insulating materials along with a vapor barrier. A covering is aesthetically pleasing but optional. The choices for fabric depend on several factors: insulating, conductivity, and vapor or air resistance properties.

    The layer that faces the inner side of two layers (or can be sandwiched between layers if using more than two) is material such as plastic or mylar that has vapor blocking properties.

    Thicker, more dense fabrics provide more insulation than thinner, more shear fabric. Tightly woven fabrics are also more resistant to air flow than those with looser weaves. One study shows that cotton fiber has higher conductivity than a comparable thickness of synthetic fabric. (Ref #2) Synthetic material (the thicker the better) therefore, is a better choice than cotton to insulate your project. Choose polyester batting, recycle old synthetic blankets and bedsheets or use synthetic fleece for the best results.

  3. Connect the layers of fabric together to create one conjoined piece of material. To join the fabric layers, sew or quilt the material together or glue it together with sprayed-, ironed-, or spread-on adhesives. Keep in mind that conduction is further reduced by trapped air spaces between the fibers and layers of fabric, so the more layers, the better the insulation quality.

  4. Make the most of your thermal lining by using a hook and loop closure or magnetic edge seal to reduce convection. Attach the thermal material to the window frame in this way. Infiltration is reduced by using impervious polyethylene as one layer in your material and radiation is reduced by using a reflective metalized poly film, which reflects radiant heat back into your home and also reflects away solar gain in summer.


  • Trapped heat between insulated window coverings and glass windows can reach high enough temperatures to crack glass; periodically open window coverings briefly to release trapped air.

About the Author

Obtained Nursing degree followed by Registered Nurse license in 1984. Have held several positions in long term and intermediate care, acute care and home health with much of this experience in leadership roles. Years of management and staff education give me a solid basis of nursing expertise and medical knowledge. In addition, conducting in-services and community health education forums involves public speaking, an ability I have utilized scores of times.