Curtains – The Surprise Insulation



Insulation is measured as an R value. The higher the R value the better it is at stopping energy transfer throughout the home.

When calculating R values, each layer of an element is taken into account. This includes materials such as glass, bricks, timber, plaster, fabric etc. and also air gaps and the air movement within those air gaps. With this in mind, various internal window furnishings were analysed.

The R value of windows with internal coverings is reliant on the chosen covering and the inherent properties of fabric choice.

When using window furnishings to achieve an air gap, sealing the gap is important. Blinds that have many gaps such as venetians, vertical drapes and open weave or lace curtains provide very little or no sealing of the air gap. A holland blind or closed weave curtain provides some sealing, but air is still able to escape at the top of the furnishing near the rod or bracket.

Using curtains/drapes and pelmets achieve much better insulation results. The difference between a closed weave curtain and a drape is the rubber backing attached or fitting closely the curtain which provides additional insulation to the glass-air gap-fabric system. Adding a pelmet seals the air gap around the rod/bracket, applying both gives 220% improvement on a window that isn't covered.

Curtains and drapes must be fitted externally to the window frame and continue around the side of the rod/bracket to line up with the wall. As a suggestion aluminium slide rails could be used rather than ornate timber rods, which will probably be covered by a pelmet anyway if the curtains or drapes are installed correctly. Curtains should run all the way to the floor and be as close as practical to the floor surface, shorter curtains on shorter windows is not usually recommended.

Energy efficiency as increased the awareness of manufacturers to use the principles described to achieve a better product. This includes the use of air gaps within blinds and reflective coatings on blinds deflecting heat from the outside way from the house in warmer months. Using external blinds, awnings and pergolas is also important in some climates as they stop some or all heat from entering the house.

Available at Budget Curtains Nowra and Budget Curtains Batemans Bay