One of the main functions of the window is to let you control the amount of light and hot/cold air that enters the house without using any sort of electricity. It is a conventional proven effective future-proof method to regulate temperature. Of course, it depends on the seasons; in summer, the window lets hot air to come in, while in winter it becomes a tunnel through which cold air travels. Either way, it affects your energy usage because you need to adjust the central heating system to get a comfortable temperature. With the right treatments, however, you can make not only attractive blinds and curtains, but also the energy-saving ones.
There are several factors to determine how effective draperies are in reducing energy usage for examples of colour, thickness, and type. A wide range of options with combinations of styles is available in the market, making it nearly impossible to determine their energy-saving properties inaccurate numbers. As a general rule, multiple heavy layers of fabric provide the best thermal protection.
During hot summer days, you can close the draperies particularly on windows that receive direct sunlight to minimise heat gain. Draperies tend to stay at a cool temperature in summer because folds and pleats lose heat through convection. In winter, draperies prevent heat loss from the house, making it a little bit warmer without putting too much work for the heating system.
To optimise draperies’ thermal protection ability, you need to hang them as close to the window as possible and let them fall onto the floor or windowsill. A cornice at the top of the draperies is also a good idea. Instead of using only one drapery for a big window, hang two draperies together to create tighter air space. The drapes should be on the sides, so the two draperies meet or overlap in the centre; use magnetic tapes or Velcro to attach the drapes to the wall. Such method creates better insulation that you can reduce heat loss by up to 25%. Draperies stay at more or less the same temperature as in the interior space as well.
Roller blinds created using insulating fabric are best to prevent heat gain and loss. Cellular blinds or honeycomb shades can trap air within cells, making them efficient for energy-saving purpose. It is also recommended to install external blinds and awnings during hot summer days to help block the amount of light or heat from entering your house. When choosing external blinds, pick one that has white or near-white colour because it can reflect more heat back to the outdoor environment.
Read an interesting article detialing how blinds can save you on energy cosets here: http://energy.gov/energysaver/energy-efficient-window-treatments
When installed on south-facing windows, awnings can reduce solar heat by up to 65% and improve to 77% on west-facing windows. Ideally, awnings should cover the entire side of a house, but one on top of each window should suffice to deliver a noticeable difference.