Insulated window shutters can considerably lessen the amount of heat lost through windows. A standard double-glazed window has a thermal resistance of about R2 (RSI 0.35). An insulated shutter with a resistance 2 to 3 times that of a window, say R5 (RSI 0.88), will substantially reduce the energy loss of that window, particularly at night when the house does not benefit from solar radiation.

In choosing, designing, or building an insulated window shutter, the principal fact to consider is its location with respect to the window. The preferred technical option is to position a window shutter so that it covers the outside of a window and can be operated manually or electrically from the inside.

When an outside insulated window shutter is closed, the window glass will warm up to indoor temperatures thereby reducing, if not eliminating altogether, the potential for condensation on the window glass. The air tightness of the shutter system is not critical and the diffusion characteristic is immaterial. When the window shutter is opened for daytime use, the window may experience rapid cooling in its central region. Although this effect induces a compression stress at the edge, the window can easily cope with this as it is opposite to the stress that occurs with an inside shutter system. When the window shutter remains closed all day, the window will not experience any adverse effects. The two main problems in connection with this system are: 1) the accumulation and control of snow and ice and the effect of strong winds on the shutter 2) the design of the control mechanism required to operate the system from the inside. Although this is the most desirable option from a thermal point of view, it may prove to be the most expensive.

A study of a typical 2-Storey house has shown that 150 sq. Ft. (14 metres sq.) of shuttered windows closed between 11 p.m. and 7 a.m., having an R-factor of 5, saved 18% of the fuel bill.  This is an example case only; the heat energy savings to be expected of insulated shutters must be determined for each shutter type, hours of operation, and specific building features.