New high-tech smart windows have a great impact on reducing heating and cooling costs in buildings in comparison with the conventional window systems. However the initial costs of these windows are rather too much. This paper demonstrates two new methods for constructing low-cost smart windows that can respond to the level of thermal condition according to basic laws of thermodynamics. The first method is based on the variations in pressure of a trapped gas at different temperature conditions which can move up and down a thin layer of a colored liquid as a sunshade, and the second one is a two phase liquid liquid (transparent translucent) fluid with different thermal expansion coefficients that allows one phase to rise or sink faster than the other one, in response to temperature variations, and thus casting or retracting an opaque light filter. The calculations and results of experimental tests showed that not only the incoming light can be adjusted without the use of electricity, but also the initial costs of construction can be reduced. (C) 2016 Elsevier Ltd. All rights reserved.