Calculated Moisture Conditions in Building Constructions. Part of "Hygrothermal Properties of Alternative Insulation Materials".The hygrothermal performance of constructions with alternative insulation products has been analysed with the 1-dimensional computer model MATCH for combined heat and moisture transfer. The analysis concerns both traditional wall and roof constructions with the alternative insulation products, and some alternative designs prescribed by manufacturers of alternative insulation materials. The choice of construction types originates both from an official direction on energy efficient building design, and from a catalogue of alternative construction layouts advised by a manufacturer of alternative insulation. The analysis comprises the use of flax, cellulose fibre, perlite, glass wool, and rock wool.The analysis has shown that alternative insulation materials can be used in place of mineral wool in a large number of traditional Danish and alternative building constructions. However, one should be aware of the hygroscopic moisture that is entrained with the organic types of alternative insulation. This must not accumulate in other building parts to which it will migrate in some seasons. Thus, constructions that are ventilated to the outside may be better to use when the insulation is hygroscopic. There is no particular advantage for the analysed constructions in using a somewhat permeable vapour retarder. The inorganic alternative insulation material, perlite, seems to have much the same hygrothermal performance as mineral wool.