NOVELTY - A water permeable sheet has a water vapor transmission rate of at least 200 g2/m2/day at 25degreesC and 75% relative humidity, and a mean dimensional stability (over 100 cycles) for a wet or dry sheet in any direction parallel to the sheet surface of less than 15% change in linear dimension.    USE - The water permeable sheet is used as recuperator membrane to manage heat, water and humidity levels in the reactant streams of a fuel cell (e.g. polymer electrolyte membrane fuel cell, alkaline fuel cell, phosphoric acid fuel cells, molten carbonate fuel cell or solid oxide fuel cells) (claimed).    ADVANTAGE - Improved mechanical properties, is dimensionally stable, highly water permeable, and acts as good gas barrier between streams of fuel and oxidant gases.    DETAILED DESCRIPTION - A water permeable sheet comprises a laminate of a substantially water permeable first layer bonded to a supporting porous layer comprising a matrix of water insoluble fibers of inorganic mineral and/or porous plastic film, optionally polyethylene or polypropylene, and/or matrix of water insoluble fibers impregnated with a water-permeable material. The sheet has a water vapor transmission rate of at least 200 g2/m2/day at 25degreesC and 75% relative humidity, and a mean dimensional stability (over 100 cycles) for a wet or dry sheet in any direction parallel to the sheet surface of less than 15% change in linear dimension.    INDEPENDENT CLAIMS are also included for:    (a) A method of making laminated sheet comprising preparing a web of water permeable film, bonding the web to a porous support layer and optionally applying an adhesive layer to form a multilayered web;    (b) A method of making an impregnated sheet comprising immersing a porous fibrous matrix in a bath containing water permeable material and regenerating the water permeable material within the matrix;    (c) A power source/vehicle comprising at least one fuel cell; and    (d) A method of manufacturing a fuel cell recuperator comprising locating a sheet in fluid connection with any conduit which carries reactant into or out of a fuel cell.