A reformer installation for generating a hydrogen-rich product gas from a hydrocarbon-containing fluid, includes a housing having an interior, at least one reformer zone disposed in the interior of the housing and at least one feed line leading to the housing. A thermally insulating heat shield causes a reduction of an operating temperature in the at least one reformer zone by 50% to take at least 8 hours and preferably causes a reduction of the operating temperature in the at least one reformer zone by 20% to take at least 8 hours. This improves the cold start performance of the reformer installation, since the reformer installation is prevented from cooling off too quickly. That is particularly advantageous for the use of reformer installations of this type in automobile construction, since those kinds of reformer installations are activated again and again at certain intervals.