Two-dimensional Cutting & Packing problems consist in allocating a set of two-dimensional items into a set (possible singleton) of two-dimensional larger objects in such a way that items are completely contained in the objects without overlapping. A particular instance of two-dimensional Cutting & Packing problem arises in the context of thermal building renovation. This special case deals with the design of insulating envelopes by packing a set of rectangular and parameterizable panels (items) over rectangular facades (objects). Taking into account the particularities inherited from the industrial problem and the need of aesthetic results, we propose in this paper a constraint-based heuristic, named CaSyE, based on guillotine cuts technique. First, we introduce the industrial problem and its particularities. Then, the constraint-definition of the problem is presented as well as the scheme of the CaSyE solution. At least, the results of the heuristic over realistic facades are shown before the conclusion.