Thermal insulation layer, in spaces that are constantly heated, need to be on the outside, because it is preferrably from the aspect of diffusion of water vapor and barrier thermal stability. Besides, in case where thermal insulation is on the inside, object construction is much more exposed to temperature oscillations. Thermal insulation on the inside can be acceptable just in objects that are perioadically heated.
Most important is to keep in mind the physics processes of object, especially diffusion of water vapor, while making insulation of roof stractures. Considering that, thermal insulation layer in roof structures has to be porotected with two foils. On the lower side vapor barrier, to prevent diffusion of water vapor, and the upper side “condensation foil”, wich is waterthight but vapor permeable. Therefore, some water vapor can evaporate, while summer months. Recommended thickness of thermal insulation layer of roof structures is min. 16cm.
EPS with slope is mostly used for flat roof structures, but in case that is classical flat roof (thermal insulation under hydroisloation). For the reverse flat roofs is necessarily to use XPS, because of exposure to humidity. EPS with slope is a very good replacement for concrete with slope, especially because of its weight.
EPS has no duration. Facades made before 50 years are proof for that. In those facade systems thermal insulation layer completely fulfills his function. While making facade every layer in it’s system has to be installed according to the rules of profession and manufacturer’s requests.
EPS is a material that does not support fire, but when temperature is higher of 100oC it melts and leaks. But when facade system is made by regulations of profession, according to EU standards it satisfy norm B1, wich means that it can be normally used for facade systems.
We can check does EPS meets all terms of building physics if useing some programs for it, while projecting objects. Those terms are for example diffusion of water vapor, condensation and draining.