According to Ukrainian standards vent valve in the dormer window is optional, but recommended elements.

Dormers FAKRO equipped with Vsepogodnoy Ventilyatsii through which room air comfortably in any weather all year round. In the warm season, a room can be ventilated by an open window, which provides supplies FAKRO 5 position fix half-open window.
In the cold attic can be ventilated with the integrated vent valve. Valve is located at the top of a window box. Vent valve V10 in a model FTS-V U2 with a capacity of 10m ³ / hr (at 10 Pa) can be used in areas where a properly designed ventilation system. Plastic element vent valve prevents the moisture in the wood of the window. The air flow is regulated by a special mechanism. Filter mounted in the valve, do not miss a large dust, feathers and insects.
Antikondensatny vent valve V35 with a large bandwidth of up to 43 m ³ / hr (at 10 Pa) ensures better air exchange. Additional rubber seal on the outer side of the window provides more tightness on the outside plate. The design of lining provides an additional insulation. When malfunction of ventilation in the building, the ventilation device V35 works on the outflow of air, outputting used, moist air from the room. Valve design eliminates possible in this case, the appearance of condensation between the door and a window box, so the window will last much longer. The air flow is regulated by a special mechanism. Filter mounted in the valve, do not miss a large dust, feathers and insects. This valve is installed in models of FTP-V U3, FTP-V U3 and preSelect ^® (FPP-V U3).