If it takes very long to heat up a room, chances are that the doors and/or windows are not sufficiently tight. Another indicator are uncomfortably cold areas in front of doors or windows. If the room is equipped with an air condition, gaps in the windows and/or doors will allow cool air to escape and it will take more time to cool down the room.
There is a simple way to discover undesirable gaps between window and window frame: Hold a lit candle at various positions close to the window frame. If the flame of the candle flutters a lot, there are definitely wide gaps that allow an exchange of air. If it flutters just a little, the gaps are still wide enough to affect the room temperature. If it flutters only slightly, but it feels considerably cooler close to the window, there are at least small gaps to prevent economic heating or air conditioning.
Try to test the situation at different positions of the window frame. In this way you get a good idea of where the trouble spots are and are able to address it with a suitable self-adhesive tesamoll® sealing profile. If you discover different gap sizes, use tesamoll® STANDARD or tesamoll® Premium flexible. These products are able to adapt to a wide range of gap sizes.