Rooms can be cold for several reasons – often we find draughts, poor cavity wall insulation or loft insulation. As part of your new build handover process, you will no doubt have had an air test. The issue with this is that it can be conducted on a similar property or corners are cut to cheat (taping up areas of heat loss to make it pass is common, for example, trickle vents and around skirting).
Commonly we find a lack of efficient heating systems and it can be something as simple as the radiators not working… In some instances, the heating is completely incorrectly connected or in the example shown below, it is often the underfloor heating system not in the room at all!