Hi Zednine,
New homes have to comply with the buidling regulations and NHBC standards if applicable. The house could be in breach of both if it does not have cavity wall insulation. However, insulation can be provided in other ways to meet the standards and regulations.
The applicable building regulations are known as Part L.
The NHBC have an indirect test which states that the central heating system must be able to maintain a living room at 21c when the outside temperature is -1C.
New homes are supposed to have
energy rating certificate but most don't.
I hope this helps
Tony