Hi,
Contact the NHBC and the local council and ask what the minimum temperature a heating system should maintain.
I know that there are definately regulations on this and I think that the regulation is that a property should reach 19C within one hour - but that is just from memory and it is dependant on the outside temperature.
You could even try Corgi, or a larger heating company and ask them for the most up to date regulations in your area.
You will need to log the temperature too. You need to give the builder solid facts eg instead of 'the heating takes ages and is too cold', you need to be able to say 'after the heating has been on for 2 hours and the outside temperature is 16C my house is still at 16C'. Once you have this information use it with the NHBC etc.
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