With a "new build" I would expect that the regulations for insulation and heat loss and boiler efficiency would have all played their part in the granting of planning permission.
I would assume (maybe incorrectly) that the boiler is capable of heating the radiators adequately.
If I were the builder I to would run away from helping you to solve your problem - it's nothing to do with the quality of the building - it is more to do with teaching the owner how to operate their heating system - the builder has no responsibility here.
It is very likely that your radiators need to be balanced.
As the heated water is pumped around the system each radiator gives up some of the heat in the pumped water - the trick is to balance the heat loss across all the radiators so that those on the back end of the flow still have some heat available to give off.
You may be able to adjust the boiler's thermostat to make the pumped water just a little hotter - you may be able to adjust the system pump to run a little faster to speed up the flow of heated water around the radiators.
"Balancing" is progressively closing - or opening - the lock-shield valve (out flow valve) on each radiator to achieve an even distribution of heat across all radiators.
When this is done you can then adjust the inlet valves of the radiators to make the rooms you need to be warmer - warmer - and the rooms you do not need to be as warm - less warm, Bedrooms for instance - seldom needed to be as warm as the lounge - you can often turn these radiators down really low.
Have a heating engineer come in and "tune up" your heating for you. You will get little to no help from the builder - why should he care?
Peccavi, January 2011
