First thing, Taylor Wimpey should be sorting the mould issue out!
There are serious health consequences for anyone living with mould in their home.
The usual response from house builders for condensation and mould is that it is the buyer's "lifestyle" that is causing or making it a lot worse. But as you say you are using your extractor fans, the trickle vents are permanently open and your home is heated. You should never dry washing indoors without proper ventilation and you should open the windows when the weather allows.
So what are your options:
In the short term, you should by a dehumidifier. I have a DeLongi one I bought on Amazon for £130. Well worth the money. Once the condensation is under control treat any surface that has mould on it with a diluted bleach solution, this will kill the mould. Do not do this for fabrics as it will bleach the colours. Wash clothes and fabrics in a bio wash.
In the longer term the probable cause is likely to be a building defect. Perhaps your extractors do not connect to the outside air?
See similar problem to yours here! It may also be caused by the external wall DPC level not being at least 150mm above finished ground level. Another cause may be a leaking gutter, downpipe or dripping overflow. Look for green on the outside walls or paving. Whatever the cause Taylor Wimpey should be sorting it out. Write to the NHBC if they fail to act positively.
Most New homes have cavity wall insulation to meet the requirements of the Building Regulations. The only exceptions are timber frame construction where the timber frame is insulated. From what you have said, I would almost certainly think you have a timber frame new home as
condensation is one of the drawbacks of this type of construction.
The size of radiators is dictated by the temperature the standards require for the room they are heating and the volume of that room measured in BTU. (British Thermal Units) . The NHBC list the temperature required for each room Living bedroom bathroom etc based on the external temperature.
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