It shouldn't feel stuffy at all. If this is the case then it hasn't been commissioned correctly IMHO. A CO2 reading is the quickest way to confirm this. Every home should have one.
"The builder advised it was pd and I went along till I later realised through a architect it wasn't..." I guess this was verbal and not in writing from the builder?
"regardless of construction type, the air in a building will react more to external inputs than internal inputs i.e. solar gain, ventilation and a heating system versus thick stone, brick or concrete walls." isn't that fairly obvious?
Tim
This podcast from Ben Adam-Smith is worth a listen.
Tim Nicholson, Joanne Bowlt and their two boys live in a 1960s end of terrace house in Oxford. Recently they started work on upgrading the property but why did they choose to retrofit?
https://www.houseplanninghelp.com/why-retrofit-a-house-for-energy-efficiency/