From this reply I take you don’t have any experience in thermal calculations and modern building. The thermal envelope of the property heat loss has zero relevance to the location or size of the property.
Nah, I’m just MCS certified in solar and HP systems!
The larger a buildings envelope, the greater the number of heat exchanges occurs with the extenal extremities (enviroment). Insulating the envelope is an important factor but, perhaps more importantly not all building can afford an A rating, whether that is by design or cost to the consumer.
The larger the building, the greater the internal volume to heat or cool…
The design, R value (inc floors), ventillation and solar control all play a crucial factor ensuring thermal comfort. Wrapping the building fabric with insulation, especially those that wern’t built to breathe, without proper attention to adequate ventillation causes issues in itself.
You don’t mention local climate and why its important – What’s the temperature on 1% of the coldest days, the hottest, the humidity, the demand you require. Choosing a HP based on these extremities, rather than averges is important and often overlooked.