Three story homes and heat

[NoHolidaysforyou]

We used to live in a three story semi detached home and it was always boiling in the months that weren't winter (which was then fine). We now live in a two story detached home and it is so much cooler. What I'm wondering is why was the three story home so much hotter? Was it because it was three stories or because it was semi detached? I also wonder because I have been looking at floor plans that we might choose in the future and some include a fourth bedroom/fifth bedroom on a third floor. Would a detached three story home also be very hot to live in?

Think it all depends on your insulation.
Detached houses will generally be a bit cooler than semi or terraced. Top floor loft bedrooms are very hard to cool down in a hot Summer, ime. But I don't think that heat moves down, if that's what you're asking. I don't think having a third floor makes your house warmer.

My thoughts would be that a third floor acts as an extra layer of insulation from the outside?

Detached vs semi vs terraced makes a huge difference to heat retention. In a terrace you have neighbours both sides keeping the heat in whereas in a detached all sides of your house are exposed.

Heat rises. I have a three storey town house. Ground floor is quite cool.