I have ducted central heating in my flat and think the problem is that the system is very inefficient. My flat is on one level, well insulated and double glazed, yet I still struggle to keep an even temperature all round.
I found out after I had bought the place that most people in the block had changed to radiators many years ago.
El Sqad, the only ones I've come across were in bungalows, so, single level. I can see where the laws of physics would take over with a duplex. Invariably, the fault was with the fan not coming on when required. Is your system fan-assisted?
The builder.........thanks........I have no idea as the main "thrust" is on the roof.....BUT.......I can hear a "whiiiir" in the garage when it comes on.
Sounds like it. If there's no fan running to distribute the warm air around the lower floor, then it all rises to the highest point.
Do you have a wall-mounted thermostat?
Yes......thermostat downstairs and a separate one upstairs...........but it matters not to which temps you set them OR which fan speeds one selects............cold downstairs and hot upstairs.
If you cannot prevent the warm air downstairs from going upstairs by shutting a door then turn the upstairs heating right down and set the downstairs at the temperature you want. Leave it for a day or so to come to equilibrium. If it is still too cold downstairs and too warm upstairs then you need to impede the flow of warm air to the upstairs. A curtain at the bottom of the stairs would be my first recourse, if that doesn't work then a door is probably necessary. Could it be that the warm air upstairs is escapung somwehere, thus allowing cold air to enter downstairs?
Ok. It needs to be looked at by a heating electrician. Various things...... fans, thermostats. Simple things that can affect the whole system. Sometimes there's even a thermostatically controlled shutter that closes off the duct when not in use. That could be closed somewhere.
I'm desperately trying to avoid reference to thermostatic flaps as it might invite innuendo from some of your female followers ;o)