If your ductwork has manual dampers on the trunk lines, they need to be adjusted for the cooling season to direct more cold air upstairs. You'd be looking for metal handles on the ductwork which open/close each trunk line, if they are installed. Technically your ductwork should be designed such that the manual dampers aren't necessary. Heat pumps are designed for cooling load.

Thanks Ryan,

I'll have a look and see if there are any handles in place.

We're on the west coast in Canada, so I don't know if cooling is the focus of the installers here.

Ryan, I am guessing that the air handler has these handles?
Can these handles to redirect the cooled air upstairs be retro fitted?

Thanks for responding.

What the previous poster meant that your ductwork, or where the ducting splits into the upstairs and downstairs runs, MIGHT have a damper that can be adjusted to direct more or less air into one space or the other. Think of a gate that can be opened and closed.

If not, your HVAC dealer can install some "retrofit" dampers to make you more comfortable. If all of your ductwork is enclosed in walls and ceiling, they may need to do a bit of "house surgery" to accomplish this.

Also, they may be able to set your air handler to run at a lower overall speed. This would slow down the airflow in the entire system, but may be satisfactory.

Thanks juliekcmo,

I will contact the local HVAC dealer, and find out my options.
What would slowing down the speed accomplish?

And, wouldn't slowing down the speed affect the whole house cooling/heating?

The house is 9 years old, I don't know why the gate wasn't installed in the first place.
Thanks.

yes slowing the speed will most certainly affect the whole house cooling and heating. But it may be an easier and less costly option to try first before going to the mess and expense of adding in retrofit dampers.

If you haven't done so already, see if some of your individual room vents can be closed off somewhat. Closing them on the lower level may help force more cooling upstairs.

Is there a problem with the heating being uneven, or just when cooling? If it is really only with the cooling, then the solar heat gain from upstairs windows and skylights is probably what is the source of the problem. Additional window coverings can make a difference to reduce solar gain, especially on east/west glass.

Yes, I agree that the solar gain is the sorce of the problem.

I called the local HVAC dealer, he said that I should call him again during the cooling months and he'll come over and have a look.
Over the phone he suggested that I could entertain a dual zone, but this would be costly.

I'll try partially closing the lower floor ceiling vents (again) and see if I can live with this configuration.

Thanks both for your help.