Building an addition on your home can be really exciting, especially if you've been making do with less space than you need for some time. However, it's important to put some thought into the building process and take your time to ensure everything is designed properly. One aspect to concentrate on is how you will heat and cool the addition. You have three basic options:
Extend your current heating and cooling system.
If your furnace and air conditioner are a bit larger than is really needed for your home, you may be able to just have an HVAC contractor add some ducts onto the existing system. Your furnace and air conditioner will blow air through these ducts, just as they do the other ducts in your home. The temperature of the addition will be monitored by the same thermostat that you already have.
Upgrade your furnace and air conditioner.
Chances are, if the AC unit and furnace you have were properly sized for your home at the time they were installed, they are not actually powerful enough to also regulate the temperature of the addition. So, rather than just connecting more ducts to the system, your HVAC contractor may also need to replace your current appliances with larger ones. They should still be able to be integrated with your existing thermostat -- and you'll still control the temperature of your entire home with that one thermostat.
Install a freestanding HVAC system.
If your HVAC contractor tells you that your current furnace and AC unit can't effectively cool the addition, another option is to leave your current system in place and install an entirely separate one for the addition alone. This is actually a good choice if you'll be using the addition as an inlaw suite or for guests to stay in. If the people in the addition don't prefer the same temperature you prefer in the rest of the home, they can use the separate thermostat and change their temperature.
Assuming the addition is only a few rooms, you probably won't need an entire other central HVAC system. Instead, your contractor can install what is known as a ductless heat pump on the wall. In the winter, this heat pump will blow warm air into the home, and in the summer, it will act as an air conditioner. There are no ducts involved, which simplifies the building plans.
To learn more about each of these options, speak to an HVAC contractor in your area.