We are looking at a home addition possibly this year. Sort of depends on material prices. We started the plans last year but delayed the construction. Our plan adds about 1500 sf to the house. We have an unusual home and it already has 2 forced air furnaces, both original, about 25 years old so no remorse getting rid of those. Only one of the units has an AC system on it, though both are set up to have one. So on the new plan I was going to go to a single heat source. I was thinking I would put in a boiler and run it to 3 zones, 2 to replace the existing furnaces and one for the addition, also forced air and possibly some floor heat. Hot water feeding a coil to replace the old furnaces I figure. I would also put AC on everything but might be able to have one condenser handling 2 of the air handler and 1 standing alone. I have Ecobees now, 3 actually (one is on my shop.) I would ad a 4th for the addition. Any thoughts or comments on that plan would be welcome. Still in the planning stages.