Duct System Update
I live in a small two floor attached wood frame house with forced hot air and central A/C (added to the hot air furnace about six years ago). We are planning a small extension to our second floor that also involves raising the ceiling height five feet. The HVAC system is a single zone and…
I live in a small two floor attached wood frame house with forced hot air and central A/C (added to the hot air furnace about six years ago). We are planning a small extension to our second floor that also involves raising the ceiling height five feet. The HVAC system is a single zone and is good but not great. One bedroom is clearly underserved because the duct serving that room was added last when one bedroom was divided. Since we’re doing work and enlarging the space, we thought we should consider improving the HVAC system. The few HVAC contractors we’ve spoken to so far suggest adding a second zone, which I don’t want to do because of cost and space considerations. I was hoping the system could be improved by increasing the size of the furnace and updating how the air flow out of the furnace is divided to serve the house. Any other suggestion/thoughts would be appreciated. Especially, should I continue to call HVAC contractors or try speaking with an engineer?
I didn’t even get to your HVAC question because I read this:
“I live in a small two floor attached wood frame house…We are planning a small extension to our second floor that also involves raising the ceiling height five feet.”
Do you have approved plans for this? Enlarging a frame house (particularly up) is quite difficult today under the building code (though not impossible).
Increasing the size of the furnace can only be done by getting a new furnace which will be a lot more expensive than adding a second zone. When I was doing rehabs in larger houses, we always put in two systems…one in the attick for the top floor and one in the basement for lower floors.
To be at all efficient, you need to do this or, more zones. When the blower is forcing air through just one large zone, it will never be efficient near the end of the run.