What's up with this HVAC setup?
October 11, 2019 7:58 AM Subscribe
We are looking at a house that is 100-ish years old. The ducting system is not one I'm familiar with and I'm wondering if it's going to be an issue or not. I've been looking online and I can't seem to find a name for it.
My current house (80 years old) has what I assume is a fairly traditional setup. Furnace in the basement, big ducts along the ceiling that go up through the walls and flow into the room via wall vents. The upstairs rooms each share a duct with a downstairs room. So, say you close the one of the vents in the living room, it will increase the airflow to the upstairs bedroom for which it shares a duct.
This house we're looking at is another beast, though. I believe it used to have a boiler or maybe even a gravity furnace. There are no wall vents, only floor vents on the first floor. There is also a large duct that goes up the center of the house into the attic (3rd level), where it branches off and insulated ducting runs along the floor to each of the 2nd floor rooms and vents out from the 2nd floor ceiling.
This seems like... a not great system. I would assume that there is a ton of risk of heat loss in the attic (hence all the insulation) leading to ice damming. We would also consider adding central AC if we bought the place and I have no idea how well that would work with this system. Also, all that ducting along the attic floor (at least 6 separate branches) make the attic really difficult to use for storage of anything large and/or heavy.
Anyway, if anyone knows a name for this type of ducting system, I'd love to know it so that I could do some research on the pros & cons.
My current house (80 years old) has what I assume is a fairly traditional setup. Furnace in the basement, big ducts along the ceiling that go up through the walls and flow into the room via wall vents. The upstairs rooms each share a duct with a downstairs room. So, say you close the one of the vents in the living room, it will increase the airflow to the upstairs bedroom for which it shares a duct.
This house we're looking at is another beast, though. I believe it used to have a boiler or maybe even a gravity furnace. There are no wall vents, only floor vents on the first floor. There is also a large duct that goes up the center of the house into the attic (3rd level), where it branches off and insulated ducting runs along the floor to each of the 2nd floor rooms and vents out from the 2nd floor ceiling.
This seems like... a not great system. I would assume that there is a ton of risk of heat loss in the attic (hence all the insulation) leading to ice damming. We would also consider adding central AC if we bought the place and I have no idea how well that would work with this system. Also, all that ducting along the attic floor (at least 6 separate branches) make the attic really difficult to use for storage of anything large and/or heavy.
Anyway, if anyone knows a name for this type of ducting system, I'd love to know it so that I could do some research on the pros & cons.
I am not an HVAC expert, just a homeowner, but...
This just sounds like a typical forced hot air system to me. My house has ducts in the attic, only instead of a large air duct running from the basement, there is hot water going to an air handler and then it gets converted to hot air, but there are still ducts running through the attic to ceiling vents.
You're correct about heat loss, there will be some, though insulating the ducts may help with that.
The loss of storage is certainly a factor with this sort of system, but you could always put shelves over the ducts.
Are there return ducts anywhere? You can't put hot air into a room unless you also remove the same amount of cold air.
There are more efficient ways to heat a house, but this isn't anything really crazy.
posted by bondcliff at 8:29 AM on October 11, 2019 [4 favorites]
This just sounds like a typical forced hot air system to me. My house has ducts in the attic, only instead of a large air duct running from the basement, there is hot water going to an air handler and then it gets converted to hot air, but there are still ducts running through the attic to ceiling vents.
You're correct about heat loss, there will be some, though insulating the ducts may help with that.
The loss of storage is certainly a factor with this sort of system, but you could always put shelves over the ducts.
Are there return ducts anywhere? You can't put hot air into a room unless you also remove the same amount of cold air.
There are more efficient ways to heat a house, but this isn't anything really crazy.
posted by bondcliff at 8:29 AM on October 11, 2019 [4 favorites]
This sounds like what we have in my house.
The upstairs rooms furthest from the central stack tend to be the hardest to keep warm. We purchased vent covers to cover some of the downstairs vents, which forces more air into the upstairs. I prefer this to the forced hot water system we had in our previous house,
As for central air, ours is in the same system, uses the same ducts. No issues there.
posted by neilbert at 8:37 AM on October 11, 2019 [1 favorite]
The upstairs rooms furthest from the central stack tend to be the hardest to keep warm. We purchased vent covers to cover some of the downstairs vents, which forces more air into the upstairs. I prefer this to the forced hot water system we had in our previous house,
As for central air, ours is in the same system, uses the same ducts. No issues there.
posted by neilbert at 8:37 AM on October 11, 2019 [1 favorite]
we live in a 100 year old house. we installed separate AC units in our attic and basement and left the radiators in place. our register/duct layout is identical other than the absence of a giant central duct to the third floor.
the ductwork in our basement is kinda spidery since it had to run along floor joists. the ductwork in our attic just runs under the edge of the roof in what would be mostly useless space anyway.
posted by noloveforned at 11:07 AM on October 11, 2019
the ductwork in our basement is kinda spidery since it had to run along floor joists. the ductwork in our attic just runs under the edge of the roof in what would be mostly useless space anyway.
posted by noloveforned at 11:07 AM on October 11, 2019
Ducts in attics are very common- think of possible alternatives like boxing out areas of ceiling to conceal the ducts. Much more expensive, and probably an aesthetic issue as well.
When I had second floor air installed in my 1930's house, I had them run the ducts around the perimeter of the semi-finished attic space that my daughter liked to use as a play room.
I then boxed around it and used that cheap plywood board that looks like tongue in groove wood on the sides, and clear 1x lumber on the top. Then stained it to match the wood flooring.
This was then a bench seat.
Residential ducts have to be insulated to R5 if inside the building envelope, or R8 or R12 if not, depending on which climate zone you are in. The R12 is new, and may not have been in the code when your work was done. Unconditioned attics are considered to not be in the building envelope.
posted by rudd135 at 8:42 AM on October 12, 2019 [1 favorite]
When I had second floor air installed in my 1930's house, I had them run the ducts around the perimeter of the semi-finished attic space that my daughter liked to use as a play room.
I then boxed around it and used that cheap plywood board that looks like tongue in groove wood on the sides, and clear 1x lumber on the top. Then stained it to match the wood flooring.
This was then a bench seat.
Residential ducts have to be insulated to R5 if inside the building envelope, or R8 or R12 if not, depending on which climate zone you are in. The R12 is new, and may not have been in the code when your work was done. Unconditioned attics are considered to not be in the building envelope.
posted by rudd135 at 8:42 AM on October 12, 2019 [1 favorite]
« Older British pre-WWII girls' boarding schools: help me... | Rip an interactive DVD to create a playable video... Newer »
This thread is closed to new comments.
posted by nickggully at 8:26 AM on October 11, 2019 [1 favorite]