Replace Ductwork?
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Replace Ductwork?

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  • Transcript

    LESLIE: Tracy in Missouri is on the line with an HVAC question. How can we help you today?

    TRACY: Well, what really the deal is is I had a new unit put in a few years back. And when they put it in, I had that – my home was built in 1964 and they had what they called “spider ductwork” back then and it’s just the old, metal, 5-inch ductwork. And they put them in (inaudible at 0:27:42) and extended off that in some area in the house for some bigger ductwork.

    But they said that that existing ductwork would be fine. When they went in and checked it, they said that it was cooling the room fine, because it was in the summer when they did they work. They said there’s a degree or two difference, which they expect – kind of normal, because the way it is.

    But the problem I’ve got is, in the wintertime, my daughter’s room is the coldest room in the house and in the summer, it’s the hottest. They’ve been down there and checked; everything’s properly connected. And they say that they’ve dampered it down a little bit, so it would push air a little more that way, and it’s still not getting in there.

    So my question to you is: would it be wiser to just go and get 8- or 10-inch – one single duct going into that room and just have one duct or extend those two – make those – both of the two existing ones – a little bigger with maybe an 8-inch or something like that? Cost is an issue but I want to make sure that it heats or cools efficiently for my daughter.

    TOM: Is this – does this house have a central return duct or is the return duct also in the same room?

    TRACY: It has a central return duct.

    TOM: Well, obviously, they get it wrong. It’s difficult when you try to use a duct system that was designed for a 1960s house. And I know exactly what you mean when you say “spider duct.” Basically, you had one big plant that came off the heating plant and then a bunch of ducts that were like home runs: every duct went to a separate place in the house, as opposed to having a large duct go down the center of the house and then other ducts come off of that.

    TRACY: Yes, sir.

    TOM: So, clearly, it seems like they got it wrong when they re-laid out the duct system. When these guys have come and said everything’s fine, obviously it’s not fine, because they got it wrong.

    There are calculations. It’s called a heat-loss analysis that you actually do if you know what you’re doing and you’re in the heating-and-cooling business, where you know what compass direction the exterior walls are, you measure how much glass is in the room and you take all these other factors into account. And then you design your system so you’re delivering enough BTUs, be it heating or cooling, to that room to be comfortable in the extremes of the summer and the extremes of the winter.

    So what you’re suggesting now is can you just make a few changes and see if that makes a difference and my answer is: I don’t know. Because I’ve not done that heat-loss, you’ve not done that heat-loss and if I were you, I would get back with the HVAC contractor that put it in wrong to begin with, in the first place, and get them to do that heat-loss, so that we get the right-size ducts going where they should be.

    Now, if they’re not going to do that, then your options would be to hire somebody else that really knows what they’re doing, to try to get that adjusted. But I mean generally speaking, airflow is critical, so you want to make sure you have enough airflow. And in terms of the return, improving the return situation can help.

    And in a bedroom, often that means putting in a vent that goes through the wall, say, into the hall. Doesn’t really supply anything; it’s just kind of a pass-through where more air from the room can get drawn back to the return. Because the more that goes back to the return, the more supply kind of makes that up in terms on the supply side. And that can make the room more comfortable.

    But I hate kind of guessing at this when I know that there is a reasonably accurate and scientific way to do that that these guys have not done.

    TRACY: Alright. Thank you very much, Tom. Appreciate it.

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