When is heat system duct-work insulated, PA location.

A manufactured home has a compact oil fired forced air furnace in one corner oc a 40x28 manufactured home. A large central duct runs down the middle of an unfinished basement and perpendicular ducts run in the joist spaces. The joist spaces in the basement are insulated with faced fiberglass. The home is in south eastern PA. Seemed like a lot of heat was wasted because the central duct was not insulated. The owner of the home complained of cold and one heating contractor installed a larger central duct (slows down flow further increasing heat loss?)
Should the duct work be insulated and if so roughly how many years to payback?
Thank you for any help!
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On 1/21/2013 5:52 AM, andyeverett wrote:

My triple-wide mfg. home has two ducts going the full length of the house. One for each of the long sections. floor vents connect each room to the full length duct. The third house section has a flexible, insulated duct going under the floor from the exchanger to a single vent in an office space.
Are you SURE of the arrangement of the heat ducts? The central duct you see must have been added after the house was built and in place.
The heat system must have an air return path free of obstructions. That includes leaving room doors open as much as possible. Is the heat duct metal? Should always be insulated. Hot or cold.
Paul in Central Oregon
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On Mon, 21 Jan 2013 09:35:37 -0800, Paul Drahn

Insulated heat ducts in basements are almost unheard of up here in "the great white north" - but our basements are insulated (and heated)
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On Monday, January 21, 2013 12:35:37 PM UTC-5, Paul Drahn wrote:

I'm pretty sure the supply ran in the basement and was probably added after the two halves were assembled. With the furnace on it got warm and if it was insulated I'm not sure the basement would freeze here in Pa, just seemed like wasted money. The owner was a older women who for 5 years had no problems but only now in her sixth season complained of cold, almost seemed like she was complaining of air currents. All the windows were "closed" but some were not latched properly. She had had several heat contractors out to try and solve her problem. One installed a new larger central duct(uninsulated) in the basement but that did not seem to solve her problems, that did not make sense to me as the house worked fine in its original configuration. I'm pretty sure that the house acts as the return to the furnace. The homeowner said she cleaned the filter regularly. I guess its time for another heating contractor.
I will advise the home owner, thank you for your help!
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On Tue, 22 Jan 2013 18:15:08 -0800 (PST), snipped-for-privacy@gmail.com wrote:

two halves were assembled. With the furnace on it got warm and if it was insulated I'm not sure the basement would freeze here in Pa, just seemed like wasted money. The owner was a older women who for 5 years had no problems but only now in her sixth season complained of cold, almost seemed like she was complaining of air currents. All the windows were "closed" but some were not latched properly. She had had several heat contractors out to try and solve her problem. One installed a new larger central duct(uninsulated) in the basement but that did not seem to solve her problems, that did not make sense to me as the house worked fine in its original configuration. I'm pretty sure that the house acts as the return to the furnace. The homeowner said she cleaned the filter regularly. I guess its time for another heating contractor.

Given that it was OK for a few years, it is not the duct. What changed? I'd check that she did not close or open some vents, that a duct did not come apart inside a wall, that the blower switches are going on and off at the proper temperature, that the blower is running properly, temperature limit switches are working properly, and that sort of thing.
Oh, don't for get the chimney or vent for obstructions. Bird's next or dead squirrel can make a difference. Did she lose her cat?
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another issue espically with high efficency furnaces is burner turn on turn off temperature.
in a attempt to maximise fuel efficeny blowers run long after burners turn off. to get the last of the heat from the burners.
this leads to furnaces blowing chilled air at blower shut down making people feel colder. easily fixed by readjusting switches.
another possiblity isnt home repair related at all.
many years ago my mom complained she was cold all the time.......
that peaked out with the furnace running constantly, indoor air temperature of 90 degress farenheit.
i took my mom to her doctor who did blood woork she was severly anemic..
this lady should probably get bood work to confirm the issue is the house and not her........
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On Jan 22, 6:15pm, snipped-for-privacy@gmail.com wrote:

the two halves were assembled. With the furnace on it got warm and if it was insulated I'm not sure the basement would freeze here in Pa, just seemed like wasted money. The owner was a older women who for 5 years had no problems but only now in her sixth season complained of cold, almost seemed like she was complaining of air currents. All the windows were "closed" but some were not latched properly. She had had several heat contractors out to try and solve her problem. One installed a new larger central duct(uninsulated) in the basement but that did not seem to solve her problems, that did not make sense to me as the house worked fine in its original configuration. I'm pretty sure that the house acts as the return to the furnace. The homeowner said she cleaned the filter regularly. I guess its time for another heating contractor.

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On Mon, 21 Jan 2013 05:52:09 -0800 (PST), andyeverett

The heat loss is keeping the unfinished basement from freezing. Insulating the ducts is probably not the problem. Installing a larger duct is not a cure either, unless it was too small to begin with.
What is cold? The entire house or just a room or two? Does the furnace run constantly when it is cold? Sounds like a good evaluation is needed to find what the real complaint is and to find if the furnace is working properly.
Right sized return duct s are a must, clean filters, proper blower speed, balance by partly closing some of the vents, thermostat setting, should all be looked at.
What is the thermostat set for and what is the actual temperature? . I'd also insulate the basement. There is a lot of loss on concrete walls.
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That's my take too. Too little info to even guess what is really wrong. But as you say it isn't likely the uninsulated duct. You would lose some heat from those ducts for sure. But it should manifest itself in slightly higher energy bills, not a cold house. If the cold problem only happened on the coldest day and the furnace was running all the time, then that small loss could explain it. Or if it's only cold in the room farthest from the furnace, then insulating the duct would help some.

He said in one of his posts that he thinks the system uses the house as a return? That would imply that there isn't a return duct system and it's just sucking air from the basement. If that's how it's installed, then it's a big energy loss, because you're sucking cold air from the basement into the furnace and constantly drawing air from the heated house down into the basement, as well as from outside.

Right, we don't even know if the thermostat set temperature is reached or not. I would assume it must be, at least most of the time or there would be one hell of a bill.

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andyeverett wrote:

Irrespective of whether the problem is connected to lack of insulation, almost ALL duct-work should be insulated (excepting that which is in an interior wall). Doing so will at least save on energy bills.
If you can easily reach the duct-work in question, the cost of insulating it should be only a few dollars and a couple hours of time. Duct-work insulation can be had at the box stores.
Payback should be in the neighorhood of one or two months of reduced energy bills.
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wrote:

Not if you want to heat the basement at least a little bit. You have to add heat one way or another so do it the easiest method. The basement does not have to be warm, but at least above freezing.
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Ed Pawlowski wrote:

Agreed. It also depends on how often you want the basement heated and by how much.
An electric space heater might be sufficient if you're only in the basement a couple of times a week to do the laundry.
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wrote:

A whole lot cheaper to just provide a geat register that you cna open or close as required. The heat radiated from the bare pipe into the basement is pretty low, taking in to account the delta T.
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wrote:

Wouldn't change my heat bill at all - I'd just have to open the registers in the basement farther to heat the finished basement.
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Any heat ducts running through unheated spaces should be insulated. I spent several days crawling aorunt on my beck in the crawl space insulating mine (18 x 30 addition).
Harry K
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