Why Closing your Air Vents Will NOT Save you Money???

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A local Plumbing contractor says the following:
“In the case of a central heating and air conditioning system, closing off vents has the same effect as a dirty air filter. It simply restricts airflow. Heating systems are designed to heat the whole home and are sized accordingly. Shutting off a section of airflow increases the air pressure in the system, in turn increasing the amount of duct work leakage."
"A more energy efficient way to control individual temperatures in unused rooms is by using a ductless heating and cooling mini split systems that are mounted on the wall and wired using a simple wiring process to an outdoor unit. No ducts are used so installation doesn’t take much time at all. Ductless heating and cooling mini split systems are a flexible solution.”
My question: Is closing the ducts to three unused bedrooms and an unused bathroom a bad idea and it won’t save any money on the gas bill?
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On Wed, 27 Jan 2016 08:06:30 -0500, Arnie Goetchius

Correct You make the furnace work harder and less efficiently by closing off the ducts unless your furnace is undersized for the home (which is EXTREMELY rare. Most furnaces are at least 50% oversized
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On Wednesday, January 27, 2016 at 8:13:12 AM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

Wrong. There is no such thing as "working harder". If you have a couple rooms that are unoccupied and you close them off and close off the heating vents, you will burn less fuel, because you're heating less space. And if you have leaky ducts, they need to be fixed. In extreme cases, if you closed off a lot of vents then you could have problems, more likely with ] AC than with heating. I have two rooms cut off that way, heating system works fine.
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On Wed, 27 Jan 2016 05:24:06 -0800 (PST), trader_4

Good God we agree. If you close off "too many" ducts it can be a problem. But one or two rooms in a normal house shouldn't be too big a deal - make sure the remaining vents are open all the way.
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On 1/27/2016 7:13 AM, snipped-for-privacy@snyder.on.ca wrote:

While I agree that closing off ductwork will increase the back pressure and cause "leakage" (unless the installer was absolutely anal about sealing all seams and joints with metal tape, etc) the only downside that I visualize is that the blower motor will have to work harder.
Let's look at an average home of ~1500 sq feet with 3 bedrooms and the thermostat for the FANG system centrally located in, say, the living room or central hallway.
We close off all three BR vents directing the total output of the furnace to the Kitchen, LR, Dining Room, Hall and Baths. Seems to me that its going to more quickly bring the area where the thermostat is located up to temperature and then shut down. This, I think, would be especially true if the BR doors were also closed during this period.
Giant savings? Likely not, but if you're not heating a third (?) or half (?) the house, how can there not be some savings realized?
It's not that unusual to adjust temps differently in different areas. In our case, we have a combo of electric baseboard heat and ducted central air. We built in 1974 and, believe it or not, the next time the heat is turned on our bedroom will be the first time (other than an initial test to ensure it was properly wired and working). We like it cold for sleeping. Winter time it's rarely above 55 degrees in there provided we don't close the bedroom door.
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On Wednesday, January 27, 2016 at 8:13:12 AM UTC-5, snipped-for-privacy@snyder.on.ca wrot e:

ff vents

Heating

hutting

rn

d rooms

ounted

No ducts

and

The question though is whether the blower motor is oversized.
I'm more familiar with commercial than residential. In commercial, vents a re often adjusted to balance air flow to the different areas. Some might b e fully open but most probably partial. Of course in commercial the blower is usually adjustable too.
At any rate, I'm not so sure closing a few vents adds enough restriction to the system to affect airflow. A dirty filter blocks the only place air sh ould be going through, but the supply has lots of outlets. Unless the blow er is barely keeping up, closing a few vents probably just slightly increas es flow in the others, and the thermostat maybe satisfies faster.
In the rooms you are not heating, the temperature differential between outs ide and in will be smaller, so you will lose less heat overall.
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On 1/27/2016 8:13 AM, snipped-for-privacy@snyder.on.ca wrote:

So, if the air leaking out of the back bedroom is colder since the vent is closed, you still need to put the same ammount of heat into the house?
--
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Christopher A. Young
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On Wednesday, January 27, 2016 at 7:50:07 AM UTC-6, Stormin Mormon wrote:

If the heat vent is closed and the cold air return is not blocked...there will be negative air pressure in that room that will draw in some warm air. How much would be the question...
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On Wednesday, January 27, 2016 at 8:57:51 AM UTC-5, bob_villain wrote:

I think that the comment related to the cold air return is key. If the cold air return is not blocked, then the cold air from that room will lower the overall return air, requiring the furnace to heat it back up. It will also cause warm air from the rest of the house to be drawn in under the door, assuming that is the largest "leak" into the room.
In the one room that I have closed off, I also crafted cold air return covers from foam pads and then placed a heavy box in front to hold it in place. This allows me easily remove the vent covers when I want to heat the room. The room is above an unheated garage and gets pretty cold. I wouldn't want all that cold air sucked back into the furnace.
http://www.harborfreight.com/4-piece-anti-fatigue-foam-mat-set-94635.html
(I love those pads. My list of uses for them just keeps growing and growing.)
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On 1/27/2016 8:06 AM, Arnie Goetchius wrote:

Colder rooms means less heat loss. Which means money savings on heat.
That's my simple minded view.
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On Wed, 27 Jan 2016 08:06:30 -0500, Arnie Goetchius

It'll save money. The contractor is selling a mini-split system. Don't be fooled.
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On 1/27/2016 9:16 AM, Vic Smith wrote:

But I can save $20 a year if I buy a $2000 mini-split. And more important, Al Gore will have more fuel for his private jet.
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On Wednesday, January 27, 2016 at 8:06:27 AM UTC-5, Arnie Goetchius wrote:

As others have said, you can save money by closing of a room or two. However, if you close the output vents, you should also block the cold air return.
If the cold air return is not blocked, then the cold air from that room will lower the overall return air, requiring the furnace to heat it back up. It will also cause warm air from the rest of the house to be drawn in under the door, assuming that is the largest "leak" into the room. If it doesn't come in under the door, it's going to come in from someplace, which might be from the outside.
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On Wed, 27 Jan 2016 08:06:30 -0500, Arnie Goetchius

No. It restricts airflow to some rooms but not to others. That is different. Here's a hint, Any time *any* one uses the adverb "simply", he's probably trying to buffalo you. Either he doesn't understand himself or he's trying to trick you. It took reading thousands of usenet posts to notiice this fact.
The things that are really simple you generally don't need to have explained to you and when you hear a simple explanation, it is obviously true on its face. When people say "simply" (and a synonym I forget) they are almost never talking about something simple.

Hopefully, they have been sized accordingly.

If there is already leakage, an increase in pressure of 20% would increase leakage by 20%. That's still only a little bit in most cases.

Yeah, but to do all that you have to buy whole new systems, his plural, not mine. That many more electroniccs and pressure systems to go bad. IIUC, the labor to replace a condensor etc. for a small system is as much or almost as much as for a whole-house system, and with 2 or 3 (or 4) systems, after the first few years, something will be breaking all the time.

I think it will save money, especially if those rooms have outside walls, as I'm sure the bedrooms do. More later.
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On 1/27/2016 10:23 AM, Micky wrote:

You know, I'd never really put the thought into words, but this sure does make sense. I'll let you know if I pick up on the synonym for simply.
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Christopher A. Young
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On 1/27/2016 9:48 AM, Stormin Mormon wrote:

That's simple. Bullshit!
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On Wed, 27 Jan 2016 10:48:16 -0500, Stormin Mormon

There was one particular guy in one particular newsgroup who was always proclaiming false things, and he always used the word "simply". But after I noticed it with him, I saw the same thing with others, even if not as often.
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On 1/27/2016 1:51 PM, Micky wrote:

Hmm. That's simply a great thing to notice.
Ha, ha. Not funny, Chris. On the same vein, a man who says "you can trust me" isn't to be trusted. DAMHIKT. Honestly, that's what I find.
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Christopher A. Young
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On Wed, 27 Jan 2016 14:59:22 -0500, Stormin Mormon

I think you're right.
Not too many people have said that to me, and few on Usenet!
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<stuff snipped>

That's "basically" true. (-: (the other weasel word I know of)
--
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