Closing HVAC vents

[JohnT]

I've already done a web search and came up with conflicting information so thought I'd see what some of you think. Here's the deal. I have a 10x10' room in my home that is used for storage. I'm thinking about closing the HVAC vent and door because it seems like a waste to cool and heat the room when it really doesn't need it. Some advice says to do it; others say don't due to causing an imbalance in the system. What say you?

[KJ Smith]

Don't do it.

Two reasons.

1. Humidity, you will lose all control. Not as big a deal there as it is here.

2. What will happen, the room you close off will eventually warm up to the outside temp.

Then instead of having an insulated wall stopping the temperature exchange, you will have 2 or 3 non insulated interior walls passing the hot/cold air into your house.


Make sense?

[texkam]

The way I understand it it all about air flow, for every vent you close you restrict some of the air flow through your system putting strain on your blower (a dirty filter will have the same effect). Obviously if all vents but one were closed the blower would have to push all the air through that one vent, not very good on the blower motor. How much effect closing 1 or 2 will have, I don't know.

[KJ Smith]

Actually, closing off the airflow lowers the amount of work the motor can do. Therefore it lowers the amperage used. It does no harm to the blower whatsoever.

If you lowered the airflow enough, you could cause the evap coil to freeze up. That could ruin the valves in the compressor.

Now that would be very bad, but not that likely with just one vent closed.

[JohnT]

Kevin, yes, what you said makes sense and is in line with what other sources say. Thanks.

[KJ Smith]

Glad to help....

If you want to save energy, check your attic insulation. You can do yourself a lot of good.

In April I added 18+ inches to my poorly insulated 2000sq ft home.

It is very difficult to quantify the actual savings.

In real dollars I have spent ~$450.00 less this year.
But electricity was cheaper this year.

In consumption I spent ~$250 less this year.
But the average daily temperature was higher.

The actual savings is in between there somewhere.
A really good engineer could spend a lot of time figuring it out.

It cost ~$750 to insulate it myself. You can get a tax credit on that this year.

So end result is somewhere between a 2-3yr payback.
3 yr is the standard residential "yes its worth it" benchmark.

The other simple method is a setback thermostat. But there are interesting arguments against that.

I have one, but I use it to lower the temperature at night so I can sleep better...

[SCone]

When my Son moved out earlier this year I closed the bath room door and the door to his room and closed the two vents... AC bill for the summer never topped $300... when it was all open the AC would be $400+ in the heat... can't say whether it makes any difference to the AC system, but it sure did for my pocketbook

[KJ Smith]

Originally Posted by SCone

When my Son moved out.....

That was probably the biggest difference.

You are talking about 25% of your bill.

Also, as in my previous post, you probably paid less for electricity this year.

Sometimes stuff is hard to prove. I like using the consumption (kw's) used.

But that can be skewed by degree days.

[ST77]

I have had vents closed off and have for years with no noticeable temp problems in the rooms that dont have a vent going

[Rson]

Sunday i will see a Engineer that owns a HVAC company. I'll ask him.

[ggeen]

I found no noticeable difference. I live alone, in the same house, for 10 years. For about half the time, I closed off the guest room vents when not in use. The other half I have not bothered. There is no appreciable difference in energy usage from year-to-year in my live experiment.

As for the question of the air handler. No, you are not using less amperage by closing a vent. No, the air handler does not work less if a vent or two is closed. Close too many vents and the air handler will work too hard and burn out. Closing just one or two probably does not cause too much harm. I've done it.

[KJ Smith]

Originally Posted by ggeen

As for the question of the air handler. No, you are not using less amperage by closing a vent. No, the air handler does not work less if a vent or two is closed. Close too many vents and the air handler will work too hard and burn out.

What is your theory on this. Do you have any electro-mechanical experience.

A blower can only move so much air. If you shut vents, it can not move as much. Lowers the amps.

Same with a water pump, shut the head, lower the amps.

[KJ Smith]

Originally Posted by ggeen

I found no noticeable difference. I live alone, in the same house, for 10 years. For about half the time, I closed off the guest room vents when not in use. The other half I have not bothered. There is no appreciable difference in energy usage from year-to-year in my live experiment.

I overstated the room warming up.
It makes it easier to understand.

An air conditioner removes heat from the space.

So what happens, as the room warms, it gives up its heat through the non-insulated walls, into the conditioned space.

So it is entirely possible that the room is close in temperature.
You are just removing the heat in a less efficient way for that particular space.

But the fact that you are removing the heat is why there is no difference in energy usage.

[JohnT]

Originally Posted by Rson

Sunday i will see a Engineer that owns a HVAC company. I'll ask him.

Thanks. I look forward to hearing what he has to say.

[picman]

Before getting a new HVAC system, I trolled an HVAC forum. Something I noted there was that heat exchangers can crack from reduced air flow. The installers don't have much love for the high filtration 1" filters because of reduced flow. Your system might not be flowing enough air without closing vents or it might have plenty of flow. Having someone test it would be the only way to know for sure.