Have you ever wondered if you could redirect the airflow in your home simply by closing vents? We put this DIY technique to the test, experimenting with how adjusting your vents can influence the comfort and efficiency of your home.
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Do not close your vents or registers in one part of the house to redirect cool or warm air to another part of the house. Just about any HVAC technician you talk to is gonna tell you exactly that.
Never close the vents off in your house. The answer is no, completely closing vents is a bad idea. Closing vents is not a good idea.
Several technicians that I’ve spoken with say that it might not matter as much as other people say. In order to find out, I did a deep dive into this topic to find out if it matters if you close a bunch of these in this video, we’re also going to test exactly what happens when you close several of your vents, and find out if that’s going to cost you money now or in the long run.
Here’s the problem we’re trying to solve: it’s usually one of two scenarios. You’ve got that one room or that portion of your house where, in the summer, it’s always too warm, and in the winter, it’s always too cold. Not enough air gets to the vent down there, so it just doesn’t keep up.
Or the other scenario is you’re trying to adjust the temperature on one floor versus another because of the same thing, maybe the upstairs is always hot in the summer, and the basement is always freezing in the winter.
So the typical thing that we’re going to try is to close all of the vents on one floor to redirect heat or cold to the other floor. Hopefully, we’ll be able to balance this out. And that’s exactly what this problem is called. This is called an unbalanced system. It’s pretty common, and it’s usually the result of someone not properly planning out the ductwork and the system for your HVAC in your house.
Why Technicians Claim You Should Not Close Your Vents
1. It Will Increase Static Pressure
Most technicians are going to tell you not to close your registers or vents for two main reasons. The first and most important one is that it will increase the static pressure in your system. Static pressure is when there’s enough resistance somewhere in your system. If that static pressure increases, it takes its toll on the blower fan. Down here, the blower fan is what generates all of the air that gets pushed through your house. So it takes all of that air that’s coming in from your returns, and it pushes it through either some air conditioning or a heater, the furnace part, and then blows it out your vents. Now, if that part goes out, nothing works. So the claim is that by having that increase in static pressure that is supposedly caused by closing your vents, you’re going to shorten the life of your blower fan, and therefore shorten the life of your unit and your system, and everything that comes along with that.
Down here, the blower fan is what generates all of the air that gets pushed through your house. So it takes all of that air that’s coming in from your returns, and it pushes it through either some air conditioning or a heater, the furnace part, and then blows it out your vents. Now, if that part goes out, nothing works.
So the claim is that by having that increase in static pressure that is supposedly caused by closing your vents, you’re going to shorten the life of your blower fan, and therefore shorten the life of your unit and your system, and everything that comes along with that.
2. It Can Cause Whistling
The second reason not to close your vents is because of whistling, and this is a real one, regardless of what any technicians say or don’t say. You may have experienced this yourself. If you close the vent down, it’s never going to seal it completely, and you’ve got a large amount of air trying to come through. It gets blocked, and so it’s forcing itself out through the little opening that you have in that vent. And that can cause whistling.
Solutions for an Unbalanced System
1. Redesign/Reconstruct your Ductwork
As far as solutions for the problem of an unbalanced system, there are a couple of things to look at. The proper way to do this is to redesign and reconstruct your ductwork. This is a costly process, it’s very involved, and it’s something that most people aren’t going to be able to do.
2. Install Dampers
Another option is to install dampers. Dampers are an open or closed valve that you can are kind of like a spigot or a faucet for plumbing. This allows you to turn the flow of air off or on, or adjust it partway. Unfortunately, this is not an option for a lot of homes. A lot of our lines are connected to the same branches. That means that you can’t actually cut off the air to the upstairs without cutting off the air to the downstairs as well.
3. Install Local Cooling and Heating
There is a third option, which is to install some local heating or cooling in the specific areas that are a problem. You can put a window unit air conditioner in, for example, or a space heater. You can even install a mini split, and I’ve done several videos on installing those. They help to balance the space, even though that’s a lot of work, and it’s something that’s not super easy and that you can do in an afternoon; it makes a huge difference in conditioning a certain space in your house.
Static Pressure Buildup….time to put it to the test.
As far as the static pressure is concerned, I’m going to put this to the test. I’m going to open all of the registers or vents in this house and get a reading on what the static pressure is. Then I’ll close one floor and see what that does to it. I’ll try closing the other floor to see if that makes any difference, because my suspicion is that it won’t. This is called a manometer, and if it’s not zeroed out, like mine is, you want to make sure that you zero it out for the pressure in this room. These two probes determine the static pressure that we need to test here.
First, we need to understand what’s in our system. On top, we have the evaporator. This is basically the part, the internal part of your air conditioning system. So this is what makes your air cold and pushes it up from there. Down here, below this, we have the furnace portion.
Below this, we have the furnace portion. We’ve got our burners lined up along here.
On the bottom, we’ve got the blower fan. Then to the left, our filter, the first probe needs to go after the filter, so in here, and it needs to go near the blower fan. And conveniently, we already have a hole right here on the side that we can use for this, so I don’t have to drill a separate hole in here. I can just put it right in here, and that’ll work.
The second probe needs to go before the evaporator and after the burners, or as close to them as possible. I’m going to drill a hole here in this back section. To do that, I’m going to use a step drill bit. This step drill bit allows me to do a little bit at a time. I want it barely big enough to fit one of these probes inside of it.
It only takes a second, and it might be scary to put this in here, but it’s not a big deal, because you can cover it and patch it up. There’s our first one, and then I’m going to need to go one more.
I’ll see if that’s big enough for the probes.
There is a little bit of insulation, so I’m going to grab another drill bit and just clear out that little spot of insulation, and then we’ll be able to insert the probe. Now that we’ve got our covers placed back on, I’m going to place one of the ports here into the top section in the hole that we drilled earlier.
And the second one I can put right down here, so that’s pointing downwards as well.
I’ll use my thermostat to turn on the heat, so we should have full force coming in. The fans will turn on. Our burners are engaging right now, so with the probes in place, I am ready to test the static pressure, both in the first port and in the second port. Then I’ll find out the difference now here. Once this turns on, I’ve got the burners going, and the blower fan will kick on in a second.
This is measured in inches of water column. It’s a weird unit that it uses, but that’s what it uses. And this furnace, along with others, specifies that you want to be at 0.5 or lower. To get that 0.5, we’re going to find out what this is and what that is, add them together, and they should come out to less than 0.5. In an ideal situation, the negatives don’t matter. In this case, we’re just looking for basically, you can make them all positive, and we’ll add them together, and the difference will show that.
We’ve got 0.3 down here, up top, p2 is around 0.26 to 0.27. If we see the difference, we’re sitting around 0.57 or so. So this is a little over one-half inch of water column, so it’s a little higher than we want it to be, but not bad. Honestly, something in that range is pretty typical and pretty decent. It doesn’t indicate a huge problem.
Now that we have kind of a baseline established, I’m going to close all of the vents on one floor. We have a Rambler-style home. I will close half of the vents in the house and see what that does to our static pressure. It is now at 0.65, and this has been sitting around 0.634. Hardly any more than it was when we had everything all the way open.
Now I’ll put it back to where all the vents are closed upstairs, and the basement has all of the vents open. The heat is going because it’s very cold outside, and that seems to be doing just about nothing to the static pressure, 0.62. Now they’re all closed, and it’s barely gone up a little bit more. So we’re at .68. Maybe it’s touched point seven before, so barely moving up. The static pressure overall is not affected, at least in this house, by registers or vents being closed. The myth that you can’t close your vents is busted!
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