Should You Close Register Vents in Unused Rooms?

I got called to a house last week and the Homeowner was concerned they were using way to much energy and they couldn’t heat and cool the rooms properly. Their solution was to close of the register vents in the rooms that weren’t used or the bedrooms that got to cold.

This is a common solution and see it all the time. I even did this in homes before thinking I could control the air flow. Heck, the damn things wouldn’t have the adjusters on them if they weren’t supposed to be shut, right?

Wrong, these should never be shut. Now that we have better building science and can test the pressures inside and out of the duct system we know that shutting the vents causes massive pressure to build up throughout the system. This negatively effects the system in a few ways-

1. It puts a lot of strain on the equipment itself. The blower starts to work harder to push the air through the system and can cause it to strain. This will shorten the life and cost you money.

2. It can freeze the coils quickly. This in turn puts strain on the outside unit and can lead to it malfunctioning. Again, costing you big time with costly repairs or replacement,

3. The increased pressure keeps the air from flowing correctly through the duct system. Air movement through ducts is actually very controlled and counts on a certain pressure to ensure the right air goes to the right duct. Closing off the vent does keep air from flowing into that duct but then makes it virtually impossible for the air to flow correctly through the rest of the system. Now to much or too little of air is getting into the rooms you still want to cool and the uneven air temperatures become noticeable.

I had to recommend that the client open all his register vents. Even though the urge is strong to shut the vents don’t do it, the answer always lies somewhere else. Let us test your home to determine what the real problem is and how you can solve it without damaging your AC equipment.

If you have any questions about air sealing insulation in your home or your client's please call us at (512) 584-4604 or email at stephen@ecadspecialist.com.