Is Closing Vents in Unused Rooms Okay?

Everyone likes to save money on an energy bill, but you may not want to sacrifice comfort by running your AC unit less. You may wonder whether closing vents in unused rooms would reduce energy costs. The reality is that it won’t save you money. The HVAC system still moves the same amount of air through the ducts, regardless of which vents are open or closed. Instead, you may end up with high humidity in the unused rooms and other costly problems. Learn why, in most cases, closing vents in unused rooms is not a good idea.

Benefit of Closing Vents in Unused Rooms

Ultimately, closing vents in unused rooms doesn’t save money on energy bills and could have multiple negative effects. However, one circumstance exists where closing vents in unused rooms could benefit your energy bill.

If you use baseboards or radiators for your heating in individual rooms, the heated air doesn’t need to travel through the ductwork that the central air conditioner uses. During winter time, you could close the vents—especially ceiling vents—to keep warm air from flowing out of the room and into the ductwork. However, you’ll want to open the vents again before you begin using the AC the following spring.

Issues With Fully or Partially Closing AC Vents

Here are some problems you could experience when closing vents in unused rooms.

Leaks in the Ducts

The contractor who installed your HVAC unit’s ductwork aimed to create the proper balance between the air pressure that the system generates and the number of vents you have. If you start closing multiple vents in unused rooms, extra air pressure builds up in the ducts. This could cause a weak section to begin leaking or could widen an existing gap.

If leaks become prominent in the ducts, you could see your energy bills actually increase because you’re inadvertently heating and cooling crawl spaces and attics.

Damage to the HVAC Unit

If enough air pressure builds up in the HVAC system and ductwork, you could end up with damage in the heat exchanger or in other sections of the HVAC unit. In addition to having repair costs, you could end up shortening the life of the system.

In the worst-case scenario, a cracked heat exchanger could release carbon monoxide into the home, putting your household at risk.

Inefficient HVAC Operation

Closing vents doesn’t save energy because it doesn’t cause the HVAC to run slower or generate less air pressure. Your HVAC system doesn’t adjust its operation based on the number of closed vents in unused rooms or elsewhere in the home. It always generates the same level of airflow because installers select an HVAC system airflow capacity based on the size of your home. 

High Humidity

One of the best reasons to leave vents open in unused rooms is to keep humidity at acceptable levels. Running air conditioning lowers humidity inside your home. Allowing excess humidity to build up inside a room could cause things like mold particles and dust mites to accumulate. These items can cause respiratory problems. You may even draw insects, like cockroaches, to the rooms with excess moisture.

The Environmental Protection Agency recommends keeping indoor humidity levels at 30% to 50%. You should never exceed 60%. Keeping vents open and running air conditioning throughout your home will deliver steady humidity levels.

Costs to Repair Ducts and HVAC Systems

Even if closing vents in unused rooms actually reduced your energy bill, the costs to repair the damage that could occur would almost certainly wipe out your savings. If you have been fully or partially closing air vents, learn about some of the repair costs you could incur.

Duct Cleaning Costs

Closing vents may encourage mold growth inside the ducts because of additional humidity. You may also have uneven air flow through a few ducts, resulting in a buildup of dust or other particles. The average cost for cleaning air ducts ranges from about $260 to $500 when you hire a local air duct cleaning company.

Ductwork Repair or Replacement Costs

The buildup of air pressure inside your ductwork when you close vents in unused rooms could cause gaps to form in the ducts. You may have to repair or replace your ductwork to fix this issue. The cost to replace ductwork can range from $450 to $2,200, depending on the size of the home and the amount of ductwork involved. A local duct installer can give you an estimate and advice on whether to repair or replace. 

HVAC Repair Costs

Closing and blocking vents in unused rooms could eventually damage your HVAC system. A local HVAC repair company can give you an estimate on the HVAC system repair cost, which could range from $130 to $2,000. Should you suffer significant damage, the cost to replace an HVAC system ranges from $5,000 to $12,500.

Ultimately, it’s not worth testing whether blocking air vents can reduce energy bills because it could cause expensive damage.