How To Ventilate a Basement

Without proper ventilation, most basements smell musty. Very poor basement ventilation may lead to health problems. These basement ventilation solutions will eliminate the smell and make the basement more comfortable and safer.

How To Ventilate a Basement

Why Is Basement Ventilation Important

Most basements are cool, damp, and smell bad. Lack of fresh air, leaks, and condensation are the main reasons. Proper ventilation helps prevent many problems.

  • Odor. Unpleasant musty moldy stale air smell.
  • Humidity. Basement humidity should be less than 60% to deter mold growth. Ventilation moves humid air out.
  • Mold. Humid, wet, and damp basements invite mold growth and promote rot.
  • Carbon Monoxide. Proper ventilation helps prevent carbon monoxide build-up.
  • Radon. In certain locations, radon gas will build up without ventilation.
  • Damage. Moisture attracts pests like rodents and insects that can damage furniture, flooring, framing, and basement contents.

Mold, carbon monoxide, and radon can cause serious adverse health effects.

9 Ways To Ventilate a Basement

Basements can be ventilated by passive or mechanical means. Sometimes both work together.

1. Open the Windows

Open at least two windows as often as possible to allow cross-ventilation. Consider replacing windows without screens or windows that don’t open. Installing a basement egress window increases safety and the larger window lets in more air.

2. Plug In a Fan

The wind does not always blow hard enough to move air through the basement. Setting up an inexpensive box fan close to an open window to bring in fresh air and move out stale air is a good option. For under $50.00 and less than $0.02 per operating hour, some fans will move up to 2000 cubic feet per minute (CFM).

3. Install Bathroom Fans

Install a bathroom fan in the basement ceiling and vent it outside–even if there is no bathroom. It will exchange a lot of air–especially with open windows. A bathroom fan costing less than $100.00 can exhaust over 100 CFM. Leave it on continuously or use a timer switch.

5. Buy a Dehumidifier

According to the EPA, maintaining basement humidity under 60% inhibits mold and mildew growth. Buy a machine that will dehumidify the entire basement. If possible, arrange for an auto-drain unit that empties into the sump to eliminate the hassle of emptying the reservoir. Most portable dehumidifiers remove 30 – 70 pints of water every 24 hours.

5. Keep the Basement Dry and Clean

Basement waterproofing is an important part of successful ventilation. Water leaking into the basement or crawl space keeps the space humid. Even a good ventilation system and dehumidifier have trouble keeping up.

Cardboard boxes and fabric absorb moisture; then release it into the air as basement humidity drops. Disorganized cluttered basements disrupt airflow–especially from corners and floors where it is needed most. Clean organized basements make it easier to spot mold and pest problems early.

6. Air Purifiers

Portable air purifiers clean and recirculate basement air–removing odors. If a window is left open they will mix the fresh air with stale basement air and improve ventilation. Starting at around $50.00, air purifiers are an inexpensive way to improve the smell of basement air.

7. Air-To-Air Heat Exchanger

Also known as a Heat Recovery Ventilator (HRV), air-to-air heat exchangers exhaust warm moist air out of the house and bring in fresh air. The warm air heats the incoming cool air–retaining up to 85% of the heat.

Moving parts in exchangers are two small fans that can run constantly and use very little power. HVRs remove radon and can be used as an auxiliary heat source in northern climates.

8. Air Conditioner

Air conditioners pump warm humid air out of windows. They are only a viable option in hotter climates where even basements can be too warm. Window-mount air conditioners and portables using exhaust hoses perform the same function of removing stale humid air from basements.


Many HVAC systems are designed to provide comfort to the main living areas–leaving basements under-served. Consider extending and upgrading existing HVAC systems to include the basement.