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Indoor Air Quality - Bathroom Remodel


Good ventilation protects both your health and your home.

Ventilation is especially important in bathrooms to remove unwanted moisture. This helps prevent the growth of mold and mildew, which can cause allergic reactions and aggravate lung diseases such as asthma. During renovation, be sure to check that your bathroom fan is functioning properly. This means not only that the motor makes noise or that the fan is running; it needs to be exhausting a sufficient amount of air*. And the air should be exhausted directly to the outside, and not just into an attic or some other space in the house.

For information on how to determine if your fan is working properly see the Homeowner's Guide to Ventilation, published by the New York State Energy Research and Development Authority (NYSERDA)

Sufficient amounts of Air:

For bathrooms, ASHRAE 62.99 recommends that you exhaust 25 cubic feet per minute (cfm) with a continuously operating fan, or 50 cfm with a fan that you turn on and off as needed.

Note: You may wish incorporate a bath fan into your overall ventilation strategy.

If you do not have a bathroom exhaust fan or if your current fan is not working, you should install one

ENERGY STAR® has finalized the ventilation fan specification.

In cold climates, bathroom exhaust fans can be used as part of a strategy to provide ventilation for the whole house. See the NYSERDA ventilation guide for more information.

Water Management

It should be obvious that all efforts should be made to avoid problems with water in the bathroom. Leaks should be fixed. Condensation problems should be addressed. Wet walls should be constructed to effectively keep water from penetrating cavities in the walls and floor.

Air-sealing Opportunities

Despite good ventilation, moisture-laden air from the bathroom can still make it's way into wall and ceiling cavities. A bathroom remodeling project may present opportunity to improve air-sealing. Electrical, plumbing, and ventilation penetrations should be sealed where they are accessible or in any walls that are opened. Depending on how they were constructed, soffits can be troublesome to air-seal, but if you are replacing bath fixtures or cabinets, you may be able to access space that would otherwise be difficult to reach.


Flooring must not only have a good degree of protection from harm by water, but should also prevent water which does get on the floor from penetrating to the sub-floor and space below.

Do not install carpet near water sources or areas where there is a perpetual moisture problem such as around sinks, tubs, showers, and toilets. To reduce the potential for microbial growth in the joints of hard surfaces or porous flooring installed near water sources, be sure to seal the entire surface.


Bathroom remodeling may present a good opportunity to replace old windows with new ENERGY STAR® windows. While costs do not always justify the change from purely an energy savings perspective, there may be other benefits of new windows. More efficient windows may be less prone to condensation and related mold growth. Painted window sashes and frames in homes built before 1978 may contain lead-based paint; this is a special concern because the friction of opening and closing windows can release lead dust into the home.

General Recommendations

While remodeling or improving the energy efficiency of your home, steps should be taken to minimize pollution from sources inside the home. In addition, residents should be alert to signs of inadequate ventilation, such as stuffy air, moisture condensation on cold surfaces, or mold and mildew growth and use the remodeling project to correct underlying problems. While all of our general recommendations may not apply to your home, you should be aware of the issues, from radon and lead, to ventilation, and good work practices.