Ventilate for fresh air, comfort and humidity control

Ventilating your home for fresh air, comfort and humidity control

Key Benefits:

• Fresh Air Exchange
• Comfort – Wind Chill, Cooler Temperature,

Key Strategies

• cross ventilation
• air movement
• stack effect
• humidity control

It’s spring in Alabama and, now that pollen season is over, we can open our windows for some natural air conditioning. Ventilating your indoor living space will eliminate odors and other pollutants that have built up over the winter. You will achieve best results for comfort by taking advantage of two natural forces to move air through the house — cross ventilation and stack ventilation.

The benefit of these natural forces is they keep the air moving and a slight breeze is more comfortable than stagnant air. During spring and fall, you will save money by running your air conditioner and fans less. As days get warmer and more humid, natural ventilation becomes less effective and you should rely on ceiling fans to keep air circulating inside the home.

Cross ventilation — Getting good air flow with natural ventilation is easy if there’s a breeze outside. Just open windows on two sides of the home or apartment so the air has a path to flow in and out.

You can manage natural cross-ventilation by opening your windows and doors, and adjusting the size and location of the openings to ventilate different parts of the home. Inlets and outlets located directly opposite each other cool only those areas in between, in the direct path of the airflow. You’ll cool more of your home if you force the air to take a longer path between the inlet and outlet. Use smaller window openings for the inlets and larger openings for the outlets. This increases air speed and improves the cooling effect.

Air from cooler, shaded outdoor areas provides the best intake air. Experiment with different patterns of window venting to move fresh outside air through all the living areas of your home. This may involve leaving some windows closed if they interfere with air moving along a longer path through the home.

What if there is no breeze?

Stack Ventilation – You can induce natural air movement if the residence is more than one story by opening a high- window and a low window. This takes advantage of the chimney effect, which occurs when cool air enters a home on the first floor or basement, absorbs heat in the room, rises, and exits through upstairs windows. This creates a partial vacuum, which pulls more air in through lower-level windows.

Indoor Comfort Factors – Temperature, Humidity, Air Movement

Temperature isn’t the only factor that impacts your indoor comfort. Equally important as air temperature to comfort is air movement and humidity, so if natural ventilation isn’t providing all three, you may need to close the windows and manage temperature, humidity and air movement with your home’s central air conditioning system. Use your central cooling system to lower humidity indoors and ceiling fans to circulate  air in occupied rooms. Ceiling fans effectively create a comfort effect of about 4 degrees cooler. Turn off ceiling fans when leaving the room.

Remember the following if you plan to cool your home with ventilation:

• Learn how air flows naturally through your home.
• Take advantage of cool night air, and ventilate your home by natural or mechanical methods.
• Keep a clear path for airflow both inside and outside your windows.
• Close windows, doors, and window coverings in the morning before your home starts to heat up.
• Avoid producing heat in your home when it’s hot outside.
• Wear cool clothing.
• Raise your air-conditioning thermostat to a more economical temperature.
• Use ceiling fans with both air-conditioning and natural ventilation for added cooling effect.

Source: National Renewable Energy Lab (NREL) http://www.nrel.gov/docs/fy01osti/29513.pdf