Attic Intake Vents

As the hot air leaves or diminishes, cool air moves in to replace it, creating a balance. That's ideal ventilation.

Ridge Vents

A ridge vent runs the entire length of the roof peak, blending into the roofline for a more attractive home. Years of research prove that a ridge vent with external baffles and an internal weather filter, combined with undereave venting, is the most efficient system you can install.

Ridge Vent Benefits:

• Works year-round
• Provides evenly distributed ventilation along the entire underside of the roof
• 18 square inches of net free area per linear foot
• Slim design, visual appeal
• Provides a higher volume of airflow per square foot of attic area than any other fixed-vent system
• Design maximizes airflow across the entire underside of roof sheathing
• Changes in wind direction have no significant effect on vent performance

Design Considerations:

• Ridge vents must have an external baffle to deflect weather away from the attic and to create low pressure over the vent openings to help pull air out of the attic
• May not provide enough ventilation area on steep hip roofs
• With all roofs, install ridge vents along the entire length of ridge for best performance and appearance. (With vaulted or cathedral ceilings: Each attic [joist] cavity must be ventilated, leaving 1-1/2" between sheathing and insulation.)
• Intake vents must be installed to provide proper airflow

Power Vents

With balanced motor and blade design, power vents quickly exhaust heat or humidity from any attic. They work on a thermostat, which automatically turns the fan on when cooling is needed. Some models also have an extra feature called a humidistat that monitors the moisture level of the air.

Benefits:

• One power attic ventilator is usually sufficient, unless it's a very large attic
• Roof-mount power vents are ideal for hip roofs
• Feature a preset adjustable thermostat for maximum homeowner convenience
• Gable-mounted power vents are an excellent option for tile roof ventilation

Design Considerations:

• Most power attic ventilators only have a thermostat, so they only monitor the heat in the attic. Moisture buildup is also a problem in the attic. A solution is a power attic ventilator featuring a combination thermostat/humidistat.
• For proper attic ventilation, the Home Ventilation Institute recommends a system that provides at least 10 air exchanges an hour. To determine the fan capacity needed to provide this minimum airflow, use the following formula: attic square feet x 0.7 = CFM (cubic feet of air moved per minute).
• Power vents are rated by CFM. Look for a power vent that provides at least the minimum CFM requirement. Remember, the higher the CFM the more air exchanges per hour.
• Note: for roofs 7/12 or higher, you may want to add 20% more CFM capacity to handle the larger volume of attic space; 30% more for roofs 11/12 and higher
• Keep in mind that there are energy costs associated with operating a power attic ventilator
• Adequate soffit venting must be installed for best performance
• If using gable vents, gable vents must be installed on the down-wind end of the home

Static Vents

Static vents (roof louvers, wall louvers and wind turbines) are inexpensive and popular with professional roofing contractors.

Design Considerations:

• According to federal guidelines, homes require 1 square foot of net free area (the total unobstructed area through which air can enter or exhaust a non-powered vent) for every 150 square feet of attic floor space. If balanced between intake and exhaust vents, the requirement is 1 square foot of net free area for every 300 square feet of attic floor space.
• Multiple roof vents are usually needed to provide the required net free area
• Must be spaced equally over roof to provide sufficient airflow along the entire roof sheathing