How do I calculate attic ventilation for whole house fan?
How do I calculate attic ventilation for whole house fan?
You need a minimum of 1 square foot of attic air venting for each 750 CFM of air flow. If you need 6,000 CFM of air flow through your house, divide 6,000 by 750 to get a minimum 8 square feet of attic venting. That translates to one attic vent 3 feet by 3 feet, or two attic vents, each 1 ½ feet by 1 ½ feet.
How much venting is required for a whole house fan?
Venting Requirements A rule of thumb is that you should have one square foot of “net free venting area” for every 750 CFM of airflow. So at 3000 CFM, you’ll want four square feet of venting. Most modern homes easily accommodate this rule, but it is important to check to ensure optimum system efficiency.
What is code for attic ventilation?
The minimum amount of attic ventilation remains 1/150 (1 square foot of Net Free Area for every 150 square feet of attic floor space. Attic floor is defined as length x width FLOOR of the attic). The amount of ventilation can be reduced to 1/300 (in effect 50% less) BUT 2 conditions must be met effective 1.1. 18.
What size attic fan would an electrician need for a 1500 square foot home?
Attic fan size chart for quick reference
| Attic floor area | Recommended attic fan size |
|---|---|
| 1000 sq.ft | 700 CFM |
| 1500 sq.ft | 1050 CFM |
| 2000 sq.ft | 1400 CFM |
| 2500 sq.ft | 1750 CFM |
Can you use a whole house fan with a ridge vent?
If you have a home with a ridge vent… the type of vent that runs along the peak of the roof, you don’t even have to measure. A 40ft long ridge vent is equivalent to 20 sq. feet of gable vent… more than enough venting for even the largest whole house fans.
Does a whole house fan vent outside?
The whole house fan then draws cool air from outside in through open windows/doors, and pushes the hot air from inside the house outside through existing vents on the roof, effectively cooling your home.
How do you test attic ventilation?
How to determine whether you need better attic ventilation
- Look at your eaves and roof.
- Touch your ceiling on a warm, sunny day.
- Thick ridges of ice on your eaves in winter are a sign of poor attic ventilation.
- Warm air that escapes living space also carries moisture that will condense on rafters or roof sheathing.
Can you over ventilate an attic?
It’s possible to have too much exhaust ventilation, but you cannot have too much intake ventilation. If there is more intake ventilation than the attic’s square footage requires, it’s not problematic because any excess intake converts to “exhaust” on the leeward side of the house.
How big of a gable vent do I need?
Typically you want a vent area of one square foot for every 300 square feet of attic space. When dividing, round up to the next whole number. In the example, you want 3 square feet of vent area.
How many CFM should my attic fan be?
Most manufacturers recommend sizing an attic fan at 2 to 3 CFM (cubic feet of air per minute) per square foot of living space.
Do you still need an attic fan when you have a ridge vent?
Combining an attic power vent fan with a ridge vent is usually not recommended because: It could reverse the natural flow of hot air out the ridge vent. If air is drawn in through the ridge vent while it’s raining, it might pull rainwater in with it, which could lead to leaking or mold in the attic.
How much ventilation do I need for my whole house fan system?
Venting plays a huge part in how your QuietCool whole house fan system works to its full potential. You can only bring in as much air as you can discharge out of your attic vents. We always recommend at least having 1 SQFT of net free area venting for every 750 CFM in your system.
How much air can I bring in from my attic vent?
You can only bring in as much air as you can discharge out of your attic vents. We always recommend at least having 1 SQFT of net free area venting for every 750 CFM in your system. For example, if a customer installs a QuietCool Trident Pro 4.8 they are pulling in roughly 4,740 CFM. If you divide that by 750, you get the number, 6.32.
What size attic fan do I need for my home?
At its least obtrusive, an attic fan will fit within the attic and behind the gable opening’s vent. A whole house fan is located within the attic, but it must open into the home’s ceiling with a vent covering the opening. Whole house fans are the width of your ceiling’s joists and around 36- to 40-inches long.
How much CFM do I need for a ceiling fan?
Take The Total Cubic Feet Per Minute Of Air Flow (CFM) Of The Fan – And Divide By 750, 2. This Will Give You The Amount Of Net Free Venting In Square Feet Required For The Fan You Select. Rated At Approx. 2000 CFM. When Exhausted Directly Into The Attic: 2.7 Sq.
