An adequate attic ventilation system is meant no only to prevent condensation problems during the winter months, but from an energy-conservation point of view, it significantly reduces the heat load on the structure during the summer, so vents reduce cooling costs. Because of trapped air, attic areas can become excessively hot during the summer, reaching temperatures as high as 150°F. Moreover, if there is an air conditioning blower coil located in the attic, the high temperature will affect its efficiency of operation.
A properly ventilated attic should have at least two vent openings located so that air can flow in one opening and out of the other. Vents in the eaves and at gable ends are better than gable vents alone, but one of the most effective types of attic ventilation system involves a combination of vents in the eaves and a continuous ridge vent. Remember that the attic must be adequately ventilated during the winter as well, and as long as the attic is properly insulated, the benefits of ventilation far exceed any fuel savings that might result from blocking the vent openings.
Unfortunately, few people bother with the insulation or ventilation of their attics. However, poor ventilation may result in hundreds of dollars added to your utility bills. You can minimize your electricity and other utility bills through some simple ways, including attic insulation and ventilation requirements.
Attic Ventilation Requirements and Benefits
According to recent estimates, less than 10 percent of homes follow the norms of proper attic ventilation. The rest have poor or no attic insulation whatsoever. To ensure proper attic ventilation against various environmental parameters, here are some of the basic attic ventilation requirements:
- Heat
Hot air is less dense, therefore it has a tendency to move upwards. If there is no attic insulation, the air gets trapped in the attic, then moves to your living space and heats up your entire home. In the summertime, the temperature of the attic is about 155 to 160 degrees, while the outdoor temperature is just 105 degrees. The air conditioning system works according to the difference between the interior and exterior temperature. Consequently, a difference of about 50 degrees puts a considerable load on your air conditioner, forcing it to draw more power to keep working and maintain the optimum temperature in your home. It is essential to have vents located as high as possible in the attic, so that exchange of air takes place and the attic doesn’t get heat up.
- Moisture
Trapped moisture can significantly affect your roof and insulation. During the winter, the air condenses and without proper attic ventilation, the moisture gets trapped inside the attic. In addition, the moisture may creep into your attic insulation and soak it, making it completely useless. Trapped moisture also gets inside the wall and causes the paint to bubble, crack and peel, and it also causes tremendous damage to the roof, reducing its life by several years. Also, moisture promotes mold and mildew growth and can inflict lasting damage upon the entire structure.
- Rain and Snow
If you follow proper attic ventilation requirements, you will be able to avoid a lot of trouble and costly repairs. An improperly ventilated attic allows snow and rain to enter your house, because improperly designed vents do not pull sufficient air, and as a result a reverse effect occurs, pulling in rain and snow during storms. A properly ventilated attic will push out rain and snow and protect your home.
Moreover, an improperly ventilated attic aggravates the deterioration of roofing shingles and forces them to wear out at a much faster rate. And if your home is poorly ventilated, your shingle manufacturer might void his warranty.
How to Calculate Attic Ventilation Requirements
According to the U.S. Federal Housing Administration (FHA), for every 300 square feet of attic floor area you should have at least one square foot ventilation. For instance, in an attic that is 30 feet by 20 feet, you would have 600 square feet of floor area. Consequently, you would need two square feet of attic ventilation. The two square feet are divided equally between the intake and the exhaust, one square foot for each. To calculate your attic ventilation requirements, follow these simple instruction:
1. Calculate the square footage of the attic space: Length X width.
2. Divide the square footage (item 1) by 300: Result of item 1 ÷ 300.
3. Change the square feet to square inches: Result of item 2 x 144.
4. Divide the square inches by 2: Result of item 3 ÷ 2.
The result of item 4 is the minimum of square inch area needed for both the intake and the exhaust ventilation. An equal amount of intake and exhaust will make for the best ventilation system. Note that you should never have more exhaust area than intake area.