Your Guide To Attic Ventilation
Your Guide to Attic Ventilation
Attic ventilation is very important to home owners for two reasons: temperature and moisture control. Temperature control is extremely important because during summer months, hot air that is produced in the house thanks to solar energy can build up and store itself in the attic, which leads to higher energy consumption in the attempt to cool the attic. By having a sufficient attic ventilation system, the ambient temperature in this area of the house will remain lower and will not force the air conditioning system to worker harder trying to lower the temperature in the attic. The second important reason for a proper attic ventilation system is moisture control. Moisture, like temperature, can also build up in the attic. If this moisture is allowed to build up, it can condense in this area and the moisture can lead to the deterioration of building materials such as insulation. A vapor barrier installation can help to avoid this build-up, thus aiding with ventilation.
The first thing to determine when considering attic ventilation is the amount of air that needs to be moved out in order to achieve the desired results. In a recent study it was determined that the proper ventilation to lower ambient air temperatures in the summer is more than sufficient to reduce the moisture build-up in the winter months. The amount of ventilation required for winter months is only about one-tenth the amount required to reduce the temperature in the summer months. Even though temperatures in the air outside may only reach 95 o -97o F, the air temperature in the attic can reach up to 160 o F. By having an air exchange of one change per minute will reduce temperatures to a mere 101 o F which will greatly reduce the energy consumption required to cool the house. One important factor in this matter is the ceiling insulation.
Houses with poor ceiling ventilation can have 30 or more percent of their cooling costs being used to cool the attic, whereas houses with better ceiling ventilation will only use and estimated 12-14 percent of the cooling costs. The definition of poorly insulated ceiling is where the “R” rating of the insulation is less than 14, or that there is less than 4 inches of insulating material.
The proper and most energy efficient way of ventilating attics is the natural ventilation method. This method of ventilation does not require any type of mechanical system and works solely on the principles of physics. As air is heated it becomes less dense and wants to rise. Wind that blows across the roof will also cause areas of high and low pressure. The basic principle, then, is to have inlets for air sweeping across the roof in lower areas with the outlets for the air inside the attic to be at higher points. For example, the outlet would be closest to the peak of the roof and the inlets would be closer to the edge of the house where the roof is lower. The greater the vertical distance between the inlets and outlets, the greater the ventilation rate will be.
Whenever it's time to evaluate energy efficiency in your house, the place to stop is at the top: Make sure your attic ventilation is adequate to get the job done.
