For many, proper ventilation is simply a way to maintain cooling comfort in the home during the hot summer months. While good ventilation is crucial to an economical and efficient home cooling system, the concepts of sound ventilation also go a long way toward providing a comfortable, , healthful environment throughout the year.
The need for proper ventilation year-round has never been more crucial than it is today. Thats because modern construction techniques have made homes virtually airtight. While this offers advantages in terms of heating and cooling, it also creates considerable problems. There is a need for a free exchange of air between the inside and the outside. Without it, moisture, heat, grease, smoke and other contaminants are trapped within the house where they are a year-round threat to the indoor environment.
During the winter months, in particular, homeowners tend to keep their homes closed up to keep heat in and cold out, which also keeps moisture and pollutants in, while shutting out fresh, clean air.
What is needed is a low-cost and effective way to maintain an even exchange of air between the inside and outside, and proper ventilation is the best way to achieve that goal.
In discussing proper home ventilation, two systems must be considered: the natural, or static, ventilation system.
The static ventilation system is simply a series of strategically placed mechanical vents. Simple though it may be, the static ventilation system is of enormous value within the home. Static vents facilitate the movement of air between the home and the outdoors, helping maintain a fresh indoor atmosphere. These vents are usually installed in openings in the attic space and must ne properly installed to take advantage of the natural flow of air.
There are five basic types of static vents. Ridge vents are designed to provide a continuous opening along the entire ridge line of a pitched roof, ridge vents prevent rain and snow from entering the attic, but allow for ongoing exchange of air between the attic and the outside. For maximum, efficiency, the ridge vent must be used with the undereave vents. Installed in the roof overhang on both sides of the house, the undereave vents serve as the intake areas, allowing fresh air to flow out through the ridge vent.
The other type of static vents are: triangular vents, those which are fitted to the high point of the gable ends of the house; rectangular vents, those which are placed slightly lower at the gable ends; the roof vents, those which are normally placed on the rear slope of the roof.
Regardless of which vents are used, the undereave vents are necessary to create a system in which air flows continuously from the attic to the outside. With this air flow, the homeowner helps to avoid the dangers which can occur in the attic from too much heat build-up in summer and too much moisture build-up in the winter.
Regardless of what type of static vents used, it is important for the homeowner to see that they remain open year-round. Some have closed vents during the winter months, thinking that this will help to retain heat within the home, saving energy. However, heat loss through static vents is negligible, and closing the vents actually hurts the indoor environment by stopping the necessary free flow of air between the inside and outside.
While static vents are crucial to proper ventilation, they may not provide the level of ventilation desired for indoor comfort and protection. For that reason, many homeowners chose to install turbine ventilators, while others elect to utilize powered attic space ventilators.
Turbine ventilators are wind-driven devices which are designed in such a manner that wind from any direction causes the upper portion of the ventilator to rotate. As the turbine rotates, or spins, a reduced air pressure in the stack draws hot or humid air from the attic space.
Working in conjunction with static vents, the powered attic ventilator offers a measure of protection and comfort that makes it a most worthwhile addition to the home.
In the winter, the powered attic ventilator can be equipped with a humidistat so that it turns on automatically to rid the attic of excessive moisture, Moisture produced throughout the house tend to rise and collect in the attic where it can be potentially more damaging than heat. The moisture can seriously hinder the effectiveness of insulation and can penetrate beams, rafters, roof sheathing, and other structural members, causing them to rot. The powered attic ventilator quickly gets rid of moisture, offering the homeowner needed protection.
Equipped with a thermostat, the powered attic ventilator turns on automatically during the summer to quickly rid the attic of excessive heat, which can burden the air conditioning system and pose a threat to building materials and insulation, accelerating their deterioration. The powered attic ventilator provides a most important service by expelling the extremely hot air before it causes difficulties.
To assure that your ventilation system function properly, it must be correctly sized. the Home Ventilating Institute (HVI), a division of the Air Movement and Control Association, offers simple formulas for computing the correct size of ventilators. First, you must determine the actual square footage of the attic. For static vents, there should be one square foot of vent area for every 150 square feet of attic square footage. For powered attic ventilators, multiply the attic square footage by .7. The result gives the proper capacity of the fan in terms of cubic feet per minute (CFM) of air moved. Attic ventilators manufactured by HVI members are independently tested and their certified CFM rating appears on the HVI label displayed on members products. It is the customers assurance that the product will perform at specified levels.
Proper ventilation in the bathroom is also of critical importance in providing a relatively trouble-free winter home environment. Thats because of the great amounts of airborne moisture which the bathroom produces.
Use of the shower creates a large amount of water vapor. In addition, it also leads to an increase of water vapor pressure. This means that the moisture in the air can be forced into the walls, cabinets, and other areas in the bathroom, causing rotting of wallboard or window framing and peeling paint. the moisture can also escape to other areas of the house, causing further damage. Compounding the problem, the bathroom generates pollutants such as heat, odors and aerosols.
The most efficient way to quickly rid the bathroom of these unwanted elements is with a bathroom exhaust fan which is ducted to the outside. Tests have shown ducted bathroom fans to be far more effective in cleansing the air than those fans which simply draw the air through a filter. An exhaust fan, mounted on the ceiling or wall and ducted outside, quietly and efficiently expels moisture and other pollutants before they can cause problems. In addition, the fan gets rid of heat, odors, and aerosol pollutants produced through bathroom use.
Again, HVI provides a formula for determining the correct size of a bathroom fan. Needed capacity of a bathroom can be determined by multiplying the floor area of the room by 1.1. The result provides the CFM rating of the fan necessary to adequately ventilate the bathroom.
One more area which must be considered in creating a ventilation system that meets winter needs is the kitchen. When it comes to indoor pollution, no room can match the kitchen for the wide variety of contaminants it produces.
It has been estimated that in the average home, the kitchen produces more than 200 pounds of airborne grease annually. Add to that smoke, heat, moisture and odors and its easy to see why the kitchen poses such a threat to the indoor environment. Soiled surfaces and a fouled atmosphere are the by-products of cooking activities.
There is an economical and effective way to assure that the kitchen environment stays fresh, clean and healthful. Modern range hoods expel all the pollutants produced by range usage before they can cause problems. Your kitchen may already be equipped with a range hood, but it may not offer the advantages or capabilities of the newer models. Range hood manufacturers have kept pace with the changing role of the kitchen as it has emerged as a major center of activity in the home. As a result, they have created range hoods that are more responsive to the increasing demands placed on the kitchen.
For the range hood to reach its maximum potential for cleansing the kitchen air, it must be properly selected and installed. HVI offers a simple formula for calculating the capacity for a range hood to effectively do its job. For range hoods situated against the wall, multiply the lineal footage of the range by 40; for island or peninsula installations, multiply the lineal footage of the range by 50. the result gives the correct CFM rating for the necessary range hood.
The Home Ventilating Institute publishes a guide which provides information about the need for proper ventilation, and how to achieve it. Single copies of the Home Ventilating Guide are free and can be obtained by writing to the Home Ventilating Institute Division of the Air Movement and Control Association.
11 Virginia Rd., White Plains, NY 10603 914 328 1992
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