Attic and Roof Ventilation

A properly balanced attic ventilation system is essential for your home. Most common forms of venting are gable vents (openings in the gable or short end of the attic wall), ridge vents (opening at the roof peak) and soffit vents (openings at the soffits or the lowest area of the roof).

A good system must have a way for the air to get in (usually the soffit vent), and get out (usually the ridge vent). A chimney effect helps the air circulate through the attic, cool air in through the soffits and hot air out the top ridge. Wind blowing across the roof peak outside creates negative pressure, helping the chimney effect and air circulation.

So what does attic and roof ventilation do?

• Helps prevent ice dams in the winter. An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas. The heat inside the attic causes the top part of the roof to be warmer than the lower edge - snow melts at the peak, drips down the roof and ices up at the bottom edge. Ventilation in the attic keeps the temperature at the top and bottom levels more consistent and reduces the formation of ice (insulation helps also).
  
• Reduces condensation and moisture in the attic and the home. Prevents wood rot, peeling paint, mold and mildew.
  
• Prevents premature aging and failure of roof shingles and decking. High temps bake the roofing materials from the attic side, ventilation helps the attic stay cooler. Most roofing manufacturer's warranties require proper roof ventilation to ensure that the materials perform as specified. If you want that new 30 year roof to actually last 30 years the attic (including the roof decking and the underside of the shingles) needs ventilation.
  
• Helps keep the entire home cooler in warm weather.

Some guidelines regarding attic and roof ventilation:

• There should be vents at the bottom (soffits) and the top (ridge) of the roof for proper airflow, but anything is better than nothing.
  
• As a rule you want the air temp of the attic to be about the same as the outdoors. If there is a wide difference you need to increase ventilation.
  
• Don't block vents. Covering your attic gable vents in winter doesn't keep your house warmer (increase the insulation in the floor of the attic to achieve this). Don't let the attic floor insulation block the soffit vents at the lower roof edge.
  
• Soffit and ridge vents are considered a balanced system. Ask a ventilation contractor for advice if your attic also has gable vents - the gable vents may negate the airflow from the soffits and ridge and may need correction.
  
• Consider adding an attic fan. Many cost below $100, are easy to install, and run on a thermostat that kicks in when attic temperatures get too high.
  
• Make the ventilation uniform throughout the attic, with no dead spaces. The ridge and soffit vents should be continuous if possible. If using gable vents bigger is better.

Insulation

Insulation is an important (and often overlooked) component of your home. Properly installed and sized insulation will help keep your home cool in summer, warm in winter, reduce drafts and keep the noise level down between the living space and outdoors.

The ability of insulation to slow the transfer of heat is measured in "R" values. The higher the "R" value, the better the insulation's ability to resist heat flow thru it.

If you plan on keeping your home for more than a few years insulation will pay for itself in energy savings by decreasing heating and cooling bills. Be sure to have proper insulation in the following areas:

• Attic - Department of Energy recommends R-38 for most of the counrty. Install insulation in the attic floor as needed to separate the living space below from the attic above. Insulation is not normally installed in gable walls or touching the roof decking in this area of the country. Don't forget to insulate over the attic hatch or pull-down stairway.
• Pipes - insulate water supply pipes carrying hot water for energy savings. It is especially important to insulate all supply pipes in unheated areas such as basements and crawlspaces to prevent freezing (the pipes will burst) and condensation.
• Ducts - insulate heating and cooling ducts for energy savings. Insulation here will also prevent condensation, which will help to prevent mold and mildew in the home.
• Walls - proper insulation here will keep heating and cooling bills down, make the home quieter, and prevent drafts.
• Hot Water Heater - uses less energy when insulated, saves money. Be sure to leave openings for the controls, don't place the insulation close to any flames on the unit.
• Basement - insulate floors above cold spaces, such as unheated basements, crawlspaces and garages. In garages make sure there is a fire barrier covering the insulation.

A prime component of your insulation system is the vapor barrier. Vapor barriers keep moisture from moving from one space to another. For example, a vapor barrier should be installed in a dirt crawlspace to keep moisture from rising up through the dirt and entering the living space above. Make sure vapor barriers are installed correctly to reduce moisture, mold, and mildew in the home.

Last but not least, make sure there are no gaps in the insulation where air and moisture can penetrate. Air movement negates the purpose of insulation - when it is improperly installed insulation can be useless. Make sure fiberglass batts in the attic cover the flooring with no gaps between. Sections of duct and pipe insulation should be joined and secured with tape. Wall insulation should be correctly installed and secured to prevent settling where gaps can occur.

Contact an insulation professional for advice before getting started. For more information visit http://www.energy.gov/.