More About Roofing

 Ventilation: A House Must Breathe

Just as a roof must keep water from entering a house, moisture buildup under the roof must be removed through proper ventilation. Improper ventilation results in warm, moist air generated in the house meeting with colder air in the attic, which causes condensation. Ventilation problems can be seen in a variety of ways, such as blistering and peeling paint on the gable end exteriors because of excessive heat and moisture. Buckling roof shingles are another sign of poor ventilation, as are ice dams in the Midwest and Northeast. Water stains on a ceiling may actually be a result of condensation moisture dripping from under the roof rather than a leak.

Ideally, air circulates under the roof by being drawn up through a continuous soffit vent, through the attic space, and then out the ridge through a continuous ridge vent. This is the smoothest and most efficient system. But few houses have continuous soffit and ridge vents. Most houses, however, do have some type of vent in the roof or an opening at gable ends. Houses with no rafter overhang, or a very short one, may not have soffits. Older houses may not have vents between the rafters leading into the attic space. Venting was not a major problem in older houses because they leaked air everywhere. But with the advent of better roofs and tighter house construction, moisture became a more significant issue.

Calculating the number and size of roof vents is not an exact science but instead is influenced by the climate, the roof pitch, available locations for vents, and the house's orientation to prevailing winds. The Asphalt Roofing Manufacturers Association states:

"In most cases, a minimum free-flow ventilation area equal to 1 square foot per 150 square feet of attic floor area must be designed and properly installed to provide proper ventilation. Where a properly designed and installed eave and ridge ventilation system is employed, a free-flow ventilation area equal to at least 1 square foot per 300 square feet of attic floor area is often sufficient. Combination eave and ridge venting is generally recognized as a superior venting technique."

Vent screens should be cleaned regularly because accumulated dust and grime can significantly restrict air movement. Fans connected to thermostats can be placed at gable end openings to draw hot air out of the attic space when temperatures reach a preset level.

Types of Vents

• Soffit vents: These vents are installed in the soffit (the enclosed portion under the roof overhang) and permit air to flow up under the roof and into the attic. They range in style from 6-inch round stainless steel vent covers that are placed in the soffit between each rafter to continuous vents that run the entire length of the soffit.

• Ridge vents: These vents run the length of the ridge and replace the ridge shingles or tiles. They are designed with interior baffles that permit air to flow out but prevent rain from blowing in.

• Turbine vents: Common on many roofs, the vent top spins on ball bearings. The slightest wind turns the vent, which in turn draws air from the attic.

• Eyebrow vents: Also called turtle vents, they provide curved openings on roof slopes. They should be used in pairs with one on each side of the roof to facilitate air movement.

 Insulation

Insulation is part of the whole roof system, and is designed to prevent both cold and heat from entering the house. Insulation is rated by R factors, which is a measurement of resistance to heat flow. Heat is energy and it always moves toward cooler areas—out of the house in winter, into the house in summer.

The temperature in a well-ventilated attic ideally should only be a few degrees different than the outside temperature. Therefore, to protect the house, the first place to install insulation in an attic is between ceiling joists. If using batts, place the paper or vapor retarder side, against the ceiling to resist the movement of water vapor. If using loose fill, a vapor retarder ideally should have been placed over the bottom of the ceiling joists before the drywall was installed.

Be sure that insulation between ceiling joists does not block any soffit vents. If your house has them, keep the insulation about a foot short of the connection between roof and wall to permit free air movement.

If it’s in your budget, you can then place insulation batts between the roof rafters and the walls, but that will have considerably less impact on protecting the house than putting insulation between ceiling joists.

If you have a cathedral ceiling with little room for standard insulation without blocking air movement, then use baffles to create a space between the roof deck and the insulation. If your cathedral ceiling is formed by tongue and groove lumber on top of rafter beams, you can also use rigid insulation on top of the roof deck, under the roof covering.

 Gutters and Downspouts

Gutters and downspouts are designed to collect water running off the roof and direct it away from the house's foundation. In this regard, the ground should slope away from the foundation so water doesn't pool. Water should also be carried as far as possible from the house by splash blocks, downspout extensions, flexible drains, or even underground drains.

Gutters, which are hung from the edge of the roof or attached to the fascia board, are made from vinyl, galvanized tin, aluminum, copper, and wood. Some come with baked-on enamel coatings, others are bare and must be painted. Among the many choices are seamless aluminum gutters that are custom formed at your house before they are mounted.

Standard sized residential gutters come in 10-foot lengths and are 5 inches and 6 inches wide. For roofs over 1,500 square feet, select the wider gutter. Most sections are connected with slip joints and end caps, and downspout connections are constructed in a similar fashion.

Standard slope for gutters is 1 inch for every 20 feet toward a downspout. Some installers, however, prefer to install gutters level with the roof edge because it looks better. Downspouts are placed at no more than 30-foot intervals, and sometimes at each end of a single 30-foot run. By using elbow connections, downspouts curve from the gutter back to the side of the house, where they are attached with straps.

Seamless aluminum: These are among the best because they require no painting, as galvanized gutters do, and do not crack or bend, as vinyl gutters do. After the installer measures your roof perimeter, aluminum is fed from a spool into a special machine that extrudes the gutters on the spot. Despite the name, these gutters are not entirely seamless, but only have them at inside and outside corners.

Galvanized tin: Among the most widely used of all gutters, galvanized tin has been around for years. Its only drawback is that it must be painted periodically to prevent rust from penetrating the galvanized coating. The gutters are stiff and strong and hold up well in areas with heavy snowfall.

Vinyl: These gutters are the easiest for the do-it-yourselfers. They are sold at all large home centers, are light and easy to put up. They usually come in just brown or white colors. Although easy to install, they do not have the look of permanency of metal gutters and are subject to distortion from heat and cold.

Wood: Although sometimes still found on old houses, wood gutters today are a custom design. They can be beautiful and long lasting with proper care, which means regular cleaning and painting.

Copper: These are also custom gutters, but beautiful and long lasting.

• Over the years, gutter supports become loose, rusted, and broken. Check them periodically and replace or repair as necessary.

• Be sure to clean leaves and debris from the gutters each fall before the rains begin.

• Check that the downspouts are clear. If not, blast the debris out with a hose stream, or use a plumbing snake.

• Check during a rain for any leaks at the gutter joints. A bead of caulk will often be enough to seal the leak.

• Use leaf guards on the gutters to prevent accumulation. Use strainers over the downspout holes. These can be made from a short strip of rolled chicken wire that is inserted into the downspout hole.
   

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