Figure 5-31.—Attic outlet vents.A warm attic that is inadequately ventilated andlowering the temperature in these spaces. Insulationinsulated may cause formation of ice dams at the corniceshould be used between ceiling joists below the attic or(fig. 5-30, view A). During cold weather after a heavysnowfall, heat causes the snow next to the roof to melt.Water running down the roof freezes on the coldersurface of the cornice, often forming an ice dam at thegutter that may cause water to backup at the eaves andinto the wall and ceiling. Similar dams often form in roofvalleys. Ventilation provides part of the solution to theseproblems. With a well-insulated ceiling and adequateventilation (fig. 5-30 view B), attic temperatures are lowand melting of snow over the attic space greatly reduced.In hot weather, ventilation of attic and roof spacesoffers an effective means of removing hot air androof space to further retard heat flow into the roomsbelow and materially improve comfort conditions.It is common practice to install louvered openingsin the end walls of gable roofs for ventilation. Airmovement through such openings depends primarily onwind direction and velocity. No appreciable movementcan be expected when there is no wind. Positive airmovement can be obtained by providing additionalopenings (vents) in the soffit areas of the roof overhang(fig. 5-31, view A) or ridge (view B). Hip-roofstructures are best ventilated by soffit vents and by outletventilators along the ridge. The differences in5-25
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business