An ice dam is an ice build-up on the eaves of sloped roofs of heated buildings that results from melting snow under a snow pack reaching the eave and freezing there. Freezing at the eave impedes the drainage of meltwater, which adds to the ice dam and causes backup of the meltwater, which may cause water leakage into the roof and consequent damage to the building and its contents if the water leaks through the roof.
Ice dams occur on heated buildings with sloping roofs in cold climates with deep snow accumulation. Ice dams on roofs form when accumulated snow forms an insulating layer under cold conditions that would cause the freezing point to be within the snow layer, if it were not subject to melting. Instead, building heat coming through the roof's surface melts the snow resting on it. This causes meltwater to flow down the roof, until it reaches below a place on the roof's surface that is below freezing—typically at the eaves where there is no building heat. When the meltwater reaches the frozen surface, ice accumulates, growing a barrier that impedes further passage of meltwater off the roof. Ice dams may result in leaks through the roofing material, possibly resulting in damaged ceilings, walls, roof structure and insulation, or injury when the ice dam falls off or from attempts to remove ice dams. [1]
The melting of roof snow comes from the combination of three basic causes: [2]
If any of these factors is absent, ice dams cannot form. Above freezing air does not promote ice dams, nor does granulated spring snow on a roof, which has poor insulating capabilities, nor does a roof that doesn't warm to above freezing at its surface. Ice dams may occur when the under-roof temperature is above 30 °F (−1 °C) and the outdoor air temperature is below 22 °F (−6 °C). [2]
Ice dams on sloped roofs can be mitigated in several ways: [3] [2] [4] [5]
When an ice dam occurs there are some maintenance options to remove it: [5]
Assuring integrity of the roof's waterproofing prevents leaks and consequent damage.
Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor to ice as the water vapor reaches the freezing point. In temperate climates, it most commonly appears on surfaces near the ground as fragile white crystals; in cold climates, it occurs in a greater variety of forms. The propagation of crystal formation occurs by the process of nucleation.
Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.
A roof is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temperature, and wind. A roof is part of the building envelope.
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away.
Freezing rain is the name given to rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow, ice pellets, or hail, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter, including the ground, trees, electrical wires, aircraft, and automobiles. The resulting ice, called glaze ice, can accumulate to a thickness of several centimeters and cover all exposed surfaces. The METAR code for freezing rain is FZRA.
A winter storm is an event in which varieties of precipitation are formed that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain—rain that encounters frozen surfaces. In temperate continental climates, these storms are not necessarily restricted to the winter season, but may occur in the late autumn and early spring as well. Very rarely, they may form in summer, though it would have to be an abnormally cold summer, such as the summer of 1816 in the Northeastern United States.
An icicle is a spike of ice formed when water dripping or falling from an object freezes.
A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer. Because thermal energy is also transferred by conduction and convection, in addition radiation, radiant barriers are often supplemented with thermal insulation that slows down heat transfer by conduction or convection.
Snow removal or snow clearing is the job of removing snow after a snowfall to make travel easier and safer. This is done by both individual households and by governments and institutions.
A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof. Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world. The National Roofing Contractors Association defines a low-slope roof as having a slope of 3-in-12 or less. Flat roofs exist all over the world and each area has its own tradition or preference for materials used. In warmer climates, where there is less rainfall and freezing is unlikely to occur, many flat roofs are simply built of masonry or concrete and this is good at keeping out the heat of the sun and cheap and easy to build where timber is not readily available. In areas where the roof could become saturated by rain and leak, or where water soaked into the brickwork could freeze to ice and thus lead to 'blowing' these roofs are not suitable. Flat roofs are characteristic of the Egyptian, Persian, and Arabian styles of architecture.
Electric heat tracing, heat tape or surface heating, is a system used to maintain or raise the temperature of pipes and vessels using heat tracing cables. Trace heating takes the form of an electrical heating element run in physical contact along the length of a pipe. The pipe is usually covered with thermal insulation to retain heat losses from the pipe. Heat generated by the element then maintains the temperature of the pipe. Trace heating may be used to protect pipes from freezing, to maintain a constant flow temperature in hot water systems, or to maintain process temperatures for piping that must transport substances that solidify at ambient temperatures. Electric trace heating cables are an alternative to steam trace heating where steam is unavailable or unwanted.
An attic is a space found directly below the pitched roof of a house or other building; an attic may also be called a sky parlor or a garret. Because attics fill the space between the ceiling of the top floor of a building and the slanted roof, they are known for being awkwardly shaped spaces with exposed rafters and difficult-to-reach corners.
In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many parts of the world, in some cases contributing high fractions of the annual runoff in a watershed. Predicting snowmelt runoff from a drainage basin may be a part of designing water control projects. Rapid snowmelt can cause flooding. If the snowmelt is then frozen, very dangerous conditions and accidents can occur, introducing the need for salt to melt the ice.
Glacier ice accumulation occurs through accumulation of snow and other frozen precipitation, as well as through other means including rime ice, avalanching from hanging glaciers on cliffs and mountainsides above, and re-freezing of glacier meltwater as superimposed ice. Accumulation is one element in the glacier mass balance formula, with ablation counteracting. With successive years in which accumulation exceeds ablation, then a glacier will experience positive mass balance, and its terminus will advance.
Domestic roof construction is the framing and roof covering which is found on most detached houses in cold and temperate climates. Such roofs are built with mostly timber, take a number of different shapes, and are covered with a variety of materials.
Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be produced during volcanic eruptions, in a similar way in which the more dangerous lahars form.
Subnivean climate (From Latin for "under" and "of snow" and English -an. This is the environment of many hibernal animals, as it provides insulation and protection from predators. The subnivean climate is formed by three different types of snow metamorphosis: destructive metamorphosis, which begins when snow falls; constructive metamorphosis, the movement of water vapor to the surface of the snowpack; and melt metamorphosis, the melting/sublimation of snow to water vapor and its refreezing in the snowpack. These three types of metamorphosis transform individual snowflakes into ice crystals and create spaces under the snow where small animals can move.
Ice sheet dynamics describe the motion within large bodies of ice, such those currently on Greenland and Antarctica. Ice motion is dominated by the movement of glaciers, whose gravity-driven activity is controlled by two main variable factors: the temperature and strength of their bases. A number of processes alter these two factors, resulting in cyclic surges of activity interspersed with longer periods of inactivity, on both hourly and centennial time scales. Ice-sheet dynamics are of interest in modelling future sea level rise.
A snowmelt system prevents the build-up of snow and ice on cycleways, walkways, patios and roadways, or more economically, only a portion of the area such as a pair of 2-foot (0.61 m)-wide tire tracks on a driveway or a 3-foot (0.91 m) center portion of a sidewalk, etc. It is also used to keep entire driveways and patios snow free in snow prone climates. The "snow melt" system is designed to function during a storm thus improve safety and eliminate winter maintenance labor including shoveling or plowing snow and spreading de-icing salt or traction grit (sand). A snowmelt system may extend the life of the concrete, asphalt or under pavers by eliminating the use of salts or other de-icing chemicals, and physical damage from winter service vehicles. Many systems are fully automatic and require no human input to maintain a snow/ice fee horizontal surface.
Snow science addresses how snow forms, its distribution, and processes affecting how snowpacks change over time. Scientists improve storm forecasting, study global snow cover and its effect on climate, glaciers, and water supplies around the world. The study includes physical properties of the material as it changes, bulk properties of in-place snow packs, and the aggregate properties of regions with snow cover. In doing so, they employ on-the-ground physical measurement techniques to establish ground truth and remote sensing techniques to develop understanding of snow-related processes over large areas.
 | Wikimedia Commons has media related to Ice dams (roof) . |
| Crystalline types |  | ||||
|---|---|---|---|---|---|
| Formations and phenomena |
| ||||
| Ice-related activities |
| ||||
| Constructions | |||||
| Work | |||||
| Other uses | |||||
| Ice ages | |||||
