Ice dams can be referred to as a ridge or mass of ice which accumulates along the rooflines’ lower edges. They usually happen in climates having regular snowfall as well as cold winter temperatures.
Ice dams may be severe which could weigh lots of hundreds of pounds, which could compromise the roof eaves’ structure. Also, ice dams can cause the meltwater to back up below the shingles, which can flow downwards causing damage to the surfaces of ceilings and walls. If nothing is done concerning an ice dam, it could cause some serious damage to your gutters, roof, insulation drywall, interior drywall, paint, as well as other surfaces
Ice dams, in some houses, are a very severe and damaging problem, but other houses may not face any troubles at all. The mystery behind some houses being plagued with ice dams excluding some other houses is yet to be known; the answer to this question will be known in the attic.
Causes of Ice Dams
The formation of an ice dam happens when the snow melts on a roof’s warmer, upper part. This meltwater then flows towards the colder eave and then freezes. This frozen meltwater, as it gathers, causes a blockage that prevents the flowing of snowmelt off the ice dam roof.
The ice starts backing up below the roof shingles, and then melts a second time, getting the roof sheathing soaked and then leaks into the attic. Here the insulation is soaked (causing it to be less effective), which could leak through the drywall of the ceiling and then moves into the living space. Ice dams with a large size could be extremely heavy and can cause damage to gutters and even cause some safety hazards to humans living below.
This issue happens when the space found in the inner part of an attic or the roof deck’s underside goes higher than the freezing point. As the shingles are heated by the warm air usually underneath the roof as well as melts the roof’s snow, this water flows down the roofline till it gets to the eave structure, which has a freezing temperature that will refreeze the water.
Ice dams begin or worsen when there’s heavy snow on the roof due to the insulating properties of the snow. The layer if the snow traps war air underneath the snow, which leads to its melting. One great way to prevent the formation of ice dams is to be sure that the attic’s air or air found below the roof deck doesn’t become too warm. If this air present in the attic stays cold enough, then the snow lying on the roof can never melt. This will be achieved through a combination of:
- Ventilation beneath the roof deck: this helps to ensure the colder outside air keeps circulating the attic, preventing this air from warming higher than the freezing point.
- Insulation of the ceiling underneath the attic: This prevents the warm air from getting up and reaching the attic space
- The blockage of any source of heat that may be contributing to the attic’s high temperatures
Causes of different roof surface temperatures
Since the majority of ice dams accumulate at the roof’s edge, then it means there is another source of heat warming the roof elsewhere. Majorly, this heat comes from the house. In rare cases, the solar heat gain may lead to these differences in temperature.
The heat from the home
The heat that comes from the house goes to the surface of the roof in three main ways: radiation, convection, and conduction.
Radiation is heat transferred by electromagnetic waves from the hot frying pan to your hand. Another example is standing outside on a very sunny day and then feeling the sun’s heat. The transfer of the sun’s heat to you is achieved by radiation. Also, when your hand is placed above this frying pan, there are two methods through which heat reaches your hands. The air above the pan is heated and it rises. This rising air transports energy/heat to your hand. This transfer of heat is only possible by convection. Conduction has to do with the heat energy that travels through a solid.
In a house, the movement of heat through the insulation and ceiling is via conduction usually passing through the ceiling’s slanted portion. The insulation’s top surface is usually warmer than the attic’s outer surroundings. Therefore, the heating of the air present above the insulation happens and then it rises, transporting heat to the roof via convection.
Loss of heat by air leakage
This is another form of convection that transports heat to the attic and then gives warmth to the roof. In most homes, this is the main form of heat transfer which causes ice dam formation.
The chimney is another heat source in the attic. Using fireplaces as well as wood stoves frequently allows the transfer of heat from the chimney to the attic. Spaces that are not well insulated or have leaky ductwork could also be a heat source. This also holds for knee wall spaces.
Exhaust systems just like those in the bathroom or kitchen may also play a role in snow melting. There may be a need to extend or move these exhaust systems in areas that have high snowfall.
How to Prevent Ice dam
There are ways to prevent ice damming, which includes ventilation, insulation, elimination of attic heat sources, and using electric heat cables. Let’s quickly look at these methods.
Houses having very good attic ventilation in most cases do not fall victims of ice dams, and the reason behind this is simple: when the cool outside air is circulated in the attic space, the surface of the roof stays below freezing levels and therefore the snow present on the roof cannot melt.
There are different ways to improve ventilation in the attic.
When there are insulated spaces between the rafters, a continuous airflow can be created from the soffit (the roof eaves’ underside) to the roof’s peak. Usually, a ridge and soffit vent system requires the installation of insulation baffles at the roof’s lower side, above the outer walls. The insulation is held back by the baffles by 1-2 inches, which creates a channel for free airflow past the insulation.
If a ridge and soffit system is not desirable or feasible, then the provision of ventilation with gable or soffit vents for the air intake and different conventional roof vents can be done. Generally, 1 sq. ft of free ventilation for every attic floor space of 150 sq. ft should be provided by any ventilation system.
Another great method is the insulation of living spaces’ ceiling underneath the attic or against the roof’s inner surface. If what you have is an open attic, then this means the attic’s floor should be insulated. These insulation methods will prevent the rising of heat to the deck of the roof and then heating it till it gets to a point when the snow on the rooftop can be melted.
Sealing up the channels of air from the living space underneath the attic is also very important as insulation. Spaces and gaps around chimneys and plumbing pipes could result in a great source of heat that can flow from these spaces into the attic.
Elimination of Attic heat sources
Heat sources could be present in your attic which you’re ignorant of. Most times, this happens when recessed lights that are older are mounted in the attic’s floor. With this, a surprising amount of heat can be radiated into the attic, which is enough to heat the air properly above the freezing point, most especially in cases when there is poor ventilation
Other sources of heat include vents in cloth dryers, uninsulated HVAC ductwork, or kitchen or bathroom exhaust fans that are not well vented.
Electric Heat Cables
Another method is the installation of an electric heat cable along the edges of the gutters and roofline.
When these cables are looped along the roof’s edge in a zig-zag pattern, the heating cable will not allow the melting water to cool enough to make it freeze when it gets to the eaves. Rather than freeze, the meltwater just flows to the ground without causing any harm.
Heat cables on roofs don’t look attractive, but if well installed can help in preventing ice dams. However, you must know that there’s always a risk involved in mixing electricity and water. Make sure the directions of the manufacturer are followed precisely.
Fighting against Ice dams
Carrying out preventive methods is best during the fall, summer, or spring, however, if you’ve failed to follow these measures and you’re currently facing some serious problems with ice dams, then some options can help eliminate or minimize them:
- In cases of heavy rainfall, use a roof rake
- Use ice-melt products or calcium chloride
- Chip the ice off by hand using an extension ladder
- Hire the services of a professional
Ice dams can be very disturbing as they cause damage to rooftops and depending on the weight of this ice dam, it could affect the eaves’ roof structure. Here we’ve been able to discuss the various causes as well as ice dam solutions to take in case you’re battling with this problem. We are sure that by following any of these methods, you will easily get rid of ice dams.