As spring nears and much of the country waits for mild weather, a significant roofing problem can be worsened by the late winter temperature swings.
Ice dams occur because the eaves are generally colder than the rest of the roof. When water melts off the main part of the roof and reaches the eaves, it can refreeze and create a dam. The dam can prevent water from draining off the roof, causing the water to back up under the shingles and into the dwelling.
Building envelope system provider Henry says that tell-tale signs of the dreaded ice dam have popped up all over the U.S. and Canada during the past few months – icicles hanging from the gutters, ice buildup at the eaves or, even worse, water leakage in the attic, ceilings or walls.
How Ice Dams Form
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Ice dams cause roof leaks. Visit www.henry.com for solutions. (PRNewsFoto/Henry Company)Roof snow melts through a combination of direct sunlight on the roof, as well as from heat loss through the roof of the building. Normally, snow melts at a rate that allows the snow and ice to run off of the roof, and drainage occurs without incident. However, at the eaves of the roof, less heat is present to melt snow and ice. Ice dams can form when snow on the roof melts and re-freezes in the gutters. Behind the dam, water freezes and thaws, expanding and contracting. This action forces roofing materials apart, traps melted water and allows it to run up under the shingles and then through the roof sheathing, often causing serious damage.
Even with insurance, this can be costly for the homeowner, as most homeowner insurance policies don’t cover ice dam removal or roof replacement – unless the homeowner can prove that the ice damaged the roof. Typically, shingle warranties also do not protect against ice dams.
Act Quickly!
Henry says a professional weatherization contractor is specially trained to work under dangerous, icy conditions and is knowledgeable about heat transfer problems. They may be listed under Energy Management and Conservation Consultants or Insulation Contractors in the Yellow Pages.
This is a job for a professional; should you choose to handle it yourself:
Do not attempt to chip away at the ice dam, as rakes and axes may damage the roof shingles that are especially brittle and prone to breakage when cold.Salt or chemicals are corrosive and may shorten the life of metal gutters and downspouts.Short-term Solutions
Once the ice dam has drained, it is important to keep the gutters clean and the roof cool. The two key ways are:
Improve the insulation in your attic: Houses in the northern United States and Canada should be equipped with insulation (between the attic floor and interior ceiling) with a heat transfer value of at least R-38 (i.e., that’s about 12 inches of fiberglass batts or blown-in cellulose). Insulation should be continuous and airtight across the ceiling so that no warm, moist air can flow from the house into the attic space. Spray polyurethane foam insulation is an especially effective insulator, as it has a very high R-value, is waterproof and forms an airtight seal around electrical conduit, pipes, vents, hatch doors and lighting fixtures. This has the added benefit of lowering your energy bills!Ventilation: As a rule of thumb, there should be one square foot of vent for every 150 feet of attic floor area. Added gable or ridge vents help to allow heat and moisture to escape the attic effectively, and reduce the chance of ice dams forming.Long-term Solutions
The only way to completely eliminate leakage due to ice dams is to modify or replace your roof with a properly installed, high-quality roof that includes an eave protection membrane or a continuous ice-and-water barrier. Eave protection membranes are self-adhered materials that are installed on the roof at the eaves, extend 36-44? up the roof and reside under the shingles. These membranes are self-sealing, continuous barriers, that offer a second layer of protection in case an ice dam forms and water leaks under the shingle. They are commonly available and add only a small amount of incremental cost to a new roof. An even more effective and foolproof technology is a continuous, self-adhered ice-and-water barrier. These materials replace traditional roofing felt underneath the shingles on the roof. They fully adhere to the roof and create a plastic-lined, self-sealed, continuous water barrier that provides a strong secondary layer of protection underneath the shingles that covers the entire roof.
Rain Screen building envelope system
This and the next two pictures show condensation accumulation on the glass’ inside surface. This is very common in monolithic glass applications used in the past.
This and the following two pictures show condensation accumulation on the glass’ inside surface. This is very common in monolithic glass applications used in the past.Surface condensation is the process whereby water is deposited from air containing water vapor. For this to occur, factors like temperature and moisture content need to occur at the same moment. Surface condensation is not only associated with cold or humid climates, it can manifest at room temperatures as high as 60 degrees Fahrenheit (if the room temperature drops from 80 degrees Fahrenheit at 50 percent relative humidity, for example). Therefore, it may happen in any project when the wall’s thermal behavior has been overlooked or not designed properly. On other occasions, the thermal behavior has been addressed but interfaces between adjacent systems were not analyzed.
Consequences from condensation are well known within the industry such as: mold growth, dampness, wall paper peeling, insulation decay, corrosion, pattern staining, etc. The good news is that these issues can be minimized if the system’s thermal behavior is checked or modeled. This way, any potential problem can be addressed. The technology now exists, where with accuracy and precision the condensation issues and thermal bridging can be predicted and avoided. And generally, this engineering cost cannot even be compared with the cost of having to repair a problem caused by these factors.
Interstitial condensation can become a problem if the wall’s air cavity is too small to allow some air movement or if thermal insulation is insufficient to prevent heat loss. The problem is that it can take several years before we notice the problem. Draining the cavity is also very important, as well as moving this drained water, in a controlled manner away from the building.
Constant condensation might damage adjacent materials, and depending on the frequency, it might even cause corrosion of metal.For Illustration 2, it can be seen that the inside temperature is relatively low due to the lack of protection from the outside environment. There is only a thin metal cap at the underside of the framing member. Due to this, cold temperature is drawn towards the inside of the building. It is most likely that surface condensation will form along this entire framing member, unless the detail is modified or thermally improved.
