Ice Dam Removal - How To
Do your roofing nails have frost on them? If so, you could have a ventilation problem in your attic. The most important feature of adequate attic ventilation is allowing moisture to escape. Alternately in the summer months ventilation prevents the excessive build up of heat in the attic.
Some home owners block vent openings to keep heat in the house during winter months. This is focusing on the wrong area to prevent heat loss. If your attic insulation is adequate there will be minimum heat loss through your attic.
Signs of moisture damage are, rust rings around your nails that protrude through the sheathing, frost on the nails in winter time ( this later melts and drips onto insulation ), delaminating of sheathing ( normally more prevalent on North side), and black mold on the underside of sheathing.
Correcting lack of ventilation is as easy as increasing the size of your existing vent holes or if not provide ventilation holes. Roof ventilation is either passive or powered. Most residential homes only require passive ventilation. This system is based on a simple rule of thumb, total vent area should be at a minimum 1/300th of the floor space. That vent area should now be divided evenly between your soffits and ridge or gable vents (top and bottom of roof ) allowing a convection current to do your attic ventilation for you, hence the term passive.
The purpose to having equal vents on the top and bottom of your roof is to promote air flow. If you have more vents on the top of your roof then you run the risk of depressurizing your attic which in turn causes warm moist air to be actually sucked through your insulation into your attic causing more moisture problems. Turbine roof vents are not recommended by a lot of roof experts for that very reason. Their faults are listed as being noisy or seized, can depressurize attic on windy days, don't work on calm days and can be a potential leak source.
Ice dams of your roof? Ice dams along the lower edges of your roof when the warm air in the attic melts the snow on the roof above the attic. This usually happens when the temperature is in the low twenties and snow has accumulated on the roof. Melting snow then trickles down to the edge of the roof where it freezes. The roof overhang is colder because there is no attic beneath it releasing any heat. The cycle repeats itself over and over creating your ice dam. A well ventilated attic is cold in the winter. The colder the attic is the less likely it is for ice dams to form. Ice dams are a sign of either inadequate ventilation in your attic or a lack of insulation. If you have ice building up on your roof on the outside corners just at the edges, go up into the attic and you might find that the insulation contractor didn't quite make it into the far corners when he was blowing in the insulation. Napoleon Home Inspections comes across this problem quite a lot, adding insulation is normally all that is required to fix this problem. Usually there is enough insulation already in the attic, it just has to be redistributed. The other problem that Napoleon Home Inspections has found to be prevalent in some attics is the lack of soffit ventilation caused by insulation blocking the space between the rafters and the soffit. This also is a quick fix, simply insert Sur-vents or Mor-vents, which are Styrofoam spacers especially designed to allow the air to move between your soffit vents along your roof to the ridge vents. These are light weight and are simply stapled in place in every second or third rafter space creating uninterrupted air flow up to your ridge vents.
Condensation of water vapor on cold surfaces in attics can cause attic wood products to rot, which can lead to costly repairs. Condensation typically occurs when warm, moist air migrates into the attic from the living spaces below. Research indicates unusually high humidity levels in the home's living spaces is strongly associated with attic condensation problems.
Building codes have some requirements that attempt to prevent the problems of ice dams and attic condensation. But codes do not address all the issues, and many houses are built without following building codes. It is the role of the builder or designer to understand the relationship of humidity and air movement when designing and constructing the house so these problems don't occur.
Avoid attic access from conditioned spaces. Access panels or doors can be located in unconditioned spaces, such as the garage, reducing the chance of warm, humid air rising up into the attic if there is not an airtight seal. No matter where the attic access panels or doors are located, make sure they are insulated and as air tight as possible.
Avoid penetrating the ceilings below attics with ductwork or piping.
Never exhaust air into the attic space. Exhaust ducts from kitchen and bathroom exhaust fans, as well as exhaust ducts from clothes dryers, should be terminated outside the home.
Limit indoor relative humidity in the living space to no more than 35 percent during the winter.
Depending on the climate, provide a vapor retarder or vapor barrier at all ceilings and walls that about attic spaces.
All attic spaces must be ventilated.
The best ventilation solution is through natural convection by installing an equal amount of vents in the soffits (low point of the attic and at or near the ridge (highest point in the attic). It is generally accepted that using a combination of soffit vents and roof ridge vents is the best way to achieve ventilation by natural air movement. In cases where the home design does not have soffits, it may be possible to replace the drip edge at the bottom edge of the roof with a vented drip edge. Gable end vents (i.e. vents in the triangular section of attic wall bounded by the pitched roof) may be an option for some homes. Consult a building professional for the best option for your home.
Open attics are usually easier to vent than cathedral ceilings. If cathedral ceilings are used, maintain an air space of at least 1 1/2 inches to 2 inches (for most situations) between the top of the insulation and the bottom of the roof deck. The amount of air space needed varies depending on the length of the ceiling between the soffit and ridge vents, the slope of the roof, the venting capabilities of the soffit and ridge vents, and the thermal insulating value of the insulation below the airspace. Sometimes up to a 4 inch air space is needed if the run of the ceiling is long, there is a limited amount of venting, and there is a limited amount of insulation.
Insulation Requirements
Use rigid plastic air chutes ( Mor-vents or Sur-vents) to keep attic insulation from blocking airflow from soffit vents to roof idge vents. Do not use cardboard or thin polystyrene air chutes which can easily lose their shape or be flattened, blocking airflow.
Provide insulation levels as recommended by the Department of Energy. In cold climates this ranges from R-38 to R-49 depending on where you are in the country, and what type of heating you have. This increased attic insulation will make your home more energy efficient and should help lower your heating/cooling costs. For more information on home insulation ask your local building supply store what is recommended for your region.
Use a membrane to keep out water and ice on top of the roof deck at the base of all roof planes. The membrane may be a self-adhesive, rubberized asphalt sheet which is directly adhered to the roof deck and seals against water entry, even at nail penetrations. The membrane should be attached to the roof deck from the gutter (or edge of roof) to a point on the roof which is at least 30 inches inside the exterior wall of the house.
Eliminate moisture problems from crawl spaces with a ground vapor barrier. The vapor barrier should be 6 mile thick polyethylene sheeting completely covering any exposed soil. Seams should be overlapped a minimum of one foot. Recent research has shown that many crawl space moisture problems can be cured by sealing the crawl space vents.
Eliminate any heat sources in the attic. (Ductwork in the attic should be sealed and insulated.)
Do not install mechanical equipment or water heaters in attics, especially in cold climates.
What To Do When You Have an Ice Dam Causing Damage
If you see water staining at an exterior wall or ceiling where there is snow on the roof above it, act quickly to avoid extensive damage.
Hire a contractor to carefully remove most of the snow from the roof above the ice dam. The contractor should avoid touching the roof with the removal equipment or even walking on the roof if possible. Cold roofs are more prone to damage because they are more brittle than they are in the summer. Routine snow removal from the roof should be avoided because there is a good chance of roof damage in the process.
Have the contractor create one or two grooves in the ice dam to allow the ponding water to drain off. These grooves should not be taken down to the roofing as this may damage the roof. If necessary, the contractor can use heat tape in the groove on a temporary basis to keep the groo
These are short-term fixes. In order to avoid the same problem in the future, a qualified contractor should assess the amount of attic insulation and attic ventilation (especially around where the ice dam formed), and look for holes in the air barrier between the living spaces and the attic.
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