In many homes, there is little space in regions like this for insulation, so it is important to use insulation with high R-value per inch to reduce heat loss by conduction. Convection and radiation heat transfer can be reduced by adding insulation.
This will make the top surface temperature of the insulation closer to surrounding attic temperatures directly affecting convection and radiation from this surface.
There is another type of convection that transfers heat to the attic space and warms the roof. In the diagram, the winding arrow beginning inside the house and going through the penetration in the ceiling, from the light fixture to the attic space, illustrates heat loss by air leakage.
In many homes this is the major mode of heat transfer that leads to the formation of ice dams. Exhaust systems like those in the kitchen or bathroom that terminate just above the roof may also contribute to snow melting. These exhaust systems may have to be moved or extended in areas of high snow fall. Other sources of heat in the attic space include chimneys. Frequent use of wood stoves and fireplaces allow heat to be transferred from the chimney into the attic space.
Inadequately insulated or leaky duct work in the attic space will also be a source of heat. The same can be said about knee wall spaces. Immediate and long-term actions will increase the snow load that your roof has to carry because the snow will no longer melt.
If your house is built to current codes, there should not be a structural problem. Roofs, like the rest of the home, should be designed to withstand expected snow loads. In Minnesota, plans showing design details to meet expected snow loads are usually required to receive a building permit. The plans for your home may be on file at your local building inspection office. To help you understand the plans, or if you cannot find plans for your home, you may want to contact an architectural engineering firm.
A professional engineer should be able to evaluate the structure of your home and answer your questions about the strength of your roof. Natural roof ventilation can help maintain uniform roof temperatures, but if the long-term actions described here are done effectively, then only small amounts of roof ventilation are needed to maintain uniform roof surface temperatures. If heat transfer has been reduced substantially, then snow will build up on the roof and cover natural roof ventilation systems, reducing attic ventilation rates.
Natural attic ventilation systems are needed to dry the attic space and remove heat buildup during the summer. Mechanical attic ventilation is not a recommended solution to ice dams in Minnesota. Because at that point even an energy-efficient home can start sprouting ice dams. In these conditions, aside from the obvious removing the snow from your roof , you might think about turning down your thermostat a little.
Yes, energy audits, roof-raking, and lowering the temperature in your home are hassles. Even if you do get an ice dam, that ice dam you worked hard to prevent will probably be smaller and less damaging than an ice dam for which you left out a welcome mat. But while icicles add visual appeal, ice dams can be a hidden risk to the roof and gutters as well as the attic and interior walls. How Do Ice Dams Form? Ice dams form because heat in the attic warms the roof but not the eaves. As the snow on the roof of a house melts, it runs down the roof where it hits the colder roof section above the eaves and freezes.
Through one or more thaw-and-freeze cycles, the ice thickens in the gutter and backs up onto the roof. Then, additional snow melt on the warm roof gets caught under the shingles and seeps through the roof. The water drips inside the roof into the attic and down the interior walls of the house. The water damage that results from ice dams can be significant to roof, shingles and gutters and to attic insulation, contents and interior walls.
How do they form? And what to do about them. Keep the roof cold by making sure warm air is not leaking into the attic from the house.
Seal plumbing vents and electrical wires with foam spray or caulking. Increase insulation in the attic. Clear leaves and debris from gutters before winter, which will prevent blockage.
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