With snow on the roof, go outside and take a look at the roof. If you see the snow melting around the roof vents, chances are that your insulation is releasing heat from your home, into the attic. Some vents could be from bathroom exhaust and you should expect to see melting there. If you only see melting at one vent, it could be a bathroom exhaust.
If you see other parts of the roof snow melting before the rest, this is also another indicator of failing insulation. Many times this is seen above the FROG (Family Room Over Garage) or a vaulted ceiling where the ceiling is parallel to the roof. There is limited space for insulation and the necessary air flow for venting.
Ice damming is a condition where ice forms on the eve section of the roof, sometimes with icicles forming up to and over one hundred pounds. You can imagine the damage this causes when these come loose, sometimes taking parts of the roofing material with them. If there is another roof below, a hundred pound spear of ice falling on it, certainly has negative effects to say the least.
Ideally, the temperature in the attic should be the same as the outdoor temperature. If it’s ten degrees outside, it should be ten degrees in the attic. This is a little harder to match in the summer, but the closer it is to matching in the summer, the less fatigue there will be to the roof.
If either the attic venting or insulation is inadequate, snow will start to melt on the roof and as the melted snow runs down the roof, it hits the eves where the temperature can still be below freezing and as such, it re-freezes causing an ice dam. Proper ventilation will help keep the attic temperature the same as the outside temperature, but even with good ventilation, poor insulation is going to induce more of your hard-earned heat into the attic.
Seldom do we find attic insulation that is sufficient. Attics, like crawl spaces are often neglected areas of the home and in the attic, insulation compacts with age and looses much of its insulating qualities. The standard R rating for attics today is R-38 and using the chart below, you can measure what you have in your attic.
The insulation process itself can also hinder the attic venting if not done properly. The best method of venting an attic is open soffit and high box or ridge vent combination, with a power vent for backup in the event the temperature exceeds a certain level. This works great unless the blown-in insulation blocks airflow from the soffit vents. This is why it’s important to install rafter baffles above the soffit inside the attic before the insulation is blown in. This reserves a path for the outside air to enter the attic space as it should.
The bottom line is that when you have snow on the roof, you can tell a great deal about your attic insulation and ventilation.
We hope this helps. . .