Why does my roof have patchy snow?

First off, let’s do some myth busting.

It’s not a lack of ventilation

Some people think that they have patchy snow because their roof isn’t properly ventilated.

That’s just not the case. To be clear - attic ventilation is really important. If you don’t have enough air flow in your attic, then you can have all kinds of issues with moisture, mold, and mildew. But a lack of ventilation doesn’t cause warm air from your home to melt the snow on your roof.

Attic insulation is the key

Adding insulation to your attic is like putting a warm hat on your head when it’s cold outside.

Heat naturally flows from warmer areas to cooler areas, so in the winter, attic insulation prevents heat from escaping through your roof, and in the summer, it prevents heat from entering through the roof.

Attic insulation works by creating a “thermal barrier” that reduces the flow of heat between the attic and the rest of the house. It’s essential to maintain a comfortable temperature in your home, especially in rooms that are connected to the attic.

There are different types of attic insulation, such as cellulose, fiberglass, and spray foam insulation. Each type has a different R-value, which measures how well it resists heat transfer.

The higher the R-value, the better the insulation. We generally insulate attic floors to R-50. What does that mean? When you look at the floor of your attic, you should see a consistent layer of insulation that’s about a foot and a half deep.

If you have spray foam attic insulation, you should see a thick, unbroken layer of foam on the slopes of your attic.

Don’t forget to seal air leaks

Every attic insulation project that we do starts with air sealing. What’s air sealing? We use caulk and foam to seal large and small air leaks that we find. Here are the most common opportunities for air sealing in attics:

• Behind kneewalls: These are the short walls that separate the finished part of the attic from the unfinished part. They often have open stud cavities that allow air to flow from the house to the attic.
• Attic hatch: This is the door or panel that provides access to the attic. It may not be well insulated or sealed, creating a gap for air leakage.
• Wiring holes: These are the holes where electrical wires run through the ceiling or walls into the attic. They may not be properly caulked or foamed, leaving spaces for air to escape.
• Open soffit: This is the box that hides the recessed lights in the ceiling. It may not be airtight or insulated, creating a pathway for air to flow from the house to the attic.
• Recessed light: This is the light fixture that is installed in a hole in the ceiling. It may not be designed for insulation contact (IC) or air tightness (AT), meaning it can generate heat and allow air to leak around it.

What’s the big deal with patchy snow on my roof?

Patchy snow isn’t a problem per se, but it’s an indication that you have bigger problems, which aren’t as visible. For example:

• Roof leaks: The melted snow can seep through cracks or gaps in your roof and cause water damage to your ceilings, walls, and insulation.
• Ice dams: The melted snow can refreeze on the edges of your roof and form ice dams that block water drainage and damage your roof, gutters, and siding.
• Mold growth: The moisture and humidity from the snow can create a favorable environment for mold to grow in your attic or walls.

If you notice any signs of roof damage, such as sagging, leaks, cracks, or creaking noises, you should contact a roofing contractor as soon as possible to inspect and repair your roof.

What do I do about uneven snow on my roof?

Give us a call at (248) 291-7815, or schedule an appointment for one of our consultants to assess your attic.