Attic frost is the accumulation of frost or ice on surfaces in a building’s attic, typically on the underside of the roof deck and any air ducts or pipes. This phenomenon can occur in cold climates during the winter months when outdoor temperatures drop below freezing and warm, moist air from within the building rises into the attic and comes into contact with cold surfaces.

The moisture in the air condenses into frost or ice. That’s no good thing for your home and can cause a variety of issues that need to be rectified quickly if you want to avoid a costly roof replacement.

What Causes Attic Frost?

A variety of factors can contribute to attic frost, but temperature fluctuations are one of the most common. When the outside temperature drops unexpectedly, the warm, humid air inside your home rises to the attic. Once in the attic it condenses and freezes against the cold wood of the interior roof. This is especially common in older homes built prior to the implementation of proper building codes that were introduced to prevent this issue.

A lack of proper ventilation and insulation in the attic can also contribute to attic frost. If the attic is not properly ventilated or if there is a problem with the vapor barrier in the ceiling, humidity, and condensation issues can arise, causing frost to form. This is especially true if you recently completed a DIY insulation project that blocked attic ventilation access or if you live in an area with extreme weather.


Proper ventilation is essential for keeping an attic healthy. Check your attic for insulation that is blocking the soffit vents. Air baffles should be installed on the roof deck of the attic to allow air to circulate from the soffit. You can check the ventilation by entering the attic with the lights turned off and your eyes closed for 30 seconds, then looking for light around the edges of the roof. If you can see light coming through, the ventilation is most likely adequate.

For good airflow, the attic should also have a ridge vent or a similar design, such as a ‘Maximum’ vent at the top. If you can, avoid gable vents. These vents neglect the roof peak. If you can’t avoid using them, it’s best to seal them and add a vent at the top.


The humidity levels in your home can have a significant impact on the formation of attic frost. It is critical to minimize the relative humidity of the air in your home if it is too high. Over 50% relative humidity (RH) is considered high and can cause condensation and frost in the attic.

Use bathroom and kitchen fans when showering and cooking to reduce humidity in your home, run a dehumidifier in the basement if necessary, and avoid hanging laundry to dry indoors.

In summary, keep an eye on humidity levels in your home, make sure your attic is properly ventilated, and make sure your ceiling vapor barrier is intact and functioning properly. Addressing all of these issues can help you avoid problems caused by attic frost, such as roof structure damage and decreased insulation effectiveness.

How To Fix Attic Frost

There are, thankfully, a number of solutions that you can attempt in order to reduce attic frost within your home. Some are simple roof repairs, others are more preventative.

Avoid Using Humidifiers

Humidifiers are specifically designed to deliver moisture into the atmosphere. You should avoid using them during colder conditions and winter. This will stop humidity from reaching the attic and building up over time. If you have bathroom and kitchen extractor fans, run these for longer than you would normally to remove humid air.

Check Your Roof Condition

Unless you are a professional roofing contractor, it’s definitely worth your while to have your attic properly inspected. A professional will be able to confirm if there are any issues, suggest maintenance regimes, or assist in repairs. Most contractors will be able to assess areas that might be susceptible to frost. They could then seal any bypasses.

Replace Old Insulation

You could attempt to replace old insulation yourself, but it’s definitely a task that you should consult with a professional on. If you’re already struggling with attic frost, you might want to consider using spray foam insulation instead. This insulates and seals all in one go, saving you a job.

Have An Energy Audit Completed

A professional energy efficiency audit can also be a valuable preventive measure. These audits are simple assessments that help you identify inefficient areas in your home. Given that each home is unique in terms of age, size, and construction material, this test allows the contractor to recommend customized solutions that are best suited for your specific home, or provide a realistic quotation for a new roof.

Don’t Simply Add More Insulation

Unfortunately simply adding more and more insulation won’t have the desired effect. It is vital to first address the issue of attic air sealing. Adding insulation to a poorly sealed attic can aggravate frost problems by trapping moisture-laden air within it. Prioritizing air sealing over insulation will help to keep moisture and frost out of the attic. If your budget only allows for one solution, choose air sealing over insulation.

Key Takeaways

Tackling the issue of attic frost can appear challenging, and certainly, the best solution is to take preventative measures before the issues actually arise. If it’s too late, take time to assess the problem with the help of a professional and you should be rid of the frost in no time.

  • Attic frost typically affects older buildings that were constructed before building codes were implemented.
  • Professionals will help you to work on repairs and further preventative measures.
  • Always prioritize ventilation over insulation.

Taking the time to speak with professionals like our team at Fahey Roofing Contractors is worth it. We’re one of the best roofers in Morgantown, WV, so get in touch with us for an estimate.