Attic Humidity (What Should it Be?)

Excess humidity can damage infrastructure, so it’s essential to know the ideal indoor humidity for different places in your home. This includes understanding the attic moisture.

The attic temperature and humidity should mirror the outdoor temperature and humidity. If the humidity is 80 percent and the temperature 120°F outside, the attic should also be 80 percent humid and 120°F inside.

The best way to achieve this is to install some attic ventilation. You can often use ridge vents to pull hot air out of the attic. You can also try passive vents that allow heat to escape on its own.

But if those attic vents aren’t cutting it, you may need another option. Read on to learn more about what you can do to keep your attic in perfect condition. 

attic floor boards and insulation

Are Attics Humid?

Yes, attics are usually humid. This is primarily because warm and hot air in your home naturally rises into your attic space from the lower parts of your home.

Hot air always rises because it is less dense than cold air. Hot air also holds more water than cold air, so heat and moisture in your attic space are inevitable. All you can realistically do is mitigate some of the impacts (like mold growth) using proper ventilation. 

Why Is My Attic So Humid? 

Other factors that contribute to the humidity in your attic are showers, dishwashers, dryers, cookers, washing machines, baths, humidifiers, and other heat-producing machines. 

Not only are all of these familiar heat sources in your home, but they are also sources of moisture.

The roof, which is directly above your attic, is also the part of the house most exposed to the sun over the course of a day. That heat has nowhere else to go but into your attic space.

humidity in attic

Other factors also determine the humidity in your attic, such as:

  • Piping, which either sweats or leaks inside your roof space
  • Water in the foundations of your home, which evaporates and finds a way into your attic space over time
  • Your area’s climate

All of these things contribute to excess moisture buildup in your attic. Heat and excess together contribute to increased humidity.

What Should Attic Humidity Be?

While attic humidity is inevitable, it should never be any higher than the humidity levels directly outside your home.

Humidity levels in your attic will generally range from 30 percent to about 60 percent, depending on the time of the year.

What Should Attic Humidity Be In Winter?

The humidity level in your attic during the winter months should never exceed 40 percent, and it usually never drops below 35 percent. 

When talking about humidity, many of us immediately associate it with heat. But excess moisture can actually be a bigger problem during the winter months.

Because the temperatures outside are usually colder during the winter, condensation becomes an issue on cold wood surfaces, metal nail heads, and piping, all of which generally feature pretty prominently in your attic.

The problem emerges when those surfaces are left wet for a sustained period and start to rot or deteriorate.

What Should Attic Humidity Be In Summer?

attic humidity be in summer

The humidity level of your attic during the summer months should never exceed 60 percent and usually doesn’t drop below 50 percent. During the summer months, your biggest enemy is the heat. 

All that summer heat starts to build up directly under the roof deck during the day, carrying more moisture into your attic than the winter cold does.

To combat this, you will need a cooling solution such as an air conditioner. However, air conditioners also carry higher costs than nonelectric attic ventilation.

Attic ventilation systems for your home are always the better option when dealing with moisture issues, heat, and excessive humidity. However, there are other options, too, like an attic fan humidistat.

What Is The Ideal Attic Air Temperature?

The heat in your attic should never exceed 130 degrees Fahrenheit during the summer months. In addition, your attic during the summer months should never be more than 10 or 20 degrees hotter than the temperature outside your home.

During the winter months, your attic heat should not drop below about 60 degrees Fahrenheit.

What Is An Attic Fan Humidistat?

An attic fan humidistat is a device attached to your home heating and cooling systems that automatically adjusts the moisture levels in your home’s air

While the humidistat is triggered automatically, you have to make the adjustment settings manually—the same way a thermostat would work with your air-conditioning system. 

These settings give you more control over the humidity and indoor temperature.

What Should Attic Fan Humidistat Be Set At?

Your standard attic fan humidistat will have a maximum operating humidity of about 90 percent, while the minimum operating humidity will be about 30 percent. 

The general goal is to have the attic fan humidistat run about 60 or 70 percent, which ensures adequate ventilation in your attic while also avoiding the prospect of the fan running continuously.

Should You Put A Dehumidifier In An Attic?

Yes, you could try a dehumidifier in the attic to help reduce the amount of moisture in the space by absorbing it into a tank. Effectively, dehumidifiers pull out excess water from the air around them. 

There is one significant drawback with a dehumidifier, though: It requires regular attention because the storage tank fills up with water quite fast. 

This is a crucial maintenance task because a full tank can not draw any more moisture from the surrounding environment.

Does Insulation Help With Humidity Control In Your Attic?

Insulation helps humidity control in attic

Yes, insulation will help with humidity control in your attic by reducing moisture buildup. This insulation can help prevent things like mold issues.

Insulation minimizes the transfer of heat in your home and attic, which has a positive impact on heat levels in your attic. It is important to install attic insulation properly.