Moisture in the attic generally starts from within the home. Many of our daily activities such as cooking, showering, and laundry all create moisture. All of that moisture rises with warm air and then seeps into the attic. Exhaust vents in bathrooms and kitchens are sometimes improperly vented and blow directly into the attic. They should be properly directed to the outside through a roof cap. This mistake in installation occurs more often than you would think! These bath and kitchen exhaust fans are highly effective at removing moisture from the living space. However, if incorrectly installed to vent to your attic, they can cause larger problems with moisture in your attic space.

The heat in your attic may not be visible, but you can see the damage it causes over time. Excessive heat within your attic is not energy efficient and can lead to costly issues in your home.

Did you know that your attic can reach temperatures of 150 degrees in the summer?  Whew, that is hot! The heat in the attic affects your living space making it difficult to cool to a comfortable temperature. That excessive heat can really overtax your HVAC system leading to increased usage and cost. It is really energy inefficient. It’s difficult to appreciate the difference between really hot and even hotter, but small temperature differences can make a big difference.

In order for the attic to avoid moisture issues, you must have a barrier between the living space and the attic. Without it, the warm moist air from inside the house will drift up to the attic. Once that air hits a cold roof deck or surface, it can quickly start to condense. That condensation remaining on the surface is what leads to mold and wood rot concerns. On a really cold morning with frost or snow on the roof, it can be easy to visibly see the difference in attics. Assuming that sunlight isn’t hitting one area more than another, any parts of the roof that have melted snow or no frost are warming up from inside the attic. Any of those spots are places to start looking for a breakdown in that barrier between the living space and attic.

However, the excessive heat creates different problems. Once again, having that barrier between the living space and attic is critically important for energy efficiency. If your air-conditioned cool air is leaking into the attic, then you are just making the HVAC work harder as the cool air escapes into the attic. You don’t want to have an air-conditioned attic. At the same time, you want to limit the heat transfer from the attic to the home to keep the room temperature more comfortable.

Heat and moisture can seep through any cracks or gaps you have between your living space and attic. Fortunately, you can address these cracks and gaps by sealing around them. Energy Star suggests several places you should check for air leaks:
Attic hatches, recessed lighting canisters, HVAC ducts, pipes, and plumbing vent stacks.
Various types of sealants may be required, so be sure to check with a professional if you are not certain of the sealant required for your specific air leaks.

Insulating your attic is another important step to create a necessary barrier between your living space and attic. Proper insulation helps to decrease heat and moisture transfer between attic and conditioned areas of your home. Types of insulation vary by geographic areas and climates.
If your attic has soffit vents, check to make sure that the insulation is not blocking them. This is a common oversight when blowing or upgrading insulation. These soffits are the intake point for fresh air needed for drying and ventilating your attic. When these soffits are blocked, outside air is not entering into the attic sufficiently.

Proper ventilation of the attic is important to prevent air from being trapped in the attic or not exchanged quickly enough. Typically, the intake of air blows in through the soffits and exhausts out through the highest points of the attic in a ridge vent or other rooftop opening. Sometimes, the air blows from side to side through gable vents.
Moisture reduction in the winter happens when the drier outside air replaces the warm moist air. It has to be removed quickly enough to avoid longer term condensation.
Heat reduction in the summer happens when the cooler outside air replaces the hotter attic air. Roofs generate a lot of heat from sunlight that transfers into the attic. The air needs to be exchanged frequently to avoid the heat buildup.

Fans exchange air more quickly than through passive ventilation alone. Fans install across the attic to create distributed and balanced airflow, which is especially important when addressing moisture in the attic. You need air movement in all areas and corners of the attic to move any trapped moist air. It is also important to have balanced airflow to not overpower your ventilation. Ventilation should be using air from the intake points and not pulling air from the living space.