Why is there condensation in my attic?
The primary cause of moisture problems in your attic is due to warm air from the heated portion of your home entering the unheated space in your attic. Heat escapes around cracks and spaces in the ceilings and walls in your home, or from light fixtures, wires, vent pipes and exhaust fans. This warm air condenses on the cold roof sheathing, causing condensation.
If you notice tea colored water stains, or a cluster of black spots on your ceiling, you may have a moisture issue in your attic. There are a variety of reasons why your attic creates condensation, but you may need a professional to determine the precise cause.
The pattern of wetness and staining are usually circular but can change shape based on the origin of the condensation and the slope of the roof. A widespread pattern of moisture damage indicates that the source of the condensation may be a result of airborne moisture. This type of condensation happens when warm, damp air comes in contact with cooler air or surfaces.
In most residential homes, the quantity of moisture in the air depends on the amount of moisture generated in the living area, in relation to the ability of the house to vent the moisture. Common sources of airborne moisture are from the occupants of the residence, plants, animals, improperly vented appliances, aquariums, damp crawlspaces, and humidifiers to name a few.
When a home is properly vented, moisture is removed from the building. Common instruments of ventilation are leakage around windows and doors or electrical outlets, the draft and venting of your heating system, an exhaust fan that is vented to the exterior, the migration of water vapor through a properly vented attic, or through the walls.
When a home is remodeled, and leaky windows and doors are replaced, the ventilation of moisture is reduced. Furthermore, when new vinyl or aluminum siding is installed moisture that would have left the building through small cracks in the walls becomes trapped inside. When a second layer of singles is added to your roof, another moisture barrier is added, making your home retain even more moisture.
Replacing your heating system with a direct vent heating unit, or replacing your hot water heater with a high efficiency unit? This will decrease the amount of ventilation of moisture-soaked air even further and reduces the amount of air exchanged in your home.
The best way to control airborne moisture in a residential structure is to adequately ventilate the attic, as airborne moisture rises. When an attic is adequately ventilated, the moisture-rich air is vented outdoors. An attic may be vented with a gable vent or through vents in the eave that go to the roof vents.
If an attic is not properly vented, the moisture is retained in the attic. In the relatively still air of the attic, the moisture condenses and accumulates on cold surfaces, creating condensation and water accumulation. This can also create frost and is the reason why improperly vented attics will produce icicles on the outside of roof vents.
How much ventilation is enough? Industry standards recommend that the free vent area for attic ventilation be more than 1/150th of the attic area. Free vent area is the open area of the vent, minus the restriction from insect or bird screens. When evaluating the ventilation of your attic, you must also space the vents evenly.
If you have had a new roof installed or plan on installing a new roof, make sure the installing contractor has properly installed the roof vents. Over time, you should examine the vents to make sure there is no blockage or restrictions of air flow. And, you should not cover vents during the winter months, as they are necessary for the proper ventilation of your home and attic.
The most common restriction of airflow in the attic is the restriction from insulation that blocks the eaves. Even when an attic may be properly vented, condensation and mold growth can occur when a bathroom or dryer vent gets disconnected. When the wood in your attic is discolored or delaminated, it is an indication that excess condensation is present
When purchasing a home, it is a good idea to have the engineer inspect the attic, as this is a sign that there may be underlying issues in the home. The degree of moisture stains, corrosion of nails, and the color of the mold growth on the underside of the roof deck, can provide a lot of information about the moisture problems that may exist.
If it is determined that your attic has a mold condition, this could be unsafe for your health. Moldy areas should be evaluated by a professional to determine if additional mold exists in a hidden area or on the underside of the insulation. Mold must be removed, and the surfaces need to be properly cleaned to ensure a safe environment for your family.
The ventilation of airborne moisture from a dwelling is a relatively simple system requiring air intake and exhaust. Gable end vents, a combination of eave and ridge vents, or a combination of eave and roof vents work well unless the air intake is inadequate or restricted, or excessive moisture conditions exist in your home. If your home has sufficient air intake, a power exhaust fan may be a good choice to pull air through your home and out to the exterior.
To ensure the best measure of moisture removal from your home, you should consider increasing the insulation in your attic, and sealing off access points. Insulating the floor of the attic and sealing any openings in the ceiling will keep the heat and warm air in the living space of the home. This will also keep the moisture contained in your home, and out of the attic. Furthermore, it is recommended that all exhaust ductwork that runs through the attic is checked to ensure there are no gaps.
When the hot air that escapes from the living area mixes with the attic cold air, condensation is created, forming a frost inside your attic, when the outside temperature rises that frost inside your attic starts to defrost and that’s the water you see inside.
If you are unsure about the levels of condensation in your attic or suspect there is mold, consult with a professional. Both of these conditions can create further damage to your home and create unsafe conditions for your family.
Max Mannino, President Tri-Star Construction
