Attic Humidity In Winter

Eliminating mold and mildew on the roof structure is the ultimate goal.

Attic humidity in winter.

To start frost accumulates when moisture laden air from the house gets into the attic. Advani hopes to finish the attic and install a minisplit although he s not sure that will lower the humidity. Our main concern in the winter is moisture. Quelch the heat wave.

Hot summer weather poses the opposite problem for maintaining recommended attic temperatures. Here is a link to an article that describes the work. When it comes to humidity you would be best to have the levels below 50 to avoid mold growth and structural rot. Only about 10 of the hip roof is shaded so it gets plenty of direct sunlight.

So the first step is to seal the air leaks. The results are that the attic temperature is close to the outside temperature but the relative humidity is significantly higher in the attic than either the indoor or outdoor readings. Winter air is by nature not humid so the problem must be condensation related. During winter months humidity from this escaping air can condense on cold attic surfaces leading to mold.

Air sealing an attic. That s about it pretty simple. In winter the humidistat operates the attic fan when the relative humidity exceeds a preset level usually 40 to 50. This reduces attic moisture.

Ideal attic temperature and humidity settings cold outdoor temperatures affect attics. High humidity in an attic is usually caused by air leaks in the ceiling of the top floor of your house. In summer the thermostat operates the fan when the attic temperature reaches a preset level usually 90 to 95 degrees f. When moisture gets into the attic it condenses on the roof sheathing in the form of frost.

If there is excessive moisture accumulation in your attic it will condense on cold areas mainly on the underside of your roof deck. With outside temperatures ranging between 5 f and 95 f attic temperatures range between 48 f and 92 f. Sealing the attic shut for the winter appears to effectively stop the air flow the major source of moisture accumulation. Some initial moisture will leak in but with no air escaping from the attic neither air flow nor air changes it will soon stop leaving only a light frost on the underside of the roof.

Frost itself doesn t do any damage but once it melts things get wet and then damage occurs.