High Humidity Attic

If there is excessive moisture accumulation in your attic it will condense on cold areas mainly on the underside of your roof deck.

High humidity attic.

As planned the r 40 worth of insulation has drastically reduced his heating bill but now he faces another unexpected problem. The dew point and rh get up close to 90 f and 90. If the attic is at 80 f and 80 humidity that s about a 21 torr vapor pressure of water. The dew point and rh stay below 70 f and 70 at their peak the peak of humidity not the peak height in the attic.

If you have high temperatures and high humidity in your attic then you may also have a problem with mold. Freezing and excessively hot outdoor temperatures rain and high exterior humidity levels make it difficult for your attic fan and heating and cooling systems to keep up with desirable attic. During the winter months the recommended relative humidity inside a house is anywhere between 30 50 percent. In contrast the humidity near the ridge in the attic gets very high.

But the humidity near the attic floor never gets out of control. By scott gibson march 18 2019. Jason advani has insulated his attic with spray polyurethane foam and while his heating bills have dropped high humidity remains a problem. So compared to that hot humid attic the vapor pressure at the other side of the foam is a factor of six higher.

Attic temperature depends on the outside temperature and it also depends if your house is insulated. At 140 f 80 humidity corresponds to 120 torr or 16 of atmospheric pressure. Ventilation is another key factor.