High Humidity Attic

In contrast the humidity near the ridge in the attic gets very high.

High humidity attic.

If the attic is at 80 f and 80 humidity that s about a 21 torr vapor pressure of water. So compared to that hot humid attic the vapor pressure at the other side of the foam is a factor of six higher. Attic moisture usually appears because of condensation. If there is excessive moisture accumulation in your attic it will condense on cold areas mainly on the underside of your roof deck.

But the humidity near the attic floor never gets out of control. 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. Jason advani has insulated his attic with spray polyurethane foam and while his heating bills have dropped high humidity remains a problem.

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

As planned the r 40 worth of insulation has drastically reduced his heating bill but now he faces another unexpected problem. That s way too high. Jason advani jason advani thought he was on the right track when he insulated the bottom of the roof deck in his walk up attic with closed cell spray foam.