Insulating the duct may also help.
Hvac is venting into the attic.
The high humid air doesn t vent out of the house before it condensates in the duct and then runs back into the house causing damage.
Roof vents allow for natural attic ventilation but mechanical solutions are also available.
A lot of people opt for a whole house dehumidifierafter spray foaming their attic.
For good attic insulation one square foot of ventilation is recommended per every 300 cubic feet of space within the attic.
Venting a homes attic is a very important best building practices will say 50 at the ridge and 50 at the soffits unobstructed.
Or you may have a distance issue.
To better manage the higher humidity resulting from shorter ac run cycles the whole house dehumidifier removes moisture from the home until it satisfies a humidistat setting typically something between 45 and 55 relative humidity rh.
Fresh combustion air for the furnace is coming from the soffit vents from both roofs.
The most common vents are.
There are two basic types of attic fans.
Rooftop fans and gable fans.
You may have a bad boot around the roof vent that is leaking into the attic.
A 1 1 ratio of intake and exhaust vents is needed to ensure proper airflow through your attic.
Box or dome vents these static vents are installed directly into holes cut into the attic roof.
Do not use mechanical means electric attic fans.
However the furnace is in an attic space which has no venting for warm humid air from house from soffits from hot roof etc to escape.
A furnace in the attic is a design that works for all homes.
No you shouldn t use a towel or other absorbing material.
Unless you plan to convert your attic to a living space it doesn t make sense to seal it and route your hvac vents up there.
Exhausting air into the attic will create a negative pressure situation you will be bringing in a lot of outside air to make up what is being exhausted into the attic this could raise your heating costs and lower the relative humidity also if there is a window in the room open it slightly while the fan is running so all of the outside make up air will come directly into the room instead.
Ridge vents these vents are installed at the top of a sloped roof and are commonly used on shingled homes.
Unless you have a slab where the equipment would likely be in the garage venting can go directly through the roof instead of routing through an exterior wall making it much easier to install the duct work along the upper floor.
The furnace has a stack which penetrates the flat roof and is about 3 4 above the roof plane.