Venting an attic

[xpanmanx]

How should we vent our attic?

We recently moved into our first home, a 1200SF, 1-story, 40-year old ranch in St. Louis MO.

There is an unfinished attic over the L-shaped house. At the peak, the trusses are around

40" tall.

The previous owner had 15" of cellulose blown throughout the attic 6 months before we moved in. We'd rather not disturb the insulation if at all possible.

There are 24"x24" gable vents at each end of the 'vertical' leg of the "L". There is a fine mesh behind each gable vent for critter control. There are no louvers or gable exhaust fans.

There is no gable venting in the 'horizontal' leg, which is a 144SF bedroom (not an addition).

There are no ridge vents. The roof is only 3 years old.

There appear to be soffit vents, but we're not too clear on that. What we presume to be vents are a dozen or more 4"x10" perforated areas in the aluminum siding which covers the eaves. The perforations are too small to see through, so we cannot deduce it the blown insulation is covering the vents.

There is a whole-house fan in the hallway. We love it.

The exhaust fans in the 2 upstairs bathrooms are vented into the attic space via aluminum flexible ducting. The ducts appear to be approx 2' long. They exhaust ends are fastened to the trusses with nylon cable ties, firing horizontally into the gable-to-gable airstream.

How do the experts here recommend that we vent our attic? Best Regards,

Tim ==

[Joseph Meehan]

trusses are around

which covers the

space via aluminum

ends are fastened

You need to address two issues. First get those bathroom vents out of there, vent them to the outside. Venting to the attic is a very bad idea. Next you need to make sure the insulation that was blown in is not blocking the soffit vents, and it sounds like it may be. If it is you have very little effective venting.

Don't worry about power venting. From my experience, in most areas (Mo included) it is not a good idea and not needed.

Other than that, it is a matter of the sizing of the vents. If they are large enough area then you are OK.

As a plus you might want to add a gabble vent over the bedroom.

[Tom Baker]

trusses are around

covers the

via aluminum

are fastened

Tim, First, those bathroom vents must go outside. Extra moisture in the attic is not good practice. I suggest you look at the Building Science Corporation web site. It speaks to attic ventilation in various climates. If you are going to vent the attic, the bedroom wing should also be vented.

Tom Baker Charleston SC