Renovations are rarely done to 100 per cent completion.
Often referred to as the “half-assed syndrome”, basic repairs falling somewhat short of their logical conclusion, unfortunately happen when a human being, usually male in gender, and without proper supervision, is given the task.
Why does this standard shortcoming exist? Because it’s human nature to be satisfied by how things look, as opposed to checking out what’s under the hood.
The renovation biz is no different. Limited funds, or limited knowledge on the part of the installer, often result in the replacement of the fixture, while kind of forgetting, or dismissing, the guts of the issue.
Case in point; new homeowner has two questions concerning the ventilation in the attic of his recently purchased 40-year-old home.
First inquiry. My 1,600 sq. ft. bungalow has one Maxi-vent on the roof, along with a 16-in. octagon vent on both gable ends, so is this providing enough attic ventilation?
And, there are two lengths of 4 in. insulated pipe attached to a bucket just under the Maxi-vent, one leading to a vent in the hallway, with the other directed into the bathroom.
So, do I just leave the vents as is? Or, can I simply close the vents, detach the insulated pipe, and let the ductwork rest on the attic insulation?
Unless otherwise specified, most homes (whether they’re new or older) are being roof vented with the Maxi-301, square (chimney like) unit.
The Maxi-301 is an exhaust vent that’ll handle 1,200 square feet of attic floor space. Therefore, in this gentleman’s case, his existing unit is going to be a little overwhelmed.
What about the two octagon gable vents, don’t they help out a bit? Not really. Gable vents work relatively well to let air into an attic, but because they’re placed on a wall, do little to effectively extricate attic air.
As a result, and in this fellow’s case, he’s got sufficient soffit and gable venting allowing fresh air into the attic, with an undersized amount of roof venting. Solution, add a second Maxi-vent.
Now, Maxi-vents come in a number of sizes, including the aforementioned #301 model, handling 1,200 sq. ft. of attic space, the #302 model (500 sq. ft.), and the #303 Maxi (800 sq. ft.). In this case, and needing only another 400 sq. ft. of air drawing capacity, the fellow could add a #302 Maxi to satisfy the attic’s needs.
However, Maxi’s differ in height between models. Therefore, since it would no doubt look a little odd to have two different size of Maxi units on a roof, even if they were separated by a reasonable spacing along the ridge, I suggested he either add a second #301 model, or forfeit his existing unit for two #303 models.
Can an attic have too much ventilation? No, only too little.
Next, what are those two lengths of insulated ductwork doing there? They were part of what would now be considered an antiquated, and inefficient air withdrawal system, known in those days (and we’re going back 20 years or so, as a Venmar).
Basically, a turbine (located where the Maxi vent is now) would (based on wind velocity) draw air out of the home.
Flaws to the Venmar strategy? The system had no brain, drawing air out at an arbitrary rate, with no fresh air intake.
Plan of action, and what should have been done in the first place? Eliminate the bucket and two lengths of ductwork. Next, remove the two Venmar ceiling vents (blocking or closing them is not good enough), repair the drywall, then on the attic side, cover the repair with a clear 6 mil. poly, adding insulation overtop.
Sealing the attic’s air space from any type of warm air infiltration is key to avoiding condensation and mold. Next, invest in a HRV (heat recovery ventilation) unit.
In this case, the gentleman already had a forced air furnace, making the investment in a humidity controlling, air quality unit such as a HRV, an easy partnership.