Attic Fans or Roof Vent and Prices

[K'ledgeBldr]

It seems this thread became an exercise in futility. Reading the OP is a financial question(s)-

Originally Posted by JOinGA

I was prompted to call a roofer due to a leak at the pipe boot over my bathroom. I have 3 non-functioning attic ventilator fans, so I decided to get a quote to replace them at the same time. I have gotten different recommondations and wildly different pricing from 3 companies. All have high recommendations on Google reviews.

How did it get so sideways? Too much conjecture on a fairly simple process- it's called "convection". Achieving viable convection relies on a certain percentage of air entering a space and a means of as much air escaping the same space. Cooler intake air from a low entry point, warmer (radiantly heated) air escapes through high placed exit point.*


Here's where a lot of people (contractors) get it wrong, the amount of soffit venting doesn't match the amount of ridge venting (I'll use ridge vent since I'm referring to "convection". A perfect example is a tall hip roof- rarely is there enough ridge to properly vent an attic by convection. And just because there is soffit venting doesn't mean it works- or works properly. Cutouts for square and rectangular vents are rarely cut correctly- some not at all! (yes- I've seen it first-hand) Then there's the sloppy install of blown-in insulation, because the contractor or builder cheaped out and didn't install baffles.


The great thing about convection cooling is it's a natural process- as opposed to a power roof ventilator which is a "mechanical" means (mechanical is another way of saying "it will fail at some point"). And the OP has already been made aware of that. With better building practices being employed into new home construction, and better materials, homes today are much more air tight and energy efficient. Trying to achieve the same standard on a house that is 15, 20, or 30yo will never happen- and those that try are exercising their futility.


I have to concur with the OP's final decision, replace the motors on the attic ventilators. When and if the time comes to replace the roof re-evaluate the attic ventilation and make a decision based on confirmed facts. Use BSC (Building Science Corporation) as a "bible" for verified information, procedures, and materials.


*There is also the argument about vented versus non-vented attics (which is not about this discussion)- I'll leave it at this: it works well in some regions (climate zones), and not so well in others.

[NC211]

This right above me, 110%.


I have the setup K' is talking about - vent caps on the ridge line of the roof, vents on the underside of the soffit. Hot air rises. Gets about 150 in our attic on a cooker of a day. What amount of air escapes as it rises, must be replaced with new air that it can pull in through the soffit vents. If the air can't replace itself, it becomes a vacuum situation and the hot air can't escape.

I will give you a a real-world example...me..

We have a side-load garage, 3 car, separate roof structure over that area of the house. However, it does open up to the main attic area of the house. ½ of that space above the garage is floored storage. The other half is the back interior wall of a bedroom. It is an area that, when built, was an option to extend that room all the way across the garage footprint.

Access to the storage area is through the ceiling in the garage, a 4x2 opening that has a wood "lid" type arrangement.

If I open that lid on a hot day - it is like a wind tunnel from below. The hot air trapped in the attic is looking for the ability to replace itself so it can move. The hotter the air, more pressure to escape up through the ridge vents. I am pretty convinced we do not have enough soffit vents, and/or some are blocked. What could it be? Well, it's not the insulation, I've checked. But we had the trim painted two years ago....and some are coated with paint...

What I have done to compensate - I built an open square lid that has a screen crossed it to prevent bees from getting up there through the garage.

The moment I realized this a few weeks ago, the upstairs ac unit almost immediately was able to drop the temp in the house a couple of degrees. Totally made sense to me at that moment, as my fat head was sitting there in that opening in the garage ceiling and my 20 last remaining hairs on it were flying around as the cool air from the garage was rushing past it up into the attic.... The air flow can be so strong that it'll fill up my untucked shirt and accentuate my awesome dad bod........and...you're welcome..