Roof Vents

I have a fairly steep roof. Do I need to use "slant back" vents or would box vents be okay?

Hello Balley, welcome to the Forum !

Just off hand, I'd say which ever one has the lowest profile, given you probably get a lot of Snow up there.

Wouldn't hurt if you were to give us a URL of both of the ones you're considering, and we can go from there.

Have a good Day !
S.W.

Hi Balley, welcome to the forum As SWHouston says

I am looking at vents made by this company
http://www.duraflo.com



Edit:
Slight correction made to URL,
S.W.

Post edited by: SWHouston, at: 2008/08/11 05:50

Balley,

Looked at the URL you provided, and the product line is pretty standard.
You can see that there are several types of ventilators, and all will work quite well, when you find how many Square Feet your Attic space is, then select the amount of ventilators required to vent that.

I previously recommended a low profile, given you live in Canada, and are probably prone to get some substantial Snow falls. The Ridge Vent they have, is the lowest profile available, and requires about 80" of vent, for every 250 SqFt of area. What's the total leniar footage of your Ridge?

How many square feet of Attic do you have?

You should consider your Soffets also, if you can't get the air in, you can't get it out. How are your Soffets set up, I need some SqFt on them too!

IF you're concerned about not being able to describe it very well, how about some pictures then! We'll take a look and go from there!

Given my location (Houston Tx) I had to use a combination of Ridge and Turbine, just didn't have enough Ridge to get the air out, and bumped the flow up with three additional Turbines, that's an option which you may not need at your Latitude, but doable.

Took a look at the Square and Slant Back they had, and I'm not saying they wouldn't work, they will, but, I wasn't very impressed with either, but of the two, the Slant Back would be preferred. In either case, you'd need several of them, to get the air moving well on an average size house.

Have a good Day !
S.W.

Post edited by: SWHouston, at: 2008/08/11 06:40

2169 sq ft bungalow. 30 X 33 ft attached garage. Very chopped up roofline. No roofers up here are using ridge vents. I have 6 slant back vents located at the peaks. No vents on the garage (its not heated or insulated). Soffits are perforated aluminum all around. My current venting meets the local codes but local roofers want me to double the venting to reduce summer attic temp. Does reducing attic temps prolong asphalt/fiberglass shingle life? I'm getting alot of mixed messages about this.

Balley,

Good info, now i got the picture !!

From what i see on their calculator, you're a couple vents short.
That's not much, and given the irregularity of your roof, you'd have to very crefully place the next two, to get real benefit out of them.
But to DOUBLE the amount of vents....Ummm, not too sure about that!

You can't have TOO much ventilation in an Attic, BUT, just where's the point of deminishing returns? Sounds like they need work, but not near as much as they say.

If you decide to add a couple or three on the house, i'd have them put one or two on the Garage too. That being for your own personal comfort, when out there in hot weather.

Asphalt thrives on heat, can even RE-seal it's self sometimes after a hail storm, IF you can wait till a hot day ! Deterioration usually comes from the elements, repeated cold-hot and being washed by Rain. IF heat was a culprit, they wouldn't warranty them for 20/30/50 years.
So, adding vents because of that, is making me think they're sorta using a costly roof replacement, as leverage to get the job.

That's two (2) exaggerations, see where it's going here !

You are NOT in bad shape, just like you are, and given how short a time it is to cold weather, rushing to get anything done now, wouldn't be prudent.
SO, let's do a test, and see just what shape you really are in !

Outside air temperature in the shade, is called Ambient Temperature.
Buy/put a Thermometer in your Attic, near one of the Vents, where it will sense the total air temperature up there. You might move it around to other Vents, just to get an average. Make notes, be sure to check it during the hot part of the day.
Hang it by a cord about two feet above your insulatioin/floor, don't place it up against/near a hot surface, Or in the case of a limited area, about hslf way between the insulation and rafter.

IF you can see a differential of 15° or less, then it will be very unlikely that additional vents will do any good at all. ( Attic° - Ambient° = ?° )

I'm really surprised that Roofers aren't using the Ridge Vent up there!
It's a very efficient way to get the hot out, and literally "hides" on the peaks of your roof. It's something you might consider, leaving the Vents as they are, and installing a few yards in the areas away from the vents, to catch those low flow areas. Labor cost for Ridge probably will be a bit higher than just another vent or two.

SO, if I were you, I'd "cool it", and gather some information first, before I jumped into this. IF you decide to add more ventilation, do it in the Spring of next year, you've got time to evaluate this.

Have a good Day !
S.W.

Post edited by: SWHouston, at: 2008/08/12 17:11