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-   -   Ventilation option.... (http://www.diychatroom.com/f9/ventilation-option-25280/)

seppainter 08-15-2008 11:51 PM

Ventilation option....
 
Hello all, i have a customer who would like to get more ventilation through her roof from her attic. There is one gable vent for an attic size of about 2800 sq. ft. At the other end of the attic is a wall and cathedral ceiling leading into the rest of the house, hence having only one gable vent. There are no soffits to be vented. So, my suggestion is going to be to put in a turbine vent in the middle or more towards the wall/cathedral ceiling. I figure this will be relatively inexpensive and do a pretty good job in more ventilation. Am I correct in my figuring and assumptions? Any information would be greatly appreciated. thanks.

steve-the painter....

Ed the Roofer 08-16-2008 12:22 AM

That or a Solar Powered Vent, like the one made either by Air Vent or GAF/ELK.

This only qualifies if she truly does not have ANY soffit ventilation, as that would be the most help,

Also, a continuous Shingle Vent II Ridge Vent, which would only require the removal of the existing Ridge Cap shingles and then cutting the slot and then installing the Ridge Vent and then nailing new shingle cap on top of it.

Make sure to use 2 1/2" to 3" long roofing nails for the installation of the Ridge Vent and also the Shingle Cap.

If you really want to offer a better remedy to her hot attic problems, then this is a much more viable solution.

Ed

seppainter 08-16-2008 01:13 AM

thanks for the quick reply ed, i wasn't sure about doing a ridge vent without soffit vents. i thought the turbine vent would provide more ventilation, she does have a lot of open space around here house, in a somewhat rural area, so wind is not an issue and from what i read the turbines transfer quite a bit of air out of the attic.

Ed the Roofer 08-16-2008 09:38 AM

Quote:

Originally Posted by seppainter (Post 149093)
and from what i read the turbines transfer quite a bit of air out of the attic.

A standard sized Turbine, or whirlybird vent provides 250 square inches of NFVA.

14 1/2 feet of Shingle Vent II would be equal to that approximately.

I would assume that her Ridge Line is longer than 14 feet, so the Ridge Vent would not only provide more Exhaust Ventilation than the turbine Vent, but also will be located at the peak of the roof and will exhaust evenly for the entire length, plus it will increase its performance with as little as a 3 mph wind, due to the Bernouli Effect from the air blowing over the windward and the leeward sides of the vents external wind deflecting baffle.

Ed

seppainter 08-16-2008 09:59 AM

thanks again for your response ed, i had been reading that a standard 12" turbine can remove 347 cubic feet of air per minute and a 14" can can expel up to 1,342 cfm of air in a 15 mph wind....these numbers just sound big to me. And, I am not a roofer, but a carpenter friend of mine thought the turbine would be easier and as or more efficient than a ridge vent. I am guessing, but I would say there is about 20-25 ft. of roofline where it could be vented.

Ed the Roofer 08-16-2008 02:33 PM

Those numbers you quoted are for a PAV, a Powered Attic Ventilator, or Roof Top Exhaust Fan, which chews up Energy like crazy. It has been proven by the Utility Companies as a fact.

The most cost effective method would be a Passive Ventilation System, unless you found a whirlybird turbine air forced revolving fan that actually and truly provides those numbers.

Check out the site at www.AirVent.com and look up the different exhaust vent options for the actual true numbers for yourself.

Ed

seppainter 08-16-2008 07:26 PM

hi ed, i got those numbers from like 3 different websites. one of which is this one:

http://www.askthebuilder.com/442_Roo...ne_Vents.shtml

if in fact they do expel that much hot/humid air would it be a better way to vent the attic? my customer's first choice was to get a powered vent and i talked her out of that, so i am definitely looking at passive ventilation. I really appreciate your time on this. i trust my carpenter in saying that the turbine vent would be good, but i wanted to get some other input on this as well.

steve

Ed the Roofer 08-16-2008 09:50 PM

Okay, you really were speaking of CFM instead of NFVA.

I typically see those turbine vents not moving due to rust or other environmental conditions or mechanical problems, such as the ball bearings wearing out, but as far as the "Initial" functionality, they work quite well.

Also, you seem set in your mind that this woulf be the better alternative, although I would not install them, so ffeel confident in your decision, at least for about a 5 year period of time.

Ed


http://www.airvent.com/professional/...windTurb.shtml


http://www.airvent.com/professional/...nd-specs.shtml


Shttp://www.airvent.com/professional/products/staticWind-specs.shtmlpecifications
Airhawk® Wind Turbines



SizeTypeDescriptionColor12"AluminumInternal brace
with baseMill, Black, Brown, White and Weatherwood12"AluminumExternal brace
with baseMill, Black, Brown and Weatherwood14"AluminumInternal brace
with baseMill, Black, Brown, and Weatherwood
HOW MANY WIND TURBINES DO I NEED?
Use the chart below to determine the number of wind turbines you'll need for various attic sizes.
Attic Square
Footage
12-inch Wind
Turbines Needed
Attic Square
Footage
14-inch Wind
Turbines Needed
Up to: Up to: 130021700218003220032400428004


Now some information about Gable Vents:

Wall Louvers

Wall louvers are installed in the gable end of the attic. The higher they are placed, the more effective they become as exhaust vents. Wall louvers are not preferred for ventilating an attic, because they provide limited airflow under the roof deck, resulting in "hot spots."
http://www.airvent.com/professional/...ectangular.jpghttp://www.airvent.com/professional/images/clear.gif
Rectangular Wall Louvers
  • Aluminum construction
  • Flush flange
  • Mill finish or Baked White Enamel
  • Sizes: 8" x 8", 8" x 12", 12" x 12", 12" x 18", 14" x 24" and 18" x 24"
Benefits:
  • Can be used where ridge vents are impractical, or where the homeowner doesn't want roof vents
Design Considerations:
  • Adequate soffit venting must be used to meet typical ventilation code requirements
  • If used in place of soffit venting, two louvers of adequate size should be installed on each end of home
  • Must be placed high to be an exhaust vent
Specifications

seppainter 08-16-2008 09:57 PM

Like i said, i'm not a roofer or a carpenter, just a painter with some basic handyman skills. i'm not really set on anything, or i would not have bothered to join this forum and ask. the carpenter i have enlisted to do the job said it would be good, but he also mentioned a ridge vent instead. but, then i see those numbers that sound big to me, and i'm thinking that might be the way to go. to be honest, i don't even know what NFVA means and when i googled it i didn't really find anything to explain it. i guess i will chat with the carpenter again and make a final decision. thanks for your input though.

Ed the Roofer 08-16-2008 10:56 PM

NFA or NFVA both are the same thing.

Net Free Ventilating Area.

This is the tested or stated amount of Net Free Air that can either enter or exit a ventilation device on its own merits, not including any additional forces. (Like, the Shingle Vent II with the External Baffle.) It draws more air out from as little as a 3 mph wind.

All ventilation products are rated either in NFVA or CFM.

The total area of the attic footprint, or floor space is used to determine the properly calculated amount of necessarry Intake and Exhaust Ventilation required.

If one of the two vents in the equation, either the Intake or the Exhaust, are missing from the scenario, then the amount of NFVA from the remaining product must be doubled to adequately meet the minimum code and FHA established guidelines.

Ed

seppainter 08-16-2008 11:01 PM

ok, well, thanks for the info and your help...

steve

Ed the Roofer 08-17-2008 12:34 AM

You are welcome.

I hope the information helped you out in making an informed decision.

Ed

seppainter 08-17-2008 08:40 PM

hi ed, i am back again....i was over at the job site today and realized a couple of things.. the ridge is only 14 feet long and there is a satellite dish about 5 feet from the gable right attached right up at the ridge. so, either we would have to run just a short 9 foot ridge vent, or run two vents, about 9 and 4 feet..moving the dish doesn't seem to be an option. would you still suggest the ridge vent over the turbine? thanks..

steve

seppainter 08-19-2008 09:05 PM

One more question, please....
 
hi ed, i am back again....i was over at the job site today and realized a couple of things.. the ridge is only 14 feet long and there is a satellite dish about 5 feet from the gable right attached right up at the ridge. so, either we would have to run just a short 9 foot ridge vent, or run two vents, about 9 and 4 feet..moving the dish doesn't seem to be an option. would you still suggest the ridge vent over the turbine? thanks..

steve

Ed the Roofer 08-19-2008 10:54 PM

Quote:

Originally Posted by seppainter (Post 149086)
There are no soffits to be vented. So, my suggestion is going to be to put in a turbine vent in the middle or more towards the wall/cathedral ceiling. I figure this will be relatively inexpensive and do a pretty good job in more ventilation. Am I correct in my figuring and assumptions?


It is primarily due to this, plus that the Ridge Venting is passive and continually works that I still recommend the Ridge Vent.

You have to view each individual set of enclosed rafter bays as individual contained air pathways.

Any other vent product, unless multiple ones were installed on top of each rafter bay would not be able to evacualte the internal heat and humidity from the remaining rafter bays.

An Intake Ventilation Upgrade is seriously needed to improve the actual flowage too.

Ed


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