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Question DetailsAsked on 8/23/2014

I have ridge vents in my roof but it is still very hot. Can I also install turbine vents?

My roofer talked me into switching from turbine vents to ridge vents when new roof was installed last year. Also he told my I did not need both. My attic is hotter than ever and am wondering if I couldn't also install turbine vents.

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4 Answers

2
Votes

Turbine vents will pull attic air mainly from the area that they are insatalled at, not evenly from all areas.


Check to see if your soffits are vented , as ridge vents pull air from the soffits, they need to be well vented between each truss or joist. Perforated aluminum soffits are the most common in newer homes, they can become partial cloged over many years.


Not saying, not to use turbines, but ridge vents should be better. Also check to see the cut the roof deck at the peak, so the ridge vents can "breathe".



Source: www.bayareacool.com

Answered 5 years ago by BayAreaAC

2
Votes

There is no reason you could not install turbine vents. Don,y really know why but in my experience they do seem to pull more air even though they are not as good at venting all bays of the rafters. They seem to pull air from below the lower edges of the rafter and I would bet that a smoke test would prove this. The ridge vents tend to prolong the life of the roofing and the roof sheathing better though. One thind I have witnessed on actually my own home and not a customers is how the two react in a fire. One section of my house had old turbines and the newer addition had a ridge vent. When the fire hit the roof area with the turbines the fire went straight to the vents and the ridge stayed intact. The newer section with the ridge vent the fire ran right down the ridge and caused a collapse of the roof and then the second floor ceiling in one part hitting one of the fireman inside. I would still recommend ridge vents though as they do a more complete job.

You might want to consider solar powered roof fans as there is no wiring invoved just like the turbines.


Don

Answered 5 years ago by ContractorDon

1
Vote

The other two commentors made a number of good points, as usual. Unless you are in a VERY hot area with zero wind and direct sun angle on the roof, your ridge vents should work better than a few unpowered turbine ventilators, overall.


I would check to be sure that you have a LOT of eave/soffit open area - your eaves (and any eave baffles) should be open pretty much full width opening between the rafters, and at least 4 and preferably about 6-8 inches clear vertical space under the sheathing, with no insulation obstruction. Soffits should ideally have pretty much continuous baffle perforations - I have found the ones that are perforated with lots of small (1/8" or so) holes have far too much resistance to airflow and do not work well. Of course, soffits in general, while they pretty up the underside of the roof overhang and are good protection against swallows and bats and wasp nests and such, are NOT good for your attic ventilation. For proper ventilation, your eave/soffit intake area (and ridge vent exhaust area) should be about 1/2-1% of the roof surface area. (Industry standard is 1/3% or 1/300th of roof area, but more recent studies have shown this is far from adequate for good attic ventilation). For a normal roof running say 20 feet on slope from overhang to ridge, this means bare minimum 1.25" airgap at the eaves and at least 15 square inches of ventilation opening per running foot in the soffit - which is about 1200 1/8" holes per running foot, so you can see the smalll perforationg soffits are FAR from adequate airspace.


The second thing I would do is check you actually have a properly installed ridge vent - the opening through the sheathing from below should be continuous or nearly so for the full length of the ridge (and along the top portion of gables on hip roofs), the underlayment (water barrier) needs to be fully cut back in that slot, and there should be free airflow through the ridge vent itself. The cheapest ones just use a plastic mesh like a large brillo pad, and some brands really restrict the airflow to nearly nothing - the best ones have wide open airflow pathways, with louvers or baffles to prevent blow-in of snow or rain or leaves. Looking up from underneath, you should be able to see clear light in the cutout area - if it is dark, you undoubtedly have poor airflow too.


If your ridge vent and eave/soffit areas appear to have good airflow capability but are not doing the job, then you certainly can do several other things to increase attic airflow:


1) install turbine ventilators at the hottest areas, though generally it seems they only pull from at most 3 rafter bays in width - the one they are installed in, and one each side at most. There are (I don't remember the company name offhand) special baffles designed to mount on the underside of the rafters that have lips that funnel airflow into the baffle, which is shaped sort of like a flattened funnel or scoop, and direct it directly up into bottom of the turbine vent hole. The ones I have seen in the past were 10 feet wide, so collected from five bays into one. They are designed to go below either turbine or plain roof vents. However, in winter they DO tend to make that area a hotspot in the roof, so you get glaciering downslope of the vent due to snowmelt refreezing on the roof, so I wouldNOT use them in areas with significant (say mor than 3-4 inches at a time commonly) or winter-long snow buildup.


2) powered vents scattered acrosss the roof of course can help - I do not think anything of the solar-powered ones with the panel mounted right on the ventilator - the amount of airlflow is miniscule, so they are like a hood ornament - look pretty, do nothing useful in my opinion.


3) increase the ridge vent airflow. I have (for winter heat buildup, but same effect) installed air collector piping below the ridge, pulling hot air and increasing overall airflow to the ridge into standard PVC perforated 4 or 6 inch drain pioe - the kind with the large (about 2 inch (?) holes every 6 inches or so, with the exhaustof the pipe being either with a powered thermostaticallycontrolled duct fan at the ends (pulling and exhausting through both ends), of passive ventilation using riser pipes up through or near the ridge to either hooded (furnace exhaust ducts or into raised cupola or celestory vent. If vented through vertical duct the cap has to be either a windvane type or anti-backdraft so any breeze does not blow down into the duct and cause stalling of the airflow.


4) put in large-capacity power louvered gable exhaust fan on what is normally the downwind end of the house. Normally, gable vents or fans are not recommended for use in conjunction with ridge vents, but in a case like yours (or like some I worked on in the Mojave Desert), sometimes you have to brute force it. If thermostatically controlled, with electric louvers so they are closed when the fan is off, the additional airflow can remove a lot of air from the attic when needed due to excess heat. It takes a large fan (thousands of cfm) to work like this, and may take one in each end of the house as they obviously tend to pull more from the area near them than towards the center of the attic unless you build a duct or plenum down the length of the attic about halfway up the roof (to avoid pulling a lot of air directly from the ridge vent). In large commercial buildings with hot roofs (usually flat or low-slope roof), it is not uncommon to run a plenum (a large box duct) with openings every few feet the length of a hot roof, evacuated by a large fan to the outside. Obviously this solution adds power demand and generally need cleaning of the blades and motor and louver screen every year or so, and of course the motors wear out every 5-10 years typically, so should be a last resort.

Answered 5 years ago by LCD

0
Votes

Turbine vents are the LAST effort to be made & the LEAST effective, sorry.


1) If you have NO soffit area in which to install an abundance of vents

you might consider ripping off some fascia, replace this with a venting fascia such as Fypon offers

however

GAF makes a hip vent, if you have plenty of these


2) If you have gables, then vent these, once soffit vents are installed


3) 2nd to last effort would be the super expensive solar cap vents BUT thye offer no research/studies to indicate the minimum 7 year energy payback, no guaranty they last 7 years w/o repairs, so wait for a sale.


4) when re roofing comes around, consider galvalume roofing but if too costly, always choose the lightest/reflective shingle ... but not so white that it bleeds/runs/streaks ... NO, solais shingles have priced themselves out of any energy payback feasiblity and the cool varieties are close to doing the same but ... if desparately hot, these will help


5) lots of work but installing correctly reflective film barriers to the underside of rafters is remarkable in solving your heat problems ... too bad they didn't deck your roof with the OSB whose attic side already has this laminate on it

Answered 4 years ago by tgivaughn




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