My hip roof attic is kind of complex (attached car port); but basically it is 1200 sq feet, with about 20 feet of ridge; on which I have 15 feet of Shingle Vent II. That's not enough -- the attic hits 135 on sunny days in June (Maryland). And my ductwork is in the attic.
So I am thinking of installing Hip Ridge Vent (say, 8 feet down each of the four 25 feet long hip ridges).
The question is whether this would help. There seems to be disagreement about the effectiveness of hip vent (eg; does it short cut the soffit to ridge stack effect)?
Any experience or advice?
BTW: I have about 110 sq feet of slotted soffit, which should get me close to the 1200/300=4 sq ft of recommended soffet vent (assuing about 5 NFVA/lineal foot.
BTW2: I asked same question in an HVAC forum, and got mixed responses. Some thought hip ridge vent would help, others not. Static vents seem to be preferred, but not universally. And my local roofing company recommended a 2000 CFM power Lomanco.
On a hip roof such as that I would recommend the power vent. Wouldn't necessarily have to be the electric one. You could also use solar vents to avoid having to wire them if the access is limited.
I have seen the hip vents but have no experience using them.
Would recommend getting a power vent as dstew66 said, but have a humidistat on it as well for the winter. This will exhaust the warm/moist air in the attic to reduce condensation and/or frost on the underside of the sheathing.
Interesting -- "install power vent" being the unaninmous opinion (ignoring small sample size issues). In comparision, the hvac people, who were pretty much against any kind of power venting!
Would you cover up the existing ridge vent, or leave it be?
Yes, get rid of the ridge vent. You want the fresh air drawn in at the eaves, not the ridge. Air Vent has an excellent resource you can download that explains the Principles of Attic Ventilation (PAV course). You can access the pdf download here.
Thanks, I am aware of these principles (though taking a bit of time on that course might be interesting). So I admit that was something of a stupid question.
It still is interesting that the "PAV is the way to go" is a dominant opinion here, but not on the hvac-talk site. I would like to hear a few more informed opinions before I go to the trouble (and expense) of covering up that nice ridge vent and installing a PAV.
Check the width of your existing ridge vent opening to accurately calculate your exhaust. If you have 3" (normally the max 1.5" each side of the peak) you have more exhaust than your intake calc at 5sf). DO NOT mix exhaust systems. If you install a vent lower than the existing exhaust (IE hips), the new opening will turn into an intake and make your soffit intake obsolete.
If your calc of existing exhaust falls short you can consider 4' or 8' off-ridge vents (but you need to omit your ridge vent if so). You want intake at the lowest part and exhaust at the highest to fully recycle the attic air.
If you install a solar/power vent and keep your ridge vent, you will have wasted money. When the fan turn on its going to pull fresh air from path of least resistance... IE: ridge vent.
Do not mix exhaust, do not mix "height" levels of exhaust and do not spend money on electric to vent your attic.
Here is some good reading:http://imageserver.webpropartners.com/usermedia/me06747//VentilationSpecifications.pdf
hip vent will only work if the house was framed to have hip vent ,It has to have a double ridge board on the hip to install the hip vent properly .You can't have a power vent and ridge vent its either one or the other ,because the power vent will pull air from the soffit and the ridge vent area, lose the ridge vent and install a power vent................
Solar powered ventilators are catching on in the Miami roofing market. Pretty hot here... Get rid of the rest.
** roofer mike**