Jeff Donnell
If you think you can or think you can't...your right
6/3/2011
Hello, Am building new house with cold-formed framing. Roof installed with 16" 26 ga. standing seam. Am about to install the vented soffitt (vinyl). I don't have any ridge vents (4/12 pitch) and was considering using a 120 vac powered roof ventilator or an powered end wall ventilator. I your opinion, which would be more beneficial. Will the heat veted from the roof cause discoloration of the steel? Being I used 16" SS, can a powered roof vent even be used? Thank you in advance for any suggestions. Respectfully, DJ
Todd Miller
Isaiah Industries, Inc.
6/4/2011
Thanks so much. Generally I would not expect any discoloration unless the vent discharges a lot of moisture which causes consistent heavy dew on the surrounding roof which could support biological growth. As far as what type of vent, you want to as best you can pull air which continually "bathes" the underside of the roof deck with fresh air. Think about your airflow patters from instake to exhaust which might best create that sort of good air flow.
Eric Novotny
An informed customer is the Best Customer!
6/4/2011
The heat should not create any issues. If you are allocating for soffit venting, I would prefer to see a passive ventilation exhaust (i.e. ridge vent) instead of a powered attic fan. Safer, non energy consumer, doesn't depressurize the attic.
Jeff Donnell
If you think you can or think you can't...your right
6/6/2011
Hello, Thank you for your responses. Yes, the soffit will be vented every 4th panel and I will install baffles between each truss so the insulation won't impede airflow. I would like to have a passive system but hate to cut into the roof to install the vents needed. Are there any secrets to installing a vent into standing seam? Trussees are 24" OC. I undestand a passive system is best but why would a negative pressure in the attic be bad? Chance of pulling are from inside the house? Just curious. Trying to learn as much as I can. Thank you, DJ
Todd Miller
Isaiah Industries, Inc.
6/7/2011
Great. It sound slike you have a good plan as far as intake. Yes, the risk of exhaust being greater than intake is sucking air up out of the house. You will find that different manufacturers have different ridge vent recommendations for standing seam. My suggestion is to make sure that you work with the manufacturer of the standing seam to ensure you're using a system of which they approve. Here's a great source of info on ventilation: http://www.airvent.com/pdf/literature/PAVbooklet.pdf
Eric Novotny
An informed customer is the Best Customer!
6/7/2011
+1 Seems well thought out. Powered ventilation inevitably sucks conditioned air from the living space below and is a bad thing. Too much air movement over the insulation (if fiberglass) decreases its effective R-Value as well. Passive is probably just fine for your application.

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