baffles in rafter bays dedicate pathways for cooler air to enter soffit ventilation areas. why builders mix ventilation strategies in attics, I'll never know or understand. there are three methods of venting attics, each are stand alone methods. not mix and match. gable end venting. soffit and ridge venting soffit and passive vents some areas are outlawing pav's, with good reason. Georgia is the latest to do so..see article below. as pav's pull hot air out of attic, they also pull cool air from duct leaks & from holes in floor of attic from conditioned space below. do they cool off the attic..you bet ya. by robbing conditioned air that you pay to cool. pav's..never a good idea for the person who lives in the house & pays the bills. undoubtably unvented attics benefit hurricane areas more thatn vented attics. putting insulation on the roofline puts ducts & equipment in semiconditioned space, and minimizes problems caused by holes in air barrier at attic floor. but for those who don't go that route, proper attic ventilation is important. just as important is sealing holes in attic floor. ICAT recessed cans, sealed supply boxes that penetrate attic floor, sealing oversized cuts at bath vent fans and so on. insulation doesn't work when air moves through it. creating an air tight barrier between attic and living space is crucial. Georgia Pulls the Attic-Ventilator Plug "The state residential code allows only solar-powered versions; plug-in powered attic ventilators will no longer be allowed Posted on Aug 31 2011 by Richard Defendorf Building science target. The money that would have been spent purchasing and installing one of these attic fans could pay for a more cost-effective upgrade, which would include more ceiling insulation and proper air sealing. Attic ventilator fans have taken a whupping in the court of building science, played starring roles on useless-products lists, and gotten roughed up in the comments sections of blogs. Now they�re gadget non grata in Georgia�s supplement to the 2009 International Energy Conservation Code. Actually, as energy consultant and Energy Vanguard blogger Allison Bailes points out, that particular part of Georgia's code supplement contains a loophole. In its list of mandatory "Systems" requirements, Georgia allows solar-powered attic ventilators, but attic ventilators designed to use grid power "shall not be connected to the electric grid." In other words, you can have one, as long as it's not plugged in. Dealing with the heat Despite the compromise, the rap on attic ventilators is now anchored in code. Promoters of these machines say the devices help cool attics by exhausting hot air to the outside. However, attic-fan critics say the fans often draw makeup air from a home's interior. During the summer, there's obviously a major energy penalty if your attic fan is pulling air-conditioned indoor air from the living space into the attic through leaks in the ceiling. Frequently cited research results from a study conducted in 1993 and one conducted by the Florida Solar Energy Center show that attic exhaust fans also can depressurize the living area to the extent they create potentially hazardous backdrafting conditions, particularly in homes with atmospherically vented gas appliances. Energy consultants like Bailes and building scientists from FSEC and the Building Science Corporation suggest that, for most homes, the most cost-effective and safe approach to address high heat in attics is to perform air-sealing work at the ceiling and to insulate deeply. " best of luck.

Sorry I didn't save the source, but when I was doing the roof on our hip I found an on-line formula that was very clear about how many square inches of unpowered vent would serve. I have only 14 feet of ridge, but used a vented shingle, plus I bought several good-sized "turtle" vents and kept the two little ones that the house originally had. I also went to some trouble to improve the soffit venting. I think it's paid off in the living quality of the house, and it should help ensure that the asphalt roof lies flat for a long time. (We bought pretty good architectural, long-warranty shingles, and figure there's no point in undermining their useful life span with poor installation. I told my wife it was my last roof, and I hope I'm right!) Good luck, M

ISTM that there are two issues at work here. The first is that you are smelling unburnt gas in the house. Someone needs to find out why. Is there a leaky connection leading up to the dryer or is there an internal failure that's allowing unburnt gas to escape? Or, maybe, there's an insignificant amount of gas released when the dryer heater lights off. I'd expect the utility tech to determine which, though I wouldn't expect him to be able to do much about an internal failure other than advise you to call an appliance repair service. Secondly, and the one the utility company keyed on, there's a maximum allowable back-pressure for exhaust from the dryer (.4" WC or more, depending on total duct length) in order to keep exhaust gasses from remaining in the house. I doubt the technician measured it, but rather made an assumption based on the apparent design.

Happy to help. I've had a bit of this work done myself, in two different houses. In one, I had a Fantech BFRK 100 installed. There was an existing bathroom exhaust fan that worked poorly but I didn't want to put in a new grill. With the BFRK, you take out the guts of the old fan, keep the housing in place, and then connect ducting that runs first to the Fantech unit located a few feet away up in the attic and then from it to the roof passthrough. I had that done by an HVAC contractor who was on site replacing HVAC equipment. I'm not sure they would have done the work otherwise, it was like a favor to me. The second one was the replacement of a 20 year old exhaust fan with light in a WC closet that was noisy and ineffective. I had that done by an electrician who also was doing other work. He needed to go into the attic to remove the old unit, connect the new one to the framing, put in a new duct and connect the power. It made a huge difference. That one also vents through a roof pass-through, important because we use it to vent the bathroom of moisture from showers and baths. Good luck and keep your BS detector handy. If other exhaust vents terminate in the attic, it's time to fix those too. Each duct run needs its own roof passthrough unless you're using a Y setup with one fan at the base of the Y for two locations. Be careful if so, those can be tricky if the duct runs from the rooms to the base of the Y aren't of equal length. As far as duct run distances go, the unit will specify the maximum distance. For my most recent job, the ceiling unit with light that was 110 CFM, I want to say the spec for the duct run was something like 60 feet. I wrestled with putting a wall vent on a gable end but decided to stick with the existing through-roof vent.