Guest guest Posted October 8, 2010 Report Share Posted October 8, 2010 Sue, I have tested many ridge vents. In reality, most ridge vents are useless because they are blocked with mesh (to prevent wind/rain entry). The entire concept is faulty for winter ventilation. The theory of roof ventilation is based on convection: warm air rising and cooler air sinking. In the winter, there is not enough of a temperature difference between the inside of the attic and the exterior air (maybe a few degrees) to cause significant convection. So air flow is determined by wind pressure differences. In the summer, there may be over 40 degree difference between outdoor air and attic air, so convection will function. But I agree with Barb. If you have not had any problems, keep the ventilation the same. BTW, in more than 60% of the re-roofing jobs I have looked at in New England, the roofers never even cut a hole before installing the ridge vent!( Easy money from suckers.) May May Indoor Air Investigations LLC Tyngsborough, MA www.mayindoorair.com 978-649-1055 > > POSTED BY: \ " SSR3351@...\ " SSR3351@... > SSR3351 > > Thu Oct 7, 2010 9:13 am (PDT) > > Thank you for your reply. The roofer told us just that. The shingles > > couldn't be guaranteed without the ridge vent. Out home is very well > built (in > 1968) without any problems. One large vent high on one side the other > two are > on opposite sides of the roof. They are square like boxes that are > air > vents. I just don't want to mess with the house as it is since we > have no > problems. The attic gets hot during the summer but what attic > doesn't. I just > don't believe that a ridge vent is going to make that much > difference & > don't want to change the construction of the home. > Barb, are you the one that was unhappy that you had the ridge vent > installed. I recall someone had problems afterwards but can't > remember who it was. > Thanks again! Sue >>>>> > It used to be the case that it was 'code' to vent roof, but that is > new > construction I believe. The only thing other than that was that > shingle > manufacturers say they won't warrant their shingles if you attic > isn't vented. > However my attic was not vented and was built in the 1930's and no > mold up > there. They get on these issues that really don't apply to older > homes. New > homes are built differently. Anyway, new code for new homes allow for > > unvented attic if you use foam, but then again, I don't think > 'building codes' > apply to just reshingling your roof. If you attic is hotter, they > feel their > shingle may get hot and dry out faster. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 8, 2010 Report Share Posted October 8, 2010 Hi Jeff I agree that many ridge vents are installed incorrecly, with some not being cut and when cut not cut wide enough in accordance with manufacturer's specs. Also, most attic ventilation is not designed properly. In mixed climates, proper roof top and soffit ventilation is essential to prevent ice damming will occur in the winter months. If installed correcly, we do not find that ridge vents are useless in the winter in the midwest. There is still heat diffusion from the living space, and it must have somewhere to go. The insulation and craft paper vapor barriers do retard vapor and heat diffusion, but there is still vapor and heat diffusion at other areas, such as whole house fans, recessed lights, wire and pipe penetrations, top of stud plates, etc. Ridge vents should be baffled to deflect wind at the exit. In MI, we have had success with Shingle Vent II ridge vent in combination with soffit vents designed to achieve 1 sq. ft of free vent space per 150 sq. ft of attic floor space, with 50% of ventilation at the ridge and 25%at each soffit. To make the soffit-ridge connection effective, recessed lights, wire penetrations, and other pathways to the attic must also be properly insulated. This can best be achieved with two-part closed cell foam. Sottit vents are kept open with baffles that completely span the truss spaces. WEe also install a template styrofoam block at the tops of the exterior walls. The Shingle Vent II has a baffle that deflects the wind from the exit, maintaining a low pressure zone so that the high pressure air in the attic will exit. There are are probably other roof top vents that can achieve the same effect if properly installed. This is the one that has resulted in the best results for our clients. Without proper ventilation that includes ridge or roof top and soffit vents, ice damming will occur in the winter months. What do you recommend for roof top ventilation. Connie Morbach, M.S., CHMM, CIE Sanit-Air, Inc. sanit-air.wordpress.com > > Sue, > > I have tested many ridge vents. In reality, most ridge vents are > useless because they are blocked with mesh (to prevent wind/rain entry). > > The entire concept is faulty for winter ventilation. The theory of > roof ventilation is based on convection: warm air rising and cooler > air sinking. In the winter, there is not enough of a temperature > difference between the inside of the attic and the exterior air (maybe > a few degrees) to cause significant convection. So air flow is > determined by wind pressure differences. > > In the summer, there may be over 40 degree difference between outdoor > air and attic air, so convection will function. > > But I agree with Barb. If you have not had any problems, keep the > ventilation the same. > > BTW, in more than 60% of the re-roofing jobs I have looked at in New > England, the roofers never even cut a hole before installing the ridge > vent!( Easy money from suckers.) > > May > May Indoor Air Investigations LLC > Tyngsborough, MA > www.mayindoorair.com > 978-649-1055 > > > > > POSTED BY: \ " SSR3351@...\ " SSR3351@... > > SSR3351 > > > > Thu Oct 7, 2010 9:13 am (PDT) > > > > Thank you for your reply. The roofer told us just that. The shingles > > > > couldn't be guaranteed without the ridge vent. Out home is very well > > built (in > > 1968) without any problems. One large vent high on one side the other > > two are > > on opposite sides of the roof. They are square like boxes that are > > air > > vents. I just don't want to mess with the house as it is since we > > have no > > problems. The attic gets hot during the summer but what attic > > doesn't. I just > > don't believe that a ridge vent is going to make that much > > difference & > > don't want to change the construction of the home. > > Barb, are you the one that was unhappy that you had the ridge vent > > installed. I recall someone had problems afterwards but can't > > remember who it was. > > Thanks again! Sue > >>>>> > > It used to be the case that it was 'code' to vent roof, but that is > > new > > construction I believe. The only thing other than that was that > > shingle > > manufacturers say they won't warrant their shingles if you attic > > isn't vented. > > However my attic was not vented and was built in the 1930's and no > > mold up > > there. They get on these issues that really don't apply to older > > homes. New > > homes are built differently. Anyway, new code for new homes allow for > > > > unvented attic if you use foam, but then again, I don't think > > 'building codes' > > apply to just reshingling your roof. If you attic is hotter, they > > feel their > > shingle may get hot and dry out faster. > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted October 8, 2010 Report Share Posted October 8, 2010 Jeff, thank you SO much for the explanation of attic air circulation!! I truly appreciate your input and expertise! My husband and I have talked about the ridge vents and have decided that we are not going to have the any roofer add one to a house that has not had any problems in 42 yrs. My house is the only place I am safe and I certainly don't want to create a problem! Again, many thanks! Sue R. Quote Link to comment Share on other sites More sharing options...
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