Thanks. The smartvents would be near to the edge of the roof under shingles, not in the soffit. So, would snow be a possible problem in this instance?

I'm not a fan of smart vents for attic ventilation in cold climate zones like upstate NY. The vents can be blocked by ice dams. I'd stick with the well-proven soffit and ridge vents.

My suggestion is to install a ridge vent and a smart vent. I had the smart vent installed in my roof last year. I have soffit vents but the are mostly blocked by batt insulation. The air flow is now much better. It is a good product if it is installed properly. I wish I has know about it when I replaced the roof the first time.

I am not sure if the gable vents need to be closed. It would seem more ventilation would be better. Charles Ross thinks they will cause air flow interference. I am skeptical, but it could be true in some situations.

@mike_home,

Bill Rose at the University of Illinois at Urbana-Champaign has done considerable research on attic ventilation. His finding is that gable end vents interfere with natural convective air flow in attics. I'd recommend avoiding them, We don't use them in homes we design and build.

Smart vents are subject to blockage by ice dams and snow in cold climates while soffits vents are not. The need to ensure soffit vents are not blocked by insulation does not make them a less appropriate choice. Maintaining a path for ventilation air is easily done by installing polystyrene vent baffles. Our code compliance inspectors look for them when they inspect insulation.

I will defer to science on the usage of gable end vents and ridge vents. In general I don't think gable vents work well for ventilation with wind generated air flow. I would think a power gable vent is required to vent the air adequately.

My house has a hip roof so the smart vent is installed on all four sides. It is highly unlikely there will be ice blockage everywhere. Even if there would it last a day or two in my climate. The insulation was installed long before builders were installing vent baffles. I agree that is the correct way to do it with an adequate number of soffits. That was the other problem, not only were they blocked there were few of them. The soffits were covered with vinyl years ago with grilles for air flow. I remotely monitor the temperature and humidity in the attic. I can now feel the air flow when I stand in the attic.

I've had two houses that , for separate reasons, couldn't have soffit vents. Both had ice dams and icicles. Through careful air sealing of the second floor ceiling and adding insulation, all ice problems disappeared.

Air sealing and extra insulation are a great way to eliminate ice dams. Air sealing also makes attic venting much more fault tolerant because the amount of moisture which migrates into the attic is greatly reduced.

In cold climates like upstate NY, proper attic venting is most critical in the winter. Any type of vent with the potential to be blocked (e.g., snow or ice) elevates the risk of condensation or even ice in the attic.

Thanks Charles Ross. unfortunately we are unable to install soffit vents due the the way the 100 year old house was built. it seems that smartvents installed about 2.5 ft from the roof edge are our best option along with adding the ridge vent and sealing the gable vent. Or we could seal and spray ffoam the attic but i fear that would be too costly.

Converting your attic to a conditioned attic is a pretty serious investment. I did that in my previous home because my 2nd floor air handler and duct work were in the attic and I really needed some additional conditioned storage as well. If you don't need it for conditioned storage, I think you'll be well served to improve the air sealing and insulation of your existing, vented attic as Seabornman did.

If you have an historic home, shingle vents may not fit well (IMO a last resort). There are fascia vents, or a continuous linear soffit vent that can still happen with some flush fascias or if not, if you are willing to redo the fascia. There are also various versions of eyebrow vents.

Typically, when gable vents are used (besides being the only available version in the old days) it is because there is not a good solution otherwise. They do actually perform, and if you have never experienced problems in your attic it may be fine to continue with them as is.