Solar fans have simplified attic ventilation. Having been in the business of ventilating attics for almost thirty years, one of the most difficult (and, in fact, impossible) situations to deal with in completed construction is heat buildup in completed rooms or finished attics with "up to the peak" cathedral ceilings. If you're an architect, builder or homeown considering cathedral ceilings, I have recommendations you might consider. The present theory, as reflected in most building codes, is that hot air will travel by convection from the soffit vents, through the styrofoam spacers and exit through the ridge vent.
Our experience has been that this theory does not work very well. In fact, the air below the roof can reach temperatures in excess of 150 DegF. That hot air is rapidly expanding. Unable to escape through the ridge and soffit vents quickly enough, it pushes through the porous insulation, heating up the ceiling and creating a tremendous heat gain to the living area. Very often, even a well-designed A / C system can not keep up.
SUGGESTION: Design a small attic over the cathedral ceiling. A solar-powered roof fan will exhaust heat from the "attic", creating a vacuum, thereby pulling in cool air from the soffits through the spacers. This creates an envelope of cool air around the living space, (If you already have some flat ceiling, just add a solar fan). .
These heat gain forces are the same in a regular stand-up attic. The solution is the same.
The living area with cathedral ceiling will be AT LEAST 10 DegF cooler with proper insulation, soffit vents and a solar roof fan, without the A / C turned on.
Please note: insulation contractors should ensure unobstructed airflow from soffit vents to attic.
Solar powered attic ventilation is one of the most cost-effective ways to improve energy efficiency for air conditioning and to improve LEED score. Typical installed cost is about $ 550 after tax credits are applied. Federal Energy Tax Form 5695. Energy saving and carbon footprint for cooling can be reduced by 10% to 30%. Payback time is less than 5 years. Every succeeding year is money in the bank!
Architects would be well advised to include and specify quality solar fans during the design phase of a project. We have many request from townhouse style condo owners because the upper floors of the unit are warm, even with the A / C turned on. They are invented from taking remedial action because they can not get permission from the Condo Association Committee.
A minimum 10% reduction in energy usage (and proportional reduction in carbon footprint) for cooling is a huge number. Moreover, it's most effective at the exact time when the stress on the "grid" is the greatest, during hot weather. Cost saving to the utility company by not having to upgrade their infrastructure because of reduced peak demand is substantive.