March 27 2019 Thorwaldson is now offering the rain hat as a separate option for adding it to all other models of rafter mounted fans to enable them to be used with no attics.
As an example, Airscape, Tamarack and VentCool have fans that come in 24 inch diameter shells. I have designed a rainhat to mount perfectly in place of the blade guard using the same mounting screws.
PERFORMANCE IS GREATER BECAUSE STATIC PRESSURE IS NEARLY ZERO
This Tornado rooftop has wide open spaces between thin vertical turbine blades. As a result tests show at least a 30% increase in air flow. So if you use a 24 inch fan that pulls 5,200 CFM in an attic, it will pull over 8000 CFM through your roof. That increase in CFM when priced at the going rate for the basic fan, is computed thus – Looking at the VentCool 4.9, its 5200 CFM at $1450 is 28 cents per CFM. Adding 2800 CFM is worth $780.00 Looking at the Airscape 5300 with 5350 CFM at $1999 (.37 per CFM) this rain hat is worth .37 x 2650 added CFM or $990.00
The result of this is the price is set at a compromise, $800.00