HRVs/ERVs are typically sized to ventilate the whole house at a minimum of .35 air changes per hour. To calculate, simply take the square footage of the house (including basement) and multiply by the height of the ceiling to get cubic volume. Then, divide by 60 and multiply by .35. Fantech Heat Recovery and Energy Recovery Units have been designed with new "high tech" electronic control boards. Features include: Accessory control contact allows the ventilator to connect to other equipment such as an existing forced air system to trigger the furnace blower motor to turn on and off on demand. A diagnostic LED Allows units to be easily operated from a remote Intellitek Multi-Function Wall Control. (Requires PDF reader) (Requires PDF reader) (Requires PDF reader)