Frequently Asked Questions

Exhaust ventilation removes stale air directly from the source area (such as a shower) and draws fresh, dry air into the home, usually through leaks around windows and doors, or through dedicated air inlets (Airlets) in the wall or windows. Check out our application guide, One Size Does Not Fit All which explains the difference between exhaust, supply, and balanced ventilation.

Supply ventilation delivers air directly into the home, either through dedicated ducts and/or forced air systems. Homes with supply ventilation systems still need exhaust fans in bathrooms and other high humidity or high contaminant areas, however, a supply ventilation system still supplies fresh air whether or not the exhaust fans are operating.

Balanced ventilation uses two fans; one to exhaust stale air and one to deliver fresh air to the home. Heat recovery ventilators and energy recovery ventilators are both examples of balanced ventilation.

Intermittent exhaust means that the fan only operates when it is turned on. This is sometimes also called on-demand or spot exhaust. In order to be effective, the location and size of the fan is critical.

Continuous exhaust means that there is always a low rate of airflow, as opposed to on-demand/spot/intermittent exhaust in which the fan exhausts air at a high rate for a short period of time.

A traditional central ventilation system has one powerful fan that treats all rooms the same, if the fan is on, it ventilates all rooms at once. A zoned system usually has one centrally located fan, but it allows the homeowner to exhaust only the room(s) in use, such as one bathroom, at a time, so the load placed on the heating and cooling system is significantly less. Aldes’ patented Zone Register Terminals make these zoned central systems possible and simple to install. See a demonstration video to get an idea of how these systems function.

Distributing supply ventilation delivers fresh air into the home through a wall hood and passes it through a filter before distributing it into the home. It is for use in homes that do not have a central heating or cooling system. Homes with supply ventilation systems still need exhaust fans in bathrooms and other high humidity or high contaminant areas, however, a supply ventilation system still supplies fresh air whether or not the exhaust fans are operating.

Filtering supply ventilation supplies a home with a constant flow of low volume fresh, filtered air. These systems are for use in homes with central heating or cooling systems, however the ventilation system will run regardless of whether the heating or cooling system is turned on. Homes with supply ventilation systems still need exhaust fans in bathrooms and other high humidity or high contaminant areas, however, a supply ventilation system still supplies fresh air whether or not the exhaust fans are operating.

Heat recovery ventilators pull fresh air into a home while simultaneously exhausting stale are from the home. Ideally, the fresh air is delivered to the living room and bedrooms, while stale air is removed from the bathrooms, laundry rooms, and sometimes the kitchen. Both the fresh air stream from outside and the stale air stream from inside the home flow through the HRV. The HRV allows some of the heat from the warmer air stream to be transferred to the cooler air stream. In winter, it recovers some of the heat that would have otherwise been exhausted. This heat transfer occurs without any mixing of the two air streams, reducing the cost of heating.

An energy recovery ventilator pulls fresh air into a home while at the same time exhausting stale air from the home. Ideally, the fresh air is supplied to the living room while stale air is exhausted from the bathrooms, laundry room, and sometimes the kitchen. Both streams of air (from inside the home and outside the home) flow through the ERV. The ERV tempers the air coming into the home and allows some of the moisture in the more humid air stream (usually the stale air in winter and the fresh air in summer) to be transferred to the air stream which is dryer. This is done without mixing the two air streams. This makes dry homes more comfortable in the winter, and saves money on air conditioning in the summer.

The unit should be relatively close to an exterior wall to minimize the length of the insulated duct to the exterior vent hoods. The outdoor duct connections must be insulated with a complete exterior vapor jacket to prevent indoor moisture from condensing on the inner duct, which would water-log the insulation layer. The duct connections to the heat exchanger and the exterior vent hoods must be designed to maintain the vapor jacket over the insulation. The fresh air intake must be located approximately six feet or more from any exhaust device, including discharge from the HRV/ERV, and it should not be installed where noxious gasses from outdoor sources are likely to be present, such as the exhaust of an automobile in a driveway. See our document, Considerations for Locating, Installing, and Ducting Heat & Energy Recovery Ventilators.

A continuously operating whole-house mechanical ventilation system is the best method to ensure a proper amount of ventilation. American Aldes offers a full range of continuously operating whole-house ventilation products. See our document, Introduction to Indoor Air Quality to see illustrations of 6 different configurations, including 1. Continuously operating exhaust systems 2. Continuously operating exhaust systems with on-demand boost 3. Continuously operating HRV/ERV or fans with or without boost 4. Continuously operating HRV/ERV for fans plus on-demand rangehood 5. Continuous operating exhaust plus on demand bath fans and rangehood 6. Continuous operating supply plus on demand bath fans and rangehood.

ASHRAE has identified several different climatic zones in the United States. See our document, Residential Applications by Climatic Zone. for guidance, or contact an Aldes expert for assistance at 800-255-7749.