Ventilation Systems Introduction
Ventilation System Introduction
All residential mechanical ventilation systems share four common features: an exhaust fan (link to E-150) with duct to remove air, an air inlet system that brings in fresh air, a method to distribute fresh air to the living areas, and controls to set the ventilation rate. In addition, and to provide an effective air exchange, the system must run continuously. The biggest difference between these systems is the method of bringing in and distributing the fresh ventilation air.
System I
The heart of this system, as with all residential mechanical ventilation systems, could be a single quiet, bathroom exhaust fan or, ideally, a 2 speed multi-port ducted central system fan such as the Eneready E-150 (link E-150). This fan would run continuously at low speed, ideally ducted on the inlet side, and exhausting the stale air from the kitchen and, most importantly, each bathroom. With this simple system, the fresh replacement air is drawn directly into the residence via passive, through-wall inlets located in those rooms most in need of fresh air; there’s no supply air fan with this system and almost no supply air duct.
Multiple passive, high wall inlets provide both an intake path and fresh air distribution to the living area and each bedroom. This system is prescriptively included in the BCBC identified by TECA as Example 4. However in exchange for simplicity and lowest first cost, restrictions are placed on its application. The residence must be single level, occupy a small footprint, have a non-forced air heating system, have no chimney and be located where the January winter design temperature is warmer than -20°C. This system has been used in millions of dwelling units over the past 30 plus years in some of the European countries most advanced in the area of residential ventilation.
Aereco
This innovative system is a technological upgrade to passive inlet systems. It is designed to automatically reduce the base ventilation rate whenever possible in order to save energy that would otherwise be consumed in ventilation. Aereco’s smart exhaust grilles track the exhaust needs of the kitchen and the individual bathrooms by sensing the (relative) humidity of the respective room. They then raise or lower the exhaust rate as needed. For example the commonly used bathroom with drying towels will enjoy increased exhaust compared to the little used 2nd bathroom. The inlets are also smart and similarly respond to relative humidity and slowly open or close in response to the individual fresh air needs of the living area and/or the bedrooms. For example, at night a 2 person bedroom will automatically receive more fresh air than a single occupant bedroom which will receive more again than the unused living room. Aereco is an enhancement of System I, and therefore the same restrictions apply to its application.
System C
This system is also prescriptively referenced in the British Columbia Building Code (BCBC), identified by the Thermal Environmental Comfort Association (TECA) as Example 1. It is applicable to all forced air heated dwelling units without climatic limitation and commonly used due to its simplicity and comparatively low cost. Generally speaking, this type of system has been operating in natural gas forced air heated houses since the introduction of standard efficiency natural gas furnaces more than 60 years ago: house air was exhausted up the furnace ‘B’ vent with the furnace by-products. With the mandated heating appliance efficiency upgrades, a principle exhaust fan, or ideally a 2 speed multi-port ducted central system fan such as the Eneready E-150 (link E-150), is now required to provide the central exhaust that is no longer available via the ‘B’ vent. An Eneready Iris Damper (link to Iris, Flow Control) provides an excellent flow control device for control of the inlet air volume.
Central Recirculating Ventilator
The Central Recirculating Ventilator (CRV) system is applicable to those non-forced air heated dwelling units without limit to square footage, number of levels or climate restrictions. The CRV fan (an Eneready E-150 works well for this application) draws in fresh air, mixes with house air to temper it, and delivers this mix to bedrooms. While needing a companion fan (or 2nd E-150) to provide the principle exhaust function, this system is relatively low cost and straightforward to install.