mechanical home ventilation

Mechanical ventilation can be as simple as a set of two exhaust fans: a kitchen exhaust fan and a bathroom exhaust fan. But it can also be a much more complicate system. And modern homes, with good insulation levels, demand those more complicate systems, that is, mechanical HRV and ERV ventilation systems.

Indispensable

In tightly air sealed buildings, mechanical ventilation is indispensable. These buildings can no more rely on air leakage to supply their fresh air needs, and natural ventilation can't simply supply enough and constant fresh air. Mechanical ventilation is the only alternative.

The simpler systems: exhaust ventilation systems

Kitchen and bathroom exhaust fans are a typical exhaust ventilation system. They are common, and can be more sophisticated, but their essence is that of kitchen and bathroom exhaust fans.

Supply ventilation

Supply ventilation systems provide fresh-air distribution, instead of exhausting stale air, like exhaust ventilation systems.

HRV and ERV systems

HRV and ERV systems allow to exhaust stale air from homes and also to bring fresh air into them. They combine this two features. Often, they involve a duct system (see diagram below for a HRV system. Source: Energy Star).

HTV Mechanical Ventilation

HRV systems

Heat Recovery Ventilators (HRV) are the most common solution in colder climates. As stale (and warm) air is expelled by the system, the heat recovery core warms the incoming fresh (and colder) air, recovering that heat.

ERV Systems

Energy Recovery Ventilators (ERV) are a refinement of HRV systems, and are a more common solution in warmer climates and in high-humidity environments.

While HRV systems transfer heat between the airstreams, ERV systems also transfer moisture, which means lower air conditioning costs in hot and humid climates.

HRV/ERV installing

HRV and ERV models are sold and installed by heating, ventilation and air conditioning (HVAC) contractors. They can be good advisors in the buying process.

Costs

Costs vary with the model. There are models with and without moisture transfer, defrost control, pre-heater system to prevent ice buildup (a must needed feature in cold climates); there are single speed models and multiple speed models, models with pollutant sensor controls, with high efficiency air filter, etc.

Costs depend also on the size of the system (often based on a total ventilation capacity equal to 0.05 CFM/square foot). Costs around $1,000 to $2,500 are very common… in new constructions.

Energy Operating costs

HRV/ERV operational costs are very low: below $1.00 per day even for more complex and continuously working systems.

Comparing the performance of HRV/ERV models

Prefer Energy Star and other officially rated systems. To compare performances, take into account the model's Recovery Efficiency (Sones) and the CFM (Cubic Feet per Minute). Models with higher Sones and higher CFM are the best options.