Uncontrolled vs. Mechanical ventilation

HRV Ventilator from LennoxUncontrolled ventilation through air leakage (air infiltration) is a common cause of higher energy bills. And also a cause of moisture, pollutants and health hazards.

Uncontrolled ventilation through air leakage

Air infiltration - through gaps and openings in the attic, walls and floors, or around windows and doors - is the main source of fresh air in many homes, in cold climates, in wood-frame homes. Air is brought into them (and drawn from them) through gaps and openings, due to the wind and differences between indoor and outdoor temperatures.

But that’s a poor way of ventilating a home. Air leakage tends to provide too much air during windy weather, and too little during mild conditions.

And as long as it involves crawl spaces and openings and gaps in the attic and wall cavities, it will be a source of dust, pollutants, moisture, radon, that is, of unhealthy indoor air.

Uncontrolled ventilation costs

Air leakage ia a cause of over-ventilation during harsh weather conditions and under-ventilation in mild weather, and is also responsible for heat and air conditioning loss.

Besides, uncontrolled ventilation is also a cause of moisture damage, mold, mildew and unhealthy air.

And that's where mechanical ventilation systems enter. They replace uncontrolled home ventilation, and are a key part of airtight homes, in many climates.Benefits of mechanical ventilation systems in cold climates
Mechanical ventilation systems are a key part of modern energy-efficient homes, in many climates. They prevent drafts and the growth of mold, mildew, pollutants or odors, and provide more comfort and protect the building structures from moisture damage. And they are key for a good indoor air quality.

Spot Exhaust ventilation systems

Mechanical ventilation systems can be of various types.

Most homes have now spot exhaust ventilation systems in their bathrooms and kitchens. Bath FanEvery kitchen and bathroom should have exhaust fans.

See: Bathroom and Kitchen Exhaust Fans

Whole House Ventilation Systems

But there are more sophisticated systems with a wider scope, especially whole-house systems providing both stale air exhausting and fresh air supplying: the HRV and ERV systems.

Exhaust vs. Supply Ventilation Systems

Balanced Ventilation Systems

The passive stack natural ventilation option

Buildings with ducted HRV and ERV systems, do not require passive air inlets for fresh air (or to exhaust stale air).

Inlet and outlet vents only make sense in mild climates, or during the seasons when temperatures are very favorable.

Or in some tropical climates, in natural ventilation cooling strategies.

Exhaust-only ventilation systems working in conjunction with passive inlet vents, may not work aas well as expected: there are reports stating that the vents may not work properly, that is, a part of them may not move significant amounts of fresh air… or may exhaust indoor air instead of supplying outdoor fresh air.

Ventilation in super-Insulated Passive Solar Houses

Passive houses - super-insulated buildings, designed according to the German PassivHaus concept - require a sophisticated and comprehensive mechanical ventilation system (HRV and ERV). That’s part of their standards. See, for technical details: BTec-Rosehhein

See, for more information on the Passive House concept: Passive House Is a Type of Low-Energy Homes.

See also: Should you Have a Mechanical Ventilation System?


five Non-ducted mechanical ventilation systems

There is now non-ducted, wall-mounted mechanical ventilation systems, based on small fan systems with a ceramic core.

That's the case of the German Lunos E2 systems, which are able to alternate between exhaust and supply modes, and to recover heat from the exhaust air stream (acting like HRV systems).





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