You probably know that the V in HVAC stands for ventilation. But how many times have you thought about the ventilation system within your home?
For most of time, homes weren’t ventilated. Humans simply found a way to stay warm by bringing heat into the home, and had little thought process about what that heat did once inside.
There are several reasons ventilation is more important today than it was long ago. The biggest comes down to leakage; homes a few decades ago had leaks and cracks all over, giving ample room for fresh air to enter and exit. Also, building materials a century ago were mostly natural products that didn’t release volatile organic compounds (VOCs) into the air. Today VOCs such as formaldehyde, flame retardants, and other chemicals are prevalent in building materials, home furnishings, and other things.
Home ventilation comes in different forms.
No ventilation - This has been the most common form of ventilation over time. There is no mechanical system in place to bring fresh air in or release stale air out. In the past, insulation was non-existent and this strategy worked well in a leaky house. But the more airtight a home’s envelope has become, the more important ventilation has become.
Exhaust only ventilation - this is a common strategy in which small exhaust fans, usually in the bathroom and kitchen, operate either continuously or on demand to exhaust stale air and moisture to the outside. This strategy creates negative pressure in the house, which pulls fresh air through cracks or other air leaks, or through air inlets throughout the home. This is a simple and low cost method of ventilating a home, but it won’t avoid pulling in radon and other gasses we don’t want in our homes.
Supply only ventilation - a fan brings in fresh air and the stale air escapes through cracks and other leaks throughout the home. The air supply is often delivered to one location where it is sent through ducts and forced throughout the system for dispersal. Supply ventilation systems will pressurize a house, which can eliminate pulling other contaminants into the home, but may also allow moisture problems to occur.
Balanced ventilation - a balanced system provides separate fans that drive both inlet and exhaust air into the home. This allows you to control where fresh air come from, where it’s delivered to, and where it exhausts from your home.
Balanced ventilation with heat recovery - if separate fans introduce fresh air and exhaust indoor air, it makes sense to locate these fans together. If you include a heat exchanger, the outgoing house air will precondition the incoming outdoor air, which can help save energy needed to heat cold air. This air to air heat exchanger - a heat recovery ventilator or HRV is the way to go in colder climates. An energy recovery ventilator ERV is similar but transfers moisture as well as heat from one airstream to the other, which is beneficial in humid climates.
Do you know what you home currently uses to ventilate your living areas?