If your home has a furnace installed in the garage, it most likely is. At one of our construction 101 classes at our Volare Town Home community in Happy Valley, this came up. We have been installing our entire HVAC systems inside the conditioned space of our homes (meaning the interior living area of the home). We realized the obvious benefits of: improved performance by reducing the length of duct work for the air to travel, by not installing ducting in the attic or crawlspace spaces as they are much hotter or colder than the air we are providing to the rooms that need it. Another benefit is, if the duct system leaks air it is only leaking into your home not the outdoors. However, it never occurred to us the air quality benefit of a furnace in the home versus the garage.
The furnace unit that is installed inside the conditioned space is a "Sealed unit" this means that the cabinet of the furnace is entirely sealed up. Unlike, most furnace units that are installed in a garage. Most people can recall being near a furnace in a garage when it started up and seeing the flame burning through the venting of the front of the furnace cabinet. What probably didn't come to mind was that when the fan motor started up it was pulling air from within the garage. This could be including the exhaust from the car, gas fumes from the gas can, bag of yard fertilizer, etc. Anything off gassing in your garage could have its fumes spread throughout your home.
The great benefit of a Marnella Homes system being entirely with the home is that it is only pulling fresh air from the exterior of the home with the assistance of the HRV (Heat Recovery Ventilator). The HRV periodically exchanges stale interior air with fresh outside air. This provides interior air quality that is superior to any traditionally installed HVAC system. This should be especially important to anyone with children that have asthma or any other respiratory health issues.
So, should you be stuck with a traditionally installed system in your home, consider this when you are letting your car warm up in the morning and you might want to find a better place to store the gas can, fertilizer bag or anything that you smell when in the garage. However, if you are looking at buying a new home, you owe it to you and your family's health to consider how your next HVAC system is installed.