There are a number of mitigating technologies which can be used to maintain quality indoor air. Our home has a heat exchanger to bring in air from the outside

There are a number of mitigating technologies which can be used to maintain quality indoor air. Our home has a heat exchanger to bring in air from the outside & venting in the mechanical room which is on a timer to exhaust any buildup of products of combustion from the gas furnace and water heater. The crawl space is also vented to avoid a build-up of radon gas. Interestingly, the homes used as an example in the article are getting mini-splits which don't have venting capabilities. They are awesome and I love the one we have in our home theater, but am afraid that when they are the only solution used for heating and cooling in a well sealed home the important issue of venting the home properly and in an energy efficient manner may not be addressed. With a central air system it's relatively easy and cheap to do an external heat exchanger. With a mini-split solution, a dedicated heat exchanger system would need to be installed separately from the main source of heating and cooling.