Tom:

I spelled the name of the heat exchanger wrong. See,

http://www.mitsubishi-aircon.co.uk/lossnay/

The ducted commercial model would require heavy insulation on the ducts
heading to the outside. I don't have the USA reseller URL.

If room a de-humidifier is not used there would be a considerable amount
of water condensation in the heat exchange element, and drains should be
provided. Every so often all the water that you see on the floor and
walls would be ducted to the outside through the heat exchanger. The
vendor should be asked for information regarding the condensation drain
function of the unit. It changes out the air and saves the heat or cool.

The unit is only an exhaust fan with a fresh air supply and core, and it
is not a heating or air cooling device.

The fresh dry air is a remedy. The hydrostatic pressure at the wall
exterior is the problem.

Ralph Hertle