(Climate zone 4A – Charleston, WV) I built a small (12′ x 24′ main level w/ loft) guesthouse in my back yard. I am fairly new to building and decided to experiment with building it as tight as possible. I caulked all the stud bays, foamed around all window and door opening, etc. I don’t have specific numbers but with all the windows closed there is a definite suction when the door is opened or closed. (Please excuse my vagueness, I have not done a blower door test). For simplicities sake I had planned on doing an exhaust-only ventilation system based around the bathroom exhaust fan. There will also be a dryer in the bathroom exhausting to the outdoors.

My question is –
a) if I do an exhaust only system what CFM should use for the bathroom exhaust fan?
b) should I consider a different approach such as a HRV for a house this small? If so, can you direct me to a HRV appropriate for this size dwelling?
c) any other advice, ideas, or concerns that I may not have thought of?

This is primarily a concern for the winter months only as we don’t use air conditioning and keep the windows open throughout the warmer months.

Thanks!