The second cause is high indoor humidity, thats why if you have a whole house humidifier the recommended humidity setting is lower the lower your expected outdoor air temperature is, to prevent condensation.

They have multiple basketball/volleyball courts, weight room, training facilities, indoor half football field and a sprint track.I like that but want to add a climbing wall, football fields, baseball/softball fields, studios for exercise classes, dojo's, track and field areas, outdoor running/walking track, biking track, health food store, therapists, etc.My thoughts are for me to build, manage, and market the facilities.

For indoor runs PEX hands down.

I would keep it indoors or at least in a safe area while not in use.

The town of Watertown (a close-in suburb of Boston) is in lockdown, all residents asked to stay indoors, all public transportation shut down by the governor.

Jesse Holmes - Did you see the pic of Brandon Turner and I skydiving indoors (see below).

We actually wrote into our agreement "pets are not allowed to eliminate indoors"...

Despite these efforts, experts worry that transmission of the virus is still likely to increase during the winter months, as more people spend time indoors, colleges across the country send students home, and families gather for the Thanksgiving and December holidays.

There used to be a big indoor mall out there when I was a kid. 

We want to put in hot tubs, create an outdoor space and perhaps swap the in-door whirlpool tubs into washer/dryers (although not entirely sure).