Getting all sweaty is a good thing… if you’re human. It usually means we’re expending energy and our body is doing a good job of regulating our temperature. But if our home is sweating, it might not be a good thing. Sweating, or condensation happens when building elements drop below the dewpoint (the point at which the air is saturated with water, the higher the temperature, the more water air can hold, if the temperature drops suddenly the water comes out of the air). Metal elements usually sweat first. This is primarily due to metals thermal conductivity (it’s ability to transfer heat). Because it can transfer heat quickly, it can drop below the dewpoint faster than other materials.
Any material that sweats can be bad. Obvious concerns would be with moisture problems and mold. Condensation can pool. This can result in hazards such as electrical shock.
Reducing humidity limits the probability of sweating (the air has to be much colder to force the water out). Insulating cold surfaces prevents the cold surface from coming in contact with the humid air. Foam wrap is usually best as fiberglass insulation does work when wet and will promote mold growth.