It's. slowly melting as the temperatures will be freezing for the next week.

Newer gas boilers have a digital readout on it, and also only heat the water as much as they need given outside temperature and the difference between the room temp and desired setting (so it's never going to send say 210 degree water to the radiators).

So I have tried to read up on laws in the Seattle, WA area and it seems that I am allowed to have a central heating system and just put in the lease that the temperature can't be set to lower than 68 degrees.

Let e P you a few and you can take their temperatures.

I certainly don't want to be paying those holding costs.I guess the exit strategy of selling the property is only as good as the temperature of the market.A friend of mine just sold his grandparents house in the same town.

You'll need to turn your HVAC system off, so hope it is moderate temperatures.

Installing multi-zones on a furnace so each apartment can control their own temperature can be challenging and more expensive than with a boiler and hot water.  

Last month, or before the temperature dropped below freezing?

There are charts online that show what are acceptable humidity levels in relation to outside temperatures. 

I have been involved in various areas of construction for over 20 years, with the last 5 being primarily spent as a project manager in the temperature control (HVAC) industry.