you can simply file a complaint at the contractors board which usually leads to a mediation.. at least that's how it works here in Orygun...

NJ requires mediation before you see the judge. 

I backed out of a deal last week where all contingencies were removed; seller wants to keep the EMD, but I am pretty confident I'll get it back in any mediation or arbitration, if necessary.

@Carlos Enriquez  cost of litigating this vs fixing probably is not worth it. and since you did fsbo ... what sales agreement did you use.. if its standard WA form there will be mandatory mediation in these events.. if you used a Stevens ness form maybe not. 

The cheaper option of mediation or arbitration are not available to me as this is a Estate sale through a probate court.

Based on what your/your plumbers research yields of where and due to what the cold exposure is coming from you should ask your contractor to help re-mediate the cold exposure.  

They have denied mediation, refused payment, and we are in litigation. 

If so call them and see if they do mediation.

Here are the details:- She owns 3 commercial properties in Los Angeles- There are not any mortgages on the properties- These properties were in a trust that my uncle and mom both were trustees of, but that is being dissolved (there was mediation and the  3 properties she now has were part of that).

Just because they live in your rental doesn't mean you are responsible for mediating every time two adults have a disagreement.