Frozen Boiler Zone pipe - Antifreeze solvent?

[Brian Karlow]

With this recent cold snap, we've experienced a frozen pipe in one of the zones in our boiler that serves a 4 unit building we just closed on in August. There is a zone for each apartment. We have been heating the apartment with the frozen with the electric wall sleeve unit that has the function to serve as a dual ac/heat unit but this is a temp solution until the weather warms and the line thaws.

My question is have any of you had your boiler service company add anti freeze type solvent to your boiler units to prevent this issue? 

This is currently a rather inefficient building with single pane windows and drafty doors we intend to replace over the next few years and I'm concerned another record cold snap could trigger the same issue again in the near future.  We struggled to keep temps above 67 in the remaining apartments and I've read adding these types of solvents reduces the boilers heat output.... this would be an issue.

Any advise, experience or feedback would greatly be appreciated...thanks in advance!

Brian