Hello everyone and thanks for taking the time to read this post!!

I just got hired at a company as an HVAC/R designer. Before that I worked as an HVAC/R sales engineer for about 2 years for a contractor before I had to leave for medical reasons. So I have been out of the HVAC field for 2.3-3 years before I landed the current designer position. I knew nothing about HVAC before my sales engineer job and had to be trained how the company works as well as the HVAC end of things, so I would say my over all HVAC experience is about 1.5 years.

The company that hired me now knows I have very good CAD skills in both AutoCAD and Revit, and the resume I provided indicates the amount of experience in HVAC.

I've been given a project that involves a complete renovation of a building. This is something very new to me, due to the size and nature of the project.

This is where I seek direction:

Here is a brief and general scope:

There are two buildings involved, building A and B. Each building is roughly 45,000 gross square feet. Both buildings were built in the early 60's are very similar regarding design architecturally, structurally, and mechanically (only how the pipes are laid out for zoning). Each building has 2 wings and 3 floors. Both buildings are heated by a hydronic system in building A. The project consists of renovating building A. Both buildings are used as office spaces, and none of which have AC.

Going back to the what is there. There are 2, grossly over sized, boilers in building A that is providing heat for both buildings. Each building has 2 zones. Each zone only services one wing. The riser diagram for the heating is straight forward. Supply goes up while each floor is branched off to service the fin tubes and goes into the return. So while one side is receiving 180 F, I'm assuming the other is only getting 140F - 120F.
Building A is getting upgrading but not B. A will be getting new windows and doors, re-insulation of the walls, and a new roof, while B will be left the way it is.

I need to come up with a new heating and cooling design but I still need a lot to review and I have lots of questions.

For heating, it was suggesting that I install 3 new boilers. Where each boiler (2 at a time) will have to run at 40% capacity and if need to, run at 50% during the very below 0 days. One boiler will be off line and serviced while the other two will be running.

As for cooling. I'm given 2 options.

Option 1 will be using split systems that will service the entire building A, while I need to come up with a hydronic system that will service building B, and A that will use radiant heating panels (in the ceiling).

Option 2 will be involving chillers. The hydronic heating system will include 3 boilers to service A and B in addition to using chillers to service building A. The system in A will be using valances for both heating and cooling.

I was given 2 books to use as for a refresher. ASHRAE 2011 HVAC Applications and the 2012 HVAC System and Equipment. I also have the 2001 fundamentals.

I'm looking for advice when using these books, how to size up 3 boilers if each needs to run at 40% capacity while each building will have different heating loads, what type of chillers used in the option 2 applications and if glycol and or any other type of cooling with water will be involved. The best way to zone this out, and info on valances which is new to me.

I appreciate any input that can help me get in the right direction.