HVAC System selection

Ciaran, whole essays could be written on this, and I'm sure there would be some difference of opinion. I think you'll need to put out more details to get a good response here. I will say that LEED is generally good at rewarding projects for using less energy on a predicted basis, period. The right system to do this will be different for every project. Modeling is a good way to try out different possibilities.HVAC is the wrong place to start the discussion, though. Start by saving energy with an efficient envelope.

In general boiler/chiller systems do not score as well as ground source heat pumps. This does not mean that GSHP are always the best answer. It just means that the baseline used for comparison is probably poorly defined in Appendix G. Over a certain size the baseline heating is electric resistance so in heating climates points tend to follow. That does not mean that it is your best choice. Do not let LEED point pursuit on this particular issue be the determining factor in your system selection. Unfortunately the simple pursuit of the maximum number of LEED points does not always give you the best solution for your project or even for the environment. The details of why this is so could be a rather lengthy essay as well.