(Appologies for double posting, I posted the same question on the v4-forum. Just realized it is probably more appropriate on the v4.1 page.)

Hi everyone

We are trying to make some strategic decisions and would be happy about some feedback. First a short summary, two questions are below.

Situation is an existing office building with moderate renovations (C+S), some key points:

  • nearly everywhere curtainwall facade, U-value facade around 2.4 W/(m²K) -> the facade is in good condition and will not be renovated, apart from some solar shading that must be redone
  • roofs will be renovated and insulated
  • cooling was provided through air with inefficient chillers -> after renovation, there will be cooled ceilings and purchased chilled water, air volume based on hygienic requirements
  • heating is and remains purchased heat with radiators and floor heating
  • lighting is replaced everywhere by LED

Using v4:

  • The building envelope of the baseline building would be the same as the existing building, prior to renovations. As the envelope barely changes, this will provided hardly any energy savings.
  • DES:
    • Path 1: both baseline and proposed modelled with purchased heat and chilled water, only downstream equipment, identical utility rates, efficiency 100 % -> no energy savings
    • Path 2: Baseline per Appendix G (efficiency 80%), DES virtual plant (efficiency maybe 85 %)
  • Evaluation: comparison of energy costs -> depending on DES modelling path, but we don't expect high energy cost savings.

 
Using v4.1:

  • The building envelope of the baseline building would be based on App. G in ASHRAE 90.1-2016 (Table G3.4-4), which would result in moderate savings in heating and cooling energy.
  • DES:
    • Path 1: both baseline and proposed modelled with purchased heat and chilled water, only downstream equipment, identical utility rates, efficiency 100 % -> no energy or GHG savings
    • Path 2: Baseline per Appendix G (efficiency 80%), DES virtual plant (efficiency maybe 85 %), but high savings on GHG
  • Evaluation:
    • comparison of energy costs -> moderate energy cost savings, but the performance rating method seems thougher to gain credits
    • comparison of GHG -> with DES Path 2, hopefully high savings on GHG

Question 1: Would you recommend v4 or v4.1 for this project? It is rather limited information, feel free to ask follow-up questions.

Question 2: Is it correct, regarding DES modelling, that path 1 does not allow to take credit for GHG savings?

Thank you for your time!

Sarah