What questions do you ask when doing sanity checks on a model?

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I love this question and am looking forward to others answers, here are a few ways we check our models:

1. We take the overall EUI of the building and compare it to CBECS data and other information we have on whether this is a realistic number. It is either miles out or in the right area.

2. We take the EUI of individual outputs, say, heating, cooling, fans etc... and we look and compare those EUIs to other projects we have done and use judgement as to whether this is reasonable for the climate and what we know about the building.

3. We look at the unmet load hours and which zones aren't meeting their loads.

4. We take a look at how the energy flows through the system, so in EnergyPlus we can do this by checking the nodes at each point in the AHU and in the zones and in the plants. From this you can check to see that all your components are working correctly. There is more on this on the question MattSteen has mentioned above.

From there it is a question of finding the issues and checking your inputs from the issues that have come out rerunning and reanalysing.

Oh this is too good!

... How many UnmetHours are there?

It had to be said.

Thanks for asking a really good question, this motivated me to organise my thoughts on things to check.

Generally, I find IES to be pretty poor when it comes to warnings, errors and reporting. I go through the following checks numerous times through an energy model process. Compared to EnergyPlus, where standard reporting of wanrings, errors and model integrity are produced automatically, IES leaves much to be desired (in my experience)

That said, the best checks to do at the early stage are those that you have to do at the end, i.e * for LEED, check everything that goes into the building summary report * sensitivity tests are a good way to spot things that aren't set up right. The pity of these, in my experience is that they are done at the end of the energy modelling process, when they are most useful more early on.

In IES, here are some checks I do

Basic Checks

• Site orientation
• Application of correct gain and variation profiles ( no people in ceiling voids !)
• Variation of loads (diversity) within air handling unit group (this is a NABERs thing)

Gains and Temperature Checks

• select all conditioned zones, range check temperature from 8am to 6pm mon-fri - are hours out of range reasonable ?
• do likewise on all zones that should be unconditioned - to check that these are not mistakenly conditioned and using energy..
• check magnitude and variation of internal gains
• check solar gains are reasonable - i.e east/west facing zones are getting sun at right times
• run the 'Cooling Report' check the cooling loads are reasonable <150 Watts/sq.m for a perimeter and ~60 Watts/sq for internal (or as appropriate to your project)

ApacheHVAC Checks

• airflow rates across the supply air fan - do these respect minimum outdoor air flow rate ?
• airflow rates across the supply air fan - is there an increase of outside air for the economy cycle - check against outdoor temp and humidity ( i copy results to excel)
• air temps across cooling and heating coils - check simultaneous heating and cooling is not occuring
• volume flow rates and supply air temperatures to VAV boxes - variation and magnitude - should find some that are maxxing out on a hot day
• select a hot day, chart the cooling loads in all zones, find a zone that appears to be at peak cooling capacity, check air flow rate is at maximum and supply air temp is at minimum.

A few things to get you started:

1) EUI, kWh/sf, W/sf, therms/sf, $/sf -- all of these should be benchmarked as if the building was currently in operation, do the values make sense?

--- also the consumption values may change seasonally, do the patterns make sense? --- cfm/ft2 match expected values for auto-sized systems.

2) Does major HVAC equipment operate throughout it's capacity? (i.e. reconcile designed capacities with modeled loads)

--- check auto-sized capacities against ASHRAE rules of thumb if not using designed capacities. --- if you have designed values or actual values, verify against those capacities for major HVAC equipment

3) If the modeling package includes a rendering feature, does it match the architect's drawings for new buildings or photos of the actual site for existing buildings.

4) See previous thread on this site about calibration methods for existing buildings...this is an area with a wealth of resources.

5) For new buildings, do the results track with the project's goals? If not that will need to be resolved either by changes to the model or revising the goals.

6) Energy end-use breakdown should be compared to other projects, variances explained.

7) Calculate average annual efficiencies for primary equipment, are they reasonable?

8) Unmet hours, and/or zone temperature reports used to show that conditions are met appropriately. Verify that air temperatures and water temperatures are reasonable.

9) Verify that correct weather file was used, any elevation adjustments are made if needed.

10) Verify modeled building area against the design or actual area. Don't count the plenums or dummy zones.

11) Assess any key assumptions that were made. Perform sensitivity analysis to determine what effect might result if the assumption was too high/low/etc.

Lots of other factors that might be specific to your model. Too many to list!

As far as someone else's model, I'd ask them some of these same questions.