Jon Morgan's profile - activity

My current approach is to use a python script to create a batch file that includes all the simulations, one per line. A

After a bit of thought ... maybe a better way to have asked the question would have been ...

How best to configure an infiltration object in E+ to match known performance obtained from blower-door tests?

From a standard test we can obtain characteristics such as ACH50, flow coefficient, pressure exponent, equivalent leakage area etc. These test results are for the whole building so it makes sense for the E+ model to work on a whole building basis.

The FlowCoefficient method allows flow coefficient and pressure exponent to be specified and then determines infiltration rates based on the other coefficients (to account for stack and wind pressures) but it's going to be tricky to implement well as previously discussed.

I would prefer to use the DesignFlowRate method but it's unclear to me how this method can be configured to match test results. The documentation says that the design flow rate is the maximum amount of infiltration expected at design conditions - but what value from the measurement data and what coefficients should be used (appreciating that the test does not provide information on site exposure or stack pressures)?

I hope this question is a little clearer - ultimately I guess I'm looking for some kind of verification that the test performance is being replicated in the model.

I might take a look at the Airflow Network sometime but not sure how I'd relate this back to measured parameters - sounds like an iterative process to adjust leakage areas etc to match ACH50 from the blower door test - sounds hairy. And as you suggest - there is no point trying to calculate answers to a higher level of accuracy than the input assumptions (real people tend to be unpredictable ...).

Thanks for the feedback - the E+ documentation for ZoneInfiltration:FlowCoefficient provides a table of coefficients for different levels of site exposure and number of building stories but I haven't seen a similar table for the ZoneInfiltration:DesignFlowRate method. I'll spend some time digging into ASHRAE Fundamentals and see what I can figure out - the main effect I'd like to capture is site exposure - windy rural sites vs urban sites for example.

I've recently been investigating the different options for setting infiltration rates in Energy Plus and am hoping for some confirmation and/or correction of how I understand the different approaches available. The question is not so much about the inputs or equations for each model but rather how they can be practically used in Energy Plus.

ZoneInfiltration:DesignFlowRate

This is the model I use most often with a defined air-change rate and primarily for commercial buildings. In this case the air change rate is constant (ignoring the modifier schedule) and the infiltration rate varies with zone volume only. Is generally fine for code compliance - which is the bulk of the work I do.

ZoneInfiltration:FlowCoefficient

This model would appear to be more appropriate for residential applications but can't figure out how it can be practically applied to a multi-zone model. From blower-door tests I can get all the necessary parameters, however, this model calculates a volume flow rate that appears to be independent of any zone parameters (e.g. surface area or volume). If I create an infiltration object for each zone separately and use the experimental parameters then the same whole-building infiltration rate would be applied to each zone - which would be incorrect. (I ran a simulation today using this approach and the mass flow rate was similar but not the same for each zone - I can't explain the differences)

Given the level of uncertainty around infiltration rates it may be sensible to stick to the first option, however, it does seem valuable to be able to take into account site exposure, building height etc. which are available with the second option.

Any thoughts greatly appreciated.