Lighting Power Density using ElumTools

Since day one of ElumTools, Revit has coexisted and offered several powerful tools for electrical analysis, including Lighting Power Density reporting functionality.  The latest releases of ElumTools include new functionality to make it easier to leverage Revit’s LPD tools as a natural part of the typical ElumTools workflow.

The Create Schedule command now includes some additional parameters which are associated with Rooms and Spaces.  To take advantage of the new electrical parameters, the first step is to create and configure Spaces in the host model.

Once you have Spaces set up, you need to make some decisions about how you wish to use each parameter.  Here is an overview of the role played by each.

Specified Lighting Load

These are intended to be reporting parameters and are fairly easy to define.  At a high level, the Specified Lighting Load parameters are values that are simply entered by the user as a design goal.  They are in no way connected to the Lighting Fixture families which are actually placed in the model.

Specified Loads are defined in the Electrical Instance Parameters of each Space.  See below.  Space Lighting Loads can either be specified “By Space Type”, particularly handy for code compliance evaluation, or individually on a per Space basis.

Actual Lighting Load

Actual Lighting Load is intelligently determined by Revit, based on the Luminaire family instances actually placed in the model.  This is intended to help ensure final design proposals meet the design specification and applicable electrical codes.

For Actual Lighting Loads to calculate as expected, all luminaire families must have a properly configured Electrical Connector.  This is a somewhat complex area and will be the subject of a future blog post. Conveniently, however, all of the families in the Built-in ElumTools library have the Electrical Connector set up “out of the box”, as of version 2018.4.

The luminaire families ship with a default load of 0VA, since each family could potentially represent many kinds of fixtures (with very different loads).  To get accurate LPD numbers, the user simply needs to define the Apparent Load Type Parameter appropriately for each fixture Type.


For Revit to compute the Actual Lighting Loads, the appropriate checkbox must be checked in the Electrical Settings. Otherwise, all Actual Lighting Loads will be reported as zero.

Computation of Lighting Loads can sometimes be a performance intensive process.  Therefore, it can be convenient to disable the load calculation functionality when working with larger models and/or on slower systems.



Luminaire Family Validation Made Easy

When a calculation is invoked, ElumTools automatically checks all Lighting Fixture families in the environment to determine whether the family has valid photometry applied.  If the program detects luminaires without photometry it throws a handy warning, alerting the user of the problem.  This is especially helpful for newbies as a quick check to see whether or not all the families are in order.

However, sometimes this warning will be triggered at times when the user actually intentionally doesn’t have a  photometric file assigned.  Take the case below.

In this case, ElumTools is warning the user that it found 4 table lamps (60 W Incandescent) without valid photometry assigned.  For most serious illumination engineering projects, this is what you want (a table lamp typically won’t be an integral part of a commercial lighting solution).  Often these kinds of families will be included in the Revit project for Rendering purposes, but are not germane to quantitative lighting analysis.

What to do?  You could of course click the “Do not show me this again” check box.  But that is a global change that will prevent the warning from popping in all cases, not just this particular one.

The latest releases of ElumTools now allow the user to “approve” individual Luminaire Types directly in Luminaire Manager.  This lets you suppress the invalid luminaire warning on a case-by-case basis.

By default, ElumTools will throw a warning for all Luminaire Types which show a “Red X” in Luminaire Manager (the way it has always worked).

Now, Luminaire Manager also gives the opportunity to click the “red X” and change it to a more friendly “green X”.  Family Types with green X’s still do not contain valid photometry.  But ElumTools will interpret them as “approved” and will not show a warning.

Similarly, you can also approve Luminaire Family Types which DO have valid photometry assigned.  This has no effect on the behavior of ElumTools (apart from changing the icon in Luminaire Manager) and is simply convenient for documentation.  It is in no way a requirement to approve Luminaire Types prior to calculating.

Behind the scenes, ElumTools stores whether a Family Type has been approved, as a shared parameter called “ElumTools Validated”.  This can be easily scheduled which can serve as a quick way to see which families still need validation (particularly useful on large projects).  Revit even provides some conditional formatting tools to pretty things up.  What fun.

Why Can’t I Suppress the Rendering?

Often when using ElumTools, you won’t be interested in a rendering and will only need the point-by-point illuminance values, and perhaps the associated statistics (avg, max, min, ratios, etc.).  A common question we get is if there is a way to suppress the rendering and have ElumTools only return the numerical results when calculating (usually in the interest of faster calculation times).

The answer to this question is no.  But it isn’t because we neglected to add the feature :).  ElumTools, like AGi32, uses a process called radiosity to consider all the interreflected light and its contribution to the point-by-point results.  With radiosity, the math to produce the calculation point values is identical to the math required to produce the rendering.  In other words, the point-by-points are a by product of the rendering.  So, were the option to suppress the renderings given, the calculation time would remain roughly the same.

There are, however, some things you can do to speed things up, particularly if you are daring enough to compromise on calculation accuracy.  This help article contains some handy tips. These can be particularly useful during design iterations when only approximate computations are required.  Then the settings can always be ratcheted up for final deliverables, when greater accuracy is needed.   Layout assistant can also be a useful “quick calc” tool to get a rough idea of fixture quantities, early in the design process.

Layout Assistant as a “Quick Calc” tool

The Layout Assistant is an easy avenue to quickly estimate average illuminance levels and make adjustments to luminaire quantities as needed to meet your criteria.  To start, simply enter the quantity of luminaires you plan to use.  Layout Assistant will immediately display an average illuminance estimate for the quantity entered, as well estimates for plus or minus 1 luminaire.  layout-assistant-quick-calc-1

The estimation algorithm used to produce the estimate is significantly more powerful and accurate than the Zonal Cavity based methodology built into Revit.  Layout assistant employs the same radiosity engine used by the calculate commands , and estimates results quickly by applying a very coarse mesh to the environment.

There are many options in the Layout Assistant dialog to tinker with the luminaire positions.  When you’re happy with your layout, place the luminaires in the Revit model by clicking “ok”. If you want more confidence in the illuminance estimate first, perform a full calculation using the “Calculate” button.