Calculating daily average and peak total occupants

This has confused many people.

From the BD&C v4 Reference Guide introduction, Maintaining Consistency in the Application:

“Daily averages take into account all the occupants of a given type for a typical 24-hour day of operation.”

“Peak totals are measured at the moment in a typical 24-hour period when the highest number of a given occupant type is present.”

Note that “transients” and “visitors” means the same thing.

In most cases, I think the numbers in Appendix 2 Default Occupancy Counts would be daily averages.

If you calculate 100 transients, that’s the daily average of total number of visitors. The “peak visitors” is your best guess at the number of visitors in the building during busiest time. This is hard to estimate, as it depends on the type of building and use: For a small restaurant open all day, out of 100 daily average visitors, the peak might be 25, for example.

I wouldn’t worry about being very precise for the number of visitors – the number of peak visitors will affect the number of short-term bike racks, but not much else. And since the minimum number of short-term racks is 4, you’d need more than 160 visitors to require more than 4 bike racks. The daily average visitors is used in the water calculations but changing the number of visitors has only a small impact on the results in the water calculator.

For overnight guest occupancy, as you found, we have the guideline for 1.5 occupants per guest room multiplied by 60%:  

 “Hotel guests are typically considered regular building occupants, with some credit-specific exceptions. Calculate the number of overnight hotel guests based on the number and size of units in the project. Assume 1.5 occupants per guest room and multiply the resulting total by 60% (average hotel occupancy). Alternatively, the number of hotel guest occupants may be derived from actual or historical occupancy.”

The Appendix 2 default occupancy for a hotel doesn’t distinguish between hotels with only guest rooms, and hotels with large secondary functions such a restaurant, retail, meeting rooms, or conference center, which can result in very different numbers of visitors.

Here’s what I’d suggest:

1. Use the USGBC formula of guest room count * 1.5 * 60% to get total daily average hotel guest occupancy.     
2. If the hotel doesn’t have a large secondary function, estimate your visitors as maybe 10 -20% of your total number of overnight guests.
3. Use the Appendix 2 table for employees to estimate the number of employees based on the total area of the hotel. This will be daily average FTE.
4. If the hotel includes a full-service restaurant (not just a breakfast room), use the Appendix 2 numbers to calculate restaurant employees and visitors for the area of the restaurant (including the area of the kitchen). Add those employees to your daily average staff FTE and add those visitors to the daily average visitors.   
5. If the hotel has a significant number of meeting rooms or a conference center, the safest approach would be to ask the owner or operator for some estimates on number staff and visitors. Appendix 2 might give a reasonable estimate of staff and visitors, and these would be probably be in addition to the overnight guests you calculated by the room count. Use your professional judgement to make a reasonable estimate.  

For an example, let's assume a hotel, 6100 square meters in total area, excluding parking, with 180 guest rooms, and no large secondary function:

From Appendix 2, Hotel default occupancy is 139 sq meters per employee (FTE)

6100 / 139 = 44 employees;

180 rooms * 1.5 * 60% = 162 overnight guests.

162 * 15% = 24 transient visitors (daily average). We might assume a peak of 8 visitors.

Total daily average occupancy = 44 + 162 + 24 = 230

Since a hotel operates 24/7, but presumably has a very small night shift, the peak number of employees at any one time might be a few less than the 44 we calculated for daily average. So we might assume:

Total Peak occupancy = 40 + 162 + 8 = 210

As a general note, if we use consistent numbers across all the related credits, follow the guidelines for calculating, use the definitions of “daily average” and “peak” properly, make reasonable and credible estimations when we don’t have exact numbers, and explain how we arrived at our estimates in a short narrative, that’s more important than being 100% accurate. 

Hope that helps!  

David wrote:"In most cases, I think the numbers in Appendix 2 Default Occupancy Counts would be daily averages".

 Is there any statement in the Reference guide or in another document that can confirm that? Are they daily avarages in all cases or in "most cases"?

I feel that this has been unnecessarily confusing for many people over the years. The fact that it hasn't been defined yet is quite strange. I've used the default numbers as average as well, and guessed the peak numbers but I feel strongly that there should be a set formula to apply if we don't have any idea from the client. The submittal form language should match the language in the manual, full stop. 

If peak visitors is only used for short-term bike parking, it seems to me that it should represent the peak at any one point in daytime for both FTEs and visitors. People will not be riding bikes at night. That would also help with the persistent problem of hotels, airports and event spaces. This calculation is seemingly so simple and yet has always been one of the most confusing to document.