Estimating the Peak Visitors

It's always been confusing that in the appendix for default occupants the 'Office' use gives an area per employee but not for transients (visitors).

Project teams just need to use their "professional judgement" and come up with their own credible estimate of visitors. You could do an informal poll within your own office and a few others of how many visitors they typically have in a day. In some types of offices conference room use might give some clues.

The number of visitors is mostly used for the water use calculations and # of bike racks, but you'll find that you can make big changes to that number and it barely moves the needle on water consumption, so it doesn't make sense to obsess about it too much.

For anyone's reference, the glossary doesn't define visitors, transients, peak visitors... but in the introduction of the reference guide/ credit library section "maintaining consistency in the application" USGBC does define:   

     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.

For example, say there's a daily average of 40 visitors over the course of a typical day, the peak visitors MUST be less - say, 10 people - estimated for the busiest time of day.

David, I have a question regarding peak visitors.

I am wondering if this number of visitors are calculated in one time of the day or in a period of time of the day. 

Cause I thought that these visitors where taken in the busiest period time in one day, for example in my project I have the busiest period from 11:30 to 13:30, in each hour I have 48 peak occupants so I have multiplied this number in 2 (2hours).

I`ll be very thankfull if you can answer and help me with my doubt,

Best regards.

Maria,

Here’s a new guideline we might consider: if the number of peak visitors is less than 160, don’t worry about being precise.

For calculating short term bike storage racks, 2.5% of 160 peak visitors = 4 spaces, which is the minimum we need to provide, so any project with fewer than 160 peak visitors will still have to provide  four (4) short-term spaces.

The peak visitors number is calculated for one time of the day, so in your case it is probably 48 peak visitors. We only need to estimate what will be the greatest number of visitors in the building at any one time. We are using this number to provide enough short-term bike racks for these visitors, so in your situation you probably don't need to increase that number by two for your two busiest hours. 

Here's one situation you might need to assume more than 48 peak visitors for a project: let's imagine a business that has scheduled events, like a testing center. Let’s assume they often have 48 people taking a two-hour test. Let's also assume that all tests start and finish at the same time, say 9:00-11:00, 11:00 - 13:00, 13:00 - 15:00. In this scenario, 48 visitors would be finishing their test at 11:00 while the next group of 48 visitors would be arriving. During the transition from one test to another there could be as many as 96 visitors.

But this would be an unusual situation. Most buildings would have visitors arriving and departing at different times, so estimates and averages for just one busiest time should be fine.  

And in your example, for 48 visitors we need 2.5% x 48 to calculate the number of short-term bike storage racks. 48 * 2.5% = 1.2 which we round up to the next whole number, 2. But the minimum number of short-term spaces we have to provide is four (4), so estimating the number of visitors doesn’t need to be very precise with relatively few peak visitors.  

In the FAQ section, there's good advice to estimate the total number visitors (not the peak) at 10% of your FTE occupancy when you don't have good data on building visitors. So a building with 1000 FTE occupants (employees) might have 100 total visitors, and maybe 30 to 40 peak visitors. Either way, it's still four short-term bike racks... 

Hope that all makes sense.