I’ve worked on energy models for everything from local schools and libraries to towering hotels and multifamily high rise. The bigger the building or the more innovative the design, the more important it is to get an energy model. Energy models help owners to anticipate operating costs; help designers to optimize building performance; and empower the design and development team to envision schemes that will ultimately contribute to a highly productive workforce in a commercial environment.
Take note! A good energy model is only as good as its inputs!
When I produce energy models for a Paladino clients, I consider several dimensions to the project. Each energy model is made up of building schedules for lighting, fans, hot water, and plug loads based on building type— such as residential or office buildings. USGBC and ENERGY STAR offer default schedules and equivalent full load hours based on these building types. For the most part, these schedules rely on historical usage data.
But work habits are increasingly unpredictable. Offices don’t always operate on a 9:00 am to 5:00 pm schedule and more people are telecommuting. These default modeling schedules do not account for these shifts.
Although the plug load of one computer or monitor may be insignificant, when 20% of an apartment building’s residents are using their apartments as offices the usage adds up. More significantly, tenants working from home aren’t using set back temperatures (included in most default schedules), so heating and cooling loads increase too.
Energy modelers use fraction schedules to determine the percentage of the population that is expected to be at home during a particular period. While that works for occupancy, lighting, and equipment schedules, it doesn’t work for HVAC because thermostats don’t work in fractions. Instead, the energy model has a t-stat schedule that can change setpoints hourly. For example, at 1:00pm, the schedule can either be at 75 or 78 degrees, but not a fraction in between.
Of course, not everyone in a multifamily building will leave at 8:00 am and return at 5:00 pm or be at home in the evening. But by adjusting energy models to accommodate new assumptions, the energy model could provide more useful predictions.
And what about energy models for office buildings? Does the increase in teleworking, decrease energy use in offices? Surprisingly, No! Most teleworkers still come into the office occasionally, and landlords usually light and cool the entire building regardless of the number of occupants. This is particularly true in open work spaces with fewer private offices. So even if just one employee is in the office, all the lights are on. Energy modeling assumptions made for office buildings are less dependent on the number of occupants.
Of course, teleworking isn’t the only change to the work environment that impacts energy models: flexible hours and weekend operation are part of the shift, too. For example, USGBC’s office lighting schedule assumes a 10% load from 6:00 pm to 7:00 pm. For many commercial office clients, this may seem surprising, since it takes only a few employees staying past 6:00 pm. to keep the lights on. But if 90% of employees are present between 6:00 pm and 7:00 pm, the schedule is still valid.
How can this change an energy model?
Ask if these changing norms are captured in your energy model. Ask how can the building loads and schedules are being more accurately predicted. Ask your modeling team if they are considering regional, industry-based, age-dependent, and other variables. While the location and material specifications are known, the details of its tenants are not.
So, although we don’t know the exact percentage of lights that will be on at 3:00 pm in a multifamily building, it is safe to conclude that we do know it is not going to be zero. And every tenant in a multifamily building probably isn’t going to use temperature setbacks on their thermostat.
Our energy modeling team can help you audit your building and tenants and come up with an accurate energy model that will help you save money and make the best decisions for your tenants. It’s easy to request a quote!