Report: HVAC occupancy sensors could slash building energy demand by 18%

A single advanced building control now in development could slash 18 percent — tens of thousands of dollars — off the overall annual energy bill of the average large office building, with no loss of comfort, according to a report by researchers at the Department of Energy's Pacific Northwest National Laboratory.

"An 18-percent boost in building energy efficiency by modifying a single factor is very, very good," said team leader Michael Brambley. "The savings were much greater than we expected."

The report is based on extensive simulations of the impact of one type of advanced building control now in the offing in the building industry. The device is capable of customizing the level of ventilation by sensing the number of people in different areas or zones of a building and then adjusting fan speed and air movement accordingly.

That's a big change from the way most sensor-based ventilation systems operate now: Currently, if there is even a single person in a room, ventilation runs full blast, as if the room is full.

But a room with just a few people doesn't need nearly as much ventilation as a crowded room. Why have a fan pushing around air for ventilation for 100 people if there's only one individual in the room? It's like airing out your house completely because there's one small whiff of bacon still in the kitchen.

"This is the reason you often feel cold when you're in a big space like a conference room or cafeteria without a lot of people," said engineer Guopeng Liu, the lead author of the report. "Technology available today doesn't detect how many people are in a room, and so air flow is at maximum capacity nearly constantly. That creates a big demand to re-heat the air before it enters the rooms. It takes a lot of energy to keep you comfortable under those circumstances."

Current occupancy sensors have helped the nation save significant amounts of energy by automatically turning off lights when they're not needed. But the team estimates that the more advanced versions still to come — which count the number of people in rooms — will save approximately 28 times as much energy, when used both for lighting and ventilation, compared to current sensors.

The project began three years ago when Liu began exploring the idea of adjusting air flow to different zones of a building based on the precise number of people in a room. That "decision" of how much air to move takes place in a piece of equipment known as a variable air volume terminal box. The new sensors that count people are likely to become available within the next few years. While they are currently very expensive, the technology is improving rapidly and the cost is expected to come down, Brambley noted.

"We undertook this study to try to determine if this is a technology worth pursuing vigorously. The answer, clearly, is yes. Using the number of people in a room as a factor in determining the level of air flow offers great promise for saving energy and money," said Brambley.

To do its study, the team focused on a prototypical large commercial office building whose footprint is 160 feet by 240 feet — about 80 percent the size of a football field. The model building is 12 stories and also has a basement, giving it a total of about 500,000 square feet. Such buildings in the United States take up more than 4.4 billion square feet. To visualize the size, think of the land area covered by Seattle — and a little bit of its suburbs — as a giant one-story building.

Brambley's team programmed the simulation to heat a building if temperatures dipped below 70 degrees Fahrenheit and to provide cooling at temperatures beginning at 75 degrees. Numbers were set back 10 degrees on the evenings and weekends. Occupancy patterns were estimated based on past studies.

In 13 of the nation's 15 climate regions, the PNNL team estimates that the advanced controls would save at least $40,000 annually for each building similar in size to the one modeled in the study. In two cities, Baltimore and Fairbanks, the savings stretch to more than $100,000 each year, because of the greatly reduced need to heat new air being pumped in from the cold outdoors. Even in the two cities where the savings would be the least, El Paso and Miami, estimated savings come to $33,400 and $23,500, respectively.

"While buildings have gotten much more efficient in the last two decades, there are still huge gains to be had," noted Brambley.

Since just a small percentage of office buildings in any given year are newly built, Brambley and Liu say a prime target for these advanced controls is retrofitting existing buildings. Liu notes that technology has leaped forward since 1989 — the year the average large office building was built - offering huge energy gains even with the expense of retrofitting.

Since heating and cooling and related equipment usually draw much more energy than lighting, those systems offer a greater opportunity for savings. The team found that advanced controls for ventilation offer about eight times as much savings as advanced controls for lighting, where lights are turned off more quickly than is now common after everyone leaves a room. When the HVAC (heating, ventilation, and air conditioning) system alone is considered, the advanced controls cut energy usage by nearly 40 percent.

A stumbling block to the new technology is that certain advanced controls might require modification to some building codes. For instance, current codes require some ventilation at all times no matter how many people are present. Brambley thinks the options are worth considering, given the energy savings at stake.

In addition to Brambley and Liu, mechanical engineer Jian Zhang and engineer Robert Lutes contributed to the project. The work was support by DOE's Office of Energy Efficiency and Renewable Energy.

A research project to test next-generation building sensors at Carnegie Mellon University provoked intense debate over the privacy implications of widespread deployment of the devices in a new 90,000-sf building. The light-switch-size devices, capable of measuring 12 types of data including motion and sound, were mounted in more than 300 locations throughout the building.

Affordable Housing | Apr 7, 2023

Florida’s affordable housing law expected to fuel multifamily residential projects

Florida Gov. Ron DeSantis recently signed into law affordable housing legislation that includes $711 million for housing programs and tax breaks for developers. The new law will supersede local governments’ zoning, density, and height requirements.

Department of Energy makes $1 billion available for states, local governments to upgrade codes

Energy Efficiency | Apr 7, 2023

Department of Energy makes $1 billion available for states, local governments to upgrade building codes

The U.S. Department of Energy is offering funding to help state and local governments upgrade their building codes to boost energy efficiency. The funding will support improved building codes that reduce carbon emissions and improve energy efficiency, according to DOE.

Structural steel gas station experience for electric vehicles rendering

Steel Buildings | Apr 6, 2023

2023 AISC Forge Prize winner envisions the gas station of the future

Forge Prize winner LVL (Level) Studio envisions a place where motorists can relax, work, play, shop, or perhaps even get healthcare while their vehicles charge.

Architects | Apr 6, 2023

New tool from Perkins&Will will make public health data more accessible to designers and architects

Called PRECEDE, the dashboard is an open-source tool developed by Perkins&Will that draws on federal data to identify and assess community health priorities within the U.S. by location. The firm was recently awarded a $30,000 ASID Foundation Grant to enhance the tool.

Architects | Apr 6, 2023

Design for belonging: An introduction to inclusive design

The foundation of modern, formalized inclusive design can be traced back to the Americans with Disabilities Act (ADA) in 1990. The movement has developed beyond the simple rules outlined by ADA regulations resulting in features like mothers’ rooms, prayer rooms, and inclusive restrooms.

1550 on the Green, a new office tower in Houston, will be delivered next year.

Market Data | Apr 6, 2023

JLL’s 2023 Construction Outlook foresees growth tempered by cost increases

The easing of supply chain snags for some product categories, and the dispensing with global COVID measures, have returned the North American construction sector to a sense of normal. However, that return is proving to be complicated, with the construction industry remaining exceptionally busy at a time when labor and materials cost inflation continues to put pricing pressure on projects, leading to caution in anticipation of a possible downturn. That’s the prognosis of JLL’s just-released 2023 U.S. and Canada Construction Outlook.

HydroSKIN is a hyperactive façade that absorbs rainwater for evaporative cooling. Photo: Institute of Lightweight Structures and Conceptual Design

Cladding and Facade Systems | Apr 5, 2023

Façade innovation: University of Stuttgart tests a ‘saturated building skin’ for lessening heat islands

HydroSKIN is a façade made with textiles that stores rainwater and uses it later to cool hot building exteriors. The façade innovation consists of an external, multilayered 3D textile that acts as a water collector and evaporator.

Market Data | Apr 4, 2023

Nonresidential construction spending up 0.4% in February 2023

National nonresidential construction spending increased 0.4% in February, according to an Associated Builders and Contractors analysis of data published by the U.S. Census Bureau. On a seasonally adjusted annualized basis, nonresidential spending totaled $982.2 billion for the month, up 16.8% from the previous year.

Sustainability | Apr 4, 2023

ASHRAE releases Building Performance Standards Guide

Building Performance Standards (BPS): A Technical Resource Guide was created to provide a technical basis for policymakers, building owners, practitioners and other stakeholders interested in developing and implementing a BPS policy. The publication is the first in a series of seven guidebooks by ASHRAE on building decarbonization.

Currently Reading

Report: HVAC occupancy sensors could slash building energy demand by 18%

Tags

Smart Buildings | Apr 7, 2023

Affordable Housing | Apr 7, 2023

Energy Efficiency | Apr 7, 2023

Steel Buildings | Apr 6, 2023

Architects | Apr 6, 2023

Architects | Apr 6, 2023

Market Data | Apr 6, 2023

Cladding and Facade Systems | Apr 5, 2023

Market Data | Apr 4, 2023

Sustainability | Apr 4, 2023

Most Popular Content

Magazine Subscription

Get our Newsletters

Follow BD+C: