Using Lighting Occupancy Sensors in Offices to Control HVAC

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Item ID: 53

Using Lighting Occupancy Sensors in Offices to Control HVAC

Occupancy Sensors: Controlling HVAC & Lighting Systems vs. Controlling Lighting Systems Only

Occupancy sensors compatible with lighting and HVAC systems and capable of managing the HVAC operations within a space depending on occupancy.

Synopsis:

Terminal boxes usually supply a single zone in a large office building. Each terminal box has a minimum flow rate that is often set at the design occupancy for the zone. Occupancy sensors can detect when a zone is unoccupied and can set the ventilation flow rate to zero when no occupants are in the zone (Zhang 2013). Spaces that benefit from having occupancy sensors that turn the lights off when unoccupied could also benefit from having the sensor communicate with the HVAC system for the zone, which would turn off or turn down ventilation air flows when the zone is unoccupied. Some spaces can also allow temperatures to naturally rise or drop, but the potential impact on occupant comfort and productivity needs to be taken into consideration. A single occupancy sensor can do double-duty by controlling both systems. Large spaces that are lightly and intermittently used, such as gymnasiums, theaters, classrooms, and conference rooms, offer the best opportunities for energy savings, which may be as high as 60% of ventilation system energy use. Hotel rooms are another appropriate application, demonstrating savings from 20% to 40%. Greater energy savings (DCV saves a smaller percentage of a much larger baseline energy use) can be achieved with demand-controlled ventilation (see record #166 in this database).These controls can be effectively used in spaces utilizing ductless heat pumps, which tend to have smaller zones.

This technology is most easily incorporated into new construction because it requires a way for the lighting and HVAC systems to communicate with each other, which can most easily be achieved in new construction. For retrofit applications, consider using wireless sensors, which are rapidly becoming more available, more reliable, easier to use and set up, and less expensive.

Energy Savings: 36%

Energy Savings Rating: Extensive Assessment What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Details

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Using Lighting Occupancy Sensors in Offices to Control HVAC

Occupancy Sensors: Controlling HVAC & Lighting Systems vs. Controlling Lighting Systems Only

Occupancy sensors compatible with lighting and HVAC systems and capable of managing the HVAC operations within a space depending on occupancy.

Item ID: 53

Sector: Commercial

Energy System: Multiple Energy Systems--Energy Management

Technical Advisory Group: 2010 HVAC TAG (#3)
Average TAG Rating: 3 out of 5
TAG Ranking Date: 06/29/2010
TAG Rating Commentary:

This has been used before, but not much. In a project I'm involved with now, the lighting control company miswired the manual override controls for lighting in such a way that when the occupant turns off the lights (while the room is occupied) the HVAC goes into the unoccupied mode. Not good, but avoidable. The technology is handy for small spaces such as conference rooms with high intermittent density occupancy. The code CO2 DCV requirements typically kick in only above a certain square footage per room. It may also turn out that it's difficult to maintain adequate calibration on CO2 sensors...I don't know.
Lighting and HVAC controls have evolved in different directions but there is a BACnet working group for lighting.
Not terribly emerging or innovative as it is common practice, at least for my firm.
These systems are generally difficult to integrate with HVAC systems that serve multiple spaces. They require that all spaces in a zone be unoccupied to actually turn off the ventilation. In practice, this rarely occurs and the systems save limited energy.

Technical Advisory Group: 2009 HVAC TAG (#2)

Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
Average TAG Rating: 3.2 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:

Except in some small cases, buildings take too long to heat and cool to respond to short term occupancy without disrupting comfort.
Typically works better if there is a separate occ sensor for the HVAC system. Coordination between trades makes sharing the lighting occ sensor difficult.
This strategy shouldn't require the use of lighting occupancy sensors (which are probably required by code), it would be helpful to identify good retrofit applications and guidelines for estimating and verifying energy savings.
Will probably turn out to be a NC because of cost, but worth considering if this is an improvement over what was available 10 years ago.
I've used it for years, although not always w/o some irritation when it goes out too quickly. Systems tend to be quirky, so might have some occupant resistance. High potential. Will they still be cost-effective with very low power room-scale LED systems (like my new office)? We run way less than 0.5 W/sf, I think.
Do we have lighting or HVAC contractors that are able to do this?
The networked lighting control with temperature sensing give a network of control inputs and are already on a user-freindly interface for management changes
We've seen impressive savings coming out of this technology.

Synopsis:

Baseline Example:

Baseline Description: No occupancy sensors controlling HVAC ventilation fans
Baseline Energy Use: 2.8 kWh per year per square foot

Comments:

Ventilation loads can be estimated from the 2009 NEEA Commercial Building Stock Assessment (NEEA 2009). Tables C-AF6 and C-AF8 provide the typical supply and return fan horsepower per 1,000 sf for all commercial buildings and/or office space. For all commercial buildings, the total fan hp equates to1.08 hp or 0.8 kW/1,000 sf. The input kW is obtained by multiplying by a load of 75% and then dividing by a motor efficiency of 0.9 (hp is a motor output value) to obtain 0.66 kW/1,000 sf. Multiply this value by the number of hours per year (79.3 hours/week x 52 weeks/year) to yield an annual energy use per square foot of 2.75 kWh/sf/year. For office space, the corresponding total connected supply and return fan connected hp is 0.72 hp total x 0.746 kW/hp x 0.75/0.9, or 0.45 input kW multiplied by 58.6 hours/week x 52 weeks per year/1,000 = 1.36 kWh/year. Because this technology can be used in a wide variety of commercial buildings, a baseline ventilation energy use of 2.75 kWh/sf/year is assumed.

Manufacturer's Energy Savings Claims:

"Typical" Savings: 25%
Savings Range: From 10% to 40%

Comments:

From Energy Eye, Inc. (in early 2013 selected assets were acquired by Web Eye, Inc.), HVAC duty cycle reduction of up to 50% is possible with total project savings in the 10% to 40% range of the HVAC energy consumption being common.

Best Estimate of Energy Savings:

"Typical" Savings: 36%
Energy Savings Reliability: 4 - Extensive Assessment

Comments:

J Zhang, et al., at Pacific Northwest National Laboratory (Zhang, 2013) used an energy model to demonstrate that the savings for large office buildings in the BPA service area is about 7% to 8% of the whole building energy consumption when common occupancy sensors are used to turn off terminal box flows when spaces are unoccupied. Savings in Salem, OR, were 3.4 kBtu/sf/year; in Boise, ID, were 3.1 kBtu/sf/year; and Helena, MT, were 3.4 kBtu/sf/year. His analysis takes heating and cooling loads, as well as ventilation loads, into account. Heating loads could be supplied by natural gas.

Zhang’s methodology assumes a 15-minute delay, with unoccupied conference room cooling temperatures allowed to float to 79°F and heating temperatures allowed to decrease to 66°F. Office space is maintained at normal heating and cooling setpoints as multiple offices exist within zones and the probability of all being unoccupied at the same time is low. Energy savings due to occupancy sensor control is predicted to increase (at the expense of comfort) given a reduced sensor delay time (15 minutes to 5 seconds) and if private office space temperatures are allowed to float or decline when unoccupied.

Zhang’s base case building has an annual EUI of 40 to 50 kBtu/sf/year. An EUI of 3.4 kBtu/sf/year is equivalent to 1.0 kWh/sf/year. This is about 1.0/2.75 x 100% = 36.4% of the commercial building baseline ventilation energy use.

Note that the energy savings calculations above only consider ventilation fan energy savings and space conditioning energy for conference rooms. If additional space conditioning temperatures were allowed to vary while unoccupied, additional energy savings would be generated. This can be achieved through demand controlled ventilation (ET #166 Demand Controlled Ventilation), which saves a smaller percentage of a much larger baseline energy use.

Energy Use of Emerging Technology:

1.8 kWh per square foot per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: square foot
Potential number of units replaced by this technology: 1,746,316,000
Comments:

Calculations of the areas where this technology maybe applied are in the table below. These are taken from the preliminary datafor the 2013 update to the Northwest Commercial Building Space Assessment (NEEA, 2014). The percentages of the floor area of eachtype of building to which this technology may apply are rough estimates.

Commercial Building Space in the Northwest where Occupancy Sensor/HVAC Control may be Applied

Space Type	Total Area (s.f.)	Approx. %	Target Area (s.f.)
Large Office	283,240,000	80%	226,592,000
Medium Office	127,610,000	80%	102,088,000
Small Office	149,740,000	80%	119,792,000
Big Box-Retail	134,190,000	80%	107,352,000
Small Box-Retail	247,840,000	80%	198,272,000
High End-Retail	61,960,000	80%	49,568,000
Anchor-Retail	119,630,000	80%	95,704,000
K-12	251,050,000	80%	200,840,000
University	128,170,000	80%	102,536,000
Warehouse	381,740,000	80%	305,392,000
Assembly	238,380,000	100%	238,380,000
Total			1,746,316,000

Regional Technical Potential:
1.76 TWh per year
201 aMW
What's this?

Regional Technical Potential of an Emerging Technology is calculated as follows:

Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)

First Cost:

Installed first cost per: square foot

Comments:

This technology is rarely implemented due to increased costs and control system complexity

Cost Effectiveness:

Simple payback, new construction (years): N/A

Simple payback, retrofit (years): N/A

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Reference and Citations:

J. Zhang, et. al., 01/01/2013. Energy Savings for Occupancy-Based Control (OBC) of Variable-Air-Volume (VAV) Systems
PNNL

IESNA, 01/01/2011. The Lighting Handbook: 10th Edition
Illuminating Engineering Society

ASHRAE, 10/01/2009. Standard Benchmark Energy Utilization Index
ASHRAE

Marty Stipe, 06/01/2003. Demand-Controlled Ventilation: A Design Guide
Oregon Office of Energy for the Northwest Energy Efficiency Alliance

FacilitiesNet, 07/01/2010. What is BACnet Interoperability?
Building Operating Management

David Nelson, 10/27/2014. Electric Lighting Controls in Whole Building Design Guide
National Institute of Building Sciences

SNL, 02/06/2012. Best Practice #117: Integrated Controls Result in Significant Energy Savings
Sandia National Laboratories

Yuvraj Agarwal, et. al. , 04/12/2011. Duty-Cycling Buildings Aggressively: The Next Frontier in HVAC Control
10th International Conference on Information Processing in Sensor Networks (IPSN)

Hong & Fisk, 01/01/2010. Assessment of Energy Savings Potential from the Use of Demand Controlled Ventilation in General Office Spaces in California
Lawrence Berkeley National Laboratory

CADMUS, 12/21/2009. Northwest Commercial Building Stock Assessment (CBSA): Final Report
Prepared by the CADMUS Group for the Northwest Energy Efficiency Alliance

Rank & Scores

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Using Lighting Occupancy Sensors in Offices to Control HVAC

2015-1 Commercial HVAC TAG (#11)

Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
TAG Ranking: 11 out of 29
Average TAG Rating: 3.2 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:

Except in some small cases, buildings take too long to heat and cool to respond to short term occupancy without disrupting comfort.
Typically works better if there is a separate occ sensor for the HVAC system. Coordination between trades makes sharing the lighting occ sensor difficult.
This strategy shouldn't require the use of lighting occupancy sensors (which are probably required by code), it would be helpful to identify good retrofit applications and guidelines for estimating and verifying energy savings.
Will probably turn out to be a NC because of cost, but worth considering if this is an improvement over what was available 10 years ago.
I've used it for years, although not always w/o some irritation when it goes out too quickly. Systems tend to be quirky, so might have some occupant resistance. High potential. Will they still be cost-effective with very low power room-scale LED systems (like my new office)? We run way less than 0.5 W/sf, I think.
Do we have lighting or HVAC contractors that are able to do this?
The networked lighting control with temperature sensing give a network of control inputs and are already on a user-freindly interface for management changes
We've seen impressive savings coming out of this technology.

2010 HVAC TAG (#3)

Technical Advisory Group: 2010 HVAC TAG (#3)
TAG Ranking: 10 out of 36
Average TAG Rating: 3 out of 5
TAG Ranking Date: 06/29/2010
TAG Rating Commentary:

This has been used before, but not much. In a project I'm involved with now, the lighting control company miswired the manual override controls for lighting in such a way that when the occupant turns off the lights (while the room is occupied) the HVAC goes into the unoccupied mode. Not good, but avoidable. The technology is handy for small spaces such as conference rooms with high intermittent density occupancy. The code CO2 DCV requirements typically kick in only above a certain square footage per room. It may also turn out that it's difficult to maintain adequate calibration on CO2 sensors...I don't know.
Lighting and HVAC controls have evolved in different directions but there is a BACnet working group for lighting.
Not terribly emerging or innovative as it is common practice, at least for my firm.
These systems are generally difficult to integrate with HVAC systems that serve multiple spaces. They require that all spaces in a zone be unoccupied to actually turn off the ventilation. In practice, this rarely occurs and the systems save limited energy.

2009 HVAC TAG (#2)

Technical Advisory Group: 2009 HVAC TAG (#2)
TAG Ranking:
Average TAG Rating:
TAG Ranking Date:
TAG Rating Commentary:

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