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Summary

Energy Recovery Ventilator with Heat and Membrane Humidity Exchangers for Commercial Application

Commercial Ventilation: Heat and Humidity Recovery vs. No Energy Recovery 

An air-to-air heat exchanger that transfers both sensible and latent heat between the exhaust air stream and the fresh air stream using one of a number of membrane-based technologies.

Synopsis:

Energy recovery ventilators (ERVs) are similar to heat recovery ventilators (HRVs) (ET #20 Heat Recovery Ventilator for Commercial Application) in that they transfer sensible heat energy from outgoing exhaust air to incoming outdoor air. Unlike HRVs, ERVs also transfer the latent energy of the moisture in the air. The ERV recaptures cooling and heating energy while controlling humidity extremes without mixing the two air streams. The key to this innovation is polymer membranes that are moisture-permeable, allowing humidity to be exchanged between the indoor and outdoor airstreams.

In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air through membrane exchange without allowing odors or pollutants in. In hot and humid climates, ERVs help to maintain (but do not reduce) the interior relative humidity (RH) in the process of cooling outside ventilation air. Reducing the RH in the summer decreases the mechanical cooling required, which makes this technology particularly suitable in hot and humid or very cold climates. A small handful of companies (e.g., Building Performance Inc. and dPoint) offer this technology using a microbe- and mold-resistant polymer (e.g., polypropylene) membrane that requires no moving parts (other than the HVAC fans external to the ERV).

Preconditioning the supply air can reduce energy consumption for heating and cooling. A study by the National Research Council of Canada showed that the ERV saved an additional 20% of dehumidifying energy and reduced cooling costs by 12%. The U.S. DOE Building Technologies Program states that enthalpy/energy recovery devices can save 65% of the energy consumed to condition outside air.

Energy Savings: 65%
Energy Savings Rating: Limited Assessment  What's this?
LevelStatusDescription
1Concept not validatedClaims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2Concept validated:An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3Limited assessmentAn unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4Extensive assessmentAdditional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5Comprehensive analysisResults of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6Approved measureProtocols for technology application are established and approved.
Simple Payback, New Construction (years): 1.2   What's this?
Simple Payback, Retrofit (years): 1.5   What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

Status:

Details

Energy Recovery Ventilator with Heat and Membrane Humidity Exchangers for Commercial Application

Commercial Ventilation: Heat and Humidity Recovery vs. No Energy Recovery 

An air-to-air heat exchanger that transfers both sensible and latent heat between the exhaust air stream and the fresh air stream using one of a number of membrane-based technologies.
Item ID: 461
Sector: Commercial
Energy System: HVAC--Heat Recovery
Technical Advisory Group: 2010 HVAC TAG (#3)
Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
Average TAG Rating: 2.58 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:
  1. This is required by code in several applications, the PNW doesn't need the additional cost for humidity exchange and if the heat is gas, the savings will be gas.
  2. Would be interesting to hear about, although a longshot for our climate.
  3. For both residential and commercial applications, we need to get more analytical. With the relatively mild climates of the NW, do the fan power requirements eat up the energy savings, unless we pay for bypasses around the ERV? What buildings actually need enthalpy control, instead of just sensible heat, and in what climate zone?
  4. I am unsure about this technology in retrofits.
  5. Unless you have a high demand for dehumidification, this technology is seldom cost-effective.

Synopsis:

Energy recovery ventilators (ERVs) are similar to heat recovery ventilators (HRVs) (ET #20 Heat Recovery Ventilator for Commercial Application) in that they transfer sensible heat energy from outgoing exhaust air to incoming outdoor air. Unlike HRVs, ERVs also transfer the latent energy of the moisture in the air. The ERV recaptures cooling and heating energy while controlling humidity extremes without mixing the two air streams. The key to this innovation is polymer membranes that are moisture-permeable, allowing humidity to be exchanged between the indoor and outdoor airstreams.

In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air through membrane exchange without allowing odors or pollutants in. In hot and humid climates, ERVs help to maintain (but do not reduce) the interior relative humidity (RH) in the process of cooling outside ventilation air. Reducing the RH in the summer decreases the mechanical cooling required, which makes this technology particularly suitable in hot and humid or very cold climates. A small handful of companies (e.g., Building Performance Inc. and dPoint) offer this technology using a microbe- and mold-resistant polymer (e.g., polypropylene) membrane that requires no moving parts (other than the HVAC fans external to the ERV).

Preconditioning the supply air can reduce energy consumption for heating and cooling. A study by the National Research Council of Canada showed that the ERV saved an additional 20% of dehumidifying energy and reduced cooling costs by 12%. The U.S. DOE Building Technologies Program states that enthalpy/energy recovery devices can save 65% of the energy consumed to condition outside air.

Baseline Example:

Baseline Description: Conventional HVAC without heat recovery
Baseline Energy Use: 10.5 kWh per year per square foot

Comments:

The 2009 Commercial Building Stock Assessment (CBSA) gives the actual electrical building Energy Use Index (EUI) for various types of heating and cooling systems (CBSA Table D-EA5). Office buildings with electric heating and cooling have an EUI of 20.1 kWh/sf/year. Office buildings with no electric heating or cooling use only 8.2 kWh/sf/year, indicating that the combined HVAC heating and cooling energy use is 11.9 kWh/sf/year. (For all commercial buildings, the corresponding values are 19.9 and 9.4 kWh/sf/year, respectively, for a heating and cooling use of 10.5 kWh/sf/year.)

Because this technology can be applied to many types of commercial buildings, a baseline heating and cooling energy use of 10.5 kWh/sf/year is assumed (NEEA, 2009).

Manufacturer's Energy Savings Claims: Currently no data available.
Best Estimate of Energy Savings:

"Typical" Savings: 65%
Low and High Energy Savings: 12% to 70%
Energy Savings Reliability: 3 - Limited Assessment

Comments:

Energy savings depend on climate type and the baseline system operation. The USDOE Federal Energy Management Program (FEMP) states that ERV systems have been shown to reduce HVAC energy consumption by up to 70% (FEMP Promising Technologies List). Other USDOE documents state that this technology can reduce outside air conditioning (heating and cooling) energy costs by 65% (Roth, et. al., 2002).

Energy Use of Emerging Technology:
3.7 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: 715,696,366
Comments:

This technology could be used for virtually any commercial building with electric space heat and without an existing economizer. The total square footage of the entire commercial building stock in the Northwest that has conditioned space that is electrically heated could be used for this application (84.7% x 27.1%, from Table C-GB13). The total commercial floor space that would benefit from a retrofit with this technology is, thus, estimated as the conditioned space or 2,640,946,000 sf x 27.1%  = 715,696,366 sf. This is the same as the square footage that is appropriate for retrofit with a heat recovery ventilator (ET #20 Heat Recovery Ventilator for Commercial Application).

 Total Commercial Floor space   % Conditioned   Conditioned space 
 Source, units   (NEEA, 2014) (sf)  (NEEA, 2009, App C )            (sf)
         3,118,000,000        84.7%       2,640,946,000     
Regional Technical Potential:
4.88 TWh per year
558 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
Emerging Technology Unit Cost (Equipment Only): $0.75
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.20
Baseline Technology Unit Cost (Equipment Only): $0.01

Comments:

Total installed costs,including overhead and profit, are estimated to range from $1.50 to $8.40/cfmfor heat wheel recovery units rated for 25,000 cfm down to 1,000 cfm (RS Means,2015 Facilities Construction Cost Data). Under peak conditions, one ton ofcooling requires about 170 cfm (Roth, et. al., 2002). One ton also serves about400 sf, so installed costs are approximately $2.25/cfm (for a 6,000 cfm ratedunit) x 170 cfm/ton x ton/400 sf = $0.95/sf.

Cost Effectiveness:

Simple payback, new construction (years): 1.2

Simple payback, retrofit (years): 1.5

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:

B.K. Ouazia, et. al., 2007. Assessment of the Enthalpy Performance of Houses Using the Energy Recovery Technology
National Research Council Canada, Institute for Research in Construction

GreenAngel, 2013. ERVs and HRVs: What's the Difference?
GreenAngel Energy

dPoint, 2013. A Revolution in CRF Core Technology
dPoint Technologies Inc.

Kurt Roth, et. al., 07/01/2002. Energy Consumption Characteristics of Commercial Building HVAC Systems Volume III: Energy Savings Potential
Prepared by TIAX LLC for the U.S. DOE Building Technologies Program

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

Energy Recovery Ventilator with Heat and Membrane Humidity Exchangers for Commercial Application

2015-1 Commercial HVAC TAG (#11)


Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
TAG Ranking: 21 out of 29
Average TAG Rating: 2.58 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:

  1. This is required by code in several applications, the PNW doesn't need the additional cost for humidity exchange and if the heat is gas, the savings will be gas.
  2. Would be interesting to hear about, although a longshot for our climate.
  3. For both residential and commercial applications, we need to get more analytical. With the relatively mild climates of the NW, do the fan power requirements eat up the energy savings, unless we pay for bypasses around the ERV? What buildings actually need enthalpy control, instead of just sensible heat, and in what climate zone?
  4. I am unsure about this technology in retrofits.
  5. Unless you have a high demand for dehumidification, this technology is seldom cost-effective.


2010 HVAC TAG (#3)


Technical Advisory Group: 2010 HVAC TAG (#3)
TAG Ranking:
Average TAG Rating:
TAG Ranking Date:
TAG Rating Commentary:

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