Humidification Retrofits Deliver Residential Furnace Efficiency

HUMIDIFICATION RETROFITS DELIVER

RESIDENTIAL FURNACE EFFICIENCY

Retrofitting 80% Residential Furnaces for High Efficiency

Josh Quinnell, Ph.D.

Thursday, December 14, 2017

Conservation Applied Research and Development (CARD) Grant # 85907

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Outline

• Introduction• Background

• Research Objectives

• Methodology• Characterization & site selection

• Measurements & data acquisition

• Analysis

• Results• Performance

• Humidity

• IAQ

• Cost Effectiveness

• Conclusions & Recommendations

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Outline

• Introduction

• Methodology

• Results


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Forced Air Heating: 80% or 90%+

High efficiency condensing furnace (90%+)Standard efficiency furnace (80%)

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Energy Savings in Residential Heating

• The single biggest energy savings opportunity in MN

• 1/3 natural gas used in the residential sector

• 2/3 of that natural gas is used for space heating

• ~20% of MN natural gas used by forced-air furnaces

• Energy savings require an upgrade from standard

efficiency (80%) to condensing furnace (90+%)

• A few problems with furnace upgrades:

• Standard efficiency still commands 30%+ of the market

• Long-lived (20 – 30 years) appliances that achieve nameplate

performance until failure

• Either wait for failure or replace a working appliance

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The Case for a Retrofit Alternative

• Standard efficiency furnaces will be here a long time

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Transport Membrane Humidifier (TMH)

• Gas Technology Institute (GTI) developed whole-house humidifier

• A second heat exchanger retrofitted to a standard efficiency furnace

• Ceramic tubes transport liquid water and heat from the flue gas to the

return air

• The nano-engineered ceramic membrane tubes transfer water and

block transport of other combustion products

• Devices promises to humidify and increase furnace efficiency

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Humidification

• Cold air cannot hold moisture which causes homes to

dry out in the winter

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Humidification

• Extreme dryness has negative consequences

• General discomfort (lower apparent temperature)

• Respiratory and skin irritation

• Static discharge

• Cracking & creaking of contracted wood

• Humidification has its own challenges

• Humidification requires a significant amount of energy for

evaporation (e.g. up to 20% of the heating load)

• Humidifiers (and excess humidity) are associated with many

problems including mineral deposition, microbial growth, and

health issues

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Objectives

• Validate the performance of TMH units and assess its

potential as an alternative path to high efficiency space

heating

• Measure the humidification benefits of TMH

technology and its performance as a whole-house

humidifier

• Monitor indoor environments to understand the

humidification benefit and adverse consequences of

excessive humidification

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Outline

• Introduction

• Methodology

• Results


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Methodology

• Identify site selection variables influencing TMH

outcomes

• Design & install prototype TMH units in research sites

• Measure TMH field performance and perform long-

term monitoring of units and indoor air conditions

• Analyze performance, humidification benefits, and

energy savings

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Site Selection

• Furnace type/make/model/age

SiteFurnace

MakeModel

Age(yr)

Size(BTU/hr)

AFUE(%)

Airflow(cfm)

h2 Bryant 383KAV 16 88,000 80.6 915

h3 Rudd UGPH07EAVER 19 75,000 80.6 960

h4 ArcoAire GUA080A012AIN 27 80,000 80 870

h5 Goodman GMPV075-1.5/3 21 75,000 80 821

• Emphasis on indoor humidity conditions

• Occupant Density: humidity generation

• Envelope Leakage: rate of humidity removal

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Envelope Leakage vs. Occupant Density

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Instrumentation

1

2

3

4

5

6

7

8

9

#

#

#

Furnace Runtime

Attic Space Temperature, Humidity, and Wood Moisture

Basement Space Temperature, Humidity, and Wood

Moisture

Common Space Temperature, Humidity, and Wood

Moisture

Ongoing Household Measurements

Characterization Measurements

Ongoing Furnace Measurements

Supply and Return Duct Pressures

House Envelope Tightness

Furnace Airflow

Supply Air Temperature

TMH Flue Gas Temperature (Out)

TMH Flue Gas Temperature (In)

TMH Temperature and Humidity

Return Air Temperature and Humidity

• Instrument furnace, TMH, and

dwelling

• Measure sensible energy added

by furnace & TMH

• Measure latent energy added by

TMH

• Measure temperature, humidity,

and moisture storage in home

• Analyze:

• Output rates (Btu/hr)

• Steady-state efficiency (%)

• Changes in indoor environment

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Code Compliance & Permitting

• Discomfort by building official over unlisted devices

• Permitting negotiations resulted in one year delay for

three installations

• Ultimately issued temporary installation permits in two

municipalities

• Documented performance & safety lab testing for each unit

• Installation instructions and operating manual for each site

• A P.E. report certifying the design & safety of the TMH

• Underwriters Laboratories field certification for one unit

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Installation

• Emphasis on documenting installation

• Retrofits will require fast and cheap installs

• Develop installation documentation

• Observe & document all installs

• Recruited a contractor and used a single crew

• Understand labor costs of installation

• Determine any barriers to installation

• Describe learning curve associated with installation

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Installation – Step 1

• Remove return drop and

existing vent & size new

return duct

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• Install TMH and

resized return drop

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• Reconfigure vent

• Dual vents enable alternate

mode testing

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• Add sealed PVC vent

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• Tie in safety switch

and inducer fan

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Outline

• Introduction

• Methodology

• Results


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Field Data

TMH BypassSite

DaysFurnace Cycles

DaysFurnace Cycles

h2 7 40 126 1594

h3 139 1550 68 604

h4 194 2474 173 1248

h5 118 1174 65 856

• Monitored for 1 – 2 heating seasons per site

• Alternate mode testing (TMH and bypass modes) in all seasons

• Reached design conditions

• Collected data during thousands of furnace cycles during both TMH

and bypass mode

• Net Result:

• Large quantity of data over

a large range in operating

conditions for four different

furnaces

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Steady-State Net Performance Increase

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Steady State System Energy Output

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Performance Summary

• Space Heating

• 9% natural gas savings for space heating (5,300 Btu/hr)

• 5 – 7°F temperature increase across the TMH

• Humidification

• 9% natural gas savings if displacing other humidification

systems (5,200 Btu/hr)

• May not displace all energy for humidification if other

humidification systems remain operational

• If TMH does not displace previous humidification there are no

savings, but it remains a significant non-energy benefit.

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Humidifier Performance

• Median humidity

outputs of 10 – 21

pints/day

• Maximum humidity

outputs of 23 – 55

pints/day

• Typical outputs range

between 8 – 28

pints/day

Hu

mid

ifie

r O

utp

ut

(pin

ts/d

ay)

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Dynamic Humidifier Output

• More humidity in

cold weather

• No humidistat

control

• Humidity output

proportional to

runtime and

humidity difference

• Self-limiting nature

decreases over

humidification

concern

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Indoor Environment Site h3 (32% RH)

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Indoor Environment Site h4 (50% RH)

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Effect on Indoor Conditions

• TMH improves indoor humidity by 10% during cold weather (<32 ᵒF) and dry conditions (<30% RH)

• Over humidification avoided in mild to warm weather (>32 ᵒF)

• Outdoor humidity is a more important factor for determining

indoor humidity than humidifier output

• Overall output is reduced in home with baseline

relative humidity (40 – 50% RH)

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Energy & Cost Savings

Heating Only Heating and Humidification

Site therms Low Medium High therms Low Medium High

h2 158 $79 $126 $189 207 $103 $166 $248

h3 121 $61 $97 $145 285 $142 $228 $342

h4 71 $36 $57 $86 207 $104 $166 $249

h5 94 $47 $75 $113 167 $83 $134 $200

• Furnace performance increase readily applied to

weather-normalized loads

• Savings sensitive to heating load and gas prices

• Savings double with humidification

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Total Installed Costs $1,400 - $1,900

Low High

Production Cost $402 $625

Retail Price $603 $938

Misc. Materials $306 $306

Install Labor $459 $660

Total Installed

Cost$1,368 $1,904

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Payback Scenarios at $1,400

Heating onlyHeating and

Humidification

Potential rebates:

Space heating conservation

Humidification conservation

Humidifier displacement

$200 $400

Site Low High Low High Low High Low High

Scenario 1 17.3 7.2 13.2 5.5 11.3 4.7 9.4 3.9

Scenario 2 22.6 9.4 9.6 4.0 8.2 3.4 6.8 2.8

Scenario 3 38.3 16.0 13.2 5.5 11.3 4.7 9.3 3.9

Scenario 4 29.1 12.1 16.4 6.8 14.0 5.8 11.6 4.8

• Nominal lifetime: 12 – 15 years (underlying furnace)

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Outline

• Introduction

• Methodology

• Results


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Conclusions

• TMH adds 10,500 Btu/hr to standard efficiency furnaces

• Offers direct natural gas savings of 9% for space heating and 9%

for humidification

• Performs similarly to a whole house humidifier without the

headaches of those systems

• It operates passively; output is proportional to need

• Improves indoor humidity by 10% in the cold weather

• Less output in mild weather & higher humidity home

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Conclusions

• Cost effective over its lifetime

• The only alternative to a condensing furnace upgrade

• Likely the only way to achieve savings before we

(slowly) phase out the hundreds of thousands of I.D.

furnaces over the next 20 to 50 years

BUT

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CIP Recommendations

• GTI has yet to entice a manufacturer to take up the concept• Potentially cannibalize condensing furnace sales

• Cite risks associated with creating a new product without an established market

• What can we do? What can CIP do?• Direct rebate offerings for space heating and efficient humidification

savings

• Develop a retrofit program to kick-start a market. Secure a sufficient number of participants to justify TMH production

• Pursue public/private partnership to lower risks of commercialization (e.g Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs)

around securing a certain number of participants through a preprocess guaranteeing a sufficient quantity of TMH sales to a potential manufacturer, thus reducing the initial risk of commercialization.Lastly, the pursuit of a public/private partnership may sufficiently alleviate the risk of commercialization. The results of this study as well as prior work by GTI, may be sufficient to develop a partnership with a manufacturer to obtain public funding that facilitate commercialization. For example via the Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs.

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Leakage

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Wood Moisture (Moisture storage)

Humidification Retrofits Deliver Residential Furnace Efficiency

Environment

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