Finding Residential Energy Solutions through Energy Modeling

A Case Study of Fort Belknap IHS Staff Quarters, Ft. Belknap MT

Michael R. Young, P.E.Civil EngineerDivision of Engineering Services - Seattle Indian Health Service

Objectives

To illustrate methods to achieve energy efficiency in low-rise residential buildings.

To demonstrate most effective measures to save energy over the life cycle of the system.

To help save money to the occupants.

Overview

Federal Regulations Case Study: Fort Belknap, MT Results:

Energy Consumption Annual Utility Bills Life Cycle Cost Analysis

Recommendations: Design

Emerging Energy Regulations EPAct 2005 (Public Law 109-58)

Federal Leadership in High Performance and Sustainable Buildings MOU

EISA 2007

Executive Order 13423Strengthening Federal Environmental, Energy, and Transportation Management

10 CFR 433, 434, 435

Executive Order 13514

Federal Leadership in Environmental, Energy, and Economic Performance

Requirements of 10 CFR 435

Meet ICC International Energy Conservation Code, 2004 Supplement Edition, and

If Life-Cycle Cost-Effective, exceed the standard by 30% (Btu Consumption, not Cost) Space Heating Space Cooling Domestic Hot Water Heating

If not LCC-effective, achieve maximum level of energy efficiency that is LCC-effective

Limitations in 10 CFR 435/IECC

Neglects Lighting & Appliance Loads

Simulated Performance: Must use same fuel type in baseline as design Heating Oil: 140,000 Btu/gal Propane: 91,800 Btu/gal Different Efficiencies Available in NG,

Propane, & Heating Oil Furnaces

Evaluation of IHS Staff Quarters

Simulated the energy performance for a 3-bedroom staff quarters unit at Fort Belknap

Modified the design to meet the IECC Baseline (Standard Reference Design)

Compared design to Baseline

Simulated Design Alternatives to Seek 30% Improvement

Applicability throughout IHS

Ft. Belknap – Climate Zone 6B Similar IECC Requirements also in Regions 7 & 8 Long Heating Season Short Cooling Season Dry Climate (Cold, Sunny Winter Days)

Does not compare well with Marine Climates, the Southwest, Southeast, or East Coast

U.S. Climate Zones

Energy Costs

Recent Post-Occupancy Evaluation (Southwest) Findings: Primary concern of Occupants: Energy Cost In some cases, monthly heating bills reached

a significant percentage of the rental rate Questions regarding unit sizing, placement of

heating registers, design & construction quality How does energy savings translate to cost

savings?

Life Cycle Cost Analysis

Examines energy cost savings versus first costs.

25-year analysis, comparing all proposed design modifications.

Follows federal standards for LCCA OMB discount rates Calculates Savings-to-Investment Ratio Calculates Discounted Payback Period Evaluates Internal Rate of Return

Case Study

Fort Belknap, MT

8952 Heating Degree Days198 Cooling Degree Days

Case Study

1525 SF (Gross) 12,200 CF (Conditioned Space) Crawlspace Foundation (Conditioned), with

ICF Walls Uninsulated Floor 2 x 6 Frame Walls with R-19 Cavity Insulation Windows: Aluminum Frame, Double-Paned,

10% of Conditioned Floor Area; (U = 0.46, SHGC = 0.45)

Design of Ft. Belknap Unit (3 BR)

Doors: Steel, Urethane Core with Thermal Break (R = 4.4)

Ceiling: R-49 Blanket Insulation Heating: Natural Gas Furnace, AFUE = 0.92 Air Conditioning: Conventional, SEER = 13 Hot Water: 50-gallon tank, NG heated Ducting: In conditioned crawlspace, return

ducting in conditioned space, no insulation Infiltration: SLA = 0.00048 ft2/ft2

Design of Ft. Belknap Unit (3 BR)

Results—Energy ConsumptionUsing Conventional Furnace

Results—Energy ConsumptionUsing Ground Source Heat Pump

Comparison of Heating/Cooling Systems

0 20 40 60 80 100

Baseline Building

Design Building

Use Vinyl Windows

Use Tankless WaterHeater

Double-InsulateCrawlspace Walls

Increase SHGC inWindows

Re-orient Windows

Apply Exterior Shading

Annual Energy Consumption, MMBtu

Conventional Furnace Ground Source Heat Pump

Evaluation of Energy Costs

Prices Vary Significantly By Region

Fort Belknap Block Charges –

Electricity: $0.0955/kWh

Natural Gas: $10.1187/MMBtu ($101.187/Therm)

Summary of Energy Costs Using Conventional Furnace

Savings = $200-$400/yearNot Addressed by10 CFR 435 (~30%)

Lighting & Appliances

Not addressed by 10 CFR 435

Constitutes ~25% of the total energy cost

A 40% savings in L&A = 10% savings in total energy cost

Energy Star Appliances: ~$75/yr savings (based on a $2000/yr energy budget)

Summary of Energy Costs Using Ground Source Heat Pump

Savings = $400-$550/year

Furnace vs. Ground Source Heat Pump

0%

10%

20%

30%

40%

50%

60%

70%

80%

Energy Savings Cost Savings

Furnace Ground Source Heat Pump

Energy Savings vs. Life Cycle Cost Savings

Comparison of Energy andLife Cycle Cost Savings

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

1. 2. 3. 4. 5. 6. 7. 8.

Design Option

En

erg

y S

av

ing

s

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

LC

C S

av

ing

s

Energy Reduction LCC Savings

Life Cycle Cost Analysis – Conventional Furnace

First Costs3 Bedroom Unit: $275,000Vinyl Windows: $(1,600)Tankless Hot Water Heater: $1,700

Life Cycle Cost Analysis – Ground Source Heat Pump

Each has a point of diminishing returns Conventional Furnace System:

Difficult to exceed 30% over IECC

More pronounced for LCC Savings Vinyl Windows have a

significant LCC benefit Remaining Iterations: Energy

Savings essentially “offset” first costs

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

1. 2. 3. 4. 5. 6. 7. 8.

Design Option

Ene

rgy

Savi

ngs

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

LCC

Sav

ings

Energy Savings vs. LCC Savings

LCCA – Conventional vs. GSHP

Energy Savings does not translate equally to cost savings

GSHP Swaps Natural Gas ($10/MMBtu) for Electricity ($28/MMBtu)

Higher First Cost for a GSHP

Infiltration

Infiltration

Baseline Model: 39% of total Heating Load

Final Model: 55% of total Heating Load

Diminishing Returns

A Closer Look at Infiltration

IECC Baseline(SLA=0.00048)

0.5 ACH(Structural

Insulated Panels) Δ %

Heating 43.4 42.8 0.6 1.4%

Cooling 2.7 2.6 0.1 3.7%

DHW 16.2 16.2 0 0%

Total 62.3 61.6 0.7 1.1%

A Comparison of Conventional Infiltration versus SIP Infiltration

Recommended Prescriptive Design Requirements:

Parameter Value

Basement Type Conditioned Crawl Space or Basement

Foundation Walls Insulated Concrete Forms, R-44 or greater

Above-Grade Walls 2x6 wood frame with R-19 cavity insulation; Investigate Feasibility of SIPs

WindowsVinyl Frame with Double-Pane (U=0.30 or below)Solar Heat Gain Coefficient = 0.60 or above

Doors Steel-urethane core with break (R=4.4 or greater)

Ceiling R-49 Continuous

Heating Natural Gas Furnace, AFUE=92% or greater

Air Conditioning SEER=13 or greater

Hot Water HeatingRequire tankless or solar as an option (emerging federal standards require that a

minimum of 30% of hot water be heated with solar heat)

DuctingIn conditioned crawlspace, Return ducting in conditioned space, Insulation not

necessary.

Infiltration Tested in accordance with ASHRAE 119, Section 5.1.

What Can Users Do?

Thermostat Settings Every °F = ~$30 savings/yr

Turn off Lights Turn down heat or A/C while away Choose a smaller unit (if available) Solar Shading (summer) Solar Gains (winter)

Recap

Federal Regulations Energy Savings in IHS Staff Quarters Computer Modeling of “Typical” Unit Best Measures for Saving Energy Impact on Utility Bills Life Cycle Cost Implications Recommended Design Modifications Energy Saving Practices (Occupants)

Conclusion

Identify Greatest Energy Sinks Which Ones Can We Address? Regional Impacts Energy Studies will be posted on DES

website (www.des.ihs.gov)

Questions