Appendix L- HERS Report (NOT USED).pdf

HERS Study Report - Astoria Family Housing Phase IV March 11, 2013

HERS Study Report

ASTORIA FAMILY HOUSING PHASE IV / SECTOR HOUSING

SECTOR COLUMBIA RIVER

ASTORIA, OREGON

SFRL # 5067015

Energy Performance Analysis of Proposed Housing Designs March 8, 2013

Prepared by

Seattle, WA

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HERS Study Report DRAFT - Astoria Family Housing Phase IV March 11, 2013

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Executive Summary This study assesses the feasibility of a metric of energy performance proposed for the U.S.

Coast Guard Astoria Family Housing Phase IV homes.

The proposed metric uses the Home Energy Rating System (HERS Index) to measure a 30% improvement in energy performance over that of a home built to the minimum requirements of the International Energy Conservation Code of 2009.

The study uses REMRate energy simulation software to generate a HERS Index for a Baseline home built to the minimum requirements of IECC 2009, and for six proposed design homes featuring various space conditioning and hot water heating systems (plus two sub-options) installed in a three bedroom, mid-unit and a four bedroom end unit, both featuring the building envelope energy conservation measures described in the Task Order Statement of Services for Contract Number HSCG5-8-D-643F73.

The six options include:

Option 1: Electric Resistance Option 2: Electric Resistance plus Heat Pump Water Heater Option 3: Electric Ductless Heat Pump Option 4: Electric Heat Pump Forced Air Option 4n: Option 4 without Heat Recovery Ventilation (HRV) Option 5: Gas Forced Air Option 5n: Option 5 with No HRV Option 6: Gas Hydronic

Findings The study finds that, with the proposed building envelope efficiency, all these systems can achieve the 30% performance improvement.

Further, the study finds that similar HERS Indices for gas and electric-based systems result in significantly different energy consumption footprints and energy costs, and recommends additional metrics to assess final proposed designs.

Finally, the study makes recommendations for the proposed system based on three project priorities. The overall top recommendation, which delivers best performance across multiple metrics, is for a hybrid of options 3 and 4, featuring a ductless heat pump, heat pump water heater and supplemental, zoned electric resistance heat in sleeping spaces and bathrooms.

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Table of Contents Executive Summary ........................................................................................................................ ii Home Energy Rating System (HERS) Study

Overview Home Designs

The HERS Index Approach

Alternate Metrics Envelope Details Mechanical System Options

Findings – Discussion Overall Observations Fuel Choice Ventilation Observations

Recommendations Glossary of Terms Appendix

Tables Table 1: HERS Baselines and Targets Table 2: Envelope Specifications Table 3: Design Home Scenarios Table 4: Findings Summary

Figures Figure 1: Improvement in Energy Performance - 3 bds vs 4 bds

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Home Energy Rating System (HERS) Study

Overview The intent of this study is defined in the Task Order Statement of Services for Contract Number HSCG5-8-D-643F73. The overall goal of the project is to produce drawings and technical specifications for the Design Build Request For Proposal for family housing in the Coast Guards Vista Heights property in Astoria Oregon.

Included in Section 2.3 of that Statement of Services, title Building Design, are a list of energy efficiency measures intended to ensure a very high level of energy efficiency, thermal comfort and indoor air quality, as well as building durability.

Section 3.2 of that document requires that “a Certified HERS Rater shall evaluate a minimum of three alternative heating system types and recommend a single system type to be used throughout all housing units along with a measurable and achievable target HERS rating to incorporate into the RFP’s design-build requirements. The HERS rating must be at least thirty percent better than permitted by IECC 2009 {emphasis added}. Alternative system types shall have established records for efficiency, low maintenance, and low life-cycle costs. Energy sources for system types shall be limited to electricity and natural gas, only, with one of the alternative system types being electric resistance baseboard heating. Recommendations need not be limited to the use of conventional heating systems.”

This report is the summary of the findings of that analysis, and recommendations to the Project Team on preferred systems. The report does not select a single system, but rather clarifies the advantages and disadvantages of each of three systems. Final selection will depend on goals and priorities of the Coast Guard that are not clearly articulated in any of the project process to date.

Home Designs The home designs used for the study consist of the two units that make up the three- and Four-bedroom four-plex building described in the Final Project Proposal Report (PPR), 5 November 2012. Specifically:

• A three bedroom unit with approximately 1788 sqft of conditioned space1. This plan is used for the two mid-units in the four-plex, having very little exterior wall area and window area;

• A four bedroom unit with approximately 2090 sqft of conditioned space2. This plan comprises the two end units of the four-plex and so has considerably more exterior wall area and somewhat more window area for its relative volume.

1,2 Square footages may vary slightly based on calculation protocols relating to stair wells, useable spaces, etc.

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Floor plans and elevations are included in Appendix A.

The PPR and the Scope of Services document describe a list of building envelope measures that will provide a very thermally efficient building envelope. The proposed designs all feature the following:

• Building shall be heavily insulated – R- 38 insulation in the framed floor, R-21 plus R-10 continuous rigid insulation in the walls (with 2x6” 16” o.c. framing), R-49 in the attic with raised heels filled with high-density foam to ensure maximum insulation to the outside of the exterior walls;

• Thermally broken to the greatest extent practicable – the R-10 rigid insulation will provide a near complete thermal break in the exterior walls. Insulation and finish details at the window and door openings should be reviewed for ways to further reduce thermal bridging without compromising building durability and effective moisture management.

Foamed eaves and deep insulation in the attic minimizes thermal bridging in the roof assembly;

• Double pane, thermally broken window systems;

• Continuous air barrier will be provided by the sheathing, the building wrap and/or the rigid insulation;

• Air tightness of 2.0 air changes per hour at 50 pascals, tested by an independent Third-party;

• Heat recovery ventilation with minimum 75% efficiency

• Energy Star appliances

• Water Sense labeled plumbing fixtures

These features essentially describe the characteristics of the “design” units used for this study.

The only variables are the Space Conditioning Systems and Domestic Hot Water Heating systems.

The HERS Index The Scope of Services defines the HERS Rating as the primary metric for measuring performance of the proposed designs, with the minimum performance being set at a HERS Rating that is at least 30% better than permitted by IECC 2009. Some clarification of this target was requested from the Coast Guard, as follows:

1) The term HERS Rating no longer applies. The Home Energy Rating System (HERS) standard metric for home energy performance is now called the HERS Index;

2) The HERS Index is a measurement of a home’s estimated energy performance compared to the same home built to the minimum requirements of the 2006 International Energy Conservation Code (IECC) – known as the Reference Home. A HERS Index of 100 indicates that a home’s performance is equivalent to that of the Reference Home. An

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Index of less than 100 indicates that the home’s performance is more energy efficient than the Reference home;

3) The HERS Index cannot therefore, by definition, be generated to directly compare a proposed home against a home built to the minimum requirements of IECC 2009.

Proposed Solution

To address this, the following approach was proposed and accepted: We will create an IECC 2009 Baseline Home for the 3 bedroom and 4 bedroom units. These Baseline Homes will reflect the minimum requirements of IECC 2009 for both an electrically heated house and a gas heated house. The HERS Index for each of these homes will be recorded and used as the baseline for each unit and fuel type. Since the IECC 2009 includes improvements on energy conservation over the IECC 2006 Reference Home, the Baseline HERS Indices will be less than 100.

The Energy Performance target for the proposed designs will then be required to earn a HERS Index that is 30% below the IECC 2009 Baseline for each unit and fuel type. For Example:

If the IECC 2009 Baseline for the 3 bedroom unit, using gas heat, has HERS Index of 95, the target HERS Index for the proposed design will be 95 x 70% = 66.5.

The performance of the reference home used to generate a HERS Index, is based on a very complex set of standards, define by RESNet, the national body overseeing and administering the HERS system. It was intended to create a directly comparable metric of relative energy performance for any home of any age, size or type, located in any climate. It is a robust and popular system and serves its purpose quite well. However, it is not “fuel-neutral” (meaning it doesn’t measure energy efficiency in exactly the same way for electric, gas oil and other fuels).

Also, it is not necessarily a good predictor of actual energy performance for two primary reasons;

1. It uses a standardized set of assumptions about how a home will be occupied – hours of light usage, lengths of showers, etc. Actual lifestyles behaviors can vary significantly;

2. It uses fairly generalized algorithms for mechanical equipment performance that do not always reflect specific, installed equipment;

NOTE: Because the HERS Index is a national standard intended for all climates, the HERS Reference home always has mechanical air conditioning installed. If the Design home does not have air conditioning installed, the modeling protocol defaults to include mechanical air conditioning of the same efficiency as the Reference (SEER 13). Therefore, the HERS index will reflect savings resulting from installing air conditioning of greater efficiency than the Reference, but will not reflect savings from not installing air conditioning in the Design home. The importance of this, in the context of this study is discussed in the Approach, below.

Approach A software tool called REMRate was used for this analysis. It is the original software package approved by RESNet for generating HERS Indexes. In addition, it can also perform fairly sensitive analyses of building loads and overall energy consumption and cost.

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REMRate generates performance data by calculating thermal gains and losses to and from a building based on its geometry, orientation and building envelope details. It uses detailed weather data from weather stations nearby to the project site (in this case, right in Astoria, Oregon) to run an hour-by-hour analysis of thermal performance based on the exterior temperature and condition for every hour of every day of the averaged (TMY) weather year at that location. Non-weather related loads such as appliances, lighting etc. are also calculated based on occupancy and other factors.

The approach to this analysis was based on the solution defined above – creating Baseline Homes that met IECC 2009 minimum requirements and setting a minimum HERS Index target 30% below that of the Baseline HERS Index.

Describe:

• the Reference Home (IECC 2006 HERS Reference Home)

• Base Electric Home (IECC 2009 Baseline for Analysis)

• Base Gas Home (IECC 2009 Baseline for Analysis)

We chose to create both Electric and Gas Baselines, since HERS is not fuel neutral and treats gas and electric fuel differently. From those baselines, Target HERS indices (Baseline less 30%) were calculated – see the table below. Recall that the HERS Reference Home (built to IECC 2006 Code) has a HERS Index of 100.

Table 1: HERS Baselines and Targets

HERS INDICES

(Rounded)

Electricity Baseline

Electricity Target

Gas Baseline

Gas Target

Three Bedroom Mid Unit (1788 sqft)

95 67 94 66

Four Bedroom End Unit (2090 Sqft)

96 67 92 64

Alternate Metrics

Because of the limitations of the HERS Index as a consistent predictor of actual energy consumption, we also selected two other metrics to compare the performance of different systems, using the underlying energy consumption calculator engine of REMRate:

• Total Annual Energy Consumption – Millions of British Thermal Units (MMBtu) per year, covering both gas and electricity consumption;

• Annual Energy Cost – using the simulated consumption of each fuel type at the current residential tariffs for electricity and gas from the local utilities in Astoria, OR – Pacific Power and NW Natural Gas

NOTE: The HERS Index modeling protocol always includes mechanical air conditioning, as noted above. However, in a temperate marine climate like Astoria’s, cooling loads are small and the cost of installing air conditioning is rarely justified. For the purpose of this study, we

Prepared by O’Brien & Company 5 evaluated the impacts of including mechanical air conditioning in the Baseline and Design homes. Because of the small cooling loads, the impacts were small – generally causing a swing of less than 2% in the energy consumption and cost reductions. The swing was either positive or negative, depending on whether AC was already included or was added to the Baseline and/or the Design being compared.

For the total energy consumption and energy cost comparisons of this study, in order to best reflect real world conditions, mechanical AC is included ONLY where it is a standard feature of the selected space-conditioning system, i.e. where a heat pump is used for space conditioning.

This applies to the Electric Baseline and all electrically heated Designs, except the Electric Resistance and Electric Resistance with Heat Pump Water Heater (HPWH) Designs.

Envelope Details

The building envelope design is common to all the proposed designs. The following table describes the basic envelope components for the Reference Home (HERS 100), the IECC 2009 Baseline Homes, and the Design Home:

Table 2: Envelope Specifications

Slab FndWalls Framed floors AGWalls Ceiling Glazing ACH50

Reference

IECC 2006

IECC

2006 R-10 Per R-13Int R-30 R-19 R-38 U-0.35 7.00

BaseElectric

IECC 2009

2009 R-10 Per R-13Int R-30 R-20 R-38 U-0.35 7.00

BaseGas

IECC 2009

2009 R-10 Per R-13Int R-30 R-20 R-38 U-0.35 7.00

Design Home

R-10 Per NA R-38 R-10c R-21 R-49 U-0.28, 3.06

Note: For the purposes of this study, we used an envelope infiltration rate of 3.0 ACH50, rather than the 2.0 ACH50 as prescribed in the Scope of Services document. The reason for this is that, while we believe it is appropriate to require the more stringent level of air tightness in the construction documents, our analysis should reflect worst case scenarios, including the likelihood that envelope tightness will decrease somewhat over time.

See Base and Proposed Envelope Heating Loads in Appendix B.

See Glossary for details of the terms in the table and elsewhere in the report.

The Design Team Project Manager and Energy Analyst/HERS Rater met with the Coast Guard Facilities and Construction representatives to discuss the types of mechanical system, and the performance objectives of the project. Design Team Project Manager, Mechanical Engineer of Record and Energy Analyst/HERS Rater had follow up discussions to identify appropriate systems for consideration. Originally, this process narrowed the field down to four systems.

Some systems, such as ground-source heat pumps and central air-source heat pumps with variable refrigerant flow and hydronic radiant floor systems were considered, but dismissed due to site constraints, first cost limitations in relation to payback on performance, or other reasons.

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Mechanical System Options

The four systems preliminary systems were:

Option 1) Zonal Electric Resistance heat for space and domestic hot water (DHW):

a. A very common heat system in the Marine zone of the Pacific Northwest.

Electric resistance heaters – either base board convection heaters, electric fan coil heaters, or radiant cove heaters located in each room with local zonal temperature controls. Conventional 50 gallon electric hot water tank with extra insulation

b. First costs are low.

c. Maintenance and replacement costs are low, service lives vary but replacement is cheap and easy.

d. Operating costs typically considered to be high where heating loads are significant, because electric resistance heat has a coefficient of Performance (COP) of 1. That is to say: One unit of fuel energy consumed = one unit of heat energy delivered;

Option 2) Electric Air Source Heat Pump central ducted forced air heat/cooling, electric resistance tank DHW;

a. The upgraded approach to heating (and cooling) a home using electricity is an air-source heat-pump, which uses fuel energy to power a refrigeration cycle to move heat in and out of the building. In the right ambient conditions, air source heat pumps have COPs between 2 and 4 – using one unit of energy to deliver up to 4 units of heat energy into the house. However, conventional, single speed heat pumps become less efficient at lower ambient temperatures, when heating capacity is needed more. During times when the heat pump can’t meet the heating load, electric resistance supplementary heat (COP 1) is used to make up the difference. So, while conventional heat pumps work well in the shoulder seasons, in the winter at the times of greatest load, they may operate with an actual COP of around 1, the same as electric resistance (this option uses a conventional electric tank water heater as above);

b. The proposed system reflects current state-of-the-art residential split heat pump system efficiency, with an HSPF of 13 and a SEER of 20.5;

c. First Costs for conventional air source heat pumps are moderate to high;

d. Maintenance and replacement costs are higher than electric resistance, gas forced air or gas hydronic (see below);

e. Operating costs vary depending on equipment efficiency and ambient temperatures, but tend to fall below electric resistance but above the following gas systems. Also ducted distribution is bulky and vulnerable to duct system leak and conduction losses;

Option 3) Gas central ducted forced air heat, gas on-demand DHW

a. Probably the most common form of central heating in the Pacific Northwest. Gas forced air systems can be designed and installed to perform very efficiently, though the level of construction detailing typically employed does not deliver efficiency. Newer systems have efficient, condensing heat exchangers with multi-stage burners and variable frequency Air Handler Unit (AHU) fans. With well-sealed ducts run inside conditioned space, these systems take up a lot of space but

Prepared by O’Brien & Company 7 can be very efficient and cost effective. On-demand gas water heaters have also proven to be very popular, though they do suffer from some capacity limitations in family households where multiple showers and other hot water loads may occur simultaneously. A conventional gas hot water tank is a less efficient but sometimes more practical option;

b. The proposed system reflects a high-efficiency condensing furnace, AFUE 95.

c. Installed cost is moderate;

d. Maintenance and replacement costs are low to moderate;

e. Operating costs – if properly designed and constructed – should be low to moderate Option 4) Gas hydronic wall radiators and/or fan coils, integrated space and water heat from natural gas fired on-demand water heater, or condensing boiler;

a. Hydronic (water or fluid lines) heat distribution is compact and efficient (water holds heat much better than air, and is easier to push around a distribution system), and almost any heat source can be used to good effect. While slab floors heated with hot water have been a luxury favorite in the Northwest, they are no longer recommended in thermally-efficient low-load homes because there is not sufficient heat loss for the slab to really warm up and perform.

b. Current best practice suggests wall radiators or hydronic fan coil units are most effective and relatively inconspicuous.

c. New generation on-demand gas water heaters come with a small buffer tank built in and are very compact. Other on-demand systems, and most boilers, require a buffer storage tank with a heat exchanger to provide both space heat water and domestic hot water;

d. The proposed system reflect high-efficiency on-demand water heater performance for a heating application, with an AFUE of 90;

e. Installation costs are moderate to high, but compact heat source and ;

f. Maintenance and replacement cost are low to moderate (equipment typically has

25 year service life)

g. Operating costs tend to be comparable to or lower than gas forced air systems;

However, when the first runs were completed, the analysts felt there were gaps in the analysis and proposed two additional systems for consideration:

Option 1) Zonal Electric Resistance heat for space, Heat Pump Water Heater for DHW;

a. The new generation of Heat Pump Water Heaters (HPWH) is being heavily promoted and incentivized, particularly in the Pacific Northwest, where heat pump water heaters have not previously been viewed favorably. HPWHs draw air from living spaces, basements, garages or outside and move heat energy from that air into the water storage tank using a heat pump refrigerant cycle. New technology, compliant with the NEEA Northern Climate HPWH spec, is showing very positive results in lab tests and field studies. Tier 3 HPWHs can deliver satisfactory performance year around, even when installed outside, or when installed inside but with fully ducted for outside air as the heat source. Current products e.g. AO Smith Vortex, or AirGenerate are performing well;

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b. The proposed system reflects the current best-in-class Tier 3 HPWH, with a hybrid EF of 2.33 (hybrid describes the operating set-up where the heater will run in heat pump mode under all normal conditions, but will use an electric resistance back-up element under high loads. In heat pump-only mode the EF rises to 2.4;

c. Installation costs are fairly low to moderate, particularly where builder rebates might be available.

Option 2) Electric Mini-split Heat Pump, zonal electric for bedrooms, electric resistance tank DHW;

a. Another popular strategy in recent years, has been to use a new generation ductless mini-split heat pump to deliver heating and cooling to the main, open plan living space, while using electric resistance heat as supplemental heat in bedrooms and other enclosed spaces. Ductless heat pumps use a new variable frequency drive condenser unit, which allows them to maintain capacity and efficiency down to very low temperatures with resorting to supplemental electric heat, so they are able to deliver very high COPs (3 to 3.5) even on typical cold winter days. In this set-up, the ductless heat pump is allocated 80% of the heating load in the home;

b. Zonal electric resistance heat for other spaces (20% of heating load) and for domestic hot water is as described above;

c. Installation costs are moderate – again many utilities are offering incentives

d. Maintenance and replacement cost should be moderate. While this technology is newer in the US market, it has been common for decades in Europe, Asia and Australia and has proven track records

e. Operating costs will be lower than electric resistance and could match some of the gas systems

All scenarios use balanced, Heat Recovery Ventilation (HRV) with 75% sensible heat recovery efficiency, per the Scope of Services Section 2.3, unless otherwise noted. After the second set of energy model runs, we substituted a central integrated fresh air supply ventilation system with AirCycler, to replace the HRV in the ducted systems. See Ventilation Options, below.

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Table 3: Design Home Scenarios

Model ID

Ventilation CFM/hrs per day

Space Conditioning Equipment Efficiency Duct Leakage

DHW

Energy Factor

Lighting % CFL Appliances

Reference IECC 2006

8cfm25/100sqft BaseElectric IECC 2009 301/401 50/24 HP 7.7 HSPF/13 seer 8cfm25/100sqft EF 0.88 0% Regular

BaseGas IECC 2009 302/402 50/24 80 AFUE 8cfm25/100sqft EF 0.56 0% Regular 1-Electric Resist 303/403 50/24 HRV ElecRes

EF0.93 80% EnergyStar

2-Electric Resist HPWH 304/404 50/24 HRV ElecRes

EF 2.33 80% EnergyStar 3-Electric Ductless 305/405 50/24 HRV DHP 11.6/20.6

EF 0.93 80% EnergyStar

4-Electric HPDucted 306/406 50/24 HRV ASHP13/20.5 6cfm50/100sqft EF 0.93 80% EnergyStar 4n-Electric HPDuctedNoHRV 306n/406n 50/24 ASHP13/20.5 6cfm50/100sqft EF 0.93 80% EnergyStar 5-GasDucted 307/407 50/24 HRV 95 AFUE 6cfm50/100sqft EF 0.85 80% EnergyStar 5n-GasDuctedNoHRV 307n/407n 50/24 95 AFUE 6cfm50/100sqft EF 0.85 80% EnergyStar 6-Gas Hydronic 308/408 50/24 HRV 90AFUE

EF 0.91 80% EnergyStar

Key Option 1:Electric Resist - Zonal electric resistance heat, electric tank water heater Option 2: Electric Resist HPHW – Zonal electric resistance heat, Heat Pump Water Heater Option 3: Electric Ductless – Ductless Mini-split heat pump, electric resistance supplemental, electric tank water heater Option 4: ElectricHPDucted – Air source heat pump, central ducted forced air heating/cooling, electric tank water heater Option 4n: ElectricHPDuctedNoHRV – Same as 4, but with integrated fresh air ventilation instead of balanced, Heat Recovery Ventilation Option 5: GasDucted – Condensing gas furnace, central ducted forced air heating, gas on-demand water heater Option 5n: Gas DuctedNoHRV – Same as 5, but with integrated fresh air ventilation instead of balanced, Heat Recovery Ventilation Option 6: Gas Hydronic – Condensing gas water heater or boiler, hydronic radiators or fan coils, heat exchanger and buffer tank for DHW

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Table 4: Findings Summary

3 bd mid-unit

4 bed end-unit

HERS

HERS

Reduction

Annual Energy Consumption MMBtu

Consumption Improvement over Baseline

EUI

(kBtu/sq ft/yr) Energy Cost

Cost Reduction

Reference IECC 2006 IECC 2006 100 0.00 BaseElectric IECC 2009 301 IECC 2009 95 0% 50.6 0% 28.30 1,536.00$ 0% BaseGas IECC 2009 302 IECC 2009 94 0% 74 0% 41.39 1,340.00$ 0% Electric Resist 303 66 31% 42.4 16% 23.71 1,283.00$ 16% Electric Resist HPWH 304 55 42% 34.9 31% 19.52 1,062.00$ 31% Electric Ductless 305 64 33% 36.7 27% 20.53 1,108.00$ 28% Electric HPDucted 306 67 29% 37.6 26% 21.03 1,130.00$ 26% Electric HPDuctedNoHRV 306n 66 31% 36.9 27% 20.64 1,112.00$ 28% GasDucted 307 56 40% 45.2 39% 25.28 982.00$ 27% GasDuctedNoHRV 307n 55 41% 45.6 38% 25.50 970.00$ 28% Gas Hydronic 308 53 44% 43.8 41% 24.50 963.00$ 28%

HERS

HERS

Reduction

Annual Energy Consumption MMBtu

Consumption Improvement over Baseline

EUI

(kBtu/sq ft/yr) Energy Cost

Cost Reduction

Reference IECC 2006 IECC 2006 0.00 BaseElectric IECC 2009 401 IECC 2009 96 0% 79.4 0% 37.99 2,478.00$ 0% BaseGas IECC 2009 402 IECC 2009 92 0% 93 0% 44.50 1,564.00$ 0% Electric Resist 403 66 31% 51 36% 24.40 1,557.00$ 37% Electric Resist HPWH 404 56 42% 42.8 46% 20.48 1,304.00$ 47% Electric Ductless 405 60 38% 43.6 45% 20.86 1,310.00$ 47% Electric HPDucted 406 64 33% 43.3 45% 20.72 1,300.00$ 48% Electric HPDuctedNoHRV 406n 64 33% 42.7 46% 20.43 1,281.00$ 48% GasDucted 407 52 43% 52.9 43% 25.31 1,097.00$ 56% GasDuctedNoHRV 407n 51 45% 53.4 43% 25.55 1,085.00$ 56% Gas Hydronic 408 51 45% 53.4 43% 25.55 1,095.00$ 56%

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Findings – Discussion Figure 1: Improvement in Energy Performance - 3 bds vs 4 bds

30%

30%

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Overall Observations All but one of the proposed Design systems met the 30% improvement in HERS Index target.

The only exception was the central Electric Heat Pump Forced air system in the three bedroom unit. Even this scenario could meet the 30% minimum improvement by replacing the HRV with a central integrated fresh air supply ventilation system. See Ventilation Options, below.

Side by side comparison of the results from the two sets of unit models reveals clear differences.

In the three bedroom unit, with little exterior wall and consequently very small heating loads, cost savings from different mechanical systems are relatively small, in spite of large improvements in efficiency, because the heat load is a small component of the total energy cost.

The exception to this is in Option 2: Electric Resist HPWH, where the addition of the HPWH substantially improves on the modest energy and cost savings in Option 1: Electric Resist, because it is the only measure that addresses a major load other than space conditioning.

In the four bedroom unit, with the greater exterior surface and larger heating loads, cost reductions are more significant across the board because heating is a larger share of the total load and so these measures have a more substantive impact on the total energy cost. Once again, however, Option 2 is a top performer.

Fuel Choice Gas is cheaper - Clearly, in either unit there is a performance distinction between gas and electricity, resulting from the fundamental efficiency of burning gas in a 90%+ efficient appliance at the point of use. Coupled with the low current and near-term projected cost of natural gas, these results may indicate that gas is the wise choice of fuel.

With one exception, (Option 2) none of the electric solutions can match the cost saving improvements of the gas-fired systems.

Electric Heat Pumps are more efficient - However, analysis of the total annual energy consumption reveals a different story: In absolute terms, the gas systems use approximately 30% more fuel energy than the electric heat pump systems, at the point of use. The lower overall energy cost of the gas systems is the result of the current low cost of natural gas and the higher cost of delivery of electricity from the original fuel source.

Energy Consumption vs Greenhouse Gas Emissions - If the Coast Guard is interested in current tracking and future reduction and elimination of greenhouse gases, installing gas infrastructure and building housing that is dependent on natural gas will limit greenhouse gas reduction opportunities in the future, whereas electric based systems offer easy options for green power purchases or on-site renewable generation (PV, Wind, Hydrogen Fuel Cell, etc.).

If this strategic issue is important, Option 2 offers attractive performance with relatively low installation and maintenance costs. For slightly higher first and maintenance costs, adding the HPHW to Option 3: Electric Ductless would yield even greater energy efficiency than any of the proposed gas options. This option is addressed in the Recommendations, below.

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Ventilation Observations

• Efficacy of Heat Recovery Ventilation: Use of heat recovery ventilation in this climate does not yield an appreciable energy performance benefit. Small reductions in space conditioning load are offset by increased fan power for ventilation;

• HRV should have its own dedicated small diameter duct system to ensure effective ventilation delivery to all living spaces. Use of the space conditioning duct work is not effective because it is designed for much higher flow rates than the ventilation only flow when the main air handler is not running. If the system requires operation of the AHU even when heating or cooling is not required, higher electric fan loads will result.

• A central integrated outside air system, which ducts fresh air into the return side of the AHU, controlled by a mechanical damper and air-cycler control is less costly to install and maintain. If the AHU has a VFD fan motor, the air cycler will run the AHU at low speed to meet ventilation requirements when no heating or cooling is required. Fan energy loads will be little different that with HRV installed and operating continuously.

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Recommendations Based on the findings of the HERS Study, the recommended system depends on the priorities of the Coast Guard in making the selection. The authors suggest three possible options:

Minimum Cost for Compliance:

Option 1: Electric Resistance. Because of the thermal efficiency of the design building envelope, electric resistance heating is a viable consideration. The very low installation cost of electric baseboard, fan coil or cove radiant heating, reasonably long service life and low replacement cost go some way to offset the relatively high energy footprint and modest energy cost reductions of this option:

3 bdrm Mid 4 bdrm End Average

HERS Index 66 66 66

Annual Energy Consumption (MMBtu/yr)

43.4 51 47.2

Annual Energy Cost ($/yr) $1,283.00 $1,557.00 $1,420.00

Baseboard and fancoil systems have some indoor environmental quality concerns, notably burned dust odors and noise, respectively. Cove radiant heating and some of the higher quality convection heater systems generally improve thermal comfort at a modest additional cost.

Low Energy Costs and Flexibility Option 6: Gas-fired Hydronic heating. Based on the preliminary analysis, the gas-fired hydronic heating system represents the lowest fuel costs based on available current utility pricing. The study favors hydronic over forced air distribution on the basis that, while installed cost may be slightly higher than a gas forced air system, the improved efficiency of hydronic distribution and lower maintenance costs compared to the ducted forced air system suggest lower long-term ownership costs. In addition, hydronic distribution offers easier fuel switching options when it comes time to replace the heat source, should gas become less attractive than other fuels in the future.

3 bdrm Mid 4 bdrm End Average

HERS Index 53 51 52

Annual Energy Consumption (MMBtu/yr)

43.8 53.4 48.6

($/yr) $963.00 $1,095.00 $1,029.00

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Best overall Performance Option 3: Ductless Heat Pump PLUS Heat Pump Water Heater. The most significant incremental improvements in performance came from the addition of the ductless heat pump or the heat pump water heater to the electric resistance option. For the final analysis we included both these systems, to create a highly efficient electrically-fueled option, featuring:

• a high efficiency ductless heat pump to provide heating and cooling in the main living space and partial heat for the bedrooms,

• supplemental electric resistance in the bedrooms and bathrooms

• a Northern Climate spec Tier 3 heat pump water heater for the domestic hot water heating This all-electric solution provides the lowest HERS Index, lowest overall energy footprint and lowest energy cost. It also brings energy consumption to a level with potential to achieve near-net zero energy performance with future installation of on-site renewable energy generation, or very low cost green power premiums.

With an average $430 annual savings over Option 1, and a marginal cost of approximately $6,000, we estimate a 14 year simple payback for this option.

3 bdrm Mid 4 bdrm End Average

HERS Index 51 49 50

Annual Energy Consumption (MMBtu/yr)

29.9 35 32.45

($/yr) $921.00 $1,060.00 $990.50

Additional notes about this recommendation:

A) An all-electric house has no back-up heat source in the event of a power outage. The efficient thermal envelope of the proposed design will maintain thermal comfort for prolonged periods in all but the most extreme conditions, if properly managed. However, if power supply is unreliable, back-up generators could be a consideration. (Note:

Without electricity to run circulation pumps, the gas hydronic system is also vulnerable, but back-up electric generator load to run hydronic pumps would be much smaller than to run heat pumps).

B) The ductless heat pump has a small, relatively quiet outdoor condenser unit, which would likely have to be located adjacent to the back of each unit. It might be possible to locate these condensers at either end of each building, running longer refrigerant lines to the two mid-units;

C) The heat pump water heater should, most likely, be installed in the bottom floor mechanical room. Outside supply air will be ducted to the heat pump and exhaust air ducted to the outside. If these ducts vent to the outside adjacent to the current mechanical room vent shown on the drawings, the high air-flow from in these ducts during operation (up to 400 cfm) could impact the rear deck/patio area from an amenity perspective.

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Consumption Feedback Systems It is important to note that the results of this study are based on a set of standardized assumptions about occupancy and occupant behavior. Building design and equipment efficiency do contribute significantly towards energy conservation. Occupant Behavior, however, is the ultimate determinant of actual energy consumption. A program of investment in energy efficiency to the extent of these recommendations would be incomplete if the plan did not include consumption feedback and monitoring of energy (and water) performance. Real time feedback on energy consumption, through some form of on-line or in-home “dashboard” is an effective tool with which to educate occupants about their energy consuming behaviors. The system will also provide facilities maintenance staff with insight into equipment performance (which components are performing to expectations and which are not) and advanced warning of maintenance requirements.

In-home dashboards of this type can be installed for $400 to $1000.00, and direct savings are hard to measure, though studies suggest that education of and engagement with home occupants about energy conservation issues can result in significant savings over time.

Multiple Metrics The results of this study suggest that using HERS Index alone as the metric of achieved energy performance in this project will provide an incomplete picture of whether the contractor has met the performance requirement.

We recommend that the design assessment includes REMRate modeling of the proposed design, by a certified HERS rater. Targets should be set for all three metrics in this study, based on the Coast Guard’s larger energy performance goals and other project priorities.

Furthermore, the Contract Specification document should include clear performance specification requirements for the elements that contribute to the energy performance of the project (including envelope infiltration, equipment efficiency, HRV fan efficacy and thermal recovery efficiency, and others) and completion of the contract should be made dependent on meeting all specification requirements in construction, also assessed by a certified HERS Rater.

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Glossary of Terms ACH --------- Air Changes per Hour ACH50 ------ Air Changes per Hour at a pressure differential of 50 pascals AFUE ------- Annual Fuel Utilization Efficiency; a measure of heating equipment performance AGWalls ---- Above Grade Walls AHU -------- Air Handler Unit ASHP -------- Air source Heat Pump CFM --------- Cubic Feet per Minute COP --------- Coefficient of Performance; the ratio of fuel energy consumed and heat energy delivered DHP --------- Ductless Heat Pump DHW ------- Domestic Hot Water ECM --------- Electronically commutated motor – an electric motor design that allows for variable speed operation and improved energy efficiency EF ----------- Energy Factor ERV --------- Energy Recovery Ventilation; a system that can recover both sensible and latent energy from whole house ventilation exhaust flow (see also HRV) FndWalls ---- Foundation Walls HERS -------- Home Energy Rating System HPWH ------ Heat Pump Water Heater HRV -------- Heat Recover Ventilation; a system that can recover the sensible heat energy from a whole house ventilation exhaust flow (see also ERV) HSPF -------- Heating Season Performance Factor; a measure of the heating season efficiency of an air-source heat pump MMBtu ------ Millions of British Thermal Units; a normalized measure of energy – the energy required to raise the temperature of one pound of water by one degree farenheit.

SEER -------- Seasonal Energy Efficiency Ratio; a measure of cooling equipment efficiency VFD --------- Variable Frequency Drive – an electric motor control system that controls motor speed and torque by varying input current frequency and voltage;