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energy star® performance guidelines overview - Rappahannock ...




ENERGY STAR Qualified Homes

Page No.

Certification Process 4

National Performance Path Requirements and Notes 5

Builder Option Package (BOP) and Notes 7

Thermal Bypass Inspection Checklist 10

Thermal Bypass Guide 12

ENERGY STAR Performance Requirements 21

ENERGY STAR Manual—J Load Calculation Requirements 23


ENERGY STAR homes use a number of innovative technologies, such as climate-appropriate insulation, high-performance

windows, airtight envelope and ducts, efficient heating and cooling equipment, plus on-site inspections and testing to verify



To qualify as ENERGY STAR, a home must meet the minimum requirements specified below, be verified and field tested in

accordance with the RESNET (Residential Energy Services Network) standards by a RESNET accredited provider, and meet

all applicable state building codes.

I. Homeowners/builders may choose one of two ways to qualify their home as an ENERGY STAR

energy-efficient home.

• A traditional Home Energy Rating—A Home Energy Rater simulates the home’s energy

use; this analysis allows the rater to identify the most effective upgrades to meet Energy

Star performance guidelines.

• The Builder Option package—The builder and rater use a set of climate-specific

construction specifications that result in homes consistently meeting ENERGY STAR


II. The Thermal Bypass Inspection Checklist must be completed for homes to earn the ENERGY STAR

label. The checklist requires visual inspection of framing areas where air barriers are commonly

missed and inspection of insulation to ensure proper alignment with air barriers (air and thermal

barriers must be continuous and complete).

III. Completion of Field Verification. In addition to the Thermal Bypass Inspection Checklist, the

Home Energy Rater must conduct on-site pressure testing of the home. The rater will check for

proper equipment size, air sealing, insulation and air distribution and will pressure test the duct system

if not located within conditioned space. The final inspection will be after the HVAC system

start-up, with permanent electrical power, and with the home totally enclosed. The rater will perform a

blower door test to verify the home’s airtightness.

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I.0 THERMAL BYPASS GsUIDE general tips and best practices

1.1 Overall air barrier and thermal alignment

Fiberglass batts shall be face-stapled to the studs. Fibrous batt insulation should not be cut short or cut long and forced/compressed into small areas.

To minimize compression, fibrous batts shall be cut around electrical boxes and split around plumbing and wiring. Wet spray cellulose shall be

cropped smoothly to prevent convective channels and void cavities between the insulation and sheetrock.

1.2 Gap between garage and conditioned space due to incomplete blocking

Creating air barriers to close gaps between the garage and the conditioned space can become increasingly difficult to construct as the joists become

more irregular at their cross section. This is particularly true for I-joists and web-trusses. A simple solution is to plan ahead and align the end of joists

with the wall adjoining the conditioned space to allow for end blocking.

Filler blocking much

Filler simpler blocking shape with much

simpler dimensional shape lumber. with

dimensional lumber

Filler blocking much

Filler harder blocking shape with much

harder Engineered shape lumber. with

Engineered lumber

1.3 Attic eave baffles

Wind intrusion can occur at roof eaves through soffit vents. If the attic insulation is left exposed, the wind blowing through the soffit can flow

through the insulation and in some cases blow it away from the edge. As a result, wind intrusion can undermine the effectiveness of the insulation

and create opportunities for moisture problems.



Energy Truss

“Soffit dam” use batt

or rigid foam board

Rafter baffle



Raised Top Plate

Additional top plate

Rafter baffle


Soffit vent

Soffit vent

1.4 Slab edge insulation

There are two basic ways to insulate a slab. First, rigid insulation can be installed directly against the exterior of the slab, as shown in the detail at

left. Note that in areas with high termite populations, builders should be careful to avoid installing foam insulation in contact with the ground.

A second option is a “floating slab,” which can be constructed using interior insulation, as shown in the detail at right. In both cases, insulation

should be continuously aligned with the air barrier.

R i g i d i n s u l a t i o n

e n c a p s u l a t e d o r

c o v e r e d w i t h

m e m b r a n e t o

p r o t e c t f r o m

t e r m i t e s a n d

e x t e r i o r

d a m a g e .

Metal termite


Sill gasket

1.5 Critical rim / band joist closure areas

Perforated drainage pipe is embedded in gravel,

covered with filter fabric, and located at lower

perimeter of foundation footing to provide drainage.



10-mil poly vapor

diffusion retarder is

extented under


Metal termite


Sill gasket

Rigid insulation

Perforated drainage pipe is embedded in gravel,

covered with filter fabric, and located at lower perimeter

of foundation footing to provide drainage.

10-mil poly

vapor diffusion


Fiberglass insulation alone is not enough to stop air from leaking through the rim / band joist. Foam or foam board fixed tightly and sealed at the

edges will stop air leakage.



Caulk bottom plate

to subfloor

Caulk band joist

to subfloor and plates

and insulate

Caulk bottom plate

to subfloor

Sill gasket or

double-bead of caulk

12 13|

1.6 Minimize thermal bridging

The intersecting corner of two insulated walls shall be framed such that insulation is continuous in the external wall (corners with unnecessary 2x4’s

are not permitted). A“California corner” or two-stud corner with drywall clips are methods of achieving this.

Advanced corner

Advanced corner

Advanced aldder T-wall framing

Advanced ladder T-wall framing

Drywall and interior

walls are attached to

Drywall clip to hold

"ladder," which spans

drywall in place between studs.

2.0 Walls Adjoining Exterior Walls or Unconditioned Spaces

2.1 Wall behind shower / tub 2.2 Wall behind fireplace

Insulate and air seal

behind tub with sealed polyethylene

plastic or sheet material.

All exterior walls of fireplaces shall be sealed with

proper sealant and , where permissible, a proper

sealant shall be used at the junction between

sheathing and flue pipe and comply with the fire

code and the manufacturer’s specification.






Seal tub penetration.

2.3 Insulated attic slopes / walls 2.4 Attic knee walls - ≥ 19 R-value






Knee wall



Rigid board insulation seals

and adds R-value ;

extend to bottom of joists, ;

caulk and tape to form air seal.

Knee wall




Attic space






box to


Seal all edges of rigid

foam insulation .



box to


Loose-fill or

batt insulation




Unwanted air leakage

Attic ventilation

Soffit vent

2.5 Skylight shaft walls - ≥ 19 R-value

Skylight shafts protruding through the ceiling and an unconditioned space need to be insulated since the shaft’s walls are effectively attic knee walls

adjoining an unconditioned space. Skylight shaft walls shall be insulated to the same level as attic knee walls and shall include a sealed air-barrier

aligned with the insulation on both interior and exterior sides of the walls

Air Barrier



Air Barrier


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2.6 Wall adjoining porch roof

To complete an air barrier at porch roofs, install blocking or another solid, sealed air barrier between the porch roof and conditioned space of the home.


Eyebrow roofs and porches, if

built wrong (left), can allow cold

air to penetrate exterior walls.

2.7 Staircase walls

An air barrier is needed at staircases where they come in contact with the exterior wall or attic above and below the stairs. This involves sealing any

gaps with caulk or foam, and providing a complete air barrier assembly.

Tape & joint



Structural sheathing

extend above & below

stringer to allow taping

with joint compound

2.8 Double walls

Double walls are becoming common in some markets to provide a more dimensional architectural appearance. The insulation must be aligned with

and enclosed by air barriers on all sides.

Interior air


Interior wall with


Exterior boundary

The interior wall

with exterior air


Interior air barrier

Exterior air barrier

Double wall area

filled with insulation

3.0 Floors Between Conditioned and Unconditioned Spaces

• An air barrier is installed at any exposed insulated edges.

• Insulation is installed to maintain permanent contact with sub-floor above including necessary supports (e.g., staves for blankets, netting for blown-in).

• Blanket insulation is verified to have no gaps, voids, or compression.

• Blown-in insulation is verified to have proper density with firm packing.

3.1 Insulated floor above garage

Floors constructed of dimensional lumber can be easier to block, insulate and seal than those constructed with engineered framing members. With

dimensional lumber, only the two open ends of the joist cavities need to be blocked and air sealed.

Floor assemblies constructed with open web trusses can be very difficult to effectively block, insulate, and air seal. In particular, open web areas are

labor-intensive to fill with batt or rigid insulation but can easily be filled with blown or spray insulation. All four edges of an open-web truss floor

assembly require the installation of a sheathing material to enclose the entire floor cavity and then all joints and penetrations need to be air sealed.


The installation of

sheathing material on all

four edges to enclose the

floor assembly.

Air seal

All joints in the sheathing

material must be air

sealed. The sheathing

must be air sealed to the

subfloor and also to the

drywall on the bottom.

Drywall ceiling

Diagram courtesy of McGrann Associates, Inc.

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3.2 Cantilevered floor

4.0 Shafts

Openings to unconditioned space must be fully sealed with solid blocking or flashing.

4.1, 4.2 Duct shaft & pipe penetrations 4.3 Flue shaft

Seal and insulate

dropped soffit




electrical boxes

and fixtures to




Seal electrical





Seal plumbing




5.0 Attic / Ceiling Interface - ≥ 19 R-Value

5.1 Attic access panel 5.2 Attic drop-down stair

(with full gasket and insulated)

(with full gasket and insulated)

Insulation dams

prevent loose-fill

insulation from

falling through


Hatch lid pushes up and

out of the way for access

. .

Cover Raised box frame pushes provides up

and insulation out of blocking the way . for


Rigid insulation box

forms lid for pull-down

attic staircase


Lid swings up

firmly attach


Build up staircase frame

and hinge rigid top and

attach insulation

Air seal .


Air seal


Scuttle hole cover

Air seal




Pull-down attic Panel staircase

Pull-down attic staircase


Seal stairs

frame gap

with caulk

or foam

Seal stairs

frame . gap

with caulk

or foam

5.3 Dropped ceiling / soffit

(full air barrier aligned with insulation

when soffit adjoins exterior walls)


5.4 Recessed lighting fixtures

(icat labeled and sealed to drywall)

Fixture tested for air leakage

Tight housing


Some have gaskets..

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5.5 Whole-house fan (insulated cover with gasket)

Whole house fan

Whole house

6.0 Common Walls Between Dwelling Units

A solution to thermal bypass at common walls is to air seal the gaps between the drywall and framed common walls using expanding foam (if allowed by

code) or fire rated blocking or caulk.

A i r s e a l h e r e

F r a m e d w a l l

D r y w a l l





Cooling equipment shall be sized according to the latest editions of ACCA Manuals J and S, ASHRAE 2001 Handbook of Fundamentals, or an

equivalent procedure. Maximum over-sizing limit for air conditioners and heat pumps is 15%.

Duct seams and air handler

sealed with mastic

All transverse seams in supply and return ducts,

including supply and return plenums and leakage

sites in the air handler, shall be sealed with duct

mastic and fibrous reinforcing mesh according to

SMACNA specifications. Duct tape is not a suitable

sealant for ducts but may be used for sealing

leakage sites at the air handler’s removable

access panels and at filter access panels.

All supply duct take-offs

spaced 6 inches apart

All supply duct

take-offs shall

be spaced at

least 6 inches

apart from

each other

with no duct



from the cap

of the supply



boxes with 4

take-offs or

less are


Allow 6" clearance on all

sides and between

duct take-offs

from plenum

Seal all joints

and seams in

air handler and

ductwork with

mastic or

mastic tape

Seal collars to

plenum with

mastic or

mastic tape

Use removeable tape for

filter door

Flex duct properly installed

Correctly supported flex duct

5' maximum

Sag ½" per foot

of support spacing

Sag ½" per foot

of support spacing

Smooth turns – no sharp angles


Correctly supported flex flex duct duct installed with enough material, to create Correct:

smooth turns with proper angles

flex duct installed with enough material, to create

smooth turns with proper angles

5' maximum

Mastic or

mastic tape

Mastic or

mastic tape

Incorrectly supported

flex duct




flex duct installed with extra material, creating Incorrect:


flex duct turns with pinched angles

flex duct installed with extra material, creating bunched

turns with pinched angles

Always seal

with mastic

or mastic tape


Always seal

with mastic

or mastic tape

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Ceiling boot air sealing Floor boot air sealing


Sealing return plenum

All air handlers shall be installed with a ducted

return plenum sealed to the unit and any

associated ducts with mastic or mastic tape.

No supply or return ducts,boots or registers

shall be located in exterior walls.


ENERGY STAR MANUAL—J Load Calculation Requirements

ENERGY STAR standards require that a load calculation be performed on every home in accordance with the latest version of ACCA Manual J

(currently version 8). ENERGY STAR requires that the following inputs be used for the Manual J:

• Maximum allowable duct leakage is 6 cfm to outdoors / 100 sq. ft.(6%) of conditioned floor area if certified by Performance Path (HERS Rating)

or 4 cfm to outdoors / 100 sq. ft.(4%) of conditioned floor area if certified by Builder Option Package (BOP).

• If software allows for grades of duct tightness, choose “tight” or the equivalent term.

• Outdoor temperatures shall be the 99.0% design temperatures as published in the ASHRAE Handbook of Fundamentals for the home’s location

or most representative city for which design temperature data are available.

• House infiltration shall be based on (0.5 CFM50/SFBE) or shall use the software choice of “tight” or the equivalent term.

• Must use actual house orientation and location.

• Must use actual window, insulation and door specifications.

• Indoor temperatures shall be 75°F for cooling and 70°F for heating.

The results of the Manual J must be used when sizing and installing equipment. ENERGY STAR requires the following sizing guidelines:

• Maximum over sizing limit for air conditioners and heat pumps is 15%.

• In specifying equipment, the next available size may be used.

• The indoor and outdoor coils shall be matched in accordance with ARI standards. Provide the ARI Certificate of ARI-Certified Performance

(from or manufacturer’s performance data to the Home Energy Rater.

Builders must submit the completed Manual J documentation to Rappahannock Electric Cooperative.

• Documentation must show that all above requirements have been met.


Air Conditioning Contractors of America Insulation Contractors Assoc. of America

2800 Shirlington Rd, Suite 300 (ICAA)

Arlington, VA 22206 1321 Duke St, Suite 303

Ph (703) 575-4977 Alexandria, VA 22314

Ph (703) 739-0356

Alliance to Save Energy

National Rural Electric Cooperative Association (NRECA)

1850 M. Street, NW, Suite 600 4301 Wilson Boulevard

Washington, DC 20036 Arlington, VA 22203

Ph (202) 857-0666 Ph (703) 907-5699

Earth Craft Virginia

Residential Energy Services Network (RESNE)

1840 W. Braod St., Suite 200 PO Box 4561

Richmond, VA. 23220 Oceanside, CA 92052

Ph (804) 225-9843 Ph (760) 806-3448

Energy Efficient Building Association U.S. Environmental Protection Agency

10740 Lyndale Ave., South, 10W 1200 Pennsylvania Ave., NW

Bloomington, MN 55420 Washington, DC 24060

Ph (952) 881-1098 Ph (202) 564-2300

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This panel to be dropped in from existing files.

A service of:

P.O. Box 7388

Fredericksburg, VA 22404



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