ENERGY STARMultifamily High Rise Program

Introduction to the Prescriptive Path

July 2011

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Prescriptive Path Components

• Prerequisites

• Performance Target

• Simulation Guidelines

• Performance Path Calculator

• Modeling Checklist

• Prescriptive Requirements

• Testing and Verification (T&V)

• Benchmarking

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Prerequisites & Prescriptive Requirements

• Appliances

• Heating and Cooling Equipment & Distribution

• Envelope

• Garages and Sidewalks

• Ventilation and Infiltration

• Domestic Water Heating

• Lighting

• Pump Motor Efficiency

Appliances

• When provided in common areas and/or apartments, refrigerators, dishwashers, clothes washers, ceiling fans, ceiling exhaust fans, in-line exhaust fans and vending machines must be ENERGY STAR qualified.

• No additional Prescriptive requirement.

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Heating and Cooling Equipment – ASHRAE Mandatory Provisions

• The heating and cooling systems must comply with ASHRAE 90.1-2007, Section 6.4.

• In addition, the systems must also comply with Prescriptive Path Section 6.5.

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Heating and Cooling Equipment – Sizing and Load Calculations

• Load sizing calculations must reflect the design. The installed capacity cannot exceed design by more than 20%, except when smaller sizes are not available.

• Loads must be calculated and equipment selected per latest editions of ACCA Manual J & S, ASHRAE 2009 Handbook of Fundamentals, or equivalent procedure.

• No additional Prescriptive requirement.

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Heating and Cooling Equipment – Minimum Efficiencies

• See Table 1 for list of equipment and minimum efficiencies per ASHRAE 90.1-2007 climate zones.

• See ASHRAE 189.1-2009 for equipment not listed in Table 1.

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Heating Equipment – Prescriptive Requirements

• No electric resistance space heating is permitted in any space.

• Atmospherically vented gas furnaces and boilers cannot be specified.

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Heating Equipment – Minimum Efficiencies for Boilers

• In Climate Zones 1-5: Boilers < 300,000 Btuh must be ≥ 85% AFUE.

• In Climate Zones 6-8: Boilers < 300,000 Btuh must be ≥ 90% AFUE.

• Boilers ≥ 300,000 Btuh must be ≥ 87% Et, or ≥ 89% Et if used with water-source heat pumps.

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Heating Equipment – Minimum Efficiencies for Furnaces

• For CZ 1, 2, and 3, in-unit warm-air furnaces <225,000 Btuh must be 80% AFUE or greater.

• For CZ 4&5, in-unit warm-air furnaces <225,000 Btuh must be ENERGY STAR qualified.

• For CZ 6, 7 and 8, in-unit warm-air furnaces <225,000 Btuh must be 95% AFUE or greater if gas-fired and 90% AFUE or greater if oil-fired.

• Furnaces <225,000 Btuh serving common areas must be greater than 78% AFUE.

• Warm-air furnaces ≥225,000 Btuh must be ≥80% Et if gas-fired and ≥81% Et if oil-fired.

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Heating and Cooling Equipment – Minimum Efficiencies for PTAC/PTHP

• Equations based on capacity determine minimum efficiencies for PTACs and PTHPs.

• Example: PTAC

EER=13.8-(0.3xCap/1000)

“Cap” is capacity and must be a number between 7,000 and 15,000 Btuh.

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Heating and Cooling Equipment - Minimum Efficiencies for ASHPs

• Air-cooled heat pumps in Climate Zones 1 and 2, must meet or exceed SEER 15 and 8.2 HSPF.

• They must be ENERGY STAR qualified in Climate Zones 3 to 8.

• Climate Zones 4-6 have additional HSPF requirements.

• Dual-fuel for zones 7&8

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Cooling Equipment – Minimum Efficiencies for Split ACs

• Split system air conditioners in any zone that are less than 13,000 Btuh must be SEER 13 or greater.

• For Climate Zones 1 and 2, split system ACs must be SEER 16 or greater.

• For Climate Zones 3, 4 and 5, split system ACs must be ENERGY STAR qualified.

• For Climate Zones 6, 7 and 8, split system ACs must be SEER 13 or greater.

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Cooling Equipment – ENERGY STAR or better

• In all zones, all window, through-wall, and mini-split air conditioners (or heat pumps) must be ENERGY STAR qualified.

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Heating and Cooling Equipment-Other Prescriptive Requirements

• Cooling tower fan motors must be equipped with variable frequency drives that are controlled by a temperature sensor on the condenser water supply pipe.

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Heating and Cooling Distribution – Ducted Forced Air System Design

• For in-unit ducted forced air distribution systems, perform design calculations (using ACCA Manuals J and D, the ASHRAE Handbook of Fundamentals, or an equivalent procedure) and install ducts according to design.

• Flex duct shall follow the Sheet Metal and Air Conditioning Contractors’ (SMACNA) installation standards for flex ducts.

• Bedrooms must be pressure-balanced.• No additional Prescriptive Requirement.

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Heating and Cooling Distribution – Insulation

• Heating and cooling supply and return ductwork must be insulated to a minimum R-8 in unconditioned space.

• Piping carrying fluid or steam with temperatures less than 60°F or greater than 105°F, must have a minimum of 1” of insulation. Pipes over 1.5” in diameter must have a minimum of 1.5” of insulation. (No additional requirement.)

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Heating and Cooling Distribution –Sealing and Leakage

• Heating and cooling ductwork must be sealed at all transverse joints and connections, including ductwork connections through drywall or other finish materials, using UL-181 compliant methods and materials.

• Total duct leakage for in-unit ducted forced air systems shall be:

≤6 CFM25 per 100 ft2 of conditioned floor area for units 1200 ft2 and greater.

≤8 CFM25 per 100 ft2 of conditioned floor area for units less than 1200 ft2.

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Heating and Cooling Distribution

• Controls• Thermostats• Outside air dampers• Hydronic design• No additional Prescriptive Requirement.

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Envelope – Air Barrier & Infiltration

• The building plans shall demonstrate a continuous, unbroken air barrier separating the conditioned space of the building from the exterior and other unconditioned or commercial spaces.

• Apartments shall be sealed to reduce air exchange between the apartment and exterior as well as the apartment and adjacent spaces.

• A maximum air leakage rate of 0.30 CFM50 per square feet of enclosure is allowed.

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Envelope

• The envelope components must comply with ASHRAE 90.1-2007, Section 5.4.

• See Tables 2 and 3 of the Prescriptive Path for minimum R-values and maximum assembly U-values per ASHRAE climate zones.

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Envelope – Climate Specific Requirements

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• Roof• Above-Grade Walls• Below-Grade Walls• Floors• Slabs

– Unheated– Heated

• Exterior Doors• Vertical Glazing

– Nonmetal– Metal

Envelope – Climate Specific Requirements

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• For example, an attic in Climate Zone 5 would prescriptively need R-49 in between roof rafters.

• If selecting another insulation method, the U-value of the roof assembly cannot exceed U-0.021.

Envelope – U-values, Insulation Grade

• U-value determinations must follow ASHRAE 90.1-2007, Appendix A.

• An area weighted average of the U-values of the wall and floor perimeter assemblies is acceptable.

• RESNET-defined Grade I insulation installation or Grade II if combined with continuous insulation (≥R-3 in CZ 1-4 and ≥R-5 in CZ 5-8).

• No additional prescriptive requirement.

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Envelope – Vestibules & AC sleeves

• When required by local building code, entranceways shall be designed with vestibules with weather-stripping hard-fastened to the door or frame.

• Insulated covers (R-7 or higher) for through-wall AC units must be provided by the building for use during the heating season or when AC units are not installed.

• No additional prescriptive requirement.

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Envelope – Walls & Windows

• For steel-framed and metal buildings, continuous exterior insulation is required.

• For masonry buildings with metal framing, continuous interior or exterior insulation is required.

• Specified windows must be double or triple-pane, with low-e glass or coatings.

• Maximum allowable window to wall ratio: 30%

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Garages and Sidewalks

• Garages shall be fully compartmentalized. • All pipe & conduit penetrations shall be sealed.• Garages shall not be heated for comfort or to

prevent pipes from freezing.• Radiant heating, either wall or ceiling-mounted

or within the garage floor (or sidewalks) may be used to prevent ice formation on the ground as a safety feature only.

• When exhaust is required by code, CO sensors must be installed to control operation.

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Ventilation – ASHRAE 62 requirements

• Common area ventilation systems shall be designed and tested to satisfy minimum requirements of ASHRAE 62.1-2007.

• Apartment ventilation systems shall be designed and tested to satisfy minimum requirements of ASHRAE 62.2-2007 based upon the anticipated occupancy.

• Measured rates cannot exceed ASHRAE 62-2007 rates by more than 50%.

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Ventilation – Duct sealing & Leakage

• Ventilation system ductwork must be sealed at all transverse joints and connections including boot to wall/ceiling connections through drywall using UL-181 compliant materials and methods.

• Ductwork penetrations must be sealed at the roof curb to prevent air leakage through the duct system and/or the building envelope.

• Central exhaust systems must be tested for duct leakage, which cannot exceed 5 CFM50 per floor per shaft. See T&V Protocols for details.

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Ventilation – Controls

• Central exhaust fans ≤ 1/16 HP must be direct-drive and have variable speed controllers.

• Central exhaust fans between 1/16 and 1 HP must be direct-drive with ECM motors and variable speed controllers.

• Central exhaust fans 1 HP and larger must have NEMA Premium efficient motors.

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Ventilation – Controls, continued

• Central exhaust and in-line exhaust systems serving apartments must have self-balancing dampers at each grille.

• Powered common laundry ventilation must be installed with automatic demand control to turn off ventilation fans when no dryers are operating. 

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Domestic Water Heating – ASHRAE Mandatory Provisions

• Domestic water heating systems must comply with ASHRAE 90.1-2007, Section 7.4 and 7.5.

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Domestic Water Heating – Minimum Efficiencies

• Domestic water heating equipment shall be ENERGY STAR qualified, where applicable.

• Minimum Efficiencies:

Hot Water Supply Boiler (oil or gas): 85% Et

In-Unit Storage or Instantaneous:

Gas (EF): 0.69-(0.002 x Tank Gallon Capacity)

Electric (EF): 0.97-(0.001 x Tank Gallon Capacity)

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Domestic Water Heating - Type

• Atmospherically vented gas water heaters, tankless coils and side-arm water heaters shall not be specified.

• If storage is provided, the maximum storage tank capacity shall be specified based on occupancy.

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Domestic Water Heating – Temperature and Pressure

• Self-contained or electronic mixing valves shall be used to control hot water temperature for central domestic water heating systems.

• The temperature of the stored hot water shall be just sufficient to deliver water to apartments within a temperature range of 120-125°F.

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Domestic Water Heating – Low Flow

• All lavatory faucets or aerators must be WaterSense labeled.

• The average flow rate for all other faucets must be ≤ 2.00 gpm.

• The average flow rate for all showers must be ≤ 1.75 gallons per minute per stall and all showerheads must be WaterSense labeled.

• All tank-type toilets must be WaterSense labeled.

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Lighting

• Lighting must comply with ASHRAE 90.1-2007, Section 9.4.

• 80% of installed light fixtures must be ENERGY STAR qualified or have ENERGY STAR qualified lamps (bulbs) installed.

• Lighting must be designed to meet light levels (footcandles) by space type as recommended by the Illumination Engineering Society (IESNA) Lighting Handbook, 9th edition.

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Lighting – Footcandles (lumen/ft2)

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ASHRAE Space Type

Lighting Power

Densities (W/ft2)

Recommended Light Levels

(Weighted Avg. Footcandles)

ASHRAE Space Type

Lighting Power

Densities (W/ft2)

Recommended Light Levels

(Weighted Avg. Footcandles)

Apartments 0.75* 16 Stairway 0.69 15

Storage 0.63 20 Restroom 0.98 12

Elevator 0.64 16Office (enclosed/open)

1.11/0.98 35

Food Preparation

0.99 40Conference/meeting/multipurpose

1.23 30

Dining Area - For Family Dining

0.89 23Electrical/Mechanical

0.95 30

Lobby 0.90 16 Workshop 1.59 50

Corridor/Transition

0.66 10 Parking garage 0.19 7

Lighting – Common Areas

• All non-apartment spaces, except those where automatic shutoff would endanger the safety of occupants, must have occupancy sensors or automatic bi-level lighting controls. Automatic controls are required in 24-hour areas such as corridors and stairwells.

• Total installed lighting power for the combined common spaces should not exceed ASHRAE 90.1-2010 allowances for those combined spaces.

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Lighting – ASHRAE 90.1-2010 Lighting Power Densities (LPDs)

ASHRAE Space Type

Lighting Power

Densities (W/ft2)

Recommended Light Levels

(Weighted Avg. Footcandles)

ASHRAE Space Type

Lighting Power

Densities (W/ft2)

Recommended Light Levels

(Weighted Avg. Footcandles)

Apartments 0.75* 16 Stairway 0.69 15

Storage 0.63 20 Restroom 0.98 12

Elevator 0.64 16Office (enclosed/open)

1.11/0.98 35

Food Preparation

0.99 40Conference/meeting/multipurpose

1.23 30

Dining Area - For Family Dining

0.89 23Electrical/Mechanical

0.95 30

Lobby 0.90 16 Workshop 1.59 50

Corridor/Transition

0.66 10 Parking garage 0.19 7

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Lighting – Calculations

• The requirement of ASHRAE 90.1-2007, Section 9.1.4a, that light fixtures MUST be calculated with the maximum labeled wattage of the fixture is not required.

• Example: A fixture with a 13 W screw-in CFL can be modeled as 13 W, plus any associated ballast power. See Appendix B of Prescriptive Path for suggested ballast power.

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Lighting – Calculations inside Units

• Overall in-unit lighting power density may not exceed 0.75 W/ft2.

• Use 1.1 W/ft2 for areas inside units where lighting is not installed (ex. Living rooms and bedrooms that use switched outlets).

• Use data from light fixtures to calculate LPD of spaces where lighting is installed and take the weighted average to get the overall LPD.

• In spaces where supplemental lighting will be needed, installed fixtures may only illuminate up to 2 ft2 per Watt.

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Lighting – Calculations inside Units

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BR1 – 150 ft2

BR2 – 150 ft2

Bath – 50 ft2

Kitchen - 200 ft2

Living Room- 300 ft2

Hall – 100 ft2

950 ft2 x 0.75 Watts/ft2 = 712 Watts

Lighting – Calculations inside Units

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BR1 – 150 ft2

BR2 – 150 ft2

Bath – 50 ft2

Kitchen - 200 ft2

Living Room- 300 ft2Hall – 100 ft2

Unlit area –100 ft2, assume 110 W supplied by occupant

Lit area –200 ft2, 100 W installed

Lighting – Exterior

• 80% of outdoor lighting fixtures must be ENERGY STAR qualified or have ENERGY STAR qualified lamps installed.

• Fixtures must include automatic switching on timers or photocell controls except fixtures intended for 24-hour operation, required for security, or located on apartment balconies.

• Total installed exterior lighting power cannot exceed ASHRAE 90.1-2010 allowances.

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Lighting – Exit Signs

• All exit signs must be specified as LED (not to exceed 5W per face) or photo-luminescent and must conform to local building code; fixtures located above stairwell doors and other forms of egress must contain a battery back-up feature.

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Pump Motor Efficiency

• All three-phase pump motors 1 HP or larger shall meet or exceed efficiency standards for NEMA Premium™ motors, where available.

• Many motors are NEMA labeled and this label alone, does not ensure that a motor is energy-efficient. This requirement refers specifically to the NEMA Premium energy efficient motors program.

• Motors 5 HP or larger for circulating pumps serving hydronic heating or cooling systems must be specified with variable frequency drives.

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Metering

• The commercial/retail parts of the building shall be separately metered or sub-metered for electricity, gas, fuel oil, water, and steam, where applicable.

• The building owner must secure signed utility bill releases from individual apartment occupants to allow for benchmarking or obtain whole-building consumption data from their local utility.

• The building owner must provide a signed release for the common area/whole-building utility meters.

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Testing and Verification

• Buildings following the Prescriptive Path must also follow the Testing and Verification Protocols.

• These protocols are the mandatory requirements for the inspection, testing and verification of components related to the building’s energy performance.

• The intent of the protocols is to verify that – the construction documents & final building include all

Prerequisites and Prescriptive requirements.– measures have been installed and perform as

expected.

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Testing and Verification

• Changes to the initial design noted during inspections must be reflected in the revised T&V Worksheets and submitted at the end of construction.

• All Prescriptive requirements must still be met in order to earn the ENERGY STAR. If any are not met, an As-Built energy model could be used to earn the ENERGY STAR, if it meets the 15% Performance Target and Prerequisites.

• The T&V Worksheets and Photo Template must be submitted as they document the results of all mandatory testing and verification.

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Prescriptive Path Components

PrerequisitesPrescriptive RequirementsTesting and Verification (T&V)

• Benchmarking

Prescriptive Path Steps

• Apply to Program; become Partner• Meet Prerequisites & Prescriptive requirements• Review plans, submit T&V worksheets to EPA• Build according to Design• Conduct Testing and Verification• Submit T&V worksheets and Photo Template to

EPA• Earn ENERGY STAR • Benchmark for two years

The End

Questions?

Contact: MFHR@energystar.gov

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