The bitterness of poor quality is remembered long after The bitterness of poor quality is remembered long after the sweetness of low price is forgotten!the sweetness of low price is forgotten!

Heat Pump Sizing Using ACCA Heat Pump Sizing Using ACCA ManualManual J8 J8 ItIt’’s a Building Code Requirements a Building Code Requirement

Size the Equipment BEFORE You BuildSize the Equipment BEFORE You Build

HVAC

• Heating, Ventilation and Air Conditioning

• Provides comfort for people• Allows humans to exist under adverse

conditions.

WHY CARE ABOUT THE HVAC EQUIPMENT?

Human Comfort Zone

(After All, it(After All, it’’s Humans s Humans WeWe’’re Experimenting With)re Experimenting With)

HEAT PUMP SIZING

FSEC Study (1996 – 489 HVAC contractors)

•Rules of thumb prevail•Intentionally oversize•Tons per square foot (350-700)•Whatever’s on sale•CFM per square foot•Manual J (33%)

COMFORT

• Comfort is primary intent of HVAC systems.

• Productivity• Building Durability• Health• Mold

HVAC BUZZWORDS

• BTU = British Thermal Unit – energy to heat 1 pound of water from 39°F to 40°F

• 1 Ton = 12,000 BTUh• Dry Bulb Temperature = air temperature• Wet Bulb Temperature = “temperature of adiabatic saturation”

psychrometer or a piece of cloth on a thermometer, temp it evaporates –less than dry bulb

• Dew Point = Temperature were air is saturated and condensation starts• Relative Humidity = Amount of water vapor in the air• CFM = Cubic Feet per Minute, air volume• FPM = Feet Per Minute, air velocity• Pascal Pa = Pressure (1 Pa = .000145 Psi) ~ 250 Pa = 1” wc• Sensible Load = reduces the temperature• Latent Load = reduces the moisture• Sensible Heat Ratio (SHR) = ratio between the sensible and total load• Grains for moisture = indicate amount of water vapor per pound of air• Manual J = method for estimating the loads• Manual D = method for designing & sizing the duct work from the Manual

J• Psychrometrics = the measurement of the heat and water vapor

properties of air • Enthalpy = a measure of the total energy of a thermodynamic system

HEAT PUMPS

• Heat pumps “remove” heat from the house in the summer and dump it outside– cooling season

• Heat pumps “remove” heat from the outside air in the winter and dump inside – heating season

• Cooling Degree Days (CDD) & Heating Degree Days (HDD) – typical outside base 65°F (example Avg temp for the day is 80°F – 65°F= 15 CDD for one month 450 CDD

• North Florida – Climate Zone 2 – design for the cooling season

HEAT FLOW

• Conduction• Convection• Radiation

SOLAR HEAT GAIN COEFFICIENT (SHGC)

• The amount of solar heat energy allowed to pass through a window

• Example: SHGC = 0.40• Allows 40% through and

turns 60% away

ENERGY EFFICIENCY

LOW-E WINDOWS AND COMFORT

Mean Radiant Temperature (MRT) has 40% Mean Radiant Temperature (MRT) has 40% more impact than ambient temperaturemore impact than ambient temperature

70700 0 F Ambient/65% RHF Ambient/65% RH

77770 0 FF77770 0 FF 9090

0 0 FF90900 0 FF

76760 0 F Ambient/45% RHF Ambient/45% RH

Less ComfortLess ComfortMore ComfortMore Comfort

CONTROLLING AIR FLOW:RULE #1

Where there is a Where there is a driving forcedriving force, , air will take the path of least air will take the path of least resistance through largest hole.resistance through largest hole.

airair

CONTROLLING AIR FLOW: RULE #2

More PressureMore PressureMore MoistureMore Moisture

More HotMore Hot(air and moisture)(air and moisture)

Less PressureLess PressureLess MoistureLess MoistureLess HotLess Hot

Driving Forces always move inDriving Forces always move inpredictable directions:predictable directions:

CONTROLLING AIR FLOW:RULE #3

One OutOne Out = One In= One In

HVAC SYSTEM DESIGN

Importance of Design• Undersized systems = discomfort• Oversized systems = wear & tear on equipment, discomfort (cooling), unnecessary expense, higher initial cost• Duct design can affect efficiency and system’s ability to heat/cool evenly

The “RIGHT SIZED” equipment is critical for performance. 95% of problems related to over sizing, duct leakage, poor duct design

OBTAIN A GOOD SYSTEM DESIGN AND INSTALLATION

• Find a contractor that will take the time to design and install it right• Create specifications for contractors• Ensure specifications are followed

The HVAC equipment, duct layout, and ductwork The HVAC equipment, duct layout, and ductwork are the are the ““heart, veins & arteriesheart, veins & arteries”” of the house.of the house.

Seek out “Best Value” – this is a “cost” avoidance issue -cheap doesn’t work unless you want lots of call backs.

STEPS to a COMFORTABLE HOMEOWNER

• Manual J8 – Load Analysis• Manual D – Duct system design & sizing• Manual S – Equipment selection• Installation – duct sealing/insulation,

thermostat location• Commissioning – Compressor and AHU checks• Ducts – verify CFM/FPM and balance system

MANUAL J8

• Procedure used to estimate the heat loss and gain of conventional residential structures for the purpose of HVAC sizing

• Determine room-by-room loads• Manual J examines:

– Enclosure elements– Air leakage– System losses / gains– Sun position– Latent and internal gains

HEAT LOSS

HEAT GAIN

HEAT TRANSFER

U-Value is the rate of heat flow in Btu/h through a one ft2 area when one side is 1oF warmer

Resistance (R-Value)U = 1 / RExample R30 = U.033 ~ R11 = U.09

Measuring Heat LossQ = U x A x ∆T

• Q = heat flow (BTUH)• U = thermal conductivity (U=1/R)• A = surface area (square feet)• ∆T = temperature difference across component (°F)

HOW MANUAL J WORKS

• BTUH heat loss or gain through an assemblyQ BTUH = U x A x ∆T

• Example– 500 sq. ft. of wall insulated to R-19– Interior temp at 75° and exterior at 89°– U-value = 1/R – value: 1/19 = .053– Delta T is the difference in temperature across a building

component that governs heat loss or gain: 89° - 75° = 14°

.053 x 500 x 14 = 371 BTUH

OBJECTIVES OF MANUAL J8 LOAD CALCULATION

•To determine the proper sizing of HVAC equipment for a structure(Block Load) •To determine the heating & cooling requirements for individual rooms ( Room by Room load) •Determine Proper Duct Design

Why Bother Sizing?Obviously don’t want one to small

Avoid CallbacksSo just make it real big

HIGH PERFORMANCE HOUSES

• So what is the cause for concern?– Improved thermal envelope leads to reduced

heating and cooling loads which results in smaller HVAC equipment

– Used to use 400 sqft / ton as an estimation of size

– Now 600 and up to 1000 sqft / ton – Reduced amount of airflow in the system– Standard to oversize ducts result in lower

velocities– Lower velocities at diffusers reduce throw and

mixing– Impact of duct leakage is amplified

WHY USE MJ8

The heating and cooling load estimates affect every aspect of the system design procedure

•Type of system (variable volume/capacity)•Equipment selection•Placement and selection of air distribution hardware•Duct routing and airway sizing or pipe layout and sizing

Because of this the load calculation must be as accurate as possible

DESIGN CONDITIONS ONLY OCCUR FOR A FEW DOZEN HOURS PER SEASON

RADIANT LOADS CAN HAVE THE LARGEST IMPACT

EAST ElevationEAST Elevation WEST ElevationWEST Elevation

WATCH the INPUTS

LOAD VS TOTAL CAPACITY

The total system capacity ~ example: 3 TONS (36,000 The total system capacity ~ example: 3 TONS (36,000 Btuh) is required only about 3Btuh) is required only about 3--4% of the time.4% of the time.

MJ8 ROOM by ROOM

AIR INFILTRATION

Measures how much air leaks in/out of a home’s envelope by studying how much air must be removed from the home to reach a certain pressure level (50 Pascal reference), thus testing the efficiency of the building envelope.Directly influences the size of the equipment because it affects the latent and sensible loads.

Blower Door Test

DUCT LEAKAGE

Influences how the building reacts in terms of health, safety, durability, comfort, and energy efficiency.

•Can be estimated with a high degree of accuracy.•Can be tested with a high degree of accuracy.•Can be eliminated.

HEAT PUMP EFFICIENCY

Heating Mode• Measured by HSPF • ENERGY STAR at HSPF 8.2Cooling Mode• Cooling efficiency measured by SEER• Federal minimum SEER 13• ENERGY STAR criterion SEER 14

ENERGY EFFICIENCY

EQUIPMENT RIGHT-SIZING

BenefitsBenefits::•• Lower CostLower Cost•• Increased Efficiency Increased Efficiency •• Longer Lifetime Longer Lifetime •• Better Moisture Better Moisture

ControlControl•• Improved ComfortImproved Comfort•• Reduced CallbacksReduced Callbacks

14

13

12

11

10

9

8

7

SEER

NEW CONSTRUCTION MISTAKES

•The Infiltration always is a guess!!!•Using the wrong Infiltration rate•Actually just assume leaky construction•Assuming Duct & Envelope Leakage Equivalent•Same plan is used for multiple subdivisions•Looking at worst case scenarios•Not Evaluating Overhangs & Benefits•Add some for parties•What’s on sale

All of this can lead to improper sizing of HVAC Equipment

THE SCIENCE BEHIND THE VALUE CONTROLLING AIR FLOW: INSULATION

Resists Heat FlowResists Heat Flow

Air FlowAir Flow

……need need Air BarrierAir Barrier

THE SCIENCE BEHIND THE VALUE

WHY CONTROL AIR FLOW?

Warm AirWarm AirGets Cold Gets Cold

Loses MoistureLoses Moisture

Impact:Impact:All action happens at All action happens at surfaces where warm surfaces where warm air can condensate on air can condensate on cold surfaces. cold surfaces. Air flow must be Air flow must be controlled to avoid controlled to avoid moisture problems.moisture problems.

THE SCIENCE BEHIND THE VALUE

WHY CONTROL AIR FLOW

Without Insulation:Without Insulation:

Inside:Inside:7070ooF, 45F, 4500F Dew Pt.F Dew Pt.Outside:Outside:

3030ooFF

5555ooFF3434ooFF

With Insulation:With Insulation:

Impact:Impact:Insulated walls create Insulated walls create cold surfaces.cold surfaces.Insulated homes must Insulated homes must be sealed tight to avoid be sealed tight to avoid moisture problems.moisture problems.

THE SCIENCE BEHIND THE VALUE

CONTROLLING MOISTURE FLOW

HotHot--Humid ClimateHumid Climate::

Inside:Inside:7070ooFF

Outside:Outside:8585ooF, F,

DrivingDrivingForceForce

7272ooFFVapor BarrierVapor Barrierfaced insulation, faced insulation, faced sheathing, faced sheathing, unfaced insulation.unfaced insulation.

ENERGY EFFICIENCYINSULATION: VALUE KILLERS

••Incomplete Air BarrierIncomplete Air Barrier••Misalignment with Air BarrierMisalignment with Air Barrier•• GapsGaps•• VoidsVoids•• CompressionCompression•• Wind IntrusionWind Intrusion

ENERGY EFFICIENCY

ALIGN AIR AND THERMAL BARRIERS

•• ContinuousContinuous•• Full contact withFull contact with

interior air barrier interior air barrier (e.g., sheet rock)(e.g., sheet rock)

•• Fully enclose Fully enclose conditionedconditionedspacespace

ENERGY EFFICIENCYAIR BARRIER ALIGNMENT: BONUS ROOM

125125ooFF

110110ooFF 110110ooFF

100100ooFF

BonusBonusRoomRoom

GarageGarageThermal Thermal

BypassBypassThermal Thermal BypassBypass

SolutionSolution::••align insulationalign insulation••add air barriersadd air barriers

ENERGY EFFICIENCYAIR BARRIER ALIGNMENT: CANTILEVER

SolutionSolution::••align insulationalign insulation••add air barriersadd air barriers

Thermal Thermal BypassBypass

Thermal Thermal BypassBypass

Cantilever Cantilever

ENERGY EFFICIENCY

TIGHT CONSTRUCTION: WHY?

•• Eliminate unwanted heat loss/gain Eliminate unwanted heat loss/gain •• Eliminate potential moisture problemsEliminate potential moisture problems

by avoiding humid air flow through construction by avoiding humid air flow through construction assembliesassemblies

•• Eliminate outdoor pollutantsEliminate outdoor pollutants(e.g., humidity, dust, pollen)(e.g., humidity, dust, pollen)

ENERGY EFFICIENCY

TIGHT CONSTRUCTION: HOW?

• Seal Un-designed Holes– Cracks– Holes– Shafts

• Control Air Flow with Designed Holes– Mechanical Ventilation– Exhaust Fans– Pressure Balancing

ENERGY EFFICIENCYTIGHT CONSTRUCTION: HOLES/CRACKS

ENERGY EFFICIENCY

ENERGY EFFICIENT DUCTS

•• Ducts Sized with ACCA Manual DDucts Sized with ACCA Manual D

•• Seal With MasticSeal With Mastic

•• InsulateInsulate

•• Avoid Using Building Cavities as DuctsAvoid Using Building Cavities as Ducts

•• Get it Inside if PossibleGet it Inside if Possible

ENERGY EFFICIENCY

SEALING DUCTS: PROBLEMS

ENERGY EFFICIENCY

SEALING DUCTS WITH MASTIC

ENERGY EFFICIENCY

ENERGY EFFICIENT EQUIPMENT

Heating:Heating:••Super Efficiency: Super Efficiency: 90+ AFUE90+ AFUE•• HSPF 8.2 HSPF 8.2 Cooling:Cooling:••14 SEER14 SEER••MultiMulti--SpeedSpeedAir Handler:Air Handler:••Variable Speed Blower Motor Variable Speed Blower Motor ••AirAir--Tight CabinetTight Cabinet

SUMMARYENERGY EFFICIENCYPERFORMANCE ADVANTAGE

Unless youUnless you’’re prepared to break the laws re prepared to break the laws of physics, energy efficiency delivers:of physics, energy efficiency delivers:

•• Lower Utility CostsLower Utility Costs•• More More ComfortComfort•• More Durability More Durability •• Improved Indoor Air QualityImproved Indoor Air Quality•• Environmental ProtectionEnvironmental Protection•• Less call backsLess call backs•• Happy Homeowner Happy Homeowner –– more salesmore sales

FOR MORE INFORMATION

Visit us on the Web:http://www.usahers.com

Or call Tim @ 904-571-9955Henry @ 904-233-7299