PHPP-IP | Cpourse I - 2 - Assemblies

2021

Up and Running with the Passive House Planning Package (9.7 IP) Module 1 | Class 2 | Assemblies

What do we want from the PHPP?

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1. What is the Annual (End) Energy Demand for Heating and Cooling?

2. What is the Peak Load for Heating and Cooling?

3. What is the total Annual Primary Energy Demand?

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Q: How do you calculate the heating energy demand?

A: (QT + QV) - η

Transmission + Ventilation LOSSES

(QS + QI)

Solar + Internal GAINS

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Q: How do you calculate annual the heat loss of a surface?

A: QT-srfc = Areasrfc ( ft2 )

In 1.

2.

3.

4.

U-Valuesrfc ( Btu / hr-ft2-F )

ft (%)

Gt ( kFhr / yr)

order to calculate the transmission heat loss for each surface of a building, we need to: Determine the surface area Determine the surface’s U-Value Determine the temperature correction factor Determine the annual difference in temperature between inside and outside

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U-Values

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What the heck is a U-Value?

U-Values are a measurement of

Btu/hr-ft2-F How many Btus flow…. …. Over one hour …. Through one square foot of surface …. For each degree (F) of difference

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U-Values are a measure of heat flow through an assembly R-Values are a measure of an assembly’s resistance to heat flow U-Value = 1 / R-Value R-Value = 1 / U-Value

For instance: R-40 à 1/40 = U-Value of 0.025 U-0.025 à 1/0.025 = R-Value of 40 bldgtyp | NYPH

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Example: 4” XPS Insulation (R-20) QT-surface = Areasurface

68 F

U-Valuesurface

ft

Gt

10’-0”

Areasurface = 10’ x 30’ = 300ft2 28 F

U-Valuesurface = 1/20 = 0.05 Btu/hr-ft2-F ft = 1.0 Gt = 120 kFh/yr

30’-0”

QT-surface = 300ft2

0.05 Btu/hr-ft2-F

1

120 kFhr/y

QT-surface = 1,800 Btu bldgtyp | NYPH

Example: 8” XPS Insulation (R-40) QT-surface = Areasurface

68 F

U-Valuesurface

ft

Gt

10’-0”

Areasurface = 10’ x 30’ = 300ft2 28 F

U-Valuesurface = 1/40 = 0.025 Btu/hr-ft2-F ft = 1.0

30’-0”

Gt = 120 kFh/yr

QT-surface = 300ft2

0.025 Btu/hr-ft2-F

1

120 kFhr/y

QT-surface = 900 Btu bldgtyp | NYPH

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Example: 16” XPS Insulation (R-80) QT-surface = Areasurface

68 F

U-Valuesurface

ft

Gt

10’-0”

Areasurface = 10’ x 30’ = 300ft2 28 F

U-Valuesurface = 1/80 = 0.0125 Btu/hr-ft2-F ft = 1.0

30’-0”

Gt = 120 kFh/yr

QT-surface = 300ft2

0.0125 Btu/hr-ft2-F

1

120 kFhr/y

QT-surface = 450 Btu bldgtyp | NYPH

Where do U-Values come from?

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Where do U-Values come from?

1. Building Codes 2. Engineering Reference Documents 3. Numerical Models 4. 2-D or 3-D Heat Flow Simulations

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NYS 2020 ECC: Assembly U-Value Throughout the code, we can find tables of U-Values (‘Effective’ R-Values) for various types of assemblies

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ASHRAE 90.1 Appendix A Appendix A includes more detailed tables of values which can be used for various assembly types

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BC Hydro Thermal Bridging Guide

https://betb.ca/

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BC Hydro Thermal Bridging Guide

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Numerical Calculation (Sometimes) Sometimes 90.1 Appendix A allows us to use a simplified numerical calculation to figure out our own U-Values

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ASHRAE HOF Chapter 25 and 27

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ISO 6946 ISO 6946 outlines essentially* the same calculation procedures and rules. This is the rules document to refer to for certain International Certifications such as ‘Passive House’

* Some small differences such as the exact surface film resistance value to use, etc.. bldgtyp | NYPH

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ASHRAE 1D Assembly U-Factor HOF Chapter 27: 1.1 R/inch Thickness

Layer R se

Layer Resistance 0.17

Vinyl Siding

1.24

×

1/2"

=

0.62

Bldg Paper

1.00

×

1/16”

=

0.06

OSB

1.24

×

1/2"

=

0.62

XPS foam

5.00

×

6”

=

30

Gyp Board

0.90

×

1/2"

=

0.45

R si

0.68 R-Value

=

32.60

U-Value

=

0.031

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ASHRAE 2D Assembly U-Factor Methods Int. ½” Drywall

3-½” Mineral Wool

5-½” Denspack Cellulose w/ Wd. Stud Framing 16” o.c. ½” Plywood Sheathing

R-Values Wood Studs: R-1.1/inch Plywood Sheathing: R-1.3/inch

3” Mineral Wool

Denspack Cellulose: R-3.2/inch Mineral Wool: R-4/inch

Ext.

Drywall: R-0.2/inch

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ASHRAE 2D Assembly U-Factor – Parallel Path Parallel Path Method R-per-Inch

Thickness

(hr·ft2·°F/Btu)

(inches)

Total Resistance (hr·ft2·°F/Btu)

Rsi (Int. Wall)

PATH 1

PATH 2

0.68

0.68

Drywall

0.2

×

0.5

=

0.1

0.1

Mineral Wool

4.0

×

3.5

=

14

14

Cellulose

3.2

×

5.5

=

17.6

-

Wood Stud

1.1

×

5.5

=

-

6.05

Ext. Sheathing

1.3

×

0.5

=

0.65

0.65

Mineral Wool

4.0

×

3

=

12

12

=

0.17

0.17

Rse (Ext. Wall)

RPATH =

45.2

33.7

U PATH =

0.022 × 90.6% = 0.0200

0.030 × 9.4% = 0.0028

Area % = U weighted

+

Utotal

0.0228 (Btu/hr·ft2·°F)

R total

43.9(hr·ft2·°F/Btu)

Path 1

Path 2

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ASHRAE 2D Assembly U-Factor – Isothermal Plane

+

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ASHRAE 2D Assembly U-Factor – Isothermal Plane Isothermal Plane Method R-per-Inch

Thickness

(hr·ft2·°F/Btu)

(inches)

R-Value

Rsi (Int. Wall)

U-Value

Area%

Uweighted

Utotal

R-Value

0.68

0.68

Drywall

0.2

×

0.5

=

0.1

0.1

Mineral Wool

4.0

×

3.5

=

14

14

Cellulose

3.2

×

5.5

=

17.6

0.057 ×

90.6% =

Wood Stud

1.1

×

5.5

=

6.05

0.165 ×

9.4% =

Ext. Sheathing

1.3

×

0.5

=

0.65

0.65

Mineral Wool

4.0

×

3

=

12

12

0.17

0.17

Rse (Ext. Wall)

0.0515 + 0.0155

0.0670

14.92

R-Value

42.5

U-Value

0.0235

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So… Parallel Plane Method gives us a U-Value of 0.0228 Btu/hr-ft2-F Isothermal Plane Method gives us a U-Value of 0.0235 Btu/hr-ft2-F Which is right?

Neither. So we just take the average of the two methods.

0.0228 + 0.0235 / 2 = 0.0232 Btu/hr-ft2-F

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Example: PHPP Numerical Calculator

U-Value: 0.024 Btu/hr-ft2-F

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2 or 3-D Simulation For many assembly types (steel stud walls, complex assemblies) we will not be allowed to use a numerical calculation. We can then turn to 2D simulations in order to establish our clear field assembly U-Value.

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