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5 WaysZero Ready Walls

Spring Training CampHidden Valley Resort, Huntsville ON | 2016.04.26

Chris Schumacher, B.Tech.(ArchSci), B.A.Sc.(CivEng), M.A.Sc.(BldgSci)

Principal, Senior Building Science Specialist

2

Requirements for Zero-Ready Walls

• Energy Efficient

• Affordable

• Buildable

• Durable

3

Approaches to Zero-Ready Walls

Deep Cavity

• Create a thick wall assembly and fill the cavity with insulation

• Double Stud Wall

• Truss Wall

• I-joist wall

• All insulation in the framed space!

Exterior Insulated

• Minimize framed assembly then add continuous exterior insulation

• Foam Board (XPS or PIR)

• Spray Foam (2pcf ccSPF)

• Semi-rigid mineral fiber (stonewool)

• Framing configuration and size for structure and utility distribution not insulation!

4

Deep Cavity vs. Exterior Insulated

( Straube and Smegal, 2009)

5

Deep Cavity Challenges

• Structural sheathing is at the coldest point in the assembly

• Cold = Higher RH

• Cold = Higher Moisture Content

• Cold = Greater Potential for Condensation

• Air tightness is paramount!

6

Exterior Insulation Challenges

• Cladding Support

• Window Support

• Trim Details

• Drainage Plane Location

• Integrating Drainage at Windows

• Rainwater control is paramount!

7

5 Zero Ready Walls(that could be adopted now)

• Deep Cavity

– Double Stud

– I-joist

• Exterior Insulation

– Polyisocyanruate (PIC)

– Extruded Polystyrene (XPS)

– Stonewool (e.g. Roxul)

8

Double Stud

I-JoistStud

R-43RSI 7.5

(installed)

R-36 RSI 6.4

(installed)

9

Polysio

XPS

Mineral Wool

R-38 RSI 6.6

(installed)

R-37 RSI 6.5

(installed)

R-37 RSI 6.5

(installed)

10

Wall Assembly – Thermal Details

• Average Nominal RSI of the High RSI walls was RSI 6.2

• I Joist Stud wall had highest calculated RSI through the stud• 2-D heat transfer simulation gives (RSI 4.7) for 241 mm stud• 286 mm I-Joist would be RSI 5.5 – significantly better than DS

Installed RSI

12

University of WaterlooField Exposure Study

Objective: to improve the understanding of the moisture-related durability performance of exterior insulated, high-R, wood-framed wall systems

Approach: Natural exposure field testing with additional (controlled) moisture exposure

Recognition: The bulk of this work was done by T. Trainor & M. Fox. Both are past M.A.Sc. Students and current RDH-BSL team members.Also, a special thanks is owed to NRCan for supporting this project.

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The BEG HutSto

new

ool

R-3

4

X P

SR

-35

P I

CR

-35

Datu

mR

-24

• Natural weather exposure• North and South elevations were used for testing

I-Jo

ist

R-3

9

Db

lStu

dR

-39

University of Waterloo

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Test Walls

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• Fibre-cement lap siding• ¾ “ (19 mm) strapping• SBPO WRB and air barrier• 7/16” (11 mm) OSB sheathing• 2” X 6” SPF framing- 24” O.C.• 6 mil poly vapour barrier• ½ “ (12.7 mm) gypsum wall board

R-24 (installed)

Conventional (Datum) Assembly

16

Deep Cavity AssembliesI-Joist Double Stud

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PIC XPS Stonewool

Exterior-Insulated Assemblies

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• Passive background performance evaluation

– Controlled indoor conditions 30-50% RH and 21° C

• Active testing to determine potential for wetting and drying

– Air Injection – constant flow rate of indoor air injected into cavity space to simulate air leakage

– Water injection test

Performance Evaluation

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Calibrated Air leak

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Air Injection Testing

• Energy Star air leakage limit = .02 l/s/m2 at 50 Pa

• Power Law: Q = C * (delta P)n (n=0.65, delta P = 4 Pa)

this was converted to an in-service air leakage rate of 0.2 l/s/m2

• Applying this to the area of the center bay (1.3 m2), results in a leakage rate of .26 l/s per test wall

• 30 CFH (.24 l/s) was used

22

Calibrated Rain Leak

• Location and distribution to simulate a window leak

• Manually inject 30 ml of water twice a day

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Testing Protocol

Phase 1- Baseline (as-built condition)

October 2012 to February 18th, 2012

Phase 2- Air Leak Testing

February 19th to April 9th

Phase 3- Drying

April 10th to June 4th

Phase 4- Rain Leak Testing

June 3rd to July 5th

Phase 5 – Drying

July 6th to October

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BASELINE RESULTS

So what actually happened?

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Sheathing Temperature: Cold Weather

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Sheathing Temperature: Cold Weather

Wall Datum - N PIC - N XPS-N RW - N Double - N

Average -7.7 -0.1 1.6 2.5 -8.9

Min. -16.3 -5.6 -3.7 -2.5 -17.7

St. Dev. 5.0 3.6 3.2 3.1 5.1

Coldest Week of the Year

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Effective R-Values at 3 Temperature Conditions

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

-15° C 3.5 30° C -15° C 3.5 30° C -15° C 3.5 30° C

PIC PIC PIC XPS XPS XPS RW RW RW

Eff

ecti

ve

R-V

alu

e

at 3 Exterior Temperatures

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RH at Inside of Sheathing

0

50

100

150

200

250

300

Dbl. Stud - S Datum - S PIC - S XPS - S RW - S Dbl. Stud - N Datum - N PIC - N XPS - N RW - N

Re

lati

ve

Hu

mid

ity

(R

H)

Peak and Average Cavity RH - No Air LeakagePeak and Average Sheathing RH – Baseline (No Air leakage)

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Condensation hours - RH sensors less reliable near 100% RH

• Stud Cavity RH/T sensor data

• Pw – Stud cavity RH/T data [partial vapour pressure in cavity]

• Pws – T-data at sheathing / plates [saturation vapour pressure]

Possible errors include sensor location, non-uniform moisture distribution in the cavity

t

RH

t

ASHRAE Fundamentals, 2009

Potential for Air Leakage Condensation

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Potential for Air Leakage Condensation

Percentage of hours that could be expected to see condensation(if there was air leakage)

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Moisture Content of Sheathing

Moisture Content: Lower Sheathing, North Elevation – Baseline (No Air leakage)

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Moisture Content Distribution

Double Stud Wall – Baseline (No Air Leakage)

Double Stud Wall (South)

Double Stud Wall (North)

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Moisture Content Distribution

I-Joist Wall – Baseline (No Air Leakage)

I-Joist Stud Wall (South)

I-Joist Stud Wall (North)

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OSB MC – Exterior Insulated South

PIC Wall (South)

XPS Wall (South)

StonewoolWall

(South)

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OSB MC – Exterior Insulated North

PIC Wall (North)

XPS Wall (North)

StonewoolWall

(North)

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AIR INJECTION RESULTS

What about measured Air Leakage?

37

L

M

L

L

Measured Moisture ContentAir Injection Wetting followed by Drying

Double Stud Wall (North)

I-Joist Stud Wall (North)

38

M

M

PIC Wall (North)

XPS Wall (North)

Stonewool Wall (North)

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Condensation Hours – Baseline Period

Condensation Hours – Air Injection Period

Condensation Hours – Drying Period

Datum Datum

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

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Condensation Potential-Change in M.C. Due to Air Injection

0 10 20 30

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Do

ub

le-

So

uth

Da

tum

-S

ou

thP

IC-

So

uth

XP

S-

So

uth

RW

-S

ou

th

0 10 20 30

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Bottom Plate

Lower OSB

Middle OSB

Upper OSB

Top Plate

Do

ub

le-

So

uth

Da

tum

-N

ort

hP

IC-

No

rth

XP

S-

No

rth

RW

-N

ort

h

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• Mould growth thresholds

• Moisture content and temperature

• Lower limit of 16% for onset (Temp>5°C)

• Lower limit of 20% for fast growth (Temp>10°C)

• Decay

• Wood below 20% MC - decay does not occur

• Above 26-28% MC decay initiated

• Decay continues until MC returns below 20%

ASHRAE, 2009; FPL, 2010; Straube, 2005; Wang et al., 2010

Potential Impact?

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Mould – Slow Growth (MC >16%, T > 5°C)

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

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Mould – Fast Growth (MC >20%, T > 10°C)

Decay risk

Total hours above 20% MC after exceeding 28% MC

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

DblS

I-JoistS

DatumS

PICS

XPSS

StnwoolS

DblN

I-JoistN

DatumN

PICN

XPSN

StnwoolN

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The Warming Effects of Air Leakage

-10.0

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

1/5 1/12 1/19 1/26 2/2 2/9 2/16 2/23 3/2 3/9 3/16 3/23 3/30 4/6 4/13 4/20 4/27 5/4 5/11

Te

mp

era

ture

(D

eg

. C

)

Date (D/M)

The Warming Effect of Exfiltrating Air

Actual Sheathing Temp.

Predicted Sheathing Temp.Air Injection Phase

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WATER INJECTION RESULTS

What if a Window Leaks?

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• Injected via tubing into the absorbent sheet on exterior of OSB [ 30 ml – twice daily ]

• 1st Interval – 300 ml

• 2nd Interval – 420 ml

Water Injection Test

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Deep Cavity

Exterior Insulated

Water Injection Test

Wett

ing 1

Wett

ing 2

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Drying Capacity

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

5/25 6/1 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10 8/17 8/24 8/31 9/7 9/14 9/21 9/28 10/5 10/12

Mo

istu

re C

on

ten

t (%

)

Date

Moisture Content of North Walls

Datum-N

PIC-N

XPS-N

RW-N

Double-N

Wetting mat

injections (1)

Wetting mat

injections (2)

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Drying Capacity

0.0

2000.0

4000.0

6000.0

8000.0

10000.0

12000.0

14000.0

16000.0

South North South North South North South North South North

Datum PIC XPS RW Double

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SUMMARY

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Zero Ready Wall Options

• University of Waterloo Study considered 5 Zero Ready Wall assemblies

• Design and construction use variations on techniques and materials common to current industry standard walls

• Field study to assess hygrothermal performance and potential durability

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Baseline

• Deep Walls showed elevated sheathing moisture contents in baselines condition

– Upper sheathing up to 17% and upper plate up to 24%

• All exterior insulated walls exhibited baseline sheathing moisture content similar to the datum wall

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Air Leakage

• Both Deep Walls showed an increased sensitivity to air leakage and a greater potential for condensation

• All exterior insulated walls studied showed a significant reduction in condensation potential due to air leakage

• Don’t underestimate the potentially greater moisture risk associated with tighter walls

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Rain Leakage

• The XPS and PIC walls showed a significant reduction in outward drying capacity, while the Stonewool wall was similar to non-exterior insulated walls

• For wetting at the structural sheathing layer, Deep Walls exhibited similar rain leakage response standard wall

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RDH Building Engineering Ltd. and Building Science Consulting and Labs Inc. have merged. Effective November 1, 2015,we are operating as one integrated firm. The merger brings two of the leading building science firms in North Americatogether to provide a combination of cutting-edge research with leading design and implementation capabilities. Theresult is a unique offering for our clients–an ability to explore new and innovative ideas based on science and ourpractical knowledge of what can be built. We are excited about the possibilities as we launch the new firm.

chris@buildingsciencelabs.comcschumacher@rdh.com

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