nnca construction workshop 2016-02-17 wall design for north...loads, gravity control ... optimal...

NNCA Construction Workshop 2016-02-17

G.Finch - RDH 1

Optimal High R-value Wall Designs for the Far North – Balancing the Science & Practice

NNCA RESIDENTIAL CONSTRUCTION WORKSHOP, YELLOWKNIFE – FEB 17, 2016

GRAHAM FINCH, MASC, P.ENG – PRINCIPAL & BUILDING SCIENCE RESEARCH SPECIALIST

[email protected] – 604-873-1181

Presentation Outline

� Northern Building & Energy

Code Requirements & Local Wall

Designs

� Building Science Considerations

for Higher R-value Wall

Assemblies

� Optimal Wall Study - R-40 Wall

Evaluation

� Thermal Performance

� Hygrothermal Durability

� Constructability, Cost, &

Resource Efficiency


G.Finch - RDH 2

Building Science Challenges in the North

� The North is the most challenging environment

to construct, operate & maintain a building

� Extreme cold requires super-insulated enclosure

assemblies, minimal thermal bridging and near-

perfect air-sealing

� HVAC systems must be reliable, easy to operate

and have redundancy

� Snow, ice, wind, permafrost all add further

unique building design considerations

� Indoor humidity & providing adequate ventilation

is often a challenge (and even more so as we

build more airtight) – Topic of Day 2

� Not all building materials are readily available

here

� Not all materials can be applied, work as well or

hold-up in the extreme cold

Building & Energy Code Drivers in the North

� 2010 National Building Code

(Plus 2012 Part 9.36 Energy Efficiency

Requirements)

� NECB 2011 (Replaced old MNECB 1997)

� Municipal Bylaws & Territorial

Guidelines have additional/modified

enclosure requirements

� In all cases - emphasis is placed on well

insulated, air-tight and thermal bridge

free building enclosures

� General shift in mind-set from nominal

(insulation only) to effective R-values


G.Finch - RDH 3

� Nominal R-values = Rated R-values

of insulation which do not include

impacts of how they are installed

� For example R-20 batt insulation or

R-10 rigid insulation boards

� Effective R-values or Real R-values

= Calculated R-values of

assemblies/details which the

include impacts of installation and

thermal bridges (studs, girts etc)

� For example nominal R-20 batts

within 2x6 steel studs 16” o.c.

becoming ~R-9 effective, or in

wood studs ~R-15

Nominal vs Effective R-values of Insulation

Minimum Code R-values – Canada’s North

All Values for most extreme Climate Zone 8 (>7000 HDD incl. NT, NU, & most YT)

Effective R-values (includes impact of thermal bridging)

Building/Energy CodeRequirement –Climate Zone 8

Walls: Minimum R-value (IP)

Roofs –Compact or

Attic: Minimum R-value (IP)

Floors -suspended: Minimum R-value (IP)

NBC 2010 (2012 Part9.36) – Part 9 Buildings

21.9 (17.5 if HRV

installed)

28.5 (flat)59.2 (attic)

28.5

NECB 2011 –Part 3 Buildings

31.0 40.0 40.0


G.Finch - RDH 4

Beyond Minimum Code R-values – Far North

Guideline, Bylawor Green Standard

Walls: Minimum R-value (IP)

Roof – Ceiling below Attic: Minimum R-

value (IP)

Floor (suspended): Minimum R-value (IP)

Nunavut – Good Building Practices, 2005

R-28 (nominal)

R-40 (nominal)

R-40(nominal)

NWT – Good Building Practices, 2011

R-32 (nominal)

R-50 (nominal)

R-40(nominal)

Yellowknife –Existing Buildings

R-30(nominal)

R-40 (nominal)

R-30(nominal)

Yukon Housing Corporation

R-28 WhitehorseR-21.9 elsewhere

(effective)R-59 (effective)

R-28.5 (effective)

General Passive House Guidelines

R-60 to R-80+ (effective)

R-60 to R-100+(effective)

R-40 to R-60+ (effective)

Note: Several Documents Refer to Nominal Insulation R-values not Effective

Residential Wall Design Preferences to Meet R-28 to R-30 Nominal Target in the Far North

� R-22 fiberglass batts + R-6 semi-rigid mineral wool

interior (R-30 nominal) w/24” stud spacing ~R-22

effective

� Poly VB/AB, Housewrap WRB/(AB?)


G.Finch - RDH 5

Many Other Wall Designs Being Built - Yukon

R-36 effective R-40 effective

From Craig Olsen & Lysann Grundlich “Breaking Down Barriers to Building SuperGreen”


EPS/MW FG/EPS/FG ccSPF/PIC/MW ocSPF/MW

R-36 effective

EPS/EPS/MW


EPS/MW SIPS/MW

ocSPF/MW

R-51 effective R-56 effective R-53 effective

CFI/MW

MW/ccSPF/FG

Making the Leap to Higher R-values (R-40+)

Base 2x6 Framed Wall ~R-16

Exterior InsulationR-20 to R-60+

Deep Stud, Double Stud, SIPSR-20 –R-80+

Split Insulation R-20 to R-80+

Interior InsulationR-20 to R-30+


G.Finch - RDH 6

How to Evaluate Different Wall Designs?

High R-value Wall Assembly Design & Detailing –Choices for Control Functions

(WSS)

(WRB)

(AB)

(VR/VB)

(Insulating Materials)


G.Finch - RDH 7

Rainscreen Claddings (Water Shedding Surface)

� For highly insulated walls suggest

drained & ventilated cavity

behind cladding (i.e. Rainscreen)

� Helps facilitate drying of wall &

cladding and reduce capillary or

vapour transfer of moisture to

back-up wall

� Vertical strapping (furring), girts

or other materials to create the

gap

� Select appropriate material

suitable for north (i.e. metal,

wood, fiber cement)

� Cladding attached to vertical

strapping

The Water Resistive Barrier (WRB)

� Often referred to as the “sheathing

membrane”

� Required in all walls – is the 2nd

plane of protection & innermost

plane that can safely manage

moisture and drain/dry it back out

� Many different products available

(mechanically fastened, self-

adhered, & liquid applied)

� Many products can also be

taped/sealed/applied as air barrier

� Vapour permeable & impermeable

products available – choice depends

on insulation placement etc.


G.Finch - RDH 8

Thermal Control - Insulation

� Many different types of

insulation products

� Low density batts

� Loose fill (blown/spray)

� Semi-rigid or rigid boards

� Spray-applied foam

� New materials like VIPs,

aerogels

� Key properties to consider:

� Conductivity (R-value)

� Air permeability

� Vapour permeability

� Density & application

Insulation R-values

� Recent research has re-highlighted the fact that the R-

value of insulation is not always constant (or as

published)

� Aged R-values (Long-term Thermal Resistance)

� Temperature Dependant R-values


G.Finch - RDH 9

Varying Insulation R-value with Temperature

It Gets Even More Complicated with Polyiso

0.048

0.041

0.036

0.032

0.029

0.026

0.024

0.022

0.021

-4 14 32 50 68 86 104 122

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

-20 -10 0 10 20 30 40 50

Temperature [°F]

Co

nd

uct

ivit

y,

k [

W/(

m·K

)]

R-V

alu

e p

er

Inch

[(h

r·ft

²·°F

/Btu

)/in

]

Temperature [°C]

Temperature Dependence of Polyiso Thermal Performance

01 (1995 to 1996) 02 (1995 to 1996) 03 (1999)

04 (2006) 05 (2006) 06 (2006)

07 (2007 to 2009) 08 (2009) 09 (2009)

10 (2012) 11 (2012) 12a (2012)

12b (2012)


G.Finch - RDH 10

Vapour Retarders / Barriers

� Vapour Retarders / Barriers

control the diffusion of vapour

through an assembly

� Limit wetting (condensation)

� At the same time we need to

allow for some drying

� Many materials act as vapour

retarders even if unintended

� In Far North – vapour control on

warm side of insulation*

� Gets more complicated with

exterior/split insulated

assemblies & with vapour

impermeable insulation

Design for Vapour Diffusion Drying Ability

� Watch over-use of impermeable materials over damp materials or materials that could get wet in-service

� Self adhered membranes

� Foam plastic insulation

� Vapor diffusion wetting & drying ability for assemblies & details should always be assessed at design stage

� In the north – especially for northern facing walls – very limited potential for vapour diffusion drying


G.Finch - RDH 11

Air Barrier Systems

� Air Barriers are Systems – always

more than one material/component

� Details are the most critical part

� 5 Requirements of an effective

Air Barrier System

� Air-impermeable

� Continuous

� Structurally Adequate

� Sufficiently Rigid (or supported)

� Durable

� Plus: Must not negatively restrict

vapour diffusion drying ability

Air Barriers Are Systems

AccessoriesMaterials Components

Whole Building

Airtightness


G.Finch - RDH 12

Different Wall Air Barrier Systems

� Preference depends on a variety of factors including enclosure design & builder familiarity with system

� Common Air Barrier Systems

� Sealed polyethylene (mastic & tapes)

� Airtight drywall (drywall/gaskets/sealant)

� Taped & sealed mechanically attached sheathing membranes

� Self-adhered or liquidapplied sheathing membranes

� Sealed Sheathing (sealants/tapes at Joints)

� Spray Polyurethane Foam (sealants at interfaces)

Robust Wall Air Barrier Systems for the North


G.Finch - RDH 13

Interior vs Exterior Air Barrier with Cavity Walls

� Industry shift away from the use of interior air barrier approaches (poly,

drywall) to favouring exterior sheathing approaches (sheathing

membranes, sheathings) as the primary air barrier element

� BUT! still need to maintain a reasonable degree of airtightness at interior

side of fibrous cavity insulation (convection suppressor) – especially in

the Far North

� Vapor barrier/retarder at interior side depending on insulation ratio

Primary Air Barrier System

Secondary Airtight element

With enough exterior insulation – risk for condensation at sheathing decreases as does need for interior air tightness

Optimal Design for High R-value Wall Assemblies in Northern Canada


G.Finch - RDH 14

Optimal Northern Wall Design Prerequisites

� Walls are subject to extreme cold, intense

winds and unique solar exposure, therefore

walls must be able to:

� Support structural loads: wind & lateral

loads, gravity

� Control environmental loads:

› Moisture - precipitation, blowing snow, air

leakage condensation, indoor water vapour

› Air – continuous air barrier system to

minimize heat loss and control condensation

› Heat –sufficient thermal resistance to

minimize losses & gains

› Noise & fire – by using appropriate materials

� Finish: Durable finish resistant to exterior

and interior impact loads/use

� Be affordable, simple to build & maintain,

be minimal weight/volume for shipping

Optimal Northern Wall Design Considerations

� Durability & Longevity

� Material & Labour Cost

� Material Availability

� Ease of Construction

� Pre-fabrication vs Site-Built

� Thickness

� Weight (shipping and/or site handling)

� Environmental aspects (material choice)

� Air Barrier System & Detailing

� Water & Vapour control (wetting & drying)

� Cladding Attachment, Finishes


G.Finch - RDH 15

Optimal Wall Research - Why R-40 Wall Target?

� Work by NRCan/CMHC has identified a target of R-40

effective for walls as it is cost, energy & resource

optimal for Northern Canadian housing archetypes

� Current minimum code targets in North are in the R-20

to R-30 effective range (and climbing) so future target?

� Many builders already constructing R-30 to R-60 walls

as part of more energy efficient home designs

� For optimization study here was a good baseline target

to strive for

� R-40 is easily scalable up (e.g. R-60+) or down

(e.g. R-30) by simply varying the thickness of

insulation layers

Primary R-40 Wall Types & Insulation Variations

Interior Insulated(Double/Deep

Stud Cavity Insulated)

Exterior Insulated

Split Insulated (Exterior & Stud

Cavity)

Insulated Structures (SIPs)


G.Finch - RDH 16

Interior Insulated – Deep/Double Stud Walls

� Water Control:

� Drained/ventilated rainscreen cladding

with synthetic housewrap WRB

� Vapour Diffusion Control:

� Sealed polyethylene at interior

� Air Control*:

� Caulked and taped poly at interior,

sealed housewrap at exterior or sealed

plywood at exterior. Alternate –

sprayfoam between studs or secondary

interior service wall

� Cost/Constructability:

� SPF/blown cellulose requires special

equipment & training

� Double framed wall requires extra labour

Structurally Insulated Panels - SIPs

� Water Control:

� Drained/ventilated rainscreen

cladding with synthetic housewrap

WRB


� OSB interior skin/EPS core

� Air Control*:

� Sealed OSB joints and EPS foam at

interior & exterior

� Cost/Constructability*:

� Expensive material, though less

labour and prefabrication speeds

up construction

� Requires specialized training and

local crane/lifting equipment


G.Finch - RDH 17

Exterior Insulated

� Water Control:

� Drained/ventilated rainscreen

cladding with synthetic housewrap

WRB & surface of exterior insulation


� Plywood sheathing and/or sheathing

membrane

� Air Control:

� Taped & sealed plywood or sealed

sheathing membrane


� Rigid insulation is expensive (high

shipping and labour handling costs)

� Thicker insulation results in unique

wall penetration details & cladding

attachments

Split Insulated

� Water Control:

� Drained/ventilated rainscreen cladding

with synthetic housewrap WRB & surface

of exterior insulation


� Poly/VB paint or plywood sheathing

� Air Control:

� Taped & sealed plywood or sealed

sheathing membrane


� Rigid insulation is expensive (high

shipping and labour handling costs),

though less than all exterior insulated

� Thicker insulation results in unique wall

penetration details & cladding

attachments


G.Finch - RDH 18

How Much Insulation to get to R-40 Effective Under Northern Design Conditions?

NOMINAL AND TEMPERATURE-DEPENDANT THERMAL CONDUCTIVITIES FOR SELECT INSULATION MATERIALS

Insulation TypeNominal (24°C)

(R-value/inch)

Cold Temperature (-20°C)

(R-value/inch)

Extruded polystyrene (EPS) R-5 R-6.3

Expanded polystyrene (XPS) R-4 R-4.9

½ pcf Open-cell Spray Polyurethane Foam (ocSPF)

R-3.6 R-4.5

2 pcf Closed-cell Spray Polyurethane Foam (ccSPF)

R-6 R-7.1

Polyisocyanurate (PIC) R-6? R-3.5?

Semi-Rigid Mineral Fibre (MW) R-4 R-5.2

Dense-pack (4 pcf) Cellulose Fibre Insulation (CFI)

R-3.6 R-4.3

Fibreglass Batt Insulation (FG) R-3.6 R-4

Current test data for temperature dependent R-values only goes down as low as -20C.

Insulation Variables – Exterior Insulated

6.5” Extruded polystyrene (XPS)

R-34 R-42

8” Expanded polystyrene (EPS)

R-34 R-41

7.5” Rigid mineral fiber (MFI)

R-32 R-41

9” Polyiso (PIC) R-56 R-41

Effective R-value @ Standard 24°C

Effective R-value @ Cold -20°C


G.Finch - RDH 19

Safe Insulation Ratio for Split Insulated Walls?

RATIO OF EXTERIOR TO TOTAL INSULATION NOMINAL*R-VALUE TO CONTROL AIR LEAKAGE CONDENSATION RISK

Indoor RH20% 30% 40% 50% 60%

Toutdoor (°C)

0 0 0.12 0.32 0.47 0.60

-10 0.23 0.40 0.54 0.64 0.73

-20 0.41 0.55 0.65 0.73 0.80

-30 0.53 0.64 0.72 0.78 0.84

-40 0.66 0.70 0.76 0.82 0.86

*prudent to assess w/ temperature dependent insulation R-value

Insulation Variables – Split Insulated 2x4

5” Extruded polystyrene (XPS) & R-13 batt (FG)

R-37 R-43

6.5” Expanded polystyrene (EPS) & R-13 batt (FG)

R-38 R-43

6” Rigid mineral fiber (MFI) & R-13 batt (FG)

R-36 R-43

7” Polyiso (PIC) & R-13 batt (FG)

R-54 R-42




G.Finch - RDH 20

Insulation Variables – Split Insulated 2x6 (R-65+)

8” Extruded polystyrene (XPS) & R-21 Batt (FG)

R-57 R-67

10” Expanded polystyrene (EPS) & R-21 Batt (FG)

R-57 R-66

9.5” Rigid mineral fiber (MFI) & R-21 Batt (FG)

R-55 R-66

11.5” Polyiso (PIC) & R-21 Batt (FG)

R-86 R-67



Insulation Variables – Double Stud Walls/SIPs

13.5” Dense-packed (4pcf) cellulose (CFI), 6.5” gap between 2x4s

R-38 R-41

13” Open-cell ½ pcfsprayfoam (ocSPF), 6” gap between 2x4s

R-37 R-40

5” Closed-cell 2 pcfsprayfoam (ccSPF) and 7” Dense-packed (4pcf) cellulose (CFI), 5” gap between 2x4s

R-38 R-40

8” EPS SIPs R-32 R-40




G.Finch - RDH 21

Wall Thickness vs Effective R-value – R-40 walls

8

9

10

11

12

13

14

15

16

28

30

32

34

36

38

40

42

44

Wa

ll T

hic

kn

ess

(in

che

s)

R-v

alu

e a

t -2

0°C

Total Wall Thickness (without Cladding) and Effective R-value at -20°C - Sorted by Thickness

Hygrothermal Assessment

� Hygrothermal modeling (WUFI)

performed for each wall

assembly using weather files

for 4 representative northern

territory cities

� Wall modeled under “normal”

residential operating

conditions and also a realistic

scenario when wall exposed to

interior air leakage (from

defect in air-barrier)

� Compared to baseline 2x6+

northern wall assembly as a

control


G.Finch - RDH 22

Yellowknife Hygrothermal Assessment – Normal Conditions

0

2

4

6

8

10

12

14

16

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

Sh

ea

thin

g M

ois

ture

Co

nte

nt

(%)

Control Double-Stud Cellulose

Exterior Insulated with XPS Split Insulated with XPS

All walls will perform adequately under normal operating conditions and perfect air tightness, well below 20% MC

Yellowknife Hygrothermal Assessment – with Incidental Air Leakage

0

10

20

30

40

50

60

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

She

ath

ing

Mo

istu

re C

on

ten

t (%

)

Double-Stud Cellulose Double-Stud Cellulose + Air Leak

Split Insulated with XPS Split Insulated with XPS + Air Leak

Deep stud insulated walls with cellulose or fiberglass are high risk from any small air leaks–ocSPF or ccSPF flash-and-fill help reduce this risk


G.Finch - RDH 23

Hygrothermal Modeling Summary

HYGROTHERMAL DURABILITY SUMMARY

Wall Wall IDHygrothermal Assessment

Notes

C Control Risky Fails by air leakage

1 D-CFI Risky Fails by air leakage

2 D-ocSPF PassSpray foam insulation functions as

the air barrier and protects the sheathing from direct air leakage.

3 D-ccSPF PassSpray foam insulation functions as

the air barrier and protects the sheathing from direct air leakage.

4 SIPS PassLocations for air leakage decay are

at the joints between panels.

5 S4-EPS Pass Sheathing is above the dewpoint.

6 S4-XPS Pass Sheathing is above the dewpoint.

7 S4-MFI Pass Sheathing is above the dewpoint.

8 S4-PIC Pass Sheathing is above the dewpoint.

9 X-EPS Pass Sheathing is above the dewpoint.

10 X-XPS Pass Sheathing is above the dewpoint.

11 X-MFI Pass Sheathing is above the dewpoint.

12 X-PIC Pass Sheathing is above the dewpoint.

Materials & Resource Efficiency

� Weights and volumes calculated for

all materials within each wall

assembly from drywall to

rainscreen strapping (no cladding)

� Compression factors/weights

included for each of the insulation

types

� Shipping of materials to different

regions estimated from local

contacts (including crating based

on volume & weight limits)

� Construction costing analysis then

performed with local shipping,

material and labour rates


G.Finch - RDH 24

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

2

4

6

8

10

12

14

Ship

pin

g V

olu

me

(cu

bic

fe

et

pe

r sq

.ft

of

wa

ll)

Sh

ipp

ing

We

igh

t (l

b/s

q.f

t o

f w

all

are

a)

Shipping Weights and Volume Comparison

Not including cladding

$0.00

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

Sh

ipp

ing

Co

st -

$/s

qft

of

Fin

ish

ed

Wa

ll A

rea

Relative Shipping Cost to Remote Regions – Resolute, NT

Not including cladding

Sprayfoam (liquid in drums) takes up little space to ship vs other insulations BUT is expensive to install once there


G.Finch - RDH 25

$0

$5

$10

$15

$20

$25To

tal C

on

sru

ctio

n C

ost

pe

r sq

.ft

of

FIn

ish

ed

Wa

ll

Labour

Material

Labour & Material Costs – Yellowknife

$0

$10

$20

$30

$40

$50

$60

Tota

l C

on

sru

ctio

n C

ost

pe

r sq

.ft

of

FIn

ish

ed

Wa

ll

Shipping Labour Material

Labour, Material and Shipping Costs - Resolute


G.Finch - RDH 26

Labour, Material and Shipping Costs – NT, NU, YT

$-

$5

$10

$15

$20

$25

$30

$35

$40

$45

$50

Tota

l Wa

ll C

on

stru

ctio

n C

ost

pe

r sq

.ft

of

Fin

ish

ed

Wa

ll

Resolute Bay Yellowknife Whitehorse

Cost Per Effective R-value – NT, NU, YT

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

Co

st f

or

Wa

ll p

er

Eff

ect

ive

R-v

alu

e a

t -2

0°C

Resolute Bay Yellowknife Whitehorse


G.Finch - RDH 27

Final Comparison & Weighted Score

NORTHERN R-40 WALL ASSEMBLIES SCORE CARD

Wall Wall IDHygrothermal Assessment

Thermal Efficiency (10

is best)

Construct-ability

Cost (10 is

lowest)

Weighted Score

1 D-CFI Risky 8 Moderate 9 22

2 D-ocSPF Pass 9 Poor 4 15.5

3 D-ccSPF Pass 6 Poor 5 13.5

4 SIPS Pass 10 Specialized 7 22

5 S4-EPS Pass 9 Excellent 10 27

6 S4-XPS Pass 9 Excellent 9 27

7 S4-MFI Pass 9 Excellent 8 25

8 S4-PIC Pass 6 Good 7 20

9 X-EPS Pass 10 Good 7 25

10 X-XPS Pass 10 Good 8 24

11 X-MFI Pass 10 Good 8 23

12 X-PIC Pass 7 Good 6 19

Optimal R-40 Wall Design for the North

- XPS and EPS insulation best choices for new construction- Rigid mineral wool close 3rd

- With exterior insulation ratio above 70% discussed, no need for poly VB at interior (plywood & foam VB)- Airtight sheathing or sheathing membrane


G.Finch - RDH 28

Optimal Exterior Retrofit High R-value Wall Design for the North

- In retrofit situations, better practice is for vapour permeable exterior insulation (rigid mineral fiber) instead of foam to avoid dual VB & potential to trap moisture

And When You Can’t Decide Which – Both!


G.Finch - RDH 29

Case Study – R-40 Split Insulated Air-tight Pre-fabricated Passive House Walls

� rdh.com | buildingsciencelabs.com

Discussion + Questions

[email protected] – 604-873-1181