May 21, 2013 – SEABEC - Zen and the Art of Building Enclosure Design

Super Insulated Building Enclosures – Balancing Energy, Durability, and Economics in the Pacific Northwest

!   Graham Finch, MASc, P.Eng RDH Building Sciences Inc. Vancouver, BC/Seattle, WA

Presentation Outline

!   What are “Super-Insulated” buildings and what are the drivers?

!   Thermal bridging – problems and solutions

!   Designing of highly insulated walls – insulation placement & durability considerations

!   Super-Insulated wood-frame building enclosure design guide

!   Energy codes outline minimum thermal performance criteria based on climate zone !  ASHRAE 90.1, IECC – US

!  WSEC 2012, SEC 2012– Washington State & City of Seattle

!  OEESC 2010 – Oregon State

!   Energy codes in Pacific Northwest are some of most stringent but are also the best implemented in North America

!   Building enclosure (R-value/U-values) very important part of compliance

!   Effective R-values considered

From Energy Codes to Super Insulation

!   Most Energy Codes now consider effective R-values

!   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 foam insulation

!   Effective R-values include impacts of insulation installation and thermal bridges !   For example nominal R-20 batts within

steel studs becoming ~R-9 effective, or in wood studs ~R-15 effective

Effective R-values

!   In Pacific Northwest - minimum energy code R-value targets generally in range of: !  R-15 to R-25 effective for walls

!  R-25 to R-50 effective for roofs

!  R-2 to R-4 for windows

!   Green or more energy efficient building programs including Passive House - R-value targets in range of: !  R-30 to R-50+ effective for walls

!  R-40 to R-60+ effective for roofs

!  R-6+ for windows

!   Other drivers – comfort, passive design, mold-free

!  What does Super Insulation mean?

From Energy Codes to Super-Insulation

Super Insulated?

12” EPS insulation boards (blocks?) R-54

Super Insulated?

8” XPS insulation below grade R-40

6” mineral fiber (stainless brick ties) over insulated 2x6 wood frame ~R-38

!   Good to have super insulated walls and roofs – but what about thermal bridges and poorly insulated windows?

Super Insulated?

!   Thermal bridging occurs when a more conductive material (e.g. metal, concrete, wood etc.) bypasses a less conductive material (insulation)

!   Minimizing thermal bridging is key to energy code compliance and an energy efficient building

!   Balance of good window performance and appropriate window to wall ratio

!   Use of exterior continuous insulation with thermally improved cladding attachments

!  Minimizing the big thermal bridges

!   Energy codes have historically focused on assembly R-values – however recently more attention is being placed on R-values of interfaces and details

!   Also impacts comfort, condensation, and mold

Energy Codes and Thermal Bridging – A Balancing Act

!   Whole building airtightness testing requirements in Seattle and Washington State building codes are driving improvements in energy efficiency

!   Various solutions to achieve higher degrees of airtightness

!   Target of 0.40 cfm/ft2 at 75 Pa is frequently being met – range of 0.10 to 0.20 cfm/ft2 possible with some solutions

Building and Energy Codes and Airtightness

!   Windows significantly influence overall building enclosure performance !   Think about what R-3

windows do within an R-20 wall – where is the balance?

!   Tend to see higher window to wall ratios in multi-family and commercial buildings

!   40% to 70%+ is common !   vs 15% to 30% in homes

!   Optimized area and tuned SHGC, windows can have a positive impact (passive design strategies)

Challenges to Energy Efficiency – Windows

Impact of Windows on Whole Building R-values

!   Concrete balconies, eyebrows and exposed slab edges are one of the most significant thermal bridges

!   Essentially ~R-1 component

!   This reduce overall effective R-value of the whole wall area by 40 to 60% (for something that is just a few % of the overall wall area)

!   Adding insulation to surrounding walls often can’t make up for the loss associated with the detail

Challenges to Energy Efficiency – Balcony & Exposed Slabs

!   Example of slab/balcony impact: !   Slab edge typically occupies ~8% of the

gross wall area (8” slab in 8’8” high wall)

!   Balconies may occupy 1-2% of the gross wall area

!  Window to wall ratio affects opaque wall area

Impact of Concrete Balconies and Exposed Slab Edges

Exposed  Slab  Edge  Percentage  for  Different  WWR  

100%  wall:  0%  windows  

60%  wall:  40%  windows  

50%  wall:  50%  windows  

40%  wall:  60%  windows  

20%  wall:  80%  windows  

8”  slab,  8’  floor  to  ceiling  

7.7%   12.8%   15.4%   19.2%   38.5%  Exposed  Slab  Edge  Percentage  for  Different  WWR  

100%  wall:  0%  windows  

60%  wall:  40%  windows  

50%  wall:  50%  windows  

40%  wall:  60%  windows  

20%  wall:  80%  windows  

8”  slab,  8’  floor  to  ceiling   7.7%   12.8%   15.4%   19.2%   38.5%  

!   Cast-in thermal breaks !  Standard in Europe – becoming

more available in North America

!   Pre-cast and discretely attached concrete balconies (bolt on)

Solutions for Balconies

!   Exterior insulation is only as good as the cladding attachment strategy

!   How to achieve continuous insulation performance?

!   Flashings and other details also important

Challenges to Energy Efficiency – Cladding Attachment

!  Many Possible Strategies – Wide Range of Performance

Cladding Attachment through Exterior Insulation

Effective R-values of Various Cladding Attachments

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Strategies: Thermally Improved Cladding Attachments

Strategies Wood-frame: Screws through Exterior Insulation

Longer cladding Fasteners directly through rigid insulation (up to 2” for light claddings)

Long screws through vertical strapping and rigid insulation creates truss (8”+) – short cladding fasteners into vertical strapping Rigid shear block type connection

through insulation, cladding to vertical strapping

!   Wide range of R-values marketed with polyisocyanurate (polyiso) and closed-cell (2 pcf) sprayfoam insulation

!   Polyiso – reports of R-5 up to R-7.5 !   Closed cell sprayfoam – reports of R-5 to 6.5

!   Both influenced by age (off-gassing of blowing gases, replaced with air makes worse with time)

!   R-value changes with temperature

!   Higher density equals lower R-values

!   This isn’t new science or information !   Real long-term thermal resistance (LTTR)

values for both products in the R-4.5 to R-5.5 range when you need them

Challenges to True Energy Efficiency – R-value Claims

Real Insulation R-values – Old Science

From: Canadian Building Digest #149, 1972

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Room Temperature

!   Wide range of aluminum foil radiant barrier products on market (paints too)

!   Varying marketing claims – anything from R-1 all the way up to R-15+

!   Realistically may achieve R-1 to R-3 (very still air) if product faces a dead air cavity (ref. testing by many institutes)

!   Be very wary of false claims & suspicious test results

!   Why care? Often cheaper to use real insulation

Challenges to True Energy Efficiency – To Good to be True!

!   Wood-framed buildings generally provide good R-values, but… !   Taller wood-frame buildings – higher stud framing factors

!   Solid wood buildings – Cross Laminated Timber (CLT)

!   Where to insulate & air-seal - what assemblies to use?

New and Upcoming Challenges to Energy Efficiency?

!   Trend towards more highly insulated building enclosures due to higher energy code targets and uptake of passive design strategies !  Often means new enclosure assemblies (mainly walls) and

construction techniques

!  Higher R-value windows (triple glazing and less conductive window frames)

!  Reduction of thermal bridging, more structural analysis of façade components, balconies etc.

!  Super insulation achieved with proper balance!

!   Long-term performance of new assemblies (particularly wood frame) can be a challenge in our wet environment

Moving Towards Super Insulated Enclosures

!   Thermal insulation continuity & effectiveness – energy code driven

!   Airflow control/airtightness – energy code and building code driven

!   Control of condensation and vapor diffusion – building code driven

!   Control of exterior moisture/rainwater & detailing – building code driven

!  More insulation = less heat flow to dry out moisture !  Amount, type and placement of insulations matters

!  Greater need to more robust and better detailed assemblies

!  Potentially more sensitive to vapor, air & moisture issues

Energy Efficient Building Enclosure Design Fundamentals

What about the Pacific Northwest

!   Continue to repair moisture damaged buildings in the Pacific Northwest

Not Super Insulated.. Lower Risk But Still Failed

Definitely Not Super Insulated.. But Still Failed

“Super Insulated” Glazing Systems .. Failed

Systemic Failure of proprietary triple glazing units

!   Rainwater penetration causes most problems –poor details (e.g. lack of, poorly implemented, bad materials)

!   Air leakage condensation can cause problems

!   Vapor diffusion contributes but doesn’t cause most problems – unless within a sensitive assembly

!   Many windows leak and sub-sill drainage and flashings are critical, other details and interfaces also important

!   Insulation inboard of structural elements decreases temperatures which increases risk for moisture damage

!   Durability of building materials is very important

!   Watch over-use of impermeable materials in wet locations

!   Drained & ventilated rainscreen walls & details work well !   Unproven materials/systems can be risky

What Have We Learned from Past Enclosure Failures?

Insulation Placement and Assembly Design Considerations

Interior Insulation

Exterior Insulation

Split Insulation

Getting to Higher R-values – Placement of Insulation

Baseline 2x6 w/ R-22 batts = R-16 effective

Exterior Insulation – R-20 to R-40+ effective •  Constraints: cladding attachment, wall thickness •  Good for wood/steel/concrete

Deep/Double Stud– R-20 to R-40+ effective •  Constraints wall

thickness •  Good for wood,

wasted for steel

Split Insulation– R-20 to R-40+ effective •  Constraints: cladding

attachment •  Good for wood, palatable for

steel

New vs Retrofit Considerations

!   Insulation outboard of structure and control layers (air/vapor/water)

!   Thermal mass at interior where useful !   Cladding attachment biggest source of thermal loss/bridging

!   Excellent performance in all climate zones – But is not the panacea, can still mess it up

Exterior Insulated Walls

Steel Stud Concrete Heavy Timber (CLT)

!   Key Considerations: !   Cladding attachment

!  Wall thickness

!   Heat Control: Exterior insulation (any type)

!   Air Control: Membrane on exterior of structure

!   Vapor Control: Membrane on exterior of structure

!  Water Control: Rainscreen cladding, membrane on exterior of structure, surface of insulation

Key Considerations - Exterior Insulation Assemblies

Key Considerations - Split Insulation Assemblies

!   Key Considerations: !   Exterior insulation type

!   Cladding attachment

!   Sequencing & detailing

!   Heat Control: Exterior and stud space Insulation (designed)

!   Air Control: House-wrap adhered/sheet/liquid membrane on sheathing, sealants/tapes etc. Often vapor permeable

!   Vapor Control: Poly or VB paint at interior, plywood/OSB sheathing

!  Water Control: Rainscreen cladding, WRB membrane, surface of insulation

Split Insulation Assemblies – Exterior Insulation Selection

!   Rigid exterior foam insulations (XPS, EPS, Polyiso, closed cell SPF) are vapor impermeable (in thicknesses, 2”+) !   Is the vapor barrier on the wrong side?

!  Does the wall have two vapor barriers?

!  How much insulation should be put outside of the sheathing? – More is always better, but is there room? Cost?

!   Semi-rigid or rigid mineral or glass fiber insulations are vapor permeable and address these concerns

!   Vapor permeance properties of sheathing membrane (WRB)/air-barrier is also important

Split Insulation and Moisture Risk Assessment

Insulation Ratio Here is over 2/3 to the exterior of the sheathing Careful with lower ratios with foam

!   R-value design target up to R-25 for steel framed wall assembly. Energy modeling showed could trade-off a bit but no lower than R-18.2 (code)

!   6” steel stud frame wall structure (supported outboard of slab edge, and perimeter beams)

!   Expectation to be cost effective, buildable and minimize wall thickness

!   Tasked with the evaluation of a number of potential options

!   Lack of performance from standard practices helped innovate a new solution

Case Study: Bullitt Center – Split Insulation Wall Assembly

Bullitt Center – Exterior Wall Assembly Evaluation

Baseline: R-19 batts within 2x6 steel stud with exposed slab edges = R-6.4 effective Considered 2x8 and 2x10 studs - still less than R-8

Target R-value up to R-25

Vertical Z-Girts (16” oc) 5” (R-20) exterior insulation plus R-19 batts within 2x6 steel stud = R-11.0 effective

Horiz. Z-Girts (24” oc) 5” (R-20) exterior insulation plus R-19 batts within 2x6 steel stud = R-14.1 effective Crossing Z-girts also evaluated <R-16 effective

Intermittent Metal Clips 5” (R-20) exterior insulation plus R-19 batts within 2x6 steel stud = R-17.1 effective up to R-21 with some modifications

The Need to Go Higher – Reduce the Thermal Bridging

The Need to Go Higher – Reduce the Thermal Bridging

Intermittent Fiberglass Spacers, 3½” to 6” (R-14 to R-24) exterior insulation = R-19.1 to R-26.3 + effective

!   Metal panel

!   1” horizontal metal hat tracks !   3 ½” semi-rigid mineral fiber (R-14.7)

between 3 ½” fiberglass clips

!   Fluid applied vapor permeable WRB/Air barrier on gypsum sheathing

!   6” mineral fiber batts (R-19) between 6” steel studs

!   Gypsum drywall

!   Supported outboard slab edge (reduce thermal bridging)

!   Effective R-value R-26.6

Bullitt Center – Exterior Wall Assembly

!   Double 2x4/2x6 stud, single deep 2x10, 2x12, I-Joist etc.

!   Common wood-frame wall assembly in many passive houses (and prefabricated highly insulated walls)

!   Often add interior service wall – greater control over airtightness

!   Inherently at a higher risk for damage if sheathing gets wet (rainwater, air leakage, vapor diffusion) – due to more interior insulation

Double/Deep Stud Insulated Walls

Key Considerations – Double Stud/Deep Stud

!   Key Considerations: !   Air-sealing

!   Rainwater management/detailing

!   Heat Control: Double stud cavity fill insulation(s) – dense-pack cellulose, fiberglass, sprayfoam

!   Air Control: House-wrap/membrane on sheathing, poly, airtight drywall on interior, OSB/plywood at interior, tapes, sealants, sprayfoam. Airtightness on both sides good

!   Vapor Control: Poly, VB paint or OSB/plywood at interior

!  Water Control: Rainscreen cladding, WRB at house-wrap/membrane, flashings etc.

Deep/Double Stud and Moisture Risk Assessment

!   Guide to the Design of Energy Efficient Building Enclosures – for Wood Multi-Unit Residential Buildings

!   Provides design and detailing guidance for highly insulated wood-frame wall & roof assemblies

!   Contains North American energy code guidance, building science fundamentals

!   Insulation placement, air barrier systems, cladding attachment

!   Available as a free download direct from FP Innovations (google the title above)

Further Guidance on Highly Insulated Walls & Details

!   Deep energy retrofit of 1980s vintage concrete frame multi-unit residential building – owners decision to renew aesthetic (old concrete, leaky windows)

!   Original overall effective R-value R-2.8

!   Exterior insulate and over-clad existing exposed concrete walls (R-18 eff.)

!   Install new triple glazed fiberglass frame windows (R-6 eff.) – triple glazing incremental upgrade <5 year payback

!   Retrofitted effective R-9.1 (super-insulated for a building of this type)

!   55% reduction in air leakage measured

!   Enclosure improvements 20% overall savings (87% space-heating)

!   Actual savings being monitored – seeing higher than predicted savings

Final Thoughts – Super-Insulation Retrofit Case Study

!   Super-Insulated building enclosures require careful design and detailing to ensure durability !  Balancing materials, cost, and detailing considerations

!  Cladding attachment detailing – minimize loss of R-value of exterior insulation

!  Shifting insulation to the outside the structure improves performance and durability – balance is often cost

!   Super-Insulated buildings require balancing thermal performance of all components & airtightness !  No point super-insulating walls/roofs if you have large thermal

bridges or poor performing windows - address the weakest links first

!   Opportunities for both new and existing buildings

Final Thoughts – “The Art and Balance”

Questions

!   Graham Finch – gfinch@rdhbe.com

!   Highly Insulated Wood-frame Enclosure Guide – FP Innovations