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.EngRDH Building Sciences Inc. Vancouver, BC/Seattle, WA

Presentation Outline

What are “Super-Insulated” buildings and what are the drivers? Thermal bridging –problems and solutionsDesigning of highly insulated walls – insulation placement & durability considerationsSuper-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 SeattleOEESC 2010 – Oregon State

Energy codes in Pacific Northwest are some of most stringent but are also the best implemented in North AmericaBuilding enclosure (R-value/U-values) very important part of complianceEffective R-values considered

From Energy Codes to Super Insulation

Most Energy Codes now consider effective R-valuesNominal 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 wallsR-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 wallsR-40 to R-60+ effective for roofsR-6+ for windows

Other drivers – comfort, passive design, mold-freeWhat 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 ratioUse of exterior continuous insulation with thermally improved cladding attachmentsMinimizing 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 detailsAlso 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 efficiencyVarious 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 commonvs 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 componentThis 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 areaWindow 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 breaksStandard 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 strategyHow 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 insulationPolyiso – 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 temperatureHigher density equals lower R-valuesThis 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 resultsWhy 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 factorsSolid 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 techniquesHigher 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 drivenAirflow control/airtightness – energy code and building code drivenControl of condensation and vapor diffusion – building code drivenControl of exterior moisture/rainwater & detailing –building code drivenMore insulation = less heat flow to dry out moisture

Amount, type and placement of insulations mattersGreater need to more robust and better detailed assembliesPotentially 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 problemsVapor diffusion contributes but doesn’t cause most problems – unless within a sensitive assemblyMany windows leak and sub-sill drainage and flashings are critical, other details and interfaces also importantInsulation inboard of structural elements decreases temperatures which increases risk for moisture damageDurability of building materials is very importantWatch over-use of impermeable materials in wet locationsDrained & ventilated rainscreen walls & details work wellUnproven 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

Baseline2x6 w/ R-22 batts = R-16effective

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 usefulCladding attachment biggest source of thermal loss/bridgingExcellent 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 attachmentWall 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 typeCladding attachmentSequencing & 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 sheathingCareful 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 optionsLack 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 Clips5” (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 panel1” horizontal metal hat tracks3 ½” semi-rigid mineral fiber (R-14.7) between 3 ½” fiberglass clipsFluid applied vapor permeable WRB/Air barrier on gypsum sheathing6” mineral fiber batts (R-19) between 6” steel studsGypsum 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 airtightnessInherently 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-sealingRainwater 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 BuildingsProvides design and detailing guidance for highly insulated wood-frame wall & roof assembliesContains North American energy code guidance, building science fundamentalsInsulation placement, air barrier systems, cladding attachmentAvailable 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-2.8Exterior 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 paybackRetrofitted effective R-9.1 (super-insulated for a building of this type)55% reduction in air leakage measuredEnclosure 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 considerationsCladding attachment detailing – minimize loss of R-value of exterior insulationShifting 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