Thermal Performance of Mass Structures

Feb. 24, MONDAY BREAKOUT SESSION 2 , Apache III 2020 RESNET Building Performance Conference

Today’s Session

▰Introductions ▰Mass timber’s future ▰Mass timber’s past ▻ Maturing CLT industry ▻ Log building heritage ▻ Advancements via the ▻ ICC Standard European Union development ▻ Carbon Accreditation ▻ A closer look at ▻ Thermal Comfort building science ▻ The details that ▰Further Resources for Log matter Building

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Rob Pickett, RobPickett &Associates

Sponsored by the Log & Timber Sustainable Building activities Homes Council, NAHB ▰2007 – Earned NAHB’s ▰1977 – Joined Colorado Certified Green Log Homes; Log Homes Professional Designation Council (LHC) forms ▰2008-10 – Accredited ▰1981 – began working with Verifier for National Green the LHC on log grading Building Certifications ▰1993-2001 – LHC ▰2010 – Charter Member, Committee Chairs Build Green NH ▰2002 to present – technical ▰2013 - Earned NAHB’s consultant, ICC IS-Log Master Certified Green ▰Today – representing the Professional Designation LHC as part of the Mass Timber Alliance 3 2020 RESNET Building Performance Conference

Advancing Solid Wood

Introducing the Mass Timber Leadership Alliance ▰Log & Timber Homes Council (LTHC, https://loghomes.org/) ▻ Represents mostly milled, engineered systems ▰International Log Builders Association (IBLA, https://logassociation.org/) ▻ Represents many methods and systems ▰Great Lakes Log Crafters Association (GLLCA, http://www.gllca.org/) ▻ Represents handcrafters of the upper Midwest North America ▰BC Log & Timber Building Industry Association (BCLTBI, https://bclogandtimberbuilders.com/) ▻ Represents the British Columbia industry – timber frame, milled, handcrafted ▰Suppliers for all of the above

▰Cross-Laminated Timber Panel Producers 4 2020 RESNET Building Performance Conference The European Technology Platform for the Forest-based Sector

http://www.forestplatform.org/#!/

CEI-Bois in Brussels is the most important confederation for the European forest and forest products industry. The European Confederation of Industries represents 21 European and National organizations from 15 countries and is the institutional body backing the interests of the whole European industrial wood sector: more than 180.000 companies generating an annual turnover of 133 billion euros and employing 1 million workers in the EU. CEI-Bois is also a shareholder in the European Technology Platform (ETP) for the forest-based sector.

5 Log, Timber and Cabin Market Survey by Active Interest Research Media

Importance: • Life style •Comfort • Energy efficiency

49% of respondents own land and plan to build in the next year or two.

6 2020 RESNET Building Performance Conference What makes solid wood homes different?

▰Solid wood is an alternative to framed cavity walls, benefiting structural, thermal, and fire-resistive performance. ▰Mass timber home design & construction often integrates timber techniques. ▰All wood surfaces require the same maintenance to protect the wood from sun, wind, and water.

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Which is best?

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How do solid wood walls stack up?

Early life safety concerns… ▰Fire ratings were a challenge ▰Log grading programs Measuring energy conservation… established to enable better ▰Ok up through the 2006 IECC structural analysis in all climate zones ▰Log builders, like every other ▰With the 2009 IECC … builder, has learned to build ▻ Energy Star certified better. windows and doors ▻ Insulate foundation vs. ▰Call for an ICC Standard: A floor cavity need to educate and ▻ 5” log width in CZs 1-4 consistently distinguish log ▻ 7” log width in CZs 5-8 walls from conventional IRC ▰Through the 90’s, many builders construction and inspection certified homes with Energy Star 9 and met 5-star+ ratings. Photo courtesy of True North Log Homes ▰More use of energy ratings 2020 RESNET Building Performance Conference

Achieving Consensus – ICC400

ICC IS-Log Committee took 3 years to develop first publication in 2007 ▰302 Material Standards ▻ Grading, moisture content & design stress values; section properties, notching and boring, wood treatments and connections ▰303 Fire-Resistance ▻ Ratings Paths -- Prescriptive (min. 6” for 1- hr), Calculated, Tested ▰304 Provisions for Settling ▻ Based on log shape, moisture content, may vary from 0.5% to 6% ▰305 Thermal Envelope ▰Ch. 4 Structural Provisions – formatted similar to the Wood Frame Construction Manual 10 2020 RESNET Building Performance Conference

Collaboration with REScheck

▰Calculation methods from ICC400 verified and implemented in REScheck ▻ More detailed and tied to wood species ▰All log assemblies are considered mass walls for purposes of determining what required U-factor to apply ▰If any insulation is added, the 'zone qualified' mass wall U- factors will be considered.

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Achieving Consensus – ICC400

Following the ICC Standards Development Cycle, the next publication was in 2012 ▰Updates of existing sections ▰Significant changes ▻ 302.4 Roof overhangs ▻ 305.2 Thermal envelope procedure starts with IECC ▻ 305.3 change from R-Value to U-Factor in Table for opaque walls ▻ Table 305.3.1.2 as alternate to IECC TABLE N1102.1.2 (R402.1.2) ▻ 306 Infiltration ▻ Attention to detail, just like all other methods of construction 12 2020 RESNET Building Performance Conference

Achieving Consensus – ICC400

Following the ICC Standards Development Cycle, the next publication was in 2017 ▰Updates of existing sections ▻ Multiple refinements ▻ Roof overhangs moved to 306 Infiltration ▰Led to change in IECC SECTION R402 BUILDING THERMAL ENVELOPE R402.1 General (Prescriptive). The building thermal envelope Exceptions: 1. The following low-energy buildings… 1.1. Those with a peak design rate of energy usage less than 3.4 Btu/h • ft2 (10.7 W/m2) or 1.0 watt/ft2 of floor area for space-conditioning purposes. 1.2. Those that do not contain conditioned space. 2. Log homes designed in accordance with ICC 400. 13 2020 RESNET Building Performance Conference Building Science: 306.2 Moisture Protection

▰Bulk water management ▰Inspection is easy to ▻ Overhangs (306.2.5) determine what maintenance ▻ Control backsplash is required (306.2.4) ▰Water film – cohesive movement ▻ Coat the exterior ▰Capillary surfaces to promote ▰Air leakage & pressurization water runoff ▰Diffusion -- Solid wood is the ideal ▻ Coating must allow wall. vapor to pass thru Porous material allowing vapor to be ▻ Fill open checks (<1/8”) gained and lost with the environment in which it is exposed. Other than joinery methods, no cavity exists. 14 2020 RESNET Building Performance Conference Building Science: 305.3 Thermal Properties

▰Wall conduction ▰Solar and indoor radiation Flir camera readings, L-R – visual, ▰Convection conduction only, with blower door on (- 50PA) Courtesy of Peter Yost, Building-Wright

15 2020 RESNET Building Performance Conference Building Science: 306 Infiltration ▰EERE Air Leakage – 25- 40% of heat loss ▰Foundations ▰First floor assemblies ▰Upper walls – dormers, gable ends ▰Roof assemblies

16 Wood Movement

1. Moisture content at time of vs. seasoned ▻ Radial ▻ Tangential ▻ Longitudinal 2. Fastening schedule ▻ Green to dry ▻ Gasket compression 3. Environment ▻ Porous material will respond to climate 4. Grading 17 2020 RESNET Building Performance Conference

The Details That Matter

At bottom of wall …

18 2020 RESNET Building Performance Conference Where log joints are properly The Details That Matter sealed by a system that accommodates shrinking and settling, log walls will form an Load bearing effective air barrier.

Gap designed for compression of gasket

Drip edge with capillary break

First log sets over 1x

alignment plate sealed 19 to subfloor 2020 RESNET Building Performance Conference

The Details That Matter

Check seal at log corners…

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The Details That Matter The sill log must extend beyond the Around window sills… ends of the logs forming the opening.

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The Details That Matter

At sides… Jamb/buck to log ends

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The Details That Matter

Above wall openings… Settling gaps over doors and windows can vary from 1/2” to 6” depending on log style and moisture content. Flashing covering the outside provides backing for insulation over the buck.

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At an upper floor…

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At roof eave overhang…

25 The Details That Matter At gable ends/rake overhangs…

26 Graphics courtesy of Appalachian Log Structures Inc. The Details That Matter

At electrical outlets…

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At switch boxes…

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At intersecting frame walls…

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Next Steps in ICC400

▰Update Climate Zone map & data relating to equilibrium moisture content ▰Adjust the prescriptive table for insulation ▰Development of a new standard that levels where log walls will integrate are implemented ▻ Carbon sequestration ▰Address how ASTM ▻ LCA/Embodied energy tests need to be ▻ Thermal comfort conducted Needed to reflect what homeowners ▰Establish a section for have experienced. performance rating 30 2020 RESNET Building Performance Conference

Mass Timber

▰-laminated timber (NLT or nail-lam) -- a century-old construction method that is undergoing a design renaissance -- Found today in many historical buildings as well as in compelling new projects of all sizes, where its structural performance and design elegance come together to create inspiring spaces. ▰Cross-laminated timber (CLT) -- a wood panel system that is gaining in popularity in the U.S. after being widely adopted in Europe. CLT is the basis of the tall wood movement, as the material’s high strength, dimensional stability and rigidity allow it to be used in mid- and high-rise construction. ▰-laminated timber (DLT) -- common in Europe and gaining traction in the U.S. for its ease of use with computer-controlled (CNC) machinery and its all-wood composition. DLT is similar to NLT, replacing nails/screws with wood to join laminations.

31 https://info.thinkwood.com/clt-handbook 2020 RESNET Building Performance Conference

Mass Timber Benefits

▰Carbon sequestration ▰Building physics ▰Thermal inertia ▰Thermal comfort ▰Life-cycle Assessment (LCA) characteristics ▻ Global Warming Potential (GWP) ▻ Green-House Gas (GHG) Emissions ▻ Low-embodied energy ▻ Sustainable resources ▻ Rural employment 32 2020 RESNET Building Performance Conference

CLT in the ICC Codes

▰2018 IBC ▻ 2-hr fire rated 6” CLT walls with exterior protection ▻ 4” CLT floor panels ▻ 3” CLT roof panels ▰State code adoptions of CLT ▻ Oregon Washington Photos courtesy ▻ of ▻ Utah homebuilding.co .uk ▰2021 IBC – approval of 14 proposals Building thermal envelope performance remains untested. 33 2020 RESNET Building Performance Conference

Life Cycle Assessment on Log Walls LCA is already used internationally to evaluate buildings and is becoming more widely adopted in Europe.

In 2012, the BC Log & Timber Industries Association contracted with the Athena Institute to perform LCA analysis of the products of their members.

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Milled Log Wall LCA Comparisons

Milled log wall 450% 400% Milled Log Wall 350% OSB, Clay Brick 300% OSB, Vinyl 250% OSB, Cedar 200% , Brick 150% 100% Plywood, Vinyl 50% Plywood, Cedar 0% Average Steel Stud Global warming Fossil Energy

35 2020 RESNET Building Performance Conference Handcrafted Log Wall LCA Comparisons

Handcrafted log wall 450% 400% Handcrafted Logs 350% OSB, Clay Brick 300% OSB, Vinyl 250% OSB, Cedar 200% Plywood, Brick 150% 100% Plywood, Vinyl 50% Plywood, Cedar 0% Average Steel Stud Global warming Fossil energy

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Carbon Accreditation

▰Responding to a Carbon Tax? ▰What is the ideal Carbon Sequester Measurement ? ▻ CarbonPlus Calculator http://www.itreetools.org/carboncalculator/entry.cfm ▻ The i-Tree Harvest Carbon Calculator https://harvest.itreetools.org/ ▰Creating a tool to measure the benefits of solid wood

Dark green = national walls? Yellow = state Light green = scheduled 37 2020 RESNET Building Performance Conference NZ Wood Carbon (http://www.nzwood.co.nz/house-calculator/)

Example home with wood floors, solid wood walls providing structure and cladding, wood framed windows, long-run steel roofing, no garage. Based on the floor area of this house, an allowance is made for all the other materials – glass, gypsum wall and ceiling board, ceilings/soffits, door panels, floor coverings, electrical wiring and fittings, plumbing, etc.

38 2020 RESNET Building Performance Conference NZ Wood Carbon (http://www.nzwood.co.nz/house-calculator/)

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Project U-Cube

Dr. Carl Timo Manz ctmanz consulting inc. [email protected]

An international research project in building physics and thermodynamics. The assessment methodology for the dynamic measurement of thermal energy demand in thermodynamically optimized model cubes enables a much more precise energy demand projection. This projection can be complimented with actual weather data and climate zone applications; facilitating international adaptability. 40 2020 RESNET Building Performance Conference

Dr. Manz’s Field Test Cubes

IMT co-initiated U-Cube research facility near Frankfurt, Germany; in support of the University of Darmstadt and the University of Kaiserslautern. 18 cm Cross-Laminated-Timber (CLT) cubes monitoring the effective coefficient of conductivity 41 for mass wood walls. Cubes: 3.0 x 3.0 x 3.0 meters. Evidence Leading to Theory

Convection: This simulation shows how convection causes irregular distribution of thermal energy inside of the cube. Note: The inner surfaces are colder compared to the figure showing the thermal radiation heating system.

Radiation: This simulation shows that the radiation heater functions very well in warming up the inner surfaces of the room. Warm inner surfaces allow lower air temperatures to achieve the same level of comfort. This results in a significant reduction of the required heating energy. 42 2020 RESNET Building Performance Conference

Monitoring System

Work in progress inside of one of the U-Cubes. “U” or “U-Value” is the European form of the North American R-Value”. Here the effective or true “U-Value” is being measured, which results in the effective co-efficient of the thermal conductivity of mass wood under thermal comfort conditions. 162 temperature sensors monitor the temperature on the inner surfaces and in various gradients of the wall. Moisture sensors in the wall monitor the moisture contents to exclude any moisture build- up.

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Thermal Comfort

A very simplified explanation for the thermal comfort in mass wood buildings can be expressed by warm inner surfaces (walls, ceilings, etc. of wood), which enable the inhabitant to turn down the inner air temperature; yet maintaining the same level of ▰Thermal comfort defined by DIN thermal comfort. In the range EN 7730 and ASHRAE Standard 55 of 17° to 23°C (inner air temperature), every degree [k] ▰European DIN-Standard (DIN-SPEC is equivalent to roughly 7 % of 91420) overall heating energy demand. the methodological protocol © C.F. Møller Architects Photo regarding the dynamic by Nikolaj Jakobsen 44 measurement of thermal comfort. 2020 RESNET Building Performance Conference

Thermal Comfort

Oulo University study The significant difference between the calculated heating demands (red) to the actual consumption (blue) was assessed in 80 buildings in Finland.

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The Next Step in Dr. Manz’s Research

▰The Frankfurt U-Cubes provide sufficient ▰Proposed: Test 3m (10’) cubes data to support expanded testing in a cold climate environment ▰Mass walls are known to perform very well ▻ Code-compliant wood frame in warm climates. Testing in cold climates walls is needed. ▻ 7” CLT walls ▰Canadian carbon initiatives are providing impetus to support further testing. ▻ 6” milled log walls ▰Goals for further U-Cube testing: ▻ 8” milled log walls ▻ Strive for consensus acceptance ▻ 12” handcrafted log walls ▻ Accredited agency to document, verify and report results ▻ 7” CLT floor and roof panels ▻ Use results to modify energy conservation codes regarding mass walls. 46 2020 RESNET Building Performance Conference A New Effective and Validated Value for Thermal Performance

▰Create an effective value of thermal resistance of mass wood in a dynamic approach, applying thermal comfort and thermal inertia. ▰Verify test data to enable mass wood walls of common and well-established dimensions. ▰Develop a standard method for calculating the effective value of mass wood walls and integrate it with a whole- house performance rating system. Can RESNET support new dynamic testing and develop a standard that incorporates carbon and thermal comfort measures? 47 2020 RESNET Building Performance Conference

Further Log Wall Resources

▰Construction documents ▰The Illustrated Guide to ▻ Plans & details Log Home ▻ Construction Manual Construction: From Log ▰ILBA Construction Shell to Finished Home, Guidelines by Dalibor Houdek ▻ Effective Practices & Methods: For Handcrafted ▰Log Construction Log Home Construction Manual - Ultimate Guide To Building Log Homes, by Robert W. Chambers ▰The Peril of Log Building: Raising a Voice for Log Building for Future Generations, by Rob Pickett 48 2020 RESNET Building Performance Conference

Thank You!

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