Implications for Building Envelope Design on the path toward Net Zero Performance

Implications for Building Envelope Design on the path toward Net Zero Performance FAÇADE+ MINNEAPOLIS, JULY 24TH 2019

Current Energy Codes Prescriptive Approach ! Lists system design requirements ! Minimum U-value requirements ! Satisfy preconceived, static, and broad notions for common and feasible construction practices

WINDOW U-VALUE OPAQUE U-VALUE GLAZING RATIO EQUIPMENT EFFICIENCY AIR-TIGHTNESS

Envelope Performance in Energy Codes CONVENTIONAL

PRESCRIPTIVE FOCUS + ASSEMBLY BASED + COMPARATIVE

EMERGING

PERFORMANCE BASED +ABSOLUTE TARGETS +THERMAL BRIDGE CALCULATIONS

• ASHRAE 90.1 • IECC

• BC Energy Step Code • Toronto TGS V3

Drive to Net-Zero Energy Codes NREL’s Best Practices for High-Performance Buildings ! Design the building envelope such that it can be used to meet as many loads as possible ! The envelope should be the first method of creating lowenergy buildings; the mechanical and lighting systems should then be sized to meet any remaining loads ! Low-energy architecture is not effective if mechanical systems have to solve problems that result from the envelope design

Drive to Net-Zero Energy Codes Absolute Performance Based ! Requires energy modelling ! Often backed up by monitoring of completed building Performance targets ! Overall !

EUI Whole Building Energy

! But also often Specific Performance targets ! !

TEDI: Space Conditioning Energy GHI: Green House Gas generated Energy

! All require comprehensive thermal transmittance calculations

What is EUI?

Energy Use Intensity Total Building Energy Per Unit Area

What is TEDI?

Thermal Energy Demand Intensity Total Space Conditioning Load Per Unit Area

Envelope Design Considerations

Strategies to optimize envelope

Strategy: Optimize Envelope Surface Area Key Concepts !  Optimize ratio of envelope to floor area to reduce potential for heat loss !  Minimize extent of interfaces to reduce the impact of thermal bridges

Credit: Integral Group, 2017

Strategy: Optimize Solar Exposure Key Concepts !  Optimize glazing orientation and shading to control solar heat gain !  Use glass coating to further limit solar heat gain

Strategy: Optimize Fenestration Key Concepts !  Optimize Glazing to Wall ratio with a focus on maximizing daylighting

Credit: Integral Group, 2017

Strategy: Optimize Fenestration Key Concepts !  Optimize alignment of the glazing and the thermal barrier to minimize thermal bridging

Strategy: Optimize Fenestration Key Concepts !  Optimize glass to frame ratio my using larger glazing units !  Optimize the glazing interface to minimize thermal bridge

Strategy: Optimize Fenestration Key Concepts !  Consider high performance glazing systems to optimize fenestration

Strategy: Improve Air Tightness Key Concepts ! Establish air tightness goals early ! Plane of air barrier clearly identified on drawings

Δ10

Strategy: Optimize Envelope Thermal Performance Key Concepts ! Poor interface details undermine effectiveness of increased insulation

IP (BTU/ hr·ftoF)

0.47

Additional Contribution to Space Heating Energy (GJ/ m2 of Floor Area)

! Minimize thermal bridging to improve thermal performance Clear Wall Only

0.14

Including Poor Details

IP (BTU/

0.12

hr·ftoF)

0.1

0.34 More Insulation is not the silver bullet

0.08 0.06 0.04

IP (BTU/ hr·ftoF)

0.02

0.12

0 No

ula r Ins o i r e t Ex

tion

inal R Nom

-5

ula r Ins o i r e t Ex

tion

xterio

Nom

in

15 E al R-

r

xterio

in

Nom

25 E al R-

r

Strategy: Optimize Envelope Thermal Performance Key Concepts !  Optimize insulation performance of envelope assemblies !  Minimize thermal bridging at structural supports and interfaces

Assembly Clear Field U-values

Interface Linear Transmittances

Strategy: Optimize Envelope Thermal Performance ! Net Zero Ready is difficult Without High Thermal Quality Details Key Concepts ! Small differences in detailing can be significant ! The wall to window interface demands the greatest attention because of the potential variation in values and overall impact

Strategy: Optimize Envelope Thermal Performance Structural Support: Some Easy and Efficient Designs are Non-Starters Key Concepts ! More complex connections ! More considerations for ! Cladding attachments with combustible components ! Thermal breaks ! Continuity of the thermal insulation across the structure ! Windows positioned outboard of the structure

Strategy: Consider New Technologies

Resources

Visualizing the performance of envelope strategies

Energy Modeling is Key to Performance Key Concepts !  Early Involvement is Key !  Interactive Parametric studies allow design teams to rapidly explore multiple design factors and assess their interaction and impacts on outcomes

Net Zero Energy Resources

Drive to net Zero - Evolution of the BETB Guide ! Low TEDI Guide provides guidance and details for Net Zero (Ready) and Passive House ! Part 3 Buildings ! Details to be included in the next version of BETB Guide ! Continue to expand the BETB catalogue/ database for more construction types, climates, and practice

Performance Expectations Revised for Higher Thermal Quality Details !  Small differences can be significant for Low TEDI Buildings !  The wall to window interface demands the greatest attention

Optimize Interfaces: Window Transition

R-10

R-11

Catalog Breakdown Appendix B ! Organized by construction and transmittance type ! Detail description ! Thermal image ! Legend ! Transmittances ! Temperature Index

Thermal.ly Catalog

Summary

The Path Forward

Summary ! It is becoming increasingly difficult to ignore impact of envelope performance ! Move beyond simply adding “more insulation” ! Better able to account for thermal performance of building envelope