HIGH PERFORMANCE INSULATED ROOFLINES
Mike Barcik, Southface Energy & Environmental Building Alliance
HELPING BUILDERS THRIVE SINCE 1982 EEBA has been a leading community resource for information and education on sustainable building for over 35 years. About EEBA 24 bottles in a case…24 hours Hmm, I wonder in a day!! what Mike’s been working on lately?!
3 ABOUT SOUTHFACE www.southface.org
Mike Barcik – Technical Principal [email protected]
Building a Regenerative Economy, Responsible Resource Use & Social Equity Through a Healthy Built Environment for All
4 MORE FREE TRAINING…
www.eeba.org 5 WHO ARE YOU?
• Weatherization • HERS Rater • Code official • Designer / Engineer • Contractor / Trades • Utility • Manufacturers / Product Rep • Policy / Government • Building Manager • Home Inspector
6 ENERGY CODE RESOURCES
Online educational resources are available by visiting: https://www.southface.org/education/online-training/
Technical assistance or training requests can be submitted to Georgia Energy Code Help Desk at: [email protected] or 404-604-3598
Additional Resources If you would like additional information on Georgia’s current energy code, please visit:
https://www.southface.org/resources/georgia-energy-code-resources/
Free: Commercial Field Guide, Pre-drywall Inspection video, webinars, tools, checklists, slide decks
Access the IECC and IRC codes at the ICC Digital Codes Library:
https://codes.iccsafe.org/
7 ASSESSMENT RESOURCE
8 WHY BUILDING SCIENCE? • Employ scientific principles from a variety of fields to design and optimize building performance and understand, prevent and correct building failures • Systems approach to houses • Physics of • Heat • Air • Moisture All efficiency measures should take occupants into account (e.g., air sealing & ventilation)
9 LEARNING OBJECTIVES
• Recall building science concepts • Apply knowledge of the building thermal envelope to home design • Interpret the energy code’s treatment of insulated rooflines • Choose best materials and methods for insulated and air sealing attic rooflines
10 Knowledge Check HEAT TRANSFER PROBLEM
Your Choices: 7 Radiation 1 Conduction Convection 2 6 1 → 2 = ______Radiation 3
2 → 3 = ______Conduction 4 3 → 4 = ______Radiation
5 → 6 → 7 = ______Convection 5
11 ATTIC HEAT TRANSFER
• 3 methods of heat transfer: ? ? • Radiation: Sun to shingles; underside of decking to other attic surfaces • Conduction: Through shingles and decking • Convection: Soffit vents through attic to ridge
12 Hmmm…
13 THERMAL BOUNDARY
• Limits heat transfer between inside and outside • Identified by the presence of insulation • The location of insulation in relation to other building components is critical to its effectiveness • Even small areas of missing insulation are very important • Voids of 7% can reduce effective R-value by half
Graphic developed for the US DOE WAP Standardized Curricula
14 AIR BARRIER
• Limits airflow between inside and outside. • The IECC defines the air barrier as materials assembled and joined together to limit air leakage. • Should be collocated with the thermal boundary • Can be the flat ceiling or the roofline
Graphic developed for the US DOE WAP Standardized Curricula
15 BUILDING THERMAL ENVELOPE
• Although these three homes look identical from the outside, each has defined the building thermal envelope differently • This results in significantly different conditioned volumes
16 CODE CONSIDERATIONS
17 R402.2.1 CEILINGS WITH ATTIC SPACES
• For CZ2-3, R-38 is prescriptive requirement, R-49 is requirement for CZ4-8 • Complete coverage of continuous R-30 / or R-38 is deemed to comply • Rulers required every 300 s.f. for blown attic insulation (R301.1.1) • GA: R-19 is acceptable under HVAC attic platforms (32 s.f./platform + 32” walkway)
18 R402.2.1 CEILINGS WITH ATTIC SPACES
19 R402.2.3 EAVE BAFFLES
20 R402.2.2 CEILINGS WITHOUT ATTIC SPACES
• If vaulted ceiling design does not allow sufficient space for required insulation, insulation can be reduced to R-30 • The area of the reduced insulation shall be limited to 500 sq ft or 20 percent of the insulated ceiling, whichever is less. • For prescriptive path only.
21 OLD SCHOOL VAULT WITH VENT
22 UNVENTED VAULT WITH SPF
23 IRC 806.5 UNVENTED ROOF ASSEMBLIES
• To reduce risk of condensation, install a certain amount of “air- impermeable” insulation before using an “air- permeable” product in an unvented roof assembly • Provides Thermal break and also “Condensation break”
24 HYBRID INSULATION APPROACHES
25 PEACHCREST COMMUNITY CENTER
26 RIGID INSULATION ABOVE ROOF DECK • Fog shows lack of air sealing at roof deck INSULATED ROOFLINES
Findings from assessments o Designate materials that will act as air barrier (challenges with 3‐dimensional metal roof decking). o Create material transition location details to link one air barrier material to the next IRC 806.5 VAPOR VENT – NEW FOR CZ1-3
• To many in the building science community, the practicality of this approach in the real world is unproven 29 TRADE-OFFS
• Even if you’ve created a high-performance, well-insulated roofline, chances are you’re still short on insulation • R-20 < R-38
30 TRADE-OFFS – BACKSTOP TABLE
• Home must meet mandatory requirements Table applies to all Trade‐off options: • RESCheck • The building thermal envelope shall be greater than • UA Trade‐off or equal to levels of efficiency of the 2009 IECC • Simulated Perf • Applies to all trade‐off options • Energy Rating Index
31 LOAD CALCULATIONS
32 HOME HEATING & COOLING ENERGY
• This chart represents Duct energy used to heat and Leakage Infiltration cool an existing home 17% Duct • A lot of this energy is 28% 4% gain/ gained/lost in the attic loss Doors 11% • Insulating and air sealing 2% Walls the attic is a high priority 12% Ceilings 17% way to improve energy 9% Windows efficiency in a typical Floors existing home
33 LOAD CALCS & FOAMED ROOFLINE HOUSES
• Foam insulation could increase the HVAC size because… • Conduction occurs through surfaces and insulating the roofline involves more surface area than insulating the flat ceiling • R-value at roofline is usually only ~R-20 but this is less than prescriptive R-38 • Well-sealed houses will likely need ventilation which can add to load
R-38
34 LOAD CALCS & FOAMED ROOFLINE HOUSES
• However, foam insulation should decrease the HVAC size because…
• Home is usually better airsealed (Lower ACH50 from blower door reading) • Insulation coverage is potentially better • Foam “holds its R-value” better over the actual temperature range o R-value is determined at 75°F but really should be measured at 0°F and 120°F – where it matters! • Ducts and equipment are inside thermal envelope • New, known ventilation cfm < random infiltration cfm
R-38
35 THE ATTIC FLOOR
• Insulation on the attic floor is often installed very poorly • This allow heat to flow freely from the attic (summer) or from the home (winter)
36 INSULATION COVERAGE IS KEY!
If 1000 s.f. of R-38 is installed with 30 s.f. of uninsulated area (R-1), it effectively yields the same heat transfer as R-18!
U x A + U x A + U x A Uavg = 1 1 2 2 3 3 Atotal
0.026 x 970 + 1 x 30 Uavg = 1000
Uavg = 0.056 R = 18
37 THE ATTIC FLOOR
• The attic flow has many pathways for air to leak through • Some of these pathways, such as duct chases, allow large volumes of air to move
38 SPRAY FOAMED ROOFLINES
39 SPRAY FOAM ROOFLINES
There are multiple ways of defining the building thermal envelope. The performance advantage of defining the envelope by the roof is air-sealing, consistent insulation coverage and ducts brought inside the envelope
40 OPEN VS CLOSED CELL
• Spray Polyurethane Foam is • Open Cell: low density (1/2 lb/ ft3), made by combining two ~R-3.7/inch, “squishy”, vapor open, chemicals, an A (isocyanate) water is blowing agent, lower cost and B (catalyst, polyol resin, • Closed Cell: high density (2 lb/ ft3), surfactant, blowing agent, fire retardant, coloring) chemicals ~R-6-ish/inch, “solid”, lower vapor in a spray application permeability (~0.5), HFC’s/other as • It is manufactured at the blowing agent, higher cost but does jobsite and is critical that the add ~30% structural benefit mix be correct and that the substrate be dry and warm enough
41 OPEN VS CLOSED CELL
• Both are considered air • Open Cell: Walls (2x4-2x6), framed barriers at specified rafter roofline, framed floors thickness • Closed Cell: Above plus foundation, • Both generate heat probably easier for hybrid during their application (exothermic) and there approaches are limits of how little and how much can be installed in a lift (pass) • Proper installation = minimal/no offgassing
42 WHY NOT R-38 OR 49?
• From an economic standpoint, it is challenging to justify higher R-values after ~5-6” of SPF • For example, 4” to 8” doubles the cost for only ~2% increase in efficiency • Hybrid systems can offset this issue
43 SPRAY FOAM – BEST PRACTICE
• Pay extra attention to the junctions (soffits, roof penetrations) • Cover the rafter tails • Use a straight wire to check for depth in multiple locations (minimum vs average) This attic is now conditioned!
44 DON’T FORGET THE FUNDAMENTALS
• Ducts still need to be sealed and installed properly • No sharp turns • Use appropriate support
45 TRUST BUT VERIFY
• Quality of installation critical that coverage is complete and proper substrate (OSB) temperature is maintained • A blower door test and visual inspection should always be performed on foam houses • Remove old attic insulation for IAQ reasons
46 SPRAY FOAM FAILS
Inexperienced or poorly trained installers can lead to a poor end product • Improper ratio • Temperature • Substrate compatibility
47 FIRE CODE ISSUES
• Ignition barrier o Some open cell and all closed cell foams satisfy • “Thermal” barrier • Basis is ½” drywall for separation between foam and occupants o Attic may not be used for storage but may be accessed and contain HVAC equipment o No drop ceilings • Otherwise, add sprayed-on intumescent coating (which adds cost)
48 COMBUSTION IN FOAMED HOUSES
• Do NOT use attic air as combustion air for atmospheric appliances • Do not add high/low vents to unvented attic • Do not use “volume” of attic as combustion air
49 COMBUSTION IN FOAMED HOUSES
• Combustion equipment inside foamed attics should be sealed combustion, direct- vent (2-pipe systems) • Not an issue in all electric homes!
50 ALTERNATIVES
51 AIR-PERMEABLE INSULATION
• Materials like fiberglass, cellulose, and rockwool, can be used for rooflines • They do not stop airflow! • Batts must be secured, or they will slide down over time • Follow IRC for condensation break (or vapor vent)
52 AIR-PERMEABLE INSULATION
• Fiberglass or cellulose can also be sprayed in • A netting is used to secure the insulation • Mind the knee wall!
53 KNEE WALLS
54 HYBRID FOAM-AND-BATT APPROACH
• A thin layer of spray foam is applied, primarily for air sealing • A fiberglass batt is used to fill the cavity
55 FOAM-AND-BATT APPROACH
• Closed-cell foam is best for this application • More dependable air barrier when applied in a thin layer • Closed-cell is less vapor permeable then open-cell • Open-cell cannot meet density requirements in shallow rafter bays
Green Building Advisor 56 MINIMUM SPECIFIC MATERIAL REQUIREMENTS: CLOSED-CELL POLYURETHANE FOAM (SPF)
• Installers shall meet the • Closed-cell insulation, installed at a manufacturer’s recommended minimum thickness of 1.5 inches and training requirements and shall in contact with the substrate, shall be complete the online health and permitted to serve as a component of safety training for SPF provided by the continuous air barrier the Center for Polyurethanes Industry. • Spray foam shall be well bonded to the substrate, including framing and sheathing.
57 SPRAYABLE CAULK / AERO-BARRIER
• A high-pressure sprayer applies a thin layer of latex, glycerin, and plasticizers • Provides air sealing but no insulation • Aerobarrier sprays while house is pressurized and seals where air leaks out
58 THE ROOF DECK CAN BE THE AIR BARRIER
• The roof deck can be used as an air barrier with proper materials and attention to detail
59 THE ROOF DECK CAN ADD INSULATION
• The roof deck can also add R value with insulated sheathing or foam board
60 Thank you!
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61 THANK YOU
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