Kohta Ueno Basement Insulation: What to Do & What Not to Do March 29, 2012 Background Basement Thermal Behavior Basement Insulation: What to Do & What Not to Do 2 Basement/Foundation Energy Use Basement Insulation Location Basement ~¼ of energy consumption in a typical house case Often left unaddressed in insulation retrofits Basements ~80% of houses in Northeast and Midwest Code requirement for insulation in DOE Climate Zone 3 and higher Uninsulated concrete wall very low R value (R-0.4 to R-0.8) Basement Insulation: What to Do & What Not to Do 3 Basement Insulation: What to Do & What Not to Do 4 Ueno buildingscience.com 1 of 20
Basement Insulation Location Heat Loss from Basements Percentage of below-grade heat loss 0% 10% 20% 30% 40% 0.0-0.3 0.3-0.6 Depth in meters 0.6-0.9 0.9-1.2 1.2-1.5 4.6 ACH50; 2129 CFM 50 total; 1100 CFM 50 through floor 8.5 ACH50; 3590 CFM 50 total; 1740 CFM 50 through floor Basement Insulation: What to Do & What Not to Do 5 1.5-1.6 Greatest heat loss from top of wall Basement slab insulation little energy benefit (but some moisture benefits) Basement Insulation: What to Do & What Not to Do 6 Heat Loss from Basements Background Basement Moisture Behavior Full height insulation anyway cold surface condensation, easier to build? Basement Insulation: What to Do & What Not to Do 7 Basement Insulation: What to Do & What Not to Do 8 Ueno buildingscience.com 2 of 20
Basement Moisture Behavior Historically, many moisture problems with basement insulation builder callbacks, etc. Building a hole in the ground Recommended assemblies with reduced moisture risk Foundations w. bulk water issues Severe and rapid damage to interior insulation and finishes due to bulk water intrusion Basement Insulation: What to Do & What Not to Do 9 Basement Insulation: What to Do & What Not to Do 10 Basement Insulation Problems Wintertime interior moisture condensation (like abovegrade walls) Cold Weather Condensation Issues Basement Insulation: What to Do & What Not to Do 11 Basement Insulation: What to Do & What Not to Do 12 Ueno buildingscience.com 3 of 20
Basement Insulation Problems Wintertime interior moisture condensation (like abovegrade walls) Condensation at bottom of wall (thermal lag of soil) Lack of drying of assembly (moisture from concrete and soil); soil is at 100% RH Soil gas condensation Liquid water through wall Basement Insulation: What to Do & What Not to Do 13 Priorities for Dealing with Water Damage Functions (In Order of Importance) Liquid Water Control from exterior drainage, grading Will address in more detail Capillary Water ( wicking ) Air-Transported Moisture Vapor Diffusion General rules; can vary on case-to-case basis Basement Insulation: What to Do & What Not to Do 14 Drain Water Away From Foundation Dealing With Bulk Water Also address water concentrations Basement Insulation: What to Do & What Not to Do 15 Basement Insulation: What to Do & What Not to Do 16 Ueno buildingscience.com 4 of 20
Control Liquid Water (drainage mat) Ground Skirt Detail Optional: French drain at perimeter Photos via Petersen Engineering petersenengineering.blogspot.com See Building Science Insight 057: Hockey Pucks and Hydrostatic Basement Insulation: Pressure What to Do & What Not to Do 17 17 Basement Insulation: What to Do & What Not to Do 18 Recommended Wall (XPS/Frame) Recommended Assemblies 1 XPS Stud wall w. batt Drywall/latex paint Air seal XPS Capillary break @ footing Sill gasket under bottom plate April 9, 2008 Wintertime condensation controlled Summertime (bottom of wall) condensation controlled Concrete can dry through XPS at a safe rate XPS is moisture tolerant Basement Insulation: What to Do & What Not to Do 19 Basement Insulation: What to Do & What Not to Do 20 Ueno buildingscience.com 5 of 20
Recommended Wall (Foil-faced Polyiso) Recommended Wall (Spray Foam) Substantially dry basement Judgment call Steel studs clear of spray foam No drying through foam: air seal must be perfect (100% RH behind foam) Photos via Marc Rosenbaum Basement Insulation: What to Do & What Not to Do 21 thrivingonlowcarbon.typepad.com Basement Insulation: What to Do & What Not to Do 22 Spray foam basement insulation Other Good Basement Walls Open cell Climate specific No bulk water Closed cell Adhered membrane (backup water control) XPS foam (insulation) Drainage mat to footing drain (primary water control) Protection of insulation above grade? Building Science 2008 Basement Insulation: What to Do & What Not to Do 23 Foundations and Basements No. 23/74 Basement Insulation: What to Do & What Not to Do 24 Ueno buildingscience.com 6 of 20
Other Good Basement Walls Other Good Basement Walls Basement Insulation: What to Do & What Not to Do 25 Basement Insulation: What to Do & What Not to Do 26 Test House Setup (Chicago) Non Recommended Assemblies Basement Insulation: What to Do & What Not to Do 27 Basement Insulation: What to Do & What Not to Do 28 Ueno buildingscience.com 7 of 20
Test House Setup (Kitchener) Test Walls (Kitchener) Test walls 2 extruded polystyrene Polyethylene roll blanket Stud frame w. fiberglass & polyethylene; painted gypsum board Stud frame w. fiberglass & no polyethylene; painted gypsum board Basement Insulation: What to Do & What Not to Do 29 Basement Insulation: What to Do & What Not to Do 30 Polyethylene & Stud Frame Walls Stud frame, polyethylene one side Stud frame, polyethylene both sides ( moist. barr. ) So What Did We Find? All the walls essentially worked no substantial failures If no liquid water, and dry interior conditions (wintertime RH) failure prone assemblies OK Examine monitoring results relative risks Air leakage important Many other conclusions Polyethylene roll blanket Basement Insulation: What to Do & What Not to Do 31 Basement Insulation: What to Do & What Not to Do 32 32 Ueno buildingscience.com 8 of 20
Moisture buildup (Double Poly Wall) Stud frame wall with polyethylene on both sides RH sensor behind exterior poly moisture barrier RH rose to ~100% and remained at this level Basement had dried for 3+ years before installation Lack of drying of assembly Inward Vapor Drive Condensation source of builder callbacks Magnitude and relationships of moisture flows Basement Insulation: What to Do & What Not to Do 33 Basement Insulation: What to Do & What Not to Do 34 Inward Vapor Drive to Poly Inward Vapor Drive to Poly Wafer sensor roughly at grade Sensor shows difference between 100% RH and liquid water condensation Moisture Content (%) 50 40 30 30 100% RH wafer range 20 10 10 ~50% RH wafer range 0 9/05 11/05 1/06 2/06 4/06 6/06 7/06 9/06 11/06 12/06 9/05 11/05 1/06 2/06 4/06 6/06 7/06 9/06 11/06 12/06 Roll Roll Blanket Blanket Frame/poly Frame/polyFrame/latex Frame/latex T Exterior Roll Blanket Frame/poly Frame/latex T Exterior T Exterior Roll Blanket Frame/poly Frame/latex T Exterior 80 70 60 50 40 30 20 10 0-10 -20-20 Exterior T T (F) (F) Basement Insulation: What to Do & What Not to Do 35 Basement Insulation: What to Do & What Not to Do 36 Ueno buildingscience.com 9 of 20
Air Leakage Foil-faced polyisocyanurate in plastic tee tracks Dewpoint of air behind insulation identical to interior Evidence for air leakage in many walls In most cases, allowed drying of concrete wall Frost and Freezing Issues Basement Insulation: What to Do & What Not to Do 37 37 Basement Insulation: What to Do & What Not to Do 38 Freezing/Frost Heave Issues Freezing/Frost Heave Issues Interior insulation reduces heat flux colder ground temperatures/deeper frost penetration Frost damage unlikely <60 extreme frost depth Inward frost heave impossible directional heave Adfreezing similar: can occur on unheated structures. Heated heat flux still outwards (although reduced) Canadian BETT study (1980s) Basement Insulation: What to Do & What Not to Do 39 Basement Insulation: What to Do & What Not to Do 40 Ueno buildingscience.com 10 of 20
Freezing/Frost Heave Issues Footing Capillary Breaks Basement Insulation: What to Do & What Not to Do 41 Basement Insulation: What to Do & What Not to Do 42 Vapor Diffusion vs. Capillarity Vapor diffusion Capillarity ~10 the moisture movement rate of vapor diffusion alone Capillarity Basement Insulation: What to Do & What Not to Do 43 Controlling Capillary Water Polyethylene under floor slab (w. freedraining fill) Capillary break between soil & basement wall Measures already in building codes Capillary break at footing-wall connection Basement Insulation: What to Do & What Not to Do 44 Ueno buildingscience.com 11 of 20
Footing Capillary Breaks Footing Capillary Breaks Basement Insulation: What to Do & What Not to Do 45 45 Basement Insulation: What to Do & What Not to Do 46 46 Footing Capillary Breaks Basement Insulation: What to Do & What Not to Do 47 47 Material Choices Asphalt-based (standard dampproofings) Cementitious coatings (cement-based waterproofing, polymer modified) Can add acrylic polymer admixture if desired (greater durability?) Latex paint based waterproofing coatings Silanes & siloxanes Basement Insulation: What to Do & What Not to Do 48 48 Ueno buildingscience.com 12 of 20
Membrane Material Membrane Material Basement Insulation: What to Do & What Not to Do 49 Basement Insulation: What to Do & What Not to Do 50 Membrane Material Membrane Material Basement Insulation: What to Do & What Not to Do 51 Basement Insulation: What to Do & What Not to Do 52 Ueno buildingscience.com 13 of 20
Background Spray Foam Bulk Water Control Retrofits Basement with persistent bulk water (leakage) issues Retrofits of existing foundations Especially uneven wall (rubble stone) foundations Hybrid insulation and bulk water control assemblies Basement Insulation: What to Do & What Not to Do 53 Basement Insulation: What to Do & What Not to Do 54 Retrofit Insulation Location Choices Retrofits: interior insulation is often the only available option Basement Insulation: What to Do & What Not to Do 55 Basement Insulation: What to Do & What Not to Do 56 Ueno buildingscience.com 14 of 20
Interior Rubble Retrofit Interior Rubble Retrofit Basement Insulation: What to Do & What Not to Do 57 Basement Insulation: What to Do & What Not to Do 58 Interior Rubble Retrofit Interior Rubble Retrofit Basement Insulation: What to Do & What Not to Do 59 Basement Insulation: What to Do & What Not to Do 60 Ueno buildingscience.com 15 of 20
Interior Rubble Retrofit Air Gap Membrane Variant Spray foam sufficiently stiff at typ. thickness (2 +) XPS basement slab perimeter insulation Spray foam forms concrete slab thermal break Basement Insulation: What to Do & What Not to Do 61 Basement Insulation: What to Do & What Not to Do 62 Beam pocket detail (air seal) Flat Surface Walls Spacer mesh to provide drainage behind foam Drainage space must be airtight Beam pocket detail (air seal away from sub-slab) Basement Insulation: What to Do & What Not to Do 63 Basement Insulation: What to Do & What Not to Do 64 Ueno buildingscience.com 16 of 20
Flat Surface Walls Alternate version: air gap membrane layer Drainage space must be airtight Another option: XPS with channels and filter fabric Partial Drainage Detail Insulated slab on top of existing slab No membrane up wall surface Light gauge steel framing interior wall Wet vs. dry basement? Basement Insulation: What to Do & What Not to Do 65 Basement Insulation: What to Do & What Not to Do 66 Partial Drainage Detail Spray Foam Bathtub 2011 by Byggmeister; reprinted with permission Sump must be connected to drainage mesh Air leakage around drainage space termination (interior chimney) Basement Insulation: What to Do & What Not to Do 67 Basement Insulation: What to Do & What Not to Do 68 Ueno buildingscience.com 17 of 20
Insulation Normalized Costs $ per sf R-value $0.12 $0.10 $0.08 $0.06 $0.04 $0.02 $0.00 Installed Costs Full retrofit $5-$7/sf basement wall area (R-20) With stud wall $10-$11/sf basement wall area Spray foam (installed) $1.00-$1.50/board foot Perimeter drains ~$20-40/lineal foot Rat slab (2 thick) ~$3.25-$4.00/sf floor area Insulation system + water management Cost comparisons should be to insulation + drainage Has to be compared to what actually works! Basement Insulation: What to Do & What Not to Do 69 Basement Insulation: What to Do & What Not to Do 70 Sill Beam Moisture Durability Additional Research: Sill Beam Durability Basement Insulation: What to Do & What Not to Do 71 Basement Insulation: What to Do & What Not to Do 72 Ueno buildingscience.com 18 of 20
Sill Beam Moisture Durability Sill Beam Moisture Durability This building has been around for the last 100 years Basement Insulation: What to Do & What Not to Do 73 Basement Insulation: What to Do & What Not to Do 74 Sill Beam Moisture Durability Sill to foundation surface colder Less drying available Permeable insulation detail? Permeable Sill Insulation Detail Foil-faced polyisocyanurate overclad on most of house High-density mineral fiber (permeable) at sill Basement Insulation: What to Do & What Not to Do 75 Basement Insulation: What to Do & What Not to Do 76 Ueno buildingscience.com 19 of 20
Sill Beam Moisture Risk Factors Field Survey Work Exterior water control features Capillary activity of foundation Magnitude of splashback Height of sill beam/rim joist above grade Drainage plane location Permeability of exterior Westford Barn retrofit sill beam example Sub slab insulation reduces risk of moisture issues (carpets on slabs; cardboard boxes) Basement Insulation: What to Do & What Not to Do 77 Basement Insulation: What to Do & What Not to Do 78 Questions? Kohta Ueno kohta@buildingscience.com This presentation is based research covered in BSC TO2 7.7 Hybrid Foundation Insulation Basement Insulation: What to Do & What Not to Do 79 Resources Building Science Digest 103: Understanding Basements http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements Building Science Insight 041: Rubble Foundations http://www.buildingscience.com/documents/insights/bsi-041-rubble-foundations/ Building Science Insight 045: Double Rubble Toil and Trouble http://www.buildingscience.com/documents/insights/bsi-045-double-rubble-toil-trouble/ Building Science Insight 057: Hockey Pucks and Hydrostatic Pressure http://www.buildingscience.com/documents/insights/bsi-057-hockey-pucks-and-hydrostatic-pressure/ RR-1108: Hybrid Foundation Insulation Retrofits: Measure Guideline http://www.buildingscience.com/documents/reports/rr-1108-hybrid-foundations-retrofits-measure-guideline/ RR-1003: Building America Special Research Project High-R Foundations Case Study Analysis http://www.buildingscience.com/documents/reports/rr-1003-building-america-high-r-foundations-case-studyanalysis/ RR-??: Bulk Water Control Methods for Foundations RR-0309: Renovating Your Basement http://www.buildingscience.com/documents/reports/rr-0309-renovating-your-basment/ Information Sheet 511: Basement Insulation http://www.buildingscience.com/documents/information-sheets/basement-insulation/ Hygrothermal Behavior of Interior Basement Insulation (Kohta Ueno MASc Thesis) http://uwspace.uwaterloo.ca/handle/10012/3242 Info-408: Critical Seal (Spray Foam at Rim Joist) http://www.buildingscience.com/documents/information-sheets/critical-seal-spray-foam-at-rim-joist Basement Insulation: What to Do & What Not to Do 80 Ueno buildingscience.com 20 of 20