Basements are Changing John Straube, Ph.D., P.Eng Basements: New & Retrofit Energy Efficient, Durable, Healthy Building Science Corporation presented by www.buildingscience.com Increasingly used as living space Not a root /coal cellar anymore! High quality space expected - new and retrofit Owner can finish herself Low cost for high density sites (cities) Can now locate laundry, heating, hotwater elsewhere Modern basements are different they need different approaches! Commercial basements are similar Basements No. 2/73 Basements Part of the Enclosure Basements Below grade enclosure Includes floor slabs, practically need to include transition Separates exterior (soil/air) and interior Functions of all parts of the enclosure Support heavy lateral loads Control less temperature, more water Finish (usually) Basements No. 3/73 Basements No. 4/73 Moisture: Old ideas Control: Moisture CBD#161-1974 Drainage layer Exterior moisture barrier Exterior insulation Air barrier Exterior insulation Drainage layer Capillary break Air tightness Moisture causes most failures Mold (musty basement smell) Decay (especially rim joist) Staining /Paint peeling Floods and leaks, eventually causing the above Salt damage to masonry old basements Where does moisture come from? 1. Exterior 2. Built in 3. Interior Basements No. 5/73 Basements No. 6/73 Straube buildingscience.com 1 of 14
1. Exterior Environment Moisture Sources 1. Precipitation 2. Rainwater shedding 3. Surface water Run-off 5. Sub-surface Moisture - Groundwater - Vapor 4. Water vapor Solutions: Minimize Rain loads Provide Good Shedding Provide Good Drainage Provide Capillary Breaks 1. Controlling Exterior Moisture Sources Same approach as above-grade rain control Deflection Overhangs, slopes, gutters Drainage/Exclusion/Storage Three strategies for the enclosure Drying Remove built-in incidental moisture 5. Sub-surface Moisture 5. Basements No. 7/73 Basements No. 8/73 Control Exterior surface water Surface Drainage First step Common problem Overhang Gutters Downspouts Sloped grade Perimeter drain Basements No. 9/73 Basements No. 10/73 Solution Problem Basements No. 11/73 Basements No. 12/73 Straube buildingscience.com 2 of 14
Basement Enclosure Strategies Exterior surface water Drainage wont help here Damage recovery Basements No. 13/73 Classification of Groundwater control 1. Drained Needs capillary break and gap/drain space 2. Perfect Barrier ( waterproofing ) One layer of perfect water resistance Beware hydrostatic forces 3. Storage (mass) Safe storage capacity and drying Don t use vapor barriers, do insulate (carefully) Basements No. 14/73 Screened(1) Below-Grade Enclosure Wall System C. Drainage plane and Capillary break E. Concrete or concrete masonry F. Insulation (int. option) G. Interior finish Drained type: drainage system with drainage plane, and capillary break Above Grade Level A. Screen (similar to cladding---shed and screen surface moisture-rain) B. Drainage crushed stone Below Grade Level B. Drainage draining backfill Drainage by specific backfill soil properties Interface with undisturbed below grade environment Screened(2) Below-Grade Enclosure Wall System C. Drainage plane and Capillary break E. Concrete or concrete masonry F. Insulation (int. option) G. Interior finish Drained type: drainage system with drainage layer& plane, capillary break Above Grade Level A. Screen -optional (similar to cladding---shed and screen surface moisture-rain) Below Grade Level Backfill not necessarily free draining Non-soil drainage layer B. Drainage crushed stone Interface with undisturbed below-grade environment Collection and Exit Drain Basements No. 15/73 Collection and Removal Drain Basements No. 16/73 Screened(3) Below-Grade Enclosure Wall System Interior Drainage (often retrofit) C. Drainage plane and Capillary break E. Concrete or concrete masonry F. Insulation (int. option) G. Interior finish Drain can be gutter or new draintile Drained type: drainage system with drainage plane, and capillary break Above Grade Level Below Grade Level B. Backfill not necessarily free draining B. Drainage crushed stone A. Screen optional (similar to cladding---shed and screen liquid moisture-rain and groundwater) Collector and Removal Drain Interface with undisturbed below grade environment Basements No. 17/73 Barrier (1) Below-Grade Enclosure Wall System No Drainage hydrostatic pressure developed A. Positive side Waterproofing B. Concrete or masonry C. Insulation heat flow control (int. option) D. Interior finish Perfect barrier: drainage system can be used to reduce hydrostatic pressure waterproofing layer resists significant head of water Above Grade Level Below Grade Level Backfill not necessarily free draining B. Drainage (opt) crushed stone Collector and Removal Drain A. Screen optional (similar to cladding---shed and screen surface moisture-rain) Interface with undisturbed below grade environment Must use waterproofing below water table! Slab? Connection? Lowers water table, reduces hydrostatic pressure Basements No. 18/73 Straube buildingscience.com 3 of 14
Barrier (2) Below-Grade Enclosure Wall System No Drainage hydrostatic pressure developed A. Negative side Waterproofing B. Concrete or concrete masonry C. Insulation heat flow retarder (int. option) D. Interior finish Perfect barrier : drainage system to reduce hydrostatic pressure waterproofing Above Grade Level Below Grade Level Backfill not necessarily free draining A. Screen optional (similar to cladding---shed and screen surface moisture-rain) Interface with undisturbed below grade environment Storage (1) Below-Grade Enclosure Wall System Limited ability to resist moisture loads A. Rubble or concrete masonry (storage) B. Usually no insulation to allow drying C. Usually no interior finish (limewash) Storage (mass) system: usually no intentional drainage often no capillary break Above Grade Level Below Grade Level Backfill not necessarily free draining A. Screen optional (similar to cladding---shed and screen surface moisture-rain) Interface with undisturbed below grade environment B. Drainage (opt) crushed stone B. Drainage (opt) crushed stone Collector and Exit Drain Basements No. 19/73 Collector and Removal Drain Basements No. 20/73 Air gap membranes aka Dimple Sheets provide drainage gap act as vapor barrier Damproofing Capillary break = drainage plane, but needs gap vapour barrier? NOT waterproofing Waterproofing resists standing head of water Basements No. 21/73 Basements No. 22/73 Glassfiber Drainage Gap Rockwool Drainage Gap Basements No. 23/73 Rockwool Drainage Layer Basements No. 24/73 Straube buildingscience.com 4 of 14
2. Built-in Moisture 3. Interior Moisture Sources 2. Localized Flooding 2. 1. Built-in Moisture (from water in concrete, mortar, wood, etc.) 2. Construction moisture accumulated during construction (ice, snow, rain, etc.) Minimize by: Delay finishing internally Reduce water in concrete 1. & 2. 1. Water Vapor in contact with cold surfaces: air movement, and diffusion 2. Localized Flooding (abnormal - Water & Vapor) 2. Solutions 1. Control interior vapor levels by: winter ventilation summer dehumidification 1. Avoid contact with cold surfaces keep surfaces warm stop water vapor moving 2. Control flooding floor drains disaster pans at appliances 1. & 2. Basements No. 25/73 Basements No. 26/73 Vapor failure not ground water Managing Air and Vapor Need to solve Surface condensation Sol n: Keep surface warm & air dry Interstitial condensation Control air/vapor flow to cold surfaces & dry air Solar driven summer condensation Allow vapor flow in, slow rate of flow Basements No. 27/73 Basements No. 28/73 Context: Below-grade Conditions Exterior soil is almost always at 100%RH Plus liquid water can press against wall Never gets as cold or as hot as above grade Significant vertical temperature gradients Top is different than bottom Typical Soil Temperatures 25 6820 6015 Temperature (C) 5010 405 320 2.0 m 0.1 4 m 0.5 20 m 1.0 36 m 3110 m For 7500 F HDD climate Note: open field values. No house to add heat Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 25-5 Date Basements No. 29/73 Basements No. 30/73 Straube buildingscience.com 5 of 14
Soil Temperatures 5 10 15 20 25 68 Measured Soil / Air Temperatures Waterloo Measured Soil 30 Temperatures Soil Temperatures Outdoor Air at University 7500 F of HDD Waterloo Climate Weather Station (1999) 25 36 in deep 30 12 in deep 20 soil temp (50 mm) 6 in Deep 25 soil temp (200 mm) 15 Temperature (F) 20 50 10 15 5 10 32 0 2005/09/28 2005/10/28 2005/11/27 2005/12/27 2006/01/26 2006/02/25 2006/03/27 2006/04/26 2006/05/26 2006/06/25 5-5 Temperature (C) Temperature (C) 15-10 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 Basements No. 31/73-5 -15 Time (weeks from January) Daily Average temperatures smooths air temperature, reduces Basements peaks No. 32/73 Exterior Temperature & Moisture Conditions Soil Relative Humidity almost always =100% Liquid water may be present Winter Jan. Above-grade design Summer July 0 10 20 3 2 5 0 7 0 Temperature Basements No. 33/73 top footing Basement Psychrometrics Since soil is at nearly 100%RH, the vapor drive is almost always inward except at very top (& rim) during winter in humid houses January footing top July Flow in Flow out Flow in Winter Summer 100% RH 75% RH 50% RH 25% RH 0-10-10.0 ºC -5.0 00.0 ºC 5.0 1010.0 ºC 15.0 2020.0 ºC 25.0 3030.0 ºC 35.0 4040.0 ºC 14 º F 32 º F 50 º F Temperature 68 º F 86 º F Basements No. 104º 34/73 F ( C) 4000 3500 3000 2500 2000 1500 1000 500 Basement Vapor Diffusion Air & Vapor Wetting Sources Water vapor is moving from soil to interior for almost the entire year over all but the top foot of basement Hence, should place vapor barrier on outside But we put it on the inside! Moisture from drying concrete, air leakage, wicking and soil also trapped by interior vapor barriers Basements No. 35/73 Diffusion of Construction Moisture Air Leakage of Interior / Exterior Air Capillary Wicking of Soil Moisture Basements No. 36/73 Straube buildingscience.com 6 of 14
No drying to the interior possible Typical basement ( normal practice ) 1. Start dry 2. No leaks 3. No poly 4. Be lucky Basement in a Bag The Diaper Tolerable north of Arctic Circle Basements No. 37/73 Basements No. 38/73 How to insulate/finish basement wall? We need to: Control exterior ground water Insulate (energy, comfort and moisture) Control air leakage and diffusion condensation Provide (a little) inward drying Accommodate different conditions over height How to do we all this? Insulation Location Choices Builders like to insulate the interior Basements No. 39/73 Basements No. 40/73 Basements No. 41/73 Basements No. 42/73 Straube buildingscience.com 7 of 14
Hybrid Add layer of: foam or spray foam To allow inward drying about 1 perm Basements No. 43/73 Basements No. 44/73 Basements No. 45/73 Basements No. 46/73 Basements No. 47/73 Basements No. 48/73 Straube buildingscience.com 8 of 14
Retrofit Building Science 49 Basements No. 50/73 Retrofit Drainage of peel and stick or dimple sheet provide superior drainage and leak resistance Retrofit Slab, drainage and sump before wall insulated Repair Wall leaks groundwater Retrofit/Reno Risk reduction Min 1 XPS Energy: 3 +EPS Dimple sheet Basements No. 51/73 Basements No. 52/73 Basement Wall Air Movement Air leakage Water vapor moves along with airflow If moist air touches a cold surface, condensation occurs Summer and winter problem Control? Include an air barrier Avoid air loops Manage pressures Basements No. 53/73 ww.buildingscience.com Basements No. 54/73 Straube buildingscience.com 9 of 14
Internal Stack Effect & Insulation Gaps in batt insulation on both sides Wrinkles inevitable Cold air = heavy Inside Hot air = light Batt Outside Common basement problem Air gaps Basements No. 55/73 Internal Stack Effect Gaps in batt Cold Weather insulation on both sides cold closed circuit energy cost condensation cool Hot air = light Result: Air Flow Cold air = heavy Basements No. 56/73 Problems w/ air permeable insulation Solution w/ Insulated Sheathing Cold Weather Cold Condensation Air permeable insulation Warmer Air permeable insulation Air leakage Air leakage Crack Crack Basements No. 57/73 Basements No. 58/73 Foam only Vertical or horizontal furring Basements No. 59/73 Basements No. 60/73 Straube buildingscience.com 10 of 14
Basements No. 61/73 Basements No. 62/73 Basement Heat Loss Slab heat loss Basements No. 63/73 Basements No. 64/73 Spray foam basement insulation Open cell Climate specific Closed cell Basements No. 65/73 Building Science 66 Straube buildingscience.com 11 of 14
Building Science.com 67 Building Science.com 68 Materials to use? Insulated Concrete Forms (ICF) Foam Board: EPS, XPS, PIC water tolerant vapour barriers to vapour retarders spray foam Semi-rigid (Icynene) and rigid (Spray polyurethane) airtight May allow some drainage R values of 4 to 6/inch vapour semi-permeable (Icynene much more) If you afford it, use them cap break, insulation, vapor retarder, above grade Basements No. 69/73 Basements No. 70/73 Thermomass Basements No. 71/73 Basements No. 72/73 Straube buildingscience.com 12 of 14
Rim joists Scenario Wood generally on exterior 1.5 wood is a vapor barrier Practically difficult to stop air leakage Result Condensation on rim joist in cold weather Decay if it can t dry in or out Solutions Insulate on exterior Slabs Slabs can loose significant energy Currently the only uninsulated part of many buildings Keep warm (comfort & condensation) Control wicking and diffusion Make softer Consider floods Basements No. 73/73 Basements No. 74/73 OSB over heavy poly dimple sheet vapor barrier and some insulation Air seal joints/edge Slabs Beware Joints Basements No. 75/73 Basements No. 76/73 Summary Control surface water by drainage Drainage layer on exterior of walls No vapor barriers on inside Painted drywall, stud, batt with foam OK Care needed at rim joist What happens if there is a flood, leak, etc. Basements No. 77/73 Basements No. 78/73 Straube buildingscience.com 13 of 14
Conclusions Building in a hole in the ground is hard Drainage is better than waterproofing Don t forget about built-in moisture and remember summer Insulation and drainage are the best tools, not vapor barriers and waterproofing Basements No. 79/73 Basements No. 80/73 Inward Solar Drives at Grade Inward Diffusion @ grade Wet concrete from rain, grade, built-in Sun shines on wall and heats it Water evaporates and diffuses in & out Can condense inside if cold and impermeable 1. Temperature and solar heating warms wet material 2.Vapour drives inward (& out) Drying If permeable 3.Vapour dries to inside Wetting If impermeable 3.Condensation on cold surfaces Basements No. 81/73 Basements No. 82/73 Hot Wet materials 4000 3500 30-60 C 90-100% RH VERY high vapour pressure 3000 2500 2000 1500 Summer Winter 1000 500 100% RH 75% RH 50% RH 25% RH 0-10.0-5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 Temperature ( C) -10 ºC 14 º F 0 ºC 32 º F 10 ºC 50 º F 20 ºC 68 º F 30 ºC 86 º F 40 ºC 104º F Basements No. 83/73 Straube buildingscience.com 14 of 14