Basements: New & Retrofit – Problems – Causes Energy Efficient, … · 2020. 1. 3. · Basement...
Transcript of Basements: New & Retrofit – Problems – Causes Energy Efficient, … · 2020. 1. 3. · Basement...
Basements: New & Retrofit
Energy Efficient, Durable, Healthy
John Straube, Ph.D., P.Eng
presented by www.buildingscience.com
Building Science Corporation
www.BuildingScience.comBasements No. 2/73
This presentation
• Basement functions
• Basement Performance
– Problems
– Causes
• Solutions
• Crawlspaces & Slabs next session
www.BuildingScience.comBasements No. 3/73
Basements are Changing
• 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, hotwaterelsewhere
• Modern basements are different – they needdifferent approaches!
• Commercial basements are similar
www.BuildingScience.comBasements No. 4/73
Basements – Part of the
Enclosure
•
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 5/73
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
– Control
– Finish (usually)
www.BuildingScience.comBasements No. 6/73
Building Enclosure Functions
• Support
– Structure: wind, gravity, earthquake
– Below grade – Soil pressure, hydrostatic?
• Control
– Heat (less extreme than above grade)
– Air (less air pressure, but it stinks, Radon?)
– Moisture (vapor, free and bound liquid)
• Finish – usually, but optional
• Distribute (sometimes)
www.BuildingScience.comBasements No. 7/73
Moisture: Old ideas
• CBD#161 - 1974
• Drainage layer
• Moisture barrier
• Exterior
insulation
• Air barrier
Exterior insulation
Drainage layer
Capillary break
Air tightness
www.BuildingScience.comBasements No. 8/73
Control: Moisture
• 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
©2008 Building Science Corporation
Appendix V
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1. Exterior
Environment
Moisture
Sources
Solutions:
Minimize Rain loads
Provide Good Shedding
Provide Good Drainage
Provide Capillary Breaks
3. Surface water Run-off
2. Rainwater shedding
1. Precipitation
5. Sub-surface Moisture
- Groundwater
- Vapor
4. Water vapor
5. Sub-surface Moisture5.
www.BuildingScience.comBasements No. 10/73
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
www.BuildingScience.comBasements No. 11/73
Control ExteriorControl Exterior
surface watersurface water
www.BuildingScience.comBasements No. 12/73
Surface Drainage
• First step
– Common problem
• Overhang
• Gutters
• Downspouts
• Sloped grade
• Perimeter drain
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 13/73
Solution
www.BuildingScience.comBasements No. 14/73
Problem
www.BuildingScience.comBasements No. 15/73
Exterior surface waterExterior surface water••Drainage wont help hereDrainage wont help here
••Damage recoveryDamage recoverywww.BuildingScience.com
Basements No. 16/73
Basement Enclosure Strategies
• 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)
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 17/73
Basement Ground Water Control
www.BuildingScience.comBasements No. 18/73
Screened(1) Below-Grade Enclosure Wall System
Collection and Exit Drain
Interface with undisturbed
below grade environment
Above Grade Level
Below Grade Level
A. Screen (similar to cladding---shed
and screen surface moisture-rain)
B. Drainage–
crushed stone
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
B. Drainage– draining
backfill
Drainage by specific
backfill soil properties
www.BuildingScience.comBasements No. 19/73
Screened(2) Below-Grade Enclosure Wall System
Collection and Removal Drain
Interface with undisturbed
below-grade environment
Above Grade Level
Below Grade Level
A. Screen -optional (similar to
cladding---shed and screen surface
moisture-rain)
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
Backfill – not necessarily
free draining
Non-soil drainage layer
B. Drainage–
crushed stone
www.BuildingScience.comBasements No. 20/73
Screened(3) Below-Grade Enclosure Wall System
Collector and Removal Drain
Interface with undisturbed
below grade environment
Above Grade Level
Below Grade Level
A. Screen – optional (similar to
cladding---shed and screen liquid
moisture-rain and groundwater)
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
B. Backfill – not necessarily
free draining
Interior Drainage
(often retrofit)
B. Drainage–
crushed stone
Drain can be gutter
or new draintile
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 21/73
Barrier (1) Below-Grade Enclosure Wall System
Collector and
Removal Drain
Interface with undisturbed below
grade environment
Above Grade Level
Below Grade Level
A. Screen – optional
(similar to cladding---shed and
screen surface moisture-rain)
B. Drainage (opt)
– crushed stone
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
Backfill – not necessarily
free draining
No Drainage – hydrostatic
pressure developed
Lowers water table, reduces
hydrostatic pressure
Must use waterproofing below
water table!
Slab? Connection?
www.BuildingScience.comBasements No. 22/73
Barrier (2) Below-Grade Enclosure Wall System
Collector and Exit Drain
Interface with undisturbed below
grade environment
Above Grade Level
Below Grade Level
A. Screen – optional
(similar to cladding---shed and
screen surface moisture-rain)
B. Drainage (opt) –
crushed stone
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
Backfill – not necessarily
free draining
No Drainage – hydrostatic
pressure developed
www.BuildingScience.comBasements No. 23/73
Storage (1) Below-Grade Enclosure Wall System
Collector and Removal Drain
Interface with undisturbed below
grade environment
Above Grade Level
Below Grade Level
A. Screen – optional
(similar to cladding---shed and
screen surface moisture-rain)
B. Drainage (opt) –
crushed stone
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
Backfill – not necessarily
free draining
Limited ability to resist
moisture loads
www.BuildingScience.comBasements No. 24/73
Damproofing
• Capillary break = drainage plane, but needs gap
• vapour barrier?
•NOT waterproofing
Waterproofing resists standing head of water
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 25/73
Air gap membranes
aka Dimple Sheets
• provide drainage gap
• act as vapor barrier
www.BuildingScience.comBasements No. 26/73
GlassfiberGlassfiber Drainage GapDrainage Gap
www.BuildingScience.comBasements No. 27/73
R k l D i L
Rockwool Drainage GapRockwool Drainage Gap
www.BuildingScience.comBasements No. 28/73
Controlling ground/rain water
• Deflection: Roof and Surface Drainage
• Classification of Groundwater control– 1. Drained
• Needs capillary break & gap/drain space
– 2. Perfect Barrier• 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)
• Drying to Inside and Perimeter Drains
Review: Exterior Moisture
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 29/73
•Minimize by:
• Delay finishing internally
• Reduce water in concrete
1. Built-in Moisture (from
water in concrete, mortar,
wood, etc.)
2. Construction moisture
accumulated during
construction (ice, snow,
rain, etc.)
1. & 2.
1. & 2.
2. Built-in Moisture
www.BuildingScience.comBasements No. 30/73
Initial Drying
From: Lstiburek 2002
• Soil cold for first yr
• Excavation collects water
• Concrete is wet– _ to 1 gal/ft2
– 25-50 liters/m2
• Cannot dry to wet exterior
• Solutions = dry in– No low perm interior
– Semi-permeable insulation
– Smart vapor barrier
www.BuildingScience.comBasements No. 31/73
2. Localized Flooding
(abnormal - Water & Vapor)
2. Localized Flooding
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 appliances2.
2.
3. Interior Moisture Sources
1. Water Vapor in contact
with cold surfaces: air
movement, and diffusion
Solutions
www.BuildingScience.comBasements No. 32/73
Vapor failure– not ground water
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 33/73
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
www.BuildingScience.comBasements No. 34/73
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
www.BuildingScience.comBasements No. 35/73
Typical Soil Temperatures
2.0 m
-5
0
5
10
15
20
25
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Date
Tem
per
atu
re(C
)
0.1 m
0.5 m
1.0 m
3 m
For 7500 F HDD climate
4”
20”
36”
110”
32
40
50
60
68
25
Note: open field values.
No house to add heat
www.BuildingScience.comBasements No. 36/73
Soil Temperatures
5 10 15 20 25
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 37/73
Soil Temperatures at University of Waterloo Weather Station (1999)
-5
0
5
10
15
20
25
30
0 4 8 12 16 20 24 28 32 36 40 44 48 52
Time (weeks from January)
Te
mp
era
ture
(C)
soil temp (50 mm)
soil temp (200 mm)
Waterloo Measured Soil
Temperatures
Waterloo Measured Soil / Air Temperatures
Daily Average temperatures – smooths air temperature, reduces peaks-15
-10
-5
0
5
10
15
20
25
30
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
Tem
pera
ture
(C)
Outdoor Air
36 in deep
12 in deep
6 in Deep
Tem
pera
ture
(F)
32
15
50
68
7500 F HDD Climate
www.BuildingScience.comBasements No. 38/73
Exterior Temperature & Moisture
Conditions
• Soil Relative Humidity
almost always =100%
• Liquid water may be
present
Temperature200 10
Summer
July
Winter
Jan.
32 50 70
Above-grade design
www.BuildingScience.comBasements No. 39/73
-10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0
Temperature(°C)
0
500
1000
1500
2000
2500
3000
3500
4000
100%RH
75%RH
50%RH
25%RH
Basement Psychrometrics
Summer
Winter
-10 ºC
14 º F0 ºC
32 º F10 ºC
50 º F
20 ºC
68 º F
30 ºC
86 º F
40 ºC
104º F
Since soil is at nearly 100%RH, the
vapor drive is almost always inwardexcept at very top (& rim) during
winter in humid houses
Jan
uary
top
foo
tin
g
Ju
ly
foo
tin
gto
p
Flow out
Flow in
Flow in
www.BuildingScience.comBasements No. 40/73
Basement Vapor Diffusion
• 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
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 41/73
Air & Vapor Wetting Sources
• Problems with fibrous insulation & vapor barrier
Diffusion of
Construction
Moisture
Air Leakage of
Interior /
Exterior Air
Capillary
Wicking of
Soil Moisturewww.BuildingScience.com
Basements No. 42/73
Basement in a Bag – “The Diaper”
• Tolerable north of Arctic Circle
No drying to the interior possible
www.BuildingScience.comBasements No. 43/73
• Typicalbasement(“normalpractice”)
1. Start dry
2. No leaks
3. No poly
4. Be lucky
www.BuildingScience.comBasements No. 44/73
Basement Wall Air Movement
• 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
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 45/73
Air leakage
www.BuildingScience.comBasements No. 46/73
Internal Stack Effect & Insulation
Hot air = lightHot air = light
Cold air = heavy
• Gaps in batt insulationon both sides
•Wrinkles inevitable
Air gapsBatt
Inside
Outside
Common basement problem
www.BuildingScience.comBasements No. 47/73
Internal Stack Effect
Cold WeatherCold Weather
Hot air = light
Cold air= heavy
Result: AirFlow
• Gaps in battinsulation on bothsides
• closed circuit
• energy cost
• condensation
cold
cool
www.BuildingScience.comBasements No. 48/73
Problems w/ air permeable insulation
Air leakageAir leakage
Air permeableAir permeable
insulationinsulation
CrackCrack
Cold
Condensation
Cold Weather
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 49/73
Solution w/ Insulated Sheathing
Air leakageAir leakage
Air permeableAir permeable
insulationinsulation
CrackCrack
Warmer
www.BuildingScience.comBasements No. 50/73
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?
www.BuildingScience.comBasements No. 51/73
Insulation Location Choices
• Builders like to insulate the interior
www.BuildingScience.comBasements No. 52/73
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 53/73
Hybrid
• Add layer
of:
– foam or
– spray
foam
To allow inward drying
• about 1 perm
www.BuildingScience.comBasements No. 54/73
www.BuildingScience.comBasements No. 55/73
Best?
• No summer
thermal lag
• Sub-slab
insulation
a plus
Free Draining backfill
or drainage membrane
www.BuildingScience.comBasements No. 56/73
• Foam only
• Vertical or
horizontal
furring
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 57/73
Spray foam
basement insulation
• Open cell
– Climate specific
• Closed cell
www.BuildingScience.comBasements No. 58/73
Materials to use?
• 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)
www.BuildingScience.comBasements No. 59/73
Insulated Concrete Forms (ICF)
• If you afford it, use them –
– cap break,
– insulation,
– vapor retarder,
– above grade
www.BuildingScience.comBasements No. 60/73
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 61/73
www.BuildingScience.comBasements No. 62/73
Inward Solar Drives at 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
www.BuildingScience.comBasements No. 63/73
2.Vapour drives
inward (& out)
3.Condensation
on “cold”
surfaces
1. Temperatureand solar heating
warms wetmaterial
Wetting
If impermeable
Drying
If permeable
3.Vapour dries
to inside
Inward Diffusion @ grade
www.BuildingScience.comBasements No. 64/73
-10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0
Temperature(°C)
0
500
1000
1500
2000
2500
3000
3500
4000
100%RH
75%RH
50%RH
25%RH
Hot Wet materials
• 30-60 C
• 90-100% RH
•VERY high vapour pressure
Summer
Winter
-10 ºC
14 º F0 ºC
32 º F10 ºC
50 º F
20 ºC
68 º F
30 ºC
86 º F
40 ºC
104º F
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 65/73
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
www.BuildingScience.comBasements No. 66/73
Basement
• New or retrofit
• Solves slab
wetness &
cold
www.BuildingScience.comBasements No. 67/73
Slabs
• Keep warm (comfort & condensation)
• Control wicking and diffusion
• Make softer
• Consider floods
www.BuildingScience.comBasements No. 68/73
OSB over heavy poly dimple sheet
vapor barrier and some insulation
Air seal joints/edge
Beware Joints
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 69/73
Slabs
www.BuildingScience.comBasements No. 70/73
Retrofit Slab, drainage and sump before wall insulated
www.BuildingScience.comBasements No. 71/73
Retrofit
Drainage of peel and stick or
dimple sheet provide superior
drainage and leak resistance
Dimple sheet
• Repair
– Wall leaks
groundwater
• Retrofit/Reno
– Risk reduction
• Min 1” XPS
• Energy: 3”+EPS
www.BuildingScience.comBasements No. 72/73
Summary
• Control surface water by drainage
• Drainage layer on exterior of walls
• Poly interior stop drying and often result in
problems
• Painted stud with foam OK
• Care needed at rim joist
• What happens if there is a flood, leak, etc.
©2008 Building Science Corporation
Appendix V
www.BuildingScience.comBasements No. 73/73
Conclusions
• Building in a hole in the ground is hard
• Don’t forget about built-in moisture
– and remember summer
• Moisture comes in liquid AND vapor
• Insulation and drainage are the best tools,not vapor barriers and waterproofing
©2008 Building Science Corporation
Appendix V