Protection against humidity
Moisture penetration
ƒ
ƒ
ƒ
ƒ
bulk moisture
capillary action
air leakage
vapor diffusion
Protection against humidity
Condensation from humid air infiltration
ƒ sources of water vapor and typical humidity production [g/h]:
­ Resting person
30 to 50
­ Active person
200 to 300
­ Cooking water
100 to 200
­ Bath
2000
­ Shower
2400
­ Apartment plant
10
­ Washing machine (laundry)
50 to 200
­ Dryer (laundry)
500
Total for apartment
400 to 1600
i.e.
7 to 11 kg/day
Protection against humidity
Condensation from humid air infiltration
ƒ reaching of dew-point °T
- assess condensation risk
higher if thermal bridges
30
or poor ventilation
25
20
Dew point
15
10
pvap
Dew-point
5
g/kg
0
0
10
o
17.5 C
Tem perature
Vapor pressure
psat
20
30
40
50oC
Image by MIT OCW.
Protection against humidity
Condensation from humid air infiltration
ƒ reaching of dew-point °T
- assess condensat on
i risk
- calculate amount
of condensed water
- account for evaporation
(summer)
Climate
Sources of
water vapor
Air flow
rate
Thermal
insulation
Interior
humidity
> 80%
Mildew
Surface
temperature
Surface
humidity
> 100%
Condensation
Image by MIT OCW.
Protection against humidity
Condensation from humid air infiltration
ƒ reaching of dew-point °T
­ assessing the condensation risk
Material
lvap [ mg / m h Pa]
Air
0.64
Concrete
0.004
0.010
Brick
0.10
0.175
Mineral wool
0.32
0.64
Image by MIT OCW.
Jvap = S Δp/Rvap
Rvap= Σ Rvap i = Σ di / λvap i
Protection against humidity
Condensation from humid air infiltration
ƒ reaching of dew-point °T
Interior
In
te
rio
r
Ex
te
Slab
rio
r
Load-bearing wall
Airtight foil
Exterior
Exterior roughcast permeable
to water vapor
ƒ prevention measures
Airtight foil
necessary
Protection against humidity
Condensation from humid air infiltration
ƒ reaching of dew-point °T
ƒ prevention measures
­ vapor retarder on warm side (before insulation)
(vapor barrier)
80o
70o
65o
OUTDOORS
70o
67o
60o
INDOORS
50o
o
40
VAPOR BARRIER
30o
o
19
8o
VAPOR BARRIER
10o
PROPER LOCATION
OF VAPOR BARRIER
20
o
10o
o
7
0o F
Images by MIT OCW.
Thermal Insulation, Condensation/moisture
Reading assignment from Textbook:
ƒ “Introduction to Architectural Science” by Szokolay: § 1.4.3 1.4.4 + § 1.5.4
Additional readings relevant to lecture topics:
ƒ "How Buildings Work" by Allen: Chap 8, Chap 12
ƒ "Heating Cooling Lighting" by Lechner: Chap 15