Understanding Dampness and Condensation Stephen Hodgson – Property Care Association
Understanding Dampness and Condensation
Stephen Hodgson Property Care Association
Dampness in Buildings
Roof leaks Plumbing leaks Condensation High ground Rainwater penetration Defective rainwater goods Flooding Rising damp Lateral penetration
ALL THESE SOURCES OF WATER ARE UNWANTED!!
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Visual Evidence of Dampness
Mould growth
Deterioration of finishes, blowing/disintegrating plasterwork
Liquid water on surfaces
Staining of finishes
Efflorescent salts on surfaces
Timber decay
Distorted timbers
Dampness to finishes
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Mould Growth
Fungal Decay
The most common cause of damp in domestic properties remains
CONDENSATION!
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Smelly
Wet
Destroys possessions
Looks awful
Health fears!
PART 1 Damp from outside!
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Common Faults
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Other Defects
Ground Water Rainwater goods
Rising Damp Blocked Gullies
Rising Damp
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How are problems damp diagnosed?
1. Visual appraisal
2. Instrument readings
3. Laboratory analysis
Correct diagnosis is vital!
Rising Damp
Reproduced from BRE Digest 245 (2007) Rising Damp in Walls: Diagnosis and Treatment
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Visual appraisal
Some obvious - some less so
We could define rising damp as:
The vertical movement of water up through masonry, the water originating from ground water. The water rises through a series of interconnecting pores by a process called capillarity broadly, porous masonry acts like a wick.
Note: Capillarity in building materials has nothing to do with or related to water
rising in plants/trees.
The rise of liquids from roots to leaves in plants is a process known as
cohesion, not capillarity, and involves hydrogen bonding of water.
RISING DAMP
Soluble chlorides, nitrates, sulphates and
other mineral salts/soluble materials
Salt concentration at top
of rise
Salt band
- most of the salts are
hygroscopic
No significant/low salt levels at base!
If the suction of the wall is greater than the suction of the ground then water will rise if not water will not rise
Rainwater in the soil is the most prevalent source of water at the base of a wall not water table
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How do we treat Rising Damp?
Physical DPC insertion
Chemical injected DPC
How do we treat Rising Damp?
Physical Barriers
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Barriers to damp can take a
number of forms. They all work
using barriers to protect the internal
finishes from water entering the
building.
How do we treat Rising Damp?
Electro Osmosis
EO Systems.
Injection Mortar
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Why Re-Plaster?
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To remove hygroscopic material
To provide a dry wall surface
Prevent future deterioration
It forms part of System
Leaks & Flooding
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Damp Penetration
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Damp Penetration
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Measuring Dampness in Buildings
Instrument readings
Electric moisture meter
Advantages: Non destructive quick to use Easy to create moisture profiles Small and portable Valuable aid in the right hands
Disadvantages: Calibrated for use on wood - not masonry Can give misleading readings (e.g. contaminant salts, foil-backed paper, high carbon substrate) Often misused in the wrong hands
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Radio Frequency Meter
RESISTANCE (CONDUCTANCE) METER
Calcium carbide meter (Speedy)
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Oven Dry Method (BRE Digest 245)
PART 2
Damp Created Inside-
CONDENSATION
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Condensation
We will look at: What is condensation
How and why is does it form in buildings?
Types of condensation
How we identify a condensation problem
How condensation affects occupation
Remedies
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Condensation
The most common form of dampness in residential properties in the UK
Misdiagnosis & misunderstanding of condensation is common
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Condensation
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It is widely accepted that we in the UK have a condensation season. This is usually between October and April but is dependant on the outside temperature. If there are significant dampness problems outside through the summer months, it is probably not condensation.
Condensation
Condensation occurs when water changes from its
gaseous state to its liquid state.
This only happens when the air reaches a relative humidity of 100%
The point at which the water changes state as
saturation occurs is known as the Dew Point
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Condensation
All air contains some water vapour.
The amount of water that can be held in the air is dependant on the temperature.
The higher the temperature, the more water can be held in the air.
Surfaces are usually cooler that the air that surrounds them.
If these surfaces are cooler than the dew point, then water will condense out of the air
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Surface Condensation
Condensation
Condensation is deposited on any surface that is below the
Dew Point.
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Condensation can be deposited at the surface and is known as surface condensation
Or within a structure where it is called interstitial condensation
Effects of cooling air on Relative Humidity (RH)
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60% RH 83%RH 100%RH
20 C
15 C
12 C
Where is the water from?
Atmospheric water coming out of its gaseous state
Water is released into the air from a number of sources associated with normal life and occupation.
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Where is the water from?
Water from rising or penetrating damp is very unlikely to contribute significantly to a condensation
problem.
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If condensation is occurring the walls will be relatively cold. If the walls are cold then significant evaporation is unlikely.
Vapour Pressure
Pascal (Pa) of kilo Pascal (kPa) is the standard unit for measuring pressure.
1 hectopascal (hPa) = 100 Pa 1 mbar.
1 kilopascal (kPa) = 1000 Pa 10 hPa 10 mbar.
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http://upload.wikimedia.org/wikipedia/commons/e/e4/Psidial.jpg
Where is the water from?
High Vapour
Pressure
Kitchen
Low Vapour Pressure
Also note that wind direction will influence the movement of water vapour in the property
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Obvious evidence of condensation problems: Mould Growth on walls ceilings Musty Smell Fungal Growth Water droplets on impervious surfaces Steamed up windows Decay to internal sections of timber window frames
Diagnosis and Investigation
Diagnosis and Investigation
Water will not condense out of the air unless temperatures are at, or below, dew point.
Mould growth can occur if high humidity levels are maintained for long periods.
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Diagnosing Condensation
To determine if condensation is happening at the time of your
investigation:
Air Temperature = Thermometer
Humidity = Hygrometer
Dew Point = Calculation
Surface Temperatures = Surface Thermometer
A MMS meter can do all these things in real time
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Diagnosing Condensation
Data Logging stations
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Diagnosing Condensation
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Diagnosis and Investigation
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Thermal Imaging
Good for locating cold
areas
Reliance on temperature
differential
Diagnosis and Investigation
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Other things to look for Construction types Placing of Insulation Vapour proof materials within construction Ventilation Systems - condition & serviceability Evidence of the causes of atmospheric water
Diagnosis and Investigation
Interstitial Condensation
Inside Outside
Wall temperature gradient
Dew point temperature
gradient
Interstitial condensation
The significance of mould & health
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Is mould associated with condensation a health hazard?
The role of the building
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Typical Bungalow
System built flats
The role of the building
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Steel clad house
High Rise flats
Heating
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Combating Condensation
Improve ventilation sweeps out moisture laden air and replaces with drier air from outside Improve heating make it constant, not intermittent Reduce sources of moisture clothes drying/cooking/bathing Improve thermal properties of walls keep dry (silicone?) Dehumidifiers Improve surface temperatures - insulate
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Combating Condensation
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Remove water vapour at source
Reduce vapour pressure and dilute damp air.
With common sense
Combating Condensation
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Passive stack ventilation
Positive pressure ventilation
With ventilation
Combating Condensation
Dehumidifier
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Thermal lining
Combating Condensation
Other Remedies
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Mould removers and anti mould chemicals
Anti mould Paints
Modern can be effective against mould growth
Don't Guess!
Get Expert Advice!
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