understanding dampness and condensation

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


Mould Growth

Fungal Decay

The most common cause of damp in domestic properties remains

CONDENSATION!


Smelly

Wet

Destroys possessions

Looks awful

Health fears!

PART 1 Damp from outside!


Common Faults

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Other Defects

Ground Water Rainwater goods

Rising Damp Blocked Gullies

Rising Damp


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


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


How do we treat Rising Damp?

Physical DPC insertion

Chemical injected DPC


Physical Barriers


Barriers to damp can take a

number of forms. They all work

using barriers to protect the internal

finishes from water entering the

building.


Electro Osmosis

EO Systems.

Injection Mortar


Why Re-Plaster?


To remove hygroscopic material

To provide a dry wall surface

Prevent future deterioration

It forms part of System

Leaks & Flooding


Damp Penetration


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


Radio Frequency Meter

RESISTANCE (CONDUCTANCE) METER

Calcium carbide meter (Speedy)


Oven Dry Method (BRE Digest 245)

PART 2

Damp Created Inside-

CONDENSATION


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


Condensation

The most common form of dampness in residential properties in the UK

Misdiagnosis & misunderstanding of condensation is common


Condensation


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


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


30

Surface Condensation

Condensation

Condensation is deposited on any surface that is below the

Dew Point.



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)


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.



Water from rising or penetrating damp is very unlikely to contribute significantly to a condensation

problem.


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.


http://upload.wikimedia.org/wikipedia/commons/e/e4/Psidial.jpg


High Vapour

Pressure

Kitchen

Low Vapour Pressure

Also note that wind direction will influence the movement of water vapour in the property


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


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.


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



Data Logging stations




Thermal Imaging

Good for locating cold

areas

Reliance on temperature

differential


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


Interstitial Condensation

Inside Outside

Wall temperature gradient

Dew point temperature

gradient

Interstitial condensation

The significance of mould & health


Is mould associated with condensation a health hazard?

The role of the building


Typical Bungalow

System built flats

The role of the building


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




Remove water vapour at source

Reduce vapour pressure and dilute damp air.

With common sense



Passive stack ventilation

Positive pressure ventilation

With ventilation


Dehumidifier


Thermal lining


Other Remedies


Mould removers and anti mould chemicals

Anti mould Paints

Modern can be effective against mould growth

Don't Guess!

Get Expert Advice!


understanding dampness and condensation

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