The Drying of Heritage Properties Nigel Hewitt Technical Manager

Communication Establish good lines of communication –Project Managers –Insured –All other relevant parties

Goals What are trying to achieve What was pre loss condition –Indoor Atmosphere 18ºC - 22ºC 40% - 60% Relative Humidity Can we find a “Dry Standard” –How “Dry” was the property pre-incident

Goals Where is the moisture located –Moisture Meters Moisture sensors Penetrating Non-penetrating Thermal Hygrometers Thermography Boroscopes

Goals What’s Wet –What kind of materials –Structural or decorative How Wet is it –Which is the most appropriate drying system Open Closed Combination

The Drying Process Water is present in one of three forms –Surface Water Very easy to dry –Free Water Easy to dry –Bound Water Harder to dry

What Effects The Drying TEMP AIRFLOW Humidity

Surface Free Water Bound Water Temperature Humidity Airflow

Moisture Movement Moisture movement occurs when there is a vapour pressure imbalance between materials and environments Moisture movement ceases when there is vapour pressure equilibrium

Permeance Ability of moisture to pass through materials Based on: –Vapour Pressure –Temperature –Relative Humidity –Pore size

Considerations Permeability of different materials –Connected materials with different rates of permeability Vapour Barriers –Where are they located –Can they be perforated –Can they be removed Hidden cavities

Considerations Secondary Damage –Moulds –Dry Rot –Wet Rot

Drying Equipment Airmovers –Essential part of drying process –Velocity, pressure and placement effect performance Airmover Types –Carpet dryers –Inter-air dryers –Axial fans –High volume airmovers

Dehumidifers Types of dehumidifier –Domestic refrigerant –Commercial Refrigerant –LGR –Desiccants Humididstats

Alternatives Heat drying systems –Is it safe Low level back ground heat Controlled Ventilation Dry Slowly

Considerations Surface finishes –Limewash –Paints –Wood panelling –Fabric –Leather

Areas of Concern

Target Drying Ducting –Simple way to improve drying

Target Drying

Drying Hardwood Floors –Apply positive air pressure one side –Negative pressure on the other –Greatly increases drying efficiency

Target Drying

Injection Drying –Dries voids and cavities –Use positive and negative pressure –Reduce claim duration –Equipment can be expensive

Secondary Damage

Contents

Monitoring Where is the moisture located –Moisture Meters Moisture sensors Penetrating Non-penetrating Thermal Hygrometers Thermography –Data Loggers –Remote Monitoring –Calcium Carbide

Data Loggers

Remote Monitoring Continual Monitoring –Temp –Rh –Specific Humidity –Dew Point –Set Thresholds –Alarms

Calcium Carbide Measures moisture content in materials A weighed sample is added with calcium carbide into the pressure vessel Chemical reaction produces acetylene gas The increase in pressure can be read directly from a calibrated pressure gauge

In Summary Determine what’s wet and how wet it is Check all unaffected items Select appropriate drying system Monitor frequently and accurately Flood Prevention

Thank You Any Questions