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Introduction to Structural Drying

Introduction to Structural Drying. The Changing “State” of Water. Water exists in three states of matter: solid (ice) liquid (water) gas (steam/vapour). The primary factor that will ultimately determine what state water will take is the amount of energy each molecule contains.

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Introduction to Structural Drying

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  1. Introduction to Structural Drying

  2. The Changing “State” of Water • Water exists in three states of matter: • solid (ice) • liquid (water) • gas (steam/vapour). • The primary factor that will ultimately determine what state water will take is the amount of energy each molecule contains. • The more energy each water molecule possesses the more rapidly it can move. • When molecules are moving quickly enough the chemical attraction that they have to each other is no longer sufficient to hold them together.

  3. The Changing “State” of Water • There are several phase changes that can occur depending upon whether energy is being added or removed. • Requires more energy during the phase changes to change water from one state to another than is required for almost any other type of molecule.

  4. The Drying Pie • Humidity, airflow andtemperature directly affectthe state in which waterexists and the rate in whichthe change occurs. • The process requires restorers to change liquid water into vapour (evaporation). • Water vapour must be removed from the building • Dehumidification • by changing the vapour to water by cooling it • Air exchange • venting the moisture laden air out of the building and bringing in air from outside.

  5. Air movement • Facilitates evaporation by removing the boundary layer of humid air from around the wet surface. • Lowering the vapour pressure at the surface • The more moisture a material contains the faster the water will evaporate. • Greater evaporation rates require more airflow to maintain the lower vapour pressure across the surface. • As materials dry less air flow is required. WHY?

  6. Air movement • Road block - Large amounts of air movement creates two problems. • Air movement creates thermal loss (cools down). • Cooler air and cooler surface materials • Less energy is transferred to the moisture molecules • Not sufficient energy to make the phase change to escape the material. • Large quantities of air movers create a lot of heat energy (BTUs). • In theory the heat created by the air movers aids in the drying process as the heat energy is transferred to the water molecules • BTUs created by the air movers can generate temperatures above 32 degrees • outside of the efficient operating ranges of refrigerant dehumidifiers.

  7. Humidity • Dehumidification is used to remove moisture from the air lowering the vapour pressure • Equipment used to create air movement can continue to facilitate moisture evaporating from the wet structure or contents.

  8. Humidity • Road block – Limiting the temperature to the limitations of the dehumidifier hinders the evaporation rate. • By raising the temperature, relative humidity is reduced, increasing the ability of the air to hold more moisture. (Increasing thirst). • Above 32 degrees the dehumidifier does not have enough capacity to reduce the temperature of the incoming air to dew point. • hence condensation on the dehumidifier coils. • Large amounts of air movement equipment can create a lot of heat.

  9. Humidity • As the amount of water in the structure decreases and the vapour pressure becomes lower the efficiency of the dehumidifier is also reduced. • Lowering the temperature of the incoming air closer to 20 degrees towards the end of the job ensures the dehumidifier can achieve the required temperature drop to achieve dew point. • But it is in this phase additional energy in the form of heat accelerates the drying process. • Common ways to control temperatures: • use the building air conditioning system • install portable air conditioning systems • reduce or increase the amount of air movers • temporarily use cooler air from outside the structure (commonly called burping). • use a controlled heating drying system to control heat and humidity ….. Drymatic. • lower temperature cause the water to freeze condenser coils, dehumidifier goes into to defrost cycle.

  10. Temperature (Heat) • Two main conclusions that can be drawn from research • At the beginning of the drying process where there is a lot of free water not bound in the materials, a 10°C temperature increase causes a doubling of the evaporative rate. • Equivalent to doubling the amount of air movers. • Following this towards the end of the process where evaporation is decreased due to water being bound in the materials the terminal drying rate increases rapidly with increases in temperature. • Heat gives the water the energy required to make the phase change from water to vapour.

  11. Temperature (Heat) • Road block – Simply heating up the structure with heaters ensures vastly faster evaporation rates. • Uncontrolled heat and fast evaporation can lead to overdying, differential drying or drying too fast. • Knowledge and technology required to understand how much heat and how to control it is now available. • Drymatic!

  12. Three Phases of Drying

  13. Three Phases of Drying • Phase 1 - Removal of Liquid Water - Extraction • significantly affect the amount of drying equipment • the time required to return the building and contents to equilibrium moisture content. • Effective extraction will also ensure less destructive methods of restoration are required. • Phase 2 - Surface Drying • Surface drying of carpet underlay and surface water from building materials such as timber and concrete. • Phase 3 – Drying of Structural Materials • Drying of water bound in materials. • Different methods, knowledge and tools are required to get the energy required to the bound water to ensure phase change.

  14. Determining Equipment Requirements • Extraction • Air movement • Dehumidification • Heat Drying Equipment • Air Filtration Devices

  15. Extraction • Effective removal of standing water will significantly affect • The amount of drying equipment and • the time required to return the building and contents to equilibrium moisture content. • Effective extraction will also ensure less destructive methods of restoration are required.

  16. Extraction • The greater the air flow and vacuum pressure, the more effective that equipment will be • Truckmounted equipment has significantly higherairflow and vacuum pressure is more effective inremoval of standing water. • Specialised portable flood extraction equipment that uses shorter hose lengths and larger diameterhoses (2 inch) can be effective. • Portable equipment exhaust air should be vented outside of the building. • Small vacuums such as shop vacs or wet vacs and domestic vacuums do not provide adequate power for effective extraction.

  17. Extraction Tools • A weighted compression can use heavy weights or as a stand on machine and works on the principle of extracting/pushing the water out of the underlay through the carpet and into the extraction machine. • A vacuum sealed (water claw or equivalent) can be used with truckmount and portable extraction equipment. • As the vacuum sealed toolrequires water to create thevacuum seal • Recommended to first extractwith the tool to remove asmuch water as possible fromthe underlay • Completing extraction with aconventional carpet cleaningwand.

  18. Extraction Tools • A conventional carpet cleaning wandis not efficient at removal of waterfrom carpet underlay. • Where specialised extraction tools are not utilised it is recommended the carpet underlay is removed. • A carpet cleaning wand is effective for extraction direct stick carpets. • Extraction test to gauge the effectiveness of extraction on carpet

  19. Extraction Tools • To ensure adequate extraction from hardwood flooring • install wood floor panels and attach them to a truck mount or portable flood extractor for up to a hour • Prior to installation ofInjectidry, interair. • This process ensures asmuch of the standing waterfrom below and frombetween the boards isremoved prior to beginningthe process of attemptingto remove the bound water.

  20. Air movement • Air movers are used to facilitate evaporation by removing the boundary layer of humid air from around the wet surface. • Air movers rapidly supply dryer air directly to the wet surface and thereby lowering the vapour pressure at the surface which facilitates faster evaporation. • Secondly air movers are used to manage air movement around the structure. • Air management eliminates the need to use equipment in all affected areas. • Used to manage air pressure, humidity, and temperature or air quality.

  21. Different types of air movers • Traditional carpet dryers • commonly referred to as air movers or blowers. • 3/4 hp motor, more static pressure. • Static pressure is used by air moversto lift carpet, • With accessories used to duct air into small spaces such as wall cavities and under cabinets and under hardwood flooring.

  22. Different types of air movers • Low amp air movers • smaller than ¾ hp, lower air movementand lower static pressure. • The advantage of using low amp airmovers • more air movers can be used on one circuitwhilst generating large volumes of CFM • generating less heat than traditional carpet dryer air movers. • Used in less destructive restoration processes • where excess heat generation will affect the performance ofdehumidifiers • Where power supplies are limited.

  23. Different types of air movers • Low pressure axial fans • used to move large volumes of air with lower ampdraw. • drying long surfaces and open areas and carpets. • not useful for pushing air into cavities and throughduct work. • The advantage of using low amp air movers • more air movers can be used on one circuit whilst generating large volumes of CFM • generating less heat than traditional carpet dryer air movers. • Used in less destructive restoration processes • where excess heat generation will affect the performance of dehumidifiers • Where power supplies are limited.

  24. Different types of air movers • High pressure ventilating fans • used with ducting to move largevolumes of air. • used to generate strong positive ornegative air pressures • used to manage air pressure, humidity, temperature or quality. • Specialty air movement equipment air mover adaptors used to inject air flow under cabinets, into wall and ceiling cavities and under hardwood flooring.

  25. Different types of air movers • Low Volume High Pressure Air Movement systems • Interair Drying System or Intectitdry • used when more pressure is needed but air volume is less important. • They can be setup in either positive pressure or negative pressure • used to dry cavities such as under cabinets,wall cavities and under hardwood flooring. • 100 CFM and produce up to 60 inches ofstatic pressure • standard air mover typically produces 2-3inches of static pressure • Since cavities have a small volume of air spacethe low CFM of the unit is effective in drying. • Pressure is the main focus of the system. • A large amount of pressure is required to pushor pull air through lengths of tubing, throughwalls or other cavities or pull air through floorboard cracks and crevices.

  26. Different types of air movers. • Direct air drying systems and heat boosters • specialised Direct Air Drying wall and floor matt systems • constant warm air stream can be directed at wet surfaces • warm airstream willquicklyremove theboundarylayer andpromote fastand efficientevaporation

  27. To estimate the number of air movers required(conventional dehumidification) • Determine the square meters and class • Divide the square meters by the factors as follows • Class 1: • divided the square meters by 14, then divide square meters by 28 • Class 2 or Class 3: • divide the square meters by 4.6, then divide square meters by 5.6 • The resulting number is the minimum and maximum range or air movers needed • Additional airflow may be required for offsets such as closets and bay windows • Speciality air movers maybe required if sub surfaces require air flow • The number of air movers may need to be increased or decreased through out the drying process based on changes in the psychometric readings and moisture readings.

  28. Guidelines for placement of air movers using(conventional dehumidification) • In a class 2 or class 3 water loss • every 3 – 4 meters along the wall • Air mover are placed at a 15 to 45 degreeangle facing the wall • Air mover snout 2 – 3 cm of the wall but not touching it • All air movers in each area will face the same direction • ensure that air movers are creating a cyclone effect and not pushing against each other • The positioning of air movers may need altered through out the drying process based on changes in the psychometric readings and moisture readings.

  29. Guidelines for number and placement of air movers(heat drying systems) • Minimal air movement is required • just enough air movement to ensure warm air is circulated evenly around the structure • high energy systems air movement must be enough to adequately ventilate the wet air from the building.

  30. Dehumidification • Dehumidification is used to remove moisture from the air so that the equipment, used to create air movement, can continue to facilitate moisture evaporating from the wet structure or contents. • A balanced drying system is achieved when the rate of dehumidification exceeds the rate of evaporation. • Conventional Refrigerant • Low Grain Refrigerant • Desiccant

  31. Conventional refrigerant dehumidifiers • Air temperatures between18 and 32 degrees • Minimum specific humidity of65 grains per pound. • Used for class 1 water loss situations such as drying wet carpet and underlay. • Conventional dehumidifiers perform very well for class 1 water loss situations • not suitable for drying structural building materials.

  32. Low Grain Refrigerant Dehumidifiers (LGR) • Low grain refrigerant dehumidifiers (LGR) achievehigher efficiency by incorporating a pre coolingstage which provides the dehumidifier withprecooled air to process. • work most efficiently with air temperaturesbetween 18 and 32 degrees • minimum specific humidity of35 grains per pound. • LGRs are recommend for most water losssituations including drying of some more porousstructural components. • all brands all makes and modelsperformance can be improved by managing air temperatures. • Higher temperature with a maximum temperature of 30 degrees is optimal at the beginning of the job where high humidity exists • gradually lowering temperatures to a minimum of 20 degrees is optimal towards the end of the job where lower humidity exists.

  33. Low Grain Refrigerant Dehumidifiers (LGR) • Common ways to control temperatures • use the building air conditioning system • install portable air conditioning systems • temporarily use cooler air from outside the structure (commonly called burping) • Where additional heat is required to increase temperature thermostat controlled convection heat dry systems such as Drymatic can be used. • When comparing dehumidifier capacity and performance look at the AHAM rating not the total daily capacity • plus look at the performance of the dehumidifier in LGR conditions of specific humidity of 35 – 65 gpp)

  34. Dri-Eaz LGR 7000 • Easily outperformed it’s closestcompetitor and AHAM • Under LGR conditions outperformedthe competition by as much as 40%. • Advanced Crossflow Technology tomaximize energy utilization • Plus - Built-in sensors constantly monitorreal time performance data to automatically calculate ideal operating parameters – such as fan speed and cycle duration.

  35. Desiccant Dehumidifiers • As usually only 75% of the process air is returned to the structure negative air pressure is usually created in the structure. • Care to ensure the quality of the makeup air entering the structure. • achieve a very low specific humidity of 10 grains per pound • efficient at drying structural components such as hard wood floors and wall cavities. • Capacity of desiccantdehumidifiers isexpressed in thevolume of air that canbe processed per houreither CFM or CMH ofthe process air exitingthe dehumidifier. • High volume desiccantdehumidifiers are verygood at structural dryingas they produce largevolumes of warm dry air.

  36. To estimate the number of dehumidifiers required to start the job • Determine volume of air (L x W x H) • Note the capacity of the dehumidifiers • AHAM litres per day rating of the refrigerant/LGR • Process air out cubic meters per hour (CMH) of the desiccant. • Determine the classification of water loss • Class 1, Class 2, Class 3 or Class 4

  37. Dehumidification Factor Table

  38. Refrigerant/LGR • Cubic meters ÷ Dehumidification factor = AHAM Litres required • Divide the AHAM litres required by the AHAM litres of the units to be installed to get the minimum number of units required to start the job • round up

  39. Desiccant • Cubic meters x Dehumidification factor = CMH required to start the job • Divide the CMH required by the CMH of the process out air of the units • round up

  40. Dehumidification Factors • A guide for the minimum dehumidification equipment required to ensure a dehumidification exceeds evaporation. • i.e. a balanced drying system • After initial setup dehumidification may need to be increased or decreased based on changes in the psychometric readings and moisture readings. • Relative humidly should not linger above 60% for any length of time. • If it does… inadequate extraction or not a closed drying chamber • With adequate extraction relative humidity of 40% or below should be achieved within the first 24 hours • If it does… inadequate extraction, not close drying chamber, or recalculate dehumidification required

  41. Understanding Thirst • Practical exercise

  42. Understanding Thirst

  43. Understanding Thirst

  44. Understanding Thirst Start of the job100% - 60% = 40% Thirst End of the job100% - 40% = 60% Thirst

  45. Understanding Thirst 100% - 33% = 67% Thirst 100% - 20% = 80% Thirst

  46. Understanding Thirst • Adding 10 degrees at the beginning • 40% x 167.5% = 67% thirst • increases the thirst of the air by 167.5% • Adding 20 degrees at the beginning • 40% x 200% = 80% thirst • increases the thirst of the air by 200% 100% - 33% = 67% Thirst 100% - 20% = 80% Thirst

  47. Understanding Thirst 100% - 7% = 93% Thirst 100% - 14% = 86% Thirst 100% - 24% = 76% Thirst

  48. Understanding Thirst • Adding 10 degrees at the end • 60% x 126.7% = 76% thirst • increases the thirst of the air by 126.7% • Adding 20 degrees at the end • 60% x 143.3% = 86% thirst • increases the thirst of the air by 143.3% • Adding 30 degrees at the end • 60% x 155% = 93% thirst • increases the thirst of the air by 155% 100% - 7% = 93% Thirst 100% - 14% = 86% Thirst 100% - 24% = 76% Thirst

  49. Why can’t I raise the temp of the job when using a dehumidifier? • Temperature drop required by the dehumidifier to reach dew point (condensation on the coils) • 20 deg – 6.5deg = 13.5 deg • Adding 10 degrees it still below 30 deg so the dehumidifier should still work right? • 30 deg – 6.5deg = 23.5 deg • The dehumidifier does not have enough capacity to achieve the temperature drop required to reach dew point • About 18 degrees does not mater which make model or brand Dew Point

  50. Why does the dehumidifier not work efficiently below 18 degrees? • Temperature drop across the coils of 18 degrees • 18 degrees in the room minus 18 degrees across the coils = zero • Water freezes at zero • Dehumidifiers goes into defrost cycle, starts up again, minimal time goes into back into defrost cycle again… and so on Water freezes at zero degrees

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