BS ARCHITECTURE 2B

MOISTURE
Architectural Design 3 – Design In Architectural Interiors (AD
213)

SUBJECT ADVISER
AR.MARK JOSEPH ANDRADA

REPORTERS
ARCHES,BERHEL ANGELO
BESA,ANGELYN
BILLOSILLO,MARK LLOYD
BOCALA,MARK JOHN
BUNCALAN,JADE
FABILA,QUINNIE
 • OBJECTIVES
AT THE END OF THIS LESSON,THE STUDENT MUST BE ABLE TO LEARN
HOW TO:
• ELIMINATE MOISTURE SOURCES
• IMPROVE VENTILATION
• PREVENT MOISTURE MOVEMENT
• MONITOR AND ADDRESS MOISTURE ISSUES
• IMPLEMENT ROUTINE MAINTENANCE
• UTILIZE MOISTURE RESISTANT MATERIALS

• CONTENTS
• MOISTURE PROBLEM
• MOISTURE BALANCE
• MOISTURE SOURCES
• TRANSPORT PROCESS

INTRODUCTION
HVAC designers must consider and deal with moisture in almost all
Of their work. The moisture most building designers consider is in
Vapor form inside ducts, conditioned spaces, or outdoors. Although
This may be the form of moisture that most interests a design engineer,
Understanding the source of this vapor is important, as this understanding allows for
more robust and economical designs, better risk management, more accurate diagnostics and
improved forensics.

Moisture Problems
Moisture has long been important to building designers since it is the single
most important agent of building deterioration. For example, moisture, from whatever
source, is involved in
• Moisture is a significant factor in building deterioration as it leads to
various problems such as corrosion of metal components, chemical deterioration of
materials, freeze-thaw damage, discoloration of finishes, and growth of biological
forms like mold and dust mites.
 • The moisture-induced electrochemical corrosion affects metal
components like HVAC equipment, structural framing, and masonry anchors.
• Chemical deterioration and dissolution of materials like gypsum
sheathing, wood products, and the occurrence of damaging chemical processes are also
attributed to moisture.
• Moisture causes freeze-thaw damage to concrete, stone, and masonry,
leading to structural failure and cracking.
• Moisture-related issues can result in discoloration, staining, irregular
wetting of building finishes.
• Volume changes due to moisture, such as swelling, warping, and
shrinkage, can cause degradation of appearance, structural failure, and cracks.
• The growth of biological forms like mold, plants, and dust mites is
facilitated by moisture, affecting occupant health, structural integrity, and appearance
of buildings.
1. Four conditions must be met for a moisture-related problem to occur:
• A moisture source must be present
• There must be a path for moisture movement
• A driving force must cause moisture to move
• The materials involved must be vulnerable to moisture damage

The Moisture Balance

1. The Importance of Moisture Balance:
- Maintaining a balance between wetting and drying is crucial to prevent moisture
accumulation and related issues in buildings.
2. Considerations for Moisture Controls
- When evaluating the risk of moisture damage, factors such as the extent and duration
of wetting, storage, and drying need to be taken into account.
3. Moisture Control Strategies:
- Strategies to control moisture typically focus on reducing wetting by improving
airtightness, increasing vapor resistance, and minimizing rainwater penetration.
4. Inevitability of Wetting:
- Recognizing that achieving perfect construction is unlikely, it is accepted that some
wetting will occur due to imperfections like insulated joints in chilled water piping and leaks
in windows.
5. Focus on Drying Potential:
- Given the imperfect nature of building construction, there is a growing emphasis on
enhancing drying potential and storage capacity to address moisture issues effectively.
 MOISTURE SOURCES
Different Sources of Moisture in Buildings:
• Liquid water from precipitation and plumbing leaks;
• Water vapor from exterior, activities, and processes within the building;
• Liquid and vapor from the soil adjoining the building;
• Moisture from construction materials or brought in with goods and people.

Sources of Water Intrusion: Rain deposition on roofs is a significant source of water,

typically ranging from several hundred to one thousand kg/m2 in most climates, with walls
receiving a percentage of this load. Even a small amount of leaked precipitation into a building
can cause severe damage over time.
Potential Damage from Water Leaks: Undetected leaks, like from leaky valves or
windows, can lead to rapid mold growth and serious structural issues. Rain leaks or plumbing
failures can result in large amounts of water discharged into a building, causing catastrophic
damage.
Water Vapor Challenges: Water vapor, although in smaller quantities than liquid
water, can also pose significant problems. Condensation of water vapor on pipes, walls, and
windows is a common issue, with exterior water vapor entering buildings through ventilation
and unintentional leaks.
Internal Moisture Sources: Occupants, their activities, and processes within buildings
can release significant amounts of moisture. Specific processes such as heated indoor pools or
manufacturing operations can contribute a substantial amount of vapor, emphasizing the need
for detailed investigation by design engineers.
 Moisture from Soil: Soil near the basement, foundation, and first floor of buildings
can be a major source of moisture in both liquid and vapor forms. Liquid water from surface
runoff or the water table can seep through cracks and openings, while water stored within the
soil can wick through building materials.

1. Importance of Moisture in Building Construction:

• Moisture content is crucial in building construction but varies depending on the type
of construction.
• Wood framing can lose around 10% of its weight in moisture.
• A normal concrete mix contains 200 kg of water per cubic meter, with half being
released as vapor.
2. Impact of Moisture Release:
• A typical house basement system with concrete can release thousands of liters of water
in the first year or two.
• A 200 mm thick reinforced concrete floor slab in an office building can release 20
liters per square meter in the first two years.
3. Moisture Retention in Concrete Block:
• Concrete blocks can trap water in their cores, affecting moisture levels in buildings.
 TRANSPORT PROCESS
Moisture transport occurs through various mechanisms, with the primary processes
ranging from least to most
powerful:
• Vapor diffusion and surface diffusion in some materials.
• Vapor convection, which involves air movement.
• Liquid water capillarity, where water wicks through porous materials.
• Liquid gravity flow through cracks, openings, and macropores, affected by hydrostatic
pressure.
1. Vapor diffusion moves water vapor from areas of high concentration to low
concentration.
• Diffusion can occur through the air or within porous materials.
• Water vapor does not diffuse through nonporous materials such as steel,
glass, and some plastics.
2.Vapor convection is the primary way water vapor is moved through ducts and spaces.
Very small air flows can move larger water vapor quantities compared to diffusion. Convection
through openings in buildings causes significant interstitial condensation, exceeding diffusion
effects by tens to hundreds of times.
• Convection through building openings is a significant source of internal
moisture after rain. To control or eliminate convective moisture transport, durable air
barrier systems must be in place in all building enclosures.
• It is critical to control vapor convection, which includes managing
airflow. This requires sealing air ducts that pass through the air barrier, regulating
pressure zones inside buildings to prevent unintentional airflow paths, and ensuring
proper functioning of supply and exhaust fans.
3.Capillary suction drives moisture movement in porous materials from areas of high
liquid concentration to low concentration. The rate of this transport is determined by pore size,
with smaller pores facilitating stronger suction but slower flow.
• Despite its sluggish pace, capillary action remains effective for extended
periods, making it crucial in structures in contact with moist soil and rain-exposed
surfaces.
• To manage capillary flow, barriers can be installed to impede or halt the
moisture transfer. Common methods include incorporating an air gap or using capillary-
inactive materials like non-porous or hydrophobic substances.
• Practical applications of controlling capillarity involve adding air spaces
behind brick cladding, utilizing crushed stone beneath concrete slabs, or placing
building paper under wood framing on concrete floors.
4.Gravity flow as a powerful means of moisture transport:
 • Liquid water can flow downward through various openings
when driven by gravity.
• Relatively large openings are required for gravity flow to
overcome capillary suction forces.
A.Examples of gravity-driven water flow:
• Water can flow through a screw hole in a plastic windowsill but
not out of a saturated brick.
• Gravity can drive rainwater into walls through leaky windows or
water through cracks in foundation walls.
B.Impact of gravity flow:
• Flows driven by gravity can lead to catastrophic failures if not
managed properly.
C.Utilization of gravity flow for managing water:
• Flashing can intercept and redirect water flows to prevent
damage.
• Condensation pans and disaster pans are used to manage liquid
water driven by gravity under appliances.
5.Multiple Transport Processes:
• Moisture movement in buildings involves several transport
processes working together rather than independently.
• Processes act in parallel and series to facilitate the movement of
moisture.
6.Groundwater Interaction:
• Liquid water from the groundwater can move upward through a
process called wicking.

References

Straube,Ph.D.,2002,https://www.researchgate.net/publication/271706272_Moi
sture_in_buildings