Nate • 13 May 2025

Nate • 13 May 2025

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Abstract This case study examines the challenges and failures associated with Variable Refrigerant Flow (VRF) HVAC systems in high-rise condominiums. It highlights the importance of adhering to industry association standards, manufacturers’ installation instructions, and regular maintenance schedules. The study also discusses common site observations and design considerations for VRF system piping, emphasizing the consequences of inadequate piping support.


Introduction


Variable Refrigerant Flow (VRF) systems are increasingly used in high-rise condominiums for their efficiency and scalability. Despite their advantages, improper installation and maintenance can lead to significant challenges and system failures.


Industry Association Standards


The industry standards for VRF systems are set by organizations such as AHRI and ASHRAE. AHRI Standard 1230-2021 and 1230-2023 outline the performance rating of VRF systems. ASHRAE provides guidelines on the design, installation, and commissioning of VRF systems.


Manufacturers’ Installation Instructions/Requirements


Manufacturers like Hitachi, LG, Trane, and YORK provide detailed installation guides and technical catalogs for VRF systems. These documents emphasize the importance of proper installation practices, including adequate space for units, weight support, ventilation, and leveling.


Maintenance Schedules and Requirements


Regular maintenance is crucial for the longevity and efficiency of VRF systems. This includes semiannual maintenance such as changing filters, cleaning coils, checking refrigerant charge, and inspecting refrigerant lines. Some manufacturers and service providers suggest quarterly maintenance to ensure optimal performance.


Common Site Observations


  • Building Overview: High-rise condominium complex with multiple VRF systems.
  • Maintenance History: Maintenance began in December 2020, focusing on outdoor units (ODUs), heat recovery units (HRUs), and common area indoor units (IDUs). The history of the equipment is unknown.
  • Equipment Age: Manufactured in 2017.
  • Control System: A proprietary system that manages all VRF systems.
  • Piping Configuration: Rooftop system piping installed below ODUs.
  • Visible Installation Issues:
  • Missing Inverted Oil Traps: Pipe lengths that exceed the maximum 6.6 feet without required inverted oil traps, risking oil circulation issues and potential compressor and board failures.
  • Inadequate Piping Support: Rooftop piping lacks proper support, leading to sagging, bending, and potential leaks.
  • Inadequate or failed pipe insulation: Piping lacks proper insulation, leading to condensation problems, system inefficiencies, and potential leaks.
  • Incorrect Copper Linesets: Soft copper pipes used where hard drawn copper is recommended, risking damage to HRUs.
  • Inadequate Indoor Lineset Support: Linesets supported with zip ties, which do not provide sufficient support.


Design of Piping System for VRF Systems

Designing the piping system for a Variable Refrigerant Flow (VRF) system is a critical aspect that impacts the efficiency, performance, and longevity of the system. Here are the key considerations:

·        Pipe Lengths and Sizing: The maximum allowable vertical distance between an outdoor unit and its farthest indoor unit is typically around 150 feet, and the maximum permissible vertical distance between two individual indoor units is approximately 45 feet. The maximum actual refrigerant piping lengths allowable between outdoor and farthest indoor units can be up to 490 feet. Pipe diameters should be selected based on the system’s capacity requirements and the manufacturer’s specifications.

·        Expansion and Contraction Loops: Due to temperature variations, refrigerant pipes can expand and contract. To accommodate this, expansion loops or offsets are used. These loops allow for the natural movement of the pipes without causing stress or damage.

·        Oil Traps: In VRF systems, only inverted oil traps are allowed. Oil traps are crucial as they prevent oil from getting trapped in the system, which could lead to compressor bearing losses and system inefficiency.

·        LATS Program: The LG Air Conditioning Technical Solution (LATS) program is often used during installation to ensure accurate system design. It helps in calculating refrigerant piping diameters, refrigerant quantities, and piping lengths based on the selected model and user-typed distance.

·        As-Built Drawings and Calculations: After installation, it is essential to provide as-built drawings and calculations. These documents should reflect the actual installed conditions of the VRF system and include details such as equipment locations, piping routes, and control strategies. They serve as a reference for future maintenance and any system modifications.

Incorporating these elements into the design of a VRF system’s piping will help ensure that the system operates efficiently and effectively over its lifespan. It’s also important to adhere to the manufacturer’s guidelines and industry standards throughout the design and installation process.

Inadequate piping support in HVAC systems can lead to a range of serious issues. Here are some of the consequences:


  • Leaks and Cracks: Excessive stress on the pipes due to inadequate support can cause leaks and cracks, which may lead to water damage and the need for costly repairs.
  • Catastrophic Failures: In extreme cases, the lack of proper support can result in catastrophic failures of the piping system.
  • Sagging and Misalignment: Without proper alignment and positioning, pipes can sag or become misaligned, affecting the system’s efficiency, and potentially causing further damage.
  • Pooling Corrosion: Improper spacing of pipe supports can lead to sagging or drooping pipes, which in turn can cause pooling corrosion and even collapse of the pipes.
  • Galvanic Corrosion: Metallic guides without lining can lead to galvanic corrosion if pipes and supports are made of dissimilar metals.
  • Crevice Corrosion: Metal-to-metal contact can create small divots that house microbes, leading to crevice corrosion and eventual failure of pipes or supports.
  • Metal-to-Metal Friction: This friction can wear down surfaces, weakening the pipe or support and increasing the risk of rupture.
  • Noise and Vibration: Inadequate support can also lead to increased noise and vibration, which can be a nuisance and potentially cause structural damage.
  • 

Proper pipe support is critical for the safe and efficient operation of HVAC systems. Ensuring that installation and maintenance adhere to industry standards and manufacturers’ guidelines is essential to prevent these issues.

Conclusion

The common site observations of VRF systems exhibit several installation and maintenance issues that could lead to system failures. Adherence to industry standards, manufacturers’ instructions, and regular maintenance schedules is essential to prevent these problems and ensure the systems’ longevity and efficiency.

Case Study: Condo Water Damage Mystery Solved – Exhaust Ventilation Imbalance, Not Roof Leaks.

by Nate • 4 November 2025
Project Overview The subject of our case study is a two-story wood-framed residential condominium, equipped with a variety of exterior claddings such as stone veneer, stucco, wood panel siding, and wood trim. The structure features flange-mounted metal-clad windows and a combination of standing seam metal, flat roofs covered with TPO, and concrete tile roofing. Following exterior cladding repairs and a flat roof replacement in 2021, the building encountered water damage issues, which we will explore in this case study. Incident Report In the winter of 2022, the owner of a condominium suite reported water damage within their unit. A subsequent report by the Community Manager detailed the water loss and remedial actions that had been implemented. Notably, inspections conducted by a roofing company, and other service providers, indicated that recent (2021) cladding and roofing work, performed on the exterior of the building was not the source of the leaks, and that the inspections were inconclusive, but recommended replacing the concrete tile roofing system above the bedroom where the water stains in the ceiling were present. Investigation Findings Construction Science Forensics (CSF) investigation revealed moisture staining on the ceilings of two bedrooms. The stains, though dry during the visit, suggested condensation issues near exhaust vents and roof edges. A flood test and invasive inspection ruled out active leaks from the exterior cladding and roofing systems. CSF performed a preliminary test of the bathroom exhaust fans and clothes dryer exhaust systems. When the clothes dryer was turned on, CSF observed that the dryer fan was overpowering the bathroom exhaust fans. Refer to photograph. This condition is causing warm moist air from the dryer exhaust to be drawn back into the condominium through the bathroom exhaust vents at the roof outlets. The warm moist air is then converted to liquid water in the form of condensation within the exhaust ducts above the 1st floor bedroom. The homeowners reported that there were intermittent leaks in the ceiling of the cupola section of the condominium above the stairwell. CSF observed that there was a master bedroom exhaust duct and vent directly above this area. CSF observed that the backdraft damper (flapper) was stuck shut by a bent exterior bird screen. This condition will contribute to condensation and water within the exhaust duct that will leak into the attic, and condense on cold surfaces. Key Observations Master Bedroom Ceiling: Staining adjacent to a bathroom exhaust vent, caused by condensation around the bathroom exhaust duct. 1st Floor Bedroom Ceiling: Staining near the roof edge, believed to be due to condensation within the bathroom exhaust duct systems. Reverse Airflow Issue: The clothes dryer was overpowering bathroom exhaust fans, leading to cold air being drawn from the exterior into the interior through the bathroom exhaust duct, causing condensation within and around the exhaust ducts. Cupola Section Leaks: A stuck backdraft damper and improperly sealed ductwork contributing to condensation within the exhaust ducts, which originally appeared to be a roof leak. Recommendations CSF recommended addressing the condensation issues by ensuring proper ventilation within the attic spaces, and exhaust systems. Installation of a passive make up air supply to neutralize the negative pressure from the clothes dryer. Additionally, CSF recommended conducting testing and balancing of the HVAC system wholistically to account for building pressurization changes caused by the fireplace flu, the clothes dryer, and the multiple exhaust fans (Kitchen, bathrooms, laundry room). Conclusion This case study highlights the importance of thorough inspections and the complexities of diagnosing water damage in residential buildings. It underscores the need for proper maintenance and the potential impact of overlooked details such as exhaust system balance and ductwork integrity. Here are a few additional considerations that might be useful when dealing with water damage in buildings: Actionable Insights: · -Facility Managers: Add exhaust CFM testing to your PM checklist. · -Contractors: Verify dryer + bath fan balance before final sign-off. · -HOA Boards: Budget for building pressurization audits every 3–5 years. Bonus: 5 Condensation Prevention Tips: · 1. Inspect Exhaust Terminations Annually – Clear bird screens, check dampers. · 2. Insulate Ducts in Unconditioned Spaces – Stop cold-surface condensation. · 3. Balance CFM Across Appliances – Dryers shouldn’t dominate bath fans. · 4. Monitor Indoor Humidity (40–50% RH) – Use dehumidifiers in winter. 5. Hire Building Science Experts Early – Avoid costly misdiagnosis.

Construction Cost of Repair Estimates: Xactimate vs. Restoration Contractors

by Nate • 7 June 2025
This article compares two primary methods of estimating repair costs for property damage: Xactimate estimates and restoration contractor estimates. It highlights their strengths and weaknesses to help property owners navigate insurance claims effectively.

The Role of Construction Forensic Experts in Water Loss and Building Failure Claims: Ensuring Transparency and Cost Control

by Nate • 15 May 2025
Water loss and building failure claims are significant challenges for property owners, often leading to high costs and emotional stress. Construction forensic experts play a crucial role in investigating these claims, ensuring transparency and cost control, in contrast to standard mitigation contractors who may cause unnecessary damage and inflated repair costs.

WETTING AND DRYING OF WOOD STRUCTURES DURING CONSTRUCTION: A GUIDE

by Nate • 13 May 2025
The blog post discusses the wetting and drying processes of wood in construction, focusing on adsorption, absorption, and desorption rates, moisture content requirements for various materials, and building code standards for drying materials before covering. Key points include: - **Wetting and Drying of Wood**: Wood undergoes wetting (absorbing water) and drying (evaporating water) cycles during construction, influenced by wood type, environmental conditions, and moisture content. - **Adsorption, Absorption, Desorption**: Adsorption involves molecules adhering to a surface, absorption is mass transfer into a material, and desorption is the release of these substances, with rates depending on temperature, pressure, and material properties. - **Moisture Content Requirements**: Materials like concrete, insulation, drywall (5-12% moisture), plywood/OSB (≤19%), and gypsum sheathing/gypcrete (≤1-5%) have specific moisture thresholds for optimal performance. - **Code Requirements**: Building codes mandate drying ma

CASE STUDY: EASEMENT AGREEMENT AND DEVIATION ANALYSIS USING ADVANCED 3D TECHNOLOGY

by Nate • 13 May 2025
This case study explores the use of advanced 3D technology for deviation analysis in construction, focusing on an easement agreement between two property owners. The agreement required the hotel developer to restore any damage caused to the existing building during construction. To assess deviations, experts utilized 3D digital twins, laser scanning, drone photography, crack gauges, and floor level manometer surveys. These tools provided precise measurements and visualizations to track structural shifts and foundation movements. The findings pinpointed areas of damage, allowing the building owner to present clear evidence to the hotel developer. As a result, the developer agreed to cover the necessary repairs. The study highlights the importance of technology in enforcing easement agreements and maintaining structural integrity. It also demonstrates how digital twins and laser scanning can revolutionize construction analysis, ensuring safer and more resilient buildings.

Air Leakage and Condensation in Buildings: A Brief Guide

by Nate • 13 May 2025
This article explores the impact of air leakage and condensation on building performance, emphasizing the need for energy-efficient and durable structures. Air leaks contribute to energy loss and moisture-related issues, making proper sealing crucial. Dew point analysis helps predict condensation risks, preventing mold and structural decay. Managing humidity levels indoors and outdoors ensures comfort and prevents condensation buildup. Thermal bridging—where heat bypasses insulation—can lead to energy inefficiencies and moisture problems, requiring continuous insulation to mitigate its effects. Decoupling wall assemblies from attic and parapet structures further reduces air leakage and moisture transfer, improving energy performance. Additional strategies like building envelope commissioning, balanced ventilation systems, climate-responsive design, and thermal imaging enhance building durability. Proper material selection, regular maintenance, and occupant awareness also play vital roles in minimizing air lea

Case Study: Hygrothermal Analysis of a Pacific Northwest Apartment Complex

by Nate • 13 May 2025
This case study investigates the hygrothermal issues of a five-story apartment complex in the Pacific Northwest, focusing on moisture management challenges and their implications. Hygrothermal Challenges: The study identifies persistent water leaks around windows and wall penetrations as primary issues affecting the building's moisture management. 1 Methodology: Data logging of interior temperature and humidity, analysis of historical weather data, and pressure testing were employed to understand the environmental conditions impacting the buildings. 2 3 Findings: Key findings include inadequate sealing at window junctures, damaged exterior sheathing, and occupant moisture loading exceeding the wall assembly's drying capacity. 4 5 Discussion: The analysis reveals that the interplay between building design, occupant-generated moisture, and environmental factors contributed to the moisture issues, highlighting the need for effective humidity management. 6 Consequences: Prolonged moisture exposure

ENHANCING CONSTRUCTION PLANNING & PROJECT SUCCESS WITH BUILDING ENVELOPE REFERENCE MANUALS (BERM)

by Nate • 13 May 2025
This article highlights the importance of the Building Envelope Reference Manual (BERM) in construction planning. The building envelope plays a crucial role in energy efficiency, structural integrity, and occupant comfort, making proper design and maintenance essential. BERM provides best practices for selecting materials, construction techniques, and climate adaptation strategies to ensure durability and resilience. It also aligns with sustainability standards, helping professionals create energy-efficient and eco-friendly buildings. By using BERM, architects, engineers, contractors, and building owners can collaborate effectively to meet high-performance standards while avoiding costly errors. As the construction industry evolves, BERM remains a vital resource for ensuring long-lasting, well-designed structures.

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by Nate • 11 May 2025
This document discusses the roles and differences between general contractors and specialty contractors in construction projects, emphasizing their unique contributions and challenges, as well as the importance of forensic experts in resolving disputes. General Contractors Overview: General contractors manage entire construction projects, coordinating schedules, budgets, and subcontractors while ensuring compliance with regulations. They provide holistic oversight but may lack specialized expertise, leading to higher management fees. 1 2 Specialty Contractors Role: Specialty contractors focus on specific trades, offering deep expertise in areas like plumbing or electrical work. They are cost-effective for targeted tasks but may create coordination issues if multiple specialists are involved. 3 4 Choosing the Right Contractor: The choice between general and specialty contractors depends on project scope, budget, and risk tolerance.