Service and Repair Plumber (SRP)

Correct: In climates with high outdoor humidity, the selection of an ERV is the most effective control. ERVs are designed to transfer latent heat (moisture) in addition to sensible heat (temperature). By removing moisture from the incoming air and transferring it to the exhaust stream, the ERV reduces the dehumidification load on the air conditioning system, prevents mold growth, and maintains occupant comfort.

Incorrect: HRVs are less effective in humid climates because they only transfer sensible heat, meaning they do not address the moisture content of the incoming air, which can lead to high indoor humidity. Exhaust-only systems create negative pressure that can pull humid, unfiltered air through the building envelope, risking condensation and structural damage. High-MERV filters improve air quality by removing particulates but do not provide fresh air exchange or moisture control.

Takeaway: Selecting the appropriate recovery ventilator (ERV vs. HRV) based on regional climate is essential for managing latent heat loads and ensuring long-term building durability and indoor air quality.

Correct: In residential ventilation design, particularly under standards like ASHRAE 62.2, the total required ventilation is a combination of mechanical ventilation and natural infiltration. As building envelopes become tighter, the contribution of natural infiltration decreases, necessitating a more robust and accurately calculated mechanical ventilation rate. An auditor must verify that the load calculations account for this relationship to ensure that the home receives adequate fresh air to dilute pollutants and manage moisture, preventing structural damage and health issues.

Incorrect: Relying on occupant-controlled windows is incorrect because it is inconsistent and does not meet the requirements for continuous or predictable ventilation in modern codes. Using sensible heat recovery efficiency as the sole metric is a failure of design because heat recovery relates to energy efficiency, not the volume of air required for pollutant dilution. Standardizing exhaust-only systems is inappropriate because such systems may cause back-drafting in combustion appliances or fail to provide balanced pressure in very tight or specific climate-controlled environments.

Takeaway: Effective residential ventilation design requires balancing mechanical systems with building envelope airtightness to ensure consistent indoor air quality and moisture management.

Correct: Evaluating the documentation of contractor concerns is the correct approach because it directly addresses the risk of inadequate ventilation (IAQ and moisture) and the communication failure between the lender, contractor, and client. In the context of internal auditing and residential design, ensuring that technical risks are properly disclosed and that building codes (like ASHRAE 62.2) are met is essential for risk management and ethical compliance.

Incorrect: Terminating the contracts of whistleblowers is an unethical and likely illegal retaliatory action that ignores the underlying safety risks. Increasing interest rates to cover liability fails to address the root cause of the ventilation deficiency and does not fulfill the auditor’s duty to evaluate control failures. Limiting the audit scope to financial disbursements ignores the significant operational and compliance risks associated with the lender’s specific loan requirements for building envelope tightness.

Takeaway: Internal auditors must evaluate whether technical risks and communication failures regarding indoor air quality and ventilation are properly managed to ensure compliance with safety standards and ethical obligations.

Correct: In modern high-performance housing, the building envelope is sealed tightly to prevent energy loss. This eliminates ‘natural’ infiltration (leaks). Without mechanical ventilation, indoor pollutants like VOCs, CO2, and moisture from daily activities accumulate, leading to poor indoor air quality and potential structural damage from mold. An HRV ensures this exchange is controlled and energy-efficient by recovering heat from the exhaust air.

Incorrect: The suggestion that an HRV is a backup for a furnace is technically incorrect as ventilation and space heating are distinct functions. Claiming mechanical ventilation is for aesthetic standardization ignores the fundamental health and safety purpose of air exchange. Stating that the primary issue with windows is a lack of sensor measurement misses the core problem of ‘build tight, ventilate right,’ which is about the physical lack of air exchange in a sealed envelope rather than just a measurement or manual override issue.

Takeaway: Mechanical ventilation is essential in modern airtight homes to provide controlled air exchange and moisture management that natural infiltration can no longer provide.

Correct: In modern residential building codes and standards such as ASHRAE 62.2, as building envelopes become increasingly airtight (typically below 3.0 ACH50), natural infiltration is no longer considered a reliable source of fresh air. Regulatory compliance requires a ‘principal’ mechanical ventilation system capable of continuous operation. This ensures that indoor air quality is maintained through a controlled and verifiable rate of air exchange, independent of weather conditions or occupant behavior, which is critical for removing indoor pollutants and moisture.

Incorrect: Relying on natural infiltration or the stack effect is insufficient for airtight homes because these forces are inconsistent and often fail to provide minimum air changes. Demand-controlled exhaust based solely on humidity does not address other pollutants like VOCs or CO2 and does not meet the requirement for a continuous principal ventilation source. Recirculation and air cleaning improve air quality by removing particulates but do not provide the necessary dilution of indoor contaminants or the oxygen replenishment required by ventilation regulations.

Takeaway: For airtight residential structures, regulations mandate a continuous mechanical ventilation system to ensure a consistent and verifiable supply of outdoor air regardless of natural infiltration.

Correct: In airtight modern homes, an exhaust-only ventilation system creates a negative pressure environment. This forces replacement air to enter the building through any available gaps in the envelope. Because this air is unconditioned and enters at random locations, it often creates localized cold drafts and temperature imbalances, which significantly reduces occupant thermal comfort and satisfaction compared to balanced systems that temper the incoming air.

Incorrect: Option B is incorrect because building codes generally do not mandate positive pressure in residential settings; in fact, excessive positive pressure in cold climates can drive moist indoor air into wall cavities. Option C focuses on energy consumption and regulatory limits rather than the direct occupant comfort and satisfaction experience. Option D describes a common operational failure of intermittent systems, but it does not address the fundamental comfort issue of drafts and unconditioned air infiltration inherent in the exhaust-only design.

Takeaway: Exhaust-only ventilation in airtight homes often leads to occupant discomfort due to uncontrolled, unconditioned air infiltration caused by negative pressure.

Correct: ERVs (Energy Recovery Ventilators) transfer both sensible heat and latent heat (moisture) between the intake and exhaust air streams. In a humid summer, an ERV will transfer much of the moisture from the incoming outdoor air to the outgoing exhaust air, reducing the latent load on the building. However, an ERV is not a dehumidifier; it cannot remove moisture from the indoor air to maintain a specific set point. If the outdoor humidity is high enough, the air entering the home will still contain more moisture than the desired indoor state, and if the air conditioning system is not sized to handle this remaining latent load, indoor humidity will rise.

Incorrect: Option B is incorrect because bypass dampers are typically used for ‘free cooling’ (economizer mode) to bypass heat exchange when outdoor temperatures are favorable, not specifically to manage moisture re-introduction. Option C is incorrect because while sizing is important, increasing the air volume (ACH) in a humid climate would actually introduce more total moisture into the building, exacerbating the problem. Option D is incorrect because while VOCs can affect air quality, they do not typically cause a mechanical failure of the desiccant core’s ability to transfer water vapor.

Takeaway: ERVs reduce the moisture load from ventilation air but require supplemental dehumidification in humid climates to maintain indoor relative humidity within healthy limits.

Correct: A failure of the active frost control mechanism is specifically identified when the system logic fails to execute the defrost sequence. In many HRV designs, the defrost sequence involves de-energizing the supply fan so that warm exhaust air can melt ice on the core. If the supply fan remains energized when the temperature is below the frost threshold, the control sequence has failed, leading to ice buildup and potential core damage.

Incorrect: Condensate overflowing the tray typically indicates a physical blockage in the drain line or a leveling issue rather than a control logic failure. A gradual increase in static pressure over weeks is a classic sign of filter loading or particulate accumulation on the core, which is a routine maintenance issue. An intake damper remaining open during high humidity relates to latent load management or indoor air quality settings, but it does not directly diagnose a failure in the frost protection sequence required for cold-weather operation.

Takeaway: Distinguishing between control logic failures and physical maintenance issues is critical for accurately diagnosing ventilation system malfunctions and assessing the effectiveness of mechanical risk controls.

Correct: In airtight homes (0.6 ACH50), mechanical ventilation is the primary method for removing Volatile Organic Compounds (VOCs), CO2, and moisture. Prioritizing energy conservation or battery longevity over minimum ventilation rates mandated by standards like ASHRAE 62.2 or local building codes introduces significant health risks and potential for structural damage due to moisture accumulation.

Incorrect: The loss of sensible effectiveness is a secondary performance metric and does not represent the primary life-safety risk associated with inadequate air exchange. There is no regulatory requirement that renewable energy systems must operate independently of HVAC; in fact, smart integration is encouraged as long as safety minimums are maintained. Ventilation ductwork is not designed to provide cooling for solar inverters, and reducing airflow would generally decrease rather than increase static pressure in the distribution system.

Takeaway: Mechanical ventilation rates in airtight homes must always meet minimum health and safety standards, regardless of energy conservation or renewable energy management goals.

Correct: In cold climates, HRVs frequently produce condensate as warm, moist exhaust air is cooled by the incoming fresh air. A proper drainage system must include a consistent downward slope to ensure gravity flow and a P-trap. The P-trap is critical because the HRV cabinet operates under pressure; without the trap, the pressure differential would either prevent drainage or allow unconditioned air and potentially hazardous sewer gases to be drawn into the ventilation system.

Incorrect: Connecting condensate to exhaust ducts leads to moisture accumulation in the ductwork, causing mold and corrosion. While ERVs transfer moisture, they can still produce condensate in extreme cold or high-humidity conditions, and assuming they never need drainage is a design failure. Terminating condensate into a crawlspace or attic introduces excessive moisture into the building structure, which can lead to rot and indoor air quality issues regardless of vapor barriers.

Takeaway: Proper condensate management requires a sloped, trapped drainage system to ensure moisture removal while protecting the unit’s pressure balance and indoor air quality.