
HVAC and Indoor-Air Quality
This article details the HVAC and indoor air quality strategies implemented in the FHB House in Kansas, a custom midcentury modern–inspired home prioritizing comfort and efficiency. The builders, Travis Brungardt and Joe Cook of Catalyst Construction, discuss their choices for ducting, zoning, and air treatment equipment to achieve a high-performance living environment.
The project incorporates flex ducting in certain areas, acknowledging that while hard piping is generally preferred for optimal airflow due to less friction loss, flex ducts offer advantages in material cost reduction, easier installation around complex structural elements like trusses, and noise attenuation. This decision balances performance with budget and occupant comfort. The house features a two-zone HVAC system to effectively manage temperature across different areas. One system serves the east end of the house, including the kitchen and a vaulted living/dining space, with its thermostat strategically placed in the kitchen. The second system is dedicated to the primary suite and bedroom core on the west end, serving three main-floor bedrooms and two basement bedrooms. Each zone has its own thermostat to provide localized temperature control, ensuring comfort for occupants in their respective living and sleeping areas.
Moisture management is a critical aspect of the home's indoor air quality strategy. In the primary suite, which includes a double vanity, large shower, and bathtub, a Fantech 6-inch fan provides source control for humidity removal during showers. The Honeywell thermostat in this area also features a humidity-sensing capability, allowing for integrated control with the air conditioning system to maintain appropriate humidity levels. The article highlights the use of Benjamin Moore vapor-blocking paint in the vaulted space on the east end, which is identified as a primary moisture concern. To address this, a dedicated Santa Fe 120 dehumidifier is installed on the east end unit, serving the kitchen, the large vaulted space, and a portion of the basement. This dedicated dehumidification ensures that potential vapor and condensation risks in high-humidity areas are effectively mitigated.
The mechanical room houses high-efficiency forced-air units. The zone system is controlled by a Honeywell Home HZ432 panel, which modulates electrically controlled dampers to direct airflow based on thermostat calls. This allows for efficient heating and cooling of specific zones. Air filtration is achieved using MERV 11 filters, chosen to balance effective particle removal with maintaining adequate airflow. While MERV 13 filters could be used, the builders opted for MERV 11 to prevent excessive flow restriction, ensuring clean air delivery without compromising system performance.
Humidity addition is also addressed with Honeywell humidifiers on both HVAC units, acknowledging the health risks associated with insufficient indoor humidity, particularly in the dry Kansas City winters. The Stiebel Eltron on-demand water heater provides continuous hot water at 120°F, eliminating recovery time and reducing the risk of Legionnaires’ disease. For fresh air intake in the airtight home, an Energy Recovery Ventilator (ERV) is installed. The ERV is crucial because the house achieves a high level of airtightness (0.70 air changes per hour) far exceeding the local code requirement of 3 air changes per hour, making mechanical ventilation essential to prevent stale indoor air. The ERV core exchanges thermal energy between outgoing stale air and incoming fresh air, preheating or precooling the fresh air to minimize energy loss. The ERV is strategically placed to serve the bedroom core, where occupants spend significant time, ensuring a continuous supply of fresh, conditioned air throughout the most occupied areas of the house.
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