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HOMEOWNER TIP
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HVAC and Spray Foam Insulation Provided by Deep South Mechanical Spray polyurethane foam insulation has become a more popular choice for home builders in the Lake Area in recent years. The potential for better air quality, increased efficiency and lower electric bills attracts the 21st century home builder more and more. Compared to the cellulose and fiberglass homes of the past and present, spray foam completely changes the game. Spray foam transforms a home of several independent systems into a single cohesive organism. No longer are appliances, attic space, plumbing and the HVAC systems separate components that succeed or fail independently, but all are interconnected. If one component is not installed and designed with spray foam in mind, then the entire homes comfort, safety and efficiency can be diminished. The HVAC system is the most critical part of the equation when considering the move to spray foam. Spray foam creates an envelope around your entire home that drastically reduces the exchange of outside air and inside air. In normal circumstances, a traditionally insulated house will have the inside air replaced by outside air every 90 minutes to three hours. However, a spray foam house will exchange the air every five to ten hours. Therefore, it is easy to understand how a spray foam home can allow for a more even temperature that requires less energy to maintain. Unfortunately, a slower exchange of air can allow for diminished air quality and humidity issues if the HVAC system is not specifically designed for foam insulation. There are two main problems that foam houses in Southwest Louisiana face that rely solely on the HVAC system to address. First and foremost are higher humidity levels. A foam house is so easy to lower the temperature fast, that a system may reach set point in a few minutes but has not run long enough to properly dehumidify the air. Therefore, one may have 70 degrees inside temperature with a humidity level of 85%. This will not be comfortable. Dehumidification is always a priority for any home, but in a home with spray foam it is essential. Secondly, stagnant air can allow for severe air quality issues. This primarily occurs in the attic. In traditional houses, the attic is outside the insulation barrier and do not “share air” with your living areas. A foam house puts the attic inside the envelope. A huge advantage of this is your attic stays nearly the same temperature as your living room and puts the heat load on the roof rather than the ceiling. Nevertheless, stagnant air in the attic can cause damage to the HVAC system and create the perfect environment for mold. 44 DESIGN & BUILD 2022
So, what does the HVAC system need to address to ensure that your foam insulation home will perform as expected? Most importantly, is that the HVAC system installed is sized properly for the volume and square footage being conditioned. There are several options concerning brand and setup suitable for a foam house. However, the minimum level of equipment would be 16 SEER two-stage equipment. The inside air handler that circulates your air throughout the home must be variable speed. This means that the blower motor can run at different speeds based on the need at any given time. Furthermore, the outside unit must have at least a two-stage compressor. This allows the outside unit to operate at full capacity when needed, but also at a lower capacity to primarily dehumidify. Even with the right equipment, a poor installation can render it ineffective. The two main components that must be present in the installation are: the inside unit must have a return specifically installed to pull air into the air handler from the attic, and there must be a supply drop of conditioned air introduced at the highest point in the attic. Both items allow for air movement in the attic which addresses the stagnant air problem. The following are other things to strongly consider when building a home with spray foam insulation: • Thermostat with humidity controls. • Dehumidifier which is often considered a non-negotiable and installed in the attic. • Introducing fresh air directly into the HVAC system to create positive pressure in your envelope. • Multiple returns throughout the home, every hallway, and every bedroom. • Gas Furnaces should be avoided. If it is necessary, a specific furnace must be installed that can be identified by two PVC pipes exiting through the roof. Not the traditional single metal 4-inch exhaust. Spray foam is the premier method of insulation and when the HVAC system is paired and installed properly, there is nothing that can compare. Overall, spray foam insulation can take a home into the 21st century.
