Ian,
According to ASHREA standards, residential dwellings must have a minimum of 0.35 air changes per hour. This means approximately every 3 hours your home should have a complete new set of outside fresh air. This is important for many reasons to include breathing air, combustion air, diluting indoor pollutants like cleaning solutions. As well as moisture build up concerns. To calculate whether or not a house fits this minimum ventilation requirement we must perform a door blower test to see exactly how much the house is "leaking" to the outside. Once we have this number we must calculate the volume of the house to determine exactly how many cubic feet of air the house contains. This number divided by how much the house "leaks" will tell us how often the air is being changed over. Currently in your home, which is approximately 17,500 cubic feet of air, the air is ventilating at a rate of 0.09 air changes per hour with a test out door blower number of 540 cfm50. Which is remarkably low. You may want to discuss with an HVAC contractor what steps may be necessary to facilitate proper ventilation. Now the solution to the problem isn't to just open holes to the outside in order to gain adequate ventilation. Because although the total leakage to outside for the home would be sufficient, it would be localized to certain areas of leakage, rather than distributed throughout the home evenly. In order to evenly distribute the incoming fresh air you would have to use some sort of mechanical ventilation. In our climate zone we recommend this be accompanied with a whole home dehumidifier. When the house is already tight, and then the insulation is upgraded, the AC will work less causing it to dehumidify less. This coupled with humid air being brought in from outside as required by code could cause a moisture problem. The whole home dehumidifier cures this issue while also bringing in fresh air, as well as filtering the indoor air with a Merv 13 filter. A Merv 13 filter is a far superior filter to the thin return grill filters the typical AC system contains. This makes for a much cleaner indoor air environment. Myself and Ira both have the AprilAire systems in our homes, and I wouldn't own a home, in the future, without one. Same goes for spray foam insulation. Remember we want to eliminate the localized unwanted leakage to outside, which causes uneven temperatures from room to room, and replace it with controlled mechanical ventilation. Which is evenly distributed throughout the home. Making for better air quality. And proper functioning appliances. As well as a more energy efficient home. Sincerely, Corey Yates Sunlight Contractors LLCDirect: 504-496-2813 Email: Cyates@sunlightcontractors.com
