I did an inspection on a home from 2007. The homeowner removed the blown in insulation and hired someone to install foam insulation at the roof sheathing. They completely sealed the attic including foaming the gable end vents (as seen in the first/foamed picture). They did not make any changes to the gas furnaces which are now installed in a sealed attic. Typically when I’m in newer construction attics with no ventilation because of roof sheathing insulation (typical in the Phoenix area) the gas furnaces will be installed with a fresh air vent and exhaust vent through the roof sheathing insulation and roof (as seen in the second picture).
I recommended further evaluation by a licensed contractor and HVAC contractor to evaluate combustible air and because the gable end vents had evidence of leaking from the interior of the house. (I’m assuming the gable end vents weren’t properly sealed before foaming the attic and the water is running down the foam to the interior.)
This is the first time I’ve come across this situation. Am I missing something? Since the attic is now sealed at the roof sheathing the gas furnaces are now getting “Air from Inside the Dwelling” ?
From InterNACHI: All Air from Inside the Dwelling
If all combustion air is taken from the inside of the dwelling, then two permanent openings should be installed. One opening should be within 12 inches of the top and one within 12 inches of the bottom of the space. Each opening shall have a free area equal to a minimum of 1 square inch per 1,000 BTU-per-hour input rating of all appliances installed within the space, but not less than 100 square inches.
I apologize in advance, this is my first post and I’m not sure what I am doing. Thank you.