foam insulation

[ocfd47543]

hello my name is jason,

i am working closely with a friend(builder) building a 3000 sq ft home. i opted for foam insulation and zero clearance wood burning stove. the idea being to heat most of the house with the stove. the hvac contractor (supposedly knew) i was foam insulating but now says he didnt know. we went with an 80% lennox unit with the thought we didnt need a 90% due to the stove. the insulation guy told me i needed a 90% because of the foam and fresh air issues. i have the feeling my builder and/or the hvac guy wont say they made a mistake. now my builder states i can build plywood boxes over my units and pipe in fresh air for the 80% unit. sounds funny to me.

if anyone knows what i need to do please help?! thank you

[Freon]

Whether it's a 100,000 BTU input furnace that's 80% or 90 % efficient, you will always need the same amount of combustion air. The only difference is your 80% furnace will run longer. The difference in the efficiency number is due to the heat exchanger differences, not the gas combustion efficiency. However you also don't have many gadgets to break and cause headaches. I'm a believer in the KISS philosophy having seen how many well-intended "improvements" can come back to cost more in repairs than they save. Theduke has given you good information about getting the required combustion air. I wouldn't worry about the furnace you have. As long as it's sized right, you'll be happy.