I put a 900 sqft addition on my earth home. I decided that now was the time to also add an HVAC system to the old part of the house while I was at it. The existing home was 1100 sq ft with 8ft ceilings. I ran a 12" round trunk line with 6 8" drops feeding the various rooms in the existing house. The new additon is above the garage and will be fed by its own 8x14 trunck line and will have 6 8inch drops on it as well. The sqft of the new additons is 900 sq ft. I had it narrowed down to 1 contractor and I installed the duct work per his calculations. He had given me a "guestimate" on what the rest of the new install was going to cost. It sounded reasonable to me and I told him I would contact him when I was closer to needing his services. Well I called him back out a few weeks ago and he came and looked things over. I then receive his written estimate in the mail and it is substantially higher that what his original "guestimate" was.
So now here I am ready to go but not really being able to afford what I thought I could afford. My plumber recommended a friend of his that does side work. He came out and looked it over. His recommendation was a 2.5 ton unit 16 seer with a 3 ton blower(same as the first guy). He also wants to run automatic dampers on each trunk line to create 2 zones and he wants to do it for a bit less than the 1st guy. Guy number 2 is installing tappan or any other brand I want from one of the local wholesale houses. The first guy is using lennox. So what is a guy to do? Also are there any things I should be concerned about considering sizing between a single zone system and a dual zone system?