Hello - I've spent a good chunk of time reading and perusing threads on here, and in just a few hours, feel so much more comfortable trying to understand the quotes I have for a new HVAC system. That said, I'm hoping a few of you can provide some insight into what I'm looking at.
House: Denver (so 0 deg for winter, 92 for summer are the numbers I'm supposed to be shooting for, regardless of the fact it has been in the upper 90's for 2 weeks now ), 1-story, solid brick (built in 1911), ~1,000 sq feet main floor, basement that is 80% finished. New double-paned vinyl windows through entire 1st floor, a few older windows remain in the basement. 4" of insulation currently in the attic, which will be upped to 12" soon. Garage is detached, so no worries there.
Replacing: There is currently no A/C, just central heat from a 35 year old furnace. I'll be adding in A/C and replacing the furnace.
Quote 1 - Installer recommended 80,000 BTU Trane XV95. Load calculation done at 50,000BTU (assuming 12" insulation in the attic). According to him, I need an 80,000 BTU furnace because 80,000 * 95% (furnace) * 83% (altitude adjustment) is 63K BTU. My other option (which he says is priced almost exactly the same) is a 60,000 BTU Train XV95. The same calculation above brings that to only 47K BTU, which falls under the load calc of 50K. In addition, he recommended a high-efficiency Trane A/C unit, but I'm unsure of the model number.
Quote 2 - Installer recommended 80,000 BTU 95% Armstrong furnace. I didn't get the detailed load calcs from him, so I can't compare directly. Also recommended a high-efficiency A/C unit.
Both installers have all their qualifications. And I like both of them. The main difference seems to be Trane vs Armstrong, and the fact the Armstrong quote is about 30% less than the Trane. Granted, it seems Trane has a better track record, but I'm able to buy a 10 year P&L warranty on Armstrong for about the same price as I am with the Trane, so I'm wondering if there is any real downside to saving the 30%?
Also, my concern is I've read SO many comments regarding how installers often want to sell you something bigger than you need, simply because they don't want you calling them because your unit can't handle the load in a cold snap. What kind of efficiency do I stand to lose by purchasing a slightly over-sized furnace? (I mean, it would be nice if the furnace could keep up during -10 degree cold snaps, but I'm trying to understand the loss in efficiency I'm paying for....) In your opinions, is an 80K furnace for what I'm describing (given the 50K load calc) way over-sized?
Any other comments or advice would be welcomed as well. Thank you so much for your help.