I'm a new guy here, an occasional lurker for months, just registered, and I even read the rules, so here goes. Hopefully this isn't too long.
We live on a lake in the Ft.Worth, TX area and have a 40-year old detached guesthouse/apartment that is being increased from 600 SF to 900SF, all under the same roof. My 80-year old parents in-law are moving into this guesthouse and paying for all remodeling, about 37K in all. We have hired a General Contractor who we have known for 24 years, and we know his work (built our previous house) and we trust him. We told him up front that cost was very important on all items of this remodel.
The guesthouse is a wood frame structure with 8-foot ceilings and 6-inch joists, insulated with fiberglass, and still has the original flat roof, covered in asphalt and gravel. A sloped/pitched roof was added later. Our lot slopes about 20-25 degrees, I think, and a 4-foot retaining wall surrounds 2 sides of this guesthouse and is about 30-inches from the house walls. We plan to have the exterior re-sided with Hardie and Tyvek and we currently have fairly new Simonton vinyl double-pane windows. There are large native oaks on the east and south sides, extending some to the west.
The current electric A/C / heater is a 2-ton unit, and cools and heats the 600SF pretty good considering there is only one intake and one outlet air vent in the main room which is over 500SF. The outside compressor unit is a 1980s Janitrol and the air handler is Airtemp from who knows when.
Included in the A/C bids for this remodel job is running six new R-6 supply ducts to new vents in various areas. The air handler will be on an outer wall of the guesthouse, and the compressor unit will be right outside that wall, probably about six feet away. The parents-in-law didn't want a heat pump, but that may not be out of the question.
The GC gave us a good bid on a 2.5 ton 14 SEER Lennox, which seems a little on the high side as far as capacity, IMO. The Lennox condensing unit is the 14ACX using R410, and the air handler the CBX26UH. 5-year warranty on compressor. I didn't specify a warranty requirement to GC in the beginning so I just found out the warranty. He's trying to keep costs low.
The local A/C guy we want to use gave us bids on 2-ton Rheems, one convential A/C and the second a heat pump. While we were talking before the bids came back, he said he thought a 1.5 ton should be sufficient, but his bids came back with 2 tons. His models on the conventional A/C are the RANL024JAZ condensing unit and the RHLLHM2417JA air handler, overall 15 SEER. On the heat pump, he offers a RPNL024JAZ and same RHLLHM2417JA air handler, 14 SEER . Both units have a 10-year compressor warranty, per my request before bidding. Both have 10KW strip heat.
I realize these units are pretty much basic units, but under the circumstances, they are what we are looking for. Since I can't quote prices or comparisons, I hope I can get away with saying that the Lennox bid is about 76% the cost of the conventional Rheem A/C unit, even with the Lennox at .5 ton more. The Rheem heatpump is a few hundered dollars more than the conventional Rheem A/C.
Ok, here are my concerns/questions if you haven't gone to the next thread by now. Our GC keeps mentioning trying to get to a 30 degree difference factor, I guess between outside temp and inside. But I gotta tell ya, the old unit we have kept the guesthouse comfortable in the Texas summers and in the winter. Also, my 80-year old parents in law are cold natured these days. I'm a little worried about the 2.5 Lennox unit not running enough to remove the humidity, especially here by the lake, given the energy efficiency (maybe not) of the guesthouse, and surrounding ground on two sides of the building, and closeby large trees.
I guess my main questions are should I go with the 2.5 ton Lennox bid with 5-year compresssor warranty or maybe get a bid on a 2.0 Lennox with a longer compressor warranty to see if costs come out about the same. Or, take the GC's current 2.5 bid and check into a Lennox extended warranty if in-laws agree. I think I prefer the Rheem unit, but its not my money being spent. Not sure if I should ask for another Rheem bid for something with a 5-year compressor warranty to better compare to the Lennox bid. I guess it all boils down to what tonnage would work best in this situation, Lennox brand versus Rheem brand, and the warranties.
Sorry this was so long. I really would appreciate any thoughts, opinions, questions, or recommendations.