Putting an addition on an old house. Basement + 2 Stories + walkable attic for future use (sloped hip roof ceilings). Looking at 1 system in basement for finished basement and main floor. 2nd system in attic for upstairs br's and future attic teen room/office/walk up storage.
Will have foamed roof deck )to R-30-35 and air tight) thus attic equip. will be in semi conditioned space. Putting in Solar thermal and p.v. Putting in mod con boiler and radiant under floor heat - staple up and some radiators in old house parts with no exposed joist bays. (am going to post another thread about my radiant system).
Very interested in efficiency and long term savings - I will be in this house 25yrs or more (have owned for 13 yrs already - finally doing addition to make it dream house). We're looking for higher SEER ratings, the energy star tax credit, heat pump and ac (no gas furnace since we'll have hot water radiant primary heat). In addition to the foamed roof deck (old and new) Am foaming the exterior envelope in the addition walls (60% of house walls) to at least 1" to air seal and then finishing with cellulose (to about R-18). All addition windows and doors are low e/argon. Old house windows single with storm, + uninsulated old walls (about 40% of house exterior wall area).
Manual J with very close examination of data input says - just shy of 4 tons for 3 levels + semi conditioned attic.
Here go my questions - thanks in advance for any input!
1. Is Carrier the way to go - I want efficiency - ability to run on low stage and low velocity of air to dehumidify as well as cool. But I also want reliability, longevity, technology, ability to maintain and fix easily, etc.
2. Is Infinity the best control for achieving this - and is it worth it? As an engineer myself I look forward to diving into the control of my complicated systems.
3. I like the thought of 2 - 2 ton units instead of having to run large supply and return ducts from basement to attic - would like to get powder room in the space on the main floor where now the old house system's big duct chase box out runs upstairs.
4. Could I have one outdoor unit that runs 2 indoor air handlers?
5. What is the sweet spot for efficiency vs. value - SEER 17/19/21?
6. Do I want variable speed air handler and 2 stage (or is it multistage) compressor?
6. Do these models look right together?
Infinity 21 SEER a/c condenser - 24ANA124A003
Infinity 19 SEER heat pump - 25HNA924A003
Infinity 17 SEER heat pump - 25HNA624A003
Infinity air handler - FE4ANF002T00
Infinity Control -SYSTXCCUID01-B
Thanks - for any thoughts. I'll be back with more info.