I'm pricing out a "mini split" system for our little addition, mostly for the "shoulder seasons" heating but primarily for cooling. Some of these units will produce 100% of their rated output at 5 below zero!
(Yooper) Dave, I've had 2 guy's out here to size & quote a 2 'head' system. Neither of them did more than a few basic size/volume measurements and seem'd to give a "seat of the pants" BTU recommendations that were different from each other. I have learned in the past from friends mistakes that with cooling, the "sledge hammer" thinking/sizing will not properly dehumidify your space. We currently use a 10k window shaker and that does the job well enough other than a long streak where the heat might build for days in a row, and also does not heat or cool our up coming additional 400 s/f. To defend these guy's, we have a very small house without any doors, long hallways & room count, and it's pretty easy to see the whole space with just a few steps. I expressed my concern to one of these estimators and he said that these units are variable speed and will acomodate my concerns about short cycling. I also showed - told them that the walls have 3" of iso foam with 3.5" of f/g on top of that along with Tyvek and all the humanly possible "air sealing". There is a lot of glass in the addition, and although they may not be the highest performing windows, I've always trusted Andersen's. The ceiling in the "old" part is more traditional with 6" of f/g with 16" +/- of blown in and the addition will have 7.5" of iso foam. Should I request them doing a manual J or whatever it's called? One outfit is sizing a 19k BTU and the other is going with a 24K BTU. The bigger unit qualifies for a $750 state rebate but still is an additional $400. I really don't care about the $400 or the rebate, but just want it to be sized properly.
While I worked in the field, I was never involved in sizing of units or even sales. I even worked with some guys that had questionable practices once it came to condemning heating units.....and let me tell you-that was not a happy time. Voiced my opinion with the boss to no avail. I can't really recommend what size for you to go with, sorry.
fuelrod does your state have an efficiency program... ours does they come out do a blower door test a floor plan and figure but you will need to heat and cool... there is an area to put in insulation type and amount.. this is done because new builds here require it to get certificate of occupancy.. r 60 red in any vaulted ceiling.. why house prices are
Yes they do, the bigger compressor will qualify. As for insulation, they do have a program, I'll have to check but it's a small sq/ft, I did it myself, and a lot of the foam I used is used. Take off from commercial roofing jobs where they apparently remove the roofing along with the insulation (on flat deck metal roofs) is done. Some of the facing on the sheets show water damage, but that is not an issue for my walls. I have bought this type of material several different times and you can save big. Around $10- $12 for a 4x8 sheet of "iso" foam depending of the thickness. Polyisocyanurate (iso) has the best "r" value per inch at 6.5. The street price is well over $25 a sheet new. I've seen guy's on C/L VT .
yes but they should be able to r value with blower door test so you can get correct size unit. .. I might have software on an old computer let me check..
