Manual J for well insulated house
I’m working on the Manual J, S and D for our upcoming home and would like some opinions on software to use. We’re building a simple 3br 26×36 colonial, with the basement being conditioned. Our home will have 10″ thick double stud walls, R15 rigid insulation on the basement walls, R10 sub slab, triple pane Marvin casement windows, R60 roof and are hoping to be at <1.0 ach50. We’ll also be using an intellibalance 200 ERV and Mitsubishi heat pumps.
I’m wondering what the recommended Manual J software might be for a well insulated house like this. Cool Calc doesn’t appear to have options for insulated slab or even walls greater than R21 stud cavity with R6 continuous. I’ve heard Wrightsoft has similar issues. Before paying for anything, I’d like to hear if anyone has any recommendations for a software that may meet my needs.
If it can do Manual S/D, that’s a bonus, but if not, I was planning on using the ACCA speed sheets. Does anyone have any opinions on those?
Thanks
Isaiah
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Consider BEopt, PHPP (both free) or REM/Rate to get you in the ballpark. Once you build to such high standards, the blanket assumptions made in standard ACCA manuals are grossly conservative. Most of them cannot model the construction methods you are describing.
The problem is that the building inspector is requiring the Manual J, S and D and told me he actually checks everything. I guess it's probably not a huge deal as I think I'm going to be oversized no matter what.
I tried Cool Calc and came out to ~23,000 btus for the total load (~ 900 sf conditioned basement, 900 sf 1st floor and 900 sq ft 2nd floor. My plan is for a ducted 1.5 hyperhear Mitsubishi system serving the basement and 1st floor, and another 1.5 ton hyperheat ducted system for the 2nd floor. There aren't any ducted 1-ton Mitsu products that also qualify me for the Mass Save All Electric incentive I'm going for, so I think I'm stuck with this.
Work with him. He's looking out for your best interest.
I absolutely plan to. I just like to have all the info before having discussions. I've already learned a ton by conversing with the inspector and I plan on having many more! Good advice here!
A single 1.5 ton unit does your heat load in Mass climate (zone 5). So having two is a bit overkill. Add in the fact that coolcalc can't properly model your place, having 3.5 tons of 5F heating capacity seems a bit overkill.
There is also the 3/4 ducted units which do about 1ton of heat at 5F.
There are also many other manufacturers that make similar equipment, I would aim for at least somewhat right sized one.
It's the problem of getting them to the space. I have 3 floors to condition, which makes only a single zone hard to make work. I also feel ducted units are a much better option than a cassette in every room for a number of reasons. If I look at smaller equipment, the minimum capacity is often the same (or even higher) than the 1.5 ton units I'm looking at.
For the most part, I was planning on using the 2nd floor unit only during the cooling season, and the lower level unit for heating season.
I'm also going for the $25k All Electric Incentive with Mass Save which limits my options.
In that case, it would make sense to go for the non-hyper heat unit for the 2nd floor. Make sure to get the base pan heater for it as this is an accessory for these.
It is cheaper, has higher HSPF and SEER and still does 1 ton of heat at 5f.
Where do you find phpp free?
https://betterbuiltnw.com/hvac-sizing-tool
This is the best tool I have used
You can look at these videos from Corbett Lunsford on Manual J calculations.
https://www.youtube.com/watch?v=DxK9JDVjN4U
https://www.youtube.com/watch?v=LEKEMI05dJE&t=121s
https://www.youtube.com/watch?v=LGhE4XwbDDE&t=23s
And from Matt Risinger
https://www.youtube.com/watch?v=CL-_VjlYnD0
Igrigos-What did you end up doing? I am similar boat, just north of you in NH with climate zone 6A