Basement heating duct help

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Lja111

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Hello Terry. I have followed you to your website.

Situation:
I'm looking to heat my basement in Bethlehem PA. New construction (2012), poured concrete foundation, propane fueled forced air HVAC in 2-zones. One for the first floor and one for the second floor (heating unit in basement) AC units are outside (1 for each zone). Basement will be about 2000sq ft. I have currently framed the entire perimeter and insulated the walls with
1 1/2" closed cell foam boards(pink stuff).
After electrical I will add fiberglass insulation.

I am pulling from the existing 1st floor Goodman system which I noticed is larger than the second floor unit. Their where 4 existing runs connected by the builder. They could not get a certificate of occupancy with the duct connected without insulated blanket on the walls, so they disconnected by cutting and capping. Once I connected them back it is not sufficient. I tested in 20degrees out side weather. The basement was 58 and the first floor was 68. I'm thinking of adding two more runs. What do you think about that. So there will be 6 total in the basement.
Everything is open with the exception of bedroom/office, bathroom and gym.
My budget is 50,000.

I understand It is not a separate zone and I will in essence have to heat 1st and second floor together. If I may add the contractors were sloppy. Everything has been done poorly. Rigid pipe runs not insulated, no mastic on joints, flex duct had hard turns reducing air flow etc. I will be correcting all mistakes.
Need help with directing duct work under lam beam .

When I take on a project I do it to its fullest potential. I plan well . . . I have a better chance of being happy with the outcome.


Linda
 

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Dana

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I assume the 1.5" XPS is a continuous sheet, not broken up by studs, with the studs fully inside of the foam? Has the band joist and foundation sill been air-sealed (with spray foam) and insulated?

At 1.5" the pink board is good for about R7.5. A 2x4 16" o.c. wall with R15 unfaced batts would come in over R10 after factoring in the thermal bridging of the studs. Adding that to a continuous R7.5 you're looking at something like R18 or higher rather than R7.5, so the conducted heat loss out of the walls (which is the lion's share of it, once you've air sealed) will have been cut by MORE than half. How much of the foundation wall + band joist is above grade outdoors? Total perimeter length? With those numbers we can do a quick & dirty load calculation for the basement both before, and after.

This means you probably won't need more than the existing amount of heating air to keep it up to temp after insulating between the studs, if you take the air sealing both the house and the ducts seriously, and that's where the time & money is better spent.

I live in slightly colder climate than you and have 3" of rigid polyiso foam (about R17) on the foundation walls in a ~1500' basement, with no insulation under the slab. But it's reasonably air tight. Even with no direct heating the basement stays at about 65F even at sub-zero outdoor temperatures. YMMV

If beyond all likelihood the basement zone can't hold 68-70F during the coldest weather with the existing ducts, a better solution would be to install a heat-exchanger isolated hydronic heating loop off the hot water heater. The heat loss characteristics don't track those of above-grade zones very well at all, and ideally would be their own zone entirely. With an R15 + R7 c.i. wall you're probably looking at a peak heat load of 3-4 BTU/hr per square foot (including slab losses) of conditioned space, or 6000-8000 BTU/hr for a 2000' basement, which is but a fraction of the burner output of a propane water heater.
 
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