rwilkers
06-29-2009, 01:00 AM
Building a new home, it is 2000 sqf on the first floor, and has a partial loft area with a 8/12 pitch cathedral ceiling. Usuable floor space total for first and second is approximately 2800 sqf, however all the floor space, usable/unusable is within the conditioned area.
Walls are Polysteel 4000 series ICF, the roof is 2x12 on 16"centers with 1+ inch of closed cell foam topped with a full stuffing of BIB. Gables upstairs are 2x8 with the same treatment. Windows are double pane, low-e and moderately sized.
House will have a 90 cfm ERV system, and separate unidirectional exhausts for bathrooms, and kitchens. Slab has 8 zones of radiant tubing, my plans were to heat radiant on the first floor from the geothermal and solar collectors, use geothermal forced air heat pump/backup heat strip on the second floor (if needed). For cooling, the geothermal would supply all via forced air to upper and lower floors, each room or floor with dedicated adequately sized return air supply.
I had two bids for a closed loop vertical geothermal, one bid called for 4 ton on the bottom and 2 ton on the top. The second called for 5 on the bottom and 3 on the top. I frankly did not believe that this house could need 6 to 7 ton of AC, especially when I was trying my best to design energy efficiency into it.
For that reason I purchased a home owner copy of HVAC-CALC and ran the numbers. Being liberal in my assumptions I came up with the following...
Whole House
Sensible Heat Gain 19,547
Latent Heat Gain 4,018
Total Heat Gain 23,565
Total Heal Loss 25,071
These numbers are pretty different from my bids, and I don't understand why they want to install two units and not a variable speed zoned single unit. Any ideas/help/suggestions here?
Walls are Polysteel 4000 series ICF, the roof is 2x12 on 16"centers with 1+ inch of closed cell foam topped with a full stuffing of BIB. Gables upstairs are 2x8 with the same treatment. Windows are double pane, low-e and moderately sized.
House will have a 90 cfm ERV system, and separate unidirectional exhausts for bathrooms, and kitchens. Slab has 8 zones of radiant tubing, my plans were to heat radiant on the first floor from the geothermal and solar collectors, use geothermal forced air heat pump/backup heat strip on the second floor (if needed). For cooling, the geothermal would supply all via forced air to upper and lower floors, each room or floor with dedicated adequately sized return air supply.
I had two bids for a closed loop vertical geothermal, one bid called for 4 ton on the bottom and 2 ton on the top. The second called for 5 on the bottom and 3 on the top. I frankly did not believe that this house could need 6 to 7 ton of AC, especially when I was trying my best to design energy efficiency into it.
For that reason I purchased a home owner copy of HVAC-CALC and ran the numbers. Being liberal in my assumptions I came up with the following...
Whole House
Sensible Heat Gain 19,547
Latent Heat Gain 4,018
Total Heat Gain 23,565
Total Heal Loss 25,071
These numbers are pretty different from my bids, and I don't understand why they want to install two units and not a variable speed zoned single unit. Any ideas/help/suggestions here?