I have a few questions for those in the trade:
1: Does the current Manual J 8th edition include considerations,
calculations, and/or values for the infiltration tightness of an ICF
building envelope? Does it utilize both u-factor and shgc for windows?
If so, can it be adjusted to address passive solar gain for structures
designed with proper southern orientation and overhangs?
The windows and doors for the home have Energy star rated u-factor and shgc,
but the shgc is being spec'd high for thermal gain in the winter, with the
windows shaded by building overhangs in the summer ( northern climate zone).
I only received one of several bids requested so far, and the contractor
said he did the load calculations per manual J. But he sort of tap-danced
around specific questions about the calculations, and the unit size/btu
rating seems to me to fit a "sq.ftg./8" sizing, as opposed to an accurate
calculation based on r-22 ICF walls and r-40 ceilings combined with
geothermal and radiant/gyp. floors.
2. I've identified the WaterFurnace brand gshp's as the most efficient, and
have requested the bids accordingly. This contractor spec'd a Synergy3
unit with radiant /forced air htg/ac with a 15kw boiler. When I asked him
about why the Synergy instead of a reversible EW unit, he said forced that
water coil ac air-handlers were hard to find and the boiler was for backup.
I'm not sure how the boiler is backup, since its an all electric
I'm hoping that the other contractors bidding will be more specific/
forthcoming with information on how they arrived at their specs, but in the
Can those with experience of combining geothermal / radiant /
ac / ERV
comment on their approach and equipment choices?
Thanks in advance.