It doesn't matter what is ''new'' in building technology if your builder doesn't already use it as a matter of course. If you want him to do something outside of his repertoire, you're going to pay extra for it. It's best to ask him about his practices and then decide if you can live with that, or if you want to pay the difference to do something else.

.Maybe put the central h&a unit in conditioned atic(total
electric)foam the underside of standing seam roof.Is this the thing to
do?

If ductwork & equipment are in the attic, then it is a good idea

to foam seal the roofline. in creating an unvented semi conditioned

foam sealed attic you eliminate issues like IC recessed lights instead

of ICAT (insulation contact air tight) recessed lights, thermal bypasses

at fireplace inserts, dropped ceilings etc.

air & thermal boundries are moved from attic floor to roofline

so that these leakage sites between attic & living space

are depressurized & no longer suck extreme attic temps

into living spaces.

would it be closed cell for your climate?

with any foam install inches of foam has to meet code's

r-value requirements. no "1" performs like r-10". no "average fill"

same depth everywhere. low spots happen, but low spots

should equal code requirement, not the high spots of the

foam install.

the air seal from roofline to attic floor is biggest leakage

site, these areas should be inspected at the least & tested

to verify install.

if so what kind of foam under the siding,in the atic and do we use
batts or blow in the attic and walls?I

high R-value foam sheathing under siding.

once foam sheathing is properly installed & sealed,

then conventional insulation in walls.

incorporate ADA (air tight drywall approach)

to interior walls for a high performance

high R-value tight wall.

buildingscience.com calls this a perfect wall construction.

if you are foam insulating the roofline, you forgo any

batts or blown insulation in the attic.

best of luck

I opted to spray foam the entire building envelope, rafters and all. House is 3,920 SF with a 5 ton HVAC unit that operates at 44% capacity most of the time (100* here in TX past couple of days with variable speed compressor) = huge energy savings and ultra comfortable inside even with a higher than normal setpoint since we arent inhabiting yet, and high delta T. Being air tight helps keep humidity down. Foam cost about $9k for walls/rafters.

there is a good deal of monies to be saved by sizing the hvac system.

when using foam insulation & paying the higher cost of the

product, there is a tradeoff. the tradeoff is smaller hvac system.

one can install a two stage unit, where at full capacity

it is oversized, but operates 98% of the time in low speed.

(ie 5 ton operating at 3 ton capacity) or you can just

buy a 3 ton system to start with. no need to pay the upcharge

for capacity you'll never use.

a single stage condensing unit & a variable speed air handler

will control humidity beautifully....if it is sized correctly.

best of luck.

I agree. I provided manual J calculations to the HVAC contractor. We could've used a single stage 3 ton for a 75* setpoint, but I wanted the ability to bring the temperature down to 72* on our hottest days. Hence the 5 ton Trane unit, which I splurged for the two stage compressor, variable speed air handler and 4 zones. We are very happy with the system. No hot/cold spots and the humidity is very low.

Depending where you live, studs + foam board + siding may be a no-no. Round these parts we need sheer walls for hurricane protection. That involves some plywood nailed in a specific manner. Those folks in CA have to worry about earthquakes.

solid sheathing with foam sheathing over it is the usual here

in hurricane alley!

In the attic under the roof, foam seal all gaps at the tops of interior (and exterior) walls to prevent heated moist inside air from venting into the attic space. Such air leaks promote mold and heat loss plus warms the roof. A warmed roof in snow country is trouble. It causes the snow to melt on the upper part of the roof and then the liquid drains to the unheated overhang and freezes making an ice dam and huge icicles hanging off the rain gutter. The condition can get so bad that it wets the interior of the outside walls. If snow is not a concern, heat losses still is. This leakage also affect the cost of air cooling in summer.

Make sure that all vents, kitchen, bathrooms, and laundry vent to the outside or through the roof. Do not vent into the attic.

Do not skimp on attic insulation. Use plenty. It has a big effect on both heating and air conditioning. I had my attic insulation increased last fall and during the winter months, I measured a fuel reduction of 13 to 15% based on comparing BTU per degree-day between the past two winters. I am also seeing less electric power used for A/C, but do not have enough data yet to make a proper calculation.

The basic code insulation requirement in your area is wall R20 and roof R38.

If your budget will allow it, consider 5"+ closed cell foam in the rafters for an R of 38+ and Zip System 1" thick R sheathing (R3) on the exterior walls and dense pack cellulose in the stud cavities for an R of 24+ This sheathing is also available in a thickness of 1 1/2" (R6).

Before you assume the zip R system is too expensive, you should price it. Compare it to the cost of OSB sheathing, home wrap and exterior foam board.

There is no minimum exterior insulation for your climate. You can easily meet the code requirement with cavity insulation so exterior foam will take a long time to pay for itself. The major benefit would be to allow an interior vapor retarder to be omitted and drying to be to the inside. The minimum thickness for that design can be determined with a winter dew point calculation.

light? not sure to what you refer.

All I can think of is air sealed recessed light fixtures.