It never is, but execution will matter less if I get the wrong package in the spec up-front. For my nickel, I want to know the trade-offs, then watch the install like a hawk. The framing, flashing, insulation and window install will also be watched very, very closely.
Originally Posted by energy_rater_La
Hence the quest to seek advice and information. ;) I'm especially worried about the first issue. I could solve a fair bit of the worry by just specifying a Mitsubishi Ducted system, but then I'd wonder about how high of a premium I am paying for the one (or two) guys in town that carry the gear (let's give them the benefit of the doubt that they understand VRF if they are willing to carry it down here...).
my worry is that you'll encounter quite a bit of the 500 sq ft per ton hvac sizing.
so prepare yourself for that battle, the two systems are better than a single
zoned system, and really work on if heat pumps cost more to operate than
I hope that I haven't given anyone here the impression that HVAC choices aren't a priority! ;) You hit the nail on the head, though, of what I sense are the key variables at play (greater expense for more efficient operation, but that may be a significant net increase in cash costs).
understand that rather than downsize or even properly size the hvac systems
the goal will change to more expensive equipment set to run in lower speeds to
achieve less tons. you pay for the upcharge, extra system & cost to maintain &
operate for a very very long time. make your hvac choices a priority.
The inexpensive Panasonic ERVs are still in the running, but if we go with a conventional set-up, we will most likely go this route.
whole house dehumidifiers can be set up to bring in needed fresh air.
that is the route I'd go.
windows are the weakest part of the wall, the lower the shgc & ufactors are,
the better the window. itrw purchasing different shgc & ufactors for different
sides (orientation) of the house is another problem. unless you plan to make
sure yourself that the right window is installed on the west side vs north side
it is better to buy the same window for all sides.
just what I've encountered over the years.
don't believe that the installers
actually understand the difference between anything other than window size.
and invest a little time in reading flashing directions that come with each window unit.
you can be sure that the installers will do the flashing the way they have always
done it. we have lots of water intrusion here from that old X cut into the housewrap.
good flashing info on each window...if someone reads it and makes sure it is done
what is your insulation package?
for walls, I perfer foam sheathing on exterior, conventional insulation in walls
and air tight drywall approach to interior.
1) 0.5" drywall
2) 5.5" high-density fiberglass (2x6 framing; ~R-23)
3) 0.5" plywood - seams staggered and taped
4) Tyvek Drainwrap
5) 1" PolyIso - seams staggered and taped (~R-6 aged)
6) Exterior cladding (deciding the mix of 3-part stucco vs. Hardie)
Spray foam only in the rim joists, wall-to-roof transition, and penetrations.
Give or take, the whole wall will be R-20 or better, depending upon framing factor.
2) 12" high-density fiberglass (~R-50)
3) 0.5" plywood decking
4) I&W Shield
5) Composition shingle or standing seam (still working the budget -- a few other options being considered)
Unvented attic, open-web trusses. The most relevant near-term decision is how many air handlers we need and where they need to be located (e.g., Mitsu VRF or multiple systems? We need an air handler on the first floor. Carrier or Lennox zoned? Not so much.
you say ducts in conditioned space...can you explain this a bit?
fur downs? foamed attic?
Unvented attic means that any can lights are not going to be a source of heat loss or a weak spot for moisture accumulation.
with ducts & equpment not in the attic..you'll save on utility costs.
if possible to do, it is a good step towards performance. putting ducts in
conditioned space nets about a 25% energy savings.
recessed lights should only be ICAT insulation contact air tight. IC are cheaper
but an opening to the hot humid attic. retrofitting IC to ICAT is costly. better
to buy ICAT to start with.
We're still trying to determine that last one!
sealing any penetrations from attic into living space should be priority also.
oversized cuts for bath fans, recessed lights, stove venting, return or supply
air..these areas are easy to find if you look for the leakage sites prior to
insulation in attic.
what is attic insulation?
radiant barrier/tech shield?
curious as to what high performance requires in houston.