Strictly read, this is not correct. If you add in the nuance of reflected vs. direct light, then we are getting closer. If the target were simply to generate an ambient luminous flux, then I suspect that I have better tools to measure that than most anyone on this board (I have access to a $20k spectrophotometer at our lab, and I routinely have a few desktop spectros and other light meters in my home office). I'm not trying to be rude, but I was more looking for equipment-specific advice, not general design advice.Quote:
Without a proper ratio of East and West facing windows for adequate daylighting,
the glazing imbalance Creates the Heat Gain issue that has to be 'fixed'.
Address the root cause.
Given that, and given that I am willing to pay for higher-spec items if they bring better performance to the table, I am back to my original questions...Quote:
What you describe (" sun house", nor just a sunroom) likely raises the window heat gain to >> 2/3 of the overall heat gain.
Howdy neighbor. Mr. Bear, you will find tons of good information here, and lots of great Pro's with all the science, but "bear" in mind "no pun intended" we live in the "Bermuda Triangle" of the a/c world, they haven't developed any a/c science really works 100% here "yet" but I hear NASA is on it. :grin2:
Let me perhaps get more clear about the various options under consideration:
1) Single stage AC + (small) Gas furnace - standard Houston practice, we have this in our current home. Probably two units (one up and one down). If I don't ask for better, this is likely what every contractor my builder polls will spec.
2) Single-stage Heat Pump - as above, but without the gas furnace. Electricity runs $0.11/kWhr (more or less) and gas is $0.80/Ccf (more or less). Higher acquisition cost vs. the AC unit, but indeterminate vs. the package.
3) High-efficiency, two-stage iterations of both of the above. Somewhat likely to get "upsold" into a higher tonnage unit(s) to handle peak loads, while the lower speed stage may or may not still be overkill for our average needs. Ductwork and other items also having to be sized to the peak airflow means more added expense.
4) VRF Heat Pump (Japanese) - Mitsubishi can operate more than one air handler internally (great!), but there are few contractors locally who work with these units (not great), and the ones that seem to work in a ducted application (we need high performance filtration) seem to only have mid-market efficiency ratings. I've read a studies done by FSRC, among others, on these types of units to see what the practical efficiency is. This is still an open question.
5) Variable-Speed Heat Pumps (Team America) - Lennox or Carrier both offer variable speed heat pumps, but zoning is done via dampers (as far as I can tell). This complicates the ductwork, and the Carrier units seem to have had some teething pain. The Lennox units are even newer.
One of the issues I am especially curious about getting expert advice on: would we need dedicated dehumidification (e.g., Ultra Aire XT105H or XT155H) if we went the VRF/Greenspeed route?
I like the idea of using the DHW source as the back-up or even primary heater, though finding someone locally who can do it may be a challenge. There are also people whose opinion I respect who say that I would want to keep the water that I use for heating separated from my potable hot water (this was in the context of in-floor hydronic systems, but the general principle probably applies...).
3 cop 3.4 ... ~10 HSPF ... > 35'F
0.03 Effective $/ kW
$0.879 per Therm electric
At $0.80 / Therm and 80% furnace efficiency, net $1.00 N.Gas therm
A new heat pump will likely cost slightly less to heat house than an 80% to 90% efficient N.G. furnace
"The rest will be a simple matter of execution..."
good that you added the smiley..execution may not be
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
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.
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.
you say ducts in conditioned space...can you explain this a bit?
fur downs? foamed attic?
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.
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.
best of luck.