My wife and I are in the early phases of designing a new house in Houston. We have started working with an Architect, and we hope to engage a builder here soon. I've spent about three years reading and getting educated on building practices and energy efficiency (e.g., I have read a lot of what Joe Lstirubek has written), and I would appreciate getting some advice from the Pros here before we get too much farther along with the design and to help educate me about how to know when I've got a great HVAC contractor vs. when I've got someone who knows enough to put the right words on the bid, but whose team does the same-old-thing when it comes down to installation.
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Thanks for any thoughts!
Did you find Joe's Houston study on ventilation and humidity control in Houston? He measured several styles of ventilation and humidity control methods. I will see if I can find it.
Regards TB
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Designer Dan
It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
Without the Estimated glass area and orientation, one doesn't know (cannot calculate) the Heat Gain.
120sf - 150sf (still running the numbers), looks like that got left out of one of my earlier posts due to a Firefox crash. The heat gain is relatively straight-forward to model to a level that is "good enough" for where we are at in the process, as far as I can tell.
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.
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.
What you describe (" sun house", nor just a sunroom) likely raises the window heat gain to >> 2/3 of the overall heat gain.
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...
Did you find Joe's Houston study on ventilation and humidity control in Houston? He measured several styles of ventilation and humidity control methods. I will see if I can find it.
Regards TB
Yep. There have been several "Houston Studies". Joe's work with a local production builder is what caused me to investigate them. However, for my neighborhood, that builder's surcharges basically made them uncompetitive with local custom builders. There have been other studies done on Houston homes, esp. with respect to energy savings for EPA Energy Star homes, and the findings regarding insulation are informing the design.
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.
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...).
Let me perhaps get more clear about the various options under consideration:
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.
You "might" find one heat pump per 100,000 conventional a/c's in Houston, that ratio should bring you up to date and how popular and energy efficient the HP is here, gas is just way to cheap here to even entertain the thought of a HP. I would sure like to know what company in Houston even gave you the option of a HP, but he must be a big share holder of Reliant shares.
Designer Dan
It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
"Likely" key word here, my very highest gas bill ever during the winter was $36.00 and some change, the lowest electrical bill I have even had in my life in Houston of 61 years has been $148.00 and some change. Just some food for thought, from someone that actually lives here and pays utility bills here, from the real world, not any chart.
"Likely" key word here, my very highest gas bill ever during the winter was $36.00 and some change, the lowest electrical bill I have even had in my life in Houston of 61 years has been $148.00 and some change. Just some food for thought, from someone that actually lives here and pays utility bills here, from the real world, not any chart.
My highest electric bill for SW FL 1,800 SF residence in last 10 years is $134 and lowest $42.
with an old 10 SEER unit.
< $100 for June, July and September is highly probable with a new AC unit.
I don't have gas.
Designer Dan
It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
My highest electric bill for SW FL 1,800 SF residence in last 10 years is $134 and lowest $42.
with an old 10 SEER unit.
Well if I had a Pit Bull guarding my stat, I might have those type of electrical bills. In all reality, this is why I never even go there with a customer on expectancy of the reduced cost of their electrical bill, we should be selling comfort only, not savings. A homeowner with a 23 seer system, can have higher bills than a person with an old dinosaur 8 seer, if you have someone that has total control over the stat. Does your truck get better gas mileage with Jr. driving it out on a sat. night, that don't even know were the brake is, or with you driving it? I know, yaw don't like me because I am a realist.
"The rest will be a simple matter of execution..."
good that you added the smiley..execution may not be
simple.
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
gas.
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
properly.
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.
The cure of the part should not be attempted without the cure of the whole. ~Plato
"Likely" key word here, my very highest gas bill ever during the winter was $36.00 and some change, the lowest electrical bill I have even had in my life in Houston of 61 years has been $148.00 and some change. Just some food for thought, from someone that actually lives here and pays utility bills here, from the real world, not any chart.
We currently average around $200/month electric and $48/month for gas (1300sf).
Originally Posted by Bear_in_HOU
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