Advice Sought for a High Performance New Construction in Houston

[teddy bear]

I like his article "Latent Heat is the Wicked Witch of the South" this is why in Houston we have such long run times. I get this a lot, especially from folks in older homes, Bill my a/c seems to run all the time, well Mr. Jones, when your feeding your a/c with latent heat all day long through cracks in walls, doors an etc. your need to starve that a/c by sealing up your home first. Or as Mr. Bear would tell them, get yourself a whole house dehumidifier, which I personally think is the best bang for your buck in our climate, or just add one to your new system.

A small point of difference. Homes need an air change of fresh air in 4-5 hours when occupied. Occupants add moisture to the home. When the outdoor dew point is 60-70^F, but the sensible temperature is 65-75^F, the a/c does not have significant sensible cooling load while still getting the 3,000-4,000 btus of latent load.
If home really got the needed fresh air during low cooling loads and high dew points, they will be damp. Unless they have reheat or supplemental dehumidification.
Ultimately, fresh air ventilation when occupied and supplemental dehumidification are needed for indoor air quality and comfort in a modern home.
A simple medium SEER a/c and a ventilating whole house dehumidifier are a practical method of getting the best of all worlds of IAQ, Comfort, Effeicency, and Reasonable Investment.

[Mr Bill]

A simple medium SEER a/c and a ventilating whole house dehumidifier are a practical method of getting the best of all worlds of IAQ, Comfort, Effeicency, and Reasonable Investment.

Going even a little deeper here, if the mfg. would incorporate a dehumidifier into the furnace or AH from the get go, the customer would get the best of both worlds in their purchase. Of course they may not be able to sell many of those high dollar, high seer systems either, and I am sure they would make more $$$$ off the high seer systems, rather than an integrated dehumidifier system. If I could build and develop one of these systems in Houston, I would be a trillionaire.

[classical]

For the type of home Bear is building a SDHV system with manual N load calc utilizing a Unichiller with Hydronic heat and cool staged and zoned he will have near perfect comfort with low utility bills including DHW. Considering the high west load a staged zoned system would be perfect.

I really do not know of another company that does this in Houston but I am sure UNICO could make a recommendation.

I would love to do a home like this but I am enjoying being retired from the BIZ and there is not enough money to drag me back.

And yes supplemental dehumidification would be very beneficial in a home of this type. Bear stay away from an ERV in Houston they are not worth the expense especially since it is not that much more for a qualty unit from UltraAire.

[motoguy128]

It actually could be easy to do. Just take a residential water source unit and add a split condenser then make the piping changes and add the 2nd coil for hot gas reheat. Then maybe add the option of and integrated erv and our economizer


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[Bear_in_HOU]

A simple medium SEER a/c and a ventilating whole house dehumidifier are a practical method of getting the best of all worlds of IAQ, Comfort, Effeicency, and Reasonable Investment.

If I never get away from needing the dedicated dehumidifier with the more advanced variable drive gear, then this starts to sound like the right way to go -- at least as a starting point. The sweet spot in the market right now is in the 15 - 17 SEER range?

For the type of home Bear is building a SDHV system with manual N load calc utilizing a Unichiller with Hydronic heat and cool staged and zoned he will have near perfect comfort with low utility bills including DHW. Considering the high west load a staged zoned system would be perfect.

I really do not know of another company that does this in Houston but I am sure UNICO could make a recommendation.

The website pushed me to someone in Dallas, but I'll see if they recommend anyone local.

Setting aside some of the pure performance aspects, it also seems like every US-based manufacturer has a proprietary communication format for their more advanced product lines (e.g., iComfort from Lennox). Can a Nest or other advanced third-party t-state use the full capability of a Greenspeed or XP25/XC25? I am a little bit of a gadget hound, but I mostly don't want to get out of bed to change the thermostat. The rest of the bells and whistles are toys.

[Bear_in_HOU]

It actually could be easy to do. Just take a residential water source unit and add a split condenser then make the piping changes and add the 2nd coil for hot gas reheat. Then maybe add the option of and integrated erv and our economizer


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Thanks! I think I follow, though my understanding was that water-based cooling was for high capacity commercial use. I am hoping for a peak heat load in the 3 - 5 ton range and our lot is a small, inner city lot.

[classical]

The nest will not provide full function with communicating equipment.

[Mr Bill]

The nest will not provide full function with communicating equipment.

Your right! the Nest is nothing but a conventional stat on steroids, that "supposedly" saves you money, because it has a built in setback that you have no control over. O lets not forget it's most positive feature, the wifi ability to adjust stat away from home with your smartphone device, well you can get a good mid range Honeywell with wifi capability, that has more "useable" features, but not quite as pretty.

[motoguy128]

Nest is just a clock programmable thermostat with internet access, a motion sensor and logic that prioritizes energy savings over comfort. It provides little benefit if any if you have properly sized equipment. It's a lot less capable than most of the communicating systems, espescially those like Carrier Infinity that manage airflow precisely to maintain humidty levels.

Controlling humidity, is the key to maintain comfort in any humid climate. You happen to like in one of the humidity capitals of the country.

[motoguy128]

Tell you what... just blue print my home, move some walls around so you can have a more ecclectic, inefficient, hodgepodged modern layout, spray foam the wall cavities use a cool roof, drop the window area to a more reasonable amount to keep your constrution costs in control, and I'll guarantee you can cool the whole place with 2 tons... and it won;t matter when thermsotat or equipment you use, since it will be cool, dry and even temps all the time. It was designed almost 90 years years ago by someone that I think was a lot smarter and mroe expereinced than those designing houses now. It was built at a time when AC didn;t exist in residential homes, so it built in features to cool a home naturally. Why reinvent the wheel.

[classical]

Bear call and talk to Dr. Heat Professor Cool in League City or Contact Jason from this site. Now that I am retired they will be your best bet for a proper design and install. I do not know of anyone in Houston that does quality work that does Unico.

I seriously doubt you will need 2-tons total cooling for this house.

Best option but expensive UNICO with Unichiller w/dehumidifier, next best Infinity/Greenspeed or comparable Lennox product w/dehumidifier. The only reason I recommend a 2-stage system is because of your peak load with west wall fenestration.

Zoning is also recommended and the Lennox and Carrier equipment have the best zone products.

[Mr Bill]

Al, his biggest issue in Houston, is going to be someone that is willing to take on the responsibility, of guaranteeing the outcome of his expectations. Probably have better luck in the off season, finding someone that is willing to spend some time on his project. Problem is with any a/c sale, it's impossible to know exactly what the homeowner expects, especially on a new build, because you have nothing like an existing ac system to compare it to. Is he going to be the GC on the job? If not he will have to tell the builder he will handle the ac part, most GC's don't like that, and are not very corporative with the ac contractor on the job, been there done that before. Al, even if your retired, this would be a good pocket change job you could supervise, unless your just spending all your time and money traveling the world. I thought about at least simi-retiring, but I don't travel much, I am pretty much a home body, retiring would turn me into a recluse.


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[vangoghsear]

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.

You can do better. Probably lowest first cost option though.

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.

In tight, well insulated construction this is worth considering. Have you considered Photovoltaic Solar panels to offset utility costs. This option is not as costly in new construction where the roof is going to be new, the electric system is being installed new, structure for the panels can be designed into the home while it is being built, energy studies required to obtain incentives will probably already be needed for the home design anyway or not required due to the expected levels of insulation etc, and incentives may still be available to make the cost reasonable. Solar makes heat pumps a no-brainer, if it is a viable option for your area (I don't know what the feel is for PV solar down there. I have a ground mounted grid tied 8.8 kW system at my house in NJ and I spent less than $200 last year for my grid tied electric with a 3 ton heatpump, heatpump water heater, an outdoor hot tub, electric cooking and clothes dryer and the usual other electric stuff. We used to average $150 per month plus $2000 per year for oil heat.)

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.

The upshot of oversizing is that a heatpump may be able to handle heat load without backup in some models, especially in milder climates for heating.

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.

I've used these type units on several projects. The question is open because there is difficulty modeling their capabilities. Commercial load programs couldn't model how they take advantage of part load through compressor load matching also, the ratings system did not extend low enough to show their advantage as a heat pump in colder climates through the ability when optimized for heating to do heatpump operation down to 100% rated capacity at 0 degrees in some models without backup heat. The drawbacks are that by code you have to make provision for the smallest room with an interior unit to be able to handle a dumping of the entire refrigerant charge into the room should a catastrophic failure occur, the units do not handle outside air well without a separate dedicated system, and finding an installer with experience who can do all the refrigerant piping work required. They also need to have provision for condensate removal on a local level (at each indoor unit) and the units are in the room, hanging on a wall, up in a ceiling or standing by a wall. The good news is they are very quiet and if installed right are very efficient.

I like the dedicated whole house dehumidifier option for treating incoming OA. If it also connects to RA then it will help reduce the latent load on the AC.

Another option mentioned above in some of the other posts that I have used is the mini chiller system. On the surface these do not appear as efficient as say the VRF minisplits (they look identical by the way), but they can allow for greater diversity for greater possible equipment size reduction. Only water and maybe some glycol (not a very high concentration in your area, I imagine) run through the building so the refrigerant charge is all outdoors so that code restriction of accounting for refrigerant dumping goes away. Installation can be done more easily because it is water piping and not refrigerant, many more contractors can do that kind of installation as certification is less stringent. Well suited to new construction. Same other problems as VRF with condensate disposal. Worth looking into though.

[teddy bear]

For the type of home Bear is building a SDHV system with manual N load calc utilizing a Unichiller with Hydronic heat and cool staged and zoned he will have near perfect comfort with low utility bills including DHW. Considering the high west load a staged zoned system would be perfect.

I really do not know of another company that does this in Houston but I am sure UNICO could make a recommendation.

I would love to do a home like this but I am enjoying being retired from the BIZ and there is not enough money to drag me back.

And yes supplemental dehumidification would be very beneficial in a home of this type. Bear stay away from an ERV in Houston they are not worth the expense especially since it is not that much more for a qualty unit from UltraAire.

Good to here from you again. Thanks for the support. There are many exciting mechanical ways to provide ideal temp/%RH throughout all the different weather conditions.
For long term affordability and simplicity, I like the simple med SEER a/cs and a whole dehu. Not much fun though.
Keep us posted on your retirement and any new concepts you feel might fix the problems we are faced with. I am older that you but continue to keep my finger in this bussiness.
Regards TB

[Bear_in_HOU]

Al, his biggest issue in Houston, is going to be someone that is willing to take on the responsibility, of guaranteeing the outcome of his expectations. Probably have better luck in the off season, finding someone that is willing to spend some time on his project. Problem is with any a/c sale, it's impossible to know exactly what the homeowner expects, especially on a new build, because you have nothing like an existing ac system to compare it to.

somehow I feel judged for even trying to get educated about HVAC -- something mentioned in a lot of other threads -- prior to the first shovel being put in the proverbial soil.

Is he going to be the GC on the job?

Not a chance.

If not he will have to tell the builder he will handle the ac part, most GC's don't like that, and are not very corporative with the ac contractor on the job, been there done that before.

I have never spent money on a car without a test drive. I'm not sure why I would take the lowest bid on HVAC (with a $10k+ price tag), and not know a little bit about the purchase ahead of time.

Al, even if your retired, this would be a good pocket change job you could supervise, unless your just spending all your time and money traveling the world. I thought about at least simi-retiring, but I don't travel much, I am pretty much a home body, retiring would turn me into a recluse.


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Not that it should have been relevant for this discussion, but I chose my builder because he was interested in having a client who cared about the craftsmanship of building a home as much as he cared himself. He knows that I am going to be beyond 'Type A' on things like flashing details and air sealing. The upside for him, beyond that he makes a nice profit margin, is that it gives him a reference to send other clients when he wants to talk about things like insulation values and air sealing -- one that is even more passionate, perhaps, than he is.

[Bear_in_HOU]

Tell you what... just blue print my home, move some walls around so you can have a more ecclectic, inefficient, hodgepodged modern layout, spray foam the wall cavities use a cool roof, drop the window area to a more reasonable amount to keep your constrution costs in control, and I'll guarantee you can cool the whole place with 2 tons... and it won;t matter when thermsotat or equipment you use, since it will be cool, dry and even temps all the time. It was designed almost 90 years years ago by someone that I think was a lot smarter and mroe expereinced than those designing houses now. It was built at a time when AC didn;t exist in residential homes, so it built in features to cool a home naturally. Why reinvent the wheel.

Generous offer. I think that there may be some kids on your lawn...

[Bear_in_HOU]

Bear call and talk to Dr. Heat Professor Cool in League City or Contact Jason from this site. Now that I am retired they will be your best bet for a proper design and install. I do not know of anyone in Houston that does quality work that does Unico.

Will do. I think Dr. Heat Professor Cool was on one of my lists of potential vendors.

I seriously doubt you will need 2-tons total cooling for this house.

For most of the day, I sure hope so.

Best option but expensive UNICO with Unichiller w/dehumidifier, next best Infinity/Greenspeed or comparable Lennox product w/dehumidifier. The only reason I recommend a 2-stage system is because of your peak load with west wall fenestration.

Zoning is also recommended and the Lennox and Carrier equipment have the best zone products.

Local UNICO rep left me voice mail while I was at lunch. I really hate that the Lennox iComfort t-stat requires a subscription. It's borderline offensive, actually. I haven't found the similar information on Carrier.

[Bear_in_HOU]

Have you considered Photovoltaic Solar panels to offset utility costs.

In the broader ERCOT market, we only have Federal subsidies. The upside is that we have a competitive (but small) residential solar industry (install costs are running ~$5/watt before tax credits). We'll get bids a bit later, but the house is being designed to dedicate the southern exposure to PV. We should be able to fit up to a 6kW system. Since I've lived through two hurricanes here with 2 week+ power outages, solar PV and a back-up generator are on the list of nice-to-haves.

The upshot of oversizing is that a heatpump may be able to handle heat load without backup in some models, especially in milder climates for heating.

I have enough toys (e.g., receivers, TVs, computers, etc.) with standby plug loads that we may not need active heating for much of our "winter".

I've used these type units on several projects. The question is open because there is difficulty modeling their capabilities. Commercial load programs couldn't model how they take advantage of part load through compressor load matching also, the ratings system did not extend low enough to show their advantage as a heat pump in colder climates through the ability when optimized for heating to do heatpump operation down to 100% rated capacity at 0 degrees in some models without backup heat. The drawbacks are that by code you have to make provision for the smallest room with an interior unit to be able to handle a dumping of the entire refrigerant charge into the room should a catastrophic failure occur, the units do not handle outside air well without a separate dedicated system, and finding an installer with experience who can do all the refrigerant piping work required. They also need to have provision for condensate removal on a local level (at each indoor unit) and the units are in the room, hanging on a wall, up in a ceiling or standing by a wall. The good news is they are very quiet and if installed right are very efficient.

I like the dedicated whole house dehumidifier option for treating incoming OA. If it also connects to RA then it will help reduce the latent load on the AC.

Another option mentioned above in some of the other posts that I have used is the mini chiller system. On the surface these do not appear as efficient as say the VRF minisplits (they look identical by the way), but they can allow for greater diversity for greater possible equipment size reduction. Only water and maybe some glycol (not a very high concentration in your area, I imagine) run through the building so the refrigerant charge is all outdoors so that code restriction of accounting for refrigerant dumping goes away. Installation can be done more easily because it is water piping and not refrigerant, many more contractors can do that kind of installation as certification is less stringent. Well suited to new construction. Same other problems as VRF with condensate disposal. Worth looking into though.

I'm not wild about having mini-splits -- too many filters to change, among other things. If we go with a VRF system, it would be with a traditional duct system and variable-speed AHU.

[vangoghsear]

In the broader ERCOT market, we only have Federal subsidies. The upside is that we have a competitive (but small) residential solar industry (install costs are running ~$5/watt before tax credits). We'll get bids a bit later, but the house is being designed to dedicate the southern exposure to PV. We should be able to fit up to a 6kW system. Since I've lived through two hurricanes here with 2 week+ power outages, solar PV and a back-up generator are on the list of nice-to-haves.


I have enough toys (e.g., receivers, TVs, computers, etc.) with standby plug loads that we may not need active heating for much of our "winter".


I'm not wild about having mini-splits -- too many filters to change, among other things. If we go with a VRF system, it would be with a traditional duct system and variable-speed AHU.

Glad to hear you are considering the solar. Lots of advantages in new construction to keep the cost more reasonable. 30k for 6 kW isn't too bad.

I think you may lose too much efficiency using the VRF without the mini splits. Some zoning may help, perhaps adding a peak load FC unit to help handle that westward facing room, but you may end up just paying more for what you could get from a med eff split system.

Some brands of VRF, LG for instance have a electronic plasma filtering and decorative wall units, just sayin' in case you weren't aware.

I like the mini-chiller systems too. You could put in a chiller sized to cover just your average load and add a buffer tank (a good idea with small systems anyway) sized to even out system operation, reduce compressor cycling on low load days, and help cover the peak load in that Westward room. Again though, you may need some zoning to really take advantage of capacity reduction.

[Mr Bill]

Al, even if your retired, this would be a good pocket change job you could supervise, unless your just spending all your time and money traveling the world. I thought about at least simi-retiring, but I don't travel much, I am pretty much a home body, retiring would turn me into a recluse.

Not that it should have been relevant for this discussion, but I chose my builder because he was interested in having a client who cared about the craftsmanship of building a home as much as he cared himself. He knows that I am going to be beyond 'Type A' on things like flashing details and air sealing. The upside for him, beyond that he makes a nice profit margin, is that it gives him a reference to send other clients when he wants to talk about things like insulation values and air sealing -- one that is even more passionate, perhaps, than he is.

Just wanted to come back and let you know, my quote up there was sort of an inside joke. Al is younger than me, so he must have lost interest in the business, or won the lotto. I actually Love this business, and would probably never retire even if I won the lotto. Not only that, I feel a responsibility to be around for the folks that help build this business, my customers. I probably could retire now, but I will wait till the old ticker stops beating to retire.