Before we begin, I just wanted to mention that I am not an industry expert, or even a novice. Please forgive me (and correct me, so that I may learn) if I use improper terminologies, measurements, etc.

I am planning on having a house built later this year as soon as my finances come though, I am sure many of you know how long the process of getting a home loan can take.

Building Location: Texas

Here is what I know about the house I am planning on having built:

Building Budget: 200K. Two-storey house with 835 square feet on first floor, 938 square feet on the second for a total of 1773 heated square feet. The shape (design) of the house is simple, mostly square with 7 main outer walls (10 with the entry angles added).  There will be a single room-sized basement to be used as a utility area, the size of this is to be determined, but approx 11x12 ft. There will be a wood burning fireplace in the living area.
The frame of the house is to consist of heavy steel for all outer and load bearing, and light steel for all inner frames -- wood will NOT be used in the construction of this home. The walls themselves are to be made of fiberglass 'Softwall' paneling. I don't want to use sheetrock/drywall in my home. This is going to be an OFF Grid solar home. I plan on using ~30 325W pole-mounted panels totaling ~9425W. The drop-in cooktop, in-wall oven and clothes drier will be run on propane, to keep the high-energy appliances off the solar grid. All floors will be covered with various decorative ceramic tile designs (prints?), based on zone. I do not like wall to wall carpeting. Area rugs will be used. ALL lighting will be LED.

Please be aware that these design decisions are set and will not be changed for any reason, so I would like to focus on: HVAC (Heating and Cooling), Heating Water and Insulation.

I was sent to this forum by the guys at GeoExchange, because they said that with my budget, strict off-grid design and location, Geothermal might not be the best decision for me. I was told that I would need to talk about insulating the outer perimeter of my house because the steel frame is a heavy heat conductor. Someone there mentioned Rigid Foam, so that might be a good starting point. It was also suggested that I seriously look into Ductless Mini-Split Systems for my home because they may very well fit into my budget. I originally had a 15K budget for geothermal, but it appears that it is near impossible to get this, since the drilling alone could EASILY cost that much. My budget still stands at 15K, it appears that I might be able to get 2-3 Ductless Mini-Split units installed with multiple zones and come well under budget.

I was also heavily interested in radiant flooring to heat my home, as I have read that this method is the most efficient way to heat compared to the forced air method. If I am incorrect with this, please let me know. If radiant flooring is still possible and I can do it properly with a modest budget, then I would definitely like to have this installed.

My problems are this: I do not know the power requirements for this Ductless Mini Split system, I hope someone here will be able to give me a little heads up about this, and I seriously need some help finding out how to properly insulate a home with a steel frame. I also do not know how my water will be heated. I am not heating it with propane, as I am limiting the appliances that will be using it. I had considered on demand water heater, but was told that they have a high energy demand, which I am not sure is true, if only one person will be living in this house. I would like to consider all of my options for heating the water too.

There are other design considerations that I don't think are important to the discussion, but I will reveal if/when they become relevant.

I think that about covers it.

Thank you so very much for reading!

Not to be critical, but it's a little frustrating when someone asks for advice but also says that the design decisions are set and won't be changed for any reason. There are other non-wood alternatives, such as ICF or steel skin SIP's, but I have to assume you've already looked into them. That being said, you definitely want to insulate the thermal transfer of heavy steel framing. Exterior foam sheeting will take care of that.

As for mini-splits, we have two Mitsubishi Hyper heat units in a 1400 square foot home in SC. Our house is ICF, and our heat load is only 11K BTU at our winter design temperature of 21 F., and 18K BTU's at 0. We generally only run the one 12K BTU mini-split unless it is very cold- single digits, which is rare here. Summer cooling load is only 9K BTU. We have one 12K unit, and one 9K unit. They are each on a 15A 240V circuit. Actual published load is 10A @ 240V max on each unit.

There are HVAC calculators that can accurately predict your needs as long as the data you put in is accurate and honest. I used HVACCalc, which was $50 for a one-time residential use, and the results have proven to be spot-on with our actual heating and cooling loads. You don't say where in TX; there's a wide range of climate in TX, as there is for SC. Both states are near-tropical in the warmest area, to much more temperate in the northern extremes. We are at the foot of the mountains in SC, so some of the coldest weather in the state.

Let's start with a zip.

jdebrree: Sorry about that, its just that the forum post that I made in the geothermal forum got taken over by overly critical individuals about my decisions, such as arguing that solar is not going to work very well (which is a lie. Texas gets 5 full solar hours per day, and the cloudy days are few), and going on about various other things, which took away from the reason I made the thread in the first place. I am not willing to argue or defend my design decisions, as it's not as if I am a pioneer with any of them.

Truth be told, I am open to other suggestions that you mentioned, just as long as its not a wood product. Stone, masonry, metal, brick, glass is what I am interested in. I just want to stick to the facts, and keep this thread on topic. Forgive me if i seemed cross.

BadgerBoilerMN: I am going to be building in 78645

Maybe I should try contacting a contractor who has experience building commercial structures? I'm not sure where to go from here. Maybe I should speak with an architect first, so I can get a set of blueprints drawn with parts lists, etc. All the people who have spoken to me/reached out to me thus far have been ignoring the things that I want, and trying to sell me a product that I am not interested in. It is quite frustrating.

I almost forgot to mention, that I want this house to be completely covered with masonry brick on the outer walls. I do not want siding or any other material. I've been researching long lasting roofing materials, and I want either Rubber or Composite Polymer shingles, with the latter being of higher interest, because apparently rubber can smell for a long time.

It's nice to see you found your way over to the right forum.

Now that you're in, take a look around. There are several discussion boards that are due research on your part. One is the windows forum, and since you've indicated some willingness to consider alternative framing, maybe take a look at the Insulated Concrete Forms, and or the Structural Insulated panels. SIPs could serve as an ideal roof, especially on an ICF structure for energy efficiency.

Thanks. I think at this point, I am just going to call around locally to see if I can find a Contractor that has experience in building my house the way I want it to be built.

It seems that all I need is good insulation and whatever.

To be honest, I don't think I can be dissuaded against a steel framed house. For me, there simply isn't any point of spending the money to have anything built if I can't get what I want. And I want to be happy with my design decisions if I am going to be living in it. I COULD use other building methods, but I would never be happy with them and would always regret my decision.

I need to speak with architects, Contractors and Engineers who specialize in this sort of thing, that way, I will get more, I don't know, doing, instead of various opinions.

I came here to seek help for information on how to build this house the best possible way it can under the parameters that I specified, and not using any other building methods, but it seems like either people do not know because they lack experience, or they don't like my ideas and don't care to respond.

Its kind of like you wanting a chocolate cake recipe, and someone doing their best to tell you that what you really want is an apple pie recipe instead.

Now, before I go, If there ARE any Contractors, Architects, Engineers, etc that have interest and/or experience helping me design this house under the parameters that I have specified, please do not hesitate to contact me.

Thank you for all that have responded to this forum post thus far.

Send the plans.

A light commercial contractor should be experienced with steel and won't have any prejudice against its use. The insulation stack-up for steel is a little different and potentially better than stick built, ICF or SIP, especially in termite territory.

We are considering a move to the area and I have taken consulted on many using my experience in Albuquerque as a baseline.

Going off-grid with mechanical heating & cooling systems is a bit of a tough thing to pull off with only 10kw of array under the best of circumstances. How many kwh per day do you expect to be able to bring in on a hot summer day, and how much on a cold winter day?

The daily uptake during peak cooling and heating days defines how much heating & cooling you'll be able to deliver, placing a firm boundary on how big your heating and cooling loads can be. You MUST design the house to be well within those limits using reasonable assumptions on what sort of heat pump efficiency you would have at the temperature extremes. Once you've designed the building envelope within those boundaries, THEN you can spec a mini-split or whatever that meets those loads. The notion that you need to "...keep the high-energy appliances off the solar grid is at odds with using heat pumps for heating & cooling. A cooktop or oven may have a high peak load, but the daily energy use is a fraction of what it takes to heat or cool even a low-load house.

In Leander TX it's probably best to incorporate a LOT of thermal mass into the walls to minimize the load peaks, and to minimize window area (particularly east and west facing glass, which will spike the cooling loads. It will also be important to use a "cool roof" finish on the roofing materials. There's a good reason the traditional building methods in that area were things like 2-3' thick white-washed adobe walls. You can face it with brick (preferably white or very light in color) or whatever you like and use whatever structural materials you like (steel is fine), but you'll need to incorporate quite a bit of thermal mass behind the insulation layers to keep the loads bounded. This isn't a matter of just high R values and steel construction. Think about approaches like rammed-earth walls with a couple inches of exterior EPS under whatever cladding you choose, and even making the partition walls out of a masonry material.

Don't overdo the south facing glass for passive heating- you can always heat with the woodstove, but the summertime gains can be insanely high even from reflected light. Read up on passive cooling approaches (seriously!) With 10kw of array you can do a lot, but there are limits, unless your battery budget is bigger than your HVAC budget.

Mini-splits and most other heat pump designs use a very real amount of standby power even when not actively in use, so to make this work you're going to have to turn the mechanical systems a hard "off". Any parasitic background loads that are normally tolerable with an on-grid system become performance wrecking drains in an off grid configuration, and adds to the size & expense of both the battery and PV arrays. It's a good idea to try living off grid in an existing off-grid house for a month before diving into building a new one.

That last sentence is worth all the rest.

In the 90's we sold the first condensing boilers to some early high-tech preppers until the found out that the pumps required drew 752 watts! This is like burning a cord of wood in a day to an off-grid person.

Frankly, being off-grid in all but the mildest climate is for people who really love to live in a tent. Even with the extreme, but not exaggerated, suggestions Dana proffers, you will have to address internal loads, such as lighting, cooking and bathing with efficient exhaust systems again burning 90 watts and up.

Overhangs are a must in most of Texas.

http://www.greenbuildingadvisor.com/blogs/dept/musings/every-house-needs-roof-overhangs

Some modeling software e.g. Wrightsoft, will allow the use of overhangs in the Manual 'J' heat load calculations.

Dana1: I don't quite believe that any modest cooling system can use more than 9000W of power in the course of a day. I am going to be the only person living in this house, and I can tell you that there will not be many electronics drawing power. I am not going to be living in Leander. I will be living in Lago Vista. The hottest that it generally gets around here is generally in the mid to upper 90s with occasional 100s during the hottest times of the year. The coldest I've seen is either barely or just above freezing. Snow and sleet doesn't usually happen and if it does it doesn't stick. By woodstove, do you mean the wood burning fireplace?

I am buying 4 or 6 Surrette / Rolls Flooded Batteries, which have a 357Ah rating.

Again, the cooktop, oven and clothes drier will be on propane, so the power requirements for those will be low. Which means they will not be using the solar grid for much of anything. All the lighting in the home will be using LED bulbs. As I have mentioned, I do not know how I will be heating my water. I WANTED to use geothermal, but that seems to be out.

I don't think I have seen any homes in Texas with those types of overhangs. I also do not have the expertise to do any of those calculations mentioned.

I do not know any industry professionals, maybe if you can suggest which the correct person that I could locate so they can do all the important calculations...would an Architect do this? Would this light commercial contractor do this? Or is there some sort of HVAC specialist?

BoilerBadger: Which plans were you wanting me to send? Also, which last sentence were you saying that was the 'most important'?

A typical 3/4 ton mini-split draws about 1500 watts at full tilt, but it'll drain your batteries fast running it at full speed.

You'll almost certainly need two of them to be comfortable in a two story house (one upstairs, one down), but you'd never want to have them both running at the same time. In a high performance house the upstairs unit will get the most use in summertime, the lower level unit gets used more in winter.

You'd likely have to schedule your heat pump use with the sun, and use the wood stove to get you through nights or cool cloudy weather. In summer you'll have more PV output to work with, but you'll still have to run the mini-splits while the sun shines and over-cool the place a bit if you can to make it through sticky 90F nights comfortably. Building a high thermal mass house allows you use the thermal mass of the house for energy storage rather than batteries.

Mini-splits (and geothermal heat pumps for that matter) are also sensitive to power quality issues, which means you'd have to verify that whatever you chose actually works well with the inverter you choose for the battery array.

I've looked at a lot of off-grid house designs, but have yet to see one primarily heated & cooled by heat pumps. That's not to say that it can't be done, just that so far it hasn't proved to be the optimal choice for most. There are a few people who HAVE used them off grid, usually some of the Sanyo models that can be set to limit the power draw to 300W or 600W, but most of the accounts I've read are in heating dominated climates with lower cooling requirements than TX.

Cross-posting a bit here...

I had assumed the fireplace was actually an air tight wood burning appliance, not an open hearth fireplace, which is an energy DISASTER that has no place in an off-grid house. A flue sucking air 24/365 is just a parasitic load, dragging humidity & heat into the house in summer, and cold air in the winter. A small air tight wood stove is a far better solution, and can be an efficient heating appliance, as almost all off-grid house designers have figured out.

A small prettified high thermal mass soap stone wood stove with a big flame viewing window can be installed for $4-5K if you have someone else do it all, less if mostly DIY. Hearthstone has a pretty good range of 35-55,000 BTU/hr stoves that could work, with both classic an modern looks, but there are others:

http://www.hearthstonestoves.com/store/wood-products/wood-stoves/bari

http://www.hearthstonestoves.com/store/wood-products/wood-stoves/heritage

Throttled down to ~1/4 of their max firing rate a non-catalytic EPS certified wood stove will still burn efficiently and cleanly, which means you'd be able to get an overnight burn out of one of these during a cold snap if you loaded it to the max once it was already burning hot then dialed it down.

Anything bigger than ~50,000 BTU/hr or so is going to be overkill on a high-R house, but with a high-mass house you can go maybe 75,000 BTU/hr without turning it into a sauna. In a high mass high-R house you'd just set it up to burn at mid-fire and let self-extinguish rather than set it to smolder-mode for 12+ hours of burn.

Assuming it's the Surrette / Rolls 12CS-11PS 12 volt batteries, a 1500 watt 3/4 ton mini-split would be drawing 130-135 amps out of the batteries (with inverter losses) at full tilt. Drawn from 4 batteries that would be about 33 amps per battery. You never want to draw down more than 50% of the full amp-hour rating of the battery or you'll shorten it's life considerably, so you have at most about 4-5 hours at full tilt without excessively stressing the battery. With 6 batteries you'd get maybe 6-7 hours of sunless use out of them, assuming you don't run ANYTHING else in the mean time. I'm not sure if those batteries can really take that much use for long on a daily basis- most prefer much shallower cycles on average.

That's why you'd need to schedule the heat pump use with the availability of the sun, and use the thermal mass of the house to the extent possible, which is why high-mass construction is your friend. You'll have plenty of power during a sunny day, but very limited capacity during darker periods.

A pretty-good unit like the Fujitsu 9RLS3 or Mitsubishi FH09NA you'd get 9000 BTU/hr pf cooling at 90F, or about 12,000 BTU/hr of heating at 32F. A pair of either should come in less than 10 grand, installed, probably under $8K. A mostly DIY installation could get that down to the $5K range. But you have to be sure that your peak loads are within the heating/cooling output range at your 1% and 99% outside design temps.

http://www.fujitsugeneral.com/PDF_06/Submittals/9RLS3Submittal.pdf

https://meus.mylinkdrive.com/files/MSZ-FH09NA_MUZ-FH09NA_Submittal.pdf

A peak heat load of 12,000 BTU/hr @ 32F for an 1800' house isn't a big design challenge, but getting the cooling load down to 9000 BTU/hr takes some judicious window specification & placement. True most of the time on hot days you'd have power directly out of the PV to work with for most of the day, so maybe during the mid-day you'd be fine running a pair of them, but not during the early evening hours. Turning at least one of them off before it's drawing on battery power would be important. To that end, eliminating all windows on the west side would be good, since west facing windows injects solar gain at the end of the day when the house is already hot, and the PV output is fading.

The fireplace is more of a decorative item, but still would be used. I've read that such a fireplace can be built so that it does not create a vacuum which will pull out all the heat. I think you build...something at an angle. Anyway, that's a big ticket item I want for aesthetic purposes. Its not perfect, it's not ideal, but it is what I want. I guess I am sentimental when it comes to things like that. With that being said, those stoves DO look quite nice. And they cost about as much as it would to build a fireplace anyway, so it is something to consider.

About the windows: I want to use solar screens and those double-pane windows which have a high efficiency rating. I don't know what they are called either, but I think this house has maybe eleven windows in all. I use blackout curtains when I don't need or want light anyway, so I can definitely make use of those in this situation.

I can get more batteries if that is what it will take to make this work.

But I highly doubt that I would be doing geothermal, since the cost to drill is extremely expensive.

Edit:

I was looking at these wood burning stoves and I think I can actually be happy with one instead of a traditional fireplace...and if those things truly have the heating capability as is shown, then they can potentially heat the entire home with no trouble at all.

But I am confused. All those numbers represent continuous usage, but most air conditioner systems do not run continuously. Once the area has been cooled to a certain temperature, it comes back on occasionally to maintain that set temperature, right? And I am not sure I recall any summer night being as hot as 90F :-P. Maybe somewhere in the 80s, which shouldn't be too bad to cool from there.

I actually think this will work. I just wanted to let you know that these are budgets that I have set, with some cushion just in case there are unforeseen circumstances. If the budget allows, I have no problem buying additional batteries. They are, however, about a grand each. But I should be able to buy at LEAST six, since I won't have to factor in any HVAC ductwork, as I am going to go with this mini split system.

You mentioned something about a 'high mass' house. What do you mean by this? So a complete masonry (all brick) is a good idea? Maybe with a reflective layer? and lots of rigid foam? I can use light coloured brick just fine, I don't really care what colour the home is so long as it doesn't look like a clown house.

Ideally, you want the thermal mass on the inside, insulated from outdoor temperatures. ICF is kind of a compromise, although there are systems with little or even no insulation on the inside. In my climate, ICF seems to perform very well. I think the thermal mass in the core has a buffering effect. We went from mid September to early January using no HVAC at all this season. We did have an unusually warm fall, but still, it shows how well the walls perform.

Mini-splits rarely run 'wide open', but they do run all of the time. They are inverter drive, which means the speed (and power usage) varies with the demand. Mine only run at full speed when they have a big temperature difference to make up. For this reason, I run them all the time during heating and cooling season, only shutting them off when i know that the house will stay in a comfortable range for an extended period. I don't know what they draw when just 'cruising' like this, but I plan to get a Kill-O-Watt type device to monitor various loads, as I'd like to get my energy usage down. Out of my total electrical usage, the heat pumps are a relatively small percentage, and i want to find out where the power is going so I can correct the problem.

I'm going to play around with solar hot water at some point. It's pretty easy to make collectors, and it should really help in a warmish, sunny climate. It's also fairly easy to store that heat in an insulated tank. You could use it for radiant heat, too.

Hmm, I think I want to try this solar water heating and put that in-line with an on-demand tank-less heater that accepts preheated water (just in case). That should reduce the energy requirements of the tank-less so that it will work with the off-grid system. OR, depending on how well the solar collectors preform, I might consider using a propane-fired boiler instead, but I really don't want my propane to be used on a daily consumer, so we will have to see. And using the solar collectors for radiant flooring + that HE woos stove would mean I would never need to use the heater function on the mini-splits. Is there a such thing as a cooling-only mini split unit?

Cooling only mini-splits are common (more common and cheaper than heating/cooling mini-splits), but the up-charge for a mini-split that does both isn't very large, and allows you to leverage the 10kw PV array to good advantage. With the PV array you'd be able to offset a LOT of propane or firewood use with a mini-split heat pump. But a wood stove is still probably going to be the most practical heating solution for when the sun isn't shining brightly.

Hydronic boiler heating systems use a lot of pumping power, and most bigger-deal tankless hot water heaters use quite a bit of standby power. A third-world type tankless( like some of the Marey units) that don't need power is the right choice for off-grid. Your domestic water pumping is also going to use power. If you have a deep well it's probably going to be important to install substantial above-ground potable water storage and schedule the well pump use to align with the sunny hours too. Battery power is precious, far more costly than straight out of the PV array. (It's about 3-4x as expensive on a lifecycle basis as PV power that isn't cycling through the battery array.)

In your area an in-line batch solar hot water heater in series with a propane tankless could do the heavy lifting for domestic hot water use, without the expense & complexity (read," reliability problem" ) of a full-on active hot water heating system.

Mini-splits run at variable speed, but since you can really only use them continuously while the sun shines the strategy would be to over-cool/over-heat slightly during the sunny hours, and minimize night time use. The 357 amp hour rating of the 12CS-11PS is at a 20 hour draw-down- at higher draw rates it will be quite a bit lower than that. Even at minimum modulation a mini-split will be drawing power a lot faster than than the 20 hour rating. Realistically you're looking at less than 200 amp hours even at low modulation levels. The efficiency of a mini-split is much higher at low speed than when running full out, but if you have the power available during the day to over-cool or over-heat the house by a few degrees it'll be much nicer to the battery. Using high thermal mass materials throughout the house would let you "store up" a lot of heating or cooling wiithout inducing the chills. Unlike battery storage, storing thermal energy in thermal mass of the building materials doesn't shorten it's lifespan, and it's about as cheap as dirt if you want it to be. (Two foot adobe walls, rammed earth, etc.). Throwing more batteries at it is usually the wrong approach.

An active solar-thermal radiant floor heating system would very likely blow the HVAC budget on it's own.

Even a decorative fireplace with a top-sealing flue damper would still have some parasitic draw, and would only run at about 10-15% thermal efficiency while burning. A pretty-good wood-stove would deliver 75-80% thermal efficiency, and in a well-designed high mass 1800' house in your area you'd probably use about a cord of wood per year (or less) if using it as your primary night-time/low-sun space heating appliance, using mini-splits for heating during the sunny hours.

Zoinks, these are some really excellent ideas! And yeah, You've already fully convinced me about getting a wood burning stove instead. I've seen some designs, and I can still have it set on a raised 'hearth' or whatever it is called and still enjoy the look and crackle of a flame that I so desire. Did I mention that instead of using drywall/sheetrock, I want to make use of these 'softwall' fiberglass paneling? It would save on painting, as they are covered with fabric...there are hundreds of patterns and designs available and they are pretty easy to affix to a wall frame. It's just that I've seen FAR too many instances where people have put holes in their drywalls, whether it is their fist, elbow, or even a posterior. I don't want to have to deal with accidents of that sort, and fiberglass has excellent resistance to mold. Here's something: http://www.greatdayimprovements.com/wall-finishing-solutions.aspx What do you think?

I think using a solar heater + propane tank-less would be the best way to go, because I will be honest, I enjoy my baths and showers so much that they are definitely the height of my day, and I don't want to worry about running out of hot water. I've been known to take so-called 'Hollywood showers', but I am sure I will have to reduce my shower time to make this work.

Where would this 'rammed earth' or 'adobe' be placed? Inside the walls as insulation? Could that traditional pink 'fluffy' wall insulation be used? I dunno what it is called, maybe its all fiberglass filaments.

High volumes of hot water are a luxury you'd pay for (most likely in propane.)

With rammed earth and modern adobe the insulation layers are located within the high-mass layers. In some cases the R-value of the material itself is sufficient for hitting the thermal performance criteria (perhaps more true of adobe than rammed earth). Fluffy pink fiberglass batting isn't usually the best way to insulate high-mass buildings- it's designed for wood-framed construction. It only takes an inch of continuous rigid EPS foam to meet code-min performance for high mass walls in your climate, but there's a case to be made for 2" when looking at how much off-grid mechanical systems & PV the higher performance building buys you.

It's common these days to install the rigid insulation within a rammed earth or adobe wall, nearer to the exterior side than the interior, or dead-centered, with 10-15" of high mass wall on both sides of the insulation layer, or 6-8" on the exterior side of the insulation, a foot on the other, depending on the materials and methods. To build with rammed earth or adobe requires finding a competent designers/contractors with those skills.

Rammed earth can often serve as it's own interior & exterior finish walls, when done by artisans who simply love the stuff:

http://www.inspirationgreen.com/rammed-earth.html

http://www.rammedearth.info/insulated-rammed-earth-Canada.htm

If I were personally planning to live off-grid in Texas I'd be looking hard at this approach to building a high performance building envelope. YMMV.

More commonly used higher-mass construction methods include insulated concrete forms (ICF) or concrete block construction (CMU= concrete masonry unit) with rigid foam insulation fastened to the exterior, but they don't have nearly the same amount of thermal mass as rammed earth or adobe, and will require more heating/cooling, but it's easier to find contractors familiar with the materials & methods. A CMU wall with 2" of EPS and a brick veneer or a double-wythe CMU with 2" EPS wedged between the two wythes with an exterior stucco finish and plaster or clay interior can be a decent performer. Building the partition walls out of 4" CMU with a plaster or clay finish also adds useful thermal mass to the house.

If you don't have a competent architect/engineer aiding on the design of an off grid house you're almost guaranteed to be making expensive mistakes. The cost & comfort trade offs between higher building performance vs. HVAC efficiency vs. PV & battery systems are endless, and it should be an iterative process, looking at how much it costs to achieve the desired comfort ends one way vs. another. This is not something easily done on a "design by web forum" basis, even if discussing the particulars is often useful on web forums. If you haven't already been there, the main editor on the greenbuildingadvisor dot com blog lives off grid in Vermont, and would have plenty of off-grid living insights still appropriate to a Texas climate.