Why isn't Net zero design and construction main stream?

Because it's more expensive to build this way.
Also, because it's money that's going towards something non-obvious and "blingy".

Granite countertops?
Travertine tile?
Exotic wood?

These are all very visible to potential buyers.

And, frankly, some people just don't give a damn if they might save some (or even a lot) of money on their bills "down the road".

This is why people buy Porsches and not Isuzus.

It's worse than that. Contractors and construction companies base their bids around doing things a certain way with a work force that is not trained to build efficient houses. When you ask for that the price goes up far more than the extra materials cost or labor and it is going to stay that way until efficient becomes normal.

I'm going to try to get to net zero by building everything myself except site work and concrete. That will let me concentrate on the details and never have a delay based on waiting for one of the trades.

My strategy is to use every square foot I build to the maximum, insulate as much as I can with my budget, build a super tight envelope, buy the most efficient appliances and AC I can and then add grid tied solar with a system that I can add batteries to later and operate off grid in the event of power outage.

I think building what I can as well as I can makes more sense than Passive Haus or other certifications but it probably won't get me in Fine Homebuilding magazine.

I am also not a personal fan of spending money on certifications and I would concur you are far better off using the money to actually improve the building envelope (i.e., the structural soundness and energy efficiency). I prefer ICF for structural soundness. Energy efficiency is best accomplished with some combination of passive solar cooling/heating, insulation and air infiltration sealing. Take the time to do a good cooling/heating load analysis and when you get your monthly operational cost down to 10s of dollars per month using a reasonably priced 1-3 COP HVAC system, you know you are getting close to the optimal design for your location. And if you go Grid Tied, Net Positive isn't all that difficult to achieve these days either...

I was just talking with a friend and we were discussing the insulation of ICF walls and adding additional insulation.

I want to build with an ICF and I have options for the amount of insulation but the base is about R25 and the upgrade cost about $1.50/ft^2, or about $3,000 to do my not terribly large project.

Luckily I am building in an area with excellent solar energy potential and low heating demands in winter.

Instead of paying in to the diminishing returns of expensive wall insulation, I'm going to put more solar on the roof which scales linearly. I will also have heat recovery ventilators (with filters) to avoid wasting the conditioned air and my AC will be zoned with minimal leakage between zones.

Any way, in that conversation my friend was unconvinced but I want to make sure I have an oversized inverter (11.4KW) just in case I ever need to weld during a power outage so the whole $3,000 can be spent on panels and that might bring me from a 5KW system to 8KW so I'll be able to generate about 40KW per day. That should be plenty for AC and typical use. I would say net positive but the moment I start welding or machining that probably goes out the window which is why I want a grid tie.

It doesn't make a whole lot of sense until you look at my potential usage.

I'm not going to be running a professional fabrication shop but I will be doing some welding work, running a mill and lathe and various other power tools on occasion. If I can zero that out, I'll be ecstatic, then my shop cost will only be materials and shielding gas. Adding more insulation could never do that for me.

Exactly so…which is why I said “optimal design for your location"…

Generally however, it is best to maximize the building envelope performance in lieu of throwing money at expensive HVAC or photovoltaic systems. As an example, in our dry diurnal southern Oregon climate (Summer highs/lows of 110/50F and Winter highs/lows of 55/20F), our interior temp would stay within 62-72F all year without any HVAC or photovoltaic systems whatsoever. This is a result of the optimal passive solar cooling/heating design, and accomplishing the required amount of insulation and air infiltration sealing for our location.

We actually keep our interior temp at 68F all year round. Having a large amount of interior thermal mass makes that relatively easy. In Winter we use hydronic radiant floor heating augmented by a masonry heater. In Summer, we open a couple windows at night and run a whole house fan for a couple hours. Our HVAC monthly operational cost never exceeds $30 just using a low cost 1 COP electric boiler for the hydronic radiant floor heating. We don’t need or have any AC whatsoever.

We do have a professional fabrication shop in our remote location where we do machining and welding. However, we use a combination of grid, hydro and photovoltaic as needed to address all of our power needs.

Yes, I'm sure I could design something with passive solar, ground source cooling and massive walls to work in the desert or I could design a less insulated house in Southern Oregon that makes up for it with solar generation.

The question is which is cheaper and I will agree that it is location dependent but solar works everywhere that you have exposure. Insulation works everywhere too but it's the diminishing returns that make a combination make sense in so many situations.

If I was better with HVAC and solar math, I could point to the optimum insulation value for any location but outside of locations close to the north and south pole, I am pretty sure that there is an optimum where solar generation matches HVAC loads and up front cost is at a minimum. Some people spend more than minimum and have excess generation, some people spend more and don't have excess generation because they didn't optimize.

For me, my construction has a minimum, R25. I can't reduce cost beyond that. I am going to need solar so I'm probably going to spend about $7-8,000 on a grid tie system. If that doesn't get me net zero I'm going to add panels instead of insulation. If my minimum insulation was like a 2x4 stick build around R10, the math would be different but solar might win there too. When the highest HVAC load is winter heating when solar generation is at it's minimum, that is going to shift the optimum toward more insulation but I think probably less than you imagine.

I would recommend that you do some basic modeling of different design approaches for your specific location. I think you will learn a lot in the process. Beopt is a popular free modeling tool for residential designs:

https://beopt.nrel.gov/

Good luck with your project!

I have tried an energy modeling web site. I'm not sure how accurate it is because it would not allow me to input options that I think would be appropriate for an ICF home with a R50ish roof insulation, a really tight envelope, heat recovery ventilation and minimal high performance windows. It basically gave payback times for potential efficiency upgrades. With the variables I could play with, extra insulation seemed to have a very very long payback time so my ICF construction seems to already be well past the point of diminishing returns.

My whole point is don't chase diminishing returns if you can spend money in an area with linear scaling.

Even with less insulation than I will wind up with, the payback of an R value increase was only in the tens of dollars a year. I'm not sure if it is accurate because it calculated my HVAC costs at about $100/month. I'm not sure about that. Even if it was way off, it was still pretty obvious that adding solar to offset my energy bill makes more sense than spending a similar amount on insulation if I'm starting at R25.

It is said that 40% of HVAC cost is caused by air leaks but I'm intending to build very tight with continuous membranes, tape and liquid flashing, with spray foam to fill any hard to seal areas. Windows and doors should have good gasket seals and in a concrete wall that barely moves at all, I think they should remain pretty air-tight for longer than typical stick built construction. With HRVs, I think that 40% will only be about 10% or less for me. It is also said that going from R8 to R32 only reduces HVAC cost about 70%. I'm most of the way to R32 and should have the air leak issue pretty much under control so I think I'm going to do as well as typical construction with super insulation and then add solar on top of that to zero it out or go net positive.

I think everyone should use those calculators but they should also be realistic about the paybacks. Throwing insulation at the problem might work in some places but it isn't a panacea because it predictably has diminishing returns.

Maybe I'm spoiled because the path seems obvious and easy for me and I can count on good solar production even if my array isn't aimed perfectly.

ICF doesn't give the return when installed in places where the temp always stays above or below your inside temp. The heat or cold just constantly flows through the wall like a normally insulated wall. In those areas the only reason to do ICF is strength.

ICF shines in areas where the nights are in the 40's and 50's and the days are in the with 70's passive solar heating. I honestly in the spring and fall use NO heating or cooling for 2 months other then a 60 watt tamarack attic fan. So for 1/3 of the year I have no HVAC costs.

What ICF does is heat up during the day and this heat is used to keep the house warm at night and then during the day the walls are cool from at night and it helps keep the house cool during the day.

I live in Michigan. I am almost net zero in a very large house with under 10k of solar and an electric car. Our only cost is water heating at $40 a month for mostly showers. We have 7 people living in the house.

Newboston real world info. that's what is needed here.

Yes, the effective R-value (i.e., the R-value that accounts for thermal mass effect) of ICF can vary immensely depending on the climate temp profile that the ICF experiences in the real world. And Yes, some modelling software definitely doesn’t properly address this. This modelling limitation at the time and getting fatigued from some ICF manufacturer’s endless exaggerated performance claims is what motivated us to accurately quantify ICF performance for different climate temp profiles so we would have accurate R-values to use for our client’s designs.

https://www.borstengineeringconstruction.com/ICF_Performance_Calculator.html

For standard ICF construction (2.5” EPS, 6” reinforced concrete, 2.5” EPS) using our actual diurnal southern Oregon outdoor temperature profiles, we calculated our effective R-value performance to be R21.38 in Spring, R66.15 in Summer, R63.42 in Fall, and R21.07 in Winter. So this is an average annual ICF performance of R43.07 or 1.86 higher performance than the conventional R23.10 R-value. Note, it is the R66.15 in Summer that largely eliminates our need for AC even when we have a couple weeks of triple digit temps. We also instrumented our ICF walls with temp sensors to compare to the calculator results and we found them to be consistent. This wasn’t really at all surprising as heat transfer has been well understood for over a century. However, it is still disappointing that ICF manufacturers still don’t publish accurate performance data.

Insulation is way cheaper than HVAC or photovoltaic systems. Yes, you definitely don’t want to waste money on insulation once you get to diminishing performance returns, but you need to accurately sort out where that is for your location. And thermal mass can often be used to great advantage as well…think Adobe homes...which existed well before there was any HVAC or photovoltaic systems.

I am not saying ICF is the most efficient or cost effective, it's what I have chosen because I like the fire resistance of the block I want and I like the idea of a home that will be going strong in 200 years. When I was pricing out a stick built wall that met my needs for insulation, fire resistance and steel hidden fastener siding, the labor was a lot more for stick built, the price of materials was not much lower and the durability was a bit questionable.

A stick build might last 150+ years if it is protected from water, insects, heat and fire but that includes a siding replacement and possibly new sheathing and exterior insulation. If a car bumps in to a corner, I could get crumpled siding and might move the structure enough to crack the tape joints in areas that would be 100% hidden. It just made sense for me to go ICF so it will be essentially perfect when I die and create some value for my heirs.

In terms of the break even, that reduction of labor is a pretty big payoff because I'm going to be doing almost all of the labor. Otherwise I would say the payoff is instant because of equity. As mentioned above, a really great stick built wall does not increase value very much because people generally don't care. With a concrete wall and knowing that it is almost indestructible and low maintenance, that is going to be a selling feature and add value.

I have taken a peak at the SIP section on here and there are far too many horror stories there. If I was ever looking at buying a SIP built house, I would have to make a deduction just because there would be a big question mark about the durability. Pricing is close to ICF construction too.

The only downside for my application is that renovations that change the layout or footprint of the building are probably more costly and complex. My solution to that is to build what I think I can live with long term and buying enough land to potentially build a second structure for compound life.

Any way, once I made that decision, the question became with a baseline of R25 and a tight envelope should I try to get to net zero through extra insulation for $3,000 or $3,000 of additional solar?

That's the real world calculation, once you have nailed down the basics, doing the math to decide on details.

DIY ICF construction is way easier and often way lower cost than stick built or SIP construction. Frankly, I can’t imagine doing stick built or SIP construction these days with fires becoming an increasing risk. I would not be surprised to see these construction methods banned in CA or OR before too long. And Yes, I fully concur with your perspective.

Great responses….We just want you to do the right thing and understand all the options. I see your points and it seems like you do a have a grasp on your plan. Keep us up to date with pictures....Though I still think your should scrub the Fab Form, but I have never used that in a project but have done mono pour.

Good Luck

Well, stick build can be a lot cheaper. I helped on a stick build that was probably $20,000 or less for about 1,200 ft^2 dried in. There is no way ICF can touch that price but there are ways to make the stick build cheaper if you are really on a near zero budget (free wood from lumber yard rejects).

The difference is that a super cheap stick built home has minimal insulation and every construction material is absolute minimum cost.

I think my cost per square foot is going to be at least twice as high but my materials are going to be chosen for durability and performance. I'm also going to have a lot more time to figure out the details and build them to plan.

That stick built home was quickly built for an elderly couple (with health issues) who were being evicted (the house they were renting was sold underneath them) so it was designed on a napkin and I'm sure some details were less than perfectly executed. It will probably last 50+ years before it is no longer worth maintaining but my 2x cost construction should be going strong with things like floor refinishing being most of the maintenance cost.

The difference in cost should be more than fully compensated for by equity and compensated beyond that by energy savings.

Really? We did our 2,400 SF single level ICF home for $11,000 total two years ago. $5,200 for BuildBlock ICF, $4,100 for 34 CY of 5,000 PSI concrete (including boom pump truck) and $1,700 for rebar. This build was 2,155 SF gross ICF wall area minus 387 SF of door/window openings or 1,768 SF net ICF wall area. And this was a 9.2 earthquake ICF structural design...something unachievable with screen or waffle grid ICCF. Construction photos may be found here if interested:

https://www.borstengineeringconstruction.com/About-Us.html

The $20,000 is dried in, pier foundation, 2x10 floor joists I think, 2x4 framing, I don't remember the size of the rafters. It had plywood subfloor and the roof was decked in MDF with tar paper underlayment and asphalt shingles. I wasn't there on siding day but it was probably about as cheap as it gets. I think that also included doors and windows, interior framing (nothing too complicated), I'm not sure if the $20,000 included insulation but they probably put in fiberglass R13 and a drywall interior.

Your $11,000 is missing a roof, roof structure, floors (kind of), interior walls and probably an exterior wall finish unless you left it Styrofoam. I'm sure yours turned out much nicer but not anywhere near as cheap.

I'm not sure if the land would have allowed a simple foundation footer for an ICF build, it was sloped, not too bad but the pier foundation allowed them to do almost zero site work beside using an auger to drill the holes.

I know I would not put such a cheap roof on an ICF house, mine is budgeted for $10,000. That's $4,000 for standing seam metal roofing, about $2,000 for I-joists, 2,000 for ZipR sheathing, some OSB and 2x8's for the eave framing, about $1,000 for blow in blanket insulation up to about R50, then there is soffit, corbels, rain gutter, etc. I want to do my interior ceiling in Eastern Red Cedar tongue and groove too, that's not going to be cheap (but it will give me some rustic character to go along with my lime plaster interior wall finish). The one place I will cheap out is the flooring, I'm going to put in some of that stone composite vinyl to be cheap and durable and I'll upgrade it later after I have finished doing most of the messy jobs I have planned.

Correct, those are just ICF wall numbers. 2x4 walls are not allowed here. 2x6 walls would have been significantly more expensive. Dried In usually additionally means doors, windows and roof. I am sure we spent in excess of $100K for those additional materials.

For exterior wall finishing, we used fire-resistant Hardie fiber-cement panel and battens for a Board and Batten look. For interior ceiling/wall finishing, we used fire-resistant drywall that was textured and painted. We added wood beams to the ceiling for a mountain lodge style. Floors are 5” thick highly reinforced concrete slabs stamped to look like old wood planks and two different stone styles for a mountain lodge style and they provide our hydronic radiant heating and passive solar heat storage. The slab floors float within the ICF walls, have 4” EPS insulation below them that rests on 12” of self-compacting pea gravel (about 100 tons total) for seismic. So no cold, creaky floors and no significant future maintenance. But none of this is cheap either.

With ICCF and plaster interior finish, I imagine you have to get all your electrical just right as any future modification would likely be painful. ICF makes it relatively easy to initially accomplish electrical and plumbing and any future modification isn’t too painful either although this is always best avoided.

Since my downstairs is a garage/shop, my shop electrical will have some exposed conduit and most of the runs will go up to the ceiling and head to a couple of truss bays where my plumbing and mini-split refrigerant lines will be.

I'll have my upstairs electric running up from the floor and probably have a spot for wires behind the baseboard with plenty of outlets and network runs installed for some level of future-proofing and a lot of it run through conduit so I can pull new wire if CAT6 becomes obsolete before the building does. I'm probably going to put a few recessed floor outlets in the living room area so I can have power under the couch and coffee table for electronic devices and chargers. With my cheap vinyl floor, I can move, add or remove floor outlets pretty easy and patch it up without refinishing or other problems if I just keep a few extra pieces of flooring stored away. My overhead lighting will run up interior walls that are not ICF and then between the roof joists.

I'm going to build some of the upstairs trim removable so that I can access those conduits at strategic spots and have several access panels in the shop ceiling to expose the entire truss bay.

Instead of laying out spaces and putting in the mechanicals as an afterthought, mechanicals are a part of my design and in some cases are dictating the layout of the spaces rather than the other way around. I'm thinking a lot about this kind of stuff. I think my electrical installation should be an easy 2-3 day job, probably with a concurrent plumbing rough in.

In a Log cabin I helped build, a lot of the electrical is kind of buried. It's all in armored conduit but you probably couldn't pull new wire if something failed. It just wasn't designed for simplified wire runs, too many corners and some of them are about as tight as the conduit will bend, then there is the issue of limited access. Also the ceiling tongue and groove paneling is run over the log rafters and has the roof deck and insulation deck screwed in to it from the top. There is pretty much no way to get anything in to the ceiling without removing the roof. Hopefully that isn't an issue for my friend but I'm going to do my ceiling as a cosmetic finish that I can take down and put back up if I want to change something badly enough or even to inspect the underside of my roof deck if it starts leaking.

My heating demands should probably be low enough to use the heat pump feature of my mini-split AC so no radiant heat for me. My slab will probably not be insulated. I won't mind my shop being a bit cool in the winter and it shouldn't have any frost heave issues. I am planning to insulate my upstairs floor joists, for sound mostly but it should let me keep the shop cool without causing cold floors upstairs. It won't be as solid as a slab, I think I'm going to hit 1/600 deflection on my worst span but it's not a long span. Most of my floor should be closer to 1/960 which should be really solid compared to most typical construction. For reference 1/360 is minimum code, 1/480 is fairly normal and 1/720 is considered a much better and pretty high end standard. Of course my plywood T&G subfloor will be glued and screwed so fingers crossed it won't squeak or creak.

Yes, always best to place lots of conduit to future proof a building. We placed more conduit and spare conduit than I can count and it is all easily accessible via attic truss design (see photos). And building to code just results in the crappiest building you can legally build...

I think if I was doing a wood sub-floor for my place again (but after living with heated stamped concrete, I wouldn't...), I would glue it and use pneumatically driven spiral nails. Conventional straight and ring nails eventually get loose. Screws eventually fail from shear stress because of their lower material strength and thread stress concentration points. They use spiral nails to construct wooden shipping pallets. If you have ever had the misfortune of trying to disassemble a wooden shipping pallet, you will understand why I recommend using spiral nails...

Yes, I will have plenty of conduit but it will all go back to that one truss bay, easily accessed from the shop or by removing some baseboard.

Heck, I might just bury some shallow two gang plastic electric boxes with a conduit to the baseboard every couple feet and if I ever need one, I just cut out the plaster over it.

I will have to look at what kind of nail gun those spiral nails need. I was planning to glue and screw because I will have plenty of time and a cordless drill to throw in lots of screws, maybe 60 screws per 4x8 sheet or more if I can get longer sheets of T&G plywood subfloor. That would be about 3 screws per foot over my 2' joist spacing. I will be using a 11.75" I-joist with 2x4 top and bottom plates spanning about 20' which I think is above 1/960 deflection on the span chart. It shouldn't move much which will reduce shear and I'll reduce individual loading by using lots of screws. The PL Premium construction adhesive also has a better bond strength than the more expensive version of liquid nails so that should handle a lot of the shear load too.

Worst case if my floor squeaks, I can add in those spiral nails when I replace my cheapo vinyl flooring in 10-15 years. It's not that I don't like the idea of spiral nails, I just don't want to buy every tool that's out there when I could just use my cordless drill and compensate by using more.

Oh, I have "disassembled" a bunch of shipping pallets but it was smashing them in to the ground to make them diamond shaped and then twisting. They are usually pretty easy to break down for the burn barrel after that. I didn't pay much attention to the nails beside trying not to get stuck.