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Musings of an Energy Nerd

The Evolution of Superinsulation

The net-zero design approach challenges some of the fundamental assumptions of the 1980s superinsulation movement

Thorsten Chlupp's house in Fairbanks required 12 tons of cellulose insulation. The photo on the right was taken from the top of a double-stud wall, looking down, before the cavity was insulated.
Image Credit: Images #1, 2, and 3: Thorsten Chlupp

At the recent “Better Buildings By Design” conference in Burlington, Vermont, I attended presentations that epitomized two different approaches to energy-conscious building. I’ll call these two approaches “classic superinsulation” and “the net zero approach.”

The “classic superinsulation” method has been around for about 35 years. It’s the approach that formed the basis of Wolfgang Feist’s Passivhaus standard.

The “net zero approach” diverges from classic superinsulation by comparing the energy saved by any energy-efficiency measure to the energy produced by a PV system of the same cost.

Thorsten Chlupp travels south from Fairbanks…

At his presentation on February 4, Thorsten Chlupp, a residential designer and builder from Fairbanks, Alaska, made a strong argument in favor of the “classic superinsulation” approach. Chlupp believes that Passivhaus principles can guide cold-climate builders — even builders working as far north as Fairbanks. (Chlupp’s superinsulated “SunRise House” has R-80 walls and an R-115 ceiling.)

Chlupp urged the Burlington audience to get “back to basics.” He said, “We need lots of insulation. Insulation is key.” Of course, Chlupp’s perspective has been shaped by the climate where he builds. “Heating is the problem,” he said. “It is all about heating. We fix that by insulating. Insulating means keeping what we have.”

(It’s certainly understandable that a builder working in Fairbanks, Alaska, has concluded that “It is all about heating.” Chlupp’s conclusion can be contrasted with the conclusion of Marc Rosenbaum, an energy consultant working in Massachusetts, where the climate is considerably milder than the climate in Fairbanks. According to Rosenbaum, “It’s Not About Space Heating.”)

A few more quotes from Chlupp’s presentation:

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  1. Tom_Bassett_Dilley | | #1

    envelope area and comfort too
    The slippery PV value calculations and question of future energy costs seem like they will keep us from an easy answer to the question to ideal envelope values, so I love that you're continuing to probe this, Martin. To confound even more, I think that the larger the building is, the less the envelope drives the energy picture, while internal loads like lighting, water heating, etc., dominate. It looked like the net zero projects discussed in your article were schools, certainly larger than Thorsten's house.

    One other factor that I think is worth putting in (as I'm sure you've mentioned before) is comfort--how good of a window do I need to sit near it and not feel cold? Here in Chicago, it's triple glazed with insulated frames; the same argument for enough insulation under the slab and in the walls. Getting to NZE cost-effectively is a must, I agree, but not at the sacrifice of comfort. That could lead us at least to regional minimums for insulation levels.

  2. GBA Editor
    Martin Holladay | | #2

    Response to Tom Bassett-Dilley
    I agree that there are many facets to this issue. For further discussion of the comfort question, see What is Comfort?

  3. Expert Member
    Dana Dorsett | | #3

    Keeping PV in perspective...
    Even if net-metering fee-adder shenanigans are bound to happen with some financially stressed utilities, by the time the first set of PV is ready to be retired the lifecycle cost of it's REPLACMENT is going to be a small fraction of what it is in 2015. When power is that cheap, (cheaper than all grid sources today), and widely distributed, grid infrastructure expansions will be very limited in scope, and grid costs SHOULD fall.

    If there isn't at least some electricity price deflation starting sometime in the 2020s it is an indication that the state regulators have failed the ratepayer in favor of saving the investor owned utilities from having to write down stranded assets.

    Wisconsin's regulators & major utilities are dinosaurs on their way to rapid extinction if they stay on their current track. Others are walking a very different path in this disruptive evolution of the industry. The dinosaurs will eventually fail, but that's not to say they can't inflict some short term pain with their thrashing on the way down.

    The notion that Net Zero is very important (or even necessary) can be debated in good faith. The grid is getting greener, and can be mandated to become greener faster when the political will to do so arrives. Climate deniers are relatively rare in folks under 30, who will all be middle-aged by 2050, and the voting age non-deniers will be the vast majority. But something like 80% of the buildings that will be standing in 2050 have already been built. Getting serious about mandating efficiency retrofits to existing buildings has a far greater effect on grid load and fossil-burning reductions than making all new construction net-zero (as is mandated in California) The ocean of retrofit efficiency upgrades (not even to Net Zero) is still pretty deep & cheap compared to Net Zero Energy new construction in terms of $/ton of carbon emissions avoidance. Net Zero Energy as retrofit has almost no financial rationale, but "Net Little" energy does, even if it's a moving target.

    Within 10 years rooftop solar may be cheaper on than much or most of the (still necessary by 2050) building efficiency retrofit upgrading, and it becomes a PV real-estate problem. Even if the utility owns PV in large centralized arrays, an all-PV grid has no good rationale, but it WILL drive down the cost of power relative to fossil fuels, even without pricing-in the externalities of fossil burning.

    As a (long-ish) side note: While the nuclear power industry as a whole is a subsidy-pampered expensive dinosaur of a pet, there is some promise in small "walk away safe" molten salt reactors that use the spent fuel-rod waste currently stored at existing reactor sites (with no good long-term disposal plans on the horizon) as fuel. It's conceivable that this, even though still expensive power relative to PV, may become a cost effective means of disposing of that nuclear waste, and therefore desirable, even subsidized (for the valuable nuclear waste processing benefit.). Unlike the existing legacy reactor designs, they need no containment building, and they can't melt down. In the event of auxilliary power failure they automatically drain into a flat tank with a geometry that inherently takes the reaction sub-critical, where it eventually cools into a stable solid. This is basically a big buff-up/makeover of a few experimental reactors that were successfully tested ~50 years ago at Oak Ridge Nat'l Labs, but designed to run at higher efficiency and more complete use of the source energy in the reactor fuel.

    With the existing stock of spent fuel rod currently on hand there is enough fuel to power the world at current electricity use for the better part of a century, no new exotic metals mining necessary. And what you end up with for waste is something with a half-life measured in centuries rather than 10s of millennia. Against the rapidly falling cost of distributed solar & wind, and this sort of nuclear waste reduction (with a huge electricity upside), it's hard to see how fossil burning for electricity has an economic chance, even without the ever-cheaper battery technology that is coming. (Leslie Dewan isn't exactly the image most people get when they picture "nuclear engineer" eh? :-) )

    It remains to be seen if these designs will get traction in the US any time soon. Nuclear power is something of a favorite subject for US DOE secretary Moniz, but the politics of nuclear power have been SO bad for such a long time there is a lot of deafness to anything nuclear out there, and not much appetite for any part if it. This is understandable after failing on early promises of electricity "too cheap to meter" and 60 years of "cheap fusion power within only 20 years", along with the spectacular disasters and near-disasters of the past 40 years. But we have to come to terms with the waste disposal some day, and this may be the cheapest & safest way out. If this path is taken, it too will be a significant distruption of the power generating biz.

  4. Coyo | | #4

    A matter of context and perspective
    Martin made me feel so 80’s! He is so good at stirring the pot.

    Since I give myself more credit than simply arguing that insulation is all you need, I think a few notes are due. First, I warned the audience at my keynote that I am of course biased working in a very challenging climate and environment; 14,000 -18,000 HDD, combined with very remote areas without any road access. Second, let’s get some context on my whole argument of “let’s get back to the basics”. My talk was about cold climate 101, which in my opinion starts with good design, followed by applied building physics and science and best building practices. Start with a good design, I cannot stress this enough. One design feature that is very important to me is resilience. A code approved home in my climate will have a 4 hour “survivability” window before things start to freeze up in the dead of winter when the heating system fails and yes, this is including the occupants.

    Why do I always drum on about “it is all about heating” in cold climates? Simple, because it clearly is the biggest energy hurdle to overcome. Keeping a space comfortable at 70F whilst it is cold outside (in my case -50F) obviously takes up lots of energy. I know, so obvious! I don’t think that Marc Rosenbaum would disagree with me and Martin’s blog about his presentation labeled “It is not about space heating” is really not a contrast at all to my claims “that it is all about heating!”. Why? Simply because it is out of context (and Martin knows that but can’t help put stir that pot!) Marc’s wonderful research is looking at results from monitoring all out electric Net-Zero superinsualted homes at Martha's Vineyard in Massachusetts. His monitoring (and others) reveals that DHW consumed way more energy than the space heating. This is very much in line with my findings on superinsulated homes we build and monitored in Alaska.

    The crux is our baseline on these projects: they are high performing superinsulted homes. There is a dramatic shift in energy use from a code approved home to a superinulated home. In my climate usually 68% of total energy use goes annually to space heating. We can cut this drastically though insulating appropriately for the climate to a point where DHW will use more than double the energy of space heating. This is exactly why I always point to insulation (along with airtightness and appropriate ventilation) first. This is your low hanging fruit. Not only to costs but also in terms of comfort and resilience. In my region with our high costs of energy, we see a 4-5 year payback to go to an R-80 wall. In some remote regions of Alaska the paybacks even come within the first year, no surprise if you have to fly in your heating fuel. How much is enough, do passive house levels of performance make sense? That is an entire different can of worms without any easy answer, and on the PHIUS technical committee we are working very hard to figure out what these levels should be for the many different climate regions of North America addressing the fact that the consideration of cost effective super-efficiency must include solar PV. Believe me after dabbling in this for a few years I can assure you that this is a very difficult question to solve.

    Last but not least – it looks like we are back to arguing PV over insulation. I will be honest, it saddened me to see that this was Martin’s take away from the conference and to see him re-inflame this argument. I felt even worse that somehow my talk got tossed in the mix to get the argument started. Don’t get me wrong, I love renewables. I own a renewable energy company and we sell and install PV. I am not here to argue that we do not need to transform into the new solar age. But I am here to argue that passive methods of conserving should always come first. We are a society of consumers. Producing energy with PV simply appeals to us more than conserving energy by adding more insulation. With the drastic cost reduction in PV pricing we can easily work our numbers to have them triumph payback over insulation. There are many good arguments but please in the end let’s not forget about resilience and longevity. Nobody can deny the beauty of a well-conceived building that simply works, by design and proper insulation, for its 80-100 year life span. No mechanical system will do that. With the help of the grid we can make Zero Energy homes with PV feasible in many climates (good luck in mine). This equation only works for so long. Look at Germany for a reality check if you need one.

    Ultimately we need to consider the question of embodied energy. If you think making sense of costs is difficult, then this one by far tops it. How do we account for the energy it takes to produce a PV panel over insulation? How far did these materials have to travel to get to my jobsite? Does this matter in our job as designers and builders? Most people have no concept on the energy and pollution it takes to move freight around the globe. I ended my keynote talk at the conference on that note ( and I do so in this post; building efficient buildings is simply not enough. We need to strive to recreate local communities. Buy local materials, grow local foods. Use recycled materials where we can, cellulose is a good example. Educate yourself about the issues of international shipping, it’s growth rate and impact on global emissions, that is already surpassing the carbon footprint of Germany.

    We can debate about any of these things all day long but please, let’s not forget that in the end we all want the same: build good buildings and have a future for our kids.

  5. GBA Editor
    Martin Holladay | | #5

    Response to Dana Dorsett
    I agree with your prediction: "By the time the first set of PV is ready to be retired, the lifecycle cost of its REPLACEMENT is going to be a small fraction of what it is in 2015. When power is that cheap (cheaper than all grid sources today) and widely distributed, grid infrastructure expansions will be very limited in scope, and grid costs SHOULD fall."

    That's why I wrote, "PV-generated electricity is dropping in price, but it is still relatively expensive compared to electricity generated by other means, including electricity from hydroelectric facilities and wind turbines. Designers who assume that the future price of electricity will be roughly equal to the current cost of PV-generated electricity are unlikely (it seems to me) to be surprised by future electricity price hikes."

    Making predictions about future energy prices is tricky, and I've been wrong before. But the evidence supporting a prediction of lower electricity prices in the future is fairly strong.

  6. GBA Editor
    Martin Holladay | | #6

    Response to Thorsten Chlupp
    Thanks for your comments -- and thanks for your groundbreaking work in Alaska. Thanks to you, cold-climate builders have a new understanding of what's possible in your very demanding climate. All of us who build in cold climates are indebted to you.

    You're right, of course, that my article sets up a contrast between your approach to design and the approach taken by John Rahill and Charley Stevenson. When a journalist sets up a contrast like that, there is a risk of oversimplification.

    That said, I think that for anyone living in a location where the local utility offers favorable net-metering contracts -- in other words, in most locations in the U.S. -- cheap PV raises new challenges to traditional thinking about superinsulation.

    You report, "In my region with our high costs of energy, we see a 4-5 year payback to go to an R-80 wall." Since you have done the math, I applaud you. (That's why I wrote, "Thorsten Chlupp tells clients that investments in very thick insulation makes sense in Fairbanks, Alaska. He's right. An argument can be made that in interior Alaska, investments in insulation that is thicker than cost-effectiveness calculations justify is reasonable — if only to improve a building's resilience.")

    For designers and builders in milder climates, however, I will repeat my advice: sharpen your pencils and do the math. Many clients are unlikely to want to spend an additional $1,000 on attic insulation when $1,000 of PV modules will save them more on their energy bills.

    My article notes that the Wisconsin situation has caused me to rethink this issue; I wrote, "I don’t have an answer to the question posed above." Every designer (and homeowner) needs to come to their own conclusions, and to determine envelope specifications based on how much money they are willing to invest in resilience, and on where they think electricity prices will end up.

  7. G. W. North | | #7

    Oh one more thing..
    I am a new member, above was my first posting. How did I do??

  8. Expert Member

    So does the source of your grid make this an individual decision, or perhaps one based on location? My power is generated ten kms up the road at a hydro dam. How much should I still link my building choices to larger public policy issues?

  9. G. W. North | | #9

    In my humble opinion. Not by location but by source. If your clean and close energy source is connected to the grid you must consider it is XX% dirty (same as the grid it is connected to). You should throw nearby cities with their gas into the mix because the politics affect (infect) the system as well.
    Your 10 km away hydro dam may supply a factory 600 km away at times. This is a waste due to resistance! Remember who is behind the grid! Just say no.

    That dam should disconnect from those who will not cooperate (go all renewable stay local -enough). The dam should turn off when the sun is shining or the wind is blowing(come on a little technology here) and turn on when it is dark or the air still...
    Malcolm if you and your neighbours (and a few fairy god mothers) got together....Yes you should link your building choices to larger public policy issues. Know that it will never happen- forget public policy - it really really is a lost cause.

    The ONLY WAY TO GET REAL IN ENERGY IS TO FORGET GOVERNMENT-GO OFF GRID. I am not -yet but that is the only way it is going to happen and I am sure I am not the only one who knows that.

  10. GBA Editor
    Martin Holladay | | #10

    Response to Tom Willemsen
    You wrote, "The only way to get real in energy is to forget government -- go off-grid." (Except you used all caps.)

    I have lived off-grid for forty years, so I'd like to provide my perspective.

    In the early years of my off-grid existence, my CO2 production was fairly low. Most of it came from my vehicle, of course. Off-grid homeowners tend to live in rural areas, so our carbon production for transportation tends to be much higher than that of urban residents.

    The rest of my CO2 production came from my kerosene lamps. The amount was minor.

    Over the years, my lifestyle ramped up. This is either understandable or shameful, depending on one's perspective. My house now has a refrigerator, a washing machine, a few computers, a computer printer, and a television, as well as electric lighting. My PV system doesn't keep this equipment running in the winter -- a gasoline-fueled Honda generator does. Because of my Honda generator, my electricity is dirtier than that of my neighbors in Vermont, who get most of their (grid-supplied) electricity from hydroelectric facilities in Quebec, as well as a local wind facility.

    Summer and winter, my electrical system depends on a very large, very heavy set of lead-acid batteries. They are important enough to get their own (small) room in the house. They are somewhat of an environmental nightmare, but that's the price one pays to enjoy the off-grid lifestyle.

    In short, going off-grid is no panacea.

    In the U.S. right now, PV produces less than 1% of grid electricity. Every U.S. homeowner who installs PV is helping make the grid a little cleaner, since 100% of the PV electricity fed into the grid displaces electricity produced by other means. For that reason, I salute owners of net-zero homes.

    Sometimes I get questions from homeowners who plan to build a house with a big PV array on the roof. They ask, "Should my home be grid-connected or off-grid?" My answer is always, "If possible, connect to the grid. The grid is the most efficient way to handle the overproduction of electricity in summer and the underproduction of electricity in winter."

  11. G. W. North | | #11

    Response to Martin Holladay
    You used kerosene lamps for light! whoa you must be old! was that picture of you taken twenty years ago? Distance from a line causes many people to off grid. Do you plan to connect to the grid or is it still too far/expensive?

    My point is we need solutions that address CO2 not mere payback. We use too much energy and to cover that requirement is too difficult with renewable energy (as in Mackay’s book –Without the Hot Air).

    It is legal, even encouraged to have electric heat. Now how are we going to go all renewable (at least with building energy and most personal transportation) with a country full of electric elements blazing? We are not.

    With CO2 hitting 400 PPM it is still legal for refrigerator manufacturers to provide only 1 inch of insulation (don’t be fooled by thick door -look at the sidewall) even with vast temp difference between inside frig and house 24/7/365.

    It is still legal for hot water heaters to have a mire inch or two of insulation. Shame on big business and shame on government. Proper insulation of refrigerator and hot water tanks is low hanging fruit and they still don’t ban poor design. Bell Canada will give you a PVR for your dish that uses 45 watts in the off position! Where did that design engineer get his degree?

    Academia could easily shame governments in making a change but they don’t want to risk funding cuts!

    Another major problem with the net zero method is - it fails if it wins! The grid does not store energy. Ok if a few rich folk (in Canada that means you work for/with the government) throw PV energy in the grid but everyone can’t do it. Centralized seasonal electrical storage (with losses) transporting electricity long distance (more losses) is not practical for renewable electricity.

    If your major portion of home energy is for heat (of home and hot water) and you want to do it renewably, you need storage. We in cold climate countries need to get good at it. We need to properly insulate (or super-insulate as you call it) NOT for pay back but to wipe out CO2 production.
    We also need low cost methods of seasonal heat storage. It must be law sooner or later, I don’t know how we are going avoid that one.

    We need to replace the annual visit of the furnace man (to look at the complicated furnace) with the thermal person who checks on things on a proper and properly installed thermal system. PV can make a bit of heat but not that much with low enough cost especially for winter.

  12. morganparis | | #12

    The Holy Grail of solar thermal
    ".... solar thermal will continue to be really really alive (you can store a winters worth of heat at home)"
    You make it sound easy, Tom. Wish it were so.

  13. GBA Editor
    Martin Holladay | | #13

    Response to Tom Willemsen (Comment #12)
    You are no longer urging us all to go off-grid, it seems; instead, you are advocating in favor of improved appliance efficiency standards. Your point is well taken (and isn't particularly controversial).

    So we all agree that improved appliance efficiency standards are a good thing. (Incidentally, the DOE has made great strides in improving appliance efficiency standards in recent years -- so we're moving in the right direction on that front.) However, there is no need to berate grid-connected homeowners who decide to install a PV system. These homeowners are part of the solution, not part of the problem -- so let's support them, not berate them.

    Q. "Whoa, you must be old! Was that picture of you taken twenty years ago?"

    A. I'll be turning 60 next month. Wrestling with energy policy issues keeps me looking young.

    Q. "Do you plan to connect to the grid?"

    A. No.

    Q. "Academia could easily shame governments in making a change but they don’t want to risk funding cuts!"

    A. I don't go in for conspiracy theories. Almost all of the academic researchers I have met are honorable women and men who follow the scientific method and report data accurately. We are all indebted to them for their important work. Academic researchers like Bill Rose produce the data that can be used to try to convince government regulators of desirable regulatory changes.

    Q. "We also need low cost methods of seasonal heat storage. It must be law sooner or later."

    A. "Low-cost methods of seasonal heat storage" is an oxymoron. The laws preventing us from achieving that goal are not the laws of the U.S. or Canada -- they are the laws of physics. It's much harder to battle the laws of physics than the laws of the land -- but good luck to you.

  14. G. W. North | | #14

    Physics and the Holy Grail
    The IEA has vastly reduced it’s mandate on researching seasonal energy storage why? Because it has been proven to work and not such a holy grail. Even Mr. Chlupp is walking on water! (and it’s not heated with PV I might add).

    I did not stop urging us to go off grid, in fact it would be MUCH easier to go off grid if we could buy some decent (low energy consuming) appliances for not too much money.

    I too like researchers but they don’t run universities. I too have not always made the best energy choices and do not blame anyone for going for 13-15% interest on their money (micro fit) for 20 years backed by our government. I don’t blame them for going for the green…

    What I am saying there is there are better ways. The better ways speak to effective CO2 reduction in a system that will work long term for everyone.

    Seasonal heat storage will never be cheap and neither will the foundation for your house but we still need one. What I am saying is: like a foundation a house needs seasonal heat storage in order keep CO2 accumulation at bay. My system is 75% complete-hope it works!!!.

  15. GBA Editor
    Martin Holladay | | #15

    Response to Tom Willemsen (Comment #15)
    In Comment #12, you wrote, "We also need low-cost methods of seasonal heat storage."

    In Comment #15, you wrote, "Seasonal heat storage will never be cheap."

    These two statements aren't exactly in alignment. I agree with the latter statement, however.

  16. dankolbert | | #16

    Molten salt reactors
    Dana - I had never heard of thorium MSR's until a couple of months ago, when my son (a HS junior) chose it as his topic for a section on energy policy his school is doing. I was amazed at what he showed me. As an old No-Nuker (of Shoreham and Seabrook vintage) my anti-nuclear-power bias goes pretty damn deep, but I agree that these are compelling on various fronts.

  17. Expert Member
    MALCOLM TAYLOR | | #17

    "If your clean and close energy source is connected to the grid you must consider it is XX% dirty"

    You've lost me there. That's like saying: you live on a nice road, but if you follow it far enough you end up in Vegas, which I think is bad place. I agree with a lot of your criticisms, but your solution of avoiding contamination with the evil modern world is ultimately self-defeating. Chomsky was asked this in an interview some years ago: What is the effect of withdrawing from consumer and civil society? He answered that the practical result was you didn't exist.

  18. Coyo | | #18

    Thanks Martin
    ...for the kind words. There is certainly no clear cut answer and in the end we as individuals need to make choices. Like with everything else in life.

  19. G. W. North | | #19

    Chomsky may be right and I think keep society, community and your friends- just go off grid so you don’t help fossil fuel pollute with CO2. The energy grid is only that – it is not the whole world.

    To clarify what I mean when I pull energy out of the grid I am causing certain amount of fossil fuel to be burned depending on time of day or year (not as bad in Canada due the blessing of hydro resources). Hydro though is a finite resource. It gets used up and fossil fuels are used as backup. Its like having a generator but it is in someone else’s back yard.

    With good design and planning I believe we can avoid participating in an energy system that continues to pump massive amounts of CO2 into the air. A system that “net zero” wants to make appear clean. They should be forced to change the name. “net zero”? Really? We don't want to balance things out -we want to avoid CO2. "Net zero" is by no means net zero CO2.

  20. GBA Editor
    Martin Holladay | | #20

    Response to Tom Willemsen
    Participating in our economy involves compromises. If you use grid power, you are using electricity that is partly generated from coal plants. One possible solution, as you suggest, is to go off-grid. I tried that in 1975; by sharing my story, I hope that you understood my point: a truly fossil-fuel-free life is difficult.

    When I was young, I tried to avoid the moral compromises that accompany supermarket shopping (tomato pickers aren't paid a living wage) by trying to grow all my own food. It's tough. I tried to avoid the moral compromises that accompany paying federal taxes by keeping my income below the taxable level. Again, it's doable -- but tough.

    These days I participate in our flawed society a little bit more than I did when I was 22. That involves compromises -- but it doesn't require that we give up on struggles to achieve social justice or better environmental policies. It's good to struggle for social justice and in defense of the environment. But a sober analysis of our own complicity requires us to acknowledge that our actions are imperfect. Moreover, participating in our social system -- interacting with our neighbors, getting involved with local government, acknowledging our inter-dependence instead of striving for self-sufficiency -- has its own rewards, one of which is to make our communities stronger.

    Most of us need to use some grid electricity (or fossil fuels) now and then. To be responsible, we need to try to reduce our use of dirty energy, and to contribute efforts to making the grid a little greener every year. Putting PV on the roof of your house is an excellent step in the right direction.

  21. Expert Member
    Dana Dorsett | | #21

    The grid is not one machine (Tom multiples, and Dan Kolbert #17)
    "In Canada we are doing well, we are only 80% dirty energy (overall). Why would I want to put clean energy into a dirty grid?".

    Location on the grid relative to the generating resources actually matter. The transmission capacity is not infinite, especially when looking at longer distances. The local grid generators ARE the primary source of the power going into your loads, even if the local grid is sometimes sipping some amount of power from a long-haul transmission line (and paying for that capacity use, not just the energy.) The notion that because a nation had 80% dirty sources means that somebody plugged into Quebec's mostly hydro grid is 80% dirty is utter bunk- it doesn't work that way. Your pulling power from the grid does NOT automatically create a carbon release. (In nuke-heavy grids pulling off-peak power is sometimes reducing the amount of heat they have to dump into the rivers or send up the cooling towers.)

    The notion that hydro resources get "used up" and need fossil burners as back up is also simply not the case. All grid resources back up all other grid resources, within the grid transmission capacity (and financial) limits. Wind & PV "back up" hydro too (and conversely). Since grid operators use price signals to get generators to put more power onto the grid or cut back, resources like wind & PV & hydro that have effectively no marginal per-kwh cost set the price- they're cheaper than fossil burners, all of which have a marginal fuel cost. This is what is putting low-efficiency legacy coal plants out of business (and some high cost legacy nukes too) in the upper midwest of the US and on the Texas ERCOT grid.

    That's exactly why you would "...want to put clean energy into a dirty grid...". Putting zero marginal cost PV onto a tainted grid is an effective way of greening that grid up, reducing the carbon load of all users of that grid, and reducging the share sourced by 25%-30% thermal efficiency coal operators (if not driving them out of business just this week). Also, by reducing the net load on your side of the substation it reduces the size of the spinning reserves currently required to keep the local-grid stable by reducing grid congestion putting off or eliminating the need for capacity upgrades at the substation level. Going off=grid with the resources has very low cost-efficiency in terms of $/ton of total carbon reduced in your dirty-grid region. Defecting from the grid may make YOU near-zero carb, but sharing the resource results in a greater carbon reduction per dollar invested. For a policy to be truly effective, it has to be cost effective.

    Also note, the grid-at-large is still getting greener by the day. Any carbon footprint per grid-sourced kwh is getting better over time. In many locations (including mine) you can purchase your power from a low-carbon supplier (usually through brokers, at the retail level) under a power purchase agreement. Even if the generator is somewhat remote from your local grid, that is still power that is going onto the grid somewhere in preference to some other resource. (At the moment I'm paying 12 cents/kwh for 100% wind under a brokered PPA under a 3 year agreement, which as it turns out is even less expensive than the local tainted-grid standard mix offered through the utility that is running ~16 cents/kwh this winter.)

    "The IEA has vastly reduced it’s mandate on researching seasonal energy storage why? Because it has been proven to work and not such a holy grail."

    Do you have references on either of those assertions? Seasonal storage using aquifers & heat pumps or large scale solar thermal are fairly expensive, and I don't know any that comes even close to working on the micro scale.

    The lifecycle $/MMBTU in Drakes Landing district heating is pretty steep, and doesn't scale downward to the local-neighborhood or single family house level very well. When PV hits $1/watt and batteries hit $75/kwh (both price points are likely to occur prior to 2030) it's going to be cheaper to go with air source heat pumps and a much smaller amount of thermal + battery storage to cover those loads in that Alberta location. ( A location north of the Arctic circle with have much more difficult design constraints.) That may take 2x the PV it takes to get to a grid-tied net-zero, but even 2x the PV at $1/watt is less than half the average cost of rooftop PV was the US in 2013. And unlike seasonal storage schemes, it's scalable. The notion that you even NEED seasonal energy storage to go near-zero carbon isn't necessarily valid. Enough PV to handle the wintertime insolation variability and sufficient storage (thermal or electric) for a handful of days would pretty much get you there.

    Dan: While the inherent fail-safe aspects of thorium reactors is attractive, it's still going to be an expensive, and fairly inflexible technology, with most of the ramp-rate slow response issue of the current nuke fleet. What's particularly attractive about Leslie Dewan / Transatomic's MSR design is that it uses spent fuel rod from legacy reactors, not newly mined thorium as the fuel. Spent fuel from the legacy fleet has serious storage, transportation, disposal & political problems. The economic value of disposing of that material by USING most of the residual energy in it while reducing it's radioactive half-life by orders of magnitude is real, even if they GAVE the power away at $0/Twh Rather than creating a long term environmental problem (the way mining thorium does), it solves one.

    Even though it'll still take 5 centuries for the re-used spent fuel from the MSR to hit relatively safe levels, a handful of centuries is a time frame for which humans can engineer reliable & safe containment. The stuff currently that takes 10s of millennia to hit safe levels sitting in cooling ponds & steel cannisters at legacy nuke sites has no known reliable solution. Since the MSRs are comparatively small (no containment structure necessary) and scalable, retrofitting them at existing legacy nuke sites as part of the decommissioning of the legacy nuke seems do-able. Putting them on existing nuclear plant sites would not require carting the hot spent fuel more than a few hundred yards, rather than some remote repository 1000s of miles away (that may or many not really work for the required amount of time.)

    Until they build out a few the actual costs are not known, but it has to be cheaper per kwh than nukes based on legacy designs, due to the comparative simplicity and fail-safe nature of the beast. The power output benefit is also substantial (considerably more lifecycle power that has been delivered by nukes to date), so as a disposal strategy these nukes have a much stronger rationale than for thorium reactors. Even if it's 5x the lifecycle cost of PV in 2050, it's still "worth it" for the waste processing value, whereas thorium reactors may well be priced out of the market by then.

  22. norm_farwell | | #22

    The problem with scaling up a net zero approach
    Thorsten makes a critical point. The Germans, who have made more progress in these things than most people, are starting to run into problems that are interesting and should make us wary of pursuing a supply side net-zero approach. Although insulation and PV look like two paths to the same point, the affordability of the net zero approach might be an illusion if widespread adoption of renewables destabilizes the grid and we all have to pay for the fix.

    My understanding is that the Germans have found that managing grid infrastructure and reliability gets more difficult as the percentage of renewables increases. They are even contemplating some kind of radical reform of the energy market itself. So the first net zero house is not a problem for anyone, but after ten million of them.... it's Hamburg we have a problem.


    As the discussion paper points out, there are no similar problems with the widespread adoption of conservation measures like insulation. Saved energy is the cheapest least complicated energy there is. Future grid stability and the continuing affordability of PV power may depend on demand reduction.

  23. G. W. North | | #23

    I stated "The IEA has vastly reduced it’s mandate on researching seasonal energy storage why? Because it has been proven to work and not such a holy grail." Dana you asked "Do you have references on either of those assertions? "

    I don't know where the specific references are (I may have heard it at a conference) however I can clarify a bit.

    They are still working on thermal energy storage but less on in ground and aquifer storage and associated modeling due to knowledge gained . Now research is geared more toward phase change materials and chemical storage.

    I agree that a lot of work still needs to be done in getting the costs down especially for individual homes. Home based thermal storage, like going off grid with PV is an another effective way to remove government from energy decisions/stop burning fossil fuels.

    Lower cost seasonal heat storage and low cost thermal collection are two areas that I am interested in/working on (as much as possible due to research funding not typically available outside university walls) as much as my own funds and time allow.

  24. Marc Rosenbaum | | #24

    comments on many good thoughts
    You'd be hard-pressed to find any fundamental disagreements between me and Thorsten. The basis of my statements at the PH conference in Portland assume the building is superinsulated. We can argue about what that means, and how it differs across varying climates. but no one posting here isn't prioritizing conservation.
    It's good to include the cost of renewable electricity in analyses of optimum insulation values, but as the price drops eventually the "optimum" enclosure won't even meet code. I've advocated to PHIUS that the standard evolve to have no criteria beyond a primary energy per person limit, an maximum air leakage in CFM50 per sf of enclosure, and maximum heating and cooling design loads per sf. And I've advocated to include PV energy to the extent that it is used on site rather than exported, to put it onto the same footing as solar thermal energy.
    Martin's observation about net metering policy being a malleable thing that may well become much more restrictive is a fundamental one, and one that as a co-owner of a company that installs PV I am concerned about. However, tightening of that policy will accelerate development of appliances that will integrate electrical (battery) and thermal (I'm guessing phase change) storage, so buildings can stop relying on net metering. The utilities will continue to tighten their own noose. Meanwhile, we need to make sure our buildings are resilient and comfortable, while avoiding carbon sequestration via two feet of insulation under basement slabs :-)

  25. Expert Member
    Dana Dorsett | | #25

    Grid stability (response to norm farwell)
    Germany's grid isn't a great paradigm for US power grids, in that the geographical area and pre-existing transmission resources are smaller than in most US grid-regions. And still, without wind & solar they would have had blackouts from closing down nukes as rapidly as they did, but with wind & solar they still have higher grid reliability than in the US (go figure!) Tales of difficult grid management on a variable-renewables heavy grid are much talked about, but rarely seen, and barely seen at all in Germany. The neighborhoods where rooftop PV backfeeding the local grids in Oahu is a better example, but one with clear solutions (behind-the-meter battery storage being just one.)

    In the wind-rich parts of the US such as ND & IA more than 25% of all power shipped on to the grid in a year is generated by wind, and not always at a time of day when that power is needed- it's sometimes in excess of 100% of the load. But when the spot-price goes negative there are ready buyers on the other end of transmission lines, and actual curtailment of output is rarely needed. Rooftop PV occurs at a time of day when grid loads are generally high, and it takes quite a large penetration of solar (higher than Germany's) before that becomes a real problem. But cost-effective remedies for stabilizing renewable grids already exist- it's a matter of adjusting the utility regulatory environment and utility business models to make that happen.

    Now that Oahu's utility company has been bought out by a more renewables-competent company than the prior management I expect some of their mid-day backfeeding issues will be dealt with by means other than limiting new PV on the neighborhoods that are backfeeding the substations. New York's re-write of the regulations looks like it will allow utilities to subsidize PV & storage in neighborhoods with overstressed feeders (and base-rate the cost) at rates different from other areas, to avoid the capital cost of upgrading the substations &/or utility-owned storage.(or peakers).

  26. Expert Member
    Dana Dorsett | | #26

    The cost of PV vs. insulation (response to Mark Rosenbaum)
    The whole business about PV having a lifecycle cost than insulation at lower insulation levels than code min is real, and the balancing point is worth thinking about. But it's more than the cost of PV, or carbon content, it's also the real-estate required.

    Right now it takes a pretty good building envelope well above code min performance to fit a PV array capable of Net Zero on the roof of a shoe-box-with-gable shaped house with the PV leveraged by current -generation heat pumps. But that is with 15-20% efficiency PV panels with an installed cost north of $3/watt and seasonal COPs of 3.5 or less. There are a couple of likely paths to getting commodity panel PV efficiency north of 30% efficiency, even as the installed cost trends downward. At 30% PV efficiency a carefully designed house at IRC2012 code-min levels could conceivably get to Net Zero with an array that fits on the house, assuming modest incremental improvements in heat pump efficiency by the time that happens. At a buck-a-watt PV it's going to be hard to make the financial case for taking it much higher than IRC2012 on the building envelope, maybe some, but not much. There is still a comfort case to be made for higher building performance, primarily for higher performance windows in colder climates.

    I've seen a draft proposal for IRC 2015 that would make U0.20 code-max for climate zones 4 & higher. That may be financially rational in some cases, but in many, not, not even at today's energy prices, given the high cost and limited lifetime of U0.20 windows. I'm skeptical that if that becomes enshrined in IRC 2015 that any states in zone 4 will take up that standard without revision, but some in zones 6 & 7 might.

    To be sure, PassivHaus levels of building performance aren't likely to be the most cost effective way to reduce carbon in 15 years. It isn't even today, in places with greener grids, and as distributed power and greener more centralized power (such as utility scale PV & wind ) goes online, nearly all grid locations are becoming greener at an accelerating pace.

  27. GBA Editor
    Martin Holladay | | #28

    Response to Marc Rosenbaum
    Thanks for your comments. I'm glad that you and Thorsten Chlupp are in substantial agreement. In spite of our group hug, however, anyone designing a superinsulated house still needs to wrestle with the question, "When do I quit insulating?"

    In states with strong political support for existing net-metering contracts that allow homeowners to run their meters backwards, with the meter re-set to zero only once a year (rather than once a month, as is the case in Wisconsin), many homeowners may feel fairly confident that existing net-metering contracts will be honored for one or two more decades.

    If that's the case -- and of course it's based on assumptions rather than a certain knowledge of the future -- I can understand the logic of building a home that simply meets minimum code requirements for R-values, especially if the home had good solar exposure or a large back yard. (Ideally, the builder would aim for a very low air leakage rate.) Any extra money could then be invested in PV, where the invested dollars would yield a better return than envelope improvements.

  28. GBA Editor
    Martin Holladay | | #27

    Response to Norm Farwell (Comment #23)
    You wrote, "My understanding is that the Germans have found that managing grid infrastructure and reliability gets more difficult as the percentage of renewables increases."

    As Dana responded, it's unclear whether Germany has reached that point yet. However, you are correct that eventually (as grid operators in Oahu have discovered), when PV penetration increases to a certain point, grid operators need to respond with new technical solutions to accommodate the PV-generated electricity.

    In the 48 contiguous U.S. states and Alaska, however, where PV contributes less than 1% of our electricity, we are a long ways from that point. In most cases, the fear of grid instability arising from too much PV is simply a red herring introduced by grid operators who are fearful of inevitable changes. (In Wisconsin, where grid operators raised an alarm about the PV threat, there are fewer than 1,000 grid-connected PV systems in the entire state!)

    It would be a shame if this red herring interferes with efforts to increase PV installations, since a transition to renewable energy sources is an essential step towards stabilizing our climate.

    Let's see if we can nudge the needle to 1%, and then 2%, and then 3%. We're a long ways from 30%, so the alarmists need to take a deep breath.

  29. G. W. North | | #29

    "When do I quit insulating?"
    This is my take on the question "When do I quit insulating?"

    It goes in stages and the insulation gets thicker at each step (also progresses from concern for self to concern for everyone)

    1. To survive.
    2. To be comfortable
    3. To (merely) save money.
    4. Maximum CO2 reduction over the life of the building (minimum 80 years).

    If we are on stage 3 and want to save some money we will look at any extra insulation and say –what is the return on the last half of insulation thickness? In cold climates we will get stuck with 2X6 or 2X8 thick walls. We will use a shorter term approach 25 years or less – when the appliance quits, when the subsidy contract runs out.

    If we advance to stage 4 max reduction of CO2 rules; we utilize insulation better, use a longer term approach(insulation lasts). In colder climates this is where the walls separate.

    With double wall construction instead of “what will the last half of the thickness give me?” I ask what would it cost to move the wall out another 12 inches? The answer is : not nearly as much as the first half.

    What thickness is that? I don't know exactly but from what I have seen too many factors get ignored and the insulation ends up so thin that fossil fuels get burnt, that we must stay connected to the grid and that "net/not zero" makes sense .

    The "dangers" of too much insulation are so so minor amid a sea of additional benefits.

  30. G. W. North | | #30

    So storage is inevitable "Net Not Zero" Versus Off Grid
    Happy 270th Birthday Alessandro Volta !

    Martin thank you for your easy to understand explanation of just how far away United States (and it seems Canada) is from over powering the grid with Renewable Energy. I think it is important to reiterate that we want renewable energy because we have to stop putting CO2 into the air.

    I think that the steps we are taking are too small and not a logical progression to a society that has embraced renewable energy. That we should leap frog instead of continuously changing / small step strategies. But how?

    Do you know of any comprehensive studies that compare two different mass roll out scenarios designed to combat the production of CO2? More specifically:

    The “net zero” approach (a reminder that CO2 IS produced so it is not zero, and you can’t take it back once you have already caused it’s production).


    The off grid approach. This is decentralized generation AND storage at the point of use and does not set the grid up for failure. A generator will likely be employed or some hybrid approach.

    If anyone has seen such a comparative study please share. It would be especially nice if the off grid strategy is not based as things are now but when some regulations have been improved:

    Vastly improved insulation thickness in buildings, in refrigerators, and hot water heaters, improved solar thermal and seasonal heat storage.

    UL CSA: when it is illegal to sell a device where the wall wart (transformer) does not switch off automatically when the device is not using power.

    Additional improved strategies to lower energy required during periods of lower renewable energy production. (the frig can use cold air from outside in the winter as an example).

    It would be interesting to see how these scenarios (along with an accelerated roll out of electric vehicles) would play out in terms of CO2, costs, jobs, and how widely the approach could be adopted.

  31. GBA Editor
    Martin Holladay | | #31

    Response to Tom Willemsen
    Q. "Do you know of any comprehensive studies that compare the net zero approach to the off grid approach?"

    A. No, but I think that you are giving too much credence to the idea that any researcher would seriously consider that eliminating the grid in favor of an off-grid approach makes sense. The grid is an extremely efficient way to handle different levels of energy production and use among neighboring homes.

    There are so many flaws to your excited embrace of the off-grid solution that it's hard to know where to start. If you expect homes to be able to get through the dark, cloudy months of November, December and January with electricity that is generated on site, they will need a lot of expensive equipment: a wind turbine, a generator powered by an internal combustion engine, or an extremely large PV array and battery system. Once you have installed this expensive equipment in every house in town, what happens to the extra unneeded electricity that the system produces in June? It is wasted, of course, because there is no grid to share this unneeded power.

  32. dankolbert | | #32

    You get an A
    for Effort.

  33. Expert Member
    Dana Dorsett | | #33

    response to Tom Willemsen(#30)
    "4. Maximum CO2 reduction over the life of the building (minimum 80 years). "

    That is not a knowable number, since the grid carbon per unit of energy changes over time, and is getting greener over time.

    Nor is the same in every location: In hydro-heavy Quebec even code-min insulation does not make sense for an electricity heated house from a lifecycle carbon reduction point of view. In Germany the lifecycle carbon hit for an electrically heated PassivHaus is many orders of magnitude than a code-min electric-baseboard heated house in Quebec, despite the much larger energy use of the latter.

    Using hydro power in Quebec or British Columbia does not require a fossil burner to fire up somewhere in Saskatchewan or Manitoba- there is nowhere near the transmission line resources or grid interdependency to make that true. Installing grid-tied PV in Saskatchewan causes a real fossil burner in Saskatchewan to throttle down though, and that's likely to continue to be the case for decades, until/unless the Canadian midwest invests as massively in wind power as is happening in the US upper midwest. The resource is there, it's a matter of political will, utility regulatory reform, and financing. New midwestern wind is cheaper than new coal on a lifecycle basis, but with renewables 99.9% of the cost is up-front- it takes some adjustments to the business models (or government mandates) to unlock that lower cost energy, but it can happen, the current fossil-friendly leadership in Ottawa notwithstanding.

    The amount of storage required to make the whole grid stable with 100% wind & renewables is a tiny fraction of the storage required for off-grid at the same energy use levels. This has been simulated rigorously for the PJM controlled grid region of the US, which is an electricity market bigger than all of Canada, over a region larger than Germany, looking at real weather data over the past 50 years. The amount of over-building of PV and wind to get there completely without storage, stabilizing the grid with output curtailment and a modest amount of demand response on the load end is also not egregious. In Xcel Energy's region from Colorado to Minnesota they have been able to idle fast ramping peakers during days with any significant wind, since the cost of using modulating the wind arrays (reducing their output below their maximum when necessary) is cheaper than the cost of keeping the spinning reserves going, and the wind has much faster ramp rates (both up and down) than gas peakers to boot.

    In light of the rapid evolution of grid resources, how is it even possible to predict the amount of carbon emissions being offset by super-insulation over the lifecycle of a house? By comparison, it's a lot easier predict the amount being offset by grid-tied PV due to the much shorter lifecycle. But as with insulation it's grid-geography dependent, near-zero in places like British Columbia or parts of Quebec, and very high in parts of the midwest.

    When going off grid there is a very different calculus of storage vs. PV, if one intends PV to be the primary energy source, including heat. The amount of storage for off-grid PV per heating BTU delivered is very high, which is why most off-grid homes in the US and Canada use wood as a primary heating fuel, independent of insulation levels. With a grid you have access to other green resources, some dispatchable (hydro, grid storage), others variable (wind, PV), but with a more diverse mix the total storage requirement to support the single-house load is at least an order of magnitude smaller than in the off-grid case. From a total capital expense point of view massive grid defection would be ridiculously expensive, and far from green, given the amount of ore that would have to be mined & refined for that much larger total amount of battery.

  34. G. W. North | | #34

    It's in the CO2 stupid
    Not you Martin (I am a fan)

    Aww yes if going green was as simple as following the “net zero” propaganda. I consider the whole premise of “net zero energy” fraudulent. It might be true that watts generated and watts used in a year balance out. Dollar wise the numbers work out (read subsidized) but “net zero” sounds like but does not speak to what I am truly after - NET NO CO2. It is a fraudulent name because it makes us think that we are not producing CO2.

    In these times to design a house properly (to heat water and house) one must examine the energy infrastructure available and consider if it’s suitable to connect to (or change design). I have determined it is not -so I insulate and go thermal.

    In Canada we are doing well, we are only 80% dirty energy (overall). Why would I want to put clean energy into a dirty grid? How many people who claim “net zero” energy think that when the lights are on at night or the heater is on in the winter that they are not pouring CO2 into our air? Too many!

    The accountants at “net zero” don’t seem to know that once CO2 is generated – YOU CAN’T TAKE IT BACK. Their next line is: oh but we can make up for it (no you can’t). In the end CO2 is CO2.

    I would love to come up with “net zero” the board game. Problem is I would have to give everyone the game at below cost and continue to supply fun money into eternity!

    Academics and government will continue support fossil fuels. They will continue to support net zero – why? It keeps the grid strong and keeps us fossil fueled. The mere mention of insulation and they scream BUT DON’T PUT TOO MUCH you are wasting your money! It is not about money - insulate until you do not produce CO2 (or not much).

    There is so much to say about how un workable and damaging the concept of “net zero” is. I hope that more of us continue to strive for ways to live that do not produce CO2. CO2 is the reason that solar thermal will continue to be really really alive (you can store a winters worth of heat at home) and that lots of insulation will continue to keep the heat in (duh). Instead of buying a gazeebo (the pay back is terrible) I am going save my pennies and buy some batteries. Bye bye grid see ya.

  35. G. W. North | | #35

    How much CO2 does a "Net Not Zero" house produce?
    The perceived flaws, getting through the “dark cloudy months”

    With occasional use of a generator (like you do). Except if decent appliances were made by manufacturers who are concerned (who have “eco imagination”) and do not offer a cheap version (3 inches more insulation would not be expensive) it would be much easier. There are many many ways to make December easier to live with RE. Biodiesel or biomass generator perhaps. There are also behavioral adjustments. Many people are busier in the summer (myself included) we drive more etc. The opposite in winter.

    No need to waste the extra power in the summer -use it:
    To pump heat into the ground, make cold to use later, to do things that would give energy in December (or not cause it's use). And of course air conditioning.

    In Canada our citizens are not aware of a master plan to combat CO2. What is happening toward that end is certainly not embraced. I for one am not confident that, if we continue as we are, that we will survive without a major ecological breakdown.

    Part of a good strategy would recognize that there are heavy emitters with energy intensive industries that are essential (steel production, jet airplanes etc) to which we should tackle later or who should get to use our hydro resource (keep the grid for them). Perhaps their work can be adjusted seasonally.

    It is hard to turn down nuclear facilities at night. Is there a “thermal corridor” around nuclear plants that can plug into this wasted heat to melt plastic for example? I doubt it.

    Are we fully aware how the “net not zero” strategy fails us?? How much CO2 does get generated in spite of the name! Some researchers on that one (who have not drank the kool aid) would go a long way.

    There are some very good strategies for off grid out there to which I am not aware. Ones that are more honest and much more effective.

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