Image Credit: Image #1: Wikimedia
More Musings of an Energy Nerd
In most climate zones, achieving the Passivhaus standard requires more expensive windows, higher insulation levels, and greater attention to air-sealing details than less stringent construction practices. It should come as no surprise that homes with these features cost more to build than homes complying with easier-to-meet standards.
While fans of the Passivhaus approach usually concede these facts, they note that the added costs yield many benefits, including lower energy costs, better indoor air quality, and improved occupant comfort — and that these benefits justify the higher construction costs.
A research study in Austria looked into this issue, and came to a surprising conclusion: occupants of non-Passivhaus apartments were just as comfortable as occupants of Passivhaus apartments. Moreover, when researchers compared the energy needed for space heating, both types of housing used about the same amount of energy.
A multi-family project in Bregenz
The research was conducted at a multifamily housing development in Bregenz, Austria, called Wohnpark Sandgrubenweg. The city of Bregenz is located in the Vorarlberg region of northwest Austria.
The project consists of 76 apartments in four buildings, each four stories tall. The apartments range in size from 592 square feet to 1,076 square feet. The apartments are owned, not rented, by the occupants.
Construction of the development began in 2005. The developers based the buildings’ design on green principles. For example, the underground parking garage includes a “bicycle service station” designed for do-it-yourself repair jobs. The garage also includes a “car-sharing stand.” (Further details on the car-sharing facility are not available.)
Space heating and domestic hot water are provided by a central boiler fueled by wood pellets. A hydronic distribution system circulates hot water through in-floor tubing. Apartment owners pay for electricity and space heating based on meters that measure energy use in each apartment.
Some of the…
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36 Comments
Martin
My takeaway is that the ideal Passivehouse is one with no occupants.
Response to Malcolm Taylor
Malcolm,
Actually, all homes perform better with no occupants -- not just Passivhaus homes.
Heat transfer between neighbors
I used to live in an apartment where only my two shortest walls were exterior walls. My strategy to lower my electric bill was to set my thermostat lower than my neighbors so that heat from their apartments would conduct into mine. I wonder if that is part of what is going on here--the PH apartments with higher thermostat set points are helping warm their neighbors, and so the energy use reported for them includes helping heat the neighbors. I wasn't able to figure out from the paper whether that would be significant--depends on whether the different apartment types were interspersed, area of the adjoining walls, and insulation of the adjoining walls. (I don't read German.)
It is true that, with a good envelope, the energy penalty for raising your thermostat setting is less. So the PH occupants may have understood that and felt free to set it where they were most comfortable, rather than at a compromise between comfort and cost or environmental guilt. The survey didn't measure a comfort difference, but it didn't prove that there wasn't one. So it may be that what the PH occupants bought was the freedom to set their thermostats where the like, guilt free.
But there is more to be figured out than just the thermostat setting. I hope they plan more monitoring, including the ventilation settings.
Response to Charlie Sullivan
Charlie,
To the best of my knowledge, all of the Passivhaus apartments are in one building, while the apartments in the other 3 buildings meet the less-stringent Eco 2 standard.
So the people in the Passivhaus apartments have Passivhaus neighbors.
Good Job They Discovered This
There were quite a few jurisdictions that were close to adopting PH standards as law. What a waste of money and added headaches for builders that would have been.
And by the way, IECC 2015 is an excellent place for us North Americans to STOP while we sort out what works well, what doesn't, wait for the PV cost curve to flatten, and evaluate current innovation.
California is going Net Zero by 2020
By 2020 all new home construction will have to be net zero energy, which will be a good testing ground for what does/doesn't work, and what's cost effective relative to PV solar.
While some north of the 49th might think that's a cake-walk due to the climate, it might be in some areas, but the populated higher elevation parts of northern California have areas with comparable heating degree days and heating outside design temperatures as those other Canadians living south of the 49th. We'll definitely see what works/doesn't by 2025 (though we kinda know already.)
PV solar in the US is averaging $3.33/watt and falling by 10% or more every year. With CA requiring Net Zero the volumes will pick up, and the costs fall even faster. https://openpv.nrel.gov/
Martin
I wasn't just being facetious. There is a strain in architecture and I'm beginning to think among some high performance builders, that sees the house as an object or machine, Its occupants are sometimes viewed as potential impediments to it achieving it's peak performance - or in architecture's case it's sculptural purity.
Kevin
The various accreditation schemes seem to compete to see which is the most annoying. I was laying down synthetic roof underlayment today and noticed the label that you could get Leed points for using it. Dear Lord - why?
I'm trying not to snicker
But failing.
Response to Kevin Dickson
Kevin,
I think I agree with your assessment that "IECC 2015 is an excellent place for us North Americans to STOP while we sort out what works well, what doesn't, wait for the PV cost curve to flatten, and evaluate current innovation."
Twenty years ago, U.S. building codes (mostly) ignored air leakage, and the energy performance of almost every new home in the country was a disaster.
Since then, what's happened? Codes have become more stringent. Codes now address air leakage. The cost of PV has plunged. LED lamps have gotten cheap. Better ductless minisplits have been developed that work well in cold climates. On the horizon, less expensive batteries may address the need to flatten out the spikes and troughs of PV production.
These developments all undermine the Passivhaus approach. There isn't much evidence that our building codes need to require compliance with the Passivhaus standard. What we really need is code enforcement, not stricter codes.
Response to Malcolm Taylor (Comment #7)
Malcolm,
I wasn't being facetious either. From an engineer's perspective, occupants are the irritating creatures who ruin a perfectly good house by moving in.
Beyond Net Zero
In "easy climates" with net metering, there is enough roof area to generate positive cash flow. The rating system at that point should be quite simple: Net dollars per year earned.
Response to Kevin Dickson
Kevin,
You wrote, "In 'easy climates' with net metering, there is enough roof area to generate positive cash flow."
In fact, the area of the roof has very little to do with whether a PV system generates positive cash flow. Assuming that the local utility offers a reasonable net-metering contract, the size of the PV array (within a reasonable range) has nothing to do with whether the investment makes sense (or whether the investment yields enough cash flow to satisfy the investor).
If a PV array rated at 8 kW is a good investment from a cash flow perspective, it's very likely that a PV array rated at 2 kW or 4 kW would also be a good investment from a cash flow perspective.
Smaller PV arrays generate less energy, of course, but they also cost less to install.
Very Good House vs Passivhaus
Martin,
I think it is worth noting that the non-passivhaus apartments built to the eco 2 standard look much more like a Passivhaus than typical North American construction. I'd call it "very good house". R-40 Walls, R-6 Windows, R-50 Roof, and R-34 underslab is quite impressive, especially considering this project development started a decade ago. These performance levels are at or near Passivhaus levels for most multi-family projects in North America. For climate comparison Bregenz has 6,282 heating degree days per year, which is roughly equivalent to Denver, CO.
Kevin,
I'm not sure what hole you have been hiding out in, but for decades superinsulation and heat recovery ventilation has proven to work. The IECC 2015 is a low bar and stopping there will ensure that we continue to lag far behind the minimum building standards in European countries like Germany and Austria.
Response to Skylar Swinford
Skylar,
While the Eco 2 standard is a low energy standard, the Passivhaus standard is more stringent. The question the researchers looked at is whether it is worth the higher cost of construction to meet the more stringent standard in a location with 6,282 heating degrees per year. The researchers concluded that it is not worth the higher construction cost.
Your jab at Kevin -- "I'm not sure what hole you have been hiding in" -- is inappropriate, and is the kind of put-down sometimes used by those who are trying to avoid examining data or discussing a technical issue.
I don't think that Kevin claimed that superinsulation doesn't work (whatever that means). Nor did he claim that heat recovery ventilation doesn't work (whatever that means). Bringing up these two issues is a red herring.
Whether or not the IECC 2015 is a low bar depends on one's goal. There may be a valid technical argument to support the idea of higher minimum R-values than those required by IECC 2015; but if this technical argument exists, you have failed to make it.
And by the way, just because superinsulation works -- in other words, just because very thick insulation slows down heat transfer -- doesn't mean that we can't discuss optimum R-values. Moreover, just because HRVs work -- in other words, just because an HRV can introduce exterior air and exhaust stale air -- doesn't mean that all single-family homes in all climates should be required to install an HRV. So the aim of your barbed comment -- "superinsulation and heat recovery ventilation has proven to work" -- is entirely unclear.
feels like cherry picking
Martin,
You make a statement at the end: "Like Dr. Kempter, researchers in the U.S. have noted that occupants of Passivhaus buildings often use more energy than PHPP software predicts."
Is there statistical data to back up this critical claim? One project here, one project there - makes for good one-off stories, but doesn't indicate an actual trend. For every project that has more energy use there is another with less energy use and many that match-up quite well. As the saying goes: the average is important. One thing we can all agree on, I hope, is that we need a lot more data.
PS - Can you provide a translation of the actual report?
Response to Ken Levenson
Ken,
There is widespread agreement that the PHPP defaults for miscellaneous electrical loads and domestic hot water use are unrealistically low for North American households.
My sources include Marc Rosenbaum, who is quoted in this article: It’s Not About Space Heating. In that article, I wrote, "Rosenbaum questioned the usefulness of the PHPP default assumptions for plug loads and domestic hot water (both of which are unrealistically low). He said, ‘PHPP assumes 6.6 gallons [25 liters] of hot water a day per person, but that’s not enough for normal Americans.’ Of course, missing the target sometimes has side benefits. Rosenbaum said, ‘If people are using three times as much electricity for plug loads as the default value set by PHPP, that helps you hit your heating number.’ ”
The PHIUS technical committee responsible for the new PHIUS standard had to tackle these unrealistic default assumptions. Their report, "Climate-Specific Passive Building Standards," notes: "RESNET defaults for energy use by “televisions and miscellaneous electric loads” are substantially higher than the current equivalent baseline defaults for “consumer electronics and small appliances” in WUFI Passive (the same goes for lighting). The formulas work a bit differently – the baseline formulas are strictly per person, whereas RESNET uses a combination of per-person and per-square foot terms (conditioned floor area, exterior dimensions). While occupants arguably “should be” using a lot less miscellaneous electricity, keeping low defaults is not an effective way of driving occupant behavior because the occupants are not being certified and there are no consequences to them. Rather, the standards influence the designer and unrealistically low defaults actually create a false incentive – they give too much latitude."
The same report notes that the PHPP default assumptions for domestic hot water use are unrealistic. The authors recommend changing the default assumptions; software should assume that occupants "Use hot water as per Building America assumptions (~50% higher than PHPP)."
I love data. If anyone has good data showing that American occupants of Passivhaus buildings are complying with PHPP assumptions for miscellaneous electrical loads and domestic hot water, I would love to see the data. (Ideally, N>1.)
The paper discussed here is only available in German. If any bilingual readers want to translate the document, I'd be happy to post a link.
Forrest Missing
This is an interesting article commissioned by Mr Rohmberg - the owner of a very large construction company in Austria where there has been some (normal) push-back on adoption of Passive House/Passivhaus: http://derstandard.at/2000002397526/Man-kann-nicht-Huellen-mit-Loechern-liefern. Despite some sectors wanting to maintain the low-energy status quo, massive Passive House developments are being built across Austria, Germany and now all of Brussels: http://www.southzeb.eu/portfolio/passive-house-residential-buildings-lodenareal-innsbruck/ and http://heidelberg-bahnstadt.de/en/sustainable-living.
As Ken commented, this study has a relatively small sample size, so it's best to take a look at a number of other studies that have amassed larger data sets in order to reach a more statistically accurate and informed conclusion: http://passipedia.org/operation/operation_and_experience/measurement_results/energy_use_measurement_results. The fact that user behavior will vary across population groups is not new, and buildings can and should be designed to accommodate this.
Thanks for sharing this study, Martin. Your keen eye for spotting anything negative about Passive House is broadly recognized and appreciated. The data on Co2 levels of the units occupied by smokers and non-smokers was particularly interesting. The elements of 'comfort' and 'indoor air quality' that cannot be sensibly measured by occupants is always revealing. From the data curves on Pg.27 & 28 it looks like the Passive House apartments are better able to deal with contaminants brought into the homes, which is in this case is from smoking occupants. The children of these smokers must be grateful.
I'm always amazed by the volume of performance data that is available on Passive House projects, while very little is provided by advocates of alternate standards or 'rules of thumb.' Are there any studies on performance and cost data being conducted for 'Pretty Good Houses?'
Response to Bronwyn Barry
"Are there any studies on performance and cost data being conducted for 'Pretty Good Houses?' "
The nearly-net-zero houses monitored & tested by Fraunhofer Center for Sustainable Energy Systems in this small study were all fairly close to "Pretty Good House" levels:
http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/comfort_iaq_low_energy.pdf
As were the mostly Net-Zero houses in this study:
http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/monitoring-mini-split-ductless-heatpumps.pdf
Since there is no hard& fast requirement to PGH with no governing body certify compliance to the non-existent firm standard there isn't likely to be an directly analogous study of PGH houses, the way there can be with PassiveHouse. But using the loose R5/10/20/40/60 rules of thumb definition many US climate zones 4 & 5 homes could be Net Zero Energy with PV arrays that fit comfortably on the roof, if some forethought is given to roof orientation & pitch. In warmer climate zones it wouldn't even take PGH to get there.
The cost of PV in the US has fallen by half in the past handful of years, and will likely fall in half again by 2020. (The current installed cost of PV in German and Australia are already only 60% of the cost in the US, using the same panels & inverters.) With CA committed to Net Zero on all new houses beginning in 2020 the US PV market will soar, and the prices will fall faster. When looking at the cash economics or lifecycle environmental impact of that last R24 of the R34 under-slab foam in the Eco-2 building vs. only R10 under the slab with sufficient rooftop PV to make up the energy difference for 100 years (even fixing the cost of PV at current prices, though they will surely fall by the time replacement maybe warranted in 25 years), I doubt very much that it favors the additional 6" of EPS. If the amount of PV necessary to cover the annual energy use of the house fits on the building, it's not clear how taking it all the way to PassiveHouse is going to be financially rational when PV hit's a buck a watt for installed cost. It sort of depends on how the business models of the electric utilities evolve, but at current German retail electricity rates distributed storage and their current ~$2/watt PV is fully financially rational, with grid defection as a financially rational possibility (though NOT a desirable outcome.)
The carbon emissions reduction argument for PassivHaus needs updating to match grid-reality on an increasingly frequent basis, and the accounting for site sourced energy needs to be able to reflect the value to the grid as well as the local user a bit better too. For the the carbon argument to remain valid it needs to be real carbon emissions avoidance, not theoretical or fictitious avoidance, and grids everywhere are evolving fast, now that both wind & solar are cheaper than fossil fuel incumbents in many markets (even the highest efficiency super-critical coal plant that was recently completed in Hamburg.) Like many utility companies, the PassivHaus approach seems to be getting caught flat-footed in the face of exponential growth & rapidly falling costs of distributed renewables, and now the rapidly falling price of grid-storage (on both sides of the meter.)
In 15 years PV will be approaching 2x the efficiency of circa 2010 commodity panels, taking even less space, and probably 1/4 the cost or less, which means it will take even less stringent building performance to hit Net Zero, and the financial rationality crossover point will be even lower, and the grid much lower-carb. The argument at that point (and even now) needs to be around lifecycle resource impacts, comfort/health, and sustainability, less on carbon avoidance & raw energy use limits. Adding another 5-6" of EPS under the slab (beyond the PGH rule of thumb) doesn't seem like the right thing to do even now in most locations.
Passive House (the real deal) and the All Renewable Grid
Dana - you'll be happy to learn that the Passive House Institute has also seen the writing on the wall as far as the all-renewable grid, which is fast becoming a reality both here and in Germany. A new assessment for both carbon emissions and primary energy calculations, weighted by source and storage capacity, were formally released in an updated PHPP this year. (The English PHPP v.9 will be out soon.) Here's a link to explain a few more details, including project examples: http://passipedia.org/certification/passive_house_categories/classic-plus-premium?s%5B%5D=renewables
There's a class being held on this in New York this week: http://nypassivehouse.org/events/advanced-passive-house-consultant-training-phpp-9-primary-energy-renewable-new-certification-levels-and-more/.
Oh, and another thing...
I forgot to mention there are pilot projects around the US that are testing this new Primary Energy Renewables (PER) calculation, using updated regionally specific grid source mixes. A presentation that explains this application for North America will be given by Jessica Grove-Smith at the NYPH Conference on Thursday: http://www.rightevents.net/NY15PH_Conference_Expo/
Response to Bronwyn Barry (Comment #18)
Bronwyn,
You wrote, "This is an interesting article commissioned by Mr. Rohmberg." Perhaps you meant to write that the "research study" was commissioned by Mr. Rohmberg? As the author of the article, I can assure you that the article was not commissioned by Mr. Rohmberg.
You are correct that a large number of Passivhaus buildings have been completed in Germany and Austria. You are also correct to note that one reaction to these projects is push-back from builders.
The energy use findings at the 40 studied apartments at the Wohnpark Sandgrubenweg projects were surprising and unusual, which is one reason why I reported on the study (as you correctly guessed).
Concerning your request for energy use data on "pretty good houses," I think that Dana Dorsett did a good job of answering.
Response to Bronwyn Barry (Comments #20 and #21)
Bronwyn,
You are correct that the Passivhaus Institut has established new certification criteria for Passivhaus builders who install rooftop PV systems. GBA has published several articles on these new labels; see, for example, this report by Scott Gibson: Passivhaus Institut Rewrites Certification Standards.
While the establishment of two new certification programs -- for "Plus" buildings and "Premium" buildings -- is interesting, I don't think that these new labels address the challenge that Dana Dorsett refers to. When electricity has a tiny carbon footprint, and when electricity drops in price, the entire premise supporting the idea of massively insulated building envelopes starts to crumble. The Passivhaus Institut has not yet addressed this challenge, because the requirements for the "Plus" and "Premium" building labels requires builders to comply with the same Passivhaus envelope standards that have been around for 20 years.
As Dana noted, this isn't just a question of cost-effectiveness. (If it were, Passivhaus builders could argue, "I know that these very high insulation levels aren't cost-effective, but I still want the thick insulation because it will help save the planet.") Thick sub-slab foam is undesirable from an embodied energy perspective. What this means is that these very thick layers of sub-slab foam are actually contributing to global climate change, because manufacturing the foam requires more energy than the insulation will ever save.
More forrest missing...
Martin,
The Rhomberg-commissioned study you've written about and Dana's shared link (http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/comfort_iaq_low_energy.pdf) point to a couple of great reasons why your relentless focus on first costs is misguided. Yes, we could build cheaper and with less insulation and slap PV on to 'zero' out the energy use, but the point of Passive House (which I've taken great pains to attempt to explain here: http://nypassivehouse.org/phius-bsc-climate-specific-proposal-unsupported-by-data-and-incomplete/) is not JUST energy, not JUST cost, not JUST comfort, but also HEALTH. All of them need to be looked at together, rather than in the splendid isolation you appear to be fixated upon.
It's now fairly universally agreed that once you cross a certain threshold of insulation and airtightness, then mechanical ventilation is required. I think we can all also agree that levels of insulation depend largely on climate, but dew-point, mean radiant surface temperature and moisture control all need to be factored in to determine what that thickness is since that addresses condensation risk. Air-tightness is simply a function of smart design, but also has an impact on ventilation effectiveness and moisture control. Now that the initial hysteria surrounding the Passive House 0.6 ach number has died down, it appears to be accepted as a reasonable number.
From the DOE study of the Stow and Townsend projects listed by Dana above as good examples of 'Pretty Good House' the energy and basic sensible comfort issues appear to be mostly taken care of, but I found the IAQ and ventilation issues uncovered by this study disturbing. Here are a few quotes:
"The occupants switched off the ventilation because of acoustic noise and to reduce electricity consumption." (Pg.30)
"The CO2 concentration was unexpectedly high, especially in the master bedroom. A likely explanation for these values was found in the ventilation unit: the flap for the frost protection was in the wrong position. This flap was built in to prevent icing in the heat exchanger, by closing the fresh air inlet and opening a bypass. Instead of being exchanged with fresh air, exhaust air was recirculated (see Figure 51). The issue was fixed in October 2010." (Pg. 28 & 29)
"The indoor formaldehyde concentrations in both homes exceeded the chronic and 8 h reference exposure levels, which were set at a stringent limit of 9 µg/m-3 by the Office of Environmental Health Hazard Assessments (2008)."
In the Rohmberg study, I pointed to similar health-related measurements that were glossed over in both that study and your own report on it: particulate concentration in the indoor air carried in by smokers, which the Passive House apartments were able to control.
There is clearly much more work to be done in the field of ventilation and IAQ. Incidentally, I’m not sure Passive House has this issue totally buttoned up either, but it does appear to address them more reliably with a 25 year history that we can benefit from. I think we can all agree that IAQ cannot be ignored in high performance buildings, whether you call them ‘Pretty Good,’ Passive House, or passive buildings. That may cost us a little more for a unit that is properly designed, sized, tested, installed and commissioned. Our building envelope may also require a small amount of extra insulation and better windows to eliminate interior condensation risk and surface temperature asymmetry to eliminate drafts that conflict with ventilation distribution design.
You may be relieved to hear that I don’t think Passive House is perfect, but it does provide a solid target framework and a reliable tool with which to design, specify and build. Those features are currently lacking in other checklist certifications and ‘rule of thumb’ guides. My point is that energy, comfort, health and IAQ all need to be looked at together for us to honestly be delivering buildings suitable for human occupation. This is not just about cost or energy or carbon footprint, but those are great additional benefits. I’d wager that every customer who reads one of these reports, or learns more about the effects of IAQ on health will be willing to pay extra for that. After all, is health not our most valuable asset?
Response to Bronwyn Barry
Bronwyn,
If a researcher could come up with housing specifications that predictably improve the health of the occupants, that would certainly be wonderful. I have not yet seen any research findings showing that families who live in green homes or Passivhaus homes have better health outcomes than families who live in code-minimum homes.
Until such a link is discovered, builders or designers who make health claims for their homes are skating on very thin ice. If you tell your clients that you are able to build a home that will help their family's health, you might want to sit down with a lawyer or your insurance broker to see if there is any basis for your claim, and to see whether your claim raises liability concerns.
For more information on this topic, see Ventilation Rates and Human Health.
While Passivhaus builders love to talk about mean radiant temperature, the discussion in cold climates boils down to glazing specs. If you choose decent windows, you've got this problem nailed. You don't have to comply with the Passivhaus standard to solve the mean radiant temperature problem.
That said, I always enjoy wrapping up my discussions with you, Bronwyn, by listing points of agreement. Like you, I believe that homes that are built with attention to airtightness need a good ventilation system. Like you, I believe that people who smoke tobacco indoors are endangering their health and the health of non-smokers who live with them. Like you, I believe that poorly designed and poorly installed ventilation systems are unlikely to be used and are the bane of the construction industry. That's why (like you) I believe in educating builders in good ventilation system design.
See, Bronwyn -- we can agree on a lot.
Agreed
Martin, we do agree on many things. I believe I've mentioned that I value your critical eye, especially with regards to Passive House. It's allowed me to continuously sharpen my pencil and re-assess what I'm doing as a designer and advocate. Thanks for your willingness to take a critical position and provide a forum where other perspectives can be seen and heard. I LOVE the banter and the push-back. There's nothing worse than a floppy dance partner! :)
Response to Bronwyn Barry
Bronwyn,
Thanks for wrapping up our discussion on such a generous and gracious note. Keep up the dialogue -- it's good for all of us.
Knock it off
I only come here for the fights with PH advocates.
Response to Dan Kolbert
Dan,
Let me guess -- you're a hockey fan, right?
Yes, but
I find the Building Science fights to be much more exciting.
Regarding California's Net-Zero by 2020 rules...
The CPUC & CEC have launched an action plan website to ease that learning curve, with design resources, case studies, etc:
http://www.californiaznehomes.com/
http://www.greentechmedia.com/articles/read/California-Wants-All-New-Homes-to-be-Net-Zero-in-2020
The population of California is about half that of Germany, and with about the same ~9 metric tons per capita it also about half the total carbon emissions, but it also has a much larger new residential home market. Germany builds about 270,000 homes & apartments per year, to California's ~185,000. Even if all the homes being built in Germany in 2020 were PassivHaus certifiable or Eco2-ish (which I don't believe is required), the net carbon impact of California's Net Zero Energy requirement will be higher.
Mind you, the cost of small scale rooftop PV solar in Germany is currently about half what it is in CA, and though the output per rated watt in Germany is considerably less than in California, it's still well over half. Germany's grid in 2015 is a bit dirtier than California's at about 0.5kg/kwh about to about 0.4 kg/kwh but both are making gains on that. When all new houses being built in CA are Net Zero CA's grid carbon emissions per kwh will drop, as will the per-capita electricity use.
Should Germany require Net Zero Energy for new construction? The envelope improvements required to get there with Germany's cooler average climate and weaker sun are higher than in California, but it's still probably cheaper than going PassivHaus, as demonstrated by the Net Zero row-house retrofitting programs next door in the Netherlands, which are cost-effective on energy savings alone: http://blog.rmi.org/blog_2015_04_16_taking_dutch_housing_from_energy_hog_to_net_zero
Dana's needs his own column - and back to the 'Hockey'
Dana - I think GBA should give you your own column. Your posts on PV and the grid are always highly informative. However, comparing cost of PV in California and Germany takes the same myopic perspective I've accused Martin of having. Cheap PV does not address the fact that we're building buildings that are not fit for healthy human occupancy.
Let's make Dan Kolbert happy here and re-focus the conversation back to Martin's original post, in which he postulates that the 'Cost of Passivhaus (or Passive House) is Sometimes Hard to Justify.'
I think I've made a 'pretty good' case for why a small cost increase for better insulation, windows and a better H/ERV (properly commissioned) may well be worth it. I've also tried to show why all of those things are connected - a great HRV with poor assemblies and leaky windows that have interior condensation won't cut it. Based on the IAQ data collected in the Rhomberg study, and in the 'Pretty Good House' example studies conducted by the DOE, all the non-Passive House projects in those studies fell short on IAQ. (For the record, I'm not sure there's enough data on whether Passive House projects deliver consistently on IAQ either.)
The better question here would be: Is occupant health and IAQ worth paying for, and how can we consistently deliver better IAQ? I think we'd all agree that we need less hot air blowing on this topic and more real data. Anyone know of any studies being conducted with this goal in mind?
+1 on the better ventilation front!
... not so much on the relative value of an "extra" 6 inches of sub-slab insulation.
Comfortable is comfortable, and low-carb energy is low carb. If you can get to Net Zero (or Net +) without taking it to PassivHaus levels, the argument for PassivHaus then needs to be around overall sustainable building practices & occupant health. PassivHaus indoor humidity levels are often pretty high, and while humidity by itself isn't a very good measure of overall air quality, in cold climates that's an indication of low ventilation rates. http://www.passivhaustagung.de/Passive_House_E/ventilation_and_humidity.htm
With an HRV of sufficient capacity the occupants basically set their own indoor air quality at a fairly modest hit in energy efficiency, far less of an energy hit than with exhaust-only ventilation schemes. Many are comfortable living in a smoke-filled radon-laden room "freshened" with aerosol spray VOCs, even if from a public health point of view that's a disaster. More than a building design issue, it's a public education issue.
IRC 2012 chapter 15 spells out general ventilation requirements ( http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_15_sec007.htm ) but it's not clear whether anything other than the bath & kitchen exhaust ventilation portion of the code gets tested and enforced with any regularity. Lstiburek at Building Science Corp and others rail against requiring ASHRAE 62.2 ventilation levels for the energy & wintertime comfort/health hits, but those levels might still be appropriate for the stogie-smokers & hair-spray addicts. Building with lower-VOC materials of lower toxicity would help, but that's not the primary source of indoor pollution in most homes.
Response to Bronwyn Barry
Bronwyn,
This week you are apparently focusing on IAQ and ventilation systems. I'm happy to address your concerns.
1. Saying that you are concerned about IAQ and ventilation systems does not absolve you from addressing Dana's points. Calling pretty good houses "not fit for healthy human occupancy" is glib and beside the point. It's a way of sidestepping the technical issues that Dana has raised.
2. Let's talk about IAQ and ventilation systems. First of all, your assumption that occupant health is correlated with ventilation rates is unsupported by the evidence. Once again, I'll refer you to my article on the topic: Ventilation Rates and Human Health.
3. Finally, if you desire a high ventilation rate, in spite of the fact that there is no scientific evidence linking high ventilation rates with occupant health, you are free to ventilate your home with 150 cfm, or 300 cfm, or 3,000 cfm of outdoor air. Nothing is stopping you. But let's not confuse the issue of high ventilation rates and the Passivhaus standard. If you want a house with a 150 cfm ventilation system, it's easy to meet your needs without complying with the Passivhaus standard. Any "pretty good house" builder who reads GBA can build you a house with a 150 cfm ventilation system -- and you don't have to use PHPP software to build it.
Short-lived 'Kumbaya' moment...
Aw shucks, Martin. And I thought we were getting along so nicely there for a moment....?
What part of "we're building buildings that are not fit for healthy human occupancy" didn't you read? (The "we're" part includes me and I don't have the answers.) I can't find a place where I connected IAQ and ventilation rates or advocated for more blowing either, so am confused by your response.
I am focusing on IAQ though. (One out of your four stabs at what I said isn't bad! :)- I think we all should be if we're building tight buildings. Toxic IAQ may be our industry's next big 'asbestos' or 'lead paint' or 'toxic Chinese drywall' - not like our industry has no record of doing dumb stuff to save money, does it?
Kumbaya is possible
Bronwyn,
No one is going to argue with the idea of making sure that our indoor air is not toxic. If you think there is evidence that we are building homes with "toxic IAQ," that's an interesting perspective. Most "pretty good houses" and Passivhaus buildings have excellent IAQ, so I see no evidence of a problem with toxins or health problems in these houses.
Future data may prove me wrong, but that's the way I see it. In the meantime, I agree: good indoor air quality is an admirable goal.
Needless to say, the European apartments with people who smoke tobacco indoors represent a special problem. They're nuts, and they should stop smoking or smoke outdoors.
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