in pursuit of energy efficient minimalism
We briefly touched on EnerPHit (Energy Retrofit with Passivhaus Components) a while back, and both EnerPHit and PH retrofits have come up in a number of recent posts, emails and discussions (e.g. the NZE v PH post, which made its way onto GBA and treehugger). PH retrofits were even briefly mentioned in Alex Steffen’s new book, Carbon Zero. After a series of recent twitter-logues (?) with preservationists and others, I’m finally getting around to collating my thoughts on those conversations. Not only is it imperative to reduce the energy consumption (and resulting CO2 emissions) of new buildings – but we’re long overdue for a strong and innovative focus on DERs – especially since the existing building stock is replaced at less than 3% per year. Luckily, there isn’t a need to reinvent the wheel – the Germans already perfected it.
With new PH construction, a 90% reduction in space heating can be achieved, but a 90% reduction in primary energy (sans the voodoo math of renewables) over present energy codes is rare. It could be feasible with a few typologies, though (e.g. clinics/dorms) but it’s not an easy feat (see our 2030 PH post). For most newly built PHs, the energy savings potential is in the 60-80% range. Here in the mild PacNW, where our energy codes are fairly progressive, residential energy savings can still be quite high (e.g. the Salem PH was a 66% reduction over baseline, even with high plug loads). Institutional projects have potential for even greater savings, with the bonus of significant mechanical equipment lifecycle savings (and comfort, IAQ, etc.)
There were mainly two concerns from those dialogues regarding PH retrofits, and we view both as being fairly benign. First, where does the insulation get installed in a retrofit? For many projects, the insulation is best applied on the exterior – generally this isn’t a major issue because existing projects tend to be masonry or concrete, and adding rigid foam insulation with a rendered finish tends to keep the design relatively unchanged. It also reduces thermal bridging. From a preservationist standpoint, I don’t really see an issue with that. There are instances where exterior insulation isn’t possible (say, a listed brick facade needs to be maintained, or no space for exterior insulation) – which means the insulation ends up on the interior. There are a number of PH retrofits that have dealt with that exact situation – and they look great, lowered space heating costs by a factor of 10, saved tons of CO2 per year, and increased the buildings lifespan. Definitely more challenging – but also should be thought of as quadruple bottom-line thinking!!!
The second sticking point seems to be the use of ‘a lot‘ of EPS or other rigid foam. We completely understand the hesitancy towards incorporating petrol-based materials – preferring to use as little as possible on our own projects (see our natural PH post). It’s also worth noting embodied energy and resulting CO2 emissions from the insulation are recouped very quickly, and in some instances nearly immediately (e.g. cellulose, cork). But even with EPS, it’s a short payback on the embodied carbon. Don’t believe me? To the back o’ the napkin!
The embodied carbon of 10″ EPS retrofitted on the facade of a hypothetical 30′x10′x30′ tall building (TFA = 750 m²) would be under 7,500 kg CO2 (8.3 tons). If the retrofit caused the heating demand to drop from 50 kWh/m²a to 15 kWh/m²a (in order to meet PH) the project would save (annually, in heating costs alone) 35kWh/m²a x 750 m² =26,250 kWh/a. Per GEMIS 3.0, electricity drawn from the grid releases 0.68 kgCO2/kWh, therefore the annual emissions saved would be 17,850 kg CO2 (20 tons). Thus, the embodied carbon of the insulation would be recouped in under half a year. This is why the embodied carbon/energy argument is moot until a building is actually uber efficient, a la Passivhaus/Minergie/etc. Focus on how the building performs, then address other ‘green’ measures.
I believe it is also worth discussing these projects in light of the Preservation Green Lab reports released in the last year. While there are merits to them, some of the assumptions in these reports (double pane windows @$100/sf = high performance?!?; comparing existing stock retrofitted to new buildings with a paltry 30% efficiency increase over baseline) are laughable, as in the E.U. factor 10 reductions in retrofits can be achieved for little to no additional cost and triple pane PH windows can be obtained for under $40/sf. Passivhaus construction that’s 70-80% more efficient than baseline (PH) changes the ‘preserve v. demo‘ equation – especially on the embodied energy front. If you want to make the case for preservation, then the case should really be ‘Passivhaus/near-PH + preservation‘. They go hand in hand, this is the ‘greenest o’ the green”, in every sense of the word.
So… On to some (heavily linked) PH retrofits.
As with new detached housing, PH retrofits for existing detached houses are not easy. Though, they can be achieved, especially if a significant rehabilitation is already planned. A plethora have been completed in the EU – and there are a few that have been done in the U.S.
Tim Eian-designed EnerPHit in Minneapolis (first in the US). The owner’s blog can be followed on MinnePHit.
Another one we really like is this rehab of a 1936 Modernist concrete house in Connecticut by Ken Levenson and Greg Duncan. The project utilizes foamglas for wall insulation, and window tape/Sto Gold Coat for the air barrier. (pdf)
Simmonds.Mills’ semi-detached EnerPHit rehab, Grove Cottage (UK), that resulted in a 55% reduction in CO2 emissions and a 58% reduction in energy consumption. More photos and info at retrofit for the future.
A certified PH rehab of an 1899 rowhouse in Park Slope that recently caught our eye – and managed to avoid ridiculous levels of insulation. +1 for buildings huddling together (increased density + thermal efficiency)! More stats on passivhausprojekte.
Multifamily? Piece o’ cake!
This rehabilitation in Berlin by BCO architkten has easily landed in my top 10, some great moves on an urban project. Also, who doesn’t love a grey building in a grey city? Yummm!
This modernization of a typical 1950s building located in Hannover resulted in a stunning 93% reduction in end energy use and 92% reduction in CO2 emissions. A brief write up (in German) can be found on passivhaus-platform (which features a number of PH rehabs that have achieved 60%-90% reductions in energy consumption).
The revitalization of this 1950s apartment block in Frankfurt resulted in an uber-impressive 92% reduction (200 kWh/m²a -> 17,5 kWh/m²a) in energy consumption. Meaning the rehab reduced total site energy by 113,550 kWh/a. When Germany’s energy costs are 31 cents/kWh – this results in annual savings of $35,200/a. Oh, and also avoids the release of 167 tons of CO2/a. Game. Changing. Report can be found here (pdf, German)
The first skyscraper passivhaus retrofit was a post-war tower in the Weingarten district of Freiburg, completed early last year. The 16-story concrete building was brought beyond present energy code requirements to meet PH. In the process, CO2 emissions and consumption were reduced by over 50%. More info here (pdf, German)
PAUAT’s school refurbishment in Schwanenstadt (AT) was one of the first retrofitted to meet PH. This resulted in significant CO2 reduction (76%), reduced lifecycle costs, significant energy savings over the existing conditiongs (77%), increased thermal comfort and air quality… How is this not standard practice?!? Good grief! Frustrating doesn’t even come close. Report here (pdf, German).
PH retrofit of a 1950s Ex-Post building in Bozen (IT), by Michael Tribus. This project takes a former postal facility and modernizes it into a stunning project that will pay for itself in under 7 years. It also shows that incorporation of exterior insulation can add a touch of frivolity to an otherwise banal facade. Report here (pdf)
Probably one of the more intriguing rehabs we’ve seen – the facades of this dormitory were removed, and then prefabricated extensions were added to the remaining structure – increasing thermal performance as well as living space. This culminated in a 60% reduction in primary energy use. Breakdown of the process can be seen here (German).
Bere Architect’s Mayville Community Centre revitalization, presented in Hannover, also achieved a whopping 90% reduction in energy usage over the existing building. Cost upgrade to meet PH from present code required an additional 3-3.5% investment. With incorporation of renewables (18 kWp PV), the price difference was only 8%. More info on this solid case study can be found here (pdf).
Industrial? Check (and mate!)
AS Solar used this modernization of an industrial building as a demonstration for their products. It was presented in Hannover this year and blew the socks off some folks, due to some pretty incredible technical achievements. Yet nother project with a stunningly awesome 90% reduction in heating demand over the original building – with the incorporation of PV and solar DHW, the building actually produces more energy than it consumes. Take that, LBC! Report can be read here (pdf, German)
In 2005, manufacturer Drexel + Weiss rehabilitated a facility built in 1969. In the process, their heating demand dropped by 95% (200 kWh/m²a -> 10 kWh/m²2a) thus saving the expulsion of 165 tons of Co2/a. Oh, and the amortized payback was under a year. Not only smart business sense – but they make phenomenally attractive mechanical units for PHs. Details can be seen here (pdf, German)
This renovation of a listed building in Austria, the Fronius HQ is attempting a Factor 10 reduction in energy use. You can catch a youtube vid here.
A revitalization of an 1950s church in Heinsberg (DE) by Ludwig Rongen will keep the brick facade intact as well. The project primarily incorporates an internal layer of insulation (cellulose, kept off the masonry wall). Of course, this ends up reducing a little bit of interior footage, but keeps the exterior intact and ensures comfort, durability and significant energy savings. Win, win, win – is it not? Rongen’s presentation on this PH retrofit can be viewed here (pdf).
Soooo… Hopefully those satiated your PH retrofit appetite. There are many examples to draw from, across several typologies and eras – I could honestly go on ad nauseum. The strategies and knowledge exist, we don’t need to reinvent the wheel – just balance the one that’s already in front of us. For us, the choice is clear. If craving more info, we’ve thrown several links below. I’d love to keep going on the topic, but I do believe this is BFC’s longest post to date and my wife has been glaring at me to wrap it up. Appreciate any thoughts/comments/critiques from the 12 of you that will read this!
- PHIâ€™s EnerPHit certification criteria for residences (pdf)
- passipedia entry on EnerPHit
- passipedia entry on thermal envelopes in PH retrofits
- passivhaus trust (UK) presentation on EnerPHit (pdf)
- Sustainable Energy Irelands PH Retrofit Guide (pdf)
- Dr. Burkhard Schulze Darup EnerPHit presentation (pdf)
- UKPH presentation on lessons learned from four EnerPHit
- 2012 UKPH Presentations (some great info on rehabs)
- Passive + Low Energy Architecture Conference Proceedings (more of this!)
- Tribus’s PLEA 2008 paper – Towards zero energy buildings: renovations (pdf)
- German article on a listed building renovated to meet PH
- haus der zukunft’s listings for energy rehabilitations
- ENoB’s listings of energy rehabs
- Ludwig Rongen’s presentation of a post-war era school modernization in Baesweiler (DE) retrofitted to reduce space heating by 90 percent (pdf) and to reduce CO2 emissions by over 500 tons per year. Boy, this sure makes the case that LEED’s not quite up to par…
- Great overview of PH- and near-PH energy retrofits, featuring a number of projects showing 76-93% reduction in end energy use – energy renovations with factor 10, Dr. Burkhard Schulze Darup (pdf, German)
It’s kind of an odd time of year with the holidays imminent, and other events having pushed the blog in the background. Every year Aaron and I commit to taking a day and devoting it to some sweet gingerbread architecture, but invariably end up on different sides of the country. So instead of dropping some guerrilla entry in a local gingerbread competition – a few modern ones that have piqued our spidey-senses over the last few years…
Looking at some of the older ones now is a little funnier than when they were first making the rounds, because of distillation through our Passivhaus lenses. This leads to some difficult questions… Is the U-value of gingerbread better than cork? Is frosting an adequate air barrier? Are sugar cubes thermally similar to AAC block?!? And if anyone has any tips on how to ventilate a gingerbread passivhaus, we’re all ears. We were thinking natural ventilation since the HRV ain’t cost effective at such a small scale. Here we go…
Something about this one that seems to reference unbuilt Chipperfield houses. Plus, I’m a huge sucker for a courtyard and redirected natural light. Can be accomplished on a Passivhaus, too!
A slick and delicious-looking lebkuchenhaus. Recipe, construction drawings available here.
the next two are some delish submissions for creative room’s 2010 gingerbread house competition…
delectable topography by busby perkins + will
mcfarlane green biggar A+D’s passivhaus tower (!)
‘Ginger Tower 062 is built with modern Passiv-Ginger-Haus technologies to reduce heat loss and is powered by a single Easy Bake Oven District Heating plant.’ – tres nice!
Marc Nuding’s Turmhaus fuer das Spreedreieck
Architizer’s recent competition had some interesting submissions… The Brasilia one was timely, especially given Niemeyer’s recent passing. The m+m tray is an awesome touch.
This last one may be the all-time fave, I’ve never seen anything as incredible… The ‘Schlossplaetzchen‘ by Kirsten Hüsig und Sören Grünert turns the sugar frosting into a structural element, yet still maintains a high level of transparency (especially for a gingerbread house). Shades of OMA’s facade on the Seattle Central Library? Yummm….
Happy holidays, folks! Stay safe, and stay warm.
As promised in our passivhaus v. pv post, here are a few PV installs that we don’t find overly offensive. Unsurprisingly, many of these meet Passivhaus – and no, that’s not a selection bias, these are just the solar panel applications we dig the most… Apparently, we really prefer when PV modules perform multiple functions and intentionality, planning and minimalist details /profiles are laid on thick!
So enjoy the pics, and feel free to add any extras in the comments.
Rolf Disch | solarsiedlung in Vauban. passivhaus + PV.
hermann kaufmann | gemeindezentrum ludesch (AT, foto: Bruno Klomfar). passivhaus + PV.
ETH/bearth + deplaze | neue monte rosa huette (CH). passivhaus + PV(!)
TU Darmstadt | 2007 winning solar decathlon entry. passivhaus + PV…
Beat Kaempfen | Sunny Watts (CH). Multifamily done right! Unfortunately, this Minergie-P-Eco project is on few (if any) radars in the US… It should be everywhere (so study up, kids!). Prefab’d, local materials and Passivhaus + PV. Beautiful…
brooks + scarpa | solar umbrella (LA)
The Passivhaus (NZEB) v. Net Zero (ZEB) debate has become an ongoing discussion that rears its nerdy head every few months. It really first took grasp shortly before GBA’s Martin Holladay published his net zero energy v. Passivhaus post. Recently, the topic has made its way into several conversations – and my arguments for NZEBs or NZEBs + renewables always spark a lively conversation. I was asked to put together a post collating my thoughts on why achieving Passivhaus should take priority over ZEBs, or at least before adding renewables.
It may be worth mentioning that I view this as an apples v. brownies issue (I’ll leave you, dear reader, to decide which is which). On one hand, extreme comfort and consumption reduction (Passivhaus), on the other – energy production (which may, or may not, entail significant energy conservation measures). PH + renewables was an active (and lively) topic in Hannover, and one of the more interesting aspects for me is where people fall on the spectrum – especially as it was a handful of Brits and Americans v. remainder on separating consumption and production.
As stated numerous times, significant energy reductions should be a priority (hence, Passivhaus). From an economic standpoint, I understand how PV makes sense for a home or business (albeit, a heavily subsidized one). However, a handful of ZEBs in a sea of inefficiency does little in terms of actual CO2 reduction. Instead, let’s be smart and have the foresight to retrofit (enerPHit!) + build an armada of efficiency (Passivhaus/Minergie/LBCs when Passivhaus!) and then, then! – once that’s been attained – let the energy companies do their thing (which they already do better than anyone else, anyway) to online larger scale renewables/offline coal plants and green the damned grid. This would have a far greater impact at lesser (collective) cost. It’s also on the radar for much of the EU – where in the UK, addressing demand could cut up to 22 power stations; and the Swiss are aggressively planning to reduce consumption by half (!) over the next 30 years.
Those aims, not coincidentally, parallel the goals of the incredibly ambitious PassREg program (Passive House Regions with Renewable Energies). For those that don’t know, PassREg is yet another program where the PHI’s leadership has been superb, and will leave the U.S. even further behind Europe. It’s literally the coolest thing since sliced bread, and makes me want to move back to Europe just so I can work on these, too. The PHI states that PassREg will:
‘…take a critical look the successful models employed by front runner regions, identifying the stakeholders involved, evaluating the driving factors and collecting appropriate solutions that might be applicable in other urban and economic contexts. In turn, the opportunities and existing barriers to the introduction and implementation of PassREg concepts in aspiring regions will be examined. Through PassREg, the wealth of knowledge that arises from this examination of the regions’ models as well as through the case studies of buildings in each region, known as beacon projects, will help aspiring regions to shape success models of their own and front runners to optimise what they already have…‘
That’s not to say I abhor ZEBs- we’d love the opportunity to crack open a few more PHs or ZEBs here at brute force – but if we’re going to shoot for ZEBs, it really makes the most sense in terms of comfort and economics if paired with Passivhaus/NZEBs first. Thus, I vote Passivhaus first…
Urban/MFH can be difficult to achieve ZEB
Even if achieving Passivhaus levels of efficiency, urban buildings and multi-family projects have proportionally smaller roof areas than detached housing, making it pretty difficult to achieve ZEB. And that’s before Donald Trump blocks your solar access with a brass-bedazzled tower. Additionally, urban rooftops are typically utilized as a deck or HVAC parking spot, which can interfere w/ incorporation of PV. +1 Passivhaus
Not all houses are ‘solar ready’
Not all buildings are ‘solar ready’ and enforcement/encouragement to make houses solar ready can have some aesthetically dis-pleasuring consequences. Do we really want to all have south facing shed roofs? Who wants to live in that world? Not this guy! What if my gabled facades want to face east-west? Much of the existing housing stock doesn’t have the roof area, orientation, or solar access to make a ZEB feasible, whereas updating to enerPHit or near-enerPHit levels may not be entirely difficult. Pushing the existing housing stock to ZEB with rooftop PV is so difficult, it’s only been attempted by a few projects. Furthermore, obstacles like trees (and power poles, overhead wiring) can seriously affect the output of a PV panel (even when bare in winter, as Marc Rosenbaum recently attested). Whereas, trees are a pleasant thing to look at in a warm, comfortable Passivhaus, and can provide shade from overheating in summer. +1 Passivhaus
PH = smaller PV area needed
Achieving Passivhaus levels of efficiency is one of the surest ways to ensure your PV array doesn’t have to spill over the boundaries of the building. This is true for homes and commercial buildings. As we noted a few years back, the Bullitt Center’s PV array could have avoided intruding into the public domain had it met Passivhaus. The amount of PV needed for North American Passivhaus homes to become ZEBs is pretty small – especially compared to solar deficient Central Europe. In looking at some of the Building America projects incorporating PV, in nearly every case, a Passivhaus would have resulted in significantly less PV than what was utilized(!). The PV arrays for many net zero projects are much larger than would be needed for a worst-case Passivhaus, significantly larger than an aggressively efficient Passivhaus. Instead of having PV bleeding out over the entire roof and adjacent garage – you could conceivably get by with just adding PV on your garage. +1 Passivhaus
Existing Stock could be cheaper if ‘PH + PV’
When you have an existing project that could be considered ‘solar ready’ – e.g., a generous south facing or large enough flat roof – it may actually be less expensive to achieve Passivhaus/enerPHit and add renewables, over adding lots of PV. Those existing projects in the US that have been able to achieve ZEB status seemingly do it on the backs of large tax credits and incentives (as was the case for the Grocoff Net Zero project: $49k out of pocket, $43k incentives/credits!). In a brief breakdown of their numbers, an ‘EnerPHit’-type reduction actually would have resulted in avoiding the GSHP ($21k) , and a ‘Passivhaus + PV’ system would have been anywhere from 33-59% smaller. Even tripling the insulation/airsealing cost, adding minisplit and $100/sf PH-certified wood windows, the Grocoffs would have spent much less money to achieve ZEB – which by the way could have allowed those generous tax credits and incentives to be spread around to more projects and have even greater economic and environmental impacts. +1 Passivhaus
New buildings could be cheaper if PH + PV
We’ve looked at this on a couple of buildings here in the NW that aimed/are aiming to be ZEBs. Two of the more high profile ones (Bullitt, zHomes) could have actually saved quite a bit of money (through PV/mechanical costs) by achieving Passivhaus first. We’ve been stating this for years, as have others in the PH community – but I think we’re finally at the point where the cost to achieve PH is exceeded by the reduction in PV costs through meeting Passivhaus. Onion Flats PH+PV rowhouses in Philly ($129/sf!) are a terrific example of this. The Salem Passivhaus would only need a 2.8 kWp (PHPP) – 3.8 kWp (actual) photovoltaic system to offset energy consumed. In Germany, where installed PV prices are even lower than the US – the emphasis is still ‘Passivhaus first, then renewables‘. They’ve been doing this in solar-deficient Austria/Switzerland/Germany for a decade now. They’ve even surpassed net zero through the incorporation of Passivhaus: Passivhaus + renewables = plusenergiehaus (a.k.a. producing more than consuming) – and this was also a large focus in Hannover. As the costs to achieve Passivhaus in the States lowers due to familiarity, smarter designs/PH integration and affordable/ locally mfr’d products (pretty please!) – this will be even more true. +1 Passivhaus
PV ain’t pretty
Yup, like semantics, aesthetics count. The nasty array on the banal house above isn’t even an extreme example. Sure, there are a few BIPV/ZEB projects that incorporate attractive installs (next post!) – half of them are Passivhäuser. But let’s be honest, most PV installations are an aesthetic abomination. PV panels tend to be rather crude, don’t work well with certain roof types (mansard! hip!) – and if the roof angle ain’t where it should be for optimal performance, racking the panels up or down on a tilted array just makes the installation look worse. This goes doubly for solar hot water installs, which except in certain applications don’t really make economic sense anymore, anyway (as Martin Holladay claimed, solar thermal is dead!). I just don’t get the appeal of looking at roof-mounted PV arrays, when they’re usually so poorly installed that the aesthetically ridiculous VW beetle spoiler looks light years better. +52 Passivhaus
PH wins on the embodied energy argument
As we’ve blogged (and the PHI and others have shown) the additional embodied energy required to hit Passivhaus is nominal, recouped in a few years at most (or less – if using natural materials). Whereas, studies on the embodied energy payback of solar panels are on the order of nearly a decade (or more) once accounting for the structure, inverter, location/orientation/system efficiency. +1 Passivhaus
PH wins on quantity of rare earth minerals required
You can build a Passivhaus almost entirely without rare earth minerals, but a photovoltaic panel? Not so much. If mountaintop removal is environmentally devastating, if the tar sands are an environmental desecration – should we really give rare earth minerals a pass because iPhones and androids are überkůl? +1 Passivhaus
A Passivhaus is a Resilient House
Resilient buildings have been getting a lot of (deserved) attention lately, thanks to Alex Wilson’s latest venture. In a lot of respects, this is. A certified Passivhaus should have little issues with durability (part of the reason for the extreme airtightness). A grid-tied PV won’t keep you warm at night during a blackout. Roger Lin’s Arlington Passivhaus lost power for nearly 2 insanely hot and muggy days last summer. How’d the house perform? Extremely well…
‘…While the outdoor temperature was 92 degrees, the basement was a comfortable 73 degrees. First floor was a warm but not unpleasant 81 degrees. Second floor was 79 degrees…
Insulation Really Works
First, all the insulation in the walls and roof is effectively isolating the indoor environment from the outdoor elements, slowing down the effects of extreme outdoor temperature changes, i.e. after 40 hours of power loss, the first floor only warmed up by 6 degrees (75F -81F) and second floor by 2 degrees (77F-79F)…’
And, as Greg Duncan recently tweeted, the ‘Winter of ‘extreme storms’ is new norm. Passivhaus ensures comfort from drafts, cold; resilience against outages and respite from loud winds‘. Whether it’s holding in heat, keeping the heat at bay, reducing external noise – Passivhaus bests a ZEB in nearly every case. Another way to think about it…’Don’t like living next to that loud street or in that airport approach? Maybe you could use your solar panel as a sound barrier!‘ +1 Passivhaus
ZEBs are not bound by QC
Finally, and I think this is one of the most important reasons, Passivhaus (at least in Europe) is much revered for being the quality control standard (despite PHIUS’s ridiculous proclamation to the opposite). Recently, a costly ZEB wasn’t built well, and during the monitoring process, it became clear there were performance issues. This Living Building, the Tyson Living Learning Center, required an envelope audit – less than six months post-construction! Not only would shooting for Passivhaus have saved them the headache of the audit, it would also have saved some serious coin. The Center as a ‘worst-case Passivhaus’ would have reduced the amount of PV by two thirds (!) compared to what eventually was installed/needed to meet LBC. This debacle led to our critique of the LBC program, which we actually support and would love to see heavily adopted – just in conjunction with Passivhaus. +1 Passivhaus
So fix yer damn U-values!
Focus on your air sealing.
And build a stunning Passivhaus. Because then – without any horrendous, oversized, budget-busting photovoltaics slapped on top – your house can truly be a very, very, very fine house!
- Eike Musall’s ZEB map
- UK/IE Passivhaus map
- Global Passivhaus map (5,680 projects)
- PHI’s Passivhaus database
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