in pursuit of energy efficient minimalism

Passivhaus Retrofits – Greenest o’ the Green

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.

Detached Housing

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)

Rowhouses? plenty!

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)

Skyscrapers? Indubitably.

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)

Institutional? Oui…

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)

Historic? Check

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!

Additional info:

• PHI’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)

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