[Greenbuilding] Aggressively Passive: Building Homes to the Passive House Standard

Sun Jan 9 15:19:22 CST 2011

I wrote
<A higher standard than the PH one is a NetZero energy house.>
to which Mr Abrams wrote
<yadda yadda. >
Not sure what to take from that.
But I will say I find it  odd that many of the people who are willing to go to great lengths to get a house PassivHaus certified are so dismissive of any approach that delivers a lower energy footprint.
One of the things I like about PH is it laser focus on energy: but this leads all kinds of articles and people to say "the most stringent standard in the world" and other such clap trap.  This is the reason I always bring up NZE homes when people claim PH is lower than any other standard. No it isnt.  And, BTW, NZE homes are not as good on an energy front as energy-plus homes, of which there are numerous out there, homes that produce more than they consume.

Not sure which BSC house plan you were looking at, but ALL of the homes we build and claim as low energy (and some we dont) follow the same principles, those laid out 30 years ago in things like the R2000 program in Canada.  The only difference is the mix to get to a certain target.  This mix, combined with details of durability, constructability, affordability, and reliability are what makes one house better or worse or different than another. 
This is what I find maddening about naive PH adopters: they seem unaware that PH is offering almost nothing new other than a specific packaging. It may be that for your client, and your climate, the best mix of strategies will be different (perhaps less airtightness, perhaps better HRV, or perhaps more of a focus on durability, etc.)

I can only think that the reason some people find PH so appealing while putting up with its many oddities is that they dont know that there are other programs and approaches out there that have been doing the same thing. R2000 homes, for example, use a binned (they use more bins the PHPP, but still) program, HOT2000, that you can download for free, and have all the features of PassiveHaus except for the per square meter energy target (a great idea) and add some air quality and durability features.  This has been going on since 1984, and has trained thousands of people to build thousands of homes.

Systems based, performance driven low energy house design is a commonality of many many companies, programs, etc.  There is nothing special or new about this, but it may be that, again, people new to the idea of low energy buildings are simply unaware that this is a common and successful approach honed over decades in all climate zones.  Perhaps that is what I am missing in my understanding.

There is no doubt that PHIUS is currently small. I dont think this is the problem.  The problem in my experience has been a lack of a willingness to modify PH to US conditions.  Dont know why this is, except perhaps they dont have the technical ability to convert units and standards, but I am told the German ones are perfect.  It would be pretty easy to switch the area measurement from DIN (Deutsche Industrie Normen) to ANSI (American National Standards Institute) and then adjust the targets accordingly.  Would be really easy to require CSA/UL standard for HRVs.  Would be trivial to adjust the EuroNorm window standard to NFRC ratings. In fact, I and others would be willing to help build the technical database to support such adjustments.  But suggestions by myself and others along this line have been rebuffed, ridiculed, and attacked.  It has left me and others (who are less public about it than I) bewildered and confused, and leads to me believe that PH will be strangled by dogma in the US after a few thousand houses have been certified.  I already see good things coming out of people looking at PH and learning the basic principles and approaches to low energy housing. I also see people wasting time and resources trying to reach certain targets that dont necessarily make sense (like getting to 0.6ACH at 50 in San Francisco!).

I dont think NZE is a superior answer.  However, I believe homes with an energy budget, and a size budget are the long-term way to deliver the most homes that consume the least resources. Figuring out such targets and how to measure them will not be easy, but it will take collaboration and accommodation of each region, and will need to change with time.  PH does not currently have these attributes, it just has an energy budget.

PS. For those who care, I have written a bit more at our website buildingscience.com,  BSI-025 and BSI-026

PSS.  Most BSC houses are not ultra low energy or NZE, most fall in between about 30% below code (hundreds to thousands per year) to 60% below code (handfuls) with one or two NZE as research.   And we usually use a DOE2.1E based hourly simulation engine, like most of the bigger (and many small) low energy building design firms do.  PHPP is a very nice Excel spreadsheet, one I think is useful in many regards, but it can be a little limiting and is certainly not the most powerful or accurate model, just a good one like many others.  We have numerous inhouse Excel spreadsheets we use for preliminary design.

On 2011-01-09, at 12:42 PM, Alan Abrams wrote:

> <A higher standard than the PH one is a NetZero energy house.>
> 
> yadda yadda.  what I see out there (as greenbuilding laity--not as an engineer) is convergence. Last fall, I had the opportunity to study the plans for the Net Zero Energy test house, designed by Building Science Corp--and--Lo!--it was in essence a passive house.  
> 
> Or vice versa--one could say that PH--which focuses on envelope design and internal systems--is the optimal platform for adding renewable systems to achieve net zero or positive performance.  
> 
> Anyway, speaking of the NZ test house--it shares with PH the same principles--air tightness, super insulation (by code standards), fresh air ventilation system, dynamite windows, and a killer job with mitigating thermal bridging.  Where it beats the shorts off of Passive House (based on their manual of standard details) is that it is carpenter friendly, using substantially conventional framing, with some complex but straightforward and consistent rain screen, air barrier, and exo-insulation details.  I did not get my hands on any of the energy modeling for this project, but I assume it was done on a platform that is analogous to PHPP.  
> 
> The greater commonality, however, is this: looking at energy design from an integrated, systematic, performance based POV, rather than a prescriptive approach.  To me, with 35 years in the trenches, this was the most important thing I took away from Passive House training.
> 
> With regard to the deficiencies of Passive House for the US--please consider that PHIUS is a shoestring operation, basically created out of little more than the ceaseless and heroic energy of Katrin and Mike, and a few dedicated staffers.  If they had the money and the muscle of DOE behind them, they could resolve the discrepancies in ERV and window ratings, and so on. They could also tweak PH to account for the wide range of climates in the US, particularly in managing latent heat loads.  Instead, their limited time and resources are devoted to training and certifying projects.
> 
> nevertheless, I am skeptical of all orthodoxy.  I like PH for a lot of personal reasons as well as professional, but if NZ can prevail, and really have a broad impact on design, amen.
> 
> AA   
> 
> Alan Abrams
> Abrams Design Build LLC
> A sustainable approach to beautiful space
> alan at abramsdesignbuild.com
> www.abramsdesignbuild.com
> 202-726-5894 o
> 202-437-8583 c
> 202-291-0626 f
> 
> 
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John Straube
www.BuildingScience.com

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