[Greenbuilding] Passiv Haus and Thermal mass (wasGroundsourceheat)

JD contact (free.fr) johndaglish at free.fr
Sun Jan 30 14:32:13 CST 2011


Hello John,

I found this in my outbox from last year~


PHPP is a monthly steady state model that has been correlated against
dynamic hourly simulation model Dynbil, of the PaassivHaus Institute and real world
measurement.

PHPP demo
http://www.passive-on.org/CD/

A small tutorial of critical elements for the PHPP (Passivhaus
Planning Package) but note that the package comes with
a +100 page manual.
http://www.altompassivhuse.dk/download/kursus/8_Workshop-phpp-day2.PDF

It is significantly better than
models such as used in the UK, BREDEM, a steady state monthly model
used for regulatory calculation but without the competance need for
good dynamic modelling.
http://www.aecb.net/PDFs/BRE%20response%20to%20Paper%203%20Mar06.pdf

It is not as good as a dynamic model calculated with finesse and
expertise. And that is a problem as even with good model description
(one report showed -31% to +13% results) analysis of the
performance of good energy modelers is probably around +/- 10% * De Montfort University (DMU),
in the UK did an statistical analyis of cumulative error variability
of the performance of SER-RES/SUNCODE in the 90s.

Some of the validation done on ESp-r :
http://strathprints.strath.ac.uk/5819/1/strathprints005819.pdf

Now if you look at real buildings and theoretical energy modelling
using steady state models you will see for instance in the UK around 30%
average difference! So in this respect PHPP is much better and
probably sufficient for the passivhaus type building.

The study of the validity of PHPP with regard to over 100 buildings
(Cephus project) is here, yes there were a few big outliers but read the
report most of these were technical setup / human problems  :
http://www.passivehouse.com/07_eng/news/CEPHEUS_final_long.pdf


Arguably the new Hot 3000 canadian modeller using the ESP-r calulation
motor developed in Europe by Strathclyde University (and the European
reference and now open source) should be quite good. It is a 3d
volumetric model with heat balance equations being solved at every
time step by finite difference method. In its basic form it is not for the
faint hearted, it being a heavyweight university research tool.

ESP-r - Heat balance equations are solved with the finite difference
method at each time step.

energyplus - Heat balance equations are solved with the response factor method
http://wiki.naturalfrequency.com/wiki/Thermal_Analysis_Methods


In most dynamic models in the US the heat balance equations are solved
with the  response factor method models using algorithms (approximations) fourrier
transformations to shorten calculation time. It is a
little easer to write algorithms for service plant... thus the bias
in America which extensively uses HVAC. It is very good but arguably
the ESP-r model is a
little bit more accurate, particularly calulating the free running
performance of heavy weight buildings.

You can see the comparatif performance (not against real buildings) of the major modellers in the
Besttest standardised performance test.
http://www.nrel.gov/buildings/energy_analysis.html#bestest

There was a program of validation of software against controlled test
cells (one room) in the European Union during the 80-90s and as I
remember ESP-r was the best but certainly not perfect.

In the real world you have people and HVAC controls which do
the silliest of things sometimes!!

regards

John Daglish

Friday, July 16, 2010, 5:58:44 PM, you wrote:

JS> I think that is the study that is often mentioned. Median tracked but variation was large, eg, there is a table in the report (which mostly deals with multifamily, less so with single family) and
JS> the ratio of the modeled energy prediction for HEATING only divided by actual varied from about 0.5 to 1.7.  Quite the scatter!!! Also, this is just for heating energy, which should be pretty
JS> easy to get. Most standard models would actually do better.That said, low energy houses like PH have a lot more noise, as it takes little in terms of solar reflections, higher interior electrical
JS> gains, small mechanical system or enclosure flaws to make a big difference.

JS> But, the conclusion I reached is the PHPP is no better, and probably a bit worse, than most models. Yet I keep hearing about this study that shows PHPP is great.  Have asked numerous people where
JS> this study is .....

JS> I still LIKE PHPP and would use it or similar to do modeling for low energy houses. But I just cannot find any reason why it is better.

JS> On 2010-07-16, at 11:42 AM, Alan Abrams wrote:

>> John
>> 
>> sorry, it's not at my fingertips; it was presented during consultant class.  the 115 house sample sounds familiar; it may be the same one you refer to.  IIRC, the correlation was in the 80-85%
>> range (of very low numbers to begin with), but the median tracked right on the money.  
>> 
>> still, memory plays tricks; will dig for it when I get a chance...
>> 
>> AA
>> 
>> On Fri, Jul 16, 2010 at 11:09 AM, John Straube <john at buildingscience.com> wrote:
>> Can you tell me where I can find this study? 
>> The only study I have found is the CEPEUS 115 home study and it did NOT show very good correlation. Adequate yes but not good. 
>> 

JS> Dr John Straube, P.Eng.
JS> Building Science Corporation
JS> Somerville MA     Waterloo ON
JS> www.buildingscience.com



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-- 
Best regards,
 JD                            mailto:johndaglish at free.fr





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