[esp-r] Re: storage of humidity within massiv components ?

Thu Nov 29 13:50:20 GMT 2007

Hi Jake, 

Every simulation tool has strengths and weaknesses. ESP-r's treatment of moisture diffusion (or lack there-of) is a known deficiency. It's an area of interest for us, mostly because we cannot accurately model night-time natural ventilation and free cooling strategies without computing the latent load resulting when moisture from humid air is absorbed in the building structure and furnishings. We have some funding to improve this aspect of ESP-r, but the work is presently on hold while we focus on other priorities.

As I'm sure both you and Professor Straube can attest to, the validity of a model's predictions depends as much on how well the user understands the underlying algorithms as on the model's theoretical vigour. Even comparatively simple tools with well-known flaws (for example, HOT2000 and DOE2.1) can be applied accurately as long as their limits are respected. And that's perhaps the biggest challenge to using ESP-r --- its limitations are not well documented and often difficult to discern. 

A few years ago, the US DOE, ESRU and SEL produced a fairly comprehensive report describing the capabilities of prominent building energy simulation programs. WUFI didn't make the list, probably because in 2005 WUFI (then WUFI-ORNL/IBP) was focused primarly on mosture transport and its energy modelling capabilities are a fairly recent addition.

http://www.eere.energy.gov/buildings/tools_directory/pdfs/contrasting_the_capabilities_of_building_energy_performance_simulation_programs_v1.0.pdf

- Alex 

-----Original Message-----
From: Jake Zwart [mailto:jake.zwart at sympatico.ca] 
Sent: Thursday, November 29, 2007 07:50
To: Ferguson, Alex
Subject: FW: [esp-r] storage of humidity within massiv components ?

Hi Alex:

I thought I would forward this email on to you.  If esp-r has one of the
better whole building simulation engines, and people struggle with it, does
that say something about the other simulators?

I am sort of passing this on, in case it may a topic of interest for your
research should you try for an advanced degree.  It may also be a of
interest should proper hygric modeling be incorporated into esp-r.  I
suppose to do something like that may mean a completely new simulation
engine would be developed and the two would both be operational, with the
user selecting which one.

I know that John Straube is very active in moisture transport analysis in
buildings and the potential harmful effects of a vapour barrier depending
upon the climate.  Research in this area, especially if it can be
incorporated into building simulation tools used by the government would
definitely be useful, and may even allow for an easily accessible engineered
alternative to vapour barriers, ultimately leading to changes in the code
regarding vapour barriers.  If this line of research does interest you, you
might consider John Straube as a supervisor, or co-supervisor.  As
co-supervisor, you might not even have to move.

I took a look at the WUFI web site and it looks good but TRYNSIS type
prices.  I did not see any indication of plant components.  There is a free
educational and non commercial version though.

Jake

-----Original Message-----
From: John Straube [mailto:jfstraub at civmail.uwaterloo.ca]
Sent: Wednesday, 28 November, 2007 22:18
To: jake.zwart at sympatico.ca
Cc: 'Pueltz, Gunter'; 'John Straube'
Subject: Re: [esp-r] storage of humidity within massiv components ?

Hi there Jake
esp-r does not handle moisture well. We have struggled even with the energy.
I have modelled buildings with earth plastered strawbales and compared them
to field measurements using WUFI with very good results.
WUFI-Plus is a new whole building program that properly accounts for thermal
mass, hygric mass, and ventilation energy, moisture and even CO2. This is
what I would consider.
The good news for Guenter is that this program is developed and supported
close to their home at the Fruanhofer Insitut fuer Bauphsik in Holzkirchen.
Checkout www.wufi.de

Jake Zwart wrote:
> Hi Gunter,
>
> I have been told that esp-r does not model moisture storage in walls which
> is an essential element of moisture calculation.  Not sure about the
vapour
> diffusion part.
>
> I have attached two papers that talk about moisture modeling in walls.  I
> have tried the simpler steady state method within a spreadsheet and it is
> quite easily implemented.  The other paper offers about a 5 year old
review
> of simulation packages that may do the modeling that you require.
>
> I find the web site www.balancedsolutions.com quite useful for research in
> this area.
>
> I have cced the author of the papers, in case you have any direct
questions.
>
> I wonder if there has been any discussion about implementing moisture
> transport and storage within walls in esp-r and what the interest would
be.
> I think it would be quite useful.
>
> Jake Zwart
>
> -----Original Message-----
> From: esp-r-bounces at lists.strath.ac.uk
> [mailto:esp-r-bounces at lists.strath.ac.uk]On Behalf Of Pueltz, Gunter
> Sent: Monday, 26 November, 2007 10:42
> To: 'esp-r at lists.strath.ac.uk'
> Subject: [esp-r] storage of humidity within massiv components ?
>
>
> Dear ESRUs,
>
> I have to simulate historic rooms with a bit humid walls by ESP -r.
> Concerning humidity WITHIN the massiv components (not only at the internal
> surface) following questions:
>
> 1) Does ESP -r calculate the humidification + de-humidification of walls
> resp. the storage of humidity in the walls ?
> In the material database a vapour resistivity is defined for each material
> ....
> But does ESP-r model vapour diffusion within a multi-layer component ?
>
> 2) If there exists a humidity source - e.g. in the ground (groundwater or
> rain water, which raises upwards into the walls of my rooms) - how can
such
> a humidity source be implemented WITHIN a multi-layer-component (e.g. a
> wall) ?
>
> Any idea or comment appreciated.
>
> Regards,
> Gunter
>
>
> --
> Dr. Gunter Pültz
>
> Müller-BBM GmbH
> Robert-Koch-Straße 11
> 82152 Planegg
> Telefon +49 (0)89 85602 - 336
> Telefax +49 (0)89 85602 - 111
> http://www.MuellerBBM.de
>
> HRB München 86143
> Geschäftsführer: Bernd Grözinger, Dr. Edwin Schorer, Norbert Suritsch
>
> _______________________________________________
> esp-r mailing list
> esp-r at lists.strath.ac.uk
> http://lists.strath.ac.uk/mailman/listinfo/esp-r
>
>
>

--
Dr John Straube, P.Eng.
Associate Professor
Dept of Civil Engineering & School of Architecture
University of Waterloo
Waterloo, ON Canada