Dew Point Calculator for Assembly

This is a tool I scripted in grasshopper for my undergraduate architecture students in a building systems course. The tool abstracts a wall or roof 'typical' assembly to help inform where vapour controlling layers and potential condensing surfaces may occur in a design assembly by graphing the temperature gradient through the assembly and calculating the dew point (internal). By studying a proposed roof and wall in isolation, it can inform the process of detailing the juncture between those two assemblies.

Here's how the script looks with the algorithm doing all the calculation and drawing on the right and the control panel for material and design parameters on the left.

Here you can see the organization of the file with the notations and group labels. The script uses two different dew point calculations for comparison.
This is an example wall assembly with a total R value in US units of 22. Material thickness (mm) and thermal resistance (u value) parameters are inputted to calculate R value in SI units which is then converted to US units. Design parameters are set to study a particular interior/exterior temperature relationship and a desired interior relative humidity. The tool then graphs the temperature gradient through the assembly and located the dew point as a coloured point (the yellow and orange Xs).

Give it a go and feel free to comment or ask questions. A 2D typical assembly dew point calculator like this is of limited value, but can be a useful step towards developing well understood details at assembly junctures.

Attachments:

Material_Assembly_Dewpoint_Calculator_NDD2016.gh, 63 KB

Replies to This Discussion

Permalink Reply by Matt Gaydon on February 2, 2016 at 2:18pm

Did a little edit of your code so its easier to add more materials and does not look so scary for those starting out in GH. Hope you don't mind. I would check it all matches your original though, i have had a look but may have missed something.

Attachments:

Material_Assembly_Dewpoint_Calculator_NDD2016 MG EDIT.gh, 35 KB

Permalink Reply by Naryn Davar on February 3, 2016 at 5:49am

Cool thanks! I just had a quick look this morning and it looks great - so much cleaner. You just merged all the data streams for each material and ran them through a single set of components instead of the copied sets I was using? Brilliant!

I'm still working on making my scripts 'less scary' for new users haha. I'll dig into this a bit deeper for next week as I'm going to be introducing this tool to some undergraduates in their first year of architecture who could use a gentle introduction to GH.

Permalink Reply by Matt Gaydon on February 3, 2016 at 5:58am

Yeah, needed to use a little C# Component as Grasshopper does not have a mass subtract component currently but other than that is all standard native GH components.

Permalink Reply by Ángel Linares on February 3, 2016 at 7:17am

Very nice and interesting topic and gh definition. This year I could observe how a small improvement in an old house (changing old windows for new double glass and insulated ones) ruined the walls of the house because of this; with the old ones some ventilation was always happening due the lack of sealing and proper fitting so the temperature never rise over the dew point (in contrast with the cold interior face of the wall). With the new ones humidity stains are appearing all around...solution: increase insulation and add a proper cavity (with drainage) using some panels in the interior face.

I don't understand how people calling themselves architect doesn't know about this topic, so important to design comfortable and "healthy" spaces.

Permalink Reply by peter fotiadis on February 3, 2016 at 8:39am

Ventilation (and water vapor barriers) is a myth well supported by makers that do cheapo stuff. If the Dew point is INSIDE the insulation AND the material doesn't absorb water things are well under control. Obviously exterior insulation (with a few exceptions: restoring classic buildings etc) is the way to go .

Given the opportunity I would strongly suggest the Bible on insulation matters:

Practical Guide to Flat Roofing (internal Pittsburgh Corning stuff available on request).

by my good friend Cristian Courtois, Pittsburgh Corning Europe: Critical for anyone taking his job seriously. Cristian is a pensioner by now but his legacy reigns supreme.

A milestone by any means that one.

Permalink Reply by Naryn Davar on February 3, 2016 at 2:27pm

This is a big issue where I live, the housing stock is often in the 50 - 200 year old range and all light frame wood construction. People insulate the walls by blowing in cellulose and replace the old single-pane windows that are double-hung with modern vinyl windows spray foamed in place. Suddenly a house that has been fine for 200 years has all kinds of moisture problems, mold and condensation on their windows. Installing an HRV as part of the overall tightening of the envelope can mitigate the condensation on the windows but it's fairly common for poorly thought out or executed attempts to retrofit the energy performance of a historic building to result in moisture problems.

Turns out the best thing for a historic home in eastern Canada is a cheap and plentiful (and relatively clean) radiant heat source...

Permalink Reply by peter fotiadis on February 4, 2016 at 1:00am

Yikes + yikes.

Anyway back to the C# thingy (I've started doing some preliminary stuff: related with managing the Numero Uno thingy: material "tables" (4 classes used: insulation, cladding/plaster, water proofing and er ... the obvious).

However the "assembly" must comply with some part naming system as found in BIM apps (my core app is AECOSim) and obviously with CSI type of specs and the likes. I fact I have a complete "app" that does this ... but (a) is strictly internal, (b) is written for AECOSim/Generative Components by yours truly.

Graphics is also a serious issue and especially combined ones: for instance imagine someone naive enough to use polystyrene [hence the vapor barrier] to do this type of disastrous roofing (meaning that DP is one thing, water absorption is another animal much much more important than DP itself > polystyrene absorbs all the condensate > Armageddon > Adios Amigos):

By combined I mean this "typical" scenario as well:

Permalink Reply by peter fotiadis on February 4, 2016 at 4:06am

BTW: In order to this properly I need k moisture (W/mK) thermal conductivity values for insulating materials. I don't have much data on that matter ... since there's only one thermal insulating thingy allowed in my practice (the benefits of owning the thing, he he).

Fill this xls please

Attachments:

Utopia_V1.xls, 21 KB

Permalink Reply by peter fotiadis on February 4, 2016 at 9:55am

Added some materials more in 4 "classes" (fill this please instead of the V1).

But this thread of yours is a giant pile of worms - although of a critical importance:

DP is one thing ... however other things play a far more important role in AEC design ... thus picking a material from some related Trees and making an "assembly" [without an extensive information provided via some properly structured RDBMS] ... means pretty much nothing in real-life. For instance: what's wrong with these combos in the long term? (from a very reputable cladding maker):

Attachments:

Utopia_V2.xls, 36 KB

Permalink Reply by Naryn Davar on February 4, 2016 at 10:53am

Hah. Well it was a first pass at a tool that is used to teach the basic concept of dew point calculations but rather than teaching the psychrometric chart and manually graphing the temperature gradient I thought it was an opportunity for a simple introduction to rhino and grasshopper in the context of architectural design process for students with little or no experience using design software.

The tool you are describing is far beyond what is required to have a conversation in the classroom about dew point and the obvious advantages in using a tool like GH to make iterating efficient - as you say, you need to be taking into account a more complexed understanding of the materials and assembly to be useful in predicting reality in practice. You are describing a professional level tool, which I would be very interested in seeing but is likely overkill for my needs. We are at the beginning of teaching a lot of these concepts so sometimes a simpler, more abstract tool is more effective. Not sure what else to say. Thanks for your insights though. I'll do some looking to see if there is foamglass being sold locally by any distributors.

Cheers!

Permalink Reply by peter fotiadis on February 4, 2016 at 11:15am

Hmm ... I say:

1. Students trained via the White Side (all simple and well) are dead men walking > there's war out there (and takes no prisoners). Ignorance IS a bliss but an ignorant is not blessed, he he.

2. If on the other hand students are introduced to the Dark Side (everything is far far more complex than it appears on first sight) ... then ... maybe ... just maybe ... they have a slim chance to survive.

Moral: press them to the max from day zero > if some brake > sorry Amigos .. blame Darwin.

More (with a tech preview of the whole approach) this w/e.

May the Force (the mat black option) be with us all.