The ABC's of WUFI - PT. 2 Component Building

Last week we entered the project information.  This week we start actually building an assembly the easy way - at our computer with our coffee and croissant close by!

First, a bit of housekeeping.  WUFI will default to SI measurements.  If you want to model and test in IP, be sure to change that by selecting “Unit System” from the “Options” pull down menu.  Be sure to click the “Use as Default” box if you desire.

Let’s open the component section of the project and look at the starting screen for designing an assembly.  You will notice that there is some information there, but it is like looking at a lump of clay before the artist does something with it.  “That’s a mighty fine lump of clay you got there!”

So, let’s pick a material for our lump of clay to be.  Clicking on the “Material Database” button brings up a new window.  It starts with the Fraunhofer Database of materials, and unless you are working with those, you will want to be in the generic or the North America database.  Note, that as a user of the free version of WUFI you are unable to add materials or change much of their information.  This is because you should purchase the full version if you will be modeling projects commercially so the fine minds at Fraunhofer IBP can continue to bring you the gold standard of moisture migration software instead of asking if you want fries with that sandwich!

I went into the North America database and chose cement board for my starting material.  WUFI works with the materials set up to have the exterior on the left side of the assembly, and the interior on the right.  When it adds new materials, it adds them to the right so I always build my assemblies from left to right, though I could click and drag a material to a different position in the assembly if I decide it needs to be located somewhere else.

You will notice that now there are two grid sections under the initial lump of clay.  It may look like it is still a lump  of clay, but it is actually now considered cement board and that material just happens to have the same default grey color.  (You can’t change material colors in the free version, but you can in the Pro version.)  Once you have defined what material your layer is you will see the grids.  If you add a new layer and have not yet defined what material it is the grids will disappear.  You only need to define the material for each layer and the grids will be there.

The grid areas serve two purposes.  The one on the top represents the entire assembly and will show camera locations, water sources, and heat sinks associated with each material.  The bottom grid area is specific to the selected material you are looking at.  You can set a camera position by clicking on a segment of the top row and then be able to see results related to that camera when you are done.  If you forget to set a camera, or don’t realize you will need one, you can still go back and look at data like that after a calculation, it’s just convenient to have it done from the get go if you know that you will need it.

Adding new layers is as easy as clicking a button.  Need two of the layers of the same material?  Duplicate the selected material with the click of a button.  You are able to change the thickness of your materials but you must NEVER change the thickness of your membranes.  This is because they have been given special properties so that they can be seen in relation to the other materials.  If you have a foot of concrete and a membrane next to it then another foot of some other material, you would never see the membrane you entered even though for calculation purposes the computer would know it would be there.  Just so that you know as much as the computer, the designers gave you magic magnifying glasses when it comes to membranes and you can see that they are there – just don’t change the thickness of the membrane because the magic won’t play nicely with your calculations if you do.

I went ahead and added the rest of the materials I want in my assembly for this case.  I need to go back and change the thickness of the fiberglass because the default measurement is for a 2x4 wall.  Be sure you have the thicknesses of the materials listed correctly so that you get as good of a model as possible.  As with anything – garbage in means garbage out.

Up Next – let’s Sink our teeth into the Source of the problem.

The ABC's of WUFI - Pt. 1 Project Info

This week we’ll start with the opening screen information.  This is important to fill out with the specifics that will allow you to come back at some later date and figure out just what you were modeling.  It’s possible that you may do more than one wall type for a project, so keeping it spelled out plainly from the beginning will help you later on. 

As you can see from this next picture, you get a fairly easy to understand fill in the blank page as the first page you see when you open a new project.  There is some default information available, such as what units you are currently working in (located at the bottom left corner of the page) and if you have any calculation results yet for this project.  Since you are just now starting a project that will state there aren’t any available.  Once you calculate some, that statement will change. 

If you would like to add a picture of the project or assembly you are modeling, it is as simple as clicking on the Add Picture button, selecting an image from your computer and it becomes part of the file.  If you want to add additional images you can and then use the arrows to step through them. 

The Project name of this file does not change on the main WUFI screen, but you can change the name of the Case that you are working on.  To do that, click on Case 1 and the screen advances to a page where you can name the case you will be modeling and enter some remarks.  It is best to use some kind of consistent naming architecture when naming your cases so that you can quickly identify what you are looking at.  “Wall” may tell you it is not a ceiling, but if you have a 2x6 wall, a sip wall, a trombe wall, and a brick wall you won’t have any idea which one you are looking at.  

Also, you may want to try that 2x6 wall with several different kinds of insulation or other materials.  Specifying “2x6 cellulose OSB” would tell you it wasn’t your “2x6 fiberglass plywood” case.  Keep the descriptions short and you will be able to look through your cases easily.  You can slide the project information to the right a little if you want to see more of the case descriptions.

If at any time you find yourself a bit lost on a WUFI page, you can get to the help screen for that page by using the F1 key.  The WUFI help guide is one of the most excellently assembled help guides I have seen.  They really worked hard at making it useful.

Up Next: Let’s create a construction!

THE ABC's of WUFI - Series Intro

WUFI is a software program for predicting moisture migration through a construction.  There are several different versions, including a new 3D one available through PHIUS that is combined with science based on the Passive House principles to model a construction prior to it being built.  This series will not focus on that version, but instead will deal directly with the free 1D version of WUFI, developed by the Fraunhofer IBP in Germany, that is available through Oak Ridge National Labs.

I live near Seattle, and if anyone has heard anything about this area, they have most likely heard about our rain.  It’s not like it is torrential, blinding, or particularly life threatening, but it can be a nuisance because it drags itself in and stays a while.  We get nice green trees and fields, and a fabulous appreciation when that bright shiny thing shows up in the sky.  (It is outside today as a matter of fact!)  But we also have had a lot of issues with water intrusion into our buildings because we have water a lot of the time.  This area has been one of the live labs that ORNL has used for measuring different building constructions and how they fair in the elements.

Fast forward through a lot of testing, measuring, and plotting and today there is available software that will allow you to take a model of a construction, place it in a certain climate, expose it to chosen parameters for a set amount of years, and then see how it is expected to survive the conditions.  WUFI won’t definitively tell you your construction WILL definitely fail, or survive, but rather that there is the potential (strong or not depending upon the results) of what you can expect.  As always, your model is only as good as the information you put into it, and your actual building can only be expected to perform similarly if it is built to the same specifications and subjected to the those same historical conditions without additional issues like leaks.  More than anything, WUFI is a tool to let you know how close to disaster you might be getting and give you an opportunity to correct the design before the building is under construction.

This series is not going to go through all the constructions or issues a project could be faced with, but rather how to begin using the free WUFI software and what information is needed on each screen in order to run a calculation.  The free version of WUFI does have limitations – you can’t add new materials to the database, but you can learn the principles of how this science can be used to design better constructions.  The free version is for educational purposes only and should not be used to definitively state the expected condition of a construction for commercial purposes.  You will be taking the responsibility for those results if you do.  There is a commercial version available for that purpose and that will also allow you to add additional materials so that your project is modeled as accurately as possible.  Any results that are displayed by the software need to be analyzed by someone familiar with the science so that the results are as useful as possible to the project.  I will go into basic analysis interpretations, but I am not a scientist, nor do I play one on the internet, but I do like blogging about it! 

To start, let me make sure you know how to get a copy of the software and install it so that you can follow along.  This is the link to the Oak Ridge National Labs website where you can find the download.  http://www.ornl.gov/sci/ees/etsd/btric/wufi/ There is also a WUFI website that Fraunhofer IBP has set up that has additional information, a way to purchase the commercial version of the programs, as well as including a forum.  You can find that here: http://www.wufi.de/index_e.html If you are going to download the free version from ORNL, do that first before trying to sign up for the WUFI forum so that you have the serial number information you need to register for the forum (the forum is free). 

I will give you all a chance to get a copy of the software and install it.  If you have any problems with the installation, you can review the WUFI forum postings on installation issues here: http://www.wufi-forum.com/viewforum.php?f=11 Additionally, you can comment on this blog or contact me directly and I will help you sort out the issues. Linda@SmallPlanetWorkshop.com

Up Next: Getting started with WUFI

Putting Passive House to the Test! Pt. 33 - PE

There are a lot of ways to design a Passive House and certainly there are some that are easier than others.  When it comes to Physics though, you just can’t change the rules (though the vacuum panels let me bend them a little to meet the Heating Load requirement!)

The Primary Energy value, however was not as forgiving.  That takes all the energy required for heating, cooling, DHW, and daily electrical use and limits it to 120kwh/m2a.  My project has a set amount of needs, and when I cram those needs into less and less space, the values don’t always meet the Passive House goal (though if it were 200sf larger it would have met it handily!) 

One of the issues with any construction is going to be the Domestic Hot Water supply.  Even if you build as efficiently as you can, as air tight, as insulated, you are still going to have hot water requirements that are set by the amount of people who will be living in the dwelling. That value is fairly static and not too dependent on the size of the dwelling (if the plumbing is efficiently placed without long runs), yet it gets lumped in with the PE value based on the square footage of the house. 

A small place like the bunkhouse has very small plumbing runs, but there is still a set amount of hot water that 2 people need to wash dishes, shower, and other items whether they live in 260sf or 460sf.  The extra 200sf made the difference not only with the DHW, but also the heating loads and the Bunkhouse may have made PH if it were larger, but I wasn’t building a huge trailer.  Though now that I think of it, this could work nicely on a mobile home which can be wider and larger! 

Was the Bunkhouse still a good project?  Oh yes!  Anything built to be more energy efficient than it normally would be is an improvement.  I could use the concepts of Passive House to increase the energy efficiency of a project like that even if it didn’t meet the PH requirements.  Did I learn anything from it?  I sure did.  The most important thing I learned is that I could really think outside the box and come up with the exoskeleton idea.  Remember I am not an architect or a designer.  I was able to take the essence of the Passive House concept and apply it to a problem and come up with a rather innovative (for me) solution.

This was a fun project to work on.  I’m sorry it won’t get built specifically as a Passive House project, but if I do build it, I know it will be a lot more energy efficient than I could have designed if I had not known about Passive House!  As for the other outbuildings I wanted to build and test for moisture migration as part of putting Passive House to the Test!, I have had to place that part of the project on indefinite hold.  Between a broken water line and a few other homeowner headaches I’ve had a bit of extra work on my hands and won’t be able to get to that.

If you have any Passive House questions or ideas for future blog articles, please contact me at Linda@SmallPlanetWorkshop.com and let me know what You would like to know about.

Putting Passive House to the Test! Pt. 32 - The Nerd Numbers

After making the Heating Load requirement numbers work last week I crunched a few tentative numbers and discovered that the price to build the Bunkhouse as I designed it to meet Passive House so far was going to be more than I have to spend, which is not always the case with a Passive House project - many come in as cheap or almost as cheap as non-passive house projects.  My project has limitations that a lot of projects don't have - regular house projects aren't limited to sizes that are able to travel on the road!  However I am so glad I made the effort to see if I could make the numbers work and in the process learned so much more about Passive House and the PHPP.  I still have to see if I can make the Primary Energy numbers meet Passive House, but for now that is just going to be an exercise - I already know I can't afford this particular project to be built as designed.

First, the nerd numbers so far that I am sure a lot of people want to know about.  How thick are the walls, and what are their R values.  For the combination of cork and vacuum panel insulation alone the walls are 7” thick and have an approximate R value of 68.  The Ceiling insulation is 11” thick with an approximate R value of 124.  The floor insulation is 9” thick with an approximate R value of 114.  These numbers don’t include any of the metal exoskeleton or plywood. 

Because I am limited to how wide the project could go, I knew that to get the R values necessary to make it work to the Passive House standard I would need to go with the vacuum panels or lose too much interior space to the thickness other insulation would have required.  When I crunched the prices for the vacuum panels I found the floor panels alone would run about $13k and that didn’t include installation or the cork and plywood that would also be needed.  Toss in all the rest of the expenses (as well as the walls and ceiling) and I knew I would be way over budget.

Since the concept of Passive House is to build affordably as well as energy efficiently, this project is not the type of project that makes the best use of the science.  Larger projects, especially multi-family projects make much more sense and are far more affordable to build.  I learned from the mental exercise I had to go through to make the project meet the Heating Load requirement just how the PHPP was able to show me where I needed to focus to increase the efficiency of what I was doing.  I now have a better understanding of designing a project and that is something that you can’t get just by reading a book about it – you really need to design a project and put it into the PHPP, even if you don’t end up building it yourself.

So, what did the project end up looking like?  I was surprised when I added the windows to see how small they looked when drawn to scale.  For a trailer they were nice sized windows, some being 2’x3’.  The smallest being 1sf.  I had recently seen a very large RV with a wild swirling paint job on it and wondered why they would do that.  After seeing what my plans look like with plain walls I imagine it could be to take the focus off of how small the windows are and how much room you will have inside their huge RV.  I’ll have to make a point to look at how big their windows are next time I see one!  For the Bunkhouse, here is where the plan is today: 

So that's the Bunkhouse as I designed it.  I'd love to hear your thoughts on the project and the series that I've written describing it.  

Up Next - Would the Bunkhouse have made the Passive House PE requirement?

If you have any Passive House questions or ideas for future blog articles, please contact me at Linda@SmallPlanetWorkshop.com and let me know what You would like to know about.