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.

Let’s start by understanding what the Annual Heating Demand and Monthly Method worksheets are for.  These worksheets are both designed to meet the EN 13790 method of calculating the heating demand for your project.  The PHPP manual states that both methods give similar results with the Monthly method being more accurate, but the Annual method easier to understand.  I found I used the information on both worksheets to help me understand the project.  Only one can be chosen as the basis of the heating demand calculation for the PHPP (and this is done on the Verification worksheet), but you can still look at the graphs on both the Annual Heating Demand and Monthly method worksheets to help you understand what is going on. 

Here are the charts I ended up with after I threw lots of money at the project and met the Heating Load requirement: 

You will see that the Annual Heating Demand chart shows where I can expect to see the heating gains and losses and at what percent.  This helped me decide between more insulation and changing window sizes.  The Monthly Method chart showed me how much free heat I could expect each month and also showed me when I could expect overheating.  The Blue line on that worksheet shows me what my losses are for each month, but not where specifically I am losing the most heat.  That’s why I used both charts.  By looking at both charts I could see how changing the window sizes would affect both overheating and heating.  I could see how adding insulation affected the heating demand on both charts as well, but the Annual Heating demand sheet broke down the difference between the losses from the walls and those from the ceiling/floor areas so I was able to target where the additional insulation would do the most good.

Because the PHPP mentions that the Monthly Method was harder to understand I decided to see if changing the chart slightly would help me see it better and I found that I like it this way.  (I didn't change it in the PHPP, I just made one by hand).  I put the Solar and Internal Heat Gains on the bottom of the chart (in yellow) since I knew I automatically had those.  Then I placed the Heat Demand (in red) above those to show what I would need to make up for the additional losses that I could expect (the blue line).  I also added an area that shows overheating more clearly for the summer months (yellow with red cross hatch).  June and September are actually special cases with free heat, heat needed, and over heating all in the same month.  By color coding these charts and studying them you can really get an understanding of your project.

So, technically I was able to get past the first hurdle and meet the Heating Load requirement on paper.  But what does the Bunkhouse look like overall and close up?  Up next I will draw the bunkhouse to scale with the window sizes that worked and see if I can find out exactly how many gold bricks I would need for the vacuum panel insulation.  I’ll also pull together some PH nerd numbers for all the folks who are wondering about R values and TFA.

Up Next – Bunkhouse Nerd Numbers.

The closest ground category the PHPP has to “Cork House with Metal Exoskeleton Built On Top of a Metal Trailer” is “Suspended Floor”, so I will work with that.  At this point I am flying blind as far as what would actually be certified by PHI for this, so this blog post will serve as a learning tool for me and anyone else who isn’t sure what it is they know or don’t know about a PHPP worksheet. 

This I know - PHI is busy.  Incredibly busy.  I can’t email them and say “I’ve got a weird project and it doesn’t fit your PHPP, what do I do?”  I need to understand what the worksheet is looking for and why.  Then I need to figure out how my project fits into that format and how to get the information I need to fill in the blanks.  When I have done all that and STILL have a question… I ask another CPHC.  Seriously.  

We need to interact with the folks in our community that are working the very same problems we are.  As we get to know each other, our strengths shine and we find those who can help us or they find us so we can help them.  That’s what I did with my window Psi G problem.  When I heard that my go-to window gal, Bronwyn was going to talk to PHI about the very same issue, I didn’t bother them.  She’ll figure it out, I’ll learn from her, y’all will hear from me. 

So, let’s look at the Ground Worksheet and see what I know and where I get stuck.  The first thing the PHPP is looking for is the Heat Conductivity and Heat Capacity of the soil.  My first thought was that it would be irrelevant since my project does not technically sit on the soil.  But, using my earlier statement, I need to find out what the worksheet is looking for and why.  The PHPP tells me that “The ground surface temperature rises and falls over time as a sine wave that has an amplitude approximately half the difference between the maximum and minimum monthly average ambient temperatures.” [PHPP 2012 pg 60]  In other words the air could fluctuate from an average 30degF at night to an average 50degF during the day for the month of April – a fluctuation of 20 deg on average, but the ground temps may only fluctuate about 10 deg on average for that area during the same period.  Tying your building to the ground is better than putting it on top of a steel trailer.  However, that steel trailer will sit on the ground and perhaps the ground will transfer heat to the trailer through radiation so I still need to consider this information in my PHPP.  The kind of soil I have happens to be the default, so that is already filled in for me.  Check the PHPP manual for the soil values that your project has. 

Under “Building Data” the worksheet wants to know the slab area, how much of the perimeter of that slab is exposed to the air, and what the U value of that slab is.  Since my entire Bunkhouse is exposed to the air, I listed the full area of the floor and perimeter.  I used the U value of my floor assembly which includes a steel layer for the trailer and a mesh rodent barrier. 

My floor slab type is “Suspended Floor” so I check that box and move to the area where I enter the “Suspended Floor” technical details.  This is where I once again need to pay attention to what the PHPP is looking for.  The Ucrawl is asking for the U value of the ground surface.  If it is insulated you would use that value, if not, the PHPP says 5.9 W/(m2K) is used.  For my calculation at this point I will assume that I am parking the Bunkhouse over bare ground. 

Next the PHPP wants to know how tall the Crawl Space Wall is.  Technically I don’t have one of those, but the trailer bed is 2’ off the ground so I will use that value as an “imaginary wall”.  I see the next field wants a Uvalue for my imaginary wall followed by a field that wants to know how big the ventilation holes are.  I see a loophole here!  I put in a ventilation value that is 100% equal to the size of the wall that the PHPP is expecting to see.  I test this out by changing the Uvalue of my imaginary wall from 900 to .9 and it does not affect the final numbers.  If I remove the ventilation numbers, the Uvalue numbers for the imaginary wall now make a difference, so I quickly put the 100% ventilation value back in.  

The Additional Thermal Bridge losses at Perimeter are not relevant since the metal is outside my Thermal Envelope.  I’m not worried about the ground water issue, so I am done.  That was practically painless and I didn't need to check with PHI after all.  I do know that PHI will go over this sheet with a fine tooth comb if I end up going for certification and they may question what I have done and make some adjustments, but I am feeling pretty confident.  I also feel like there could possibly be the potential to come back and add an insulated skirt to the Bunkhouse so that I have some benefit of a crawlspace if I need to.  I might look at that in the future.

Since I didn’t get to the Annual Heating Demand and Monthly Method sheets this time, I will look at those next week.

This past week I attended a conference on ventilation that the wonderful folks at Walsh Construction and Passive House Northwest put on.  They brought John Straube of the Building Science Corporation to speak to us about Mechanical Systems for Low Load Buildings.

The place was packed with people interested in hearing one the of the premier voices in Building Science address the questions and concerns that we in the Passive House community have regarding Mechanical Systems.  The surprise to me was that the emphasis he saw in these buildings needs to be placed on Domestic Hot Water as a primary concern.  By building the envelope tight and insulating well we are keeping our heat demand down, but we still need our water heated and that will end up being a higher percentage of energy usage than our heating demand.  Thus John covered quite a bit of ground on heating water, using it in home energy heating, but ultimately said that there is no one single solution for all the demands that are expected of an HVAC system.  

John said that basically we look to HVAC to provide Ventilation, Heating, Cooling, Humidity Control, and Air Filtration.  We need something that will give us fresh air while keeping us at just the right temperature without the air being too dry, too moist, or full of junk like pollens and odors.  If you’ve got the $$$ you can plan a fabulous system that will do just that, but for the rest of us with a lot less $ we have to decide where the priority is and sometimes that comes down to comparing the cost of a more expensive system vs what insulation we won't need to put in, or is the more efficient system saving more money in utility bills than the extra it cost to purchase?

Generally, for this area, we are blessed with having such a mild climate that we don’t have the crushing summer humidity of the East Coast, or the daunting temperatures of Anchorage or Phoenix.  In our climate there are times we can get away with something less efficient and save money rather than purchasing the more expensive unit that is top of the line, but we need to understand, especially in the Passive House community, what that means for our project in terms of energy use, mechanical ventilation, and certification.  If your goal is to meet Passive House certification, then you may need a more expensive unit to get to that level.  If so, look for the ways that you can offset that cost.

I have been keenly interested in the Lunos e2 HRV that the guys over at FourSevenFive.com sell to solve my ventilation needs in the Bunkhouse.  It handles smaller volume buildings, which the Bunkhouse definitely is, and it does not require ducting.  I will need to plan the fresh air supply carefully since it is a small building and will be built to the PH level of airtightness.  Finally, because I am trying to meet PH requirements and get certified, I do want to pay close attention to how the unit will perform in the PHPP.  Fortunately for me, the 475 guys have published an article on how to insert the numbers into the PHPP.  That’s service that brings a smile, eh?

One last item that I am interested in specifically for my project - the humidity levels at the lake are really quite high, so dehumidification will be a concern.  During the conference John Straube mentioned that the best course of action could be to separate the humidity issue from the rest of the goals for the HVAC system and deal with that separately.  I think that sounds like a great idea for my project since I am really limited to what kinds of small HRV’s and ERV’s are available.  I’ll address the dehumidification separately and see what creative ideas I can come up with.

Up Next - Looking at the Heating Demand and Heating Load in the PHPP

As I have mentioned, my lot is practically in a temperate rainforest.  That means I have ginormous evergreen trees almost everywhere.  There are a few places where the trees were removed on my lot for the old mobile home.  My neighbor to the west has a cleared section that lines up with mine, so I do get afternoon sun.  This will need to be accounted for in case the western facing windows allow too much solar heat gain.  It’s possible I could even end up having to ADD shading to that side of the bunkhouse! 

One thing you need to realize is that the shading aspects of your lot, both during the winter (buildings, coniferous trees, other permanent objects) and during the summer (deciduous bushes and trees, summer awnings, other shading devices) need to be accounted for because the amount of solar heat they let in or keep out is monitored closely for effective PHPP calculations.  Even if you had a site with no shading you would still need to calculate the shading aspects that the window placement in the walls have.  The PHPP is that picky (and for good reason).

Here is a picture you may have seen me use in other articles on shading.  I love it because it represents all the different ways the PHPP looks at shading (though the “r other” shading example in the picture is rather weak it should still remind you to look for those examples as well.)  The shading aspects that are in place year round will be listed on the Shading worksheet and those that are only an issue in the summer will be listed on the Shading-S worksheet.

Up Next - Ventilation

I must add, that even though I now have Zola’s Psi G and Psi default install figures for a variety of windows, PHI will still need to approve the figures if I use them in my project.  At issue will be things like how Zola arrived at those figures, which testing protocol they used, what sizes of windows were tested, what types of install measurements and materials were used.  This is not something that Zola alone needs to square away with PHI, it is something any non-PHI certified component manufacturer needs to address in order for their product to be included in a PHI certified project.  As for my project, the Psi install will need to be revisited even if I go with a certified component since I am planning a rather unusual wall assembly.

So how do we get North American products to be included in the PHPP?  Those manufacturers will need to understand the importance of having their products certified and that the benefits will include consultants having an easier time choosing products to help them meet their project certification goals.  Last year Bronwyn Barry worked with PHI to arrange a workshop for window manufacturers in the US so they could learn more about Passive House and what they need to do with their products to make them more energy efficient.  The dialogue has started and it will take time, but we’ll get there as folks begin to understand the Passive House concepts and see the projects that the first wave of Passive House folks are putting on the market.

I know I had a fun time at the PHNW conference mentioning to all the window reps that I was trying to design a Passive House travel trailer.  It caught them off guard and yet they wanted to know more.  I still don’t know if the project will make certification, though I do know it will be extremely energy efficient even if it doesn’t.  What’s important is to think of ways we can save that energy and live a cleaner life in the process.  For me it is also “Can I solve this puzzle?”  I love me a good puzzle!

Up Next: Shading

I understand the concept as laid out by Benjamin Krick of PHI in my previous blog posting "The ABC's of the PHPP - Part 4B Psi-lence of the Jambs", but I found that having all the bits to do the calculations was more difficult than I thought.  The Zola Windows website plainly says that they will be happy to assist with any information necessary to enter their windows into the PHPP, but I wanted to see if I could do it with just the information I found online.  Unfortunately I didn't realize all the information I would need to have until I started working on the THERM model.

 Here is where I had problems. PHI combines a calibration panel with a known window frame and then they run a THERM calc on the assembly.  I had a CAD drawing of the window frame I wanted to use, but I did not have the u values of the materials involved since some are proprietary.  I did have the overall u-value of the frame as tested by Zola, but I quickly found that using that as a generic value for a material I called the frame didn’t work.  I began to feel I was cutting too many corners and making too many assumptions so I stopped.  As the old saying goes, “Garbage In, Garbage Out!”

During this exercise I contacted my Window Guru, Bronwyn Barry, and found she is dealing with the exact same issue with another window manufacturer’s window.  She will be personally working with PHI on that (and then can teach me!), so I have decided to follow the other path and ask Zola for assistance to see what kind of information they have that I could use and report back what that was like.  There is nothing like a good learning experience to get a blogger excited. 

If I did have all the materials and could have modeled them in THERM I am fairly confident I could have come up with a value that would have been a good guess placeholder.  Even if it were right on the money, the big issue with windows that are not PHI certified is that PHI will not automatically accept the window manufacturers testing information.  PHI will make the final decision of just what you are allowed to enter in the PHPP.

Still, at some point we need to have a method that we can plug numbers into and get values out of easily, so this issue will definitely be revisited.  In the meantime, I will see what the manufacturer has to say and report back. 

Up Next – talking to Zola about their product and the PHPP.

I chose to use the Zola Window information for this exercise because their brochure included the necessary values that we will need to fill in the glazing and frame information  in the PHPP and run the Psi calculations in the next blog installment.  If the brochures or website for the windows you are interested in do not have the specific information, ask the company.  

First, let me run through the very quick and basic explanation of COG (center of glass) and EG (edge of glass) as it is used in ASHRAE and ISO calcs to figure out the Ug value (U value of the glazing).  ASHRAE divides the window into areas where the spacer affects the Uvalue of the glazing (Ueg – the outer 2.5 inches of glazing) and areas that are not affected by the spacer (Ucog – glazing not in the outer 2.5 inches).  ISO doesn’t use this edge of glass region separation in their calculation, and instead looks at how the spacer affects the glazing in a linear way along the edge intersection of the glazing and the spacer.  Here are the two formulas that I found in a 2007 LBNL report on State-of-the-Art Highly Insulating Window Frames – Research and Market Review 

If you need to give your inner window geek a thrill, the report has much more detail on these equations that you can check out in section 2.1 Thermal Transmittance (U-Value) which starts on page 8.

So, for entering the glazing of a window we use the center of glass u value to enter into the Win Type worksheet as well as the SHGC value which is equivalent to the G value that Europe uses.

To enter the Frame information on the Windows worksheet, we need the U value of the frame (Uf) and NOT the U value of the entire window assembly (Uw).  This is where you will need to be careful with what information you are looking at.  Full Frame or Overall window performance are the Uw and include the glass U value in its calculation.  If you notice in the above example, the glass has the best U value, the frame the worst, and the total assembly falls somewhere in between.  This is why you need to make sure you are looking at the U of just the frame and not the entire window - inputting the total window U value instead of the frame u value will give you a too good result in your PHPP.  Ultimately this will get caught - best to look out for it before it means your project doesn't get certified!

This gives us most of the information that we need to enter a non-PH certified window into the PHPP.  We still need to calculate the Psi G and the Psi Install.  I covered the general information of how to do this in a previous article called “The ABC’s of the PHPP – Pt 4b The Psi-lence of the Jambs” Next I will use this window information and do those calculations.

Up next – taking non-certified PH window information and determining Psi G and Psi Install values

This week I researched the suspended film technology question a bit more and compared the windows I saw at the PHNW conference last week.  I also came up with the corniest clipart pic for "Window Film" - my kids always tell me not to do art.  I think they might be right.

Starting with the suspended film issue.  Evidently this was a technology that several manufacturers tried about 15 or 20 years ago and the failure rate was unacceptable.  Alpen has been working with this technology for quite some time and offer a lifetime guarantee on their high performance residential windows for the original owner if they continue to own and reside in the home.  They have lesser 5 & 10 year warranties for other situations.  Alex Wilson over at the Green Building Advisor is using Alpen for his project and says "I’ve known Robert and his company (Alpen) for many years. He and Alpen have been the leaders with high-performance windows in the U.S. since way back in the mid-1970s, consistently way ahead of the curve in introducing new technologies." 

Short of getting into the lab and doing some testing myself (after getting that all important window guru degree so I know what I am doing in the window testing lab!) I think I will go with the reassurance that customers have relied on for a vast array of purchases - is it a known company, do they have a reasonable warranty, are their reliable reviews of their products and customer service department, are the advantages of why I am considering them enough to warrant giving them a try rather than another manufacturer?  From Refrigerators to TV’s we don’t know the science or performance of new to us technologies but we occasionally venture beyond a known name or technology and try something new because it seems reasonable.  At this point I will say that for me having the Alpen warranty and experience with the suspended films is enough for me to keep them in the running for my project.  

So let’s see how the windows I looked at during the conference stacked up.  The window reps I spoke with were from Alpen, Cascadia, Euroline, Unilux, Yaro, and Zola.  Because there are 3 main variables to consider (SHGC, U value, and Vt) it is hard to make a chart and say “Aha!  This is THE definitive Passive House window” because the variables can work against each other.  The trick is to find the right combination that gives you the best performance for your particular situation.

While researching this article I found a great comment that Martin Holladay made on a thread at the Green Building Advisor website “The holy grail window for south elevations in northern climates is a magic window with a very low U-factor, a very high SHGC, and a very high VT. That magic window doesn't exist, so we all have to choose the specs of our windows based on a series of compromises.”

Using Martin’s Magic Window for South Elevations in Northern Climates I found a few window packages that I could be interested in.  Only two manufacturers had information easily available for the three different variables I was looking for, though most had 2.  Given that, I was able to choose a few models to put into the PHPP.  Alpen, and Zola each had something I could tell was in range, I need a Vt number from Yaro.  I am going to contact Cascadia for some more information because it appears their Ug values are not for COG.  I know they have had windows used in Passive House projects (including the Seattle Passive House that Dan Whitmore built) and I want to make sure that I have the correct information for them.

Up next - adding manufacturer’s window information into the PHPP

I spoke with each of the vendors, and with the exception of one, found some options to consider.  Hannes Hasse of H&H Windows was quick to point out that their all wood windows and doors would most likely not be the best fit for my project due to the way the material would react with the movement I could expect the Passive Bunkhouse to experience.  I really appreciated his expert opinion.  He had gorgeous windows and doors and I will definitely consider his product again if I plan a regular Passive House.  Bonus - H&H Windows are manufactured in Seattle.

The other vendors all had some product line that they felt would be beneficial for my project.  I made notes and gathered up the brochures.  Now to sort through it all!  There were immeditately two different ways I could classify the windows apart from performance.  One manufacturer, Alpen, had a triple glazed option that included 2 suspended films instead of a third pane of glass.  This allowed for a lighter and thinner product.  The other manufacturers offered only 3 panes of glass for their products.  When asked if they had a line with the suspended film I usually received an answer that it was not reliable.  As these windows will get some movement I want to do a bit more research into this area before deciding for or against suspended film.

The other way that I could compare the products would be from where they are being shipped from.  Alpen said their product shipped from Colorado, Cascadia is a Canadian company, and the other manufacturers were located in Europe.  There are those who have crunched the numbers for carbon footprint and found that the carbon impact of distance can be mitigated by the type of travel used for the shipment (boat verses semi-truck).  The other concern with distance is replacement parts or service could have an extended time attached to it.  Zola pointed out that they only sold windows by container full, though I could share a container with another project and have my windows shipped with them.  Things like this need to be taken into consideration when planning the construction schedule as well. 

I need to list out all the window options in terms of U value, SHGC, and Vt.  That will definitely drive the decision as to which way I want to go with the windows.  I do find the Alpen windows appealing both from a lightweight and thinner perspective, but want to look more into the reliability issue of that method.

Up Next – comparing the performance numbers and researching the suspended film issue.