Kevin Derheimer wrote:I recently built a passive house and dealt with extreme air sealing. I used zip system on the ceilings, it's osb with a green air barrier on one side that would go on the room side. You then use their special tape to seal the seams. I ran 2x2 furring strips on top of zip system to attach either t&g aspen or drywall. Electrical goes in the 2x2 gap, ceiling electrical boxes fit in this gap. Any penetration was sealed with prosoco joint and seam filler. I did blower door test and got to 0.7 ACH on the first pass. This method has been used many times on passive houses and really works. Certainly not the cheapest, but mine with 21+" of insulation gave me around R96, and no air leaks.
Kevin Derheimer wrote: The house is the most comfortable I have ever been in! I did the passive house training a couple of years ago and have been studying methods and materials since. It's tough to find materials that do the job that are not either offgassing or environmentally detrimental. The passive house group does not like spray foam because of the nasty blowing agents. Air sealing tapes or wet flashing products are standard. Foam, by the way, is not considered an effective air seal. Plywood and osb are not air tight also, I talked to a guy who used unfaced osb and couldn't get good blower door results, he found air was traveling through the osb, I used foam backer rod and prosoco air dam to seal around Windows. I installed Viega radiant heat system myself as well as the Zhender erv. 14" walls, 8" geofoam under slab, 6" geofoam under footers, 4" external wall foam to move dew point out of wall cavity to eliminate chance of condensation in cellulose. I have hydro shark 10 heating house till I get solar thermal going, boiler core is the size of a beer can. This is the first winter and the house performed better than I ever expected.
Terry Ruth wrote:Sealing a Passivhaus (Germany) building's is entirely different than US (PHIUS) like apples and oranges different you can see in the WUFI models with regard to air flow & material mold. That is why PHIUS now exist, they disagreed and got a divorce in 2013. If one does not understand the difference it is dangerous, deadly, sealing in a sick home that an HRV/ERV won't cure. Just when you thought everything was comfortable and fine, well think again!!
Kevin Derheimer wrote:Hi terry, I did my training with phius in 2013 and am familiar with the "divorce". I understood it to be about treating different climate zones differently, not just using northern Germany as the base model. Your point is well taken, I modeled my design using climate data for my city and ran 10 year simulations on walls and ceiling. That is when I had my "aha" moment in regards to dew point. With no foam on the exterior I was showing a good deal of moisture accumulation in the dense pack cellulose, which means mold and rot! 4" of external foam moved the dew point out of the wall cavity into the foam and the simulation showed no moisture accumulation over the 10 years.
In the training, we looked at several passive house failures, and I have since studied more of the building science. There are some critical things that most people miss or don't give enough attention to, like interior wall finishings. There was a single sentence in the training material that stated you could have only 3 coats of pain, ever! So 1 coat of primer and 2 finish coats is all you get, not very realistic in my opinion. That, surprisingly enough, didn't bother anyone but me! If the wall dries to the inside, and you seal the surface with too much paint, you get a vapor sandwich, which again means mold and rot. I decided to use American clay on most of the walls because it is very permiable and moisture regulating. Primers and paint were a different story, I spent months talking to all of the paint manufacturers about permeability of their paints and primers. I found nearly all had perm rating of 4 or less, compared to around 45 for drywall. (It was interesting that the paint mfgs were not asked about perm rating much). I found a primer (Roma) that could be tinted and used as final coat, and with sand added, was acceptable for primer for the clay. I think at this point, I think I have done a pretty decent job with addressing the building science part of the project. As they say, the devil is in the details, and time will tell.
Terry, forgot to answer the net zero part. Net zero would be great, but not required. There is a tab in phpp where you enter electrical usage, it forces you to consider all proposed electrical appliances. The idea is to reduce primary energy, or energy generated at a power plant. You get immediate feedback on energy choices and can get info on the carbon footprint relating to your choices. In my experience, it really forces you to consider electrical Usage.
I chose surface mount ceiling lights, and 1.5" metal boxes in mechanical space. Ceiling is zip system with 2x2 furing strips, then drywall or natural t&g aspen. All lights are led or led capable.
I ran the simulations in an older version of wufi from oak ridge national labs.
Terry, Wow, I loved joe's article! I can't believe they actually printed the part about "coefficients" and "guesses", LOL! I've said that to people before but everyone just thought I was crazy! So, now I'm wondering if the wufi software I used took some of the different transport mechanisms into considerations.
In the pics of my simulations there is moisture shown in the OSB layer behind the foam but it did not transfer into the interior insulation. I could not explain why this would show up, now it makes more sense.
Ok, The difference between layered materials and monolithic in terms of moisture transport (in any phase) makes a great deal of sense. It sounds like newer wufi software may handle this better, makes me want to re-simulate with newer software. I did not realize that the software was ignoring the more difficult transport mechanisms, troubling to me that it was not disclosed. I'm not sure it would matter to most people though, I know maybe 2 people who would enjoy that article as much as me.
I’m not sure WUFI handles PCMs at all or the massive amounts of bacteria and fungi families always being found.
I knew fiberglass has lower than stated r-value when installed poorly. This now makes more sense on several levels. I assumed it was just because of air intrusion (air flow in wall cavity). This article is awesome because it's making me rethink my reasons for different designs. I would like to see the BSC report, do you have the link?
I have been preoccupied with eliminating thermal bridging to eliminate condensation possibility (rot and mold possibility), the idea of galvanic chemical or physical reactions between layers that would promote microbial growth is both exciting and daunting. Do you have any examples of this?
I have looked at phase change drywall, looking forward to seeing field trials. Makes me think of the moisture regulating properties of natural clay finishes. I'm sitting here shaking my head thinking that we don't even know what we don't know.
My next question for you would be what would your optimum wall look like?
yes, I see the differences in how Germany and the US deal with building science.
I have seen the part dealing with rain, that was the main reason I implemented a rain-screen to break possible capillary transfer between cladding and underlying materials.
In the simulation, I used polyiso, but after discussing its possible long term r-value degredation with an older cold room builder, I chose xps. Possible problems with polyiso may be due to moisture phase changes inside the insulation.
Since any foam is a vapor barrier it will not handle phase change well. A PCM would much more efficient. I do not think there is a lot of quantified data for natural builders to use, although Staube and some others like ORNL, ASHRAE, are developing them. One thing good about WUFI Plus is one can define thier own materials properties and assign and benefit.
I haven't seen an explanation for why polyiso may degrade.
I read it outgases some claim for a short time after manufacture others say longer. I personally stay away from foams, too much controversy. About the only place toxic materials are acceptable to me is surrounded by an air stream.
Under my cladding (cedar and stone over durarock), I used wrapshield SA over edges of z-joists to prevent moisture transport into the wood. I am taking for granted that the materials I picked to either prevent or direct moisture transport will perform as advertised.
I have been trying to get the architect to use BIM, but he still uses autocad and sketchup. I took the time to learn revit and love it. After using it, I can't see why designers wont use BIM. I have PDF's of plans.
I am currently working on the calculations for a 4K+ square foot house in Durango.
Terry Ruth wrote:Kevin, you still out there? I’ve been helping with a plaster job over in China and learning how to better communicate on forums. The later being more of a challenge.
I hope we can agree it should be obvious by the data as in electrical and HVAC loads new building’s are producing we are on the right track air sealing but, let’s not misunderstand what is meant by it. Unless we live in the tropics we certainly do not want big holes around fenestrations or in walls leaking cold weather in or conditioned air out. In open flow wall cavities we do not want moist convective air loops degrading r-values. In ventilation channels such as cladding we need high flow and little resistance due to air leaks at boundary layers. PCM’s(Phase Change Materials) we do not want air or vapor barriers. So we are talking several different modes of air transports aside from vapor modes of transport.
. I'm still bating around if I will completely ignore all these certifications or obtain them for third party bragging rights after I build, prove, and test the design. I'm more interested in the IAQ than anything since I am sure that is where most fail.
reduce penetrations I don’t use any can lights, I hang all my interior lights so I only have a romex wire penetration in my ceiling’s….all integrated LED fixtures, the light last as long as the fixtures and produce low e-loads. Continuous nner boundary layer wall/ceiling air sealing planes provides a nice place to deal with penetrations especially if self-sealing plastering. Not clear on your layering I'd need to see a drawing. I like the word furring strip as in cladding ventilation gap or rain screen much better than house wrap. I have no house wrap in my designs.
The blown cellulose industry took this test and ran with advertising it stating the HD packed wall cavity has lower flow than fiberglass. Many do not want to look at the other elements that promote microbial growths such as the food in blowing agents and fire retardants. If it is not inert, look at what it reacts to. If one does not know do not use it. I like mineral wool but care must be taken with it too. http://buildingscience.com/document-search search " thermal metrics"
Do you have a 3D model of this? What simulation software for HVAC and electrical loads are you going to use for it? I thought everyone is getting away from PHPP and using PHPPUS or better now PHIUS_WUFI Passive?
I found a company called Cetco, that specializes in foundation sealing and soil gas mitigation for brownfield building sites. They have a product called geo-vent, its 12"wide, 1" thick, comes in a roll, has geofabric cover, and airspace inside. You install in a continuous loop under the foundation. They have a transition fitting to go from the geo-vent to 2" pvc that I sleeved through footer and ran to perimeter drain which ran to daylight far from house. The idea is to provide a passive channel for the radon to escape before it builds enough pressure to enter the structure through the slab. It cost less that $200 to install, local contractors loved the idea so much that they are now using it as well. You could do the same thing with corrugated drain pipe, may be close or cheaper in price, but probably a lot more difficult to install.
I did use heavier moisture barrier under the slab, wet flashed and taped. I would think anyone building a tight house, natural building material or not, would be smart to deal with radon mitigation before construction.
Link to the geovent - http://www.cetco.com/DesktopModules/Bring2mind/DMX/Download.aspx?Command=Core_Download&PortalId=0&EntryId=104
Yes, me as well, my problem is that customers look for the certifications even if you have no idea what you are doing. So I have been working on getting them to appease customers. My experience is that in 5 to 10 minutes, you can see who has a good understanding of underlying principles, and who is blowing smoke.
From what I can tell from little info I could find is this is a ventilation channel that comes in a roll that acts like a rubble trench with plumbing to attempt to move gases out of the building's IAQ. In theory there has to be a low pressure area around it from high air flow, or, enough ground pressures to produce flow to it, so that gases are sucked into the perforated rolled out channel then out vent pipes. I would think to get this to work would take more than just laying this product down, it would take an engineered understanding of the gases, pressures, and flows. I'm not sure I lay my life on the line for it. I could not find any proven designs over a long term field test could you?
This is interesting though since I think VOCS are becoming as much of a concern as radon in soils as we better understand what is causing poor IAQ and lung cancers. Back in the day the concern was what ground contaminates where leaching into drinking water, not into our buildings. What is as much or more of a concerns is natural building methods that surrounds themselves with walls and roofs not knowing. I know there is a big effort to try and solve brownfield issues and building IAQ by more natural eco remediation's and materials, not just vapor barriers and ventilation channels. There are some reports on the internet showing that it is not just a matter of shoving some top soils into an earth bag, or brick, or in form work, no more than it is layered manufactured products without an understanding of the mating reactions.
I think this product has a better chance when used in conjunction with air and vapor barriers. They do have issues as you noted since once a puncture occurs the flow to the low pressure area will be higher than over the entire barrier in many cases. In other words, a punctured air/vapor plastic barrier is worse than no barrier.
I dunno, after I see a radon and soil test I would then decide it I were going to even build on the site and/or hire the required professionals.
I think the only rating that matters right now is the HERs, did you get that? Did you try and qualify your building for EEM's? Energy Efficient Mortgages, or Fed and State Tax breaks? Passive house is not being used as far as I know. It is too new to the USA. Energy Star has an IAQ not sure any bank or anyone is seeing the value in it yet. It's going to take educating clients on some of the sales hype builders have achieved in the past like LEED certified sick building's. IMO the future in is IAQ. Perhaps a tuff sell to smokers but for the most part.
My understanding is that you don't need lower pressure to suck radon into the channel, the pressure in the soil Is relieved by the channel, so, theoretically, radon would never be able to reach a pressure level that would allow it to infiltrate the structure. I know "theoretically".
If you use a heavy, sealed vapor barrier, coupled with a system to allow soil gas pressure to escape, do you think a puncture would be worse? I'm thinking you would have air in the channels, as well as radon, since radon is heaver than air, wouldn't air be pulled into the structure rather than the heaver radon? If vapor movement was into the structure, air would be drawn back into the drain tube, and ultimately Into the structure. Voc's would be a different story, I would think their movement would be into the puncture first.
I talked to some guys that did radon testing and researched radon soil testing, and did not get a good feel that a radon soil test would accurately forecast potential long-term radon levels in a future structure.