As always the debate about how Permi foams are rages on. The only thing I would add for the lay person is that yes EPS foam is not "the best" foam product on the market, however it is depending on your perspective and use probably your best bang for the buck product on the market.
Looking at their construction video, the major thing I would do differently is I would probably spray foam the foam joints at the inside to ensure that there is a consistent vapor barrier on the inside of the envelop that will allow the wood studs to still somewhat dry to the outside of the wall if necessary.
My wife and I are looking at building a second home in San Diego and I'd like it to be a high efficiency envelope. I know the climate is really temperate and in the target zone for sure. I'm thinking that in that area with a proper passive solar design we could get away without any air conditioning or heating? What kind of insulation profile are we looking at for this area?
Topher Belknap wrote: and replied in green
2) Air sealing (especially if you plan to run your house at positive pressure) is important, as you don't want to be pumping warm moist air into your walls where it will condense, and encourage rot.
If your less permeable barrier is to the inside of the wall this should be a non issue. Walls should breath to the outside.
A low-permeability barrier is all well and good, in the appropriate climates. But a) It doesn't do anything to reduce infiltration through holes, which are the vast majority of the air sealing failures. b) It is usually not something homeowners of existing homes have a lot of control over. (or perhaps more accurately, want to take control of) c) Drying to the outside is no substitute for not letting moisture into the walls in the first place, d) Is not a good idea in certain climates.
Thank You Kindly,
Topher
Sealing a wall either from both sides equally or more to the outside is a bad idea all round. Summer humidity should be fine because you won't have a dew point for the moisture to become liquid inside the wall system you want a certain amount of "acclimatization" between your wall and the outside conditions. Where things go sideways is when you have a less permeable surface on the exterior that can get cold enough for interior humidity to condense against during the winter. Winter is where you get humidity condensing and rotting out the inside of your wall system.
Sealing up holes should have zero effect on this one way or another.
If the owner's issue is not enough insulation overall then they will want to address insulation for the entire envelope, however that looks. If there is enough insulation and its just air leakage through services, windows, doors etc then seal up the holes, its a no brainier. Purposely having air move unrestricted into the wall system from inside the house is your worst case scenario.
Topher Belknap wrote:
1) As others have said, insulation and air sealing is usually a better place to start.
Yes coupled with the addition of an HRV would also help keep things efficient, comfortable, and healthy
2) Air sealing (especially if you plan to run your house at positive pressure) is important, as you don't want to be pumping warm moist air into your walls where it will condense, and encourage rot.
If your less permeable barrier is to the inside of the wall this should be a non issue. Walls should breath to the outside.
4) Positive pressure is not a solution for infiltration. It just becomes exfiltration.
Indeed, why would you want your building to to do either?
5) You are going to want the woodstove when the sun isn't shining, so the solar heater won't be in service.
Yes, I've battled with this problem myself... How can I get solar gain at night? The only solution I know of is thermal mass (anti Knight flame suit on...)
Hey all I'm trying to source out some good information on shipping containers as homes. We are batting around the idea of a live/work multi family building from containers. Anyone have some good sources of info? Specifically we are looking at insulated units.
Essentially, my idea is to gut the inside of a house down to the bricks, apply an interior layer of earthen plaster over the exposed bricks, and then to bring the straw bales INSIDE of the house to use as interior insulation, which would then be finished in a final layer of interior earthen plaster.
What do you guys think?
Thanks
Hi Miles, welcome to Permies!
I hope your project succeeds! As much as I'd like to see Detroit reborn as an artist community, I'd much rather see it reborn as a hub of cold-climate alternative building.
I spend some time looking at houses in Detroit (as well as the rest of lower Michigan), so here are a couple of important factors for your plan:
First, it sounds like you might be picturing these houses as having load-bearing brick walls. Almost none of them do. That practice was pretty much over before Detroit's building boom, so they'll almost all be brick veneer over stud framing. Seriously, I'd bet that 96% of the brick houses in the city are brick veneer and 99.5% of the houses available for auction. That's going to change your approach- now you've got to cut a 1.5"x3.5" notch in your bales every sixteen inches for the studs OR leave a 3.5" gap between your bales and your bricks. Neither of these is desirable.
The other thing is that the $500 houses are mostly built before the era of open floorplans. Your contemporary tract houses, not such a big deal if your turn an 18'x 26' living room into a 16'x24' living room. Still fine. But you turn a 10'x12' room into a 8'x10' room, and you'll regret it.
If it were me, I'd be heading in the direction of doubling the studs and deciding how to insulate a twice-as-large-as-usual cavity, whether with slipstraw or rock wool or something else.
Good luck!
If this is the case then it will be hard to retrofit the structure to be more inline with a high performance envelope. Structural brick is a lot easier to work around than veneer.
You're probably not going to like this but the first decision you need to make about your project is: How will you quantify performance?
-energy efficiency?
-living space?
-useful space?
Buildings are very much machines, how they serve you is entirely up to you.
Dale I like the enthusiasm but I gotta say if there is one rule we've learned over the last 50 years of building it's that encasing bio matter in a plastic bag is a recipe for failure. Once moisture starts to get in either through wicking, ambient humidity or just leaking the wood will start to rot and once it starts rotting in those circumstances it goes fast.
I personally really like non organic foundations because they are far more resistant to water than wood or the like.
Think about it your putting wood in an open, upturned bag. So one crack in the wood post over time from drying or pressure and you have a place for water to run. Same theory as why cordwood walls fail with time.
Think of interior thermal mass as a thermal flywheel. So whatever inputs you put into it will be carried at a more moderate level over more time in a more consistent way. So thermal mass doesn't have much direct effect on energy input levels but it is vital for passive moderation temperature.
You can do cool things like run heating/cooling lines through TM and use it as an awesome radiant heat source as well as heat sink.
Only thing I would add to this is that the insulation value will drop considerable with time, so even if it isn't yet rotting it will be losing its ability to insulate quickly. Your basically starting on the back side of a bell curve as far as performance goes. Soo, in short order you will have lost much of the value and wasted a lot of time and energy even if it doesn't rot.
OK I'm going to inject some building science into this discussion.
1. Putting structural brick on the outside of a permeable and even an "impermeable" insulation material is not exactly wise. During cold times which do happen in Detroit you'll have a higher level of humidity inside the house than outside. As this humidity moves through the straw bale/slip it will come into contact with the much less permeable brick which also happens to offer a cold and comparatively impermeable surface. That surface is the perfect place for humidity to condense and turn to moisture/water. Water in a wall system means mold, mildew, rot and basic failure of the structure.
2. The brick is free thermal mass, putting it outside your thermal barrier means that its now a temperature conductor. In the summer is will gain heat and reduce the insulation performance of the straw, in the winter it will conduct heat away from the thermal barrier and again reduce performance. Put the thermal mass inside the structure and it does the exact opposite it helps regulate interior temperature and thus increases overall performance of the building. So inside VS outside, you want the insulation outside.
3. Straw slip has a lower R value per inch vs bales, it is really meant more as a semi-structural material for cob based architecture. I don't see the value in this application. If I lived in a very temperate dry climate then I would say straw slip has good value.
4. Glass bats are my personal LEAST favorite insulation material, they hold moisture, are hard to install properly etc.... I much rather recommend spray foam for the basement, foundation or crawl space.
5. Minor point of interest, there is some debate on the R-value of a straw bale and generally the numbers are between R-30 to R-50. R-50 is on the high end so don't assume that to be a hard consistent number. That said R30 is probably more then enough for this type of application in that climate.
I don't see why you would want to do this. You would be moving free thermal mass to the outside of the envelope and loose space. Also the structure would not necessarily be equipped to handle the loads on the interior. seems to me for the same or less work you could do the outside and have a lot more on the plus side then the minus.
Just because they're telling you how to do something better doesn't mean they are pushing it as "best practice".
Blower footrests are fine and performance is vital. The problem isn't the what it's the why. And for me the why is a healthy structure that promotes a healthy environment for the people and things inside. Who care how well it performs if it makes me and my children worse in life?
If your layers of glass aren't properly sealed you will get serious frost buildup in the winter which will over time (probably not long) rot the wood surrounding the glass. Also, under the sun the glass can experience massive thermal gain which can cause failure of the glass itself.
I think in order to do it right you will meet to retrofit newer sealed units into your window openings. However that said the performance gains will be massive.
In "traditional times" people lived almost half as long too. I'm sure mould was ever present and it probably silently killed many children and adults before their time. I think a lot of what drove the "modern mindset" comes from the desire to live a full life.
A mass building that remains just warmer then freezing will grow mould in mass because the walls will always present a condensation surface.
Yes insulate but IMHO if you looking for ways to insulate your mass you should look at other forms of building like straw bale. There is no one solution to fix the world. Context.
Everything in context including cob. Materials and practices succeed or fail based on the context in which they are used. So this means that in some climates some materials or practices thrive while in others they fail.
I consider cob to be a thermal mass material and it will generally behave like stone, concrete or other high mass systems. This means not good for cold climates without massive energy input.
Just because you like cob and what it stands for doesn't mean it's use is either efficient or ethical in certain contexts.
Like I've said before my take on the reason tyvek typically doesn't perform is because it's generally sandwiched against exterior sheathing. When it's on it's own like the diffusion wall then I can see it working much better.
Jay, the arctic wall is just an adaptation of the diffusion wall system being used in Europe for a while now the key difference is that in Europe the wall is thinner because of the need for less R-value vs Alaskan winters. It has some history behind it beyond that application. The wall system is being monitored in real time tracking how the moisture moves and has been for a few years now and the have found that te home wrap does in a practical manor diffuse moisture as designed in the real world even in the dead of winter.
Brian, I think arguing that there should be no obvious holes in the wall system is kinda like saying cars run better on roads. We're way beyond that and the discussion is about the next level of thinking. The holes are a given, I don't think anyone builds a wall with holes as acceptable.
What jay said about plastic used inside walls it totally true. I don't care how many holes you have 6mm plastic is a junk solution.
I can't speak for JC buy drafts to me are holes in the wall system where air and water freely flow allowing uncontrolled air exchange. Permeable is a structure that has the ability to passively dry quickly enough that any moisture interacting with the wall system won't damage the wall system. Also if possible a permeable wall system should be designed to move the humidity in one direction, out.
Whether air exchange is controlled passively or mechanically is another topic.
I would classify the "arctic wall" promoted by CCHRC to be air tight but vapour permeable.
First things first if you are building or renovating a structure that is going to house the public it is your responsibility to ensure that it is safe in every way you can think to make it so. My recommendation is to involve an engineer who can help you with that process. Structural integrity comes before insulation in an existing structure. This is your first responsibility.
Properly insulating the inside of a steel building is generally hard to do well with fibreglass on the walls, you may find a good place for the glass in the roof for it though.
Probably the easiest overall would be to just strap the inside with wood framing and infill with spray foam for the walls. You could look at things like strawbale etc on the inside but I honestly done see making it work properly being worth the effort.
From what I can see in the commercial side of the industry LEED is being abandoned by many in the industry because it's just way too top heavy and frankly it adds SIGNIFICANT costs to projects with little quantifiable return. Where I live the support just isn't there outside of some government projects.
I would say this. For me I tell clients that the first question to answer in the process is "how do you want the building to perform?" So performance drives the process for me. Having the ideal ecological etc solutions and a home you don't like being in long term is a non starter and turns others off the whole idea. Others might say people just need to suck it up and live a harder life but that's not a viable answer to adaptation of sustainability on mass. Life has to be enjoyable for the majority of people in order to have impact.
I generally don't appose many of the modern products or industry but I really want to be able to take everything that I can IN CONTEXT. So I'm positive about foams etc if they work best in context.
I don't think anyone has ever argued here that an airtight envelope is bad so I'm not sure why you keep harping on it?
The place where I think your not following is that we're discussing building practices that go beyond just air sealing. "Best Practices" don't actually outline "the best practice" they outline the current fads that some governing body has decided to endorse no more and no less. Minimum code requirements across North America are way out of date, way too low in the performance department and HEAVILY politically influenced following that as a best practice I largely ignorant when we can do so much better for relatively little extra input.
Thermal mass has been discussed to death. If you don't see it you don't see it. Passive solar, same deal. Anyone who is building for efficiency and not accounting for passive solar as a foundation of their design criteria is an idiot. It's simple free energy input that has been used, tested, proven centuries ago. Why you would go through the expense and effort to build a high performance building without accounting for passive solar and thermal mass as part of the design is plain foolish. Passive solar and thermal mass can often be accomplished for little to no extra cost over typical building practice so why one interested in permaculture would neglect to address it is beyond me.
The ideas and information from the 70s is 40 years old, we can do so much better with lower impact now why wouldn't we?
I would think a single story strawbale structure would work really well in your climate. Good insulation, good thermal mass and cost to build isn't outside the box either.
The venting systems aside you might want to consider building some insulated thermal mass into the room to help carry that heat through the night. Night time is probably where you are seeing the most loss.
The problem and one we recently experienced close to my home city is that even a lower volume dependence on the grid can set you up for issues if there is an interruption of a few days.
I think current practice is a fad because it is largely discounting passive solar which is definitely superior and not much more expensive then a simple higher performer upgrade to the existing. It's all progressional but why would you want to go to seething that was current in the 70s when we have so much better and proven solutions available now?
I will agree with Brian that performance comes first, in so much as a structure that is a pig to keep warm and dry is not sustainable long term.
The current fad in "building science" is all about sealing and insulation right now and that's great but it's still ignorantly based on the idea that a structure should be heavily grid dependant or at the least mechanically so.
I think HVAC systems begin to lose a lot if their overall value when a building is well balanced and uses passive solar design. I'm still a fan of HRV systems but a building can have a passive design that allows air to naturally move in convection loops within the envelope and that is where TM comes into play as well as working as a storage and buffer for solar thermal inputs.
I understand the desire to use found on site materials to build but as has been said on the forum before:
1.Yes you do want to seal your foundation as much as possible as well as insulate it from direct contact with the earth if you can. You don't want your house drawing up moisture and gasses like radon into the envelope. You also don't wand the earth to wick away heat like is happening with this home.
2. Thermal mass does not compensate for insulation, they are two different concepts with two different roles. If your in a really temperate climate where the earth never or almost never freezes and it's usually dry then yea thermal mass alone can accomplish efficiency. Otherwise you need to insulate.
3. A thermally high performance structure can inherently handle and maintain higher levels of humidity because the moisture isn't presented with a surface to condense upon. So yes always set a performance standard as your primary goal in construction everything can easily build around that. If you don't then you can have an inherently compromised structure like this one. All the energy put into an "ideal home" you can't live in and now needs major rework.
4. Take the design phase of home building extremely serious, it's not a one size fits all equation. A design that works great on one place can be a failure just a mile away. You have to ask the question "why?" a lot. Nobody knows everything, if your builder/consultant only has experience in one or two disciplines that is a sign you need second and third opinions.
5. Foundations are the most important part of your building.
6. Even if it's DIY, "Buyer beware". Don't let yourself get caught up in the hype of anything be diligent.
Without the mass you have a solar house not passive solar. The mass is there to mitigate the temperature peaks passively. The idea is part of the efficiency comes from not having to mechanically manage those fluctuations which are pretty extreme when direct solar radiation is your primary heat source. So yes the mass doesn't replace a good envelope but it does a great deal to make a passive solar system work.
I think we can confidently say that cob alone would be inadequate. So I've turned my thinking to hybrid designs: how would you "stick" interior cob to exterior straw bale?
If you could confidently link the two, then questions about load bearing abilities come to mind. And since I have a family I can't really move them into an experiment. Well, I could... but then they'd run away, write a book, and there'd be a documentary about dad's stupid house.
I'm not super pro or con anything so non-natural materials wouldn't be a deal breaker.
Maybe we need to have a 3 season cob home and a winter McMansion. Yeah... that'll do!
The simple answer is structural straw bale with cob as the wall plaster. Its done all the time, no worries.
If you only build a structure to efficiently keep warm air from mixing with the cold then yes TM is a non starter. If your building a structure to be a healthy comfortable place to spend large amounts of time then I think paying equal attention to TM is important.
Hmm you want the walls not to be so packed with material that they hold water. Thinner could be ok.
You have to assume that bathrooms will always have a higher amount of humidity though so concrete is preferred over fibreglass to me and ventilation is really key.
Maybe you should explain what you mean by removing wall cavities?
-Generally for walls you want a concrete board surrounding the tub/shower area this will resist the mold when damp.
-ensure that all your stuff is not level, in other words you don't want your surfaces to drain in any direction other then the actual drain.
-Use quality shower/tub products that won't leak
Those are the basics, maybe you can give some more information for better answers.
I actually view thermal mass on par with insulation and sealing. In fact I think proper use of thermal mass is in some ways much more difficult to achieve.
I'm not sure if I know of a way to passively deal with humidity.
Yea I'm not suggesting specifics but a more mass based system would probably be ideal especially in the summer. Just because this year has been a peak for low temps doesn't necessarily mean you build to the peaks, you build to the averages with the ability to function in the peaks. So something like Straw slip, earthship etc could all work really well in that climate as apposed to a more northern climate where they don't really work well at all.
I would say above 60% year round. But I would go with thermal mass over permeable insulation in your climate. Cob and the like probably work stellar there.
Unless you are in a VERY humid climate I think things like showers, cooking, cleaning etc will all generate higher humidity than outside, especially in peaks. You're still better off releasing to the outside. Maybe in a place like Florida but that isn't a climate I would use this type of wall system anyhow.
I'd say the performance if the arctic wall is almost completely based on the fact the tyvek isn't backed by sheathing. I guess the dense pack acts as a backing of sorts.
I'm willing to gamble that sandwiching two materials results in a higher level of resistance than the sum of the two materials individually.
