Detail directory
user-757117
| Posted in Plans Review on
Or perhaps detail dustbin…
If you have a detail that you think would be beneficial to the GBA community, please post it here with the hope that it may eventually be selected for permanent enshrinement in the GBA details “library.”
All climate zones are welcome.
It is a shame when perfectly good details become lost in the “void” of long dead Q&A threads.
I should also mention that this thread is listed under the “Plans Review” category for reference.
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Thanks, Lucas, for starting this thread.
And thanks again to all the GBA readers who have been posting details. Keep them coming.
As far as I'm concerned, there's nothing wrong with re-posting details here that have appeared before in other threads -- it's helpful for everyone if these details are all gathered together in the same thread.
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To get the ball rolling I'll re-post my "cold climate hat" detail.
These are meant to be low-foam details, with foam use restricted to below grade applications and crack sealing.
The roof/wall section does not include interior/exterior cladding.
The larger section shows service cavities on the interior which can, of course, be deleted.
Lucas,
Just wanted to say...I think your drawing is exceptional.
It reminds me of some very fine drawings from 1911
http://books.google.com/books?id=plY1AAAAMAAJ&pg=PA99&dq=William+a+radford+old+house+drawings#v=onepage&q&f=false
John, thank you. I'm glad you like it.
I have often been accused of being "too old-fashioned".
I guess my mutton chops don't do much for me in this regard.
Lucas, thank you for posting your diagrams. The details of the insulated drop ceiling are a method I have not seen before.
How would you detail the vapour barrier around the ceiling lights and Octo boxes?
- Jim
Lucas, great cross section detail. Drawn well my friend and I like the design concept you are working on.
Lucas, In the slab detail, the poly runs over the concrete. Most of the info I have gathered indicates the poly should run over the XPS and under the concrete. Am I missing something?
Jim, thanks for your interest.
I would include the service cavity at the ceiling plane. A 3/4" cavity would allow the use of "pancake" style boxes.
Because of the extra material I struggle with the appropriateness of the "service cavity" idea. In this case it makes detailing of the poly air barrier much easier by eliminating penetrations at electrical boxes.
No, I would run the poly under the slab as well. I'm not sure that extending the poly all the way under the slab is necessary if using XPS. The red line represents the ACL - a term which I have been told is falling out of use now - and can consist of materials other than the poly. Anyway, as long as the poly and concrete are tied together, or the slab perimeter is otherwise sealed, the slab becomes part of the air barrier asembly.
Some framing details that belong with the others.
Lucas,
I finally found out why my attachment was failing, concerning the strawbale wall with a rainscreen. Thought I would post it here so that you might see it. It includes a post and beam structure so it doesn't address your original idea of how to attach the rainscreen to a bale, but it does attempt to detail how you would attach the rainscreen to the P&B structure.
Dylan, thanks for posting that detail.
Air sealing details:
Also, would it not be simpler to eliminate your drop ceiling idea, and simply get raised heel trusses to whichever depth insulation you need. Wrap the underside of the trusses with osb/ply and use that as your air/vapour control layer again. Same use of your service layer, just with a potentially simpler detailing.
Would a 3/4" service cavity pass canadian electrical code? That was one thing I was trying to find out... for instance, creating the service wall with 2x2's, and having a horizontal chase behind the baseboard like Bensonwood had approved.
Lucas,
Is there any particular reason you wouldn't just use the plywood/osb interior wall sheathing as your vapour/air barrier? Seems like it would be far more vapour open than using poly.
Your timing couldn't have been better as I've been hashing the double-stud wall with interior service wall over for the past few weeks and could not get my mind around bringing the load bearing wall into the middle wall. With the service wall, effectively hiding the slab edge foam, it's nearly perfect.
This is quite similar to what the Bensonwood guys are pushing. The concept of separation of shell from service is one that really clicks with me. Keep this stuff coming, it's great.
* I just noticed you're using planks instead of sheathing. Still a nice build.
John, thanks for your interest.
"Airtight" sheathing was my first choice approach for air/moisture control. Despite all the evidence to the contrary, I have not been able to convince anyone with any signing authority that a VB is not required in my climate... Since I am required to put one in, I figured I'd run with it.
The "drop ceiling" is probably not going to be the most affordable... The alternative you suggest may turn out to be more so...
An advantage to the "drop-ceiling" is that it separates air control and thermal control from the "cladding function" of the roof.
The insulation and air barrier stay over the conditioned space while the roof is free to go where it likes - like over an unconditioned garage or covered porch say.
In this way the roof is just like a large, slanted rainscreen.
John Brooks once called this roof concept "a hat", which seems like a good description to me.
Good question, I'm not sure... I am planning to do the 3/4" service cavity at the ceiling only using "pancake" boxes for light fixtures. I've been over the plans in detail with my inspector and she didn't have much to say - except that she thought I'd have a hard time wiring in such a small space...
Lucas,
At one time I considered building sort of a barn-like structure and then building an enclosure inside the "barn".... with all the layers neatly lined up.
Or build an enclosure and then build a barn around it
This is how I imagined a wall cladding structure and a roof cladding structure could be Isolated from the Living Enclosure.
The Living enclosure would be wearing a "coat" & a "hat"
Claddings (siding & Shingles) could be replaced without disturbing the nest..
fun to think about .... but perhaps not-so-practical and not-so-affordable
Lucas,
I like your overkill attitude.
I think John O'Brien is asking some good questions.
The concept of isolating the "layers" and the structure has a good sound to it.
It just does not seem very practical.
Is more than One Thermal Layer so bad?
Is it bad for the structure to share space with a thermal layer?
Have you looked at Thorsten Chlupp's "SunRise Home" ?
Thorsten's climate is likely more extreme than yours...
He is not using a vapor barrier.
John, I agree that this envelope is not-so-affordable.
The "drop ceiling" has pros and cons - certainly, there is a high labour component.
Service cavities have pros and cons - again there is a high labour component.
I tink that the pros of either could outweigh the cons given appropriate circumstances.
Two sheathing layers is definately not-so-affordable.
I am presently attempting to eliminate the exterior sheathing altogether.
I think Robert has done this on a number of his houses.
Here's more Lucas on layering with links to more. She's got a pretty good blog which I linked via Martin's review of her work --
http://www.ecobuildtrends.com/2011/02/designing-in-layers.html
John, I would say that Thorsten's climate is much more extreme than mine.
I wish I could say good-bye to the concept of the "VB".
I think Robert was right when he said we should avoid "hermetically sealed".
Poly is too impermeable - not to mention a possibly redundant material.
ADA is a bit too moisture permeable.
Exterior grade plywood is a class II vapour retarder... just about right.
I wish I could convince the "auhorities".
Lucas,
I am NOT a building scientist...
The PLYWOOD air & vapor control layer has "sounded" like a pretty darn good idea to me for a long time.
It is encouraging to see Thorsten experimenting with it.
I hope he publishes something soon
JoeW, thanks for the link.
I think there is something to the "layering" concept.
I like the "spaghetti bowl" analogy.
I am reminded of double stud walls where the load paths are all mixed up and confused.
It doesn't seem to make much sense when it is possible to build a double wall that uses only one "layer" to transmit roof/floor loads to the foundation...
Hey Lucas,
You have been quiet for a looong time.
Did you start building your house?
And/Or... do you have any new "half-baked" ideas?
here is a detail I came up with for my house. I used the PERSIST/REMOTE approach, slightly modified for the tricky TF. Yes it's very foamy, but at the time I thought I was building green...now I just have to settle for HP and possibly stuff some straw in the wall cavities
Hi John, I am building and I'm already 3 weeks behind and over-budget :-P
I haven't been on the net much lately but I always try to have a peek at what's going on at GBA when I am... I found interesting the details you linked in your "Sweedish Food for thought" thread.
Most of my "half-baked" ideas have lately revolved around solving specific little air-sealing problems... high temperature copper pipes penetrating the air barrier... an "air-tight" firewood hatch through the exterior wall... the ceiling support assembly for the chimney...
I'm hoping to eventually get a blog going with all the details posted with photos...
What about you? Are you any nearer to finding a more ideal profile for your mixed/humid zone 3?
I still think a scaled and modified "ARCTIC" concept could provide not-so-foamy, buildable and possibly affordable profiles for any climate zone... That photo Thorsten's crew setting up roof trusses on a plywood deck keeps coming back to my mind.
I like the "core"(Plywood Pressure-Boundary) of the Arctic Concept...
and I like the Vented "cowboy hat" (roof cladding structure)...
And that the Wall & Ceiling Service Cores are INSIDE the Plywood-PB.
I still think OUTIE windows in the same Plane as the Plywood-PB would be more Buildable/Durable.
I think that a Plywood-Pressure-Boundary would be "Buildable"....
Easy to Understand, Inspect,Test and Repair
I don't think that trying to create an air barrier at the Rigid Insulation is such a good idea.
Especially if mixing partial structural sheathing and partial Rigid Insulation.