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#32878 - 03/30/15 03:35 AM Wrap and Strap..how it works?
Snickare Offline
Member

Registered: 05/25/14
Posts: 16
Loc: Gavleborg
Hi Guys,
i have read something about this insulation method,an alternative to SIP,someone can explain to me how it works?photos or drawings are very well accepted if someone has them..thanks for the help!

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#32879 - 03/30/15 04:11 AM Re: Wrap and Strap..how it works? [Re: Snickare]
Snickare Offline
Member

Registered: 05/25/14
Posts: 16
Loc: Gavleborg
Just another question that came in my mind..in case i want to have drywall on the inside of the building,what kind of thickness should i pick?thanks again!

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#32882 - 03/30/15 11:30 AM Re: Wrap and Strap..how it works? [Re: Snickare]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Hi Snickare,

I am not sure I could even begin to do justice to this topic...even if I wrote 20 pages. It is much more complex and varied than that. It depends if the project is going down the route of "mostly natural/traditional" insulative methods or an augmentation of systems.

It can include "cold roof/rain screen" systems, wall truss (a.k.a. Larsen Truss) systems or just simple "2x" strapping on the outside of a frame, among the most common methods, yet there are more as well.

Drywall thickness isn't really a consideration until a finer element of design is considered. I for one don't use drywall nor promote it. We use traditional lime or earth plasters/renders, textile or wood wall treatments.

Sorry, not much help on this but perhaps it offers some more areas to research with...


Edited by Jay White Cloud (03/30/15 11:30 AM)
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#32883 - 03/31/15 01:57 AM Re: Wrap and Strap..how it works? [Re: Snickare]
Snickare Offline
Member

Registered: 05/25/14
Posts: 16
Loc: Gavleborg
Hi Jay,
thank you very much for your reply,i was actually referring to this method,https://www.youtube.com/watch?v=jNdipEU3xoo

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#32884 - 03/31/15 12:19 PM Re: Wrap and Strap..how it works? [Re: Snickare]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Hi Snickare,

I have been "pulled in" on project similar to this...I do not promote or encourage such designs.

First I should validate that I am a staunch "traditionalist" and avid natural building enthusiast. I don't believe in "airtight" architecture (accept in spacecraft and submarines) and only promote permeable "draft proof" methods of building...in other words...NO HOUSE WRAPS, condensing surfaces and/or elements that will block moisture from freely escaping the interstitial zones of a buildings thermal diaphragms.

I also promote and design architecture under the principles of "disentanglement." We still have a rabid normative culture in the building trades of "not my problem" and "get it done fast...while making as much money as possible." Both of these "psychologies" inundated the building industries and its facilitators. Structures are designed with too many "reinvented wheels," and "tunnel vision."

The structure in the video may seem applicable in "concept," however...

Can moisture actually escape the walls effectively without being trapped or condensed at time of the year promoting fungal and mold activity?

How easy will it be to run mechanical, electrical, HVAC element and related necessities?

How will the architecture endure over time?

How will future owners upgrade, augment, or alter any of the "systems" without tearing through the 2x material or an outer wall insulation system and its siding?

The architectural elements of the timber frame in the video are the complete opposite of "disentanglement" principles. There is no "cold roof-rain screen" elements. No mention of how electrical/mechanical will be address without "tear out, cut/drill through" of previous work, as well as clear indications that this building will probably require "air to air heat/ventilation" mechanicals (ironlung) to make the system work...Then the question is for how long, at what cost over all without maintenance, and other issues...

I see this type of "wrapping" too often and find it "narrow in view" of a much bigger and longer picture in good design and building practice. It often comes with comments like..."well we can make it work this way..." That is great, but I don't what to "make" my designs work...they simply need to work with as little effort as possible and the fewest moving parts possible. What parts there are need to be easily accessible when (not if) an upgrade, augmentation or repare needs to be facilitated. This may cost more in the beginning (not necessarily) but in the "big picture" and long term durability of the architecture...it is much less expensive.

Regards,

j


Edited by Jay White Cloud (03/31/15 12:21 PM)
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#32888 - 04/01/15 09:26 PM Re: Wrap and Strap..how it works? [Re: Snickare]
TIMBEAL Offline
Member

Registered: 12/10/07
Posts: 1875
Loc: Maine
I like Jay's approach. Does time always allow for these beautiful methods, not always. Worth consideration.

As for the wrap and strap in the video. I don't like the 2x framing on the outside of the t and g. It will be a bugger to get sealed when fitting all the pieces of foam into these spaces. Instead just wrap the sheathing in 4'x8' foam sheets and apply strapping to the outside of the foam with panel screws.

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#32892 - 04/02/15 10:39 AM Re: Wrap and Strap..how it works? [Re: Snickare]
timberwrestler Online   content
Member

Registered: 11/07/05
Posts: 269
Loc: Becket, MA
I agree with Tim on the 2x framing around the foam.

Jay, I'm all for disentanglement too, but what natural building enclosure would allow for that (with reference to mechanicals)?
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#32893 - 04/02/15 11:23 AM Re: Wrap and Strap..how it works? [Re: Snickare]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Hi Tim,

Thanks for that, and I agree time actually appears to seldom allow the "better approach" in the current American market of construction...both mainstream "2x" residential or even our beloved timber framing...

I just left "another" of such projects down south in a vintage timber frame conversion that will be facilitated virtually the same as you just described...

There was 1" antique barn board placed on the frame first, then 4'x8' of plywood, then 2" polyiso foam board as a thermal break, then a 2x vertical on 16" center, then 3" of spray foam, and then (thankfully at least) a rain screen system is suppose to be installed (I am no longer on the project) so I am not sure this will take place.

Now there are already logistical issues with mechanicals and electricals, and the questions of achieving proper ventilation. All of course dependant on expensive HVAC systems to make these augmentations of modernity work, as well as, other logistical planning issues and "tearing through" work already done to achieve both the HVAC and the M/E. Again, more common than not, the trend that some alleged "experts" in HVAC engineering and architecture insist on doing even in the face of overwhelming issues to the contrary.

I am afraid too many buy into the notion that time doesn't allow better planning, as in the long run the other issues seem to far out way good planning and design in the beginning. The "breathable" and "disentanglement" issues, seem to present as actually the path of "good practice" we should go down. These methods of "disentanglement" are actually more common in large commercial work (i.e. skyscrapers, hospitals, etc) than they are in residential here in our markets. Even natural and more sustainable building materials are finding their way in. I am hopeful, as more clients and craftspeople ask these questions, that each project will see more and more shifts in that direction. For the projects that do go fully traditional, natural, and/or sustainable, such a "straw clay slip infills," straw bale, pisť infills, mineral wools, etc, the outcomes are proving more than just good practice, but fiscally better in the long term of durability and maintenance.

Regards,

j
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#32894 - 04/02/15 11:57 AM Re: Wrap and Strap..how it works? [Re: timberwrestler]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Originally Posted By: timberwrestler
...what natural building enclosure would allow for that (with reference to mechanicals)?


It comes down more to a shift in material application and design approach modalities, with more "permeable" materials and not this fixation with building "space ship" (a.k.a. airtight) architecture that doesn't take into consideration all the other environmental-structural events that a building will experience over what we hope would be centuries. Too many builders and manufacturers have a very "short term" views of architecture. I have routinely heard industry leaders in modular (a.k.a. stress skin panel) and modern building state very clearly that there view of modern domestic building has:

"...an economic and viable lifespan of less than 30 to 50 years before major upgrades, interventions and/or augmentation take place..."

This is great for the industry, GC, and Developer (i.e. bank accounts)...It is horrid for the property owner, the architecture and our planet...

Take a rough cut 2x8, stick that in a jig and punch a single plunge mortise (`20mmx50mm) with a standard bit Makita chain mortiser ever 500 mm, then split into a 2x3 and 2x5, gives you a wall truss framing member once spans are added to the desired length, that can now range in thickness from 300 mm up to 1 meter without additional verticals members added. This system of wall truss can more than accommodate a myriad of natural insulative methods as described already from SB to a mineral wool matrix, or others. We can in house manufacture several different forms of wall truss for most projects in less than 2 weeks for the average project in the same pricing window of most (if not all) stress skin systems. These wall trusses also facilitate greater ease in HVAC, H/E, and other augmentation, including future upgrades. These systems do not require (if planned for) the "tear out and through" so many other systems require. This is just but one methods of the "traditional-natural" building movement I have seen or facilitated in the last decade. Just basic web searches into "breathable walls," "natural building" "wall truss systems" (search in German, or in a European Google search can reveal more), cobb, straw bale, etc can really get the "creative juices" flowing in this direction. I for one will not turnkey my own projects anyother way.

Regards,

j
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#32897 - 04/02/15 10:50 PM Re: Wrap and Strap..how it works? [Re: Snickare]
TIMBEAL Offline
Member

Registered: 12/10/07
Posts: 1875
Loc: Maine
Strongly recommend an air exchange system in a wrap and strap building. I have seen examples of owners choosing not to use it due to cost and then they have issues.

An exception would be sections of my own home, where I can walk down a part of my house through a hallway and have snow blow on me. I need to address the issue, until then, I think..... fresh air.

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