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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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#32898 - 04/02/15 11:33 PM Re: Wrap and Strap..how it works? [Re: Snickare]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Right you are Tim!!

As can be told from my views...I don't recommend or like "airtight" architecture but rather "draft proof" with only permeable insulation and no "house wrap"...

However...

If going the way of "airtight" and wrapped in foam...I haven't seen one work yet that does have an "air exchanger" system to make them work...


Edited by Jay White Cloud (04/02/15 11:33 PM)
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#32900 - 04/06/15 09:30 PM Re: Wrap and Strap..how it works? [Re: Snickare]
Hylandwoodcraft Offline
Member

Registered: 03/23/11
Posts: 141
Loc: Western NY
This is an interesting thread. I have done quite a few projects with a fairly standard SIP approach. I increasingly feel the limitations of this type of approach, and really want to be able to spend some R&D time on alternatives. I am particularly interested in a "Chip and Slip" type non load bearing wall. I just need to find the time (and a competent plasterer).

For the time being, I am trying to increase the workability of the Sip type enclosure with cold roofs, rainscreens, EPDM gasketing, etc. It's hard to escape the feeling though, that the sip enclosure may be overly complicated to properly detail.

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#32901 - 04/06/15 10:43 PM Re: Wrap and Strap..how it works? [Re: Snickare]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Hey Sean,

Good to hear from you!

The more the years go by, the more I become impressed with the "old" traditional systems and our new knowledge of them. I also grow less and less impressed with what modernity has to offer and the damage it does to human and planet health while making billions for large industries...

Lite straw clay slip infill methods (and related others) are nothing more than traditional "insulative" methods of cobb and related "wattle-daub" work. As an infill and/or overlay system they are proving each year to not only be efficient, but healthier and more in balance with our goals as sustainable builders (and Timberwrights.) I see these systems being "revitalized" with modern understanding while still incorporating traditional wisdom. Set to work in concert with other "permeable materials" like mineral wool board/batt we can achieve highly effective thermal envelopes, without issues of trapped interstitials moisture all to common with the "airtight" concepts...
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#32947 - 04/20/15 10:45 PM Re: Wrap and Strap..how it works? [Re: Snickare]
collarandhames Offline
Member

Registered: 07/03/08
Posts: 191
Loc: Peterborough, Ontario
While not getting all fancy with building wrap, vapour barriers etc works for some, those of us in cold climates up north need to realize that many months of sub zero temps can provide breeding grounds for mould if not detailed properly.
Up here in canada, we have a motto. Seal tight and vent right. Which means continuous vapour barrier on the inner third of the insulation (or better yet, on the inner face), and yes, mechanical ventilation. I live in a war time story and a half, and the first year I lived in it, I replaced all windows and sealed up all outlets, switches etc. as well as replacing the old chimney furnace with a high efficiency furnace, thus eliminating the air exchange in the house.The second winter we all fell sick as I had made my house simlar to placing your head in a plastic bag. Third winter , I had installed an HRV, and we all breathed better. The HRV was 1500 bucks installed, but now with our sealed tight vented right house, the natural gas bills are around 400 bucks a heating season.
Those who want to tell me I'm wrong, hey,, how cold is your winter? It is an issue.
hope this helps. Cold climate building is another thing.

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#32948 - 04/20/15 10:48 PM Re: Wrap and Strap..how it works? [Re: Snickare]
collarandhames Offline
Member

Registered: 07/03/08
Posts: 191
Loc: Peterborough, Ontario
I should note that we are currently experimenting with pre-fabricated straw bale walls, which do "breathe". They will take on moisture threw the plaster, but as long as the seasonal inner condensation is less than the amount let back in the warmer months, it's a good system.
Building enveloping, a new thread?
dave]

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#32949 - 04/20/15 11:49 PM Re: Wrap and Strap..how it works? [Re: Snickare]
Jay White Cloud Offline
Member

Registered: 11/06/08
Posts: 480
Loc: Vermont
Hello Collarandhames,

I don't believe I can agree with many of the perspectives you just shared about vapor barriers, yet understand that view is common. I would love for you to join Permies.com and perhaps read some of the information there and engage in a the same conversation there about these concepts of "airtight" architecture. Not to dissuade you at this time, but I think you would enjoy reading some of the other perspectives in natural/traditional building modalities.

Hope to see you there,

j
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#32958 - 04/30/15 10:05 PM Re: Wrap and Strap..how it works? [Re: Snickare]
collarandhames Offline
Member

Registered: 07/03/08
Posts: 191
Loc: Peterborough, Ontario
Jay, I am eager to learn of others ideas. I do know that a lot of air flow threw a small hole in interior stucco will lead to condensation at dew point. It's all relative. If the ambient air is being ventilated in areas of high moisture , like bathrooms and kitchens, then I think we are all good.
I will look at the site you reference, and look forward to learning more.
dave

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#32959 - 04/30/15 10:17 PM Re: Wrap and Strap..how it works? [Re: Snickare]
collarandhames Offline
Member

Registered: 07/03/08
Posts: 191
Loc: Peterborough, Ontario
Jay, I had a quick look, and knowing you are in vermont helps. However, we have such cold temperatures for such a long time, I am concerned with the amount of moisture that can enter the wall cavity over successive seasons, and the longevity of the wall. My partner is planning on doing some prefabricated straw bale panels this summer, and I will chat with him in hopes of enlightenment. A lot of the folks on this Permies.com page have no experience with our wickedly cold long winters. Again, I have a good basis of the building envelope in normal construction, and have seen where too much lack of detail can cause studs to rot, but am eager to learn more of how it works in my environment. We have a super green builder in town -Chris Magwood, who is pushing the building envelope, and I'll try to chat with him. I actually helped install the steel roof on canada's greenest home. I'm totally into it, however, as I can't help it, will be naturally skeptical until I understand the properties involved with the wall system in my climate. Always eager to learn. dave

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#32970 - 05/15/15 05:05 AM Re: Wrap and Strap..how it works? [Re: Snickare]
Jon Senior Offline
Member

Registered: 05/04/11
Posts: 112
A well-wrapped building requires (mandates in fact) a form of mechanical ventilation... which itself needs to be correctly sized and well thought out. My personal view is that as we increase the insulation in a house, leaving it "leaky" becomes less of an option. Putting 30+cm of insulation in walls serves no purpose if you allow uncontrolled airflow. Mechanical ventilation also allows you to introduce fresh air where it is required, which may not correspond with the placement of windows and to ensure a logical airflow throughout the house, where humid air (such as in a bathroom / kitchen) is not circulated through "dry" rooms before being extracted. Here in Europe, passive houses are fitted with mechanical ventilation systems that extract calories from the "used" air and thus pre-heat the incoming air, and the remaining heat in the air is passed through a heat pump to be used for heating domestic hot water. This is admittedly a highly-technological solution.

If you're prepared to treat the envelope as a "living" structure where low-cost walls can be cheaply replaced or rebuilt as necessary (straw bale + clay render for example) then to a certain degree the risks of moisture incursion can be ignored as the material cost (environmental and monetary) is low, but this has to be considered as a part of the ongoing maintenance of the building.
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Contemporary Norman longhouse in Normandy

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