Roof and Wall Design

This topic contains 13 replies, has 4 voices, and was last updated by Sean Hyland Sean Hyland 4 days, 15 hours ago.

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #17341
    rrbounds
    rrbounds
    Participant

    I have been thinking about alternatives to the standard SIP that many use to cover the Timber frame.  After viewing what Ecocor does on their prefab designs, I believe some sort of a variation of that design may be a good alternative. What are your thoughts on this area of timber frame building

    #17351
    Brice Cochran
    Brice Cochran
    Keymaster

    There are a lot of alternatives to SIPs including the system the Eco car constructs.  I was unfamiliar with them but with some surfing on their site, I am up to speed.  There are a very other larger timber frame companies that create there own panel system.  Benson Wood and New Energy Works are two that jump into my mind.  Benson has an article about there’s here and one on New Energy’s here.  There are all kinds of way to do it yourself, is that your plan?

    What is your opposition to SIP’s?

    #17359
    rrbounds
    rrbounds
    Participant

    Thanks for the reply. Other than cost, I have no real opposition to SIPS. However, I am a serial DIY.  I believe I can build a cost effective, efficient shell system for whatever timber hybrid I end up building. As I am located in a lower zone 4, I don’t need the super insulated, but do want to build an airtight appropriately insulated structure. Ideally I’ll find someone with a design that makes sense for my case, and I’ll go from there.

    I would like to take the larger hammer beam you have listed, and design a smaller home with the timber space as the central area. I’m just in the playing with ideas stage – where I am collecting information.

    #17360
    Sean Hyland
    Sean Hyland
    Participant

    rrbounds, That’s funny! This was the exact topic I as planning to introduce since I find the enclosure to be the thornier side of TF.

    A bit of background…I have been building timber frames for about 10 years and started out with the conventional SIP approach. As I got into it further I became more and more aware of the limitations of the SIP panel and first tried to augment my installs and finally have abandoned the SIP concept in favor of my own system.

    Perceived SIP deficiencies first. First of all, I have seen 20 to 30 year old SIP failures which demonstrate that the OSB is definitely the weak link, and any given system is only as good as it’s weakest link. If we feel very generous, let’s assign a lifespan of 75 years for a well detailed SIP enclosure. What is going to become of all the foam at the end of the lifespan? EPS can be recycled, but only for very clean material, certainly not building salvage with adhered facings. Will it be burned? Buried? Spreading foam bits far and wide as it gets demolished. Who really knows.

    I didn’t like the amount of indigestable foam waste I was putting into the landfill, much less thinking about the horrific long term possibilities.

    It became imperative to me to design an enclosure which can gracefully go into the earth when that time finally comes.

    In the shorter term, SIP are hard to repair because of there composite nature. Also very hard to add or modify wiring runs, lighting etc. The first owner is certainly only the beginning of a house’s history and it is seems short sighted to use systems which ignore the need for easy modification or repair.

    What I have gone to is a modified Larsen truss system with Roxul and vapor “smart” wraps. OSB is right out and everything is solid wood and Fir ply. All roof faces have a dedicated 1.5″ ventilation channel. The entire enclosure is designed to be very tight but also very breathable, with drying potential both in or out. The materials and components should prove both resilient under adverse conditions and easily repairable should the need arise. It also relies on passive systems for vapor management.

    The mechanicals are run in a separate layer from the insulation, thus simplifying both installs and making future modification easy without disturbing the insulation.

    This year I am also getting into some straw bale as a foray into another alternative system. The truss wall/ Roxul method is my “production” technique though. Easily understood by conventional builders and architects using “conventional” materials.

    I think that SIPS will continue to be on the outs over time. Some of the big shops like Bensonwood and New Energy have developed their own concepts because they recognize the inherent limitations of SIPS. I expect this trend to continue despite the SIP industries’ marketing clout.

    #17398
    Brice Cochran
    Brice Cochran
    Keymaster

    Sean, do you have a cross-section your Larson Truss Panel design, would love to take a look at it.

    Brice

    #17468
    Sean Hyland
    Sean Hyland
    Participant

    Brice,

    I would be happy to sent some pics and specs. I’ll upload some stuff when I’m at the right computer.

     

    #17470
    Brice Cochran
    Brice Cochran
    Keymaster

    Thanks, Sean.

    #17519
    Robert Wallace
    Robert Wallace
    Participant

    Brice,

    I am I the design phase of my first timber frame house. I too would be interested to see the wall system Sean is referring to. Have you ever heard of the “perfect wall” enclosure system. I have seen several YouTube videos pertaining to this wall design and have wondering how it might be incorporated into my hybrid design. I have no previous TF building experience to draw from, so I am asking the craft pros out there for guidance. Your input is greatly appreciated.

    #17523
    Brice Cochran
    Brice Cochran
    Keymaster

    I just did some research on the ‘perfect wall’ system.  I would agree with that it is a great system.  You can easily build that system up as the skin for a timber frame structure.  I know you currently live in NC where are you planning on building your retirement home?  It may have some impact on the advice you get.

     

    #17529
    Robert Wallace
    Robert Wallace
    Participant

    Brice,

    I have land in both South and North Carolina. I plan to build on either of the two locations. Both are in the foothills of the western NC mountain chain. The climates are very similar, with historically low snowfall or icing loads.

    #17618
    Sean Hyland
    Sean Hyland
    Participant

    Here are some pictures, although they will perhaps need some explanation. On the current project in the works I’ll have this system incorporated into the building plans so I’ll have some better drawings at some point. Here is a sketch of what I have going on with the roof.

     

    The third pic shows the roof starting to insulate. Under the green layer (Intesana) is the  T&G.  The second pic shows the roof insulation done (under black layer of Mento 1000) and additional 2×3 layer for air gap under sheathing which is started. That layer of Mento 1000 on the roof will tie directly into the layer of the same which is going on the exterior of the walls creating a continuous exterior membrane.

     

    Let me know your thoughts and questions…

    roof truss assembly 001-min 100_0013-min100_0002(1)-min100_0051(1)-min

    #17620
    Sean Hyland
    Sean Hyland
    Participant

    Robert Wallace,

    I did some reading on the “Perfect Wall” after you mentioned it which led me to reviewing PERSIST and REMOTE.

    Interesting stuff. I’m extremely happy with my technique on the roof but I have been considering tweaking the wall assembly as I think I can maintain my design goals while reducing labor time and complexity.

    The revision on the walls is very similar to the “Perfect Wall” concept, although using Roxul the whole way rather than foam.

     

    I should also clarify on my sketch above: When I referenced Roxul for steel studs I din’t mean that there are any steel studs in my enclosure. Instead, I am using a Roxul batt designed for use with steel studs since it is sized @ 24.25″ wide. That way it fully fills the cavity with almost no thermal bridging (only the intermittent 1×6 blocking).

    Sean

     

    #17628
    Brice Cochran
    Brice Cochran
    Keymaster

    Sean, is it possible to create “pre-built” panels on the ground and fly them into place on the roof?  Personally, I like to limit time slinging sheathing and the like on a roof. It took two days to fly all my SIP roof panels and put the underlayment on, which is fast.  I would also like to figure the cost breakdown on your system.  It is undoubtedly cheaper, always curious about the cost of things as it weighs heavy in the affordability of getting a timber frame.

    #17638
    Sean Hyland
    Sean Hyland
    Participant

    Brice,

    I have toyed with the idea of trying to panellize the system. I’m sure it may be possible with some modifications. I haven’t been too concerned with going that direction though since it seems like a bit of a trade off.

    You get to shop build more components and you decrease project time on site which are both plusses. On the negative side you complicate logistics (moving, trucking, and installing large assemblies), making it more reliant on heavier equipment.

    The building papers I am incorporating might be harder to integrate properly in a panelized system.

    The cost is certainly not any cheaper than SIPS. It’s actually higher in cost. The German wraps/tape are fairly pricy as well as the cost to go with better materials (5 ply Fir CDX over OSB) all add to the cost. Roxul is also more expensive than either cellulose, fiberglass, or direct purchase EPS.

    However, customers seem to be easy to convince on it’s merits, so it hasn’t been an issue.  I don’t really worry about being a volume producer, so the pressures might be different for someone seeking a high volume solution.

    I’ve come to the general conclusion in life that monetary cost is actually the most irrelevant metric of value, even though it gets treated like the most important. Yes it’s a factor, but it’s more important to build for quality than cost.

     

     

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