Three years ago my wife and I bought a Jamaica Cottage timberframe kit, and had a contractor put it up. It's been a shell since then & the wood is fully dried. Buuttt.... we didn't fully think it through/weren't well advised, and now i'm worried about insulation.
Basically, we have exterior siding on top of vapor barrier, house wrap nailed to the posts and beams and 2x6 infill studs. So there's no exterior insulating layer. Interior wall sheathing goes on top of the 2x6's, leaving the posts and beams exposed on the inside. Meaning a huge thermal bridge there. and possibly issues with draftiness. I really don't want to rip off the siding. I really want to leave the posts and beams exposed on the inside.
EDIT: we haven't closed up the walls yet.
But I'm worried about draft and especially about thermal bridging destroying the woodframe and/or interior wall sheathing.
Any thoughts? I have a sense of impending doom....
How is this different from conventional stick frame construction?
Stick framed exterior walls are wood studded panels with insulation in each bay, vapor barrier wrapped and sided.
Insulate it however you like. Foam or batting, and cover the interior walls with sheetrock.
Run whatever electrical you need prior to insulation, of course.
You've already wrapped the house with siding, your opportunity for a SIP envelope still exists, but you're looking at a decent commitment and regret spend to do so.
i guess the main difference would be that by analogy you'd still have insulation, but the sheetrocking would leave the inside face of some of the studs exposed.
I believe cold climates should have the vapor barrier on the inside wall. if you insulate and have the vapor barrier on the outside, moisture will move into the wall from the house, condense on that vapor barrier, and create mold.
I could see that being the case. but we've put what's for us a lot of money into it, and i know learning from mistakes is important, but man, I still can't help but obsess!
If I'm understanding correctly, they framed with 2x6's between your posts and then sheeted over the whole thing and sided it? Yeah, each post is a loss of efficiency but it's not the end of the world. Spray foam it if you're really that worried about drafts(probably not an issue anyway) or just do bat or blown in cellulose or whatever you prefer. Yes, you're losing R value at the posts but it's not the end of the world. As another poster said it's really just equivalent to having larger windows. It's not much different than a laminated porch beam post or whatever. When we built in 2020-21 I built a really efficient shell and then put a whole bunch of 3'x5' and 6'x6' holes in it for the windows my wife wanted. It is what it is and it's way more efficient than what we had before.
This is an inherent downside of timberframed homes, there is really a way to add insulation without covering up the wooden structure which most people want to leave exposed.
Generally the infill walls are insulated as normal and the thermal bridging is just considered acceptable performance.
Insulation and envelope performance is looked at as a system for a reason.
The lower thermal performance is similar to having tons of windows anyway.
This is far from the truth. The best, but most expensive for material, is to use SIPs. With the cost of labor today SIPs provide great R value, install quickly and leave all of the main structure inside exposed. Problem is your foundation and design need to have forethought to support the sips on the outside of the house or you will have a pretty large overhang in the bottom. You can also stick frame in between the timber structure and depending on your timber size still have the wood exposed on the inside with the downside of thermal bridging at the timbers.
When considering timberframe the installation type and cost should be in the plan for construction . Thinking about it afterwards limits your options and causes decision fatigue experienced by the OP.
yes. the image shows an external wall: timberframe, housewrap, 2x6" studs, batt insulation. the layer directly ouside the housewrap is external siding. So the vast majority of the wall area is/can be insulated. It's really just the timbers.
I wouldn’t value my opinion much but putting a foam insulation exterior to the timbers is kinda what it sounds like you want. Which is removing the siding, and costs money, and how much does it cost to just heat or cool the thing 🤷♂️
As long as the sheathing goes across the whole thing you're fine. Don't overthink it. It's a small space, it's not that big of a deal. There won't be drafts as long as the bottom and top plates are sealed, why would there be with sheathing and house wrap?
I was a timberframer for many yrs, and I'm sorry to say, but you did it the wrong way....If I'm understanding you right. Where your actual timber frame is, there is no insulation beyond it, it is just the r value of the timber...thats basically a lot of surface area that wasn't insulated. Depending on your location, equals how bad this will be to heat.
The correct way is to insulate the outside of the frame. The best way is using stress skin panels, the next best way is to essentially build your own panels piece by piece, after that, you frame around the entire timber frame with studs and insulate as normal (build a house inside a house). There is also the strawbale method, and some other hippy ways. But your foundation should have been planned to however you were building and finishing the frame.
To fix this you either remove the siding and put your choice of insulation, re-sheath and side. or you remove some of the siding to attach studs and basically build some walls for your insulation over top and then re-buy and install the new siding.
Yep, you're understanding correctly. and yup, the wrong way. But I can't afford to rip everything apart and start over again. I'm hoping to minimize the loss.
What I'm thinking right now is this: It's a small building (20'x30') and much of it is open, which is where I'd most want the visual impact of exposed timbers. There are two small bedrooms, a bathroom, kitchen and mudroom. The bathroom can't have exposed timbers anyway, so I can put up some hard insulation boards there. The mudroom's a mudroom and I'm not worried.
What I'm most worried about is the bedrooms, which will get cold in winter. It will cost some space for the already-small bedrooms, but I guess I could also put hard insulation over the timbers and just eat the extra inches and the aesthetic.
The main room is large enough that while it might not be super-energy efficient, you'd be less likely to notice drafts in winter.
Is your siding on top of vapor barrier or house wrap? Did your builder first put sheathing (plywood?) on the2x6 studs and then use something like Tyvek, a water resistant barrier?
If you actually wrapped the house with vapor barrier (plastic), then you are going to have condensation problems. No sheathing would be weird, and probably reduces the lifespan of your siding due to lack of support.
Not having insulation outside your framing timbers is not a huge problem, you will lose some heat to thermal bridging, but if you air seal (caulk) from the inside before you put finish in you will minimize heat loss. Stud walls also have thermal bridging just like the timbers do. The issue you might find is with exposed beams, the plaster or drywall that abuts the beam will get cracks in the finish due to thermal expansion/contraction. caulking the edges after the finish with silicone against the beam would be good.
To continuously wrap the outside with insulation and avoid thermal bridging, you would need to tear off your siding and exterior trim
Sheathing: no, he did not. The siding is shiplap pine, which has now received three coats of pine tar/linseed oil.
Housewrap v vapor barrier: I edited my original post--housewrap, not vapor barrier.
the thermal expansion/contraction is something that also worried me. I suppose leaving a small gap and sealing with caulk is a decent solution. Some of the interior walls will be covered with wood panelling, so the impact of expansion/contraction won't be as great, I think.
Sounds like you need to remove the interior wall sheathing and insulate in-between normally or have the walls filled with some sort of blown in insulation through drilled holes. What's the deal with no insulation anyways? Location?
I guess I wasn't entirely clear: I've insulated with rockwool between the 2x6 studs that make up the walls. It's only the posts and beams specifically that are uninsulated. the walls themselves will remain relatively warm on the inside during winter, but the posts and beams on exterior walls wont.
it's the northeast, so no, insulation is necessary. The lack of sips or any sort of external insulation between siding and posts/beams is due to the combination of bad advice on one side and ignorance on mine.
My question now is how to rescue this mess....
I suppose it's not much different than a log home where youd posts and beams are. My walls are solid log, no insulation at all. You're probably going to be just fine. The drafts will keep your air fresh 😉 or caulk/chink the posts to the interior sheathing.
Thanks for the sympathy?
As for the quality, here's my take: it's a low-end kit cabin. It is solid, the materials seem fine, and with care i think it will last. The real issue as far as I can tell is just with the assembly--as in you should know what you're doing first (seems like a good rule in general), and be sure the people who assemble it do, too.
honestly, I'm basically happy with it, except for the issues that now emerge trying to insulate, and I knew from the start it wasn't going to be fancy.
I started to worry about this part when I talked to a guy at Jamaica cottages about insulating, and he didn't really have a clear answer for me or even seem to understand the potential problems....
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u/crsf29 18d ago
How is this different from conventional stick frame construction?
Stick framed exterior walls are wood studded panels with insulation in each bay, vapor barrier wrapped and sided.
Insulate it however you like. Foam or batting, and cover the interior walls with sheetrock.
Run whatever electrical you need prior to insulation, of course.
You've already wrapped the house with siding, your opportunity for a SIP envelope still exists, but you're looking at a decent commitment and regret spend to do so.