Log home insulation advice…
My son has a 1990 built log home (from a kit) in climate zone 6. He has been there 2 winters, and although a nice house we are dealing with the energy issues inherent in this design. We have done small things like basement and rim joist insulation, caulking, etc, and have bigger plans for the future (about which I have gotten good advice from this site) when finances allow.
There are two bedrooms on the first floor with just the 8″ white pine logs for walls. That is only maybe R-10 (less counting leakage thru seams). We are thinking about adding rigid foam to the interior (1 or 2 inches, knowing 2 would be better), with sheetrock carefully applied over the rigid. This should certainly be good air sealing if not great added R value.
My main questions are: 1)what type of rigid board would be best, 2)is there a house wrap type paper or other that would be good under the rigid foam on the logs, 3)I have some concern about it getting cold enough against the interior logs to condense moisture (do I need to be?), and lastly, 4)what about attachment of foam and sheetrock in light of typical seasonal movement of the logs. From could be glued or tacked, but what then?
I know log homes have specific issues and are not necessarily the primary domain of this site, but I know there is great expertise here from both the experts and readers, and I’m hoping there is some direct experience with this type of retrofit. And I’d be happy to hear about other log home specific insulation ideas in addition to what has already appeared on this site.
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I build log homes. That said I inform everyone that they are not energy efficient nor an economical choice. The sales people always say the opposite and there is nothing anyone can do.
Best choice is to sell. No one wants to sell. Next best idea is to heat with wood stoves or pellet stoves and do the labor required to save costs for fuel so you can enjoy owning a log home that is not ever going to be worth converting to super insulated.
Urethane caulks are used often to chink machined logs inside and out. Sometimes we use clear silicone inside or even black or browns when caulking checks so the check still looks like a check which is a desired look. There are contractors that redo log homes and they do great work. Expensive depending on what one thinks is expensive.
I have built many log homes. I do not own one and at this point never will. They are a luxury home in my opinion though sold as being the opposite at least as to cost to own, build and heat and maintain. Especially those three. Maintenance is the highest of any home I build. Cost to construct is the highest. And cost to heat is by far the highest.
If you insulate the walls, caulk completely all the joints first. If you have flat inner logs faces, rigid foam, then drywall is fine, but we often just add T&G milled to the same width as the logs so after completion the wall still looks like logs, which is why the log home was bought in the first place. savings in fuel will mostly come from reducing air leaks in the walls the ceilings the rim joists and basement and doors and windows.
Good luck. Stay near the wood stove, and throw more covers on the bed.
Howard,
A.J. gave you some good advice. I hope that your son can sell the home to a buyer who likes log homes and can afford to maintain and heat one.
If you want to insulate the walls on the interior, air sealing is key.
You can build a 2x4 stud wall and insulate with spray foam. Or you can install one or two layers of rigid foam and drywall. (There are no condensation concerns with this technique.) Rigid foam works best if the interior side of the logs are sawn, co-planar, and vertical. If you have round logs on the interior, installing rigid foam will require fussy shimming.
To anyone thinking of building a kit log home. Try this. Go to Rescheck and run through insulation options for your log home. I have to in NY when submitting for a building permit in my county. I have run the numbers for two homes recently. Both passed at 0% above code by upping the insulation values far higher than code at the ceiling, basement, floor, doors and windows.
Also it now looks like logs have to be larger to even try to pass Rescheck. The last two had 10" and 12" logs and would not pass with smaller logs. Many of the kit log companies sell 6-8" logs and I built a quite a few years ago.
Last point, one of my log choices now has logs 14" and even much larger. But to go with large logs you have to have a much larger home for the logs to scale look wise and to actually not chew up room size. Very noticeable starting with 12" logs, the rooms have to be drawn taking into account the wall thickness especially if room partition walls are log. That all looks great when done right and also costs much more. IMO they are million dollar ski and snowmobile and hunting camps and that's it
Built for luxurious fun they are the great.
http://www.energycodes.gov/rescheck
Thanks AJ and Martin for really good advice. I had reservations about the log home from the get go, but not enough to try to talk my son out of it due to ideal property and location and other factors. Two previous families had lived there without much complaining about energy (though the 2nd was selling, so...). This was a Lincoln kit with logs milled like clapboard on the exterior and flat on the interior. They are flat top and bottom with 2 v-groove slots and a gasket, but still allows plenty of leakage. We do heat it with wood cut ourselves, so cost is not that bad but workload is. There is a high efficiency propane forced air furnace as an assist and backup. Neither my son nor I would ever build a log home if we were starting from scratch.
It seems like spray foam would be expensive and still allow thermal bridging at the 2x4's, whereas rigid foam would be continuous. And there is the additional loss of room space with this added thickness. Should I assume that house wrap is redundant or useless? And no one mentioned the connecting of foam and sheetrock vis a vis log movement. AJ?
My son has done a good bit of silicone caulking on the inside and this does help. The logs are milled flat on the inside, but hardly like a sheetrock flat as the logs curl a bit so there may still be some some shimming needed.
The kit sellers in 1990 probably thought this was wonderfully insulated with 12" fiberglass in the roof/ceiling (albeit with no air sealing). This will never be an especially efficient home to heat, but with improvements will have tolerable tradeoffs.
Howard, Unfortunately, because of the seasonal movement, it is best to build a completely independent wall on the interior of the logs and insulate that. It needs to be kept down from the ceiling with the trim at the top able to slip as the walls move. Using the drywall to air seal is almost impossible. A smart membrane is easier but still very time consuming to attach to the intermediate interior walls. As Martin and AJ have suggested, you really need to go into this with your eyes open. Most of the people I've met who have renovated log homes end up finding the work involved daunting.
Malcolm, an older Lincoln Log home does not have a lot of log movement. First of all, LL air dries the the rough sawn log cants for a year or more before planing. Second, my experience is that once we caulk with urethane the entire exterior and silicone the inside, then that is done for the time being including seasonal changes once the homes are a few years old. At five years old most start caulking. As the breeze through the wall is a bear when it's windy and -10.
New wet logs of large diameter shrink and the wall height drops if allowed to about 3/16" per foot. After six years a 12" log wall is down, time to stop adjusting the post jacks. The trim slip system was never part of Lincoln Logs kits years ago though should some of us built interior walls with a bit less height to try to guess that all would be at the same level in time. The more rustic less machined log kits are mostly using large diameter logs and like the ones from PA the logs are shipped sometimes just days after being cut from the forest. Can you say 100% wet, yes sir. I think I have actually almost seen a wet log wall shrink in height over just a week of early spring warm weather.
Anyway, the model for LL in Chestertown was one of the first LL kits to be fitted with interior T&G to cover lots of interior caulking to reduce air leakage that was severe on windy days making selling a kit somewhat difficult I would guess. Another problem all the kits had was selling T&G cathedral ceilings and not understanding how much heated air was flowing through and out the vented roof. Lots. I found out how much when I was in an attic above a cathedral and stood in front of a hot blowing wind of air exiting the top of the cathedral into the attic.
Howard. rigid foam over caulked logs, idea one. Idea two, open cell spray foam, Northeast Spray Foam is located near LL factory could blow that for you, talk to Doug. Open cell is flexible. if flex is needed. If you use 2x3s on the flat and shimmed them off the wall with 2x3 blocks top mid and bottom the foam could go under. You could cut foam shims for the length of the 2x3 might be best. Then finish with T&G to keep the look. One of the mills near LL used to plane T&G to the same width as the LL logs.
Where is the log home located?
I haven't built one since Stephenson Lumber purchased the company after bankruptcy. Lately I have built and designed a PA wet upon delivery shrinking wall home and cabin. Lots of tricks to the shrinking factor, slotted 2x4s slipping double top trim kits post adjusters and copper wraps... lions tigers and Adirondack bears and more.
Thanks, Malcolm. Can you share some details? If one builds an independent wall I suppose a 2x frame is the thing, possibly ripping wood to 2" (ie. 1.5 X 2 to reduce interior space impact) and using 2" rigid foam. That scenario would be the 'cut and cobble" method,- or do you think something else is better? Is the problem that screw holes will be pushed around, opening voids in the foam and sheetrock? That doesn't seem a huge problem for the foam, but probably is with the sheetrockCan you tell me more about attaching the inner wall and where? The floor (to joists or blocking) seems obvious and easy enough, but what about at the ceiling (same way?)?
A paper membrane does sound reasonable to attach, as it could be attached in a modest # of places around the edges with some slack to allow for movement. Do you recommend any particular membrane?
You are correct that this is a pain, but is what we have to work with.
Thanks again AJ for the options suggested. My son is willing to finish wall with sheetrock as there is plenty of other wood/log look elsewhere (the great room), so some saving of $ there. We have some interest in minimizing thickness of the interior add ons so would probably avoid rigid foam under the wood frame. More likely we would use cut and cobble with canned spray foam, or consider your open cell option in between the wood. This might allow some thermal bridging, but a trade we would take.
If one did the rigid foam on caulked logs without a frame, going with the notion that the house is now stable, would one then use longish sheetrock screws thru the foam into the logs? (I'd use minimum # of screws). It would seem the foam would need minimal attachment, -just tacking or gluing since it would be held on by sheetrock.
We are located in northern Vermont, minus 20 or so last night, coldest temp this winter by far. Weather you can identify with?
You don't have to cut and cobble. There is Dow foam made with a channel for wood strapping.
caulk all seams, corners floor and ceiling joint.
Add rigid foam with strap nailers, 1.5" foam uses 3/4" strapping
seal foam all around edges, tapes caulks, can foam... they all have to not melt foam, so read for compatibility.
Nail up your drywall and seal the edges of that too.
add your trim back and seal it... clear caulk works great where you have to be careful that it may show.
Seal up the whole home. Great time to get a blower door test done and pay to take the time to find all the air leaks. Well worth the cost. Worth more than your wall insulating. Have caulks and can foam ready to use.
There is no need to worry about the logs moving. Maintenance for log homes never ends. Just keep the woodstove going and sleep near it when it -20 like the rest of us do. Grab the futon off the couch and toss it down.
If you have a T&G cathedral ceiling you are losing heat through that by the thousands of BTUs. You can go nuts with clear silicone and hit the joints. All labor, not a lot of cost for the gain.
Howard, I missed the reference to it being a Lincoln Log house with squared timbers. That simplifies things considerably. As AJ says there is less seasonal movement or concern with uneven log widths. I'd do as AJ suggests in post 9.
We will check out the Dow foam with the channels for furring. Sounds like a useful product, and thanks for the details on application. We are well aware of the cathedral ceiling issue. We have talked about the foam over fix when re-roofing, having gotten most of the details from this site. This is a big and expensive job and will have to be a couple years off. The shingles are original so their time is nearing.
It seems the exterior roof fix is better than anything that can be done from the inside. I don't think more than 2" of foam could be added on the inside, as opposed to the required 5 - 6" outside. The inside fix would require either taking down and reusing the T&G boards, or going over them and repurchasing at considerable expense, -but it sure would be nice to have effective air sealing inside.
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Martin: your comments in #2 indicate moisture condensation behind the foam and against the logs would not be a problem. I'm glad to hear this and value your knowledge, but hope you'd be willing to explain why this is the case, since I have read elsewhere a belief that this can be a problem. It is certain that this area would remain very cold in the winter, -more so after the insulation isolates the inner log from the home's warmth. Is it that the air sealing done well prevents any moist air from entering that area? And would there be no concern of inward migration in the summer?
Howard, if moisture is a concern, use unfaced EPS.
By the way, we added drywall walls to LL homes for the kitchen cabinet wall many times. The company never said customers were having problems. Wood can hold a lot of seasonal moisture.
Anyway, if you are concerned do one wall first and see what the results are and if you get any desired change or worse.
Rim joists, blower door work, the cathedral are all much more important areas to deal with then the wall. Windows, you can buy low E added glass,
Better option is to enjoy four months in Florida for less cost than converting a LL to superinsulated.
Put some wood in the woodstove and enjoy the outdoors. I love skiing at Jay Peak off trail. Jay is the place to be in your part of VT... Stowe, Mad River, Sugarbush, the sailplane port... Church Street in Burlington...
AJ; Moisture is not a particular concern if it doesn't need to be. The house has fairly low humidity, but that might not always be the case in the future. Martin provided some relief in stating that moisture would not be an issue, - I just wondered what the principle was that had him feel this way. We know the LL home will never be high efficiency, but we are still seeking out reasonable cost improvements to reduce wood use (and some propane). It's just a challenge deciding which efforts are best and how to go about executing them, avoiding mistakes, so thanks again for your helpful advice. We will do something with the cathedral ceiling, but are still deciding what. We know the exterior foam, -5" of it would be a best fix, but outrageously costly, largely for that amount of foam. We are thinking about interior fixes for the ceiling as well.
Howard, I see that this thread is about 5 years old. I hope that you still get this. I am in exactly the same situation as your son was 5 years ago, and am thinking about doing exactly the same fixes. I would like to hear what you decided to do, and with what results. I am in Irasburg, VT, so we are probably neighbors.