Replies

1. 
   charlie_sullivan | Jan 21, 2019 03:46pm | #1

   Can you tell use more about the sheathing ("wall boards")? Is is old style pine boards, or is it plywood? Or modern OSB?

   You might want to use a peel and stick membrane, as that seems to me to result in better air sealing than an unadhered membrane. But I'm not up on the different options for peel and stick membranes, as far a vapor permeability.

   How high your summer humidity gets is one consideration as to whether there's any reason not to use a vapor tight layer there.

   For siding, if you have a local source of rough sawn cedar, that would be my first choice. But that might not be an option.

2. 
   Kevin_Hiebert | Jan 21, 2019 05:10pm | #2

   It's 115 years old so it's dimensional lumber for the framing and 3/4" boards on the outside of that. It'll be very dusty under the old siding and I'm not sure we'd have good adherence without a lot of surface prep. But it might be worth it. I've looked at Adhero but never used it before.

   Humidity isn't a big concern here and air conditioning is common but not universal. Which raises the question of heating system. The existing hot water radiant heating system could be revived with the installation of a new boiler but then we'd want to add a separate cooling system. Might be better off to install a multi-head air-source heat pump that would cover both heating and cooling.

   If we found a local source of cedar, is there a low maintenance finish you'd recommend?

1. 
   Aedi | Jan 21, 2019 06:44pm | #4

   The only low maintenance finish for cedar is burning it. You can search Shou Sugi Ban for more info on the technique.

   In my research, I have heard that if you burn it deeply and don't mind the natural greying as it ages, you don't need to maintain it at all and it will last several decades -- I've heard claims of 100 years, but that is hard to verify. Most people seem to go for a more shallow burn and brush it so the lighter grain peaks through the charring; such finishes require oiling every few years, but I'd assume less often than unburned wood.

3. Expert Member
   Akos | Jan 21, 2019 06:02pm | #3

   Kevin,

   I would second the peel and stick, much easier to work with over something with a lot of gaps like board . I've had no issues installing over 100 year old tongue and groove, I did use a primer though.

   Another option would be to install a layer of rigid insulation and tape the seams. A bit more cost then the peel and stick but at least you would get some R value for the cost. If you insulate or even partially insulate your existing wall plus the exterior rigid insulation, you can probably reduce the thickness of exterior trusses, might be able to go with something like a TJI instead of making the trusses (less make, more buy). For partial insulation in service cavity I like Roxul's AFB as it comes in 2.5" thickness leaves lots of room for fishing wires in the future. Better then leaving an empty cavity.

   Depending on the size of the house and how air tight you can make it, you might be able to heat it from a high BTU hot water tank. All you would need to add is a plate heat exchanger two pumps and expansion tank added to the DHW heater to revive the existing radiant (this works well if your tap water is not very hard).

   No such thing as a low maintenance wood finish. All need some TLC sooner or later.

1. 
   charlie_sullivan | Jan 21, 2019 09:43pm | #5

   In principle I like the idea of taped foil-faced insulation as an air barrier with bonus R-value, but I'm not sure what you are thinking as far as how that works with the trusses or TJIs. Do they mount to the surface of the foam? Maybe that's simpler and sturdier than I am imagining, especially if it's only 1" foam. And I guess if you are making your own trusses the strip that bears on the foam could be wider than 1.5" if necessary.

1. Expert Member
   Akos | Jan 22, 2019 09:37am | #6

   Charlie,

   Foam is very hard to compress with a flat piece of lumber no matter the thickness. You can surface mount the TJI's the same way you would do strapping for a rain screen. Wider flange might be easier to work with but I don't think it matters much.

4. 
   Kevin_Hiebert | Jan 22, 2019 11:22am | #7

   It's sounding like a peel-and-stick barrier is the way to go in this case.
   If I tried to mount the Larson trusses over the foam I would have a tough time fastening them firmly enough to support the weight of the siding.

5. 
   Kevin_Hiebert | Jan 22, 2019 12:33pm | #8

   Seeing what's available locally, it'll probably be Blueskin VP100 for the air barrier.
   One less variable to worry about.