Hey everybody,
We live in an old log cabin in Central Sweden (Dalarna). So climate is long, cold, dry winters (down to -20 celcius snow on the ground from November -> April), and short mild summers. Climate here is quite dry although heavy rains in summer.
The cabin itself is about 150 years old and built in the scandi style, the original chinking is moss and plant matter. A conventional roof (10 x 2 rafters / roofing felt / metal cladding) was put on in the last 30 years (at a guess).
When we moved here the walls had been insulated internally with mineral wool between stud work, and the same between the rafters. Last winter was coooooold. The walls are extremely leaky, and the insulation had been compromised by decades of mice and squirrel activity.
This year I have been renovating the upstairs of the house, which is room in roof construction. So far I’ve replaced the insulation in the separating floor, have chinked with expanding foam, and filled in any gaps with expanding foam and wire mesh (for the pests).
I’m currently insulation between the rafters with 150mm PIR (0.022 w/m2k), leaving a 25 - 50mm air gap above. At the eaves on the internal side there is a chipboard barrier separating it from the external eaves / soffits / fascia, so I’ve sealed around there and fit ventilation grilles with insect mesh.
Next job is to insulate and line the internal walls. My plan is to erect a 2 x 4 studwall tied to the floor and rafters, with 100mm PIR between the studs and 50mm PIR over the inside face. Then plasterboard and skim.
This will leave a residual cavity between the stud wall and log walls of between 25 - 75mm (the walls are really not straight, level, or plumb).
Anyway my question is, should I seal off this cavity? or should I attempt to ventilate it? Should I be fitting a vapour barrier on the inside of the stud work? I was planning on fitting a vapour barrier on the ceiling over the insulation, but I’m a bit unsure when it comes to the wall construction.
Side note: I’m not interested in gains from the thermal mass of the logs. The house is located in the woods in a shaded spot and doesn’t receive masses of sun in the period when it would need it for this to help. That might work in milder climates but here in Sweden then the walls -need- to be insulated, and external insulation isn’t an option.
Side side note: the heating is combination of wood burner and electric. The wood burner provides most the heat (in this part of the house) and is on almost everyday from September - May. The chimney stack runs up through the centre of the space in question. Downstairs is living / dining room (kitchen / bathroom is in different non-log part of the house)
I’d really appreciate any help as log cabin construction seems a lot more niche then more conventional styles and it can be difficult to find information that’s specific to it. Thanks :) |