Takisolering av trähus
Hello,
I am in the process of buying a house in northern Sweden (near Arvidsjaur). The house is a log house from the late 19th century that was later expanded and used as a summer house. My intention is to renovate the property and turn it into a year-round residence.
I plan to insulate the walls externally with wood fiber as well as the roof and I'm trying to decide whether to build ventilation and insulation layers on top of the roof or underneath from the inside.
An Arvidsjaur resident who also owns a log house recommended keeping the existing tin roof because the quality of older panels is much better than modern counterparts.
I saw a suggestion that the battens, insulation and vapor/ventilation layers could be built on top of the existing sheet metal roof, with screws going through it into the wood underneath, with a newer sheet metal roof as a final outer layer.
Is this correct or does the existing sheet metal have to be removed first? Are there any advantages or disadvantages to choosing to insulate on the outside rather than the inside (apart from saving space inside)?
I don't want to accidentally introduce a design that will damage the house in the long run.
Thanks in advance,
Andy
I am in the process of buying a house in northern Sweden (near Arvidsjaur). The house is a log house from the late 19th century that was later expanded and used as a summer house. My intention is to renovate the property and turn it into a year-round residence.
I plan to insulate the walls externally with wood fiber as well as the roof and I'm trying to decide whether to build ventilation and insulation layers on top of the roof or underneath from the inside.
An Arvidsjaur resident who also owns a log house recommended keeping the existing tin roof because the quality of older panels is much better than modern counterparts.
I saw a suggestion that the battens, insulation and vapor/ventilation layers could be built on top of the existing sheet metal roof, with screws going through it into the wood underneath, with a newer sheet metal roof as a final outer layer.
Is this correct or does the existing sheet metal have to be removed first? Are there any advantages or disadvantages to choosing to insulate on the outside rather than the inside (apart from saving space inside)?
I don't want to accidentally introduce a design that will damage the house in the long run.
Thanks in advance,
Andy
Hi Andy
Warning! A wall of text will follow.
In general it is much better to insulate on the outside, but obviously the exterior will change. So, a lot of thought and effort should be spent on how to minimize those changes and keep the look, incl proportions and material and details, as close to the original as possible.
The most important thing to keep in mind and at any cost avoid, is the risk of moist in the construction. Due to our cold climate all houses must be protected from it. Unfortunately the moist comes both from the outside as well as from the inside, and on top of that the risk of moist issues increases with the insulation thickness.
To protect the construction from internally generated moist all houses built for the last 50 years have an internal layer of plastic film to stop the moist from getting into the insulation.
The original tin roof can function as such a moist proof layer, if it is in good shape and airtight. Maybe it needs some extra care around the chimney and any other possible throughputs such as ventilation ducts and roof hatches.
As for the external roofing, there always needs to be an ventilation layer/duct directly underneath. For a tin roof there will always be condensation due to temperature changes more or less every day year around. That moist needs to be able to ventilate to the outside. Also, with more hefty/rapid temperature changes there is a lot of condensation so a moistproof roofmaterial underneath is required to handle it. For external roofs with roof tiles this is even more important. Thoose roofs do not have a problem with condensation, but they are not so watertight so rain and snow gets in to some degree, especially in combination with wind.
There is of course much more to say but these general comments will do for now. Now need to make anyone comatose from hitting a wall of text. 😳
Adding a picture, (honestly stolen from https://info.rockwool.se/sv/isolera-ratt/nybyggnad/takkonstruktioner/), which describes the principles in an universal language.
Warning! A wall of text will follow.
In general it is much better to insulate on the outside, but obviously the exterior will change. So, a lot of thought and effort should be spent on how to minimize those changes and keep the look, incl proportions and material and details, as close to the original as possible.
The most important thing to keep in mind and at any cost avoid, is the risk of moist in the construction. Due to our cold climate all houses must be protected from it. Unfortunately the moist comes both from the outside as well as from the inside, and on top of that the risk of moist issues increases with the insulation thickness.
To protect the construction from internally generated moist all houses built for the last 50 years have an internal layer of plastic film to stop the moist from getting into the insulation.
The original tin roof can function as such a moist proof layer, if it is in good shape and airtight. Maybe it needs some extra care around the chimney and any other possible throughputs such as ventilation ducts and roof hatches.
As for the external roofing, there always needs to be an ventilation layer/duct directly underneath. For a tin roof there will always be condensation due to temperature changes more or less every day year around. That moist needs to be able to ventilate to the outside. Also, with more hefty/rapid temperature changes there is a lot of condensation so a moistproof roofmaterial underneath is required to handle it. For external roofs with roof tiles this is even more important. Thoose roofs do not have a problem with condensation, but they are not so watertight so rain and snow gets in to some degree, especially in combination with wind.
There is of course much more to say but these general comments will do for now. Now need to make anyone comatose from hitting a wall of text. 😳
Adding a picture, (honestly stolen from https://info.rockwool.se/sv/isolera-ratt/nybyggnad/takkonstruktioner/), which describes the principles in an universal language.
Fantastic, thanks Oldboy.
On our roof we've got the internal wood boards the outer metal is screwed to. The house has had a leak around the chimney previously so I've got to replace some of that anyway. Would you put the moisture proof layer before the wood boards?
If we're going with wood fibre insulation, am I right in thinking we'd need a breathable moisture barrier so the wood fibre can release any moisture?
On our roof we've got the internal wood boards the outer metal is screwed to. The house has had a leak around the chimney previously so I've got to replace some of that anyway. Would you put the moisture proof layer before the wood boards?
If we're going with wood fibre insulation, am I right in thinking we'd need a breathable moisture barrier so the wood fibre can release any moisture?