ᐅ Adding a dormer to a hipped roof using timber construction – which insulation is best?
Created on: 21 Sep 2017 09:32
D
deifelHello everyone,
We are currently planning to add an additional story to our hipped roof bungalow and have already worked out some plans with our architect. According to this, we will be building the extension using a timber frame construction. The carpentry and painting contractors have completely different opinions regarding the insulation—both for the insulation between rafters and for the exterior walls and roof.
This makes it harder for us to form our own opinion. Therefore, we would appreciate any tips you can provide. I will summarize the options:
For insulation between rafters in the walls and roof, mineral wool or blown-in insulation seem to be the main options. Some contractors completely reject blown-in insulation, while others consider it the best choice. Our architect’s view is that if the walls, etc., are open, mineral wool should be used since it is an established and transparent method. With blown-in insulation, you cannot be sure if it has been installed fully and sealed everywhere... The same applies to the roof.
For the exterior walls, some timber frame contractors recommend wood fiber insulation boards. Others, such as painters, argue that this is not necessary and that polystyrene would be a better and more cost-effective choice. The structure of the exterior walls, from inside to outside, looks as follows:
Plasterboard walls
18mm (0.7 inch) OSB
Substructure
Vapor barrier
18mm (0.7 inch) OSB board
16cm (6.3 inch) structural timber
40mm (1.6 inch) wood fiber insulation boards, plaster base
Plaster
Are wood fiber insulation boards really the better choice here, or should we consider alternatives like polystyrene?
We are also not yet sure whether we should insulate our ground floor (masonry). It might make sense since the scaffolding will already be in place and this would give us a uniform facade. Are there generally any issues with the transition between the masonry ground floor and the timber frame construction? So far, this has always been denied, but I have also read different opinions online.
Many thanks in advance for your help!!!
Frank
We are currently planning to add an additional story to our hipped roof bungalow and have already worked out some plans with our architect. According to this, we will be building the extension using a timber frame construction. The carpentry and painting contractors have completely different opinions regarding the insulation—both for the insulation between rafters and for the exterior walls and roof.
This makes it harder for us to form our own opinion. Therefore, we would appreciate any tips you can provide. I will summarize the options:
For insulation between rafters in the walls and roof, mineral wool or blown-in insulation seem to be the main options. Some contractors completely reject blown-in insulation, while others consider it the best choice. Our architect’s view is that if the walls, etc., are open, mineral wool should be used since it is an established and transparent method. With blown-in insulation, you cannot be sure if it has been installed fully and sealed everywhere... The same applies to the roof.
For the exterior walls, some timber frame contractors recommend wood fiber insulation boards. Others, such as painters, argue that this is not necessary and that polystyrene would be a better and more cost-effective choice. The structure of the exterior walls, from inside to outside, looks as follows:
Plasterboard walls
18mm (0.7 inch) OSB
Substructure
Vapor barrier
18mm (0.7 inch) OSB board
16cm (6.3 inch) structural timber
40mm (1.6 inch) wood fiber insulation boards, plaster base
Plaster
Are wood fiber insulation boards really the better choice here, or should we consider alternatives like polystyrene?
We are also not yet sure whether we should insulate our ground floor (masonry). It might make sense since the scaffolding will already be in place and this would give us a uniform facade. Are there generally any issues with the transition between the masonry ground floor and the timber frame construction? So far, this has always been denied, but I have also read different opinions online.
Many thanks in advance for your help!!!
Frank
I am not quite sure why you mention the aspect of a hip roof so prominently. Is the extension not supposed to be a linear raised reconstruction of the existing roof, meaning inserting a new floor with straight walls in between, but rather involve altering the roof shape? I do not see how this would differ from extending a gable roof.
How advisable it is to insulate the existing ground floor depends on its wall construction. I would not recommend plastering the entire structure seamlessly together when different building materials are involved. Basically, adding extra stories is a routine procedure for prefabricated house manufacturers, both on their own buildings and on masonry constructions, and both with references. This, of course, does not change the fundamental inhomogeneity.
What was the motivation for choosing timber frame construction for the extension?
Batt insulation is stapled on; blown-in insulation tends to settle.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
How advisable it is to insulate the existing ground floor depends on its wall construction. I would not recommend plastering the entire structure seamlessly together when different building materials are involved. Basically, adding extra stories is a routine procedure for prefabricated house manufacturers, both on their own buildings and on masonry constructions, and both with references. This, of course, does not change the fundamental inhomogeneity.
What was the motivation for choosing timber frame construction for the extension?
Batt insulation is stapled on; blown-in insulation tends to settle.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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