Hello everyone,
I have already tried searching but couldn’t find the right information. Therefore, I kindly ask for your help with my questions.
I want to insulate our new "garden house" (1 workshop room with 2 windows, 6 square meters (65 square feet), 1 storage room, 4 square meters (43 square feet), each with its own door). The building rests on pier foundations with 10x10cm (4x4 inches) posts, 3 continuous horizontal battens, and overlapping larch wood cladding. The floor is paved.
1.) For the floor, I was recommended to build a substructure from KDI-treated wood on rubber pads. Directly on the paving, XPS boards should be placed, slightly lower than the substructure (to allow air circulation). OSB panels are planned to be screwed on top of the substructure as the floor surface.
2.) Due to space constraints, the walls and ceiling must be insulated from the inside. With conventional insulation using mineral wool, a vapor barrier would typically be required. However, since various mounting brackets/hooks will be screwed to the walls, I am concerned about damaging the vapor barrier. Therefore, I would like to insulate here using XPS as well. I plan to glue the XPS directly onto the cladding, in a similar way to the floor. Then, OSB panels would be screwed onto the existing battens/posts.
I now have the following questions:
Regarding 1.) Is an additional membrane or similar required beneath the substructure or the XPS boards?
Regarding 2.) My biggest concern is mold growth. It wouldn’t be a problem if it doesn’t get too warm and humid inside. Is there any issue with the planned wall and ceiling insulation using XPS? How much space should remain between the OSB panels and the insulation? Is ventilation behind the insulation necessary, or can the XPS boards be attached directly to the cladding?
Thank you very much!
Lasse
I have already tried searching but couldn’t find the right information. Therefore, I kindly ask for your help with my questions.
I want to insulate our new "garden house" (1 workshop room with 2 windows, 6 square meters (65 square feet), 1 storage room, 4 square meters (43 square feet), each with its own door). The building rests on pier foundations with 10x10cm (4x4 inches) posts, 3 continuous horizontal battens, and overlapping larch wood cladding. The floor is paved.
1.) For the floor, I was recommended to build a substructure from KDI-treated wood on rubber pads. Directly on the paving, XPS boards should be placed, slightly lower than the substructure (to allow air circulation). OSB panels are planned to be screwed on top of the substructure as the floor surface.
2.) Due to space constraints, the walls and ceiling must be insulated from the inside. With conventional insulation using mineral wool, a vapor barrier would typically be required. However, since various mounting brackets/hooks will be screwed to the walls, I am concerned about damaging the vapor barrier. Therefore, I would like to insulate here using XPS as well. I plan to glue the XPS directly onto the cladding, in a similar way to the floor. Then, OSB panels would be screwed onto the existing battens/posts.
I now have the following questions:
Regarding 1.) Is an additional membrane or similar required beneath the substructure or the XPS boards?
Regarding 2.) My biggest concern is mold growth. It wouldn’t be a problem if it doesn’t get too warm and humid inside. Is there any issue with the planned wall and ceiling insulation using XPS? How much space should remain between the OSB panels and the insulation? Is ventilation behind the insulation necessary, or can the XPS boards be attached directly to the cladding?
Thank you very much!
Lasse
I would say you can glue the XPS boards directly onto the formwork and then install the OSB panels in front of them.
Where would moisture come from in a workshop or storage room?
The formwork still lets enough air in from outside.
Why are you doing all this anyway? Hours of tinkering in winter?
I usually get quite warm while working, but otherwise, a fan heater should be enough to keep an uninsulated shed warm.
Where would moisture come from in a workshop or storage room?
The formwork still lets enough air in from outside.
Why are you doing all this anyway? Hours of tinkering in winter?
I usually get quite warm while working, but otherwise, a fan heater should be enough to keep an uninsulated shed warm.
Thank you for your reply. I’m always warm enough as well. The concern is only about the stored items, like power tools and paints, for example. Frost would be quite problematic.
And strangely, there is a rather high humidity level (~85%!) in the rooms. I wonder where it comes from; the only explanation I can think of is that it might be coming from the floor. In any case, the cardboard on a few boxes (which weren’t placed directly on the floor) became noticeably damp after just 2-3 weeks.
So, in short: lower humidity and no frost.
And strangely, there is a rather high humidity level (~85%!) in the rooms. I wonder where it comes from; the only explanation I can think of is that it might be coming from the floor. In any case, the cardboard on a few boxes (which weren’t placed directly on the floor) became noticeably damp after just 2-3 weeks.
So, in short: lower humidity and no frost.
1) Why do you want to insulate the cabin? Insulation does not heat the cabin; it only slows down the loss of heat already inside. So unless you install a heating system or plan to stay inside for 12 hours straight (body heat), insulation alone won’t make it any warmer.
2) To achieve any significant insulation effect, you first need to make the cabin airtight.
3) Leaving a ventilation gap between the OSB and the insulation makes the insulation ineffective. Heat will be carried away directly by the outside air before the insulation can prevent it (see point 2).
4) I don’t see the need to install a vapor barrier, as there shouldn’t be any significant moisture entering (see @apokolok).
I would save the effort and just install a space heater that you can turn on when needed. The money saved on insulation will likely be spent on higher heating costs for the lifetime of the cabin.
2) To achieve any significant insulation effect, you first need to make the cabin airtight.
3) Leaving a ventilation gap between the OSB and the insulation makes the insulation ineffective. Heat will be carried away directly by the outside air before the insulation can prevent it (see point 2).
4) I don’t see the need to install a vapor barrier, as there shouldn’t be any significant moisture entering (see @apokolok).
I would save the effort and just install a space heater that you can turn on when needed. The money saved on insulation will likely be spent on higher heating costs for the lifetime of the cabin.
Oh, then it’s great that I questioned the whole thing again... I’m not really keen on the work either. But the high humidity (see above) especially made me uneasy.
What else can I do about the moisture? Maybe just treat the floor with my XPS construction? I don’t know where else the moisture could be coming from. Or maybe add exhaust vents just below ceiling height? I thought the insulation would also reduce the moisture. Thanks.
What else can I do about the moisture? Maybe just treat the floor with my XPS construction? I don’t know where else the moisture could be coming from. Or maybe add exhaust vents just below ceiling height? I thought the insulation would also reduce the moisture. Thanks.
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