Insulating Floor from Below in Crawl Space – Material Choice to Avoid Moisture

[Sorchen]

Hello!


I am planning to insulate the floor from underneath in the crawl space and would appreciate some input from those of you with experience. The reason is that the floor is too cold in the cabin, especially in the transition between the old timber and an older outdoor/indoor section. I haven’t done a job like this before, so I'm looking for specific product tips (brands/product names) that I can Google and read more about – I plan to do the work myself but want to choose the right materials and method from the start.


Conditions:

• Crawl space with about 80-100 cm ceiling height, fully accessible
• Old timber house, walls are additionally insulated
• Extra cold particularly in the transition between the timber part and an older outdoor/indoor section
• Floor structure (from top to bottom): tile floor, underfloor heating, sawdust, hardboard, and boards supporting the structure

What I’m considering:

1. Method – the best way to mount insulation from below against the boards/beams? Battens and boards, or are there better solutions for such a low crawl space? Especially interested in how to solve the transition between the timber part and the old outdoor/indoor section, where it is often difficult to make a good connection. Preferably specific products for fastening/fittings too, like what you buy at Beijer/Bauhaus/XL-BYGG.
2. Material choice – I want to avoid making the construction too tight so that condensation/moisture forms in the floor. Given that there is already sawdust in the structure, I am a bit worried about moisture migration if I choose the wrong insulation. I believe more in allowing the construction to breathe rather than sealing it completely – is windproof paper something to consider here, or are there better alternatives for this type of floor? What do you recommend for an old house like this – mineral wool, cellulose, or something else? Are there specific products (e.g., a certain type of boards or loose-fill insulation) that work well in a crawl space without trapping moisture?
3. Mice – we have a cat that keeps mice at bay above ground, but in the crawl space, she obviously can't reach them as well. Are there insulation materials that mice dislike building nests in, or is it mostly a question of sealing and barriers regardless of material choice? Tips on pest-proof solutions/products (mesh, sealing strips, etc.) are welcome.

I’m a beginner at this, so links, image examples, and “how-to step by step” are greatly appreciated. Thanks in advance!

 

[Sorchen]

Hello!


I am going to insulate the floor from underneath in the crawl space and would appreciate some input from those of you with experience. The reason is that the floor is too cold in the cabin, especially in the transition between the old timber frame and an older outdoor/indoor part. I haven’t done this kind of job before, so I'm looking for concrete product tips (brands/product names) that I can google and read more about — I plan to do the job myself but want to choose the right materials and method from the start.


Conditions:

• Crawl space with about 80–100 cm ceiling height, fully accessible
• Old timber house, walls are additionally insulated
• Extra cold just at the transition between the timber part and an older outdoor/indoor part
• Floor construction (from top to bottom): tile floor, underfloor heating with water pipes, sawdust, masonite, and boards that support the structure

What I am considering:

1. Method — the best way to mount insulation from underneath against the boards/joists? Battens and boards, or are there better solutions for such a low crawl space? Especially interested in how to solve the transition between the timber part and the old outdoor/indoor part, where it’s often difficult to achieve a good connection. Preferably concrete products for fastening/beams too, like what you buy at Beijer/Bauhaus/XL-BYGG.
2. Material choice — I want to avoid making the construction too tight so that condensation/moisture forms in the floor. Considering that there is already sawdust in the construction, I am a bit worried about moisture movement if I choose the wrong insulation. I believe more in the construction being able to breathe rather than being completely sealed — is breather paper something to consider here, or are there better alternatives for this type of floor? What do you recommend for an old house like this — mineral wool, cellulose, or something else? Are there specific products (e.g., a certain type of boards or loose fill) that work well in crawl spaces without trapping moisture?
3. Mice — we have a cat that keeps the mice in check above ground, but in the crawl space, she obviously can’t reach them as well. Are there insulation materials that mice dislike building nests in, or is it mostly a question of sealing and barriers regardless of material choice? Tips on pest-proof solutions/products (mesh, sealing strips, etc.) are welcome.

I am a beginner at this, so links, image examples, and "step by step" guides are really appreciated. Thanks in advance!

Forgot the picture: