Crawl spaces are often talked about as a risk construction. A basement is preferred instead.
What I'm wondering then is:
In what way would a crawl space, for example, built directly on cleaned bedrock with a cast footing and masonry blocks, be worse than an old unheated basement?
If all these old houses with, sometimes even damp, "scary basements" manage without moisture problems and mold in the joists, why wouldn't a crawl space as described above manage just as well?
What is the difference like?
What I'm wondering then is:
In what way would a crawl space, for example, built directly on cleaned bedrock with a cast footing and masonry blocks, be worse than an old unheated basement?
If all these old houses with, sometimes even damp, "scary basements" manage without moisture problems and mold in the joists, why wouldn't a crawl space as described above manage just as well?
What is the difference like?
One must differentiate between outdoor air-ventilated crawl spaces, like the traditional "torpargrund," and warm crawl spaces that are ventilated from the inside. The latter behave like basements. When I refer to crawl spaces henceforth, I mean the first type. Older crawl spaces functioned through significant heat leakage from above. With today's requirements for insulation of floor structures, crawl spaces become too cold. This is significant during certain seasons when it becomes colder in the crawl space than outdoors. Warm and humid air entering through the vents causes condensation on the surfaces in the crawl space.
Older types of basements, with walls made of concrete block and uninsulated concrete floors, function well as long as the temperature in the basement remains around 16 degrees, and organic materials have not been used on the floors, walls, and ceiling. A modern well-insulated basement is like any living room.
A crawl space is a risk construction with today's energy standards. Few also build uninsulated basements today.
Older types of basements, with walls made of concrete block and uninsulated concrete floors, function well as long as the temperature in the basement remains around 16 degrees, and organic materials have not been used on the floors, walls, and ceiling. A modern well-insulated basement is like any living room.
A crawl space is a risk construction with today's energy standards. Few also build uninsulated basements today.
But if you take a 220 mm floor structure, for example, which is common today, and insulate it to that thickness while installing underfloor heating, shouldn't it be comparable to an old poorly insulated floor structure that leaks heat down to the basement? Because the underfloor heating should leak a little, right? And at the same time dry out the floor structure, which is actually the only organic part that could be attacked by mold in such a crawl space.J justusandersson said:
And then you have it unventilated, i.e., warm humid air doesn't flow in through vents. In the summer, the underfloor heating is indeed turned off, but then it's fairly warm, so the air shouldn't condense on the surfaces in the crawl space.
Though maybe it's not that simple? It just seems like there are a lot of old basements that are uninsulated and cold, where you might also have a laundry/drying room and possibly even a shower, which add moisture to the space. Despite this, the mid-floor structure is fine.
Because, after all, it's the mid-floor structure that is the sensitive point. Everything else is stone, concrete, and leca/brick, i.e., inorganic.
It's precisely warm, humid summer days that are the problem. If you have rocks in the crawl space that are cold and cool the air there, you'll get condensation.
A modern insulated floor structure with underfloor heating should not leak much and there is no point in comparing it to an old crawl space. You can simply measure and see if the crawl space is warming up (which it shouldn't).
One way to handle an old crawl space is to heat it to achieve the same conditions as before; it costs energy, but it did before too. A better way in many cases is to seal it and dehumidify.
A modern insulated floor structure with underfloor heating should not leak much and there is no point in comparing it to an old crawl space. You can simply measure and see if the crawl space is warming up (which it shouldn't).
One way to handle an old crawl space is to heat it to achieve the same conditions as before; it costs energy, but it did before too. A better way in many cases is to seal it and dehumidify.
Completely OT but how is your "crawl space" going tommib?tommib said:
Well thanks, I was down there today digging a bit. Mostly because it's cool and nice, and also because the kids wanted to go down. Progress is very slow, mostly due to work and other renovations. Right now, we're in the process of tearing down half of the upper floor, so that's taking up most of my vacation. I'll try to post an update eventually.
Yes, but condensation on what? Condensation on the rock doesn't matter, just as little as if it happens on the masonry foundation. The only place it can damage is the joists that are facing upward. If Isodrän, for example, is installed under the entire joist structure, it should insulate without trapping moisture (since it has draining properties). Wouldn't that be enough?
Or clad the joists with something else that tolerates moisture?
If there is no organic material down there at all, then it's probably not a problem. However, I would not start experimenting with alternative methods without carefully monitoring the results. There are established methods for handling a crawl space.
What if it's completely clean in the crawl space with washed rock as a base? Concrete footing around and lecablock? The only organic left is the floor structure that is the "ceiling" in the crawl space.
This is what I found on Isover:
"When you insulate the floor structure from below, you avoid ruining the room's floor. At the same time, the wood is protected by placing insulation on the underside of the floor structure. The floor structure simply gets a higher temperature. The prerequisite for being able to insulate the floor structure from below is that there is enough space in the crawl space."
Source: https://www.isover.se/isolera-golv-och-golvbjalklag-fran-krypgrunden
It doesn't become a warm foundation, but the floor structure should still stay quite warm, right? Then one should actually be able to skip the insulation between the beams and insulate under the beams all the way, so it should maintain approximately the same temperature as the floor inside, especially if there's floor heating. Or?
Moisture occurs in three different states, which is significant for how it is transported. Solid form: ice, liquid form: water, gaseous form: water vapor. Air can bind water vapor, how much depends on its temperature. The water vapor in the air is often the biggest problem because it can move in all directions and penetrate materials, condensing there. Moisture in the form of water, for example in a laundry room, is easier to control.
Perhaps the best option is to convert to a warm foundation... it probably shouldn't cost significantly more either if you just insulate the sole and the foundation well? Like 2x100mm Isodrän...