Stone foundation - dirt floor basement... insulation?
lil_geek
16 years ago
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scryn
16 years agoRelated Discussions
Basement Insulation: What to do wen exterior is insulated?
Comments (5)Not that I know of. But my thought is that the external insulation is so minimal--BSC and Building America recommend a minimum of 2"XPS for high performance in a cold climate--that the wall might still be cool. Plus there's likely extensive thermal bridging at the top and wicking up of moisture through the walls (unless there is insulation under the wall or a thermal break). If it were my home, I'd add at least an inch of high-R foam on the interior as well. And don't forget the rim joist area, either with foam board well sealed, or easier and surer, spray foam. Spray-foaming the rim joist area is an essential step in creating a healthy energy-efficient basement. Here is a link that might be useful: High R Value Foundation Assemblies...See More1870 house, stone foundation - what about the basement?
Comments (2)Before the mid-20th Century, basements were not looked on as potential living and dry storage places. However, limestone and rubble basements can be converted for such uses from the outside or from the inside. For one approach to inside insulation, waterproofing, see here. The efflorescence and visible dampness point to specific exterior issue that will have to be addressed. You just factor it into your price....See MorePlastic sheeting over basement dirt floor to combat moisture?
Comments (10)The intended purpose for laying down plastic is to retard the transmission of soil vapor (which is in almost all soils except in extremely arid areas, and inexorably rising due to changes in barometric pressure) from coming up into the basement space. The fact that you are using a dehu means that you have a perceptible soil vapor problem (at least that's why you are paying the electric co. to run the dehus, which is comparable to running an A/C, in some cases). Note however, that I said retard, not completely prevent the rising of soil vapor into the basement atmosphere. Nothing I know of will completely keep it out. Because we now have a goal of sealing up our houses in the name of energy savings (and have modern, and different, whole-house heating systems) rising soil vapor can get stuck within the building potentially causing damage to the structure or contents or residents, if mold develops. Of course your house, like mine, was built with long-tested systems that did not expect, or require, the house to be as hermetically sealed as we sometimes try for these days. In 1857 the vapor was a-rising just as it is today, but it was exiting the building much more easily. Two other factors: people lived and worked at home and were more likely to be aware of and able to adjust the basement openings during the day, promoting additional passive ventilation to remove the moisture. And they may have highly prized that very same moisture if they stored food in the basement. Of course they also didn't have nifty stuff like cross-linked plastic molecules made into cheap (if you don't take into account any off-stream environmental costs), easily laid-out rolls of plastic to put to use, either. Soil vapor is also coming from the basement's walls as your inspector noted. But blocking that moisture is as hard as, or harder, than blocking the soil vapor. If you had thoughts of converting your basement to modern uses (family room, media room, exercise parlor, etc.) you may be disappointed as this is rarely successful in old houses such as ours. So the remaining issue seems to be: how tight is the house above the basement, and how might that tightness be interfering with the house's natural ventilatory patterns. (I think of it as how the house is "breathing", albeit in a passive way.) And of course, it also depends how much more you may be planning to do, in the name of energy conservation, to further tighten up the house. You have run smack into one of the central dilemmas of old-house care: how do you integrate (without doing damage) modern building and energy standards with a structure that was designed and built to support a completely different system? Solving one problem can easily create a new, perhaps more difficult to manage, unforseen issue. There are many opinions and oxen-to-be-gored in this arena. As a practical matter, if you want to lay down plastic (though I recommend special-purpose materials intended for vapor retardation instead of construction poly) and can seal it well with tape where sheets are overlapped, and along the bottom of the walls, you can susbstantially reduce the amount of rising vapor within the basement cavity. But you should know there are some who posit that doing so will shift this moisture (perhaps with damaging consequences) to adjacent soil spaces, including under and in the immediate, exterior vicinity of your foundation walls. This (according to some) may super-saturate the soil, disturbing the necessary firmness and creating settling or susidence problems. Does it? I surely don't know, but it does create - over time - a very moist soil under the plastic. (You can test this by laying a yard-square scrap of plastic on the dirt floor and see what happens.) Others recommend various systems of forced, or air-pressure augmented passive ventilation to remove the moisture laden air from the basement before it can rise into house interior and replace it with (theoretically) drier exterior air. This method has the advantage of not monkeying around with existing soil mositure states, but it is complicated, and may take personal attention to adjust during each day and/or electricity to run. If you have just purchased this house, I think you should observe the ebb and flow for a while (at least a calendar year), as you think about this. And keep the issue in mind as you contemplate any further sealing and insulation projects. It sounds as though the dehus are keeping things in check, so nothing (except cost of power and fuss of removing condensate) is lost by taking a go-slow approach. And by all means, test for radon if you have it in your area. (Your local or state health department is a resource on this.) An upside of the necessary ventilation to control radon can be a reduction of basement moisture since the gas and at least some of the air vapor are removed at the same time....See MoreInsulating floors above dirt basement
Comments (4)I have the exact same setup. My living room, built in 1880, is over a fieldstone-walled, dirt-floor basement. I had the same problem when I first bought the house. Prior owners had foam board in places, and it wasn't air sealed, but I'll tell you, mice just LOVED creating homes between the boards and the ceiling of the basement/floor of the living room. It was disgusting. And when one would die, the living room just stank! I took them all down (it was a very, very gross job), cleaned the ceiling using tsp and bleach to sterilize it, and then a friend installed Roxol batting insulation on the ceiling using insulation wires to hold it. Roxol is non-toxic and rodents hate it, which is why I chose it, and it has been fantastic. Whatever you decide, I'd pick something that repels rodents. Foam board they can just chew right through to make a home. Ugh....See Moresharon_sd
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