Adding exterior basement insulation
 

I've been thinking about adding basement insulation since I've been monitoring my basement temperature for the dryer heat recovery system. I've noticed it sways a lot more than I'd like to see. In the morning this winter it starts off in the high 40s, and during the day usually gets up to the very low 50s. While this is probably good for the freezer down there, its not so great for the furnace or the water heater, and it also makes for very cold floors! So, I've been thinking of insulating the basement. Since it is already quite small, I think I would like to insulate the exterior. Yeah, this would involve digging all around the house and putting in rigid foam board. However, doing it on the outside will allow me to fix any drainage problems that will show up this spring. It would also cover up the exposed field stone that is above ground, but below the siding. I'd really like some input and ideas to get me thinking more about this.

Good idea. Houses lose a shocking amount of heat thru floors, slabs, and foundations. We tend to focus on the attic and forget the bottom end.

Have you studied frost-protected shallow foundations? Standard construction technique in northern Europe, and catching on in North America. The idea is to provide a foam 'tutu' around the whole house, keeping cold air and water away from the footings or basement walls. Much more effective than gluing foam flat to the wall, because it creates a conditioned space around the whole building. And you don't have to dig as deep. Helps with drainage issues at the same time.

If you can swing it, I'd advise digging about 30" deep all the way around. Glue blue foam to the vertical foundation, then a 4'x8' sheet of 2"t foam as your tutu. It should slope down an inch or so; placing perf pipe and gravel at the outer edge will help carry off any extra water, if you have someplace to carry it off to. Squirt foam the tutu-to-wall seam, and leave 1/4" between panels so you can squirt foam those seams too. If you really want waterproofing, you can apply 'Ice&Water Shield' membrane to the vertical foam and lap it over the wall/tutu joint.

One down side is the difficulty planting foundation shrubs; but if you go down 30", you should be fine. Both my house and shop are on SFPFs; the footers sit less than 2' deep. You still want a good surface grade to move water away from the house quickly. Won't kid you, tho -- it's a big job!:D

I'm bumping this thread because I heard Ryland is thinking about doing the same thing and I'd like to know how he is planning on going about this. :)

If you're going down, why not go down all the way then? Put in the whole weeping tile set up and properly seal the outside wall. Get the whole drainage system going, that way it will keep your basement that much dryer for that much longer. Gives it that extra protection.

I agree Higgy. I'm just wondering what he all has figured out? What machinery would be good to rent, amount of insulation to use, etc.

I did something like this on my parents house, their foundation walls have about 2 feet exposed above ground, so I dug down just over two feet all along the house so I could put 4x8 foot sheets on the foundation walls, and a bit over a foot wide strip at the bottom (was working on this alone or I would have gone farther out), I could have gone straight down on their house, all the way to the footing but then I would have had to rent an earth compactor and compacted the soil as I back filled it, it took me just over two days to dig by with a regular shovel, in clay soil and I filled a wheel barrow with bricks that were used as fill in the soil.
On my own house I plan to get a keg of beer and ask people to show up with shovels (keg gets tapped after the work is done), plan again is to go down about two feet, this time going out farther (because I'll have help this time) and lay a full 4x8 foot sheet out flat to make the above noted Tutu but I'll most likely use two layers of 1.5" foam and stager the seams so I get a total of 3" and the only seam I have to worry about is the transition from flat foam to upright foam.
on the one side of our house we also have a drainage problem, my plan is to dig a trench at the edge of that foam, 4 feet from the house, that slopes towards the lower part of the yard, away from the house, use some gravel drain tile (black pipe with holes and a cloth silt shield) in the bottom, then 2" crushed rock on top of that, that area is the edge of the driveway so the crushed rock will blend in, if it was yard then I would go to finer rock, maybe some land scaping fabric and top soil.

What could be used to cover the foam board, to make it look finished?

You can use pre-finished foam that has a stucco or pea gravel coating, or buy rubber stucco in a bucket and brush or trowel it on, that is what I did, two coats of thinly troweled on gray latex/sand stucco with fiber gilass tape on the seams.
You can also use aluminum flashing, steel flashing, fiber glass milk board like foundation wall covering or a nice brick or stone facing.

for my own house I ended up only insulating one and a half sides of it so I bought two six packs of beer to share with the three friends who showed up to help dig, it took about 4 hours to dig out, install drain tile, plastic that directs the water to the drain tile, 2" foam, more plastic and every seam was taped with vaper barrier tape on the plastic and this thick gooy rubber tape with aluminum foil backing on the foam and were the foam meats the house, it's a tape designed for going around sky lights to keep the weather tight.
All in all I think we put down around 6 sheets of foam, 200 feet of drain tile, back filled it and raked it all out at a nice slope, we have not had any more water leaks in the basement (used to have a few gallons leak in every time it rained) and the basement is warmer.

Thanks for the finish ideas. Not one did I have.

Beer. Yum!

Cheers
kevin