We insulated on the outside of our foundation when replacing the weeping tile. we used sprayfoam, initially envirofoam and later used walltite upstairs and part of downstairs. it cost roughly $3 a sq ft for 2 inches, the amount the recommend to be a vapour barrier; they claim r7 and inch but it might settle closer to r6 an inch.

you could feel that the uninsulated furnace room was warmer on the part insulated the day before and cooler on the part done after that. a national research canada study suggested similar spray insulation was effective insulation and could last some years. it is water resistant or better. it should seal the small cracks in the foundation (unless the foundation movest too much). In winter the basement needs much less heat than upstairs, in part due to the insulation and in part due to larger windows upstairs and more exposure to cold winds. the same spray insulation covered the joist ends on the outside but then has to be covered with stucco or something else.
good luck with your insulating.

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I am also in the process of building. I have some building experience and will also be insulating and finishing my basement. I have projected costs for finishing the basement myself and you definitely save thousands not only from the labor side but also from energy costs projected over the life of the house. If at all possible one should always consider insulating under the slab of your house. One of the biggest mistakes people make is to not spend the $700 on insulation to insulate under the slab. Most people insulate on top there by losing thermal mass which acts as an effective temperature moderator for basements. With the slab insulated underneath one can overpour self leveler and place radiant heating cables for really cost effective heating.

In regards to the extruded polystyrene…make sure you weigh the cost and benefit of this system. Extruded foam often looses R-value over time unlike the expanded stuff. The expanded stuff can also be used just erect a vapor barrier over the foam before the stud wall. make sure not to put another vapor barrier over the batt insulation as you will create a bubble between the studs where water vapor will sit and cause mold to grow on wood studs.

One other thing to consider is when to insulate. Depending on the initial water content of the concrete it could take over a year for the concrete to expel excess moisture not expended during cement hydration! In other words, wait a while, put a dehumidifier in the basement, keep it going around 50% Humidity. Even when it looks dry it probably isn’t. Tape a piece of plastic to the floor leave it there for a day or so then check it for trapped moisture

Anyway, I am no expert on building but I am a physicist and I have studied thermodynamics and fluid mechanics. Air infiltration and vapor control are all complex physical processes. The dynamics of moisture infiltration in basements is quite complicated and controlling it is an uphill battle. here’s an artile you may find useful.

http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf

Djg

I am going through the exact same process right now. We still have half of our basement undeveloped. We received a bunch of quotes on the materials. Kents came in the lowest for the studs – $2.69 per.

Another thing you might want to consider doing is putting in a sub floor.

Good luck!

Chris

Tom, interesting point about the blown in insulation and condensation. How did you fix it? And yes, I will be using gyproc to finish in the future, the wood listed above is for the framing.

Thanks for the heads up Ken!

We had the blown foam insulation sprayed in our house – it comes in two separate canisters and forms as the two liquids combine. The cost is pretty high – just for the rim joists it came to $14 per linear foot. But it’s about the best insulation you can buy, and it seals great. The problem we had was that in the summer hot humid air would get in via the rim joists, condense against the top plate bolts (the bolts that hold that strip of lumber to the top of your foundation), and then the condensation would collect and drip down the wall into the insulation. Not nice. But the fix worked great – this summer, not a hint of condensation, so we can now feel comfortable finishing the basement. Our ‘interesting’ neighbours all have the same problem – one of them had all his exterior windows re-caulked thinking that was the problem – the only thing was – the moisture was along the entire wall – not just under the windows!

One question – you said you were finishing the walls with plywood? Can I ask why not drywall? That gives you a nice finished wall surface..

Tom

Just my $.02

DAvid

My basement is now insulated with R24 with 7 inch of fibreglass Instead of polystyrene panels.

The wall is framed with a 3 1/2 space between the wall and the studs. One layer (R12) of fiberglass between the outside wall an the studs and another (R12) between each stud. In addition a vapour barrier is hung on the outside wall (starting 4 inches above grade) and another a standard vapour barrier on the surface of the wall.

Not sure what your total R value will be but doing it will cost a few hundred less and give you R24.

It can get pretty cold here in Manitoba and I have been very happy with the results.

I had my builder do my basement and he used the polystyrene foam (pink stuff) cut to fit the rim joists and then caulked.

On your plan – it seems like overkill to glue sheets and then use batting over top – batting itself should provide ample insulation and can be placed directly against your concrete wall. You can use cheap and effective clear plastic vapour barrier and you should be all set.

Ontario is fun because unlike out east, we have 2 different problems: keeping hot outside moisture away from your cool dry indoors in the summer, and then keeping the cold dry outdoor air away from the moister, warmer indoor air in the winter. Makes placement of the vapour barrier a challenge, and often homeowners end up with condensation in their insulation. Best way around it is to blow poly foam into the rim joists. but you shouldn’t have trouble with that, since the air is less humid in your area. It’s that humidity that kills us!

Telly, the issue with insulating the basement ceiling is that if the basement is unheated, it will actually make the basement colder (it will insulate the cold).