ICF's tend to have nailing tabs for dry wall and siding and if you are going to add insulation you should add it to the outside that way the mass of the concrete is better insulated.
If you want to know how bad the electric heat is then get a copy of the utility bill, if the house is old enough to have a history that is, you said it was new... is it brand new or just new to you?
ICF's vary in insulation value, some are better then others, their advantage is that they are monolithic so you have no drafts in your walls, other then around doors and windows.
Even if it's a brand new house, having an energy audit done is a good idea, builders take short cuts whenever possible but problems will not show up right away because not enough time has passed.
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