Here are his words: I actually think icf is too good at insulating! Here are mine: A tighter seal just means you have more control. It's only bad if you use it unwisely What do you think? We live in northern va and have adjacent unimproved properties ready to build. (His preferred method is to use double 2 x 8 instead of 2 x 6 and stuff it with more insulation

Too well insulated means no heat or cooling needed. I haven't run into one of those in 40 plus years in the business.

Too well insulated means no heat or cooling needed. I haven't run into one of those in 40 plus years in the business.

I look at "too well insulated" as meaning the following:

The energy cost savings you will realize during the ownership of the home will not equal or exceed the price differential between the PREFERRED insulation method and rating, and the code-minimum or a more reasonable high-insulation plan.




This is usually because the person isn't also looking at soft factors like air sealing, comfort levels, thermal breaking, noise reduction, etc.

Yes, ICF generally results in a VERY tight home envelope.
To the point where mechanical ventilation and the planning for it is mandatory.

This is a Good Thing.
When it comes to your home's interior environment, you do NOT want to be "balancing" against exterior environmental factors over which you have no control.
You want CONTROL over the interior environment.  PERIOD.  With the exterior environment introducing, IDEALLY, NOTHING AT ALL to the mix.  Realistically, you want it introducing as little as is feasible.

Then all you have to do is get it to your ideal conditions and spend as little time and energy as possible on maintaining that, while exhausting stale, "polluted" air and bringing in "fresh" air.  Again, in a manner and rate YOU control.


Also, simply because an insulation plan IS "overkill" does NOT mean you should NEVER go with it.
You could have very specific, very tight energy goals you're trying to achieve (such as Passive House/Passivehaus).  And what you're going overboard in insulation on, you may realize some savings by getting away with through right-sizing of your HVAC systems.

You may also realize cost savings in construction through redundancies.
Say you're going ICF from slab to roof.
While you COULD spec different levels of insulation value for sub-grade and above-grade walls.  But, when buying in bulk, the cost differential is negligible, and it becomes easier (labor saving) when you're dealing with components that are all the same size.

As for double 2x8 vs ICF.

How crazy were you looking to get with ICF?

Depending on what insulation he blows into a double 2x8 setup, you're looking at R60+ And a wall structure that's going to be 18+ inches thick.
And, unless he's putting exterior insulation on, he's going to wind up with mold, mildew and rot in his wall structure due to the dew point in a cold climate occurring WITHIN the wall structure.
He's be better off putting 3-ish inches of rigid foam outboard of the stud bay/sheathing and going single 2x8. With blown-in fill like fiberglass, cellulose, etc, you're talking R15 (exterior) plus about R28 in the wall cavity. And leaving you with a wall system that's been fully thermally broken.

ICF might be more expensive if you're looking for an identical level of insulation value.
But you'll realize massive labor savings as you wind up with a fully insulated & air-sealed wall system once the concrete cures.
All you'll want to do is look into water/vapor sealing the wall. Likely in some form of peel & stick or fluid-applied product.