Thoughts on building a house with ICF's.

[Bryan Berguson]

We've found ourselves needing to move so we need to build a new house. I've said for a long time, "If I ever build another house, I'll build to the roof with ICF's". This would be basement and first floor. We live in the Northeast so insulation is a major consideration. Anyone have thoughts, good or bad, on building with ICF's?

The other unique feature I'm considering is putting my woodshop under the garage. Right now the woodshop is in our basement which I said I'd never do again. However, I need to consider cost(s). Any thoughts on this? Garage will be 26X30, which would be a little bit smaller shop than I have now but just a little and no support posts so I won't be sacrificing much.

Thanks

Bryan

[Ted Calver]

ICF's ???? Plus additional question marks to meet minimum length reqts.

[Brian Libby]

@ Ted ICF's are insulated concrete forms

@ Bryan : I have a friend who thinks ICF's are great - He built his house with them 3years ago. A shop under the garage sounds like a great idea !

[Mark Bolton]

Not that it means anything but been in the building trade through much of my teens and adult life. Personally I wouldnt go with them on the first floor simply because you will have the added cost of the ICF's coupled with a lot more costly details associated with every other aspect of the project, deck framing, wiring, plumbing, window and door fenestrations. Unless you find a contractor who is specifically specializing in complete ICF envelope construction I would wager it will be a challenge, and very costly.

Being from the North East (MA originally) I completely understand where you're coming from. My advice would be 100% for the ICF foundation and then look into super insulated framing techniques for the structure above. You can really do a lot with a building envelope 2x6, stack framed, 24" o/c, header hangers, and even an exterior wrap of 1" ISO. You can easily get close to an R25 envelope. If you can do everything possible reduce the wood in the wall and trade it for insulation you can really make great gains. You will be confronted by a lot of "I would never not go 16" o/c" but its whooey. Do your homework and you will find you do a lot with a conventional frame. Its the habbits of the US builder that keep our envelopes so inefficient.

Just my .02

Mark

[Brian Libby]

Re-read your thread- I agree on only doing the basement - that is what my friend did.

[Bryan Berguson]

Not that it means anything but been in the building trade through much of my teens and adult life. Personally I wouldnt go with them on the first floor simply because you will have the added cost of the ICF's coupled with a lot more costly details associated with every other aspect of the project, deck framing, wiring, plumbing, window and door fenestrations. Unless you find a contractor who is specifically specializing in complete ICF envelope construction I would wager it will be a challenge, and very costly.

Being from the North East (MA originally) I completely understand where you're coming from. My advice would be 100% for the ICF foundation and then look into super insulated framing techniques for the structure above. You can really do a lot with a building envelope 2x6, stack framed, 24" o/c, header hangers, and even an exterior wrap of 1" ISO. You can easily get close to an R25 envelope. If you can do everything possible reduce the wood in the wall and trade it for insulation you can really make great gains. You will be confronted by a lot of "I would never not go 16" o/c" but its whooey. Do your homework and you will find you do a lot with a conventional frame. Its the habbits of the US builder that keep our envelopes so inefficient.

Just my .02

Mark

If I go with conventional framing (which I'm leaning towards), I was planning on dense pack cellulose. If I have sheet insulation on the outside, does it go under or over the OSB? I'm thinking over and then just use longer nails for the siding? I've done it on the inside of the stucture with drywall over it but it's difficult to say the least.

24" oc 2x6's would be equal in strength to 16" oc 2x6's wouldn't it? But, if wrapped with 1" of insulation, does 24 oc vs 16 oc really make much of a difference? Insulation wise.

thanks

[Matt Meiser]

Are you sure you don't me SIPs?

SIP = Structural Insulated Panel (2 sheets of OSB with foam between)
ICF = Insulated Concrete Form (2 sheets of foam with plastic ties between to be used for concrete forms, then left in place)

Both look really interesting if one is building but I'm not sure ICFs would make for a good roof

[Bryan Berguson]

Re-read your thread- I agree on only doing the basement - that is what my friend did.

Thanks Brian. That's why I'm asking here... lot's of experience and common sense! Did he put radiant heat in his floor and if he did, what kind of insulation did he use?

[Mark Bolton]

If I go with conventional framing (which I'm leaning towards), I was planning on dense pack cellulose. If I have sheet insulation on the outside, does it go under or over the OSB? I'm thinking over and then just use longer nails for the siding? I've done it on the inside of the stucture with drywall over it but it's difficult to say the least.

24" oc 2x6's would be equal in strength to 16" oc 2x6's wouldn't it? But, if wrapped with 1" of insulation, does 24 oc vs 16 oc really make much of a difference? Insulation wise.

thanks

Whatever insulation you choose is fine, spray foam would of course likely be the highest R value but its whatever the best you have available (and in budget). You can install the ISO directly on the studs and omit the OSB all together though you have some issues to contend with. Many super insulated shell's opt for OSB on the corners only for stability with 1/2" ISO everywhere else then another complete wrap with 1/2" ISO to get you to the 1" (except on the corners where you will have 1/2" OSB/1/2" ISO). Others omit the OSB altogether going for Z strips on the diagonals at the corners, let-in to the studs. This allows you to go with a 100% ISO exterior. Super tight. If you think of 1" of ISO at an R8 plus your interior walls at their lowest being an R19 fiberglass) you are already at an R27. If you pop your cavity insulation you can break R30 in a 6 1/2" thick envelope easily.

Omitting the OSB, in my opinion speaks more to what your exterior siding will be more than anything else (fastener spacing)

Have you looked at buildingscience.com ? You will have to look into many issues such as vapordrive, fresh air exchange, and so on.

Mark

[Jerry Bruette]

Bryan

Pick up the January edition of Fine Homebuilding. they have three articles you'd be interested in, Energy smart foundations, Attic insulation fiberglass vs cellulose and The American House: Where did we go wrong. All three articles talk about insulation and maybe more importantly infiltration, stopping air from entering and moving around in your house.

My house is over 20 yrs. old and I have conventional framed 2x4 walls with 1 inch of foil faced ISO on the outside and dense pack cellulose. I think wrapping with the inch of ISO is better than 2x6 framing because the ISO gives you a thermal break which you don't have with the 2x6 frame. You may have a higher R value with the 2x6 frame but you won't have the thermal break at each stud without the ISO wrap.

I would also consider trusses that hae the extra height where they meet the wall for insulation, around here they call them energy trusses. Might go by another name where you live.

If you can't find the Jan. issue of Fine Homebuilding I'd be happy to send the copy I have I'm done with it.

Jerry

[Mark Bolton]

the ISO gives you a thermal break which you don't have with the 2x6 frame. You may have a higher R value with the 2x6 frame but you won't have the thermal break at each stud without the ISO wrap.Jerry

Why dont you have the ISO break? You can still frame 2x6 with no exterior sheathing and just ISO on the exterior. I am not sure I follow you here? A thicker was is just that, a thicker wall. Provided you fill it with insulation (and can afford to), its always going to be better. Super insulated walls of old were 10" thick with fiberglass.


Mark

[Bryan Berguson]

I'll look for that issue Jerry. Thank you - if I can't find it, I'll take you up on that offer.

Bryan

[Jerry Bruette]

Mark

Many of the contractors in my area convince home buyers that a 2x6 wall has a higher R value, which it does. But that's only half of the story. Without a thermal break on the inside or outside of your studs they will be a cold spot (or hot) in yor wall.

I suppose a 2x6 frame with a sealcoat of foam sprayed inside the stud cavity, finished with cellulose, and wrapped with one inch of ISO onthe outside would give you the ultimate in tightness and insulation value if you can afford to do it.

Jerry

[Chris Damm]

You say you want to put your shop under the garage with no support posts. This would require prestressed concrete planks or a lot of very big steel beams. That would be very expensive and require expensive equipment to place them.

[Brian Libby]

@ Bryan- I think my friend used radiant heat
I know of at least two neighbors that have used the prestressed concrete for garage floor. - added cost IMHO is worth it.
In the same foot print you get all that added clear span space