We're building with ICF's to the roof line in northern  NY.  We're getting our windows through InLine out of Toronto.....fiberglass casements and several sliding doors.  Their recommendation is to locate the windows several inches back from the outside face of the ICF wall.  It is possible to flush mount their windows but you pay an upcharge for the "brick mold" and the nailing fin (which is PVC).   InLine also has (for a fee) external aluminum extensions to accommodate setting the windows back into the opening.  Those aluminum extensions come in 1 5/8 inch and 3 1/4 inch.  The rationale for setting the windows back in the opening is for protection from the weather (wind and driving rain) and for increased energy efficiency.  The argument is that from the inside of the house to the outside there is a temperature gradient through that window opening.  Locating the windows back within the 12 inch deep opening reduces the gradient so reduces the likelihood of condensation.

My husband is concerned about mounting the windows back within the opening because he feels he won't get as good a weather seal as flush mounting them. 

The window bucks will be made from....oh drat, can't remember....not PT wood, I think it's engineered and is environmentally greener.

I have read Manfred's comments about pulling out the bucks and mounting directly to the concrete. 

Any thorough explanation about this process, and opinions about the location of the windows within the openings and the need for exterior extensions, would be very helpful.  I'll pass them along to my husband.

Thanks in advance!  Cathy

We have always installed windows flush the the exterior of ICFs. I think that I get a better seal on the window opening by using the nailing fins and perimeter foaming for sealing. The statement about reducing the likelihood of condensation by recessing the windows does not ring true to me.

I second Wes. And the extension jam is better on the inside, for a seat or set stuff, than on the outside where you have to get water and snow to not stay there.

The external jams are tapered.  I guess snow could be an issue but rain would run out.  Cathy

Cathy,

I second the comments...every ICF project I have seen the windows are mounted flush with the outside of the structure using the nailing fins. This allows a more traditional approach with the finishing of the exterior veneer or siding.

I am also doing some building- from footer to roof with ICF. I am curious which brand of block you will be using.  The choices seem to be too few and far between, at least up here in Timbucktou.  BTW 14 minutes from the Bridge to Canada. 

As to the topic, Aluminum has little R value and I had always understood it became a 'wick' to radiate heat from the house.

Where are you?  Which bridge?  Timbuktou sounds like around here.  We're about 1 1/2 hours south of the border in Trout River or Massena.

Our house is part of a NYSERDA research project.  We're using Logix blocks but the foam is a new foam that BASF is bringing into North America from Europe, called Neopor.  It has graphite imbedded in it and has a higher R value than the traditional foam.  It's a silvery grey, as opposed to white.   In any event, our house will have thermal couples throughout to monitor energy consumption for a year after we move in.  It's been an interesting project.

The aluminum wouldn't act as a heat wick because it dead ends into the outside of the fiberglass frame.  No conduction.  It would act as a wick if it were connected to something conductive or if it went all the way through to the inside.

Cathy

The window manufacturer is correct. Setting the windows back from the face does increase the efficiency of the window. If you install your windows with the nailing flange, the top sash on a double hung window is projecting beyond the face of the building and subject to direct force of the wind. Recessing the window means the wind has to work harder to place positive pressure against the window. I am building an Icf houuse in the near future and recessing the windows and doors is my method. You can seal your windows by back-caulking your stop material when you install your exterior stops. Use a fifty year caulk and place it where the sun can't hit it and it will last a long , long time.

Sorry smatwall,
I'm with the others on this one I believe it's more important to set the windows on the outside for better sealing since most water intrusion problems occur in the windows area.
Second I like the fact you can sit a plant or whatever on the inside. Most windows are built to sustain high winds and wind. mechanisms are more than often warrantied by the manuf.
so I don't think durability is an issue here .I'm also building my own in the spring .
Cheers1

Is there any reason you can't put a doubule buck? A 2x12 buck with a 2x6 buck built inside of it. Then you can still install windows with the nailing flange.You would have to be sure to flash it so water couldn't get in but it should work and give you what you are looking for.

Greg

Makes for more cost but can be done I'm sure.
Why not get a vinyl/fiber factory jam for the necessary width and be done w/it for at least 25 years .No more swelling mdf , bubling/pealing paint etc. Do it once do it wright!!
Cheers!

If you use a 2x12 across the wall it will introduce something called "Thermal Bridging" whereby cold can be transferred across the wood buck into your house.  While it may be unnoticeable, it can happen.

 I know that Nudura has a plastic "easy" buck system that uses a 2x6 inside the form eliminating this.

 But as most have stated, I don't think setting the window back inside the  wall is a great idea, as it would increase the chances of leaking.

I would stick to tried and true method of installing the windows on the external face of the wall.

Canton area, I also am using  Logix, I had just inquired from our local distributor yesterday about the new blocks.  They don't seem enthusiastic about something they don't stock.  I have tried to reach out to other block companies but, I need to find a distributor that has the bracing also. : ( 

 

I have solar and wind as part of my restoration project of a 160 year old farm house.  The addition is for the Mom in Law.

I am looking into the alternative windows choices,  I am finding the information and opinions very interesting.  Thank you all.

I'm not sure how far along BASF is with introducing the Neopor into the Logix blocks. They had to do a special manufacturing session (for lack of a better word) to get us our blocks. We are too wooded for solar and wind but are putting in lots of glass for passive solar in the winter. We looked into the solar hot water system from Viessman because we are going to use their boiler. It was going to cost us around $14K for just the solar tubes and the heat exchanger so we are not going that route. The house will be so tight we shouldn't need to burn a lot of propane anyway. As for windows, it's been an education. If you want to contact InLine Fiberglass in Toronto, ask for Mark. He's young but very thorough and he actually started his tenure with the company working on the factory floor assembling windows. Because of our house being a research project, I've asked Mark for a lot of data for the researchers to crunch and he's done so with grace and no complaints. Be aware that the higher end windows such as InLine are ordered "ala carte"....the base price is for a simple frame with the glass. If you want brick mold, nail fins, wood interior, exterior jam extensions, etc it all costs more. InLine has around 5 basic colors but they have an infinite number of custom colors (for a fee) and can even color the outside one color and the inside another (split colors...for a fee). They also custom size all of their windows so you can order exactly the size you want. We're getting a 16 foot sliding glass door for our living room. Cathy

In my case, with Andersen 400 windows, that wasn't an option, or at least not a reasonably priced option. All their catalog extension jambs are too short for an 11" block wall. I didn't inquire about cost for custom made jambs. Don't know what other mfrs offer.

I would focus on the word "unnoticeable". With an R value of about 1 per inch a 2 x 12 buck would have an R value about 11. When you compare that to the total wall area the fact it's R11 vs about R20 for the rest of the wall would degrade the total wall R value very little. The windows themselves are worthy of much more attention than the bucks. Typically each square foot of window has roughly the same heat transfer capacity as four square feet of ICF wall.

And you're kicking around the advantage of flush vs. recessed windows? Maybe I'm naive, but I can't help but think you're buying yourself a huge potential for air infiltration with that large a sliding door. Enough to maybe wipe out all your window gains. Have you looked at the fenestration data for the door? Sliding anything can't be as tight, I don't think, as a swinging closure. That's why casement windows are more air tight than single or double hung, or sliders. I put casement windows and french door for the patio because of that even though I would have preferred double hung windows and sliding door.