I want to hear some thoughts on the matter.   This is for an ICF house.   What are the implications insulation wise (heat/cold loss) if one used 3'x3' windows compared to 4'x4' windows?    I'm talking about the Pella type of windows with two panes and air or something in between.  Energy star and energy efficient and all.    Would it make a big difference?   Slight difference?   No difference?   I'm thinking why make the walls using ICF's then have bigger windows where the heat/cold gets in/out?

I'm thinking why make the walls using ICF's then have bigger windows where the heat/cold gets in/out?

Because people like to look out the windows. There is also an architectural element of attractiveness about the windows. If neither of those things matter, then it is only a matter of building code.......

Windows themselves do not have a high R-value, but as stated they are architectural components of the house.

Your heat loss at a window is going to happen, I can't run the numbers but the heat loss cost from a 3x3 to a 4x4 I am sure is minimal.

The biggest factors of windows are the window seal themselves around the glass and if the window is an operating one, the seal when closed, the second factor is the installation, how well was it done and was it sealed properly.

Chris is spot on regarding the importance of the installation.

That said, given the same window characteristics, u-value etc. there is about 75% more heat loss in a 4x4 than a 3x3. That's quite a bit of difference. Particularly if you have a bunch of them. I would still put in the windows you "want" while keeping in mind that they are the weakest link. Regards.

Posted By jacktca on 19 Jan 2012 02:45 PM
   I'm thinking why make the walls using ICF's then have bigger windows where the heat/cold gets in/out?

99% of people do NOT want to live in a box with no windows. While having a home with no windows would result in the strongest & most energy efficient design but who would want to live in such a place? A vampire?

People like being able to see the sunlight and outdoors from the inside of their homes. Some people have great views and wish to see them while inside. Not everything is always about efficiency. Architectural elements & aesthetics are important to people also.

I prefer to lose some energy out my window but be able to see a great view like this:

how much view do you need while you are asleep and have your eyes closed--unless you have a wife like my now EX wife
Invest in good windows and good, insulated drapes or shutters.
There are nano coatings that will block or retain heat up to about 10%

I may have missed part of the question above. Why bother with ICFs if you want lots of windows? Think of your house as a boat with a number of small (thermal) leaks. A window might constitute one leak and a large window might constitute two. Since ICF generally outperforms conventional you will still have a better performing house with ICF. Your performance will go down with many large windows and will just go down further with conventional.

Additionally, as many of you know thermal mass effects are clear and obvious in just about any ICF structure long before it has windows or doors installed. If you don't believe this I can say with certainty that you really haven't been around ICF under construction. You don't have to go more than a few feet into a cave to experience the mass effect and most caves don't have doors. Regards.

Go to Builditsolar they have a very good insulation calculator that lets you plug in different insulation values and you can get a cost idea for each change. I've used it for windows before

Once you start tinkering with certain window calculators, you will find that windows are also a source of heat (insolation) and not just heat sinks.

Posted By ICFHybrid on 20 Jan 2012 10:17 AM
Once you start tinkering with certain window calculators, you will find that windows are also a source of heat (insolation) and not just heat sinks.

Very true. In the winter you will love the fact that you have windows, especially those that are south facing. In the summer, if you position the home correctly and incorporate shades, the heat gain will be minimal.

Wow this is turning out to be a controversial issue, and it shouldn't be.   What happened is the architect planned on using Reward blocks.  They are 16" high.  So 3x3 windows would not fit well but 4x4 windows would fit perfectly (3x16=48).  I ended up buying what is left of a warehouse full of Integraspec blocks.   They are 12" high.   So 3x3 windows fit just as well as 4x4 fit without having to cut blocks up to make them fit (3x12=36).   That said, I have lots and lots of windows in the plan.   They don't all have to be 4x4.   I can make some of them smaller, say 3x3, especially on the side of the house where the view is not so breathtaking.    The bedroom window doesn't need to be 4x4.   It's not a case of windows vs no windows.   It's a case of I have lots of windows in the plan do they all have to be so big?   

Posted By jacktca on 20 Jan 2012 02:55 PM
The bedroom window doesn't need to be 4x4.

No, but it's got to be close. Bedroom windows must meet the requirements for emergency egress which in the 2006 IRC is 24" high by 20" wide clear opening and no more than 44" above the floor. A 3' x 3' window won't meet that.

This requirement applies to all sleeping rooms and basements.

Forget about fitting the block size. It's easy to cut the hole in the block wall to fit the window. And, just because a window is 3' x 3', or 4' x 4', doesn't mean the rough opening is that size. Plus you've got to figure in the window buck inner and outer dimensions. And window rough opening dimensions are not standardized. Make sure you decide what windows you are going to use BEFORE you start building the walls. Andersen sizes ain't the same as Pella ain't the same as Peachtree ain't the same as Martin ain't the same as... You get the picture.

This the report upon which Nudura bases its insulation claims, Nudura being the brand that TexasICF sells.

http://www.nudura.com/Libraries/Tech_Centre/NUDURA_WHOLE_WALL_THERMAL_RESISTANCE.sflb.ashx

You will find nothing about thermal mass, caves or thermal-mass-adjusted equivalent R value, as the Federal Trade Commission wants to see it, along with legitimate research. You won't find it because ICF's thermal mass effect is not cave-like but rather groundhog burrowish. So TexasICF offers up what "many people know" instead.

If I am misstating the facts, Texas, please post a link that does substantiate Nudura's thermal mass effect.

Emergency egress???   Wow, I didn't think of that.   So I can make the windows 24"x48" but not 36"x36" because the egress on that would be 18"x36".   Good to know this. 

A 36x36 operable casement window would work. We're using one 35x47 casement in each of our bedrooms/office/den rooms; the remainder of the windows are fixed. Additionally, they leak less than double hung or sliders. Dave

Posted By toddm on 21 Jan 2012 04:41 PM
This the report upon which Nudura bases its insulation claims, Nudura being the brand that TexasICF sells.

http://www.nudura.com/Libraries/Tech_Centre/NUDURA_WHOLE_WALL_THERMAL_RESISTANCE.sflb.ashx

You will find nothing about thermal mass, caves or thermal-mass-adjusted equivalent R value, as the Federal Trade Commission wants to see it, along with legitimate research. You won't find it because ICF's thermal mass effect is not cave-like but rather groundhog burrowish. So TexasICF offers up what "many people know" instead.

If I am misstating the facts, Texas, please post a link that does substantiate Nudura's thermal mass effect.

Hello Todd.   Please allow me to attempt to clarify.   You've linked to Nudura's laboratory R-value report.   R-value, which we have discussed in the past only deals with conduction and conduction only.   It does not include convection or radiation nor does it include thermal mass in any way shape or form --- not sorta, kinda or even a little.

No one should expect to find references to the other two modes of heat transfer or to thermal mass in Nuduras document about conduction (R-value).   I will repeat what I said earlier -- anyone that denies the thermal mass effect of ICF just hasn't been around it directly.

It's not that your misstating facts exactly it's just that some of this conversation is going to require a little more research on your part.   I would like to suggest you check out google: "ASHRAE K12 50% Solution" or check out the greenbuildingtalk thread.    Download the document and read it.   The top performing schools in the United States are predominately mass schools and Nudura currently holds the number one spot as the top performing school.  This document is not "about" Nudura but it does elevate the importance of ICF and mass walls in general to another level.  

If you want to report me to the Federal Trade Commission, go ahead -- but you might want to include the authors of the above document that recommend ICF as a mass wall solution.  For example:   ASHRAE,  The American Institute of Architects, The U.S. Green Building Council and the U.S. Department of Energy.   Perhaps the Federal Trade Commission will argue with the U.S. Department of Energy.    Regards.

Posted By jacktca on 21 Jan 2012 04:44 PM
Emergency egress???   Wow, I didn't think of that.   So I can make the windows 24"x48" but not 36"x36" because the egress on that would be 18"x36".   Good to know this. 

Don't count on it. Depends entirely what the actual 24" dimension is. Keep in mind by the time you figure in the frame and sash and how the window opens, the 20" requirement could end up close to 28". For example, the Andersen 400 casement CX14 with split arm hinge requires a rough opening of 32" but has a clear opening width of only 21.8". The optional straight arm hinge will increase that to 25.69".

Welcome to wonderful world of window haze. You're in for some real learnin' my man! It's a world where 2.5 + 3.8 = 6.1, or is it 6.5, and on rare occasion it might even = 6.3!

Pella Designer Series, metal clad wood frame casement, smallest sizes to meet egress rqmts is 29"W x 35"H and 25"W x 41"H with optional side mount opener.

http://www.pellaadm.com/userdocs/do...SSZTAB.pdf

TexasICF, one should expect to find references to thermal mass effect and corresponding research in Nudura's literature if the company includes mass in its thermal performance claims. Otherwise, as you suggest, the FTC would come calling. Just to be helpful, it would look something like this: http://www.logbuilding.org/EnergyPerformanceLogHomes.pdf

Please post a link.