I agree with you totally, except a two story box is most efficient, instead of a one story sprawling ranch, or a house with all kinds of wall exposure. Half the slab cost too. I'm thinking we ought to start a thread titled "Energy Savings Ideas to Design into your Next Home". Would you contribute? I see adding an item a day. It could eventually turn into a sticky.
Have you see my thread "OMG, My attic hit 90 Degrees"? Right up your alley. Pic...

Steve

Here is a link that might be useful:

Likewise with a home with lots of south-facing glass - you can make the glass repel a lot of that solar energy, but a better design would shade those windows from the sun entirely, or would locate them on a less solar-intensive elevation. -- rltarch

Sorry, but you can't generalize like that. For example, passive solar homes depend on all or most of the windows being on the south side.

Passive solar homes are especially effective in the North, but they also work in the South where we are building. Sun through the south glass is free heat. Properly designed overhangs along with careful solar orientation control the summer heat gain. Done correctly, little to no sun strikes the south windows during the summer cooling season. Added thermal mass helps dampen the daily temperature swings year round.

West windows are much more of a problem, due to the low sun angle in the late afternoon and early evening, which is why our new home will only have two of them, both small. On the other hand, there will be 35 windows in the south wall, plus four glass doors.

Morning east sun...likewise. I built mine inside an oak mott, between the shade trees and the south facing porches, minimal direct sun exposure.

Can't have windows on the north side in the North. So I guess that leaves us with no windows at all?

Although you might want to limit the number and size of windows on the north side of your home, there is no reason to think that you can't have windows facing that way.

And, if you happen to have the best views to the north and you want more windows in that direction, there are options available that way as well.

In order to show how windows affect wall performance, and hopefully to start a discussion or two, I am dropping in a relatively simple comparison of window performance, using a 1000ft2 wall with 200ft2 of windows.

Simple because there are a number of factors that I haven't included such as a roof (which some people seem to consider an important part of any home), and I didn't take into account in any way direct solar gain which can be both a positive or a negative depending on climate and time of year.

I think that the numbers may even surprise some folks.

Total wall = 1000ft2
Windows = 200ft2
Wall window = 800ft2

Total wall insulation value (excluding windows) = R10 or U.1

Window option a = U.5
Window option b = U.3
Window option c = U.15

Wall = 800ft2 x U.1 = 80

Window a = 200ft2 x U.5 = 100
80 + 100 = 180/1000ft2 = U.18 or R 5.5

Window b = 200ft2 x U.3 = 60
80 + 60 = 140/1000ft2 = U.14 or R 7.14

Window c = 200ft2 x U.15 = 30
80 + 30 = 110/1000ft2 = U.11 or R 9.1

So in this scenario upgrading windows from U.5 (typical clear glass dual pane performance) to really good LowE triple panes at U.15 improves overall wall R-value performance by 65%.

Increasing total wall insulation value to R-20, again excluding windows, then

Wall = 800ft2 x U.05 = 40

Window a = 200ft2 x U.5 = 100
40 + 100 = 140/1000ft2 = U.14 or R 7.14

Window b = 200ft2 x U.3 = 60
40 + 60 = 100/1000ft2 = U.10 or R 10.0

Window c = 200ft2 x U.15 = 30
40 + 30 = 70/1000ft2 = U.07 or R 14.3

So per the formulas, doubling wall insulating value, and still using windows with U-value of .5, results in an overall wall R-value improvement from R 5.5 to R 7.14.

Interestingly, in this scenario, improving window performance from U.5 to U.3 (dual pane clear glass to dual pane LowE and argon) in the R10 wall results in the same improvement in overall wall R-value performance as does increasing wall insulation from R10 to R20 while using windows with a U.3 in both walls.

In the R10 wall, improving window performance from U.50 to U.15 resulted in an overall wall improvement of 65%.

In the R20 wall, the same window upgrade results in a 100% improvement in overall wall value performance.

Again doubling the wall insulation, this time up to R40, and yet again excluding windows, then

Wall = 800ft2 x U.025 = 20

Window a still = 200ft2 x U.5 = 100
20 + 100 = 120/1000ft2 = U.12 or R 8.33

Window b = 200ft2 x U.3 = 60
20 + 60 = 80/1000ft2 = U.08 or R 12.5

Window c = 200ft2 x U.15 = 30
20 + 30 = 50/1000ft2 = U.05 or R 20

So, improving 800ft2 of wall space from R10 to R40, and using windows with a U-value of .50 in both walls, results in an overall wall improvement from R5.5 to R8.33 or 51%.

And yet again (again), assuming my math is correct, in this scenario 800ft2 of wall with R10 insulation, but with 200ft2 of U.15 windows, actually has better overall wall R-value performance numbers than does a wall with R40 insulation and U.50 windows installed.

A bit long but hopefully food for thought...

Interesting. There are two issues that I've thought of.
1. The benefit to cost ratio diminishes as you improve efficiency.
2. Walls certainly contribute to the heat gain of a house, but it's nowhere close to what the roof/attic does.

"1. The benefit to cost ratio diminishes as you improve efficiency. "

I'm not sure that's a valid statement. I've seen many cases where upgrades have more than paid for themselves in direct, energy-consumption cost savings.

""1. The benefit to cost ratio diminishes as you improve efficiency. "

I'm not sure that's a valid statement. I've seen many cases where upgrades have more than paid for themselves in direct, energy-consumption cost savings."

It is valid.

The initial cost/benefit for efficiency is often large, and easily pays for itself over a reasonable lifetime for the improvement.

With the energy demand now reduced the cost/benefit becomes higher, it costs more or saves less.

My apologies; I misunderstood the statement.

Hey Oberon!! can you drop me an email??

what I would like to see is homes designed with the ductwork in the conditioned space, then duct leakage
would be to the interior of the house and not the exterior.
there are so many real world problems with duct leakage/return leakage and so many oversized units to make up for the leakage.
HO gets 5 tons on 2500 sq ft home..if house leakage
were reduced and duct and return leakage reduced to 5%
then unit is oversized...
one of the biggest misnomers is that a bigger unit is better. what really happens is that unit short cycles
costs more to use per month, doesn't run long enough to
remove humdidty..and because of all the stops and starts
has a shortened life.
high efficient hvac is only as good as the install.

in my latest training class they did a calculation that blew me away...
I've seen a lot of home with R-38 attic insulation, with attic staircase in the conditioned space.
so when uninsulated attic staircase is included with little to no R-value the overall attic insulation is reduced to R-25...now throw a bunch of IC rated recessed cans (not air tight ICAT) one equals one sq ft of uninsulated attic..what do you have now???
insulation that can't perform because of air movement through the insulation..

efficiency always costs more upfront, but it is the length of time it takes to pay back that cost that makes one option preferable to another.

green is 80% energy efficiency and 20% everything else
(joe lstriburek of buildingscience.com)

I would like to see an energy efficiency forum here.

"what I would like to see is homes designed with the duct work in the conditioned space, then duct leakage
would be to the interior of the house and not the exterior." -- energy_rater_la

That is what we are doing. Our GC is having the trusses built with a notch for the supply duct. The notch will be drywalled and sealed on the top and sides. The attic insulation will be above the notch, all of which will bring the duct effectively into the conditioned space.

While there will be drywall below the duct too, the registers won't be tightly sealed from the duct cavity, so any duct leakage will be forced down into the room, instead of up into the attic.

BTW, our attic stairs will be in the unconditioned garage.

I have trusses between the first and second floor, with space enough for the flex duct to travel through an opening.

Yeah, you really need to do some research on passive solar.

This site has some brief info on windows.

WAY over generalized! We built our house facing due South. The south facing wall is ALL glass, two stories tall. There's no reflective treatment on the glass, that would defeat the purpose. There is only one tiny window on the west wall. We have NO A/C and none is needed, this house stays very cool in the summer. And in the WINTER! Unless there is heavy cloud-cover, it requires NO heating whatsoever. None. Even with snow on the ground and below freezing temperatures, if it was a sunny day, we have to open the windows at night, otherwise it could go over 80 degrees. Nice and toasty. Don't over-generalize. It's all in the design.

Proper design is very important when building a home to take advantage of solar.

It is probably more common for folks to use too much south facing glass in a solar design than too little, it is quite possible that given the right set of circumstances overheating a home in winter can be more of an issue than overheating it in summer.

Although some folks believe that clear glass is the best choice to take advantage of passive solar heat gain, in reality, LowE coatings don't necessarily defeat the purpose of passive solar gain.

Using the correct LowE coating will actually enhance solar heat gain by keeping the solar-gained heat in the home when the sun isn't shining on the glass.

Y'all might be interested in this house being built by a group of univ. students in Lafayette, LA (go Ragin' Cajuns! :-) ). In the fall of this year, they will travel to Washington D.C. to compete in the US Dept of Energy Solar Decathalon competition. It is intended to be totally self-sufficient.

I have no specific interest in this project, except that I'm a Univ. La.-Lafayette alumni and I hope they win :-)

energy rater la, you may already have been aware of his project, but if not, hope you get to check it out for yourself.

There is a fairly new product out by Dow called SIS. (Structual insulated sheathing)It is an external sheath panel with either 1/2 or 1" styrofoam and house wrap all in one panel.It acts as a structial panel and the 1" foam gives an R value of 5.5. The edges of the panel get taped like house wrap. Combine this with 2x6 construction with R19 fibreglas and the walls become R24.5. The foam on the outside takes care of the thermal bridging through the studs for a truer R value. If one glues the panel( as well as screwing)it helps seal the air flow through the walls.

Everything I ever read says going beyond R13 in walls isn't cost effective.