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Insulation Overkill?

mitcholmes's picture

As I start the beginnings of building my own home, I have tossed ideas back and forth in my own mind, so i figure I would also turn here to get some more respected advice.

On my mind right now is framing/insulation/sheathing for the home i want to build.  My questions are in regard to how much is 'too much' insulation or is that even possible / worth the extra cost.  I live in Fort Collins, CO which is climate zone 5.  I am going to be building a relatively smaller 2 story home, probably around 1,000 sq. ft. and I like the idea of 2x6 framing 24" OC, with advanced framing techniques to get the most out of my insulation.  BUT i also like the idea of using rigid foam sheets on top of the sheathing to reduce thermal bridging through the studs.  I'm not talking about just rigid foam for sheathing, because I know that creates headaches structurally, so I'm talking about 1-2" of rigid foam on top of OSB, sheathing the 2x6 walls.  

I assume 2x6 24"OC framing insulated properly would definitely do the job, but i'm just not sure if the 1-2" of rigid foam would be worth the extra hassle and money.  Is there a point in insulating a new home where it just gets ridiculous and the costs start outweighing the savings?  I want to do my first home build right, so in my mind overkill with insulation and sealing everything up sounds like a nice cozy home to me!  I don't know how much of a concern this would be, but doing the above would also create walls that are about 9" thick all said and done, which creates more custom work on the windows.... 

Thanks in advance for any input and advice.  If you think 2x6 walls with batt insulation and regular sheathing will keep me happy and cozy, let me know.

to save you the time and (post #207074, reply #1 of 25)

to save you the time and money of the exterior rigid foam board insulation and batt in the stud bays, i would opt for "open cell spray foam insualtion" in the stud bays.  it costs more for the spray foam insulation but it insulates much better than the batt insulation.  by not doing the exterior of the sheathing you shold offset the cost and have a nicely insulated and air tight house.

 

google (post #207074, reply #2 of 25)

Mooney wall

2x6 framing sucks for insulation values

and exterior foam needs lot's of tricks to avoid catastrophy

 

Mike Smith Rhode Island : Design / Build / Repair / Restore

              www.mfsmithbuilder.com

Mike (post #207074, reply #3 of 25)

Had an energy audit done here recently-

Looked through/at the heat sensing camera and was surprised to not see the stud locations in our walls.  The 1" dow bluebd we put on the exterior seems to have worked divorcing the studs from the exterior cold transfer.  Rain screen (vertical furring) over that, felt paper then siding.

Had I known about Mooney at the time, I'd have surely done that too.

Lower level, stepped block walls w/2" rigid fibreglass panels over the block-2x10 studs to make up the thickness so no ledge in/out.  2x6 -24"oc upper level.

No catrastrophy as of yet.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


A super insulated house in (post #207074, reply #4 of 25)

A super insulated house in fort collins will cut down on your utilities and make the house very comfortable all year.  They are doing great things with small houses all over colorado at habitat for humanity - super insulated, radiant heating, and cheaper than you'd think since there's a lot of cost savings in the mechanicals (lower heating and cooling requierements).  The construction technology guys are pretty open about sharing...check out the denver habitat office for the right person to talk to.

Personally if I were in your shoes I'd do a slab on grade foundation with radiant heating and foam for wall insulation or extra thick walls and celulose.

Keep checking craigslist - just recently a guy on a comerical job was giving away "scrap" foam board -- packed solid it was 16' square and 4' tall!  

Fort collins is in a good location for passive solar winter heating as well - essentially large overhangs to block summer sun with windows in the right places for winter heat when the sun is low.   A step further is a sun room with lots of glass (often just reused slider door glass) that can be blocked from the main house in the summer, but is open and heats the house in the winter.

There is a lot you can do in that climate - you're not too hot and not too cold.

Are you in town or out?   If you're a little higher up the hill the passive solar pays back even more.

 

Beer was created so carpenters wouldn't rule the world.

energy/insulation hesteria (post #207074, reply #5 of 25)

I think there is a hesteria out there over energy/insultaion.  In fact I sware Finehousing Building Mag must devote half it's issues to the subject showing what seems like 100s of ways to build "high energy" efficent homes.

The fact is there are dimenising returns on insulation.  This is an economic fact of every question in the world.  You could spend an infinite amount of money and still have a tiny amount of heat loss.  Does that make any sense.  Of course not.

Now one question is what is the cross over point.  There are many factors involved i that one question.  One of course is how long are you going to be in the house.  In someways it is a shame this is a question at all, since it would be nice if we all would make economic decsion which are right for the life of a property and not us personally.  but ....  Secondly what are current energy costs and projected future energy costs.  The first part of teh question is basic the second ... your guess is as good as my.  It is probably easy to say they will rise.  Thirdly, what is the "time value of your money", what return to you want or need or expect to make on each additional dollar spent on air sealing and insultation.  This is all complicated, and this is why most people on the board will (not tell you this but.. ) throw up their hands and basically tell you the more the better.

I know my parents have a house 2000 sq ft, two story, 2 x 4 walls, the old insulation board (probably R-1 1.2) instead of soldi sheathing, plastic vapor barrier inside, decent (?) atttic insulation, and their heting bill is about $120 during January with electric heat at $.08 / kw.  So ... what ... about $500 a year?  What you pay to cut that bill by $50?  Well at an expected rate of return of 10% you would pay $500.  Could you sheath an entire house with 2 inches of foam?  Could you use 2 x 8 instead of 2x6 for less than $500.  Could you spend the time and money in labor to do a mooney wall?  Etc.  These are the easy options.  Some of teh crazy stuff in FHB, woudl cost a small fortune.

Then there is the issue of the dew point and rotted walls if you use too little foam on the exterior of the sheathing.  And the added framing details to fir windows and doors out to accomadate.

So,  I say go for 2x6 framing (lumber saving techiques can not hurt your here and can not cost you), the best cellulose or dense pack FG at R21, If you have an attic go crazy with mountains of insulation there as it is easy with not heroic framing issues, and insulation crawlspaces and basements.  Pay attention to air sealling issues.  Then pay attention to air sealing issues.  this is the easy stuff.

Do teh math on spray foam.  It does not pay.  MY OPINION, other can disagree, but none will offer teh math.

Insulation (post #207074, reply #6 of 25)

Keep in mind that heat always moves to cold.

Therefore, it makes sense to have the insulation on the warm room side of the frame.

Having the insulation on the outside of the frame, means that you will be heating the frame and the spaces between the wood, you will also use more insulation and have greater problems eliminating heat bridges.

Having the insulation on the room side of the frame, means you use less insulation, if you use sheet polystyrene or a similar closed cell product, you can produce what is in effect a sealed plastic box. Completely eliminating all the usual heat bridges between the warm air inside and the cold air outside. 

From the inside, a skim plaster coat, dry wall, insulation, frame etc.

Not necessarily true.  The (post #207074, reply #7 of 25)

Not necessarily true.  The only difference in amount of insulation is the thickness of the walls at the corners -- otherwise surface area is surface area.  And in some cases you can more completely cover the structure (eliminate heat bridges) by insulating on the outside.

Consider, eg, how you must handle intersecting interior walls if you insulate on the inside.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Which is easier? (post #207074, reply #8 of 25)

I still think there is a bit of hesteria about insulation/energy.  That said, if you want walls with greater than an R21 afforded by FG and 2x6 studs, which is easier, foam on sheathing or foam on interior walls.  ALmost all windows need jam extentions regardless of the wall thickness so that is a non issue.  But trimming out windows and doors on the outside seems more complicated.  Then there is the issue of attaching siding over foam (nailing stripes?  Long screws?????)  ANd of course there is the dew point issue with foam on the exterior?

The whole thing seems not worth the money, the labor, the time, and the risk.  Even teh Mooney wall which seems easier seems iffy on many of the same counts.  But which is better if you decide to go that route. ??

How so? (post #207074, reply #9 of 25)

 Even teh Mooney wall which seems easier seems iffy on many of the same counts.

 

How so?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Cost, labor, trimming, pay back (post #207074, reply #10 of 25)

Cost, labor, trimming, pay back.

The biggest iffy is the pay back.  What R value are you gettng in a Mooney wall, I don't recall?  Still alot of time, labor, trimming....

Don't get me wrong, of all the double wall stragegies, 2 x 10 walls, I-Joist walls, exterior sheathing, etc.  I like the Mooney wall the best.

Trimming doors and windows on the inside would be pretty straight forward.

So id 2x6 walls give you R 21 (forgetting thermal bridging), what does  Mooney get you?  Remind me.

do (post #207074, reply #11 of 25)

do, do a search for mooney wall and include Mike Smiths name for a bunch of discussion.

You can do that as easy as me.

I was remembering a figured R-18 with a whole lot less thermal bridgeing than you'd get with an R-19 fibreglass/6" wall.

So, look here and then look some more.

http://forums.finehomebuilding.com/breaktime/energy-heating-insulation/mooney-wall

Tell me what you find.

 

When you get done, I'll tell you the construction of this house of ours that recently had an energy audit and what I didn't see when we scanned our walls with the 4000 dollar camera.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Why hold us all in suspence? (post #207074, reply #12 of 25)

I have been to the sites before.  Like you I don't recall any of the figures (R values), if any were offered.  As I also said, I like the concept, and think it makes the most sense of all the other crazy double wall etal stuff.

Sure, I would be interested in what you found.  But I would be more interested to know how much more it cost to achieve WAHT SPECIFIC dollar savings in heating!  This is my entier point.  I am sure we could get heating cost down to near zero if we spend $1,000,000 to achieve it, but does that make any sense?  Of course not.  So the original posters point is, where is the cross over point between dollars spent and dollars saved.  As I have also said NOT ONE poster I can recall or ONE FHB article runs the numbers.  Too lazy?  Just don't know?  Or what?  But what it appears to me is that what is said is "well it can't hurt, well you are going to save energy, well......"

I am sure your camera shows limited thermal bridging.  Ok, fine, but does that save you in dollars and cents?

Like to hear from you in detail.

Do (post #207074, reply #13 of 25)

I think the first thing you need to do is set a time limit on the structure with you in it.  If you're going to live in it 7 yrs, no way you get pay back.  Live in it 20 or more, and that payback seems quite easy.  Give the place to your heirs or sell it in your golden yrs?   maybe get more or sell easier if you've got the right info for a prospective buyer.

Next, set a thermometer setting that will keep you comfortable-hell, turning down the heat to 55 at night, down when you leave for the day, down when the sun comes in, up the other times but only to 63 or 5 will save you all sorts of money..............but what's that say to comfort level?  If you want to go that route, buy a good programable thermostat or find a way to "program" your system according to your lifestyle and the weather report.

Siting your house properly, with do regard to prevailing winds, wind blocks and all the logisical settings you can muster-more savings no?

We haven't even touched on insulation or R-value yet.

 

25 yrs ago when we built this place, I thought I knew what I was doing.  I did in many ways, but then again,our insulation is batt fibreglas.  Saving grace I'd guess, good site management.  Add to that, utilizing the passive gains in winter and natural and passive shading in the summer.  These are building properly to be able to gain a benefit at all.  You're probably going to have an overhang, why not build it to work for you down the road.  You're going to have windows, so why not put them where they'll do the most good, rather than be just an energy drain.  While you're at it-situate the house so those windows have something to look at!

This is what the energy audit camera showed-no lines in the 1st floor walls, no lines in the 2nd floor walls.

From the outside-first floor:  

Built into the hill with a stepped foundation-8"block-filled cores not holding rebar and poured solid, with vermiculite.  (I had a particulate mask on while filling-hope that worked.)  Over the block to the outside is 2" rigid fibreglass insulation (that doubles as a water drain on it's outter 1/4" of surface)  R-value of that?  beats me-it was over 20 yrs ago-Look up Warm and Dri, might have it listed.  

 

Because the found. is stepped up the hill, didn't want a ledge in or out-and the block has that 2" of rigid on it...............the stud walls that take it to the first floor ceiling I built out of 2x10's.  All wall framing-2ft centers.  Outside of that covered with 1" Dow (seems to me R-7-look that up also).  Did not use ply at corners, diagonally braced with metal strapping.   Over the 1" Dow, vertical furring, 30lb felt (when it was thick), Siding-Shakertown cedar shingles affixed to a 2 course by 8' 3/8's plywood backer.

2nd Floor-2x6 @ 2' centers.  Again, same exterior detail as 1st floor.

All stud cavities meticulously (as I could) filled with fibreglas batts.  Inside of that-6 mil visqueen, then 5/8's firecode.

 

To flush up the block wall on the inside with those 2x10's, 3/4 inch Dow.

Perimeter of slab holding hydronic tubing-1" Dow (now, would be thicker).  Below slab-2" Dow (again, now would be thicker or some other product that performs better).

Heat source-Tulikivi Masonry Soapstone heater with if I remember 6000 lbs of soapstone mass).  This used for spring and fall heat exclusively and as a comfort maker/gas saver,  every nite and weekend throughout the winter .  Main heat source in winter, gas boiler-23 yr old 90some efficient.

Cooling-attic fan to draw cool nite air in, shut up house-temp rise throughout the day only a couple degrees.  So, 65 outside at nite-67 inside at end of day.  For those HOT muggy summer days here in NW Oh.  ONE window air conditioner-fits in a second story great room 2' casement window.  Will cool the whole house, not just "sort of".  It adds a dollar a day of use to our electric bill (and our power costs are not low).

Somewhere I think I figured the downstairs walls above the block was somewhere in the high 30's R-value, 2nd story was a bit less.

 

Up in the attic-ONLY 8" of fibreglass batts-way undersized in todays standards and now that all the accumulated crap from 20 yrs of living and a daughter that's moved away..............there goes that idea of topping off what we have up there.

Forced to by economics, then for sure - jettison the crap and add more blown probably cells.  Until then-there's got to be some sort of rating for boxes of crap.

Our down fall, can lights that are too old to have been air tites.  Minimal insulation over them.

And the glass at nite.  Our beautiful views do have a drain of heat at night-or rather a source for cold.

 

Now, for a 2700 sf house,   in January of last yr, our coldest month-105 ccf of gas used.  For boiler, dryer, stove and domestic hot water (tank htd by boiler)  Total yearly usage- 632ccf    Summer months-20-25 ccf's.  About 500 ccf's used from Nov. thru March.  

Remember, the masonry heater use-burn up maybe 1 cord per yr.   Cost if bought-about 150.00

 

And, as to your question about thermal bridging savings?   hell yes-add up all those lines you see in a commonly built home and it's got to be like leaving a window open all year.   Same goes with cooling in the summer, no?

 

That's all I got-you'll have to do the R hunting and figuring-my house is built and we're living in it.

Best of luck on yours.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Couple of points (post #207074, reply #16 of 25)

FIrst off, this is not my thread.  I was not asking for suggestions on techiques (althought quite welcome).  I was responding to the original poster who asked about over kill, to which I relpied by questioning the lengths and expense people go to save energy with out really running any numbers.  I think alot of people just like teh idea of building "well" or just don't mind spending the money on FAITH that it will pay off.

Seconndly, you mention payback.  As a professional in financial anaylsis I will say payback is a bad bad measure of return on investment.  If I promise to pay you $1 in five years what woudl you be willing to give me today for that promise?  One dollar?  No you would not.  Let us say you would be willing to give me 50 cents today for that dollar, then how much would you pay me for $1 in six yers?  Another 50 cents?  No, you would pay me even less for that dollar since you have to wait another year to get it.  THerefore teh point is that saving $1 ten years from now is amouts worht nothing to you. So very very roughly a payback period of greater than 7 or 10 years, depending on your "cost of capita" or your "required rate of return" means you should not make the investment.

As for thermal bridging, thermal bridging is also a point of some hesteria.  Thermal bridging is NOT more than just a low R value section of a wal or roof.  Teh 2x6 stud is something like an R-5, so if you have insulation of R 19 between teh studs (14 1/2 inches) to average is 17.7 for  16 inch section of wall.  Simple as that.  So ok I don't have 19, I have 17.7 (less of course becuase you have headers, double studs, etc.).  So really addressing thermal bridgin is just addig insulation to the stud, and by default the whole wall.

Overall, my view is that I like you have personal experience with a particular house my father built 35 years ago.  2 x 4 walls, FG, insultation board for sheathing (R- 1+), Plastic VB, 2 inch bead foam on crawlspace walls, FG and  Newsprint stuff in the attic, two story 1900 sq ft.  The highest winter heating bill in Zone 5 (i think, Canadian border) is about $120 with electric heat.  So even if the exact same house were built today with whatever insulation techique yo chose, could you save 50% of the bill?  LEt us say you could, that would mean saving $300 each year (5 months times $60, that might be high as it includes shoulder months).  How much woulld you have to spend to save that?  If you have to pay $3000, forget it,

Granted I would build that house differently today, but I would not go to great heroics to do it.   Forget foam, just too dare expensive, and I would not spend the money or lose teh floor space with duble walls, etc.    

One afterthought.............(ha ha) (post #207074, reply #14 of 25)

orientation of the dwelling.

This house is a two story down hill. Downhill faces the south (with the few degrees off for proper passive siting).  Our prevailing wind-from the SW.  That puts the corner of the house pointing at the wind commonly coming at us.  Here in NW Oh, that's usually a stiff breeze-not much to stop it in these farmlands.  How much cooling in the winter from a constant breeze on a house?  beats me, but we don't feel the wind here around the house as much as we feel it walking the dog 500 ft away up on the high ground in the neighborhood.  Not scientific, take from that what you will.

We are in the woods on a hill.  The wind comes along the river valley and up the hill.  If you look at those line things that show air movement-it goes straight till it hits something in it's way.  The trees and hill tend to direct that wind up and over the house. 

So, just siting the dwelling either properly or luckily, can have a beneficial effect on our comfort inside.

And, for all intents and purposes-it's free.  That is, it didn't cost extra to get the gain.

no?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


Superinsulated House (post #207074, reply #15 of 25)

I don’t think one can determine exactly how much insulation to use.  There are too many variables to the calculation.  There is some practical reasonable cutoff point of maximum insulation, and there is average consensus of adequate insulation.  I believe that if insulation is increased from the average consensus to the maximum, a reduction of heating energy cost of 50-75% is achievable.  I see that as the workable range of improvement.

While that cutoff point of maximum insulation cannot be found with specific certainty, it can be estimated.  A lot of where that point is theoretically located depends on the individual preference as to how much you are willing to invest upfront to accrue a return over time that will eventually exceed the upfront investment.  It also depends on how much you value comfort because some of the payback is added comfort.  But, in any case, what I would do is find that point as accurately as possible, and then add a substantial extra amount of insulation just for good measure and certainty. 

For me, in Minnesota, that comes out to wall insulation of about R-50, and a vaulted ceiling/cold roof insulation of about R-100.  I am working on a house design with those values.  There are other factors such as reducing window area from what is typical somewhat, and minimizing thermal bridging.  Also included is a high performance basement with a lot of attention to the insulation and vapor control scheme.

This is a double stud wall system with parallel chord scissors trusses for the roof system.  It is hard to break away from 2 X 6 studs and 2 X 12 rafters, but I conclude that I must in order to get to the R-values I want.  To my thinking, trying to get to those values with the single member envelope leads to some compromise and insulation cost that outweighs the cost of the double member envelope.  For a variety of reasons, I rule out using spray foam.       

Of course one could determine how much insulation to use (post #207074, reply #17 of 25)

Of course one could determine how much insulation to use.  We just don't want to do it.  Teh fact taht someone has come up  with codes requirements is a start.  They are determined based on some cost benefit anaylsis.  However, having said that in this enironment of "we must build windmills to generate 30 cent a KW energy when we can generate the same KW for 10 cents" who is to say what potential mental disorder is suffered by code writers or municipalitics (especially in CA or OR).  I digess.

I mean really, what will it cost you to get R100 in the roof vs what it would cost you to get R45ish?  This is a number you should be able to figure out pretty easily.  But my previous points are made by the fact that you (not trying to get personal) appear not to know or to care.  ANd I am not sure if teh benefit side of teh equation gives you linear results, ie does doubling teh insulation gieve you a linear 50% saving?  Even if it does, does it makes sense to double your expenditure to save only half?  Diminishing returns.

All interesting questions.

Yes, I know what you mean (post #207074, reply #18 of 25)

Yes, I know what you mean when you say that I appear not to know or care.  That is the way it would seem if there were no other explanation to what I am saying.  It would appear that I am just shooting from the hip.  But there is another explanation. 

To start with, I deeply care.   And I have come to realize that the notion that there is some exact mathematical/scientific answer is an unreasonable expectation.  It is unreasonable because there are so many factors that must go into the calculation, and those can only be estimates, educated guesses, and hunches.  About the only factors that are actually known are the price of energy and insulation today.

You could do an energy model of a proposed house.  At least then, you would have accounted for thermal bridging, windows, doors, etc.  But even that requires a lot of input factors.  If ten people each did a model of the same house would they all get the same result?  In any case, the model is just the beginning.  There is the framing cost versus higher R-value insulation like spray foam that can save framing cost by using a thinner insulation layer.  But then you also have the risks associated with spray foam chemistry being off, and thus not delivering its full R-value potential, or shrinking too much, or never fully curing.   Such site-made variables can be avoided by the use of a manufactured product such as XPF or fiberglass batts. 

But let’s look at this from your perspective.  You asked about the cost difference between R-45 and R-100 in the roof.   Well, the insulation would be more than double.  There would be added cost in the increased height of the scissors trusses.   Some people minimize insulation upfront, and add more later.  This can be more costly than adding it all at once because of the need to open up cavities, possibly enlarge them, and then finishing them back closed.  Furthermore, insulation today will cost less than the same insulation in the future, and it never wears out, so it is cheaper to build all the R-value upfront in terms of just insulation cost.  Waiting to add more insulation in the future is a gamble that energy prices will not rise too much.  Yet I see the distinct possibility that energy prices will rise faster than any commodity price increase in history within the next 15 years.   Building a house includes far more cost than just insulation.  How much is it worth to compromise the thermal performance and comfort of that whole big investment just to save a little money on insulation?  

So you tell me how you would determine how many inches of what type of insulation to use in the roof system for the vaulted ceiling.  You don’t need to come up with the number.  Just tell me how you would arrive at.    

I look at it in reverse (post #207074, reply #19 of 25)

I look at it in reverse.  In a previous post I posted that I know personally a house with basic insulation, R14 walls, I guess R 35 in the attic, 1900+/- sq ft, and it cost about $700 seasonally to heat.  SO looking at it in reverse, what would I pay to cut that bill in half.  I think that is a tall order, but let's look at it.  If cut in half I would save $350 a year.  How much would I be willing to pay in additional building costs to say $350 each year?  The financial math gives you the answer at $3500 assuming you want a 10% return on your money.

So, the easy math is the cost of buildign upgrades.  How much does your double wall cost you?  Easy, math, cout the stubs, add up the cost of the insulation.  IF you have a builder you get a quote from him.  My guess is you start monkeying around with framing strategies and the money adds up really fast and your $3500 is gone in a flash.  I would likely not argue too much with the cheap low hanging fruit of thicker attic insulation, no framing and little added labor.

And remember, I think (big word) cutting heating cost by one half is a big order.

Another example or thought is spray foam.  It appears that you are not in favor for health reason, but the shear cost is enough to scare me off.  I hear numbers like $6000 over traditional insulation for a house like the one about.  The return on that investment is negative.  Now people have a cult following and or just plain take it on faith that get their money back.  I just don't see it.

The math on the construction side of things is not that hard.  Surely you must know what the upcharge for your proposed buiilding plan is?  IF not it can't be that hard to figure out.  And then I would think you could ask around and see what it costs neighbors to heat an equal sized house.  You could do so very rough thoughts with that information.

Assume that neighbors house has R -19 walls and R-40 - R 50 attic.  If you plan to double that, I would guess you could guess that your heating would be half what your neighbor claims.  Then compare that to your cost of your upgraded insulation system.  (Still don't recall if heating expense is inversely propotional to the increase in R value.  I think FHB did an article on that.

For my new home, I plan to do R-21 walls, maybe a bit better in gables where I will frame for board and batten so will do a "reverse mooney" to get blocking for board siding.  I will get R -45 in cathedral ceiling with furred out foam under rathers (thermal bridging).  Attic will get dumped with R-60ish.  Just no special framing expenses and no expensive foam.  If my mom is paying $700 to heat her house, mine with 50 % more insulation can do worse. And of course, I will be very careful with air sealing which I believe is hugh and again cheap.  My bottom line is insulation is cheap: framing, labor and foam are not.

Good discussion. 

I think your approach sounds (post #207074, reply #20 of 25)

I think your approach sounds reasonable.  Everything that I am saying about the issue is stipulated on a new house starting with a clean sheet of paper.  A remodel has a lot more limitations to what can be done, so that simplifies the cost/benefit calculation. 

What I am talking about pertaining to the insulation question is a high performance, superinsulated house that goes as far as possible in every detail to maximize its comfort and heating energy efficiency.  My concept is much more than just an above average amount of insulation.  It blends the superinsulation with other attributes that complement the energy efficiency objective such as a compact, space efficient, open plan with a simple, non-sprawling layout.  I compensate for the compactness and simplicity with exceptionally high quality materials, components, detailing, and finishes; and first class heating and ventilation systems.   Also included is impeccable workmanship and framing design. 

So, it is a personal choice to do something rather unique, and many people might decide that they are not interested in such perfection.  In building a house, there is always the prevailing undercurrent pull to do everything as cheaply as possible because the overall expenditure is so large.  Most people push back against that to some extent, but it still rules as an underlying premise.  I am pushing back against that undercurrent as much as possible.  I want the house to be more like a precision machine than an architectural abode.  What I am proposing is a building concept that I will build.  I would not rely on the building trades to produce the quality that I want. 

My primary objection to spray foam is not the health effect, but rather, it is that the material is site-made by installers who may or may not be competent.  There is a large variety of component brands and chemistry, plus stipulations on how they are to be used and mixed.  Installation technique also comes into play.  There is something about spray foam that is seductive to certain people, and it seems to me that those people are attracted to the panacea of foam in eliminating the need for thicker framing due to its high R-value, and eliminating the need for a vapor barrier.  And as you say, the cost is very high.  I choose to save the high cost of foam and spend the money on a thicker frame and insulation layer consisting of a manufactured product. 

SIP construction (post #207074, reply #21 of 25)

Build with SIPs and foam the joints. 

Response to Perry, Post 23,` (post #207074, reply #23 of 25)

I would have responded to Perry's post, but the annoying add is covering the bottom half of his post. 

The problems I have seen with joints in SIPs is bad details when they are built.  If the joints are done well they are very solid structurally.  Adding the foam to seal any voids in the foam at the joint just makes them air and weather tight, and not any stronger. 

A good structural joint that isn't properly sealed allows air/moisture to penetrate. 

A lot of people have problems (post #207074, reply #22 of 25)

A lot of people have problems with SIPs.

The reason, buildings move due to the effects of wind, sun and cold.

Over time, the joins open, water vapor gets in, wood rots. Spray foam as a jointing material is not the answer.

If you intend to use SIPs then you must take great care to prevent water vapor escaping from the home and entering the joints, this can only be done using a water vapor proof plastic membrane.

What's been overkilled is (post #207074, reply #24 of 25)

What's been overkilled is this thread.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Threads have a life of their own (post #207074, reply #25 of 25)

The zig and zag.  What shingles are best?