Hello,
I am a long time reader, first time poster.
We have a two story house on the north shore of Lake Ontario, near Kingston. We are planning on a renovation to convert the building from seasonal use to all season occupancy.
My question concerns upgrading R value of insulation of existing walls. The walls are 2 x 4 framed, insulated with fiberglas batts, hardboard exterior sheathed with poly vapour barrier and drywall installed on the interior. The exterior walls are slated to be wrapped with Tyvek, with new vinyl siding installed.
A local contractor has proposed using 1″ rigid foam to upgrade insulating capacity. He proposes removing all interior drywall, installing the foam on the inside of the studs and then reapplying vapour barrier and reinstalling drywall.
It seems to me that the same thing could be accomplished by installing the the foam on the outside on top of the sheathing then Tyvek, then siding.
My reasoning is that the exterior application will be far less involved. The builder says that this would be a problem due to two layers of vapour barrier (the foam and the poly).
I would appreciate advice from the group on this issue.
Thanks,
Allan
Replies
Tell your builder to get him/herself some vapour permeable rigid foam or to just tear the plastic film off immpermeable rigid foam and use it on the outside of the wall BEFORE Tyvek and then vinyl siding. It goes on fast, it increases R, it solves thermal bridging, it's all good. This is an extremely common Canadian practice (rigid foam under vinyl) and your contractor's unfamiliarity with it would raise a red flag if I were in your shoes, although they are right to say that you'll be in trouble if you use the stuff with the barrier intact. One thing to watch, especially if the contractor has not installed like this before, is how they detail the windows and doors, since the added thickness of the foam creates a few (easily solved) problems at these openings.
JT
Cartwright, MB
in your colder heating climate, the foam belongs on the inside of the studs. Outside can cause buildup of condenstaiton and maol problems.
But an entire interior redo is in the works if you already have a finished house. It would be hard to reconcile costs even wioth higher fuel cost now.
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This is essentially what the builder said. Another piece of information is that he plans to to remove all dw, poly and fiberglas from the outside walls first. This is partly to facilitate the electrician's modifications to wiring in those walls, partly to update the electrical boxes to current energy standards. The plan is to save and resuse as many batts as possible.
This clears the way for the rigid foam install on the inside. The home is heated with electric baseboard heaters supplemented with propane fireplace in living room.
Any further thoughts?
if he is going that deep, with removing the FG batts, throw them away. Convection loops in FG batts reduce the effectiveness in a cold wind to almost nothing. He should be installing n insulation that eliminates that convection heat loss. Spray foam in place such as Corbond ( Google Walls that work) or other urethene foams, or use denspak cells ( cellulose blown in tight enough to eliminate settling and convection loss) or BIBBS ( Blown in Blanket systems of chopped fibreglass similarly packed)you should also use this site's search to find discussions on "mooney walls" if you are able to stand losing the dimensional space tothe interior.Then, consider junking that electric baseborad heat. It is the cheapest to install but the most expensive to run in most places - wait - did you say upstate NY? - if you are buying power from niagra Mohawk and own stock in the company, you mioght be one of the few that advise doesn't apply to.
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Thank you all for your input.
Much appreciated.
If your builder is removing the 'rock, poly, and insulation anyway, you should ignore everything I said earlier about choosing rigid foam on the outside and instead listen to these other guys about spraying in. Jeff
If you are going to remove the drywall why not use Astro-Foil on the inside, R-7.2. Look at http://www.insul.net
astro foil has its uses, but this one would make it nearly useless
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Piffin, why do you say it would be useless in this application? If he is removing the drywall he can add a layer of Astro-Foil to the inside of the studs and gain R 7.4 of insulation value in a 1/2" space. I have agreed with most of your posting and have read them all and gained some insight to various problems. So, once again, why do you say it would be useless.
There is no way that astro foil will provide that much insulation. That is why. Their projections and claims of the R-value are equivalent values. They go through a complicated description of how they arrive at their claims, but in fact, they only have that value when appplied to radiant heat loss, not convective or conductive heat loss. Add to this the fact that the effectiveness of radiant products has been tested and shown to be ineffetive unless there is at least an inch of free air space in front of the radiant barrier. (That sort of design increases the covective heat loss but isn't what you are suggesting anyway) I think it is a great product for certain applications. I use a couple thousand dollars worth of it every year, but the3 interior of this wal is not one where it would be worth the troubel to install it. Rigid foam panels would be far more effective. he can get R-7 out of an inch that way.
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Study their own technical reports and installation specs. The R-values assumed are when installed according to thier specs only. The drawings they provide show it with an air space to the interior of the astrofoil.Also, not that when measured according to various methods, their own reports show varying results from R-4.2 up to R-15. The result of a projected R7 more or less, is for horizontaal heat loss in certain settings and with specific installation. I would far rather have a known qulity in the foam than an uncertain value in the astrofoil in this instance.
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Piffin, Atro-E does not have a R-15 rating on any of their sheets. Therefore I must assume that you are using a different product.
Forgive me if i round off from 14point-something What is your interest in pushing the stuff for all applications? Do you make a living selling it? Trying to justify having used it on your own house? You really seem bent on forcing me to use it even in places where it is not appropriate or where other products are a better choice.
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PIffan,
You make an excellant point regarding astro foil..
while it has merits in the south here in Northern heating climates it pretty much is worthless.. Sprayed in foam would seem to be the best for this particular application...
Even in the north, there are good applications for it.For instance, we have a lot of rubble stone foundations to "crawl" spaces anywhere from 3' to 6' deep. These stone wals are 18" to 24" thick, leak water sometimes, and are worthless as insualtion.
So it is common to drape Astro-foil over it, fastening it to the sills, and realize a big gain.Another good location for it is when doing staple up PEX heat between old floor joists. These can vary in layout from 12" to 32" and can be peeled logs even. Stapling up the Astro with reflective spaces is the easiest and possibly the best solution for driving the heat up with out wasting it into the cellar.
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Piffan,
that is an interesting tidbit, do you think you could use it to staple up heat tubing as well? They sell an aluminum plate for the job, but it's realitively expensive and pretty labor intensive (in that you need to form each piece yourself)
We use the plates that the pex snaps into. The primary purpose of those is dual - to hold it in place, and to conduct heat from the tube to the larger contact surface making it a conductant and radiant heat delivery system. The Astrofoil stapled up gets placed an inch, more or less, below the Pex and plates, to reflect the heat back upward. Without insulation, the plates would be delivering more heat to the cellar that through the floor above it.
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Piffan,
Thank you! That's exactly what radiantec suggests as well, but my thoughts were since heat rises wouldn't it only be a matter of time before it (heat) rose back up? Just wondering out loud since I'm pretty sure I'll do as radiantec suggests...
heat doesn't rise, warm air rises.So if you have an eight foot cellar, that is a lot of air to heat before it does much rising to heat upstairs. Believe me, I know, Before we got the last one Astrofoiled, the cellar was an uncomfortable 75-80° while the main floor was 65. Course the doors stayed open a lot while subs came and went and windows were openned for painting fumes. But I do think that more heat rose only when the cellar door was open to let the air rise.
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Piffan,
I'm not sure of the differance, warm air rises, Hmmm heat radiates right? and it warms up objects which radiate heat further. Now granted a metal would radiate heat at a faster rate than say a wood will (would?) but does that mean that once stability is reached everything should be the same tempurature? no that's not right because a radiator is much warmer than the floor under it.. Hmmm. I've gotta think here..
Insulation prevents the transmission of heat so if we assume that metal transmits heat more efficently then foam or wood will it can be assumed that the metal would warm the wood faster. Right? thus radiated heat from the metal will be prevented from passing the astrofoil and added to the heat already in the wood.. Or am I wrong?
Not sure I followed the reasoning there, but the conclusion is right
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There are 3 type of heat transfer, convection - which is warm air rising, conduction, and radiation.Now AL make a great conductor, but a piss poor radiate heat source.The term is emisivity and is similar to reflecttivity. The purpose of the AL plate is to conduct heat from the tubing to the floor. The floor then become a radiant souce of hear.Radiant head goes equally in all direction. Clearly you feel the radiant heat from the side of fireplace or wood stove.Since the radiant head goes in all directions you want to control it so that most of it goes into the floor and not the space below.Since it is radiant a reflective radiant barrier works well. Thus a foil product.
Piffan,
Not trying to beat a dead horse here but I guess either I'm confused have it wrong or need some guidance in this matter..
Imagine I put heating tubing under my subfloor without the plates that radiantic recommends..
You indicated that the basement would get warm, perhaps warmer than the floor above it.. Assuming no insulation between floors what would prevent the heat from the basement warming the floor above? Wouldn't both floors eventually reach the same tempurature?
You claim heat doesn't rise and I guess I understand that, in that heat radiates which warms objects etc... Those warm objects heat the air which rises,..... I don't know anybodywho builds a floor so tight as to prevent air from getting thru it even plywood flooring has edges which allow rain to leak thru so if rain can leak thru it can't air also leak past it? Since I'm not using plywood but 2x8's for flooring I'd imagine my floor would be more prone to leakage (but I digress) The warm air from below would eventually bring the floor to the tempurature of the basement below..
The problem is the floor and floor coverings are also an insulator. To get the upper floor warm, downstairs woud probably be unbearably hot.
rich1
Wood is a terrible insulator.. R 2 for a 3 1/2 inches.
You are right, but the heat still has to get through the floor. As a result, the lower space will be warmer than the top space.
BTW, air is actually a poor medium to transfer heat. The heated air will rise, but the btu's will have to be transfered from the air to the floor and back to the air. Suspended tube systems or with no transfer plates require a much higher water temp.
Edited 9/8/2005 11:28 pm ET by rich1
depends on the species and the moisture level. variesmt dry cedar logs are rayed in some books as high as R1.14 per inch
pine about .97/inch
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Understand that I'm not an expert in thermodynamics here"You indicated that the basement would get warm, perhaps warmer than the floor above it.. Assuming no insulation between floors what would prevent the heat from the basement warming the floor above? Wouldn't both floors eventually reach the same tempurature? "I think that you would alwaays have extra heat loss in the cellar. The only way you would reach perfect equilibrium is if there were absolutely no heat loss from the preiphery of the cellar - through walls, flooor, windows, etc.Also, to drive the heat to the upstairs, the cellar would always have to be warmer forth eheat energy to flow from the warm zpne to the cold zone.If those presumptions are correct, in heating the cellar to higher than living space, you increase the temp diffferential between interior and exterior which then increaswe the heat loss in the cellar.So, while losing more heat from the dcellar, you are still forced to heta it warmer than you want the main floor to be in order to be conmfortable there. instead of a 55° cellar and a 70° main floor, you are using extra energy to maintain a 75° cellar to be as comfortable on the main floor.In the house we did last winter, the slab heat was the only thing operating. The cellar was at 72°, the main was around 55° and the second floor was sometimes barely above freezing unless we turned on accessory electrical heat. This was without full insulation yet. Heat did rise to some extent, but not enough to offset the heat loss, so it is most comfortable and most efficient to deliver it to the room where you want it.That's my opinion, but I stand ready for correction by heating techies who know better.
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Piffan,
You make a good point and I'm in no position to argue it but would you please explain further?
In my case I have 9 foot ceilings in the basement, much of the basement is ICF's and has two inches of foam under the floor. however the north basement wall will only have two inches of foam and the concrete floor doesn't have any foam under it so given a ground temp of 55 there is potential for heat loss greater than the rest of the house (protected by SIP's)
I'm not sure why the upstairs would need to be colder. Warm air will rise untill it reaches the same tempurature right? so if the basement were say 5 degrees warmer wouldn't the rising heat cause the next floor to get to that temp (assuming no heat loss from open windows or lack of proper insulation)
I keep going back to Fords Model T's which used thermosyphoning to circulate the water rather than a water pump.. cold water settled and warm water rose... evan old fashioned homes used to use the power of rising heat to warm upper floors rather than blowing air..
Anyway with heat tubing on the floor above the basement the floor itself would warm up to a degree from direct radiation and what heat radiated into the basement would eventually seek to rise. Yes, we'd lose some heat into the basement and the inefficencies of it's insulational envelope but given a ground temp of 55 degrees and say an outside winter temp of say 20 below I'd think that if you are going to heat any room the best one would be the lowest one..
" I'm not sure why the upstairs would need to be colder."It simply is. You have a lot ot of resistance to heat loss in your basement the way it is constructed, but the floor itself still offers sopme resistance, so the basement would always need to be warmer to drive the heat to it
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Piffan,
That has me confused. You spoke about the floor in my basement but the heat source is 9 feet above the basement floor so any heat "loss" would require heat to radiate down 9 feet to warmup the basement floor and then conduct that heat loss into the 55 degree ground.. yes there would be some loss.. would that be as great as the loss from the next floors walls if the outside were at say minus 20? (but insulated with a six inch SIP?) not trying for numbers here, just a sense of how heat travels.
My sense is that heat travels from warm towards cold both thru radiation and conduction.. that radiation has a greater resistance than conduction.. conduction can be dramatically slowed thru the use of insulation.
That is all more or less truebut the nine feet of air has about the same resistance to heat loss as the inch of wood in the floor, so you would deliver the same heat energy to the whole cellar as to the main fllor. Then yoiu still need to heat the space above on the main floor, not just the floor itself
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Frenchy, when I moved into my house, I hadn't had time to insulate under the radiant above the basement. Lots of other things had bigger flames shooting from them at that point in my life. Like you, I figured that it didn't matter much and I planned to leave it uninsulated. Also like you, I have an ICF basement. Well, yeah, the first floor warmed. But the basement got unbearably hot. I couldn't work down there. So, I insulated and now things are hunky dory. The house still isn't quite done, but I believe that when a carpenter finishes a house, he has to sell it or die. Not wanting to do either right now, I'm proceeding slowly....
AndyAndy Engel
Senior editor, Fine Woodworking magazine
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Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
So can Anybody answer my question about the celotex board being used under neath the siding on the outside for retrofits, and new construction? Very common in Illinois........
Benefits? Disadvantages?When in doubt, get a bigger hammer!
I've wondered about that for quite a while.
Similar questions regarding the same have been voiced in old threads here but nothing really definite in answer was ever drawn as to a conclusion.
I'm thinking perhaps everyone is wanting to back off the question as it is a fairly common practice and no one really has an answer beyond opinion.
sleeps till noon but before it's dark...
Well you need to be specific about the material.Celotex is company name not a product. The company has gone bankrupt several years ago and the different products sold off.I don't know which, if any, carry a Celotex name.But Celotex made shingles, fiberboard sheating, and polyiso insulation/sheathing. And possibly others.
exactly
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okok, So this stuff is the 1/2 inch poli something (can't remember the technical name) sheathing.......
The sheets are yellow and say celotex on them in big letters. IT defininately is not a closed cell foam, the stuff feels more hollow, and it itches like crazy when you get it on your skin.
Anybody else know what I am talking about?
When in doubt, get a bigger hammer!
So now I had to re-read to see what the question was againSee, celotex used to make a homasote type product that was commonly used for sheathing and insulation board, generally asphalt saturated, and poor insulation but better than wood. The poor R-rating you mentioned made me think maybe that is what you were talking aboutBut the stuff you describne is a polyisoanurate between foil skins. it is vapor permeable except for that foil. But the R-value is 7.2 per inch, some of the best you can get.The question that applies is whether it is wise to apply it to the exterior of the wall. That depends on the climate. In a strong heating climate up north, it is better on the inside, while in a cooling climate, it serves better on the outside. in a moderate climate, a lot can depend on the overal thermal and vapor design.
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Thanks for the response.......
This stuff isn't in foil though.......I am going to look into it, and find out the exact product. I worked for a cotractor who swore by the stuff....
You have any good suggestions on books about insulating, and creating a proper barrier system??
When in doubt, get a bigger hammer!
http://www.buildingscience.com/all I know about it and more
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That sounds like the polyiso.Dow now makes it. IIRC the one of the names for the insulation was Tuff-R.There where several variants with plastic surfacing and I think some kind of fiberglass in addition to the foil.Here is the tuff-rhttp://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A//www.dow.com/styrofoam/na/iso/tuff_r.htm&ei=o3wjQ_jRG5icsQGI85n3AgAnd you can start here and look at the other verisonshttp://www.dow.com/styrofoam/na/
I've seen the stuff you're talking about used as sheathing on commercial buildings. Generally, they were slated to be brick clad, so assume an air space for moisture purposes. That's all I know.Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.
Andy,
That's exactly what radiantec suggests as well but it's nice to know that real world experiance backs them up, thanks!
The funny part is last winter I had 1/2 of the house timberframed with SIP's and the other 1/2 was a well insulated stick built.. on a cold day last winter I took a laser thermometer around the house and I could easily find any stud because it was 4 degrees colder than the space where the insulation was 49 to 53 degrees.. The ceiling's were 6 degrees warmer than the floor and they were less than 8 foot ceilings...
The portion that was built with SIP's was 68 degrees any place I looked at. the ceiling 28 feet up or the floor were both 68 degrees.. anyplace on the walls was 68 degrees..
There were 14 heat registers in the stick built portion of the house and I put a T in the duct work and ran one 4 inch duct into the basement under the SIP portion and ended it under the floor in the approximate middle of the addition..
Now there may be 1/2 to 3/4 of an inch between 2x8 floor boards so it was easy for heat to rise..
PS, you need to have someone with their mind engaged to staple it up there. I had a helper who, with an electric staple gun was so impressed with how fast he could work, that he forgot to think about where he was stapling when he got to the end, so I had to call the plumber back to make a repair in the line.
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Piffan,
Heh, Heh! Been there, done that! Oops! ;-)
I'm lucky in that there is no chance to staple thru the sub flooring. It's a full two inch thick!
I think that you are wanting to use the "foil" to help spread the heat like the aluminum plate does.No it won't work like that. The foil is microscopicaly thin and won't transfer any heat sideways.And beside in many version the foil is behind an buble air layer and won't get much conductive heat anyway.
Bill,
I had the idea that maybe it would radiate heat not that it would conduct it. the result would be much faster heat tube installation
Okay, are we talking about the same product? Astro-Foil, Astro-E, or are you maybe referring to Reflectix that is available at HD or Lowes? I am looking at the ASTM test results. ASTM C-236 (which is the insulation standard that insulation is rated by) list Downward heat flow of R-14.5, Upward R-4.9 and Horizontal R-7.0. Yes it needs a 1/2" air space to achieve this rating but in this application (removing the drywall) the 1/2" would not be a problem. Now, I know that reflectix does not stand by their test results, infact I have had been told by a Maryland building inspector that Reflectix would not provide the building department with a written R value.
I know it is dangerous to assume, but I would assume the existing insulation is going to remain. How then, do you maintain 1/2" airspace. And how do you insure the reflective side stays clean?
Astro-E comes in 16" and 24" tab rolls, the tab is 1/2", therefore by stapleing the tab to the inside of the stud (not the face) you get the air space. I have had some places that the FG in the wall has been overstuffed and in those places I have used the metal rods that FG installers use to put batts in ceilings.
If you do that, you compact the FG under it, and reduce the R-value of that complimentary product. Also, the FG will try to loft back out, in center of the space, bulging the astro until it is back in contact with the SR.The only way to use the tabbed astro is to furr out over it, or to use R15 FG in a 2x6 wall to maintain the required airspace.
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If you used (yes we are talking about the same product. I've had their technical sheets open too and they have three different reports with varying data in differing circumstances) the astrofoil in this wall, you would only be able to maintain a reflective air space by removing FG batts or by adding furring strips over the astro before sheetrocking. For the same depth of wall space, Foam would give a gauanteed R-rating not a theoretical one, and would not allow a concvection heat loss loop in that space, and would be easier to install.
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Piffin, I still don't understand "theoretical". The ASTM test results are figured the same for all insulation, FG, Foam, Astrofoil. If you don't take ASTM test results at face value then you must question; load bearing beams, plywood sheating, footings etc.
I don't take anything at face value. Every product we use in this business has certain properties, good and bad. Testing presented is done to show a product in the best light.For instance, testing of FG batt insulation is done with very little temperature differential. When you actually need the Rvalue, the differential is more like 50 -60 degrees. At that kind of ratio between inside and outside, there is a strong convection loop in the wall, creating a tremendous heat loss that does not exist when the temp diff is only 20° - that means that batts do not perform in real life the way they test in a lab.Same thing for the Astrofoil. It is tested under a certain set of ideal circumstances, which rarely exist in real life in real houses. As a matter of fact, I have seen the product used dozens of times in other houses and never once have I seen it installed according to instructions, leaving the air gap that is necessary for it to function as tested. You yoursaelf in this thread have even implied that you could just jam it in over the studs, behind the SR, and over the FG without a dimensional change, but that is definitely ignoring the advise of the manufacturer.
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So theoretically, to be placing a one inch foam product on the outside of the insulated wall and the remaining interior between the studding up to the inner wall surface with fiberglass batts, one will get a 'truer to testing' result from the FG batts seeing the main brunt of the coldest temp is negated by the foam board,
thus the outside cold temps that hit the fiberglass being not so extreme and warmer will lessen the intensity of the convection loop?
as Buddha said to the hotdog vendor .... "make me one with everything"
wrong directionThe foam panel goes across the interior side of the studs, serving as a thermal break and VB in addition to the insualtion upgradeshould I draw a picture? I have the CAD open.
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c'mon pif, I'm trying to find the validity for these guys that put foamboard sheets under their vinyl.
as Buddha said to the hotdog vendor .... "make me one with everything"
it's done....
takes that dollar a square vynal and gives you the illusion that it's the big buck stuff..Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
Piffin, I have gone back over my conversations and do not find where I said jamb it over the studs. No, I do not make a $ on the product. Yes, I have used it in my own house, my sons house, my sisters house and at least 2 dozen other houses. Try this (because I have one and have) insulate a house and use a thermal imagining camera to shoot it. This will be the true test of how well the insulation works. I just hate FG, have seen it get wet and not dry out, I have seen way too much mold behind FG with an interior vapor barrier. I use Tiger Foam (2inches) on the outside, and Astro-Foil on the inside giving me a R-21 in a 2x4 wall.
The question you were asked was about installing this in the wall in questionhere which had, has, and will have FG batts, so in the context of the discussion, it might have been wise to clarify that you were talking about a totally different scenario with your recommendation.now that you are more clear, your thermal design makes sense for a new construction, and you can see that you also use thermal bridge breaking foam as I was suggesting for this guys wall here, in addition to the Astrofoil, rather than instead of.
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TA DA! I think we found a common ground, not only do I use this method in new construction (which I do little of) but I use this in remodels. I have found that the vast majority of insulation that is 15+ years old is either installed wrong and/or is no longer effective.
Whew!!!;)
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I don't know where you got the numbers.Here is their report.http://www.insul.net/pdfTestResults/TD5_AF%20.pdfIt is based on a simulated basement wall with furning strips.And they come up with 4.8
Any of you older BTers remember the guy a few years back who was always pushing his radiant foil in about every post he made as the cure all for man's ills before he got booted off?
Today I'm a bettin' man that this is the return of the same.
as Buddha said to the hotdog vendor .... "make me one with everything"
Ok guys, a question? Would one inch celotex board on the outside of the house do any good? I believe it is a VR and not a VB. Down in my area a ton of guys are retrofitting houses by doing just that, and then siding over it.
I've siding a couple of new cons. houses that had colotex over the osb---???
I think the stuff is only like R2 or 3 though
--------------------------------------------------That's not ugly! Its custom!
So down there you are thinking of cooling, I take it, instead of heating.
Seems the VB/VR would be right then on the outside and some form of sealing insulation regardless of Rvalue would be better than none.
Got me wondering in that South American climate if the celotex was borate treated for insect intrusion?
as Buddha said to the hotdog vendor .... "make me one with everything"
Sorry, didn't clarify........Not here in Peru, but back home in Illinois.
Every thing here is masonry, and there is not insulation here...........When in doubt, get a bigger hammer!