Replies

1. 
   xMikeSmith | Dec 22, 2002 07:39pm | #1

   yes, in jobs where higher levels of insulation were worth the price ( eg: electric heat ).. we use 1" high density EPS with furring  on the INSIDE.. we used to use polyiso.. but it was not as cost effective as EPS.. and we use dens-pak cellulose behind the EPS... not fiberglass

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

2. 
   Piffin | Dec 22, 2002 09:12pm | #2

   Yes, you are on the right track to doing it right. You have also wandered into the the wasteland laft behind after the last battle of the vent wars. As with the DMZ in Korea, it is an uneasy place to find yourself.

   ;)

   .

   Excellence is its own reward!

   "The first rule is to keep an untroubled spirit.

   The second is to look things in the face and know them for what they are."

   --Marcus Aurelius

3. 
   BillHartmann | Dec 22, 2002 09:25pm | #3

   You might also want to get the Building Science Book for your climate. Or check with your local library.

   The book has lots more details and options in it.

4. 
   don26299 | Dec 23, 2002 02:02am | #4

   Yes we have used unfaced FG in the walls and ceilings and 1 in R Board inside with great success (west central Illinois).  We use plywood or chipboard outside with Tyvek over that. 

   The CIPS energy consultant long ago advised us against visqueen under SR.  He said he had learned this over 25 years before that. 

   I have heard other contractors talking about mildew and moisture problems here with visqueen.  One job they removed the ceiling in order to remove the visqueen.   My theory is that you can get almost instant condensation on visqueen.   The R Board, however, will disperse the heat or cold on either side and you will have a hard time getting condensation droplets to form.  This covering of all the wood really makes for dramatic results heating and cooling too.

   Surely the climate makes a great difference on this,  but my experience with visqueen as a vapor barrier is the exact opposite of what I have read in many articles, including FHB.  I am NOT AN EXPERT in this field, but I won't be using VQ unless the customer insists at his own risk.

5. 
   don26299 | Dec 24, 2002 08:30pm | #5

   Here's what I would do if I was building a house here in midwestern Illinois as far as insulation:  R13 unfaced fibreglass in walls.  plywood or chipboard outside with Tyvek over.  Inside 1 in R Board with 5/8 SR over.  Ceilings: 5/8 SR, 1 in R Board, 12 in fibreglass unfaced.  Ridge and soffet vents with Proper Vents.   What's wrong with this anybody?

1. 
   xMikeSmith | Dec 24, 2002 09:37pm | #6

   you mean besides the fiberglass ?Mike Smith   Rhode Island : Design / Build / Repair / Restore

1. 
   don26299 | Dec 26, 2002 05:43am | #7

   What is your suggestion about the fibreglass?

1. 
   xMikeSmith | Dec 26, 2002 07:48am | #8

   don't use it.. it is impossible to get a draft tight fit in any bay... switch your specs over to dens-pak cellulose...we used to use all fiberglass in the walls ,  and cells in the attics..

   we switched over to 100% cells about 3 years ago..

   here's a link to the system we use..

   http://www.regalind.com/technical.htm..

    other than the fiberglass, we use a lot of the same techniques you list.. with one exception.. in the wall system, we horizonatally strap the walls at 16" OC..we use 4" sq. elec. boxes with a 1.5" plaster collar

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

1. 
   BillHartmann | Dec 26, 2002 07:23pm | #9

   ".we use 4" sq. elec. boxes with a 1.5" plaster collar"

   Are those available in bigger versions? What do you do at say a door where you might want 2-4 switches.

2. 
   xMikeSmith | Dec 26, 2002 08:50pm | #10

   1st... in the exterior walls is the only place we do this... so.. we try to keep the device boxes to just what we need.. if an alternate location makes sense.. we get it out of the exterior wall..

   i'll have to go back and look at what we did for ganging so i can give you the real answerMike Smith   Rhode Island : Design / Build / Repair / Restore

3. 
   don26299 | Dec 27, 2002 06:18am | #11

   Would you mind explaining the strapping.  I can think of some things, but I may be missing the point.  Thanks

4. 
   xMikeSmith | Dec 27, 2002 07:39am | #12

   putting 1" or 2" foam  ( we use EPS Performguard ) on the interior presents a couple of problems.. most have to do with there being no nail base behind the sheetrock / blueboard..

    if you furr your walls , you eliminate  those problems & you gain a couple of things..

    (1) you can blow dens-pak cellulose behind the foam and it won't blow the foam off the wall

   (2) you gain another 3/4 " of space BEHIND the elec. devices .. space for insulation..

   (3) you have a nailbase for trim around doors, built-ins , baseboard & molding

   (4) you have a better surface for hanging your drywall / blueboard without crushing the foamboardMike Smith   Rhode Island : Design / Build / Repair / Restore

5. 
   Mongo | Dec 27, 2002 01:53pm | #13

   Mike,

   Looking for alternative techniques for the same buildng methods...how do you detail cells in rafter bays with regards to ventiing the underside of the sheathing? Manufacturered baffles? What do you use that stands up to DP cells?

   Thanks, Mongo

6. 
   xMikeSmith | Dec 27, 2002 03:38pm | #14

   Mongo, we use Propa-vent .. one of those closed cell egg carton type baffles..

    here's one view of the upper roof.. the baffle only extends a comfortable distance past  the cell fill mark ( in this case 24" ).. so the upper roof of this gambrel will have cells  12" deep and tapering up to 24"  then leveling off over the balance of the attic space..

    the 2d view is at the plate line on the lower roof. here we use 2x8 rafters to get more insulation room... the thinnest point will be at the upper plate  ... about 6".

   at the base we dropped a vertical plywood back wall ( knee wall ) so we can get about 16" at the floor level..

   if this had been one of our energy houses, and we were trying to maximize the R-values.. we'd add 1"   or 2" EPS foam to the interior face of the rafters and stud walls before we furred it.. in this case.. we'll concentrate on a lot of attic insulation...Mike Smith   Rhode Island : Design / Build / Repair / Restore

   
7. 
   Mongo | Dec 28, 2002 08:21am | #15

   Thanks for the reply and the pics. Are those baffles strong enough to not be crushed by dense-packing cells in a closed rafter bay?

   Thanks again.

8. 
   xMikeSmith | Dec 28, 2002 05:12pm | #16

   yes, absolutely.. they get stapled on the 3 flanges,  Mike Smith   Rhode Island : Design / Build / Repair / Restore

6. 
   sphaugh | Dec 28, 2002 09:42pm | #17

   shows it pretty clearly on inside face of studs in heating climates. 

   http://www.buildingscience.com/housesthatwork/

   scroll down & select your climate.  Joe is among the first to promote outer face vapor barrier & sealed attics in cooling climates.. but I find that his "science" is pretty good - lots of sources & real world research cited throughout.

   (When I lived & worked in SC - up til 9/02 - I was told by mechanical contractors that Joe is a nut.  Supposedly some building science professor at Clemson refuted his work but I could NEVER get them to share any facts or written opinion.  Since my in-laws are all Clemson grads, I guess I just have to go with JOE!)