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2" rigid insulation on older house

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  • 2" rigid insulation on older house

    i live in Canada where the temperature can be -40 to +40 celcius.i am going to replace the windows & doors and was thinking about putting 2" rigid insulation on the outside.couple of ?.is the insulation going to allow the house to breathe properly and do i need building paper on the outside or underneath the rigid.any answers or opinions would be appreciated

  • #2
    Re: 2" rigid insulation on older house

    A company I do a lot of work for completed a 160 unit upscale condominium complex last fall. The used 2" ridgid foam and Tyvek wrap with seam tape. Polyisocyanurate has an R value of about R7 per inch. Polystyrene foam or Dow foam normally found in home centers has an R value of about R5 per inch. With R19 batts in the 2X6 exterior walls that should give you nearly R30. They installed the foam right over the exterior sheathing with the foam nails and washers then house wrapped in the Tyvek. This is in Connecticut and was a code requirement due to the HVAC system they used (no air-to-air heat exchanger).

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    • #3
      Re: 2" rigid insulation on older house

      Originally posted by buffer View Post
      i live in Canada where the temperature can be -40 to +40 celcius.i am going to replace the windows & doors and was thinking about putting 2" rigid insulation on the outside.couple of ?.is the insulation going to allow the house to breathe properly and do i need building paper on the outside or underneath the rigid.any answers or opinions would be appreciated
      the house will breathe properly with the foam.i would use building wrap also.the foam may be tight but not so tight that it would cause a problem.my plumber built his home last year the same way.he is on a slab with radiant heat.works like a charm

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      • #4
        Re: 2" rigid insulation on older house

        when using the foam do you put the wrap on before or after the foam

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        • #5
          Re: 2" rigid insulation on older house

          if the foam you are using is dow super tuf r, or a similar polisosianurate insulation, proceed with care on exterior installations. when i asked dow chemical about using it as interior insulation between stud walls that were framed on the flat to save space in a basement laundry room, they advised that it does not like wet environments.
          there's a solution to every problem.....you just have to be willing to find it.

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          • #6
            Re: 2" rigid insulation on older house

            Originally posted by buffer View Post
            when using the foam do you put the wrap on before or after the foam
            The wrap goes on over the foam and before the siding.

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            • #7
              Re: 2" rigid insulation on older house

              Originally posted by buffer View Post
              i live in Canada where the temperature can be -40 to +40 celcius.i am going to replace the windows & doors and was thinking about putting 2" rigid insulation on the outside.couple of ?.is the insulation going to allow the house to breathe properly and do i need building paper on the outside or underneath the rigid.any answers or opinions would be appreciated
              I did exactly what you are considering. After careful research, I added 2" of extruded polystyrene and wrapped it with Typar before siding. This also eliminated the squeeking that some people say they get between the siding and the polystyrene. I also did NOT tape the seams on the polystyrene upon advice bu the siding contractor. This is so the house will breathe. They actually said that if i tape the seams, they will cut the tape.

              Now to some good news - firstly this is NOT spam - call CanSpec before you do anything. You can "Google" them. You can calculate the grants on-line. They will assess your home before and after and you will qualify for government grants. I live in Ontario and by adding +R9 and air sealing, I qualified for $3400.00 in Federal and $3400.00 in Provincial grants. (I got another $400.00 for upgrading my attic insulation as well). The insulation, Typar, and attic insulation cost me less than $2000.00.

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              • #8
                Re: 2" rigid insulation on older house

                This is off of DuPont's web site:

                Taping the seams with DuPont™ Tyvek® Tape gives you the best Tyvek®-to-Tyvek® adhesion, optimal protection against air and bulk water penetration, and extra durability protection during the building’s construction phase.

                Tyvek is not a vapor barrier, it is more like Gor-tex in that it will let moisture escape but will not let air infiltrate, thus, taping the seams will complete the seal.

                I'm not familiar with this Typar that Hacksaw123 was discussing but I wouldn't let any sider cut the tape on my house, especially at $12.00 a roll and the labor that goes into applying it.

                Dupont also says:
                With more energy efficient construction, “building tight; ventilating right” is the best practice. Mechanical ventilation is more important with today’s sophisticated energy saving home features. However, blower door testing on homes wrapped with DuPont™ Tyvek® show natural air exchange rates per hour that are well within acceptable guidelines per ASHRAE Standard 62.

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                • #9
                  Re: 2" rigid insulation on older house

                  Typar is just another generic type of house wrap and is basically the same as Tyvek. In my case, the Typar was taped. It was the seams (joints) in the extruded polystyrene that were not. It is feared that if you completely seal the joints in the extruded polystyrene, you in effect have created another vapour barrier. As you know, a vapour barrier must be on the warm side of the insulation so it does not sweat. A rule in an R2000 home is the 1/3 2/3 rule. No more than 1/3 of the insulation can be on the warm side of the vapour barrier. Most sources I checked confirm this except for Dow Corning. I did come across their site and that is what caused me to look into it further. There is not 100% agreement on this but the majority of the sites I found say "do not tape the seams in the polystyrene". This may not be as critical in a constantly warm climate.
                  Last edited by Hacksaw123; 02-04-2009, 08:58 PM.

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                  • #10
                    Re: 2" rigid insulation on older house

                    thanks for all the replies.i would tend to go with Hacksaw123 and not to tape the seams on the foam and i would only tape the verticle seams on the typar.you would want the bottom and top open to let any moisture out

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                    • #11
                      Re: 2" rigid insulation on older house

                      Sorry for not making this clear. I wouldn't tape the seams on the insulation (the foam) but I would tape the seams on the house wrap (Tyvek/Typar). Moisture is designed to pass through the house wrap and you tape the seams to prohibit air infiltration.

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                      • #12
                        Re: 2" rigid insulation on older house

                        I had a R2000 certified home built 2 years ago by a reputable builder in Ontario. He used 1 1/2 inch code board plus R 19 fiberglass in 2x6 stud walls (then covered with stone or brick). Taped all seams, not at top or bottom. Vapor barrier on inside of wall under drywall. Tyvek only used on garage portion (covered with stone and wood siding).

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                        • #13
                          Re: 2" rigid insulation on older house

                          i helped a guy put 2" styro on a house a couple of years ago and the achitecs specs were if you taped the joints on styrofoam you didnt need tyvek.

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                          • #14
                            Re: 2" rigid insulation on older house

                            Originally posted by buffer View Post
                            i helped a guy put 2" styro on a house a couple of years ago and the achitecs specs were if you taped the joints on styrofoam you didnt need tyvek.
                            Hmmm.... After all that, it looks like you're right back where you started

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                            • #15
                              Re: 2" rigid insulation on older house

                              Originally posted by buffer View Post
                              i helped a guy put 2" styro on a house a couple of years ago and the achitecs specs were if you taped the joints on styrofoam you didnt need tyvek.
                              I think a lot of it depends on climate. In areas that don't see freezing weather and insulation is more for air conditioning, it may not matter as much.

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