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cold climate roof insulation

dancitect | Posted in Energy, Heating & Insulation on May 1, 2005 07:37am

Hi

I have an old house (1929) in Upstate NY on the border of Vermont and Quebec.  I am going to put on a new roof and am planning to use recycled rubber roofing tiles that look like slate.  I want to solve an insulation problem while I am at it.

Part of the roof has living space directly below it (aprox 6 feet up the roof) where I want to put a couple of skylights (but that is a whole different issue).  The roof currently creates icicles so I am assuming it needs better insulation.

I am wondering if there is a way to insulate this without ripping off the roof deck or the plaster of the interior. 

Right now the attic is vented with gable vents and has blown in fiberglass insulation onthe floor (the ceiling of the living spaces below).

It was suggested to me that it might be possible to build a secondary roof deck over the existing deck with rigid foam insulation and an air space that would run from soffit to ridge.  This would also solve the problem of the roofing that I want to use suggests a plywood base.

Any ideas????

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Replies

  1. Piffin | May 01, 2005 08:08pm | #1

    If you have voids in the inner insulation, after stripping the shingles you have, drill holes in the roof deck and blow in dens pack celluloase or chpped fibreglass.. Dry in the exposed sheathing with 30# taarpaper, then apply 2" XPS foam insulation board. Run across it with 2x4 for strapping to make it a cold roof, I use GRK screws to secure through the 2x4, the foam, the sheathing and into the rafters. Eaasy to get 5 or 6" screws that will run right in.

    Then you sheath with new plywood, and RooftopgaurdII for underlayment paper, and shingle away.

    but if you have not yet purchased those rubber imitation slates yet, take a look at what some of them can do in only a few years...

     

     

    Welcome to the
    Taunton University of
    Knowledge FHB Campus at Breaktime.
     where ...
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    1. rez | May 01, 2005 10:25pm | #2

      You know, that could be a positive selling point in that the shingles can now compliment the wavy and bubbling vinyl siding with the popular 'random' look.

      sobriety is the root cause of dementia.

    2. dancitect | May 02, 2005 06:28am | #6

      Thanks... that is similar to what I was told.... makes sense to me

      Would you use a ridge vent at the top; but only to cool the exterior deck? 

      I am assuming you wouldn't recommend the slates then... looks like they are buckling... any particular reason why?   What about the manufacturers... don't they give a 50 year warranty?

       

      1. Piffin | May 02, 2005 06:47am | #8

        A warranty is only as good aas the company and product it stands behind. A piece of paper won't keep water out of your house. one of the early manufacturers of thesse is now out of business, according to hearsay. One of the photos is of Eternit brand. Notice the implication in the mname of eternity? Hah!Problem is that rubber is recycled and the hot sun cooks off volatile oils in petro products. That is why composition shingles are coated with ceramic chips, to keep the UV from drying the asphalt and cooking off the volat5ile oils that keep it waterproof and supple. These products with recycled rubber already are short on oils - notthat I know a tinkers dam about the chemistry, but IMO, when the product already has forty thousand miles on it bnefore getting turned into roof tiles, it is reasonable to expect dryrtot to show up early. When these products fiorst hit the markeet and somebody sent me a sample of one, i replied asking them what the wind resistance and real life liongevity was. I never got a simple polite reply, and have been hesitant to use them, until i see one that lasts. There are three such roofs I know of here, from at least two manufacturers, and all three have had problems. maybe you have aliner on a goood one. The idea is a nice ont to use up watse produict, but i have to see the proof first - for that kind of money, not to mention my reputation 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. dancitect | May 02, 2005 01:56pm | #9

          Thanks for your insight...

        2. User avater
          constantin | May 02, 2005 07:40pm | #11

          Allow me to quibble...The Duraslate product is being made by the largest PVC manufacturer in North America with billions in revenue. These imitation slate tiles are either virgin PVC or made from recycled PVC, I cannot recall which. Either way, I expect them to be around a lot longer than a rubber-based product for the reasons you have so eloquently stated.As with all construction materials, it pays to delve a bit deeper into where they came from, how they were tested, and how the conditions compare to the environment they'll face at the job site. If I had not been 100% confident that the Duraslate was the right product for my environment, I would not have used it.Lest we forget, even authentic slate has its flaws that can and will lead to leaks over time.

          1. rez | May 02, 2005 08:09pm | #12

            Constantin- Welcome to Breaktime.

            I see you placed a pic in your profile but no data.

            How about giving us an idea who you are and what part of the country you're from.

            sobriety is the root cause of dementia.

          2. Piffin | May 02, 2005 08:50pm | #13

            No need to quibble. That is a positive recommendation. Like i said, the idea is a good one but it is up to the mqanufacturers to convinvce me that they make a product worthy of attention. This is a good step and the name should be sticking in my head now. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          3. dancitect | May 03, 2005 12:05am | #14

            What environment did you use them in....

          4. User avater
            constantin | May 03, 2005 09:01am | #15

            ... hi, everyone, I've posted here for a while. Piffin may remember me from earlier discussions re: fake slate and non-vented roofs. Anyway, the house is in the Boston area, i.e. a climate in which heating predominates almost 8-1.

  2. cliffy | May 02, 2005 12:00am | #3

    If you are in an area with snow forget the skylights.  It doesn't matter what flashing kit Velux has or how meticulous you are installing them,  installing skylights in a snowy area is like driving a motorbike, sooner or later you are going down.

    Have a good day

    Cliffy

    1. gdavis62 | May 02, 2005 03:46am | #4

      I used to travel to Midland on biz, even in the winter.  I was impressed at how many people got to work via snowmobile, and what a cottage industry there was there, shoveling excess snow off rooftops in the winter.

      What's your average winter snowfall?  I wish we had yours here!  I am in ski country, upstate NY.  We get real cold, but we don't get the consistent snowfall you have.

      BTW, we have Velux skylights, and we're doing OK.

      1. cliffy | May 05, 2005 05:02am | #18

        Hello Lake Placid.

        I've had the pleasure of three road trips to your town.  What a great place.  We did 3 days on Whiteface each time and checked out all the sights and facilities on a day off.  Good times.   About a 9 or so hour drive for us.

        I live in a little town beside a little ski hill.   We get dumped maybe 6 to 10 feet ach winter.   I don't shovel the snow off my roof but some people do in these parts. However I think I'm the only person in our town without a ski do. 

        What kind of biz would bring you to Midland?

        I have installed my last sky light (unless I relocate in the future)

        Have a greaat day

        Cliffy

        1. gdavis62 | May 05, 2005 01:53pm | #19

          I was in the door business, and all the molds for our fiberglass skins were made by Weber Tool, in Midland.

          1. cliffy | May 06, 2005 02:34am | #23

            Oh.  The only thing I've checked out in Midland was the huge church( Ste. Marie amoung the Hurons I think) and the Indian Village.  My parents got up at about 3 in the morning about 20 years ago to drive down there to see John Paul the Second.   Is Shania's Lake Placid home near you? 

            Have a good day.

            Cliffy

          2. gdavis62 | May 06, 2005 01:05pm | #24

            Ms Twain sold her place and moved. 

    2. Piffin | May 02, 2005 04:30am | #5

      Properly installed skylights don't leak. I've done literally thousands.In a cold climate they will have condensation issues though. 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      1. dancitect | May 02, 2005 06:33am | #7

        Can you suggest the best skylight for a cold climate? It gets to -20F in the winter here but doesn't usually get killed with snow... although the last two winters were pretty wet.

        One of the skylights would be in a bedroom the other in a bathroom.  Both are on the east side of the house.  Any special way you would install them with the new roof deck mentioned above?

         

        1. WorkshopJon | May 02, 2005 04:30pm | #10

          Can you suggest the best skylight for a cold climate?"

          Dan,

          No one best brand IMO, but differing methods of flashing.  Cheap ones are "curb" flashed.  I've always had good luck with the step flashed which are more expensive.

          WSJ

        2. Piffin | May 06, 2005 02:24pm | #25

          Earlier, i was responding about the shingles, but on review, see you were asking more about the skylihts. The best way to go is with Velux. i wrap from sheathing to side of frame with vycor or bituthene ifrst, then do the step falshing kit they provide. From inside, I use spray faom around eges and cavities to help prevent the clash of hot and cold that leads to condensation. Trim to it should be caulked tight.UI have also had one where I did something I have heard others do - there was a skylight in a kitchen, right over the sink, loacted just right so that condensation driopped off a single spot and hit the lady on her head - very aggravating. So I built a mini gutter that would collect the moisture drip and re-evaporate it again. between that and a shutter/bind set to close it off at night, we eliminated the complaint. 

           

          Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      2. cliffy | May 05, 2005 04:53am | #17

        If you lived here you may reconsider!

        Have a good day

        Cliffy

        1. Piffin | May 06, 2005 02:27pm | #26

          I don't know where "here" is, but it would be hard tyo find a climate harder on skylights and roofs than the high country of Colorado 

           

          Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

    3. RobWes | May 05, 2005 10:48pm | #21

      I've been gone for a few days.

      I will never in this region put a skylight in any home I will live in. We take the time to place 40/50 year rated shingles on our roof then we go ahead and poke a bunch of holes in it. I've never seen one that didn't leak. I start my house this month more North than the NY Canada border. No holes in my roof.

      1. cliffy | May 06, 2005 02:30am | #22

        Right on.  I don't plan on putting any more skylights in anyone elses home either.  If they want one that bad they can hire somebody else.  

        Have a great day

        Cliffy

  3. MrEnergy | May 03, 2005 07:05pm | #16

    If you insulate the deck and it is over an already ventilated attic space, you are wasting your time ... except that it will likely eliminate your icicle or ice daming (damning?) problem (by decreaseing the temperature of the roof surface). You would need to elimnate the current gable/soffit (eave) venting to also affect the energy aspect of the house.

    Icicles can form not from a lack of insulation, but ALSO from lots of air leakage into the attic allowing warm air to warm the roof surface up enough to melt snow and allow the freeze/thaw to occur and build ice dams. I've seen many well insulated roofs w/ 12-15 inches of ice build up ... due to penetrations of the attic/roof structure. A major culprit is the ever popular recessed light fixtures.

    One inspection I did on a new well insulated home w/ major ice dams ... I poked my head into the attic ... no problem seeing as the insulation was held back from the many recessed light fixtures and the many misc holes in the fixtures illuminated the attic well enough to see everything in the attic!! The heat from the lamps exacerbated the chimney effect and air flow from the moist space into the attic.

    1. dancitect | May 05, 2005 05:25pm | #20

      If you eliminated the current gable vents... there are no soffit vents; would you then insulate the rafters in the attic or just leave it with insulation on the floor?

      Also I am assuming I would vent the new roof deck from soffit to ridge???

      Thanks for all your help....

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