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insulating 1970 deck house style roof-exterior vs. interior approach-costs

1970deckhouse | Posted in General Questions on

First, apologizes in advance as it is a steep learning curve to absorb  roofing concepts and I am starting at zero.  I found this earlier thread (below) which is helpful in beginning to  educate me on what is needed and what to watch out for when contractors are talking to me. I also found diagrams on the Acorn Deck house site (below).Thoughts appreciated on realistic price points to expect and exterior vs interior insulation pros/cons for efficiency and costs. 

The old family home, a 1970s deck style exposed beams, 1200 square foot footprint, has no insulation in the roof.  The roofing deck has layered  roofing paper and shingles and the roofing deck underside is what you see from the inside. (I grew up in the house and we knew no better when it was built.)  The house is in the mid-Atlantic (can be below freezing  winters and hot summers).  So far I have gotten estimates-60-90k from experienced companies to insulate from the outside with new roof etc., which makes tearing the house down and starting over not unrealistic.  However, I can deal with most of the rehab inside myself but this roofing problem is not a DIY. If I can fix the  roof I can deal with everything else a little at a time.   These estimates  seem high to me but I have no experience. 

If the estimates are accurate, is insulating inside a better way to go cost/efficiency -wise-If so, I am not sure aesthetics alone  justify the price to go with exterior insulation.

 You can see the melted snow /frost line on the roof which is painful to see and to keep warm for a senior was 4k a year.  
Thank you in advance.

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  1. gusfhb | | #1

    So, I live in one and have done a bunch of DIY insulation etc.

    The roof is actually pretty easy.
    The real issue is how much you want to look at visually.
    The original house had a 6 inch facia board, covering 2-1/4 inches or so of decking plus insulation.
    My house had a whopping one inch of foam.

    Everything you do will be a massive improvement.

    IF you have the extended living room with the associated shallow pitch roof, go with rubber[as I did]

    Rumor is after a heavy rain the Deck House guys hated going into work. They all leaked.
    Mine doesn't and I suggest you focus on water first, insulation second.

    If you are fussy about the roof edge look, do a lot of research into various treatments. I ended up with a 8+ inch facia which preserves the 'look' and greatly improved the energy performance.

    Really, glass is the issue.

    I have 750 square feet of glass in a 2800 square foot house. There is no energy answer that does not speak to the glass. Start doing the math. you can have a foot of foam on the roof, but if you do not address the glass, you will not really get far

    1. begreener | | #3

      The best way I have been able to deal with the fixed (double pane R2) window glass (sits in a 2X4 mahogany window buck) in my mid-1970s Deckhouse is by placing a battery operated, room darkening, double cellular shade between an Indow plexiglass (interior storm).

      You don't need the tracks because the glass window is "fixed" (air tight)

      Glass R2
      Cellular shade R4
      Indow R2

      Total R8?

      The best way I have found to deal with the metal crank-out windows is to use a magnetic interior storm window

  2. 1970deckhouse | | #2

    Thanks, interesting and accurate point about the windows/glass. All original windows, never replaced, but at least all standard size windows and sliders. I have been thinking I needed to start with the roof insulation problem, but obviously there is more than one insulation/heat loss issue going on here--the melted roof line is just the most in your face one! And I have always thought the walls may be suspect as to the among of insulation used. Thanks again.

    1. begreener | | #4

      My deep energy retrofit for wall insulation (all DIY) for my mid-1970's deckhouse (has a walkout basement/split entry) is to:

      1. Remove all siding/sheathing above grade & R11 FG batt
      2. Attach 1.5" urethane nailbase (R9) for thermal break
      3. Inject 2-part, slow-rise, urethane foam in 3.5" cavity (R21)

      Below grade

      1. Remove all sheetrock & R11 FG batt
      2. Attach 1.5" Wallmate EPS (R7.5) - strapped horizontally
      3. Inject 2-part, slow-rise, urethane foam in 3.5" cavity (R21)

  3. gusfhb | | #5

    I think there might be some pushback on the foam sandwich
    I would like to see some pics of how you handled the exterior window jamb details
    For those unfamiliar, the window jambs have no exterior or interior trim, so those details can be, errr, problematic

  4. Expert Member
    Akos | | #6

    Roofers that are used to doing shingles usually have no/minimal experience in dealing with exterior rigid insulation. The price seems to say, they don't want to do it.

    My recommendation would be to talk to a roofer that does flat roofs (torch down or single ply) as these folks are familiar with rigid. The one thing to watch is they use the correct length screws so the screws don't poke through the ceiling.

    None of this is worth while doing unless you need to replace the existing roof.

    The one DIY thing you can do is air seal the edges of the T&G. The T&G might look like tight but all those gaps between the boards add up to a big hole to the exterior and a good part of your ice melt issues. You can carefully drill from the inside so you don't poke through the roof between the boards and inject foam to seal them up.

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