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Community and Q&A

Metal patio door frame

MNzS7buQPf | Posted in Energy Efficiency and Durability on

This is a very small question… I face the need to deal with 2 broken seal glass segments (basically, all of the glass) of the patio door. These can be replaced with 2 low-e coated glass for about ~$600. But then, would continuing with the metal patio frame be a big liability? A year ago I replaced the outdoor framing around the patio door and in the process we added some foam sealant around the metal frame. It has improved things; there is less infiltration, but some sections of this metal frame still had a bit of “frost” forming on them on the inside in the very cold of winter. Does it mean that I still have some air pockets next to the frame that allow the cold to permeate to the house or is it a feature of the metal door itself? (Well, metal is conductive, who the hell came up with the idea of making metal frame doors?). Replacing the whole door with standard compatible to my other upgrades would cost about $2,500, so it is a bit steep).
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  1. Riversong | | #1

    You are right on all counts. Metal door frames are a bad idea that's gotten worse with our increasing concern about energy efficiency and interior comfort and durability.

    You would be better off with a less expensive patio slider with an insulated frame than by putting good glass in a highly conductive frame that may be showing signs of corrosion as well. But if you can afford a good quality door, you won't regret the decision, since it will probably function better and longer. Make sure that the glass units come with a 20 year warranty.

  2. MNzS7buQPf | | #2

    Robert, thanks for answering!
    If we were to guesstimate the portion of heat loss due to metal frame relative to glass with broken seal and relative to glass with good seal/low-e what would be these proportions? If I could reasonably imagine that the frame is responsible for say 10-15% of the heat loss of the whole door (w/repaired glass) I would still stay with it. I'm thinking of those thermal images people take of the heat loss - there is probably some indication where most of the loss is, for various configurations, so seeking some input from those who do a lot of these :)

  3. Riversong | | #3

    The broken seal does not effect the insulating value of the glazing unit, except perhaps trivially if it had an inert gas fill which was replaced by air or if it had a lowE coating which now has condensation on it - it only effects the transparency and visible light and solar gain.

    This is a very rough approximation, but if each 36" x 80" glazing panel is surrounded by 1" of aluminum frame, the conductivity of the frame would so overwhelm that of the glass that changing an R-2 panel to an R-3 panel will make almost no difference - in either case the whole door R-value would be something on the order of 0.03.

    A metal-framed patio door might be OK in southern California, but not anywhere with cold temperatures.

  4. HDGFHkB5cP | | #4

    For whatever it's worth, if you replaced the entire door with a qualifying unit before 12/31/10, ~1/3 the cost of the unit could be used for a tax credit. Not sure about just replacing the glass.

  5. Interested Onlooker | | #5

    When I just clicked the overall Q&A button my Sophos malkware package warned me of a Trojan, namely


    I received the same warning when I clicked on the 'contact' button. It looks like you might have a security breach.

  6. J Chesnut | | #6

    How much you should spend on this depends on where you are located. The colder the climate you live in the higher the recommendation to deal with this properly.
    If you do decide to replace the whole unit I would consider going to a exterior rated swing door with a fixed side lite. Sliding operation doors and windows (like double hungs) typically allow more air infiltration because it is difficult to get a tight seal around things that need to be allowed to move past each other.
    Quality window units come with a NFRC rating that includes a rating for air leakage. I haven't dealt with domestically made exterior rated doors recently. Does anybody know if exterior doors come with a air leakage rating?

  7. MNzS7buQPf | | #7

    Thank your for further explanations and recommendations! I live near Chicago, pretty cold in winter!

  8. Riversong | | #8

    NFRC tests both doors and windows for air leakage per ASTM E 283.

    Both air leakage and condensation resistance, however, are optional on the product label.

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