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Community and Q&A

Skylights and cold (cold!)…in San Diego

aztecrsf | Posted in Energy Efficiency and Durability on

The TLDR version… we have two skylights that appear to be a major source of cold in our family room with a vaulted ceiling. They are dual pane and don’t leak. They’re also large, 5-6 x 2-6. I’m wondering if an acrylic insert, like a storm window, that is air tight and creates a 1″ space, would make much difference when it’s already dual pane. Same for double-cell blinds. They’re expensive to just experiment with, and it would require scaffolding to install, so I’m looking for feedback. 

Additional details… Thankfully our house is not in Wisconsin, because the building is already very cold in San Diego (don’t laugh, Midwesterners!). Thanks to the tattletale FLIR camera, we’ve targeted and tackled many obvious issues in the attic, like gaping holes into bath soffits, walls totally open above, sealing around a chimney, adding insulation, sealing every top plate hole, etc. A total of 13 days in the attic and the improvement is minimal. 

That could partly be because of the skylights. But as a bonus, that room’s ceiling likely has either no or minimal insulation. It’s hard to tell, but based on the thickness measured inside and outside, it looks like just tile roof, asphalt shingle below that, over T&G. We also have single pane windows and a French door. The total area of glass is about 2.5x that of the skylights. At least the windows and door are tight. We can’t put storm windows on them, but we might have dual pane sashes made (they are $2k each, so they are the last thing we want to do, although we have 4 on order for another room). Why so expensive? The windows are high end wood, expensive to remake custom, and the walls are stucco (not painted).

Thanks for any insight.  

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  1. Expert Member
    BILL WICHERS | | #1

    You may be loosing a lot of heat through the sides of the skylights wells too as this is a difficult area to effectively insulate.

    You would probably have some energy savings with a “storm window” as you describe, but you might not actually get a noticeable amount of improvement. The storm window on the inside is going to increase the risk of condensation as well.


  2. aztecrsf | | #2

    Zephyr, the skylights are on low curbs, no wells/shafts. We do have other skylights in other rooms with those shafts, which indeed have been a pain to insulate correctly. They had R30 batts just stapled over them, giving an effect R value of zero, plus or minus. Foam is the solution there. Thankfully, those rooms are not the meat locker that the family room is.

  3. Expert Member
    Akos | | #3

    Don't know how old those skylights are but basic dual pane is around R2. This is only just slightly worse than your un-insulated roof (~R3). If you look at the surface area of the two, even if you double the R value of the window, it would make little difference to the overall heat loss.

    There is no easy answer here, if you want warmer ceiling, you need to get some insulation there. Maybe next time the roof needs to be re-done, adding even 1.5" of rigid insulation over the roof deck would make a HUGE difference in heat loss.

  4. aztecrsf | | #4

    Akos, there wouldn't be any clean way to add insulation outside, as the clay tiles would then be uneven with the other sections of the roof, and I'm not sure what we'd do at the overhangs with the added thickness. However, we could add foam to the ceiling and cover with drywall, but that would be a real bear. I'll take my infrared thermo and read the skylight vs ceiling temp tonight after the furnace has been off for awhile. That should help show whether the skylights are that much colder than the ceiling.

  5. Expert Member
    Akos | | #5

    If your windows are clear glass, they would be colder especially on a clear night because of radiation losses. In that case a set of shades would definitely help, you won't get that feeling that the windows are sucking the heat away from your body.

  6. aztecrsf | | #6

    That describes it perfectly. The temp is fine, 68-71F and yet we need heavy sweatshirts/blankets to sit in there the moment the heater shuts off.

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