Closing a skylight with gypsum board

Question

We have a fixed skylight in the point of the house where we have stairs and this continues to an office that we have. Therefore the office is in an open space with the stairs and the skylight. This is around 6 meters x 70 cm and is fixed. We have never had leaking issues because the window is fixed.

We have had the house for 8 years, and every winter we have the issue that on really cold nights, condensation forms on the skylight and all night we hear drops of water from the skylight. This is probably because we unfortunately made the error of putting single glazing, and not double glazing, on the skylight.

I applied a window a film and also sprayed it outside with a matte transparent paint but this just reduced the August sun, and there is no change in the winter.

Also the other problem that we have is that sitting in the office feels very cold in winter, because of all this open space. I assume that if the glass is so cold it could also make a difference in temperature, correct? Or is the cold feeling because of the double ceiling height?

Therefore, we are thinking of closing the skylight with gypsum board. We want to stop the condensation issue in winter, and also possibly stop this really cold temperature that we think is caused by the cold glass.

Would you say that is OK to close this with gypsum board, or will the condensation continue and lead to mold over time? Would it help to put insulation between the glass and gypsum board?

Attached are photos from the roof, as an FYI guys. This is a custom made window. The roof at that point is sloping, and the brown color was just a paint i did thinking that would make some difference...

Answer 1

If you simply cover the bottom of the opening with drywall/plasterboard/gypsum board, you'll still have condensation on the skylight, though possibly a little less because the drywall will slightly insulate the window opening. The difference is that instead of dripping onto the office floor/down the stairs, it'll get collected on top of the drywall. Instead of irritating you each night, now you won't notice until the drywall gets so soggy that it collapses onto your desk chair.

Insulating the cavity between the drywall and glass will help, but it's very much a short-cut way of doing things. It will likely have a negative impact on resale opportunity/value when it comes time for you to move on. People will look a the lovely skylight when they're looking at the outside of the house and wonder where it went when they're looking at the inside. They may wonder what other short-cuts/shoddy workmanship was done and it could scare them off from making a purchase.

If you really don't want the skylight any more, the proper thing to do is have it removed and have the roof patched in with plywood & shingled over to match the rest of the roof (or sealed and graveled, now that we have a pic of the actual roof in question), then insulate the cavity in the rafters, then drywall and finish the interior ceiling.

If you like the light but want better insulation, replace the skylight with one with double- or even triple-pane glazing, possibly Argon filled (for better insulation) and low-e coatings to help keep the UV out and the heat in.

A replacement skylight (whether just the glazing or a whole new unit) won't be cheap, but will probably be on par with filling in the hole with solid roofing material. Either will be less expensive than a hospital visit if you happen to be sitting in the office chair when the drywall gives way because of the condensation that's collected on it.

---

You mention that you stuck a window film "on it". I'm not certain if this was a coating directly on the glass, or if it was a "window insulation" kit that went on the window frame.

• If it was something directly on the window, that probably wasn't going to have had much of a chance to provide any additional insulation. Put a thin piece of plastic (like plastic food wrap) on your hand and hold it over the stove - you'll notice the same heat hitting your hand as without the plastic there. Please do this carefully - you don't want plastic melting to your hand!

• If you use a window insulation kit, with double-sided tape on the skylight frame, then thin plastic that sticks to the tape and is heat-shrunk to stretch tight, odds are good that this will provide a noticeable improvement in insulation. It won't be nearly as good as double-pane glazing would be, but you might find that it's sufficient to stop the condensation.

  • This may be sufficient to put off replacing the glazing for a year or two until you've got some cash saved up to do it and prices have come back down from the stratosphere.

Answer 2

TL;DR

Replace the skylight with double-pane or triple-pane glass. Argon gas is typically used in between the panes and the condensation issue should stop.

Add a ceiling fan and run it in reverse (blow air at the ceiling) on low during the winter to make the room warmer.

---

We never had leaking issues because the window is fixed.

It's never too late to experience a leak.

---

every winter we have the issue that at really cold nights, water is formed on the skylight and we head all night drops of water from the Skylight.

Condensation, yes.

---

we did unfortunately the error of puting 1 glass, and not double glaze on the skylight.

I wasn't aware that single-pane windows were still an option. Is this some sort of "homeowner special"?

---

I sticked on window a film and also sprayed it outside with a matte transparent paint. But this just reduced the August sun, and there is no change in the winter.

Right, air isn't a good insulator. The only advantage of the film is to stop drafts.

---

Also the other problem that we have, is that sitting in the office feels very cold in winter, because of all this open space.

Warm air rises and is easily escaping out of the single-pane window.

If you have a ceiling fan then run it in reverse to recirculate the warm air trapped along your ceiling.

---

I assume that if the glass is so cold it should make also a difference is tempereture correct? Or the cold feeling is because of the double ceiling height?

The single pane is letting heat escape and the double ceiling height means that it's tougher to keep that room warm.

---

Therefore, we are thinking of closing skylight with gypsum board. We want to stop all this condensation issue in winter, and also possibly stop this really cold tempereture that we thing that is caused by the cold glass.

Would you say that is OK to close this with gypsum board , or it will create mold over time? Maybe put between glass and gypsum board glass-wool/fiber.

Oh dear, gypsum is not a vapor barrier so the glass would still condense but now you've hidden the problem so good luck with the mold and eventual rot.