How can I insulate skylights?

My house has been extended and the extension has double glazed windows for roof, think of it as a very sturdy conservatory. I understand why the previous owners did it - to get more space and light, but in terms of heating they have created a disaster.

I could see the issue immediately, but didn't think it would be that bad as the glazing looked to be very modern.

Reinstating the previous garden door inside would not be ideal, so I am now looking for ways to sacrifice light for better insulation.

There is plenty of headroom, so if it was possible to bond insulation to the inside and box it in, that might be a solution.

Is something like that feasible or are there better methods? Thank you.

EDIT - added picture for clarification:

enter image description here

The problematic part is the window panes above the door and normal windows, they form a kind of elongated pyramid shape with a rectangular base area.


4 Answers 4


You could consider putting in french doors between the rooms. This would help with keeping more of the heat in where you want it and still allow light to enter.

  • That would definitely work in terms of heating, this is what people normally do here. However because of the way it is arranged originally and rearranged later, I would then end up with 2 very small rooms.
    – nsandersen
    Commented Jan 23, 2019 at 15:39
  • Hmm. I've seen what looks like a pocket doors with multiple panels. Not sure of the correct name nor the expense for them either. Similar to sliding panel doors you see for some patios. Or a curtain. Will help with retaining the heat yet still be easily moved. Commented Jan 23, 2019 at 15:58

You could make a wood or aluminum frame that fits inside of each window pane, then put Styrofoam insulation board in that frame and devise a way to "clip" the frame into place during the winter, allowing it to be easily removed in warmer months. Do it just like it was a window screen, you can use that type of rotating clip.

enter image description here


The problem with covering glass skylights up with insulation is that it will create condensation on the interior of the glass.

Because it sounds like such a “disaster” (as you call it,) I suspect your skylights are single pane glass.

If your skylight is a flat window looking skylight (and not the bubble on the roof type), I’d suggest converting to double pane or even triple pane glass. There is a conversion kit that fits into the slot where the single pane glass is now, but the perimeter still allows a lot of heat transfer through the frame, glazing stops, etc.

They also make solar glazing that allows the sunlight in, but keeps the heat from escaping.

If your skylight is the bubble type that sits on top of the roof, you can replace it with one that has double glazing and an insulated curb.

I’d contact a local window company to see if your skylights can be converted.

  • It is double glazing, but while it looks good and new, many types where I live aren't that good, for instance won't be filled with low-conductivity gas etc. It is the whole roof that is glazed though, so even with triple glazing it might not be ideal. Regarding condensation, yes, it would have to involve impermeable membranes and no space between glass and outside part of insulation or there will be a condensation problem. It is OK to bond it, ie. to make at least half of it a more permanent installation.
    – nsandersen
    Commented Jan 23, 2019 at 8:40
  • If it’s a true conservatory, maybe you could add shades. However, I doubt it would save much energy for the cost of the shades.
    – Lee Sam
    Commented Jan 23, 2019 at 10:41

Rather than cover the skylights, how about creating a “passive solar” installation and use the solar gain to heat the room...especially after the sun goes down. (You can google “passive solar house design” to get an idea of what I’m proposing.)

We’ve built brick walls in solariums that absorb the solar heat during the day and radiates it back out into the room in the evening.

You’d need to build the wall where it can get direct solar gain for most of the day. We’ve built them in the East-West direction and oriented to the South. It could be built along a North wall.

Also, you could pour a concrete topping slab floor to help absorb the solar gain.

I’d contact an architect or solar designer to see if it’s feasible.

  • I like the idea, but it is North-facing with two stories above it - and the Sun doesn't shine so much/go so high in the Winter, so it is in the shade a lot of the time. The goal is to be able to use the space in the Winter too.
    – nsandersen
    Commented Jan 23, 2019 at 10:56

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