I WFH and my normal office is a lovely big converted double garage with TV, sofa’s and Sonos – unfortunately it’s too big to heat (electric only) for just me so I’ve moved into the ‘computer room’ in the house which is pretty small but kinda nice.

The problem is that it’s actually the coldest room in the house and I will still be heating it electrically as I’m the only one at home!

It’s at the end of a single storey extension and has windows on the two external walls with old style double glazing which certainly isn’t as good as it could be.

I’m wondering whether its worth adding something to at least one window to create some secondary glazing. If so, what works and what doesn’t?
Does it have to be sealed to the window frame?

depends on the rest of the room/walls, and/or how big the windows are but IMO it’s unlikely to make much difference unless your windows are as big as your walls. Are the wals insulated?

Heavy curtains? There’s a noticeable temperature drop in our bedroom when we open the curtains of a morning.

do you mean physically to the window frame itself? Ones I have seen are attached to the window reveal and you will need to have a good seal to that to stop air movement getting through the secondary glazing ideally, this helps to stop draughts and limit moist air getting trapped between the window and secondary glazing. You’ll potentially get loads of condensation in there otherwise due to the internal window surface being much cooler due to the secondary glazing keeping the heat inside the room.

Is the single storey extension roof reasonably insulated?
As others have said, are the external walls insulated?

glass itself isnt a great insulator its the vacuum in a double glazing unit that does the insulating so really ‘secondary glazing’ is really a draft excluder for something like single glazed sash windows.

Curtains would work better but at this time of year its a bit off a play off between keeping heat in and benefitting from any solar gain during the daytime.

Ahh, OK, thanks guys.

It’s probably not worth it even though one window is almost the entire wall (short side of an L) – it’s not something I’d want in place all the time.

Block walls with a cavity that was filled years ago but is possibly not that good.

The bigger issue TBH is the boxe in soil stack that comes from my en suite into the rood space above the office – the boxing is just 4mm ply and there’s a big hole at the top where it opens into the roof space. I’ll be filling that gap with expanding foam I think.

You could look into replacing the sealed glass units, cheaper than replacing the windows.

If you can seal up and insulate everything you see with regards to gaps it will greatly help retaining the heat for longer. Once you’ve exhausted that avenue, then if you still have issues look at curtains etc for windows.

The gap inside a double glazed unit isn’t a vacuum, it’s normal dry air but sealed. Air is a good insulator as long as it can’t move and convect the heat. Secondary glazing creates a similar static body of air but not as well as a double glazed unit. If you have trickle vent (a mandatory requirement which is nuts as they make modern windows pass all sorts of thermal tests then make you drill a slot through them) or leaky seals on the openning windows the secondary glazing won’t be that efficient.

Checking roof insulation and sorting the soil pipe would be my first tasks.

The gap inside a double glazed unit isn’t a vacuum, it’s normal dry air but sealed.

Anything faintly modern has argon or krypton in there and its been that way for at least 10 years.

Anything faintly modern has argon or krypton in there and its been that way for at least 10 years.

If your work involves anything shady I suggest getting some krypton ones, great for preventing Superman from bursting through the glass and beating you up.

Checking roof insulation and sorting the soil pipe would be my first tasks.

+1

I also found that inserting a layer of reflective, wind proof membrane under carpet underlay or laminate floor underlay also helped when coupled with sealing drafts under skirting. Can you insulate the floor like this, or indeed get in there and properly insulate?

After that, a lining of insulated plasterboard is the next step to improve things. BUt that means remounting all electrical fittings, door casings, window cills and skirting. Plus a skim…