How to insulate bay window

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I love in a 1950s house similar to the one pictured below. The lounge and biggest bedroom are both at the front of the house and both have these big bay type windows. We recently had the lounge window replaced as we did some work to the downstairs of the house but the bedroom one is quite old.

The bedroom is absolutely FREEZING and there is a proper draft in there that floats across the bed every night. Last night we had the heating on all night and even so when I went to bed the thermometer in our room said 14 degrees. In the early hours in winter it’s not uncommon for it to drop to below 10 even though our thermostat downstairs has not dropped below 16.

I know the window is a big part of the issue and we plan to get it replaced ASAP. However I also think the construction of the front of the bay is an issue, in part because the lounge is also cold despite having a new window. The wall feels so cold and I don’t think there is any insulation at all, when we decorated and stripped the wallpaper it didn’t seem to be plaster on brick but it just sounded hollow; or maybe wood?

Can anyone advise on the structure of these bay frontages and give ideas on the best way to insulate? I’d rather do something structural even if it costs a bit of money, instead of going down the beach curtains/tinfoil/bubble wrap etc hacks. But also open to those if there’s something life changing that I can do for cheap! Thanks

Phone won’t let me post picture but it’s similar to this one I’ve found
www.onthemarket.com/details/10006187/

Argh typos - live not love. Also big curtains not beach curtains?!

I’m in exactly the same boat as you - bubble wrap has really helped.

Is the bay part of the original structure of the house or have they been added after? Also, look under your windowsill, where it meets the wall. Are there gaps, no matter how thin, there?

You need to put insulation between the tiles on the outside and plaster on the inside. You probably have a timber frame between the two so insulate between the frames.

You can get new plaster boards with insulation on the back but I don't think you can get curved boards so probably won't work for your curved bay.

You should also make sure that you insulate the roof of the bay.

Thanks both. Yes I think it’s timber framed. The bay isn’t actually curved, it’s several different flat sections at various angles so I may be able to use plasterboard. Would it just be a case of whacking some plasterboard on the inside affixing it to the current walls? The walls underneath the window would then come further into the room than they do currently but then we could have a deeper windowsill with the new window.

Also this is going to sound stupid but what kind of tradesman would do this? All the general builders near me are booked up for months I doubt I could even get someone to bother to come out and quote for such a small job. Would a carpenter be able to do it? Or someone who installs windows…?!

Proper Interlined curtains will make a massive difference. My house is really well insulated with huge bay windows. If it wasn’t for interlined curtains the rooms with bays would be cold in a way no other rooms are.

Builder, handyman, maybe plasterer.

If the bay windows are north facing as mine are those rooms are freezing.
The best solution is really heavy curtains. The only reason I haven't done it is because I have asthma.
I got Louvre shutters for the lounge. It helps a bit.

That sounds perishing.
You can get plasterboard with insulation on the back and do the whole wall and into the bay. If a wooden construction then really thick insulation board in there before plasterboard on top.
Our bay window had a completely empty "roof" so our builder filled it full of insulation board. Made a huge difference.

Is cavity wall insulation an option?

We’ve got the same issue in our 50s house. Our plan of action is to insulate the bay using insulated plaster board. Possibly creating a cavity large enough to pack with more insulation. Window is also knackered (28 years old) so that’s on the list also. 10 degrees in there this morning. 🥶

@Smokeahontas it’s part of the original house as far as I’m aware. All the houses on my road are the same layout and structure.

@SoupDragon we do already have cavity wall insulation but I think that part of the house is a timber frame so not possible in the bay I would assume…? As there is no cavity to insulate?

@Monty27 yes it’s north facing 😭 thought I’d woken up in the Arctic this morning!

@SkiingIsHeaven just seen that you’ve said you can insulate between outside and inside. What sort of person would I ask to do that? Is it beyond general handyman? I’m a bit worried as i had read some stuff online about needing to ensure air flow to prevent mould so if someone does a bad job it could cause the whole timber structure to rot 😟

Also my DH is going to hate me because he put lining paper all over the walls when we decorated which took forever in the bay and he doesn’t feel the cold (would happily sleep without duvet etc) and if we do this work it’s going to need redecorating…! Although if we had plasterboard and new plaster then he wouldn’t have to line it I guess and could just paint straight onto it.

Same issue, 30s house. Our bay is definitely not a cavity wall, so we could either insulate the inside or the outside (or both). I wonder if putting a layer of foil and insulation backed membrane and shingle tiles on the outside would be the right thing to do. I worry that it would need planning permission because it's a change to the visual appearance of the house though. If we did this it would be also when upgrading the inside insulation with the foam-backed plasterboard others have mentioned. That would mean replacing the windowsill, which might then mean replacing the windows. All in all if this was done by a builder, I reckon it's easily £5-10k for the ground and upstairs together.

For us I mean - double insulating plus windows and all that, is what leads to my cost estimate.

OP, I think if you were just adding plasterboard inside it only needs a competent jobbing builder, possibly only a few days work then replastering. BUT you need to be careful of ventilation.

@Newnews A normal builder would be able to do it. I would recommend that you call your building control department at the council for advice on the void needed. Or ask an Architect.

@Newnews

Also my DH is going to hate me because he put lining paper all over the walls when we decorated which took forever in the bay and he doesn’t feel the cold (would happily sleep without duvet etc) and if we do this work it’s going to need redecorating…! Although if we had plasterboard and new plaster then he wouldn’t have to line it I guess and could just paint straight onto it.

Must cost a fortune in heating bills though....

Blinds, replacement glazing, cavity wall insulation, a refit, there's a lot of options but I'm not sure other than just switching them out for new ones which will be a solution that fully works

It's quite typical for bays to have a wooden frame, plastered over, the void full of cobwebs and dust, scarcely any insulation or draughtproofing.

You can pull the old plaster off (there will be dirt and dust). Sweep and Hoover it out, you can scrub it. I would put wood preservative on the framing and examine it for rot and worm.

You can use a piece of breathable roofing membrane at the back, tacked down to keep out draughts and spiders, pack the gap with mineral wool loft insulation, it will pack into irregular gaps, put plasterboard over the inside to form the new inside wall, and skim.

The skill needed will be the plasterer, you may find one who agrees to do the dirty work as well, but stripping and insulation are DIY jobs

If the outside is tiled, it is probably just on a wooden frame. When you next have it retiled, have it stripped off, clean out, put insulation in the gaps and use breathable roofers membrane again, it resists rain or snow blowing in. A roofer will do it, possibly an older one who's cut down on running up and down ladders

Hi OP
Wondering if you managed to do something about this and what you did?!? I have the same issue in my 1930s bedroom, with timber frame bay. Recently installed triple glazing but seems a waste of time if we are losing heat through the bay underneath!
Jen

@GoodJen we have a 1920s house, and got a plasterer in to plaster with insulating board and then skim. Ours was not insulated at all when we stripped it back to brick.m

You can get wooden sash windows renovated and have double glazed window panes put in at the same time. That doesn’t affect the decoration in the room though the refurbished wooden frames need to be painted within 6 weeks.