Insulating an old bathroom

[Craig24]

I'm looking for the best option on insulating my bathroom, it's a Victorian terrace (1895), it has cavity walls (very narrow cavity).

The 2 options I am looking at would be,

- Insulated plasterboard straight onto the walls (worried about the break in the built in vapor barrier at each join).
- The second option would be stud the walls, PIR boards, vapor barrier sheet and tape any joints, then standard plasterboard over the top.

Any advice? Thanks

 

[noseall]

I'm looking for the best option on insulating my bathroom, it's a Victorian terrace (1895), it has cavity walls (very narrow cavity).

The 2 options I am looking at would be,

- Insulated plasterboard straight onto the walls (worried about the break in the built in vapor barrier at each join).
- The second option would be stud the walls, PIR boards, vapor barrier sheet and tape any joints, then standard plasterboard over the top.

Any advice? Thanks

I've posted a fair bit lately whereby we trap PIR boards against a wall as well as a layer of DPM, using 50mm x 50mm studs, the fill in between the studs also, foil taping all joints as you go.

However, you could slim that down a bit by foam fixing some 50mm PIR boards direct to the walls (as you won't need DPM), then fix 2" x 1" roof battens straight through the sheets and into the wall. Then fit 25mm insulation between the battens (foil tape all joints), then fix Duplex boards.

 

[Ivor Windybottom]

Best to avoid plasterboard in a bathroom, definitely anywhere near a bath or shower. Opinions differ, housebuilders love the stuff as it's the cheapest option but they don't care what the place looks like beyond the warranty period.

You could clad the walls with tile backer board. It doesn't normally have a stated U-value (insulation rating), but it consists of two waterproof outer layers with foamed plastic in the middle. Totally waterproof, rock hard and it insulates. Available from any tile outlet in assorted thicknesses, choose whatever thickness/insulation compromise you think is best.

Various mounting methods and opinions, I'd be inclined to bed directly onto the wall on tile adhesive. You could also then screw on with stainless screws and insulation washers into wall plugs after it sets, just as a safeguard. Apply a tanking kit around the bath or shower, then just tile directly over.

Obviously this commits you to fully tiling the bathroom. But that's usually for the best anyway.

How to Install Tile Backer Boards

www.tilefixstore.co.uk

 

[Murdochcat]

Fit a larger radiator and decent extractor fan ?

 

[JohnD]

You don't need studs

25mm of foam boards would make a tremendous improvement. You could hack off the old plaster first.

What sort of extractor fan have you got, and when do you use it?

If you have access in the loft above the ceiling, you could fit a ducted inline fan. Can be much more powerful and quiet than ordinary wall fans. You must of course duct the steam outside, not into the loft.

 

[Craig24]

I’ve currently got a Tornado ST100T Silent 100mm wall fan, it comes on with the light and runs for 10 mins after.

I’m concerned about moisture penetrating the boards with it being in a bathroom, that’s why I was considering studs, pir and then a vapour barrier over it all?

 

[JohnD]

What do you think studs will do?

I don't know the throughput of that fan but I expect it is around 80 cubic metres per hour.

If you have steamy showers you need about 240

Unless you leave the fan running continually

Edit
As it is a timed model, you should be able in increase the run-on to 20 or 30 minutes with the adjuster inside the casing, which will extract more steam.

But in my case the biggest improvement was CWI which made the room and walls warmer. I don't get condensation on the tiles or mirror now. Luckily your terraced house has very few external walls.

I see it now, the spec looks remarkably similar to the excellent Envirovent, 100 cu.m/hr, although it does not mention rubber motor mounts or ball-bearing motor.

Bathroom Fan Silent Tornado ST100T Zone 1 Extractor with Timer | Extractor Fan World

Shop for the Bathroom Fan Silent Tornado ST100T Zone 1 Extractor with Timer. Order online from Extractor Fan World.

www.extractorfanworld.co.uk

 

[mrrusty]

I also have a narrow cavity. On the window outside wall I have 72.5mm insulated PB (60+12.5) fixed direct, on the shower outside wall I have 2x3's on edge filled with PIR and overboarded with tilebacker cement board. It's been a perfect solution - we don't get condensation on the walls at all even with long showers - our extract is an inline over the shower cubicle. My house relies on the ventilated cavity to control interstitial condensation caused by the insulation resulting in colder internal walls. ( that's the theory anyway - so far so good). I would not consider CWI for this reason.