IPx4 wall mounted 2kW fan heater. Dimplex FX20VE springs to mind with inbuilt runback timer adjustable
5-100min (turns itself off). Needs to be mounted 60cm from the edge of any bath or shower. Very fast warmup even in solid double brick.
Extractor on the shower & kitchen.
- Elica Krea in Stainless from John Lewis is =A389 or so, looks good as a mixture of "old design, modern finish, stainless, mesh filters rather than ugly holes"
- It needs a 127mm core drill, buy Blue Spot from Amazon UK or hire for a day (about =A330-35 for deliver/collect same day)
You need to get excess moisture out of kitchens vs loading the house - and not drying washing on radiators or in front of radiant gas fires which will saturate a house!
Insulation on the inside.
- The idea behind insulation on the outside is you keep the thermal mass of bricks which heat up over many weeks. The downside is for that "thermal mass" to work you need continuous internal heating to build up that store of heat. Additionally insulation on the outside shuts off any solar gain if you are south facing, which even in winter is still something.
- The idea behind insulation on the inside is you only have to heat the air in that room "on demand" rather than trying to build up a store of heat in bricks, which in a bathroom/kitchen is not practical.
- Insulation on the inside gives rapid heatup from limited heating (towel rail, wall mounted fan heater).
Marmox behind the tiles.
12.5mm is barely noticeable, 20mm is noticeably, 30mm should be very good indeed. It is not cheap, but does work.
Going Kingspan/Celotex (PIR) insulation...
- Wall is covered in a wood batten frame
- 25mm Celotex is pushed into the wooden frame
- 12mm Celotex covers the wooden frame (cold bridge)
- 9.5-12.5mm Plasterboard covers the lot
- Skim of plaster
- Tiles
That gives you 50mm total thickness, of which only 37mm is Insulation which also loses 5-10% of its U-value due to cold bridging from the wooden frame.
Going Marmox insulation...
- Wall is Mapei Primer G or S (sealed)
- 20-30-40-50mm Marmox is bonded by Mapei Keraflex
- Skim over with plaster
- Tiles
The key difference with Marmox is 100% of the thickness is insulation and there is no cold bridging or wooden frame to rot. Marmox is thus ideal for rooms tight on wall thickness (small kitchens, small bathrooms).
Bare Insulation figures...
- 20mm PIR =3D 29mm Marmox
- 30mm PIR =3D 43mm Marmox
- 35mm PIR =3D 51mm Marmox
- 65mm PIR =3D 94mm Marmox
Installed Insulation figures...
- Solid 9" brick wall, U-value =3D 2.11
- Solid 9" brick wall with 30mm PIR & 12.5mm PB =3D 43mm combined, U- value =3D 0.43 =3D=3D 43mm Marmox (same thickness)
- Solid 9" brick wall with 35mm PIR & 12.5mm PB =3D 47.5mm combined, U- value =3D 0.40 =3D=3D 50mm Marmox (same thickness)
- Solid 9" brick wall with 40mm PIR & 12.5mm PB =3D 52.5mm combined, U- value =3D 0.37 =3D=3D 58mm Marmox
You can see how PIR whilst better suffers due to space "lost" to plasterboard. It's surprising no-one has stuck XPS to PIR foam or done a Marmox with PIR foam (XPS is somewhat stronger than PIR).
Real world:
- Solid 9" brick with 30mm Marmox =3D 66% less heat loss (U value falls from 2.11 to 0.72)
- If it took 1000W to heat it before, that figure is now 340W
- Comfort wise the room will also warm almost instantly
The downside.
- Marmox is very expensive.
- 25mm PIR for 2400x1200 is about =A312
- 30mm Marmox for 1250x600 (1/4 the size) is about =A318
That is =A312 v =A360 for the same area. Admittedly Marmox is easier to fit re labour, plus no wood battens, plus no plasterboard, but it does need =A36 Mapei Primer-G/S and =A37/5kg Mapei Keraflex.
So Marmox is good for those tight situations or where waterproofing is key (solid wall kitchens, bathrooms etc).
What we need is a PIR version of Marmox (cement/PIR/cement), I believe one does exist - but I've never seen it for sale. I think Kingspan make it. A simple PIR (Kingspan) rather than XPS (Marmox) board which can be bonded to a wall & plaster skimmed, job done fast, ideal for DIY sheds.