Aengus
Member
- Messages
- 1
- Location
- Northern Ireland
Hi there,
I'm in the process of renovating my 1850s stone cottage here in Northern Ireland. I want to install some insulation in the attic as it's currently uninsulated and thus the upstairs bedrooms get hot in the summer and cold in the winter. It has what I think is termed a collared roof so the upstairs rooms are partially in the eaves with a small (~2m wide) flat section. This means the attic space above is pretty restricted, maybe 60cm of head room and access to the eaves from the top is very difficult so I think I will need to bring the old replacement gypsum plasterboard ceilings down to install the insulation. The rafters and ceiling joists are both ~115mm high, 45mm thick and on ~300mm centers.
My plan for the sloping sections is to insulate between the rafters with 80mm flexible wood fibre (e.g. Steico Flex, Gutex Thermoflex etc) leaving a 35mm air gap beneath the roof covering, which is just slates with the remains of some lime torching, no felt, so hopefully plenty of ventilation. I've also looked at hemp insulation (Indibreath flex) or wool batts which both seem slightly cheaper so could be good options. Then fixing directly to the rafters I would use ~40mm of a denser wood fibre insulation (e.g. Gutex Thermoroom or similar). The buildup for the flat section would be similar but I will use a thicker insulation between the joists and it would be easier to use something softer like the wool as it would be fully supported. Again, on the underside of the joists I would ideally board it with 40mm wood fibre.
My main question is whether it's possible/advisable to apply a lime plaster of some sort to the wood fibre insulation, I've seen this done commonly for walls but I'm concerned that there's not enough mechanical key for applying it on the underside of the ceiling either flat or sloping sections without it slumping under it's own weight. Some suppliers seem to recommend Lime Green Solo (2x5mm coats) for this or St Astier Ecomortar (2x2mm coats) or similar. I've also seen a non-hydraulic lime hemp plaster recommended by Ty Mawr but if used for ceilings they say it should be applied to wood wool. I could forgo the extra wood fibre and use a 25mm wood wool board instead as this does look to have a much better mechanical key but obviously with some loss to the insulation value.
Does anyone have experience with replacing ceilings with wood fibre and then applying a lime plaster? Any particular products you'd recommend or avoid? Alternatively are there any glaring issues with my insulation plan? I may also add internal wall insulation of the same 40mm wood fibre mechanically fixed to non-internal walls.
Being based in Northern Ireland, sourcing materials from common UK suppliers is difficult, lots don't ship here and for those that do pallet costs can be quite high. There are some Irish suppliers I'm looking at who seem good though and stock most things.
I'm in the process of renovating my 1850s stone cottage here in Northern Ireland. I want to install some insulation in the attic as it's currently uninsulated and thus the upstairs bedrooms get hot in the summer and cold in the winter. It has what I think is termed a collared roof so the upstairs rooms are partially in the eaves with a small (~2m wide) flat section. This means the attic space above is pretty restricted, maybe 60cm of head room and access to the eaves from the top is very difficult so I think I will need to bring the old replacement gypsum plasterboard ceilings down to install the insulation. The rafters and ceiling joists are both ~115mm high, 45mm thick and on ~300mm centers.
My plan for the sloping sections is to insulate between the rafters with 80mm flexible wood fibre (e.g. Steico Flex, Gutex Thermoflex etc) leaving a 35mm air gap beneath the roof covering, which is just slates with the remains of some lime torching, no felt, so hopefully plenty of ventilation. I've also looked at hemp insulation (Indibreath flex) or wool batts which both seem slightly cheaper so could be good options. Then fixing directly to the rafters I would use ~40mm of a denser wood fibre insulation (e.g. Gutex Thermoroom or similar). The buildup for the flat section would be similar but I will use a thicker insulation between the joists and it would be easier to use something softer like the wool as it would be fully supported. Again, on the underside of the joists I would ideally board it with 40mm wood fibre.
My main question is whether it's possible/advisable to apply a lime plaster of some sort to the wood fibre insulation, I've seen this done commonly for walls but I'm concerned that there's not enough mechanical key for applying it on the underside of the ceiling either flat or sloping sections without it slumping under it's own weight. Some suppliers seem to recommend Lime Green Solo (2x5mm coats) for this or St Astier Ecomortar (2x2mm coats) or similar. I've also seen a non-hydraulic lime hemp plaster recommended by Ty Mawr but if used for ceilings they say it should be applied to wood wool. I could forgo the extra wood fibre and use a 25mm wood wool board instead as this does look to have a much better mechanical key but obviously with some loss to the insulation value.
Does anyone have experience with replacing ceilings with wood fibre and then applying a lime plaster? Any particular products you'd recommend or avoid? Alternatively are there any glaring issues with my insulation plan? I may also add internal wall insulation of the same 40mm wood fibre mechanically fixed to non-internal walls.
Being based in Northern Ireland, sourcing materials from common UK suppliers is difficult, lots don't ship here and for those that do pallet costs can be quite high. There are some Irish suppliers I'm looking at who seem good though and stock most things.
