Rigid insulation to cavity block. What thickness?120 or 150?
- Thread starter galegp
- Start date
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1) your topic title says 100 or 120, your text says 120 or 150.. struggling to make up your mind? what is your criteria for perfection? lowest cost? best U value? best availability at short notice? least hassle to build?
2) what is the expected temperature difference between each side of the wall, year round average?
2) what is the expected temperature difference between each side of the wall, year round average?
1) Sorry I meant between 120mm and 150mm. My criteria for perfection is U Value. This room is currently an attached garage to the house. It is very cold and built in single hollow block. Over the ceiling there is a roof. My plan is to fit insulated boards using mushroom fixings.
2) Outside temperature 8 degrees. Inside temperature 15. I’d say 7-10 degrees difference.
2) Outside temperature 8 degrees. Inside temperature 15. I’d say 7-10 degrees difference.
So the garage is single skin brick and can effectively be regarded as an extension to the house. The wall between house and garage is uninsulated. After works are complete and the garage has become a playroom it will be a part of the house like any other, and the temperature in the playroom will be the same as that in the house, so the effective temperature drop across the wall will be 0 degrees
You want the lowest U value, hang the cost or complications to building this will bring. The wall will be insulated internally and another wall constructed
Personally, I'd render the existing skin with a non waterproof render on the inside, then line it with 100mm of PIR insulation. The purpose of the render is to seal up gaps and cracks that leak air, but still allows a path for moisture to take out of the wall.
After that, construct a lightweight timber frame wall 90mm wide, sitting on a small block or brick upstand and a dpc. It's lighter and faster to construct than a masonry leaf. The timber frame panels can be filled with 50mm of PIR or 90mm of mineral wool. You can then line the internal face with OSB, run a breather membrane such as tyvek airguard over the OSB and seal it together to reduce the opportunity for draughts to nil. The purpose of the OSB is to provide a surface to fit the membranes to, afford them some protection against plasterboard hole making activities (using a blunt pointed saw) and it provides a surface to mount electric boxes etc to
Add 25mm battens over the top of this, and use them to mechanically fix the joints in the airguard (which will be glued) as well as at other points along the wall (600mm spacings). Run your services in the void created and then hang your plasterboard. The tyvek can be ordered reflective, and in combination with the service void cavity has a minor improvement in U.
This wall construction would have a U around 0.14 and give you something to hang your internal stuff on/in at the loss of 65mm over just lining the wall with 150mm of PIR backed plasterboard achieves the same U but isn't as airtight and has nowhere to run services/hang shelves etc.
You reach a point with insulating where it isn't worth throwing the money at insulation without making efforts to improve the air tightness. 500mm of kingspan standing up in the garden is going to do nothing to keep your house warm
Also, for reference purposes, a house built to Passivhaus standards must achieve a wall U value of 0.15 or better. British building regs is 0.30 or better
You want the lowest U value, hang the cost or complications to building this will bring. The wall will be insulated internally and another wall constructed
Personally, I'd render the existing skin with a non waterproof render on the inside, then line it with 100mm of PIR insulation. The purpose of the render is to seal up gaps and cracks that leak air, but still allows a path for moisture to take out of the wall.
After that, construct a lightweight timber frame wall 90mm wide, sitting on a small block or brick upstand and a dpc. It's lighter and faster to construct than a masonry leaf. The timber frame panels can be filled with 50mm of PIR or 90mm of mineral wool. You can then line the internal face with OSB, run a breather membrane such as tyvek airguard over the OSB and seal it together to reduce the opportunity for draughts to nil. The purpose of the OSB is to provide a surface to fit the membranes to, afford them some protection against plasterboard hole making activities (using a blunt pointed saw) and it provides a surface to mount electric boxes etc to
Add 25mm battens over the top of this, and use them to mechanically fix the joints in the airguard (which will be glued) as well as at other points along the wall (600mm spacings). Run your services in the void created and then hang your plasterboard. The tyvek can be ordered reflective, and in combination with the service void cavity has a minor improvement in U.
This wall construction would have a U around 0.14 and give you something to hang your internal stuff on/in at the loss of 65mm over just lining the wall with 150mm of PIR backed plasterboard achieves the same U but isn't as airtight and has nowhere to run services/hang shelves etc.
You reach a point with insulating where it isn't worth throwing the money at insulation without making efforts to improve the air tightness. 500mm of kingspan standing up in the garden is going to do nothing to keep your house warm
Also, for reference purposes, a house built to Passivhaus standards must achieve a wall U value of 0.15 or better. British building regs is 0.30 or better
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Thanks very much for the info. Definitely something for me to think about.
Now can I ask you for your opinion on my plan.
Render the brick wall with non-waterproof render and then fix 120 PIR and plasterboard to the wall using mushroom fixings. I know this will not achieve the best U rate but my garage is very narrow (2.40m) and perhaps my budget is also limited.
Thanks.
Now can I ask you for your opinion on my plan.
Render the brick wall with non-waterproof render and then fix 120 PIR and plasterboard to the wall using mushroom fixings. I know this will not achieve the best U rate but my garage is very narrow (2.40m) and perhaps my budget is also limited.
Thanks.
The wall can be insulated externally if space is at a premium, and the external treatment of the wall could be a lightweight cladding, render, brick slip etc. While i think it may technically require planning approval to fit EWI it ought to be relatively easy to obtain or if you just did it, likely they wouldn't really care so long as the new finish was a match for the existing or something that would be within the scope of permitted development
Note that you need building regs approval in any case because youre upgrading a thermal element/have to have considerations to moisture. If you make a really good job of sealing up any draughts you should ensure that the room is adequately ventilated to prevent condensation and mould issues. this can be achieved by trickle venting the windows (ugh - there's something deeply wrong about building a draught free building and then deliberately banging holes in it to let the heat out as well as the moisture) or fitting a small MVHR. You might then get the bug and seal up the rest of the house and have that have a ventilation system too
Note that you need building regs approval in any case because youre upgrading a thermal element/have to have considerations to moisture. If you make a really good job of sealing up any draughts you should ensure that the room is adequately ventilated to prevent condensation and mould issues. this can be achieved by trickle venting the windows (ugh - there's something deeply wrong about building a draught free building and then deliberately banging holes in it to let the heat out as well as the moisture) or fitting a small MVHR. You might then get the bug and seal up the rest of the house and have that have a ventilation system too
Morning.
Regarding the flow. I need to raise it 90mm.
What is better option?
1- Flooring floor. Lay damp proof membrane + 60mm rigid insulation + 18mm tongue and groove chipboard.
Or
2- Make a wooden frame with joists and fit rigid insulation in between it with chipboard or plywood on top.
Thanks for your help.
I
Regarding the flow. I need to raise it 90mm.
What is better option?
1- Flooring floor. Lay damp proof membrane + 60mm rigid insulation + 18mm tongue and groove chipboard.
Or
2- Make a wooden frame with joists and fit rigid insulation in between it with chipboard or plywood on top.
Thanks for your help.
I
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