To thermaboard (dryline) or not.

[hayabusa]

Hi all,
Just after building the shell of my house. Conventional build, standard block and cavity. I put in a 50mm kingspan board in the cavity. TW50, i think it is called.
However Spoke to someone last week and explaned that I was insulating the interior of the external walls with a 12mm plasterboard and 37 mm insulation board (total 50 mm thermaboard). I am going with UFH also. That then raised the issue of thermal mass, that I was reducing it by insulating the walls that are already insulated hence the house will cool down quicker. Also If i dryline the internal walls then the TW 50 already in the cavity will be rendered useless.
I would like you input on this one. Should I do the internal peremeter walls with this board or not.

Slighty confused as I do not want compromise on insulation, however I do not want to spend on it if it is not fully effective.

Thanks

 

[kilbird]

Hayabusa - also interested in this one. Am worried that my ufh will by teaering out thro walls and was thinking of doing the exact same as u - am very interested tto hear what others have to say

 

[Superman]

That then raised the issue of thermal mass, that I was reducing it by insulating the walls that are already insulated hence the house will cool down quicker.

Not by too much though - you still have all the internal walls, the concrete floor etc. which act as a thermal mass - you are only losing 1 surface out of 6 (if you include the ceiling).

lso If i dryline the internal walls then the TW 50 already in the cavity will be rendered useless.

No you don't - you also get the effect of this insulation. This insulation would only be rendered useless if there were a ventilated cavity between the drylining and your insulation (which there is not - the cavity is on the far side of your TW50).

I would like you input on this one. Should I do the internal peremeter walls with this board or not.

Do it.
Spending money on insulation is the second best way of saving money on your build. (The best is reducing draughts).

 

[Birroc]

Superman,

Re daughts, have you heard of this new system where you make the house completely airtight by installing a 'breathable' plastic membrane on all interior walls/floors/ceilngs when the walls and roof are built? Some guy was trying to sell it to me last week. Costs 2000 to install.

 

[extopia]

Hayabusa - also interested in this one. Am worried that my ufh will by teaering out thro walls and was thinking of doing the exact same as u - am very interested tto hear what others have to say

Your floor should be insulated at the sides (as well as the bottom, underneath the UFH pipes) to prevent the kind of thermal bridging your mention here.

 

[hayabusa]

Ok, Thanks for the replies.
Looks like I will continue with drylining.

Extopia,
My plan for insulating at the sides is as follows. Let the thermaboard down to the subfloor. Put DPM under the insulation an UFH approx 1 foot under the insulation and run it up the wall and tape to the thermaboard. This will prevent coldbridging, and will also protect the thermaboard (plasterboard) from getting wet and damaged. Is this good practice?? Then when it dries cut the DPM above the Finished floor.

Thanks

 

[extopia]

I don't know if this is good practice tbh - you should follow the manufacturer's recommended procedure for whatever product you are using.

 

[davidoco]

run it up the wall and tape to the thermaboard.

As previous poster stated you should look up the various guidelines on this. Once you see as drawing for how they run the DPM out over the inner leaf you'll see how it works.

 

[Superman]

Re daughts, have you heard of this new system where you make the house completely airtight by installing a 'breathable' plastic membrane on all interior walls/floors/ceilngs when the walls and roof are built? Some guy was trying to sell it to me last week. Costs 2000 to install.

Yes I've heard of various companies. Haven't formed an opinion about them yet I'm afraid.