Insulated plasterboards - are thinner ones worth installing?

karenhalsey

We are wanting to install insulated plasterboards into an outbuilding. It is a small space so we need to maximise floor space. The energy trust recommends 60mm thickness but sizes for purchase range from 22mm to 72 mm. Would thinner insulation boards (e.g. 25 mm) still be effective? Any advice much appreciated.  Thank you.

ThisIsWeird

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

moneysaver1978

karenhalsey said:

We are wanting to install insulated plasterboards into an outbuilding. It is a small space so we need to maximise floor space. The energy trust recommends 60mm thickness but sizes for purchase range from 22mm to 72 mm. Would thinner insulation boards (e.g. 25 mm) still be effective? Any advice much appreciated.  Thank you.

In the walls, right?

stuart45

What is the wall's construction?

moneysaver1978

ThisIsWeird said:

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

Sorry to hijack this thread, but does this mean that insulated plasterboards are as good as 200mm Knauf roll insulation (on top of the existing 100mm)?

CSI_Yorkshire

moneysaver1978 said:

ThisIsWeird said:

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

Sorry to hijack this thread, but does this mean that insulated plasterboards are as good as 200mm Knauf roll insulation (on top of the existing 100mm)?

for the same U-value.

moneysaver1978

CSI_Yorkshire said:

moneysaver1978 said:

ThisIsWeird said:

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

Sorry to hijack this thread, but does this mean that insulated plasterboards are as good as 200mm Knauf roll insulation (on top of the existing 100mm)?

for the same U-value.

So if you do not want to compromise the height of the loft, would insulated plasterboards be a viable (pricer) alternative?

CSI_Yorkshire

moneysaver1978 said:

CSI_Yorkshire said:

moneysaver1978 said:

ThisIsWeird said:

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

Sorry to hijack this thread, but does this mean that insulated plasterboards are as good as 200mm Knauf roll insulation (on top of the existing 100mm)?

for the same U-value.

So if you do not want to compromise the height of the loft, would insulated plasterboards be a viable (pricer) alternative?

You'd need what, about 150-170mm of plasterboard for the same insulation of 270mm rockwool I think?

It's fine to use in floor voids, so I can't see any reason it couldn't be used in the loft floor.

ThisIsWeird

Hi M78.
I haven't compared their relative insulation values, but I would postulate that, say, 150mm of PIR - ie typical joist height - fitted snugly down against the ceiling would provide a highly effective level of insulation. As you say, tho', it wouldn't be cheap, and fitting it snugly would not be easy. 
An alternative would be to lose a couple of height inches from the room below, and line the ceiling with insulated p'board, and then just a 'fill' of loft insulation to the tops of the joists. 
Why don't you want to compromise the loft space height? 

FreeBear

CSI_Yorkshire said:

moneysaver1978 said:

CSI_Yorkshire said:

moneysaver1978 said:

ThisIsWeird said:

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

Sorry to hijack this thread, but does this mean that insulated plasterboards are as good as 200mm Knauf roll insulation (on top of the existing 100mm)?

for the same U-value.

So if you do not want to compromise the height of the loft, would insulated plasterboards be a viable (pricer) alternative?

You'd need what, about 150-170mm of plasterboard for the same insulation of 270mm rockwool I think?

It's fine to use in floor voids, so I can't see any reason it couldn't be used in the loft floor.

The size of the loft hatch will limit how big a piece you can get up there. You'd probably need to set up a cutting bench to slice the sheets in to manageable widths before taking them in to the loft.

ThisIsWeird

FreeBear said:

CSI_Yorkshire said:

moneysaver1978 said:

CSI_Yorkshire said:

moneysaver1978 said:

ThisIsWeird said:

In short, yes. 
Whatever insulation you add should have a dramatic effect, but the more you add, the less the additional improvement. But still always fit as much as you can.

A way to look at it is like this; imagine an uninsulated wall - say sheet metal. If you add 1" of insulation, let's say that reduces heat transfer by a factor of 10 - not unreasonable - so a tenth of the heat now escapes. Now add another inch of insulation - how much additional effect would this have? Only a tenth. 

So, any/all insulation is good. 

Sorry to hijack this thread, but does this mean that insulated plasterboards are as good as 200mm Knauf roll insulation (on top of the existing 100mm)?

for the same U-value.

So if you do not want to compromise the height of the loft, would insulated plasterboards be a viable (pricer) alternative?

You'd need what, about 150-170mm of plasterboard for the same insulation of 270mm rockwool I think?

It's fine to use in floor voids, so I can't see any reason it couldn't be used in the loft floor.

The size of the loft hatch will limit how big a piece you can get up there. You'd probably need to set up a cutting bench to slice the sheets in to manageable widths before taking them in to the loft.

Good point. But I guess you'd want them inner-joist width anyway, so could be pre-sliced before taking them up.
Rigid PIR would be a lot of work to do accurately, tho', so I'm not really suggesting it - unless someone wanted max insulation for depth. 
I guess they could be pre-sliced for an 'easy' fit, and then expanding-foam them into position to seal them, but that brings other potential issues! And all cables would need repositioning first.

Tbh, if someone has a typical loft with 6" joists, I'm going to suggest that a firmly-packed infill of normal loft insulation and boarded over will give a satisfactory level of ceiling insulation. If only 4", then sitting a series of 2" blocks along them all to sit the boards on should suffice.
A possible concern, tho' - could there be a risk of condensation forming in that relatively unventilated layer?
Best ceiling insulation of all, I'd suggest, would be insul-p'board lining of the actual ceiling below, but that's disruptive and will lose room height.