Insulated Plasterboard - Did I Take The Wrong Option?

Atlantic1 · 10-04-2013 12:16am #1

My house is cavity (hollow) block build. I recently put insulated plasterboards on all the external bedroom walls.

I went with 62.5mm of Kingspan TW52

The thermal conductivity of it is 0.026W/mK (up to 80mm) according to the Irish Agrement Board.

The similar Xtratherm product is 0.022.

Is this a big difference and should I have gone for the Xtratherm? The prices were similar.

shgavman · 10-04-2013 1:46am

Tiny difference.

A cavity wall u factor is 0.4 W/(m²K) which is considered good. Glass can be as low as 1.1 W/(m²K).

A 0.04 difference won't make any significant difference.

Windows/doors are where most heat is lost. These kind of images illustrate that.

Don't worry about it the difference.

shgavman · 10-04-2013 1:47am

I should say, 'usually where most heat is lost'

Atlantic1 · 10-04-2013 4:43pm

Thanks Shgavman.

I'm going to do further work in the house later in the year and I'm going to use K16 or K17 plasterboard. Thermal conductivity: 0.021W/mK.

I'm sorry I didn't get it for this job too but it's a bit late now!

Still, the job turned out very well and the rooms are very cosy.

shgavman · 10-04-2013 5:08pm

I can't remember the intricacies of thermal conductivity for a stratified element (part of degree in University). Here's my vague understanding.

When they measure the thermal conductivity (or resistance, can't remember) across a stratified building element, say for example a cavity wall is a stratified element. Each component of the wall (outside skim, external block, air cavity, insulation, internal block, internal plasterboard, paint) has a R-value. Each component also has a different thickness. So, even though the R-Value of the plasterboard might be very good (small number), the plasterboard is really thin. Compare that to say a block may have a poorer R-Value but it's thicker thicker than the plasterboard so it's contribution to the overall thermal resistance of the wall might be similar.

Does that make sense? Obviously blocks won't have a good R-Value so it's silly of me to compare it but I'm trying to convey that an important factor is the thickness....I think! Haha. Sorry, as I said it's been a while and I may not even have it right. Just try to calculate the contribution of the additional plasterboard to the overall thermal resistance of the wall.

Hope that helps.

sydthebeat · 10-04-2013 7:19pm

Atlantic1 wrote: »

Thanks Shgavman.

I'm going to do further work in the house later in the year and I'm going to use K16 or K17 plasterboard. Thermal conductivity: 0.021W/mK.

I'm sorry I didn't get it for this job too but it's a bit late now!

Still, the job turned out very well and the rooms are very cosy.

do not bother with the kooltherm products, they are not worth the extra cost over the therma products, or the xtratherm products, in my opinion.

'Therma' is a polyurethane product
xtratherm thermal liner is a polyisocyanate product
'kooltherm' is a phenolic product

the first two are very similar type, they are the light creamy yellow foam that youd recognise.

the phenolic is more of a pink product. its main advantage over the others is its superior fire resistance. At retrofit levels the extra 0.01 difference is extremely negligible in the big scheme of things.

Atlantic1 · 10-04-2013 11:15pm

shgavman wrote: »

I can't remember the intricacies of thermal conductivity for a stratified element (part of degree in University). Here's my vague understanding.

When they measure the thermal conductivity (or resistance, can't remember) across a stratified building element, say for example a cavity wall is a stratified element. Each component of the wall (outside skim, external block, air cavity, insulation, internal block, internal plasterboard, paint) has a R-value. Each component also has a different thickness. So, even though the R-Value of the plasterboard might be very good (small number), the plasterboard is really thin. Compare that to say a block may have a poorer R-Value but it's thicker thicker than the plasterboard so it's contribution to the overall thermal resistance of the wall might be similar.

Does that make sense? Obviously blocks won't have a good R-Value so it's silly of me to compare it but I'm trying to convey that an important factor is the thickness....I think! Haha. Sorry, as I said it's been a while and I may not even have it right. Just try to calculate the contribution of the additional plasterboard to the overall thermal resistance of the wall.

Hope that helps.

Thanks again. Do you know which would have a better U Value . . . . a 9.5mm or a 12.5mm insulated plasterboard, with the same thickness of insulation?

shgavman · 10-04-2013 11:27pm

It's R-value and U-factor (frequently misquoted). Again, 3 mm of extra material will make an insignificant difference. Don't get blinded by the numbers. Sydthebeat seems to have more practical knowledge of the products than I do.

Atlantic1 · 10-04-2013 11:57pm

shgavman wrote: »

It's R-value and U-factor (frequently misquoted). Again, 3 mm of extra material will make an insignificant difference. Don't get blinded by the numbers. Sydthebeat seems to have more practical knowledge of the products than I do.

Yeah, Syd has advised me a number of times prior to this. A great guy to have around here!

Atlantic1 · 11-04-2013 12:01am

sydthebeat wrote: »

do not bother with the kooltherm products, they are not worth the extra cost over the therma products, or the xtratherm products, in my opinion.

'Therma' is a polyurethane product
xtratherm thermal liner is a polyisocyanate product
'kooltherm' is a phenolic product

the first two are very similar type, they are the light creamy yellow foam that youd recognise.

the phenolic is more of a pink product. its main advantage over the others is its superior fire resistance. At retrofit levels the extra 0.01 difference is extremely negligible in the big scheme of things.

Thanks, as always, Syd. :cool:

What would you go for if you were using insulated plasterboard?

Maudi · 11-04-2013 12:15am

eh??what?

sydthebeat · 11-04-2013 12:17pm

Atlantic1 wrote: »

Thanks, as always, Syd. :cool:

What would you go for if you were using insulated plasterboard?

If i was applying an insulated plasterboard i wouldnt have a preference between xtratherm thin r or the thermawall products. They are essentially the same... so whatever you can get the best deal on.

if space wasnt a huge issue, you could also consider a polystyrene drylining board. If you could get a 10% wider board for less than the PIR or PU product then it would be cost effective.

In my opinion the installation of drylining is the 'grunt' part of making a retrofit energy efficient. Making the works thermal bridge-less and more air tight is the 'finesse' part.

Atlantic1 · 11-04-2013 12:50pm

sydthebeat wrote: »

If i was applying an insulated plasterboard i wouldnt have a preference between xtratherm thin r or the thermawall products. They are essentially the same... so whatever you can get the best deal on.

if space wasnt a huge issue, you could also consider a polystyrene drylining board. If you could get a 10% wider board for less than the PIR or PU product then it would be cost effective.

In my opinion the installation of drylining is the 'grunt' part of making a retrofit energy efficient. Making the works thermal bridge-less and more air tight is the 'finesse' part.

I knew you felt that way about drylining.

Wouldn't a polystyrene drylining board have a poor U-value though?

sydthebeat · 11-04-2013 1:29pm

Atlantic1 wrote: »

I knew you felt that way about drylining.

Wouldn't a polystyrene drylining board have a poor U-value though?

drylining is a necessary process in most retrofit cases, im not against it, once its done properly

polystyrene, at thicknesses of 50-70 mm is about 10% less insulative than foam.. so thats why i was suggesting that if you can get, say, a 72.5 polystyrene sheet for less than the price of a 62.5 foam sheet then it would make financial sense. Polystyrene does have other advantages, but dealing specifically with u values, the different is minimal.

For example.....

assuming you used the same thickness sheets ie 72.5mm
if you dryline with foam and you get a 0.27 wall u value
if you dryline with polystyrene you get a 0.29 (these are just rough figures)... difference is 0.02
if you have standard double glazing, 300mm quilt in your roof and not do anything to the floor.... you are most likely going to have an average elemental u value of around 0.35 ish
On top of this you will have a thermal bridge factor of 0.15, at best.

that means that your average u value of the construction of your house is 0.35 + 0.15 = 0.5

so considering that, plus all the air tightness issues, do you think the 0.02 difference in u values between foam and polystyrene really makes any difference?

Atlantic1 · 11-04-2013 2:31pm

sydthebeat wrote: »

drylining is a necessary process in most retrofit cases, im not against it, once its done properly

polystyrene, at thicknesses of 50-70 mm is about 10% less insulative than foam.. so thats why i was suggesting that if you can get, say, a 72.5 polystyrene sheet for less than the price of a 62.5 foam sheet then it would make financial sense. Polystyrene does have other advantages, but dealing specifically with u values, the different is minimal.

For example.....

assuming you used the same thickness sheets ie 72.5mm
if you dryline with foam and you get a 0.27 wall u value
if you dryline with polystyrene you get a 0.29 (these are just rough figures)... difference is 0.02
if you have standard double glazing, 300mm quilt in your roof and not do anything to the floor.... you are most likely going to have an average elemental u value of around 0.35 ish
On top of this you will have a thermal bridge factor of 0.15, at best.

that means that your average u value of the construction of your house is 0.35 + 0.15 = 0.5

so considering that, plus all the air tightness issues, do you think the 0.02 difference in u values between foam and polystyrene really makes any difference?

I guess not, Syd.

You are wise!

sinnerboy · 11-04-2013 3:00pm

Atlantic1 wrote: »

I guess not, Syd.

You are wise!

you have no idea .....

Atlantic1 · 21-04-2013 2:44am

sinnerboy wrote: »

you have no idea .....

Which one is Syd, Sinnerboy?

Happyman42 · 22-04-2013 12:51pm

Get a room you two! (preferably insulated)

mickyd.ie · 13-09-2014 2:46pm

hi all

the info here is very good ðŸ‘ i just wanted opinion on pumping a 150 mm cavity and a 50 mm insulated board on the inside? does this sound like a good idea or are there better option?

hexosan · 13-09-2014 4:00pm

mickyd.ie wrote: »

hi all

the info here is very good ðŸ‘ i just wanted opinion on pumping a 150 mm cavity and a 50 mm insulated board on the inside? does this sound like a good idea or are there better option?

Yeah 200mm cavity and forget the insulated plasterboard

mickyd.ie · 13-09-2014 4:15pm

hexosan wrote: »

Yeah 200mm cavity and forget the insulated plasterboard

cavity is already set up , blocks are going up as we speak but would what im doing equal the 200mm cavity i should have done?

BryanF · 13-09-2014 4:37pm

mickyd.ie wrote: »

cavity is already set up , blocks are going up as we speak but would what im doing equal the 200mm cavity i should have done?

You need to plaster the room side of the block work and install air-tightness measures at the same time.

mickyd.ie · 13-09-2014 5:10pm

BryanF wrote: »

You need to plaster the room side of the block work and install air-tightness measures at the same time.

plaster and not fit insulated board or both? what is involved in airtightness?? thanks for your help

hexosan · 13-09-2014 5:13pm

If you've only just started building I suggest you learn as much as you can as fast as you can about Airtightness

mickyd.ie · 13-09-2014 5:16pm

hexosan wrote: »

If you've only just started building I suggest you learn as much as you can as fast as you can about Airtightness

ye ive just started and ill have to read up as quick as possible

BryanF · 13-09-2014 5:32pm

why not check out the search function at the top of the page. Has your architect/eng specified an air-tightness value? Were you going with wall/window vents ? What's the provisional BER looking like for spec & ventilation & heating? Drylining reduces the effectiveness of the walls thermal mass amongst other issues. Air-tightness in homes is about eliminating drafts and uncontrolled heat loss, It needs to be considered at each junction/ material change and is achieved by using caulking, tape, membranes, plaster etc

MicktheMan · 13-09-2014 9:50pm

mickyd.ie wrote: »

ye ive just started and ill have to read up as quick as possible

You might start here

mickyd.ie · 01-10-2014 9:51pm

hey all so on my block wall do i fit anything like a membrane before i fix the insulated boards?

MicktheMan · 01-10-2014 10:31pm

mickyd.ie wrote: »

hey all so on my block wall do i fit anything like a membrane before i fix the insulated boards?

Answered already

BryanF wrote: »

You need to plaster the room side of the block work and install air-tightness measures at the same time.

mickyd.ie · 01-10-2014 10:33pm

MicktheMan wrote: »

Answered already

manufacturer dont say to plaster room side of the wall though what is the advantage of doing this? thanks

MicktheMan · 01-10-2014 10:42pm

mickyd.ie wrote: »

manufacturer dont say to plaster room side of the wall though what is the advantage of doing this? thanks

Seals you external walls for airtightness.

mickyd.ie · 02-10-2014 10:35am

is this for someone looking for a passive house or do you think this should be done regardless, I am also pumping the 150 mm cavity, thanks for your help

sydthebeat · 02-10-2014 10:38am

mickyd.ie wrote: »

is this for someone looking for a passive house or do you think this should be done regardless, I am also pumping the 150 mm cavity, thanks for your help

absolutely must be done to come anywhere near reaching minimum building regulation standard of 7 m3/m2 blower door test result.

mickyd.ie · 02-10-2014 11:18am

sydthebeat wrote: »

absolutely must be done to come anywhere near reaching minimum building regulation standard of 7 m3/m2 blower door test result.

thanks for the advice , is it also a nightmare to fit rads, kitchen units ect after slabs are fitted or would u cut the slab out in these spots?

sydthebeat · 02-10-2014 11:48am

mickyd.ie wrote: »

thanks for the advice , is it also a nightmare to fit rads, kitchen units ect after slabs are fitted or would u cut the slab out in these spots?

no definitely wouldnt cut the slabs for kitchen units.

its no problem fixing, use stronger longer screws.

obviously electric chasing should be done in the blockwork, skimmed over, and the fittings cut from slabs.

BryanF · 02-10-2014 11:53am

mickyd.ie wrote: »

manufacturer dont say to plaster room side of the wall though what is the advantage of doing this? thanks

What manufacturer? The insulated slab manufacturer? You hardly expect them to consider anything behond their own product? What is your buildings expected air-tightness?

mickyd.ie · 02-10-2014 5:32pm

BryanF wrote: »

What manufacturer? The insulated slab manufacturer? You hardly expect them to consider anything behond their own product? What is your buildings expected air-tightness?

very true point, i have no idea on the air tightness as I bought this land with planning and i am tackleing it without an architect hense all the questions, i am thinking about paying someone to give me an achieveable ber and what to do to achieve this . I am on a tight budget so i want a decent result not out of this world if you get me. thanks again all this advice is very helpful

sydthebeat · 02-10-2014 6:55pm

mickyd.ie wrote: »

very true point, i have no idea on the air tightness as I bought this land with planning and i am tackleing it without an architect hense all the questions, i am thinking about paying someone to give me an achieveable ber and what to do to achieve this . I am on a tight budget so i want a decent result not out of this world if you get me. thanks again all this advice is very helpful

You must certainly shouldn't be using a public forum as a replacement for professional services.

This is the last I'll post in response to any of your posts.

mickyd.ie · 02-10-2014 7:05pm

sydthebeat wrote: »

You must certainly shouldn't be using a public forum as a replacement for professional services.

This is the last I'll post in response to any of your posts.

I've been asking advise ,i thought thats what most people on here do. dont reply to anything you dont want to pal. thanks anyway

MicktheMan · 02-10-2014 7:27pm

mickyd.ie wrote: »

very true point, i have no idea on the air tightness as I bought this land with planning and i am tackleing it without an architect hense all the questions, i am thinking about paying someone to give me an achieveable ber and what to do to achieve this . I am on a tight budget so i want a decent result not out of this world if you get me. thanks again all this advice is very helpful

So you are building a house and have no idea if what you are building will comply with building regs (i.e. the law) not to mention whether you will be comfortable in your new home.

Good luck with that.

Insulated Plasterboard - Did I Take The Wrong Option?

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