best type insulation for attic conversion

RobAMerc

hi all,

I have been given 3 quotes for an attic conversion, howver all 3 offer differing insulation.

1: sprayfoam under roof
2: 100 foil back insulated plasterboard
3: 40mm super quilt

All are coing in at around the same money

would anyone here be able to tell me which of these is the best insulation ?

Thanks

sydthebeat

What u value will each give....

Because if they not the same, then you after not comparing equivalents

BryanF

In an existing roof where you haven’t the luxury of breathable felt, how will the builder ensure ventilation of the roof structure? This will impact the insulation type and method of install.

Tefral

What are you insulating it for first of all?

Sprayfoam wont give you the same U-Value as PIR anyway for a start.

feckthisgenie

BryanF wrote: »

In an existing roof where you haven’t the luxury of breathable felt, how will the builder ensure ventilation of the roof structure? This will impact the insulation type and method of install.

I'm looking at lcynene sprayfoam for my attic conversion. Stupid question but how do you know or find out if the existing felt in is breathable?

listermint

feckthisgenie wrote: »

I'm looking at lcynene sprayfoam for my attic conversion. Stupid question but how do you know or find out if the existing felt in is breathable?

Look at it. If it's not fabric type then most likely it's older bitumen based ****e.

feckthisgenie

listermint wrote: »

Look at it. If it's not fabric type then most likely it's older bitumen based ****e.

Cheers will do. House built in 2005 so modern enough. Hopefully that means it's breathable felt

MicktheMan

feckthisgenie wrote: »

I'm looking at lcynene sprayfoam for my attic conversion. Stupid question but how do you know or find out if the existing felt in is breathable?

Remember that spray foam is not airtight (regardless of what's claimed by the installer) so you will also have to consider what your airtight barrier will be and how to implement.

feckthisgenie

MicktheMan wrote: »

Remember that spray foam is not airtight (regardless of what's claimed by the installer) so you will also have to consider what your airtight barrier will be and how to implement.

If it expands and gets into every nook and cranny I'm sure it will prevent cold getting in or am I missing something?

BryanF

feckthisgenie wrote: »

If it expands and gets into every nook and cranny I'm sure it will prevent cold getting in or am I missing something?

Yes.

Just replace the words ‘vapour barrier’ every time your see the words ‘air-tightness’

Internal vapour should not make its way into a roof/wall structure.

feckthisgenie

BryanF wrote: »

Yes.

Just replace the words ‘vapour barrier’ every time your see the words ‘air-tightness’

Internal vapour should not make its way into a roof/wall structure.

???????

MicktheMan

feckthisgenie wrote: »

If it expands and gets into every nook and cranny I'm sure it will prevent cold getting in or am I missing something?

If

feckthisgenie

MicktheMan wrote: »

If

It does

MicktheMan

feckthisgenie wrote: »

It does

It doesn't create a continuous barrier to air, therefore it will allow cold air in thus cooling the internal space and, as BryanF alluded to above, allow moisture laden internal air into a cold roof structure rising the risk considerably of timber rot and eventual structural failure.

feckthisgenie

MicktheMan wrote: »

It doesn't create a continuous barrier to air, therefore it will allow cold air in thus cooling the internal space and, as BryanF alluded to above, allow moisture laden internal air into a cold roof structure rising the risk considerably of timber rot and eventual structural failure.

So Icynene are advertising lies with their statement below? How did the achieve the certifications listed below?

Icynene is the only foam on the market to have achieved BBA, ETA and IAB certifications. Icynene absorbs the lowest amount of moisture and has the highest level of vapour resistivity of any soft foam on the market.

MicktheMan

feckthisgenie wrote: »

So Icynene are advertising lies with their statement below? How did the achieve the certifications listed below?

Icynene is the only foam on the market to have achieved BBA, ETA and IAB certifications. Icynene absorbs the lowest amount of moisture and has the highest level of vapour resistivity of any soft foam on the market.

And said certification is silent on air tightness which was my initial point.

feckthisgenie

MicktheMan wrote: »

And said certification is silent on air tightness which was my initial point.

Air tightness is not my main concern as the house is not an A rated house. My house is 15 years old and probably BER rating of C so the Lcynene will actually make my house warmer then it currently is. As long as the insulation is breathable and ventilation is good so that the rafters don't rot , that's my main issue.

griffdaddy

RobAMerc wrote: »

hi all,

I have been given 3 quotes for an attic conversion, howver all 3 offer differing insulation.

1: sprayfoam under roof
2: 100 foil back insulated plasterboard
3: 40mm super quilt

All are coing in at around the same money

would anyone here be able to tell me which of these is the best insulation ?

Thanks

Hi, I'm looking to do the same in my end of terrace. Do you mind me asking what kind of quotes you're getting?

I'm also wondering if there'll be any access issues because the attic is converted.

Thanks,

Griff

sydthebeat

feckthisgenie wrote: »

Air tightness is not my main concern as the house is not an A rated house. My house is 15 years old and probably BER rating of C so the Lcynene will actually make my house warmer then it currently is. As long as the insulation is breathable and ventilation is good so that the rafters don't rot , that's my main issue.

where will the ventilation be?

MicktheMan

feckthisgenie wrote: »

Air tightness is not my main concern as the house is not an A rated house. My house is 15 years old and probably BER rating of C so the Lcynene will actually make my house warmer then it currently is. As long as the insulation is breathable and ventilation is good so that the rafters don't rot , that's my main issue.

What's an A-rated house got to do with it?

So you're planning on making a great big hole in the top of your house (attic conversion) and are not concerned about heat loss due to air leakage. That's grand so.:rolleyes:

Good luck.

feckthisgenie

MicktheMan wrote: »

What's an A-rated house got to do with it?

So you're planning on making a great big hole in the top of your house (attic conversion) and are not concerned about heat loss due to air leakage. That's grand so.:rolleyes:

Good luck.

A big hole?? It's an non habitable attic conversion, the roof is not altered apart from a few vulex. You sound like a bit of a drama queen to be honest 🙄. Lcynene is air tight, is good enough for me.

Calahonda52

feckthisgenie wrote: »

A big hole?? It's an non habitable attic conversion, the roof is not altered apart from a few vulex. You sound like a bit of a drama queen to be honest ��. Lcynene is air tight, is good enough for me.

I suggest you look in the mirror.
.
The bloke you are pi$$ing in on top of is probably one of the most experienced blokes on this topic in business in Ireland and that is you best shot?.
.
Another one for the ignore list

GreeBo

feckthisgenie wrote: »

. Icynene absorbs the lowest amount of moisture and has the highest level of vapour resistivity of any soft foam on the market.

My bucket leaks the least amount of water of any bucket in the market...it still leaks water though.

feckthisgenie

Calahonda52 wrote: »

I suggest you look in the mirror.
.
The bloke you are pi$$ing in on top of is probably one of the most experienced blokes on this topic in business in Ireland and that is you best shot?.
.
Another one for the ignore list

That doesn't give him the right to be condescending to people on here. Half of these so called "experts" giving advice on here use too much technical jargon no loss. You do realise people asking advice on here are lay people .

BryanF

I think we’ll leave it there, the OP hasn’t posted since, thanks