Nemesis
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Well, I wonder if in order to get it all has to comply with the latest building regs?
If in doubt, give them a bell.
If in doubt, give them a bell.
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To put this in some perspective as you may feel I have slighted the use of their product...
As part of this thread Ian posted about using it to insulate his loft with an existing lath and plaster ceiling, when he relays the tiles.
I've read the on-line leaflets and find myself on the brink of posting something for Ian along the lines of, you want to keep your ceiling intact, the moisture control techno stuff all sounds plausible, if I found myself in your situation, I'd give it a go. I almost said that in my first post on the subject.
But then, on their own website, they have a third party document which says, hey, actually, you do have to go with standard thinking on this subject and fit a vapour barrier. So I find myself thinking this is a shame as this looked like the perfect application for their product but now it's blown out of the water (no pun).
So I think Ian needs to be certain that they understand that he cannot fit a vapour barrier and take it from there
As part of this thread Ian posted about using it to insulate his loft with an existing lath and plaster ceiling, when he relays the tiles.
I've read the on-line leaflets and find myself on the brink of posting something for Ian along the lines of, you want to keep your ceiling intact, the moisture control techno stuff all sounds plausible, if I found myself in your situation, I'd give it a go. I almost said that in my first post on the subject.
But then, on their own website, they have a third party document which says, hey, actually, you do have to go with standard thinking on this subject and fit a vapour barrier. So I find myself thinking this is a shame as this looked like the perfect application for their product but now it's blown out of the water (no pun).
So I think Ian needs to be certain that they understand that he cannot fit a vapour barrier and take it from there
Nemesis
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I would call them. Genuine people and helpful when I have called.
I discussed my requirements at great length with their technical advisor on the 'phone some time ago, and got the following response by email:
Good Morning Ian,
Thank you for your email and interest in Thermafleece.Following our detailed telephone conversation the following points are confirmed.The breather membrane should have a between rafter sag for natural drainage of 10 - 15mm. Thermafleece 50mm thick can be placed in the rafter depth. This will allow the plaster key through the laths to take effect and will not involve unnecessary setting out problems. The vertical walls can be insulated with Thermafleece to your chosen depth, and a breather membrane fixed to the back of the framing to hold the insulation in place. Across the ceiling joists you can insulate to a depth of, say, 250mm to compensate for the thinner areas of the sloping roof sections. This will give a good result and the overall effect should be as you want. I hope these points are in accordance with your requirements.
Best regards
However, as noted this does *not* cover the requirement or otherwise for a vapour barrier on the warm side of the ceiling explicitly. It is implicit in that there is no way of keeping the lath and plaster ceiling exposed whilst fitting an adequate vapour barrier. You can't fit the barrier over the ceiling laths before putting the insulation in either, as this would be impossible to secure properly.
The discussions of the last day or so have given me and others pause for thought. There is, as GK says, ambiguity between the technical diagrams and the BBA certificate. We just need to go to Second Nature with this and get written clarification, which is what I intend to do.
We are all, I am sure, aware of the need to let traditional buildings breathe, and the importance of not compromising this principal when retro-fitting insulation. Thermafleece does seem to be an ideal product in addressing this problem.
From an eco-friendly perspective, I am very wary of employing urethane board insulation, as is common practice.
There is plenty of proof that traditional roofs perform well and last for centuries if the covering is kept in proper repair, the rain water is disposed of efficiently, and ventilation is maintained. No sarking, no felt, no breather membranes and no insulation. My house is a good example.
I don't know of any hard evidence of an historic roof that has been insulated with wool, and has survived without problem despite a lack of modern vapour barriers or breather membranes. There may be some evidence out there. I am sure that wool was traditionally used for insulation, although lack of vermin proofing may have been a problem.
I won't introduce a risk of rot into my roof just to insulate it. Once the roof tiles are put back on, that's it. I cannot afford to take it off and redo it if there's a problem.
Good Morning Ian,
Thank you for your email and interest in Thermafleece.Following our detailed telephone conversation the following points are confirmed.The breather membrane should have a between rafter sag for natural drainage of 10 - 15mm. Thermafleece 50mm thick can be placed in the rafter depth. This will allow the plaster key through the laths to take effect and will not involve unnecessary setting out problems. The vertical walls can be insulated with Thermafleece to your chosen depth, and a breather membrane fixed to the back of the framing to hold the insulation in place. Across the ceiling joists you can insulate to a depth of, say, 250mm to compensate for the thinner areas of the sloping roof sections. This will give a good result and the overall effect should be as you want. I hope these points are in accordance with your requirements.
Best regards
However, as noted this does *not* cover the requirement or otherwise for a vapour barrier on the warm side of the ceiling explicitly. It is implicit in that there is no way of keeping the lath and plaster ceiling exposed whilst fitting an adequate vapour barrier. You can't fit the barrier over the ceiling laths before putting the insulation in either, as this would be impossible to secure properly.
The discussions of the last day or so have given me and others pause for thought. There is, as GK says, ambiguity between the technical diagrams and the BBA certificate. We just need to go to Second Nature with this and get written clarification, which is what I intend to do.
We are all, I am sure, aware of the need to let traditional buildings breathe, and the importance of not compromising this principal when retro-fitting insulation. Thermafleece does seem to be an ideal product in addressing this problem.
From an eco-friendly perspective, I am very wary of employing urethane board insulation, as is common practice.
There is plenty of proof that traditional roofs perform well and last for centuries if the covering is kept in proper repair, the rain water is disposed of efficiently, and ventilation is maintained. No sarking, no felt, no breather membranes and no insulation. My house is a good example.
I don't know of any hard evidence of an historic roof that has been insulated with wool, and has survived without problem despite a lack of modern vapour barriers or breather membranes. There may be some evidence out there. I am sure that wool was traditionally used for insulation, although lack of vermin proofing may have been a problem.
I won't introduce a risk of rot into my roof just to insulate it. Once the roof tiles are put back on, that's it. I cannot afford to take it off and redo it if there's a problem.
Lime
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May I say that I had no idea that I was about to stir up a hornets nest concerning vapour barriers.
Now I know more about your argument, biffvernon, I can see where you are coming from.
I was perturbed when I downloaded the Thermafleece brochure because I could not understand one of the diagrams.
It had a part within the roof structure that I could not place nor imagine what it was. (Thick brown-red thing under battens)
As is so usual it was the exact diagram in which I had interest so I went to the BBA site to download their Agrément Certificate (02/3950) for Thermafleece.
It has a similar diagram but the arrows are pointing at different things so my confusion is not made any easier!
you can download the BBA Cert in pdf form here:
http://www.bbacerts.co.uk/query.idq?CiRestriction=thermafleece&CiScope=%2Fcerts%
However it is very clear that in both the brochure and the BBA 02/3950
This vapour-permeable barrier should be on the side of the tiles.
No if and buts it must be used.
However the BBA Cert also said for insulation (Sarking) next to sloping tiles:
As for fire resistance and any adverse effect it may have I quote:
Now I know more about your argument, biffvernon, I can see where you are coming from.
I was perturbed when I downloaded the Thermafleece brochure because I could not understand one of the diagrams.
It had a part within the roof structure that I could not place nor imagine what it was. (Thick brown-red thing under battens)
As is so usual it was the exact diagram in which I had interest so I went to the BBA site to download their Agrément Certificate (02/3950) for Thermafleece.
It has a similar diagram but the arrows are pointing at different things so my confusion is not made any easier!
you can download the BBA Cert in pdf form here:
http://www.bbacerts.co.uk/query.idq?CiRestriction=thermafleece&CiScope=%2Fcerts%
However it is very clear that in both the brochure and the BBA 02/3950
Brochure said:
Certificate said:
This vapour-permeable barrier should be on the side of the tiles.
No if and buts it must be used.
However the BBA Cert also said for insulation (Sarking) next to sloping tiles:
Which makes it very clear that a vapour barrier of some sort must be used with Thermafleece on the warmer side too.
As for fire resistance and any adverse effect it may have I quote:
and
It is right and proper to investigate the vapour control layer requirement Lime.
I can see why a breather membrane is specified for the cold side. Although I have my doubts as to how breathable these membranes will remain in long term use.
However, the insistence on vapour control on the warm side goes against everything I understand about breathability. Stopping water vapour escaping in one place is surely going to put the problem somewhere else?
If the thermafleece is vapour permeable, a breather membrane is fitted on the cold side and the rafters are suitably ventilated you'd think that any condensation could get out.
I will ask Second Nature tomorrow, and see if I can get some clarification.
It would also be interesting to look into the historic use of insulation. You'd think wool would have neen used in the past to insulate, albeit without the benefit of rot/insect proofing. If wool did cause problems and contribute to rot, it must have become apparent, and likewise if not.
I can see why a breather membrane is specified for the cold side. Although I have my doubts as to how breathable these membranes will remain in long term use.
However, the insistence on vapour control on the warm side goes against everything I understand about breathability. Stopping water vapour escaping in one place is surely going to put the problem somewhere else?
If the thermafleece is vapour permeable, a breather membrane is fitted on the cold side and the rafters are suitably ventilated you'd think that any condensation could get out.
I will ask Second Nature tomorrow, and see if I can get some clarification.
It would also be interesting to look into the historic use of insulation. You'd think wool would have neen used in the past to insulate, albeit without the benefit of rot/insect proofing. If wool did cause problems and contribute to rot, it must have become apparent, and likewise if not.
Nemesis
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I am sure we have had discussion about this in the past, with Middi - wool used as insulation in timber framed buildings.
Rings a bell Nemesis. Although Middi used Celotex boards to insulate his roof, which was beautifully repaired. I can't do it the same way, as I've got a different roof structure and am in a mid terrace.
I'm backing Thermafleece as a solution, but sans vapour control barriers or anything that hamper breathability. The worst case for me would be to have to underboard the ceiling, but I will not be using urethane boards if I can help it.
I'm backing Thermafleece as a solution, but sans vapour control barriers or anything that hamper breathability. The worst case for me would be to have to underboard the ceiling, but I will not be using urethane boards if I can help it.
Nemesis
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I think it was ina historic context, finding wool used in the past as insulation while repairing buildings.
I suspect it's as I said - to pass Building Control regs, they have to asy about the barrier.
I suspect it's as I said - to pass Building Control regs, they have to asy about the barrier.
biffvernon
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You may be asking for trouble, NT, but Ian won't get any if he leaves out the vapour barrier.
The BBA line:
The BBA line:
sounds rather like a standard sentence that gets put in all situations where insulation is involved in the modern non-breathing, put-trickle-vents-in-your-window-frame type of build. It is not appropriate advice for what we are discussing here.
Lime
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I look forward to what you can find out, Ian Bond.
Let us clear a few things up.
When laying Thermafleece between joists in the loft directly on the ceiling below (not between the rafters) no vapour barrier is required.
Consideration has to be given to the fact that insulating the ceiling will result in a cooler loft so the likelyhood of condensation is higher.
They therefore advise that the ventilation is increased if found to be poor.
As usual, care needs to be taken to ensure the Thermafleece does not go right to the ends of the joists directly under the eves. It is here that a space must be kept to allow normal ventilation to occur. In older houses, particularly where a new roof has been put on with a sarking sheet under the tiles, under the eves of the house is the only place ventilation occurs.
When using Thermafleece, either under the roof tiles (sarking) or as a wall insulator for timber frames, a breather membrane should be used on the outer (cold) side and a vapour barrier used on the inside (warm).
In every case it must also be remembered that electric cables need to be derated if within (not merely passing through) the insulation.
I suspect that some people have used this Thermafleece on brick external walls and under tiles without using a vapour barrier. Presumable on the basis that the wall/house/timbers/tiles needs to breath. While I can understand that argument I cannot agree with it.
In my opinion the amount of moisture that will pass through the insulation from the warm inhabited side to the much cooler outer side far exceeds any that may "breath" from the fabric of the building.
It will result in an accumulation of water within the insulation and outside building fabric.
I realise that there is some latent heat effect with Thermafleece when it absorbs water that will increase the temperature within it.
However I think that it is forgotten that a reciprocal loss of water retention is required for this cycle to continue to have any lasting effect.
.....By this I mean that I can't see how all the moisture produced both by the structure and from within the building ever has a chance to be evaporated.
The wool cannot absorb endless moisture, it has to have a mechanism to release/free it.
Where does it go?
added.
Or where does the moisture from the fabric of the house go anyway? .with or without a vapour barrier.......not considering the internal moisture laden air.
Is it being suggested that the wool transfers the moisture from the building (the breathed bit) to the inhabited side and evaporates it there?
How does that work?
Let us clear a few things up.
When laying Thermafleece between joists in the loft directly on the ceiling below (not between the rafters) no vapour barrier is required.
Consideration has to be given to the fact that insulating the ceiling will result in a cooler loft so the likelyhood of condensation is higher.
They therefore advise that the ventilation is increased if found to be poor.
As usual, care needs to be taken to ensure the Thermafleece does not go right to the ends of the joists directly under the eves. It is here that a space must be kept to allow normal ventilation to occur. In older houses, particularly where a new roof has been put on with a sarking sheet under the tiles, under the eves of the house is the only place ventilation occurs.
When using Thermafleece, either under the roof tiles (sarking) or as a wall insulator for timber frames, a breather membrane should be used on the outer (cold) side and a vapour barrier used on the inside (warm).
In every case it must also be remembered that electric cables need to be derated if within (not merely passing through) the insulation.
I suspect that some people have used this Thermafleece on brick external walls and under tiles without using a vapour barrier. Presumable on the basis that the wall/house/timbers/tiles needs to breath. While I can understand that argument I cannot agree with it.
In my opinion the amount of moisture that will pass through the insulation from the warm inhabited side to the much cooler outer side far exceeds any that may "breath" from the fabric of the building.
It will result in an accumulation of water within the insulation and outside building fabric.
I realise that there is some latent heat effect with Thermafleece when it absorbs water that will increase the temperature within it.
However I think that it is forgotten that a reciprocal loss of water retention is required for this cycle to continue to have any lasting effect.
.....By this I mean that I can't see how all the moisture produced both by the structure and from within the building ever has a chance to be evaporated.
The wool cannot absorb endless moisture, it has to have a mechanism to release/free it.
Where does it go?
added.
Or where does the moisture from the fabric of the house go anyway? .with or without a vapour barrier.......not considering the internal moisture laden air.
Is it being suggested that the wool transfers the moisture from the building (the breathed bit) to the inhabited side and evaporates it there?
How does that work?
OK, the question has been put to Second Nature, so lets give them the opportunity to clarify the issues.
Hi,
Please will you help me with the following query regarding Thermafleece Sarking?
I am considering using Thermafleece to insulate between the rafters in an historic stone tiled roof. There is a lath and plaster ceiling attached to the underside of the rafters that I wish to preserve, and do not want to cover or board over.
I intend to put the Thermafleece batts above the ceiling, between the rafters. There will be approximately 2 inches of ventilation space above the insulation to the top of the rafters. A breather membrane will be fitted over the rafters, and the tiles hung from roofing battens. I cannot counterbatten as the roof is mid-terrace.
The breathability of the building's fabric is key to controlling condensation and preventing damp, so Thermafleece's breathability appealed to me over conventional modern urethane board insulation.
Paul Pickett kindly answered some of my questions several months ago, although I have not been able to commence work on my roof as yet.
I have another question that I hope you will be able to answer for me. A statement in the BBA Certificate has been brought to my attention. It's on Page 10 of 12, para 7.5:
7.5 A vapour control layer should be applied to the warm side of the product.
This is causing me some concerns, as vapour barrier seems to conflict with the requirement for breathability. I had hoped that any moisture passing through the lath and plaster ceiling, and through the Thermafleece insulation, would be able to escape via the ventilated rafter space, aided by the breather membrane.
1. The application of a vapour control layer would require me to cover the historic lath and plaster ceiling
2. If the vapour control layer is stopping moisture from escaping via the central part of the roof slope, as currently happens, it will increase levels of condensation elsewhere. The roof would be ventilated at the eaves, but this may not be sufficient.
3. The clause in the BBA certificate appears to imply that without a vapour control layer, the insulation may not be able to disperse water vapour from inside the building quickly enough, and become saturated. This in turn would increase the risk of rot to the roof timbers.
Please will you clarify the requirement for the vapour control layer, where Thermafleece is used in traditional buildings that rely on breathable fabric to control moisture levels.
Many thanks for your help,
Ian Bond
Hi,
Please will you help me with the following query regarding Thermafleece Sarking?
I am considering using Thermafleece to insulate between the rafters in an historic stone tiled roof. There is a lath and plaster ceiling attached to the underside of the rafters that I wish to preserve, and do not want to cover or board over.
I intend to put the Thermafleece batts above the ceiling, between the rafters. There will be approximately 2 inches of ventilation space above the insulation to the top of the rafters. A breather membrane will be fitted over the rafters, and the tiles hung from roofing battens. I cannot counterbatten as the roof is mid-terrace.
The breathability of the building's fabric is key to controlling condensation and preventing damp, so Thermafleece's breathability appealed to me over conventional modern urethane board insulation.
Paul Pickett kindly answered some of my questions several months ago, although I have not been able to commence work on my roof as yet.
I have another question that I hope you will be able to answer for me. A statement in the BBA Certificate has been brought to my attention. It's on Page 10 of 12, para 7.5:
7.5 A vapour control layer should be applied to the warm side of the product.
This is causing me some concerns, as vapour barrier seems to conflict with the requirement for breathability. I had hoped that any moisture passing through the lath and plaster ceiling, and through the Thermafleece insulation, would be able to escape via the ventilated rafter space, aided by the breather membrane.
1. The application of a vapour control layer would require me to cover the historic lath and plaster ceiling
2. If the vapour control layer is stopping moisture from escaping via the central part of the roof slope, as currently happens, it will increase levels of condensation elsewhere. The roof would be ventilated at the eaves, but this may not be sufficient.
3. The clause in the BBA certificate appears to imply that without a vapour control layer, the insulation may not be able to disperse water vapour from inside the building quickly enough, and become saturated. This in turn would increase the risk of rot to the roof timbers.
Please will you clarify the requirement for the vapour control layer, where Thermafleece is used in traditional buildings that rely on breathable fabric to control moisture levels.
Many thanks for your help,
Ian Bond
biffvernon said:
The use of a VB on the warm side has nothing to do with a building being breathable or not. Eaves ventilation addresses that for most of the building, and the permeable membrane for the wool & roof timber. To those for whom it matters I can only suggest looking at why VBs are used on the warm side of roof insulation, then things should be rather clearer.
NT
I have a reply to my questions from Second Nature. They replied within 2 hours.
Good Morning Ian,
Thanks for your email.There are some interesting clauses in BBA certificates, but, unfortunately, the BBA does not consider 'alternative' constructions like yours. Yours is a fairly standard refurb application where account has to be taken of the nature of the existing system and the age of the components where moisture accessability has been provided over many years. As you rightly say to reduce that facility would be to affect the moisture content levels of the fabric and lead to possible deterioration.I am sure that the system as you envisage, ie without a' control' layer will perform as intended and that there is sufficient breathability to accomodate moisture migration out of the system. The ventilation space you intent to use above the insulation and beneath the breather membrane will ensure that adequate air movement takes place and so minimise any condensation risk. The BBA Certification is sometimes contradictory as, no doubt, the certificate for the breather membrane will indicate that it can be used without a 50mm ventilation cavity.(eg Tyvek Supro, Klober Permo Forte, etc.) Many projects like yours have been successfully completed without any air gaps and give no cause for concern. I hope this is of help. Best regards
Paul Pickett
Technical Consultant
Second Nature UK Ltd
Good Morning Ian,
Thanks for your email.There are some interesting clauses in BBA certificates, but, unfortunately, the BBA does not consider 'alternative' constructions like yours. Yours is a fairly standard refurb application where account has to be taken of the nature of the existing system and the age of the components where moisture accessability has been provided over many years. As you rightly say to reduce that facility would be to affect the moisture content levels of the fabric and lead to possible deterioration.I am sure that the system as you envisage, ie without a' control' layer will perform as intended and that there is sufficient breathability to accomodate moisture migration out of the system. The ventilation space you intent to use above the insulation and beneath the breather membrane will ensure that adequate air movement takes place and so minimise any condensation risk. The BBA Certification is sometimes contradictory as, no doubt, the certificate for the breather membrane will indicate that it can be used without a 50mm ventilation cavity.(eg Tyvek Supro, Klober Permo Forte, etc.) Many projects like yours have been successfully completed without any air gaps and give no cause for concern. I hope this is of help. Best regards
Paul Pickett
Technical Consultant
Second Nature UK Ltd
MdB said:
I've just done the calcs for my house based on 50mm sheepswool insulation.
I'd need 66 m^2, which would be a total cost of £503, for 4 packs including VAT and delivery. And I'd have plenty left over from the 4th pack.
That's to insulate the roof slope between the rafters, the backs of the lath walls, and over the 1st floor ceilings at the eaves.
I suppose I could pile up the insulation thicker on top of the ceilings (25 m^2 area), to say 225mm, and get the back of the lath walls up to 100mm.
That puts the price up to £1,253 inc VAT and delivery. I'd probably add to the insulation in the accessible bits in stages.