[Dave Rowell]

We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25 to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Can anyone hazard an educated guess as to what the likely pay-back time will
be? It's a 3-bed semi, and we're miserly with our heating!
Or is a compromise worth considering? Eg. only upgrading over the new
landing, or only the north-facing side of the roof.

Thanks, Dave

[Doctor Drivel]

"Dave Rowell" wrote in message
...

We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard,

Get them to put "only" high perfroming cellotex in all around. Triso9 is a
con.

The Advertising Standards Authority got them claiming their reflective
insulation is 'Equivalent to 200mm of traditional thick insulation'. A
complaint has been upheld after ASA went to independent technical experts.

The judgement can be seen at:
http://tinyurl.com/s6c2p

DO NOT let them put this stuff in.

and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the
U-value of the roof from 0.25 to
0.15 according to the engineer.
Cost of the upgrade would be £630 - ouch!

Tell them to reassess without the Tiso9 and all cellotex.

Can anyone hazard an educated
guess as to what the likely pay-back time will
be?

Go for the most you can get. Fuel keep on rising in price. Payback is
quick.

[Hugo Nebula]

On Mon, 03 Jul 2006 20:46:05 GMT, a particular chimpanzee named "Dave
Rowell" randomly hit the keyboard and
produced:

We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25 to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Check with your local Building Control about Tri-Iso 9 or 10 (& other
'multi-foil' insulation). There's been a lot of chatter in the last
few weeks about whether they have anywhere near the insulation value
they claim. As a result, my Council has stopped accepting it until
something is resolved.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

[[email protected]]

Dave Rowell wrote:
We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25 to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Can anyone hazard an educated guess as to what the likely pay-back time will
be? It's a 3-bed semi, and we're miserly with our heating!
Or is a compromise worth considering? Eg. only upgrading over the new
landing, or only the north-facing side of the roof.

Thanks, Dave

This sounds very expensive
I have just had 70 mm Kingspan tp10 for 19.99+VAT for a sheet 1200*2400
( althougt I think £23.00 + VAT is nearer the mark.

What I think has probably happened was that your builder went to
sheffield insulations and has quoted retail price which is £46.00+VAT
per sheet. He will get 50% discount on this

Ring Minster Insulations for a proper price for the area you need

HTH Phil

[nafuk]

Dave Rowell wrote:
We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25 to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Can anyone hazard an educated guess as to what the likely pay-back time will
be? It's a 3-bed semi, and we're miserly with our heating!
Or is a compromise worth considering? Eg. only upgrading over the new
landing, or only the north-facing side of the roof.

Thanks, Dave

Ask the architect/builder how many 8' x 4' sheets of Xtratherm or
Kingspan or Celotex (all same product near enough) are required. To do
this properly you need 6" of flexible/on a roll type insulation between
the rafters, then 50 mm celotex under the rafters. You may not have the
depth of rafters or headroom to do this so you will have to go 50mm
celotex between the rafters and 35mm under the rafters. I would advise
to get a breathable roof membrane installed as then you can get away
with a 50mm gap between the insulation and this membrane.
I get 8' x 4' sheets of 50mm celotex for £20 incl vat incl del from
my local builders merchant - had to haggle a bit. Or, look on ebay
(search for insulation).
It the conversion has flat roofing near the roof apex (i.e. a small
loft area) then fill this void with flexible insulation to save money,
or rigid if you want a storage area.

[Doctor Drivel]

"Hugo Nebula" abuse@localhost wrote in message
...
On Mon, 03 Jul 2006 20:46:05 GMT, a particular chimpanzee named "Dave
Rowell" randomly hit the keyboard and
produced:

We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25
to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Check with your local Building Control about Tri-Iso 9 or 10 (& other
'multi-foil' insulation). There's been a lot of chatter in the last
few weeks about whether they have anywhere near the insulation value
they claim. As a result, my Council has stopped accepting it until
something is resolved.

See this:

http://tinyurl.com/s6c2p

[Christian McArdle]

The Advertising Standards Authority got them claiming their reflective
insulation is 'Equivalent to 200mm of traditional thick insulation'. A
complaint has been upheld after ASA went to independent technical experts.

Reading the adjudication shows that it provides no new information. It is
already known that basic u-Values are much worse for it, as it takes no
account of the method of heat transfer resistance used by Triiso type
insulation. This has never been in dispute.

The Tri-iso Super 9/10 insulation works using a completely different method
to Celotex/Kingspan/Rockwool. Methods used to measure conduction of
traditional insulation are not applicable to tri-iso insulation. This is why
BM Trada designed an "as used" type of methodology that measured actual
performance as installed which is valid for any type of insulation, no
matter how it works. The ASA adjudication reads in a very suspect manner.

i.e..

"We acknowledged that BM TRADA Certification was a leading multi-sector
certification body accredited by the United Kingdom Accreditation Service.
We considered that the BM TRADA report did not provide enough detail to
support their methodology instead of the methodology employed by the
internationally recognised ISO industry standards."

It is very clear to me why the ISO industry standards are not applicable and
why a different methodology was required. I can't see why the ASA thought
otherwise. A methodology that actually involves sticking it on a house and
seeing how much heat is required to keep it warm would appear to me very
superior to measuring one aspect of a material's construction in the hope
that there is a linear relationship to energy use. The main reasons that
such a methodology is not normally used is obviously one of cost.

For me, the jury is still out. My loft has been insulated with it (I had
read all the controversy and the BM Trada methodology BEFORE installation).
Right now, the loft temperature is acceptable, especially compared with my
MOL's loft which was insulated conventionally and is currently uninhabitable
due to heat.

When the insulation originally went in (about March), the loft room
immediately became the warmest room in the house despite having no heating
system.

Christian.

[Doctor Drivel]

"Christian McArdle" wrote in message
...

The Advertising Standards Authority got
them claiming their reflective
insulation is 'Equivalent to 200mm
of traditional thick insulation'. A
complaint has been upheld after
ASA went to independent technical experts.

Reading the adjudication shows that
it provides no new information. It is
already known that basic u-Values
are much worse for it, as it takes no
account of the method of heat transfer
resistance used by Triiso type
insulation. This has never been in dispute.

The Tri-iso Super 9/10 insulation works
using a completely different method
to Celotex/Kingspan/Rockwool. Methods
used to measure conduction of
traditional insulation are not applicable to
tri-iso insulation. This is why
BM Trada designed an "as used" type of
methodology that measured actual
performance as installed which is valid for
any type of insulation, no matter how it works.
The ASA adjudication reads in a very suspect manner.

i.e..

"We acknowledged that BM TRADA
Certification was a leading multi-sector
certification body accredited by the United
Kingdom Accreditation Service.
We considered that the BM TRADA report
did not provide enough detail to
support their methodology instead of the
methodology employed by the
internationally recognised ISO industry standards."

It is very clear to me why the ISO industry
standards are not applicable

Read it again!!!! "We considered that the BM TRADA report did not provide
enough detail to support their methodology". Trada did devise a separate
testing method and they don't agree that it is adequate.

For me, the jury is still out.

It doesn't work until proved it does. They claim equiv to 200mm of
Rockwool. Not proven at all.

It is bubble wrap with a layer of foil in a covering of poly. If taped, it
tends to make the place more air-tight giving the impression of superior
insulation.
There is no testing model to explain, which is good enough. After all this
time you would have thought they could have done tests on an Actis Triso9
house and an identical house without Actis with 200mm of insulatiion in
the walls. If there was a clear difference I'm sure they would be crowing
from the rooftops with all data printed and freely given out.

Many people have seen an improvement, although I think more to the air-
tightness the plastic sheeting gives.

There is NO proper independent tests for this stuff. It is not the same as
Rockwool that is clear and reacts differently. So, two identical houses
both air-tight to the same levels, one with 200mm of Rockwool one with
Triso9. Then test the houses using meangfull recorded data. Simple isn't
it? Not one test has been performed.

So, far it is a case of it doesn't work until reliable meaningful
independent test data is produced on houses in cold climates. Triso9 is
"very expensive" bubble wrap, nothing else...until proven otherwise.

[Doctor Drivel]

"Christian McArdle" wrote in message
...

My loft has been insulated with it (I had
read all the controversy and the BM
Trada methodology BEFORE installation).
Right now, the loft temperature is acceptable,
especially compared with my MOL's loft which
was insulated conventionally and is currently
uninhabitable due to heat.

How did you insulated the loft? Put this stuff on the rafters? Above the
floor joists with 25mm air gap?

[Christian McArdle]

How did you insulated the loft? Put this stuff on the rafters? Above the
floor joists with 25mm air gap?

It is under rafters with 25mm cross battening and plasterboard, as
recommended.

Christian.

[Christian McArdle]

It is bubble wrap with a layer of foil in a covering of poly. If taped,
it
tends to make the place more air-tight giving the impression of superior
insulation.

Well, the fact that it is applied in such a manner is actually a selling
point. It is very difficult to cut Celotex/Kingspan and wedge it in without
lots of gaps that promote leakage. Rockwool isn't quite so bad, but a lot of
rigid board installations are badly done, with rough sawn boards with large
gaps, often unfilled with squirty foam.

There is no testing model to explain, which is good enough. After all this
time you would have thought they could have done tests on an Actis Triso9
house and an identical house without Actis with 200mm of insulatiion in
the walls. If there was a clear difference I'm sure they would be crowing
from the rooftops with all data printed and freely given out.

They have. Have you read the BM Trada report? Not the little certificate,
but the one explaining what they did?

So, far it is a case of it doesn't work until reliable meaningful
independent test data is produced on houses in cold climates.

They performed tests in High Wycombe and France. They used the data to
refine their prediction model. Whilst High Wycombe isn't exactly the coldest
place in the country, it is close enough to Reading to give perfectly
acceptable results for my purposes!

BM Trada is not some fly-by-night company giving out certificates for 20
quid and a blow job. They are a very respected company with all the UKAS
certs you can get.

I can't find the details for Super 9 at the moment. However, a similar
methodology was used for the Super 10.

http://www.tri-isosuper10.co.uk/docs...ada%20Cert.pdf

This details how the test chalets were constructed and tested is here and
how the data collected was used to fine tune a model that allowed predictive
comparisons to be made for various weather conditions and locations. The
comparisons were then made for many UK locations to give the average compari
son of 210mm for the Tri-iso Super 10. (My recollection is that Tri-iso
Super 9 had slightly lower performance).

These tests were conducted by a credible and independent testing company on
the premises of that credible and independent testing company.

So, two identical houses both air-tight to the same levels, one with
200mm of Rockwool one with Triso9. Then test the houses using
meangfull recorded data. Simple isn't it?

Very simple. And exactly what they did.

Christian.

[Guy King]

The message ews.net
from "Doctor Drivel" contains these words:

It doesn't work until proved it does.

So for all those years that it was unclear how bumblebees fly[1] they
actually weren't?

[1] Now rather better understood.

--
Skipweasel
Pay no attention to that man behind the curtain.

[Hugo Nebula]

On Tue, 4 Jul 2006 14:52:12 +0100, a particular chimpanzee named
"Christian McArdle" randomly hit
the keyboard and produced:

http://www.tri-isosuper10.co.uk/docs...ada%20Cert.pdf

This details how the test chalets were constructed and tested is here and
how the data collected was used to fine tune a model that allowed predictive
comparisons to be made for various weather conditions and locations. The
comparisons were then made for many UK locations to give the average compari
son of 210mm for the Tri-iso Super 10. (My recollection is that Tri-iso
Super 9 had slightly lower performance).

There is nothing to say what the external conditions where during the
test to maintain the temperature at 23°C. It could have been during a
hot, southern French summer. Likewise the date of the testing in the
UK isn't given, nor is the external weather conditions.

It's probably very easy to maintain a minimal temperature difference
due to the better radiation properties of the material, but I suspect
at greater differences the conductivity has a much more dramatic
effect.

These tests were conducted by a credible and independent testing company on
the premises of that credible and independent testing company.

TRADA apparently don't have UKAS certification to test insulation
products, so their test doesn't count.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

[Doctor Drivel]

"Hugo Nebula" abuse@localhost wrote in message
...
On Tue, 4 Jul 2006 14:52:12 +0100, a particular chimpanzee named
"Christian McArdle" randomly hit
the keyboard and produced:

http://www.tri-isosuper10.co.uk/docs...ada%20Cert.pdf

This details how the test chalets were constructed and tested is here and
how the data collected was used to fine tune a model that allowed
predictive
comparisons to be made for various weather conditions and locations. The
comparisons were then made for many UK locations to give the average
compari
son of 210mm for the Tri-iso Super 10. (My recollection is that Tri-iso
Super 9 had slightly lower performance).

There is nothing to say what the external conditions where during the
test to maintain the temperature at 23°C. It could have been during a
hot, southern French summer. Likewise the date of the testing in the
UK isn't given, nor is the external weather conditions.

It's probably very easy to maintain a minimal temperature difference
due to the better radiation properties of the material, but I suspect
at greater differences the conductivity has a much more dramatic
effect.

These tests were conducted by a credible and independent testing company
on
the premises of that credible and independent testing company.

TRADA apparently don't have UKAS certification to test insulation
products, so their test doesn't count.

The only way to test this stuff is over a period of time with as I have
said, two identical houses next to each other, both air-tight to the same
levels, one with 200mm of Rockwool one with Triso9. Then see how much fuel
they use and measure temperatures at various points around the house either
side of the insulation.

It may do what they are saying, but until proper meaningful tests are
carried out is not the equivalent to 200mm of Riockwool. And it is not
exactly cheap either.

[Dave Rowell]

We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25
to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Can anyone hazard an educated guess as to what the likely pay-back time
will
be? It's a 3-bed semi, and we're miserly with our heating!
Or is a compromise worth considering? Eg. only upgrading over the new
landing, or only the north-facing side of the roof.

Thanks for the info guys.

I'll call Devon CC tomorrow and see if they're accepting Tri-Iso9 at the mo.

The cost of the upgrade includes materials, installation and VAT - they're
charging about £230+VAT for the celotex alone (seems reasonable from ebay
etc), and then 2 man-days labour (seemed a lot, but maybe if it's gotta be
cut careful with no gaps etc .... ??).

Anyway, any thoughts on how to work out a pay-back time for the celotex
addition? 10-20 yrs would do me, but not 30+

Cheers, Dave

[John Rumm]

Doctor Drivel wrote:

There is NO proper independent tests for this stuff.

Funny how this bothers you here, and yet is of no concern when you are
promoting quack descaling devices.

So, far it is a case of it doesn't work until reliable meaningful
independent test data is produced on houses in cold climates.

No, it either works or it doesn't - whether it has been "proven" yet
will not change what it does in reality.

"very expensive" bubble wrap, nothing else...until proven otherwise.

And you are a waste of usenet space until proven otherwise.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

[John Rumm]

nafuk wrote:

I would advise
to get a breathable roof membrane installed as then you can get away
with a 50mm gap between the insulation and this membrane.

You can do that without a breathable membrane so long as you have
sufficient ventilation of the 50mm gap. IIUC you can reduce the gap
further if you do have breathable sarking.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

[Hugo Nebula]

On Tue, 04 Jul 2006 20:42:13 GMT, a particular chimpanzee named "Dave
Rowell" randomly hit the keyboard and
produced:

I'll call Devon CC tomorrow and see if they're accepting Tri-Iso9 at the mo.

And they'll go, "huh?!"

Building Control is looked after by your district council.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

[Doctor Drivel]

"Guy King" wrote in message
...
The message ews.net
from "Doctor Drivel" contains these words:

It doesn't work until proved it does.

So for all those years that it was unclear how bumblebees fly[1] they
actually weren't?

They were flying. We could see them flying.

They say equiv to 200mm of rockwool. That should cascade into energy
used/saved. Not difficult to measure.

[Doctor Drivel]

"John Rumm" aka Essex Chav wrote in message
...
Doctor Drivel wrote:

There is NO proper independent test for this stuff.

Funny how this bothers you here, and yet is of no concern when you are
promoting quack descaling devices.

Chav, what devices might they be?

So, far it is a case of it doesn't work until reliable meaningful
independent test data is produced on houses in cold climates.

No, it either works or it doesn't

Any figures? How does this cascade into energy used or saved?

- whether it has been "proven" yet will not change what it does in
reality.

What does it do in reality?

Boy you are thick! Chavs usually are. He had never heard of the stuff until
he read this thread.

[The Natural Philosopher]

Dave Rowell wrote:
We're having a loft conversion done - work starts tomorrow - and I'm
wondering about upgrading the roof insulation they've specified. They use
TriIso9 as standard, and it could be upgraded by adding 50mm of cellotex
between the rafters . This would reduce the U-value of the roof from 0.25
to
0.15 according to the engineer. Cost of the upgrade would be £630 - ouch!

Can anyone hazard an educated guess as to what the likely pay-back time
will
be? It's a 3-bed semi, and we're miserly with our heating!
Or is a compromise worth considering? Eg. only upgrading over the new
landing, or only the north-facing side of the roof.

Thanks for the info guys.

I'll call Devon CC tomorrow and see if they're accepting Tri-Iso9 at the mo.

The cost of the upgrade includes materials, installation and VAT - they're
charging about £230+VAT for the celotex alone (seems reasonable from ebay
etc), and then 2 man-days labour (seemed a lot, but maybe if it's gotta be
cut careful with no gaps etc .... ??).

Anyway, any thoughts on how to work out a pay-back time for the celotex
addition? 10-20 yrs would do me, but not 30+

Cheers, Dave


Answer is to look at the area covered and start doing sums.

You can assess the heat loss from average inside/outside temps..

If the roof is say 30 sq meters, then heatloss at .15 a compared with
..25 goes from 7.5w per degree C to 4.5W per degree C.

At an overall - say - 10C average temp differential, that's a saving of
30W, or, over a year 262KWh...at at least 4p per Kwh on any energy,
thats about £11 a year :-)

[Doctor Drivel]

"Christian McArdle" wrote in message
...
How did you insulated the loft? Put this stuff on the rafters? Above the
floor joists with 25mm air gap?

It is under rafters with 25mm cross battening and plasterboard, as
recommended.

Is the loft vented? Are the eves vents left intact?

[Doctor Drivel]

"Christian McArdle" wrote in message
...

When the insulation originally went in
(about March), the loft room
immediately became the warmest
room in the house despite having no heating
system.

How does this translate to energy saved/used.

[Christian McArdle]

It is under rafters with 25mm cross battening and plasterboard, as
recommended.

Is the loft vented?

The loft is habitable space and ventilated accordingly.

Are the eves vents left intact?

Above the insulation, from front to rear, there is soffit ventilation, 3
ridge vents supported by cross ventilation at the apex and then ventilation
at the rear of the dormer to the soffit. There is at least 5cm to the
ventilation channels. In addition, the sarking is breathable membrane.

Christian.

[Christian McArdle]

How does this translate to energy saved/used.

Well, the rafters had been insulated with a miserly 25mm of EPS. This had
significantly worse performance as it used to be freezing cold up there.
Clearly the Super 9 is doing something, although I have no figures to make a
proper comparison.

Christian.

[Doctor Drivel]

"Christian McArdle" wrote in message
...
It is under rafters with 25mm cross battening and plasterboard, as
recommended.

Is the loft vented?

The loft is habitable space and ventilated accordingly.

Are the eves vents left intact?

Above the insulation, from front to rear, there is soffit ventilation, 3
ridge vents supported by cross ventilation at the apex and then
ventilation
at the rear of the dormer to the soffit. There is at least 5cm to the
ventilation channels. In addition, the sarking is breathable membrane.

Christian.

So you installed breathable membrane under the tiles and have eves
ventilation that vents up the rafters following the roof slant to the ridge
tiles. I read that only breathable membrane is sufficient as long as the is
an air gap of 25mm; and no eves and ridge ventilation is required. The gaps
between the tiles is enough to take away the water vapour.

[Christian McArdle]

So you installed breathable membrane under the tiles and have eves
ventilation that vents up the rafters following the roof slant to the
ridge
tiles. I read that only breathable membrane is sufficient as long as the
is
an air gap of 25mm; and no eves and ridge ventilation is required. The
gaps
between the tiles is enough to take away the water vapour.

Indeed. The ventilation provided is very belt and braces. Personally, I
wouldn't have bothered with most of the vents and just relied on the
breathable membrane. However, I'm certainly not expecting the wood to rot
away any time soon!

Christian.

[Doctor Drivel]

"Christian McArdle" wrote in message
...

So you installed breathable membrane
under the tiles and have eves
ventilation that vents up the rafters
following the roof slant to the ridge
tiles. I read that only breathable
membrane is sufficient as long as the
is an air gap of 25mm; and no eves
and ridge ventilation is required. The
gaps between the tiles is enough to
take away the water vapour.

Indeed. The ventilation provided is
very belt and braces. Personally, I
wouldn't have bothered with most
of the vents and just relied on the
breathable membrane. However,
I'm certainly not expecting the wood to rot
away any time soon!

It has been proven that the breathable membrane is all that is needed, but
Building Control sill insist on an air flow so the eves ventilation and
ridge tiles have to go in. All they are doing is over cooling the house in
many cases.

If they just accepted the membrane all could be done from inside the loft.
Seal up the eves ventilation gaps into the loft. Rip out existing sarking
with a Stanley knife. Install membrane between rafters stapling and using
tape where needed,. Leave an air gap between underside of tiles and
membrane. Another air gap on the loft side of the membrane and then
insulation and plasterboard. water vapour working its way through the
plasterboard and insulation will work its way through the membrane and out
into the outside air via the gaps in the tiles.

That will work, but I doubt they would allow you to do it. Or will they?

[Christian McArdle]

That will work, but I doubt they would allow you to do it. Or will they?

Well Kingspan say it is OK even without any air gap at all. I don't know if
it was the builder or the BCO who insisted on the vents.

Christian.

[Doctor Drivel]

"Christian McArdle" wrote in message
...
That will work, but I doubt they would allow you to do it. Or will they?

Well Kingspan say it is OK even without any air gap at all. I don't know
if
it was the builder or the BCO who insisted on the vents.

BCO, I'm sure. They like an uninterrupted air path. The cross batons that
the tiles are hung off blocks the flow. The makers of the membranes say it
is not necessary as the water vapour will just float out of the membrane and
through the gaps in the tiles.

[John Rumm]

Doctor Drivel wrote:

It has been proven that the breathable membrane is all that is needed,
but Building Control sill insist on an air flow so the eves ventilation
and ridge tiles have to go in. All they are doing is over cooling the
house in many cases.

Our BCO would have been happy with a breathable membrane and no
additional ventilation.

Rip out existing
sarking with a Stanley knife. Install membrane between rafters stapling
and using tape where needed,.

Personally I would not be happy with replacement sarking installed like
that, since it will defeat one of the benefits of having it in the first
place - i.e. as a secondary weatherproofing layer under the tiles.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/