Well, I'm running a sadistic hardware experiment at the moment, running 2
pcs and an ultrasparc in the loft. Despite my long-standing must-do job of
putting insulation in the loft it remains unstarted, so I think now is as
good a time as any. (If I have a burst of energy tonight I will probably
cave in and bring the poor machines back down into the office).

It's a victorian terraced house with standard roof construction (the name
escapes me at the moment, but they're not trusses).

My plan is to install as thick kingspan or celotex between the rafters as I
can get away with, whilst leaving a ventilation gap of 50mm between the
insulation and the sarking/tiles. At the apex I will sacrifice a little
headroom and fix some insulation horizontally so that there is a ventilation
route connecting both sides and all gaps betwen the rafters. At the edges
I'll leave a small gap & install vertical insulation so that there is no
airgap underneath & into the loft, but ventilation is maintained from any
gaps in the soffits up to the rafter ventilation space. Everything will be
sealed as far as is possible.

There are 2 air vents per roof face, about 1m from the apex.

Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the roof)?


--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the roof)?

If there is plenty of soffit ventilation, I think you may just get away with
it, although I suspect some BCOs might want to see ridge vents.

Shame you've got sarking, though! Without it, you could fully fill the
rafters and just put in breathable membrane next time the tiles/slates need
changing.

Christian.

"Christian McArdle" wrote in message
t...
Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the
roof)?

If there is plenty of soffit ventilation, I think you may just get away
with
it, although I suspect some BCOs might want to see ridge vents.

Shame you've got sarking, though! Without it, you could fully fill the
rafters and just put in breathable membrane next time the tiles/slates
need
changing.



hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over all
the rafters) - the kind that is reinforced with an internal mesh.

There's no requirement for BCO involvement in this is there? It isn't a
loft conversion, just a boarded loft. Well, at the moment, but if it does
get converted that'll obviously require the whole Building Control
enchilada.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"RichardS" wrote in message
...
"Christian McArdle" wrote in message
t...
Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the
roof)?

If there is plenty of soffit ventilation, I think you may just get away
with
it, although I suspect some BCOs might want to see ridge vents.

Shame you've got sarking, though! Without it, you could fully fill the
rafters and just put in breathable membrane next time the tiles/slates
need
changing.



hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over all
the rafters) - the kind that is reinforced with an internal mesh.

There's no requirement for BCO involvement in this is there? It isn't a
loft conversion, just a boarded loft. Well, at the moment, but if it does
get converted that'll obviously require the whole Building Control
enchilada.


Actually, I've just had another thought.

I'd been wondering how I would hold the insulation between the rafters. It
strikes me that if I get another lot of kingspan/celotex of about 20mm
thickness (if the cost doesnt prove prohibitive), then I can install that
over the top of the rafters (well, on the underside - ie on the loft-space
side) and that would hold the between-rafter stuff in place. As well as
giving me a nice ledge near the apex that the top horizontal insulation can
sit on & a nice smooth internal finish to the whole loft. Are there any
vapour-condensation issues for cold roof rafters so-covered?

That'd also give me 40% extra insulation (there will only be space for 50mm
of insulation between the rafters - I've just measured it).

I'm sure they won't be, but insulation products such as this damned well
ought to be VAT zero rated.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over all
the rafters) - the kind that is reinforced with an internal mesh.

Yes. It is this stuff (which would not be original) that prevents you fully
filling. That's unless you can read the make and it happens to be a
breathable membrane.

There's no requirement for BCO involvement in this is there?

Probably not. I just mean that there might be some difference in opinion on
whether soffit ventilation is sufficient for an apex roof. It may be
particularly troublesome if there is a rear "extension" with a valley join,
as is common on Victorian houses, as there will be no through ventilation on
those sections, particularly on the rear apex section between valley and
ridge.

Christian.

"Christian McArdle" wrote in message
t...
hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over
all
the rafters) - the kind that is reinforced with an internal mesh.

Yes. It is this stuff (which would not be original) that prevents you
fully
filling. That's unless you can read the make and it happens to be a
breathable membrane.

There's no requirement for BCO involvement in this is there?

Probably not. I just mean that there might be some difference in opinion
on
whether soffit ventilation is sufficient for an apex roof. It may be
particularly troublesome if there is a rear "extension" with a valley
join,
as is common on Victorian houses, as there will be no through ventilation
on
those sections, particularly on the rear apex section between valley and
ridge.



just had to go up and recheck that! you reminded me that there is an
extension (from where I am typing at this very moment, so can't very well
forget it!) but the construction of the house is such that the apex of this
extension is substantially lower than the main roof apex, which also means
that I am presented by a complete sloping face of the roof on that corner,
with no access into the extension roof.

I'm actually beginning to look forward to doing this job now.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

I'd been wondering how I would hold the insulation between the rafters.
It
strikes me that if I get another lot of kingspan/celotex of about 20mm
thickness (if the cost doesnt prove prohibitive), then I can install that
over the top of the rafters (well, on the underside - ie on the loft-space
side)

Indeed. Doing so is strongly recommended, and verging on the compulsory for
new build/loft conversions. Keep the lower layer of insulation at or below
the thickness up the upper layer to avoid condensation issues. I would put
50mm between and 50mm underneath. Ensure that the top layer is foil covered
to give a reflective surface for radiated heat from the tiles (you'll
probably find that the boards come fully foiled anyway).

Note that you should cover the entire lot in 12.5mm plasterboard. This not
only provides an aesthetically pleased surface, but has other benefits, such
as making the space lighter and providing much needed fire protection to the
insulation.

Are there any vapour-condensation issues for cold roof rafters so-covered?

Your proposed solution is OK for condensation, provided the roof timbers are
ventilated to the cold space. This is why you must leave the 50mm gap. If
you had no membrane, or it was breathable, you could fully fill the cavity
and assume that the timber is still ventilated through its upper surface to
the tiles/slates.

Christian.

but the construction of the house is such that the apex of this
extension is substantially lower than the main roof apex, which
also means that I am presented by a complete sloping face of the
roof on that corner, with no access into the extension roof.

Yes, some have a valley join, whilst some have lower floors and ceilings in
the "extension" to avoid the expensive roofing shenanigans required. Mine is
definately the former, whilst my mum's house has the latter.

Christian.

"RichardS" wrote in message
...

Well, I'm running a sadistic hardware experiment at the moment, running 2
pcs and an ultrasparc in the loft. Despite my long-standing must-do job
of
putting insulation in the loft it remains unstarted, so I think now is as
good a time as any. (If I have a burst of energy tonight I will probably
cave in and bring the poor machines back down into the office).

It's a victorian terraced house with standard roof construction (the name
escapes me at the moment, but they're not trusses).

My plan is to install as thick kingspan or celotex between the rafters as
I
can get away with, whilst leaving a ventilation gap of 50mm between the
insulation and the sarking/tiles. At the apex I will sacrifice a little
headroom and fix some insulation horizontally so that there is a
ventilation
route connecting both sides and all gaps betwen the rafters. At the edges
I'll leave a small gap & install vertical insulation so that there is no
airgap underneath & into the loft, but ventilation is maintained from any
gaps in the soffits up to the rafter ventilation space. Everything will
be
sealed as far as is possible.

There are 2 air vents per roof face, about 1m from the apex.

Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the roof)?

we provided vents for my loft conversion (after some argument with the BCO
who gave way eventually), by pushing pieces of treated timber roof battens
between the layers where one sheet of roofing felt/sarking overlays the next
and stapling in place. this opens up a ventilation gap between the two
layers. You have to ensure the piece of wood isn't so long that it emerges
from beneath the edge of the top layer (otherwise it may get wet and rot).


--
Bob Mannix

"Christian McArdle" wrote in message
t...
I'd been wondering how I would hold the insulation between the rafters.
It
strikes me that if I get another lot of kingspan/celotex of about 20mm
thickness (if the cost doesnt prove prohibitive), then I can install
that
over the top of the rafters (well, on the underside - ie on the
loft-space
side)

Indeed. Doing so is strongly recommended, and verging on the compulsory
for
new build/loft conversions. Keep the lower layer of insulation at or below
the thickness up the upper layer to avoid condensation issues. I would put
50mm between and 50mm underneath. Ensure that the top layer is foil
covered
to give a reflective surface for radiated heat from the tiles (you'll
probably find that the boards come fully foiled anyway).

Note that you should cover the entire lot in 12.5mm plasterboard. This not
only provides an aesthetically pleased surface, but has other benefits,
such
as making the space lighter and providing much needed fire protection to
the
insulation.

snip

Thanks, Christian. After reading the Kingspan K7 product pdf it seems that
the 12.5mm plasterboard can be substituted by Thermawall TW56 zero ODB
boards, which would solve the vapour barrier issues and fire protection
requirements & provide me with that extra insulation in one go.

Loads of diagrams on that pdf, and that's just confirmed all that you've
said.

Of course I haven't got around to pricing this lot up yet, so plans may well
change!!

Now, if I can just convince my wife that this is hell of a lot better
solution than one of those bloody silly portable air conditioners that she
wants at the moment, then I'm onto a winner all round.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

On Tue, 21 Jun 2005 16:07:58 +0100, "RichardS"
wrote:


"RichardS" wrote in message
...
"Christian McArdle" wrote in message
t...
Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the
roof)?

If there is plenty of soffit ventilation, I think you may just get away
with
it, although I suspect some BCOs might want to see ridge vents.

Shame you've got sarking, though! Without it, you could fully fill the
rafters and just put in breathable membrane next time the tiles/slates
need
changing.



hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over all
the rafters) - the kind that is reinforced with an internal mesh.

There's no requirement for BCO involvement in this is there?

No, just invite Tony round for professional consultation....


It isn't a
loft conversion, just a boarded loft. Well, at the moment, but if it does
get converted that'll obviously require the whole Building Control
enchilada.


Actually, I've just had another thought.

I'd been wondering how I would hold the insulation between the rafters. It
strikes me that if I get another lot of kingspan/celotex of about 20mm
thickness (if the cost doesnt prove prohibitive), then I can install that
over the top of the rafters (well, on the underside - ie on the loft-space
side) and that would hold the between-rafter stuff in place. As well as
giving me a nice ledge near the apex that the top horizontal insulation can
sit on & a nice smooth internal finish to the whole loft. Are there any
vapour-condensation issues for cold roof rafters so-covered?

This is one of the Celotex recipes - i.e. some insulation between the
rafters and some on top.



That'd also give me 40% extra insulation (there will only be space for 50mm
of insulation between the rafters - I've just measured it).

I'm sure they won't be, but insulation products such as this damned well
ought to be VAT zero rated.

But isn't this to create a "computer facility" for your servers?

A reasonable business expense, I think.



--

..andy

To email, substitute .nospam with .gl

The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

"Andy Hall" wrote in message
...
On Tue, 21 Jun 2005 16:07:58 +0100, "RichardS"
wrote:



snip



That'd also give me 40% extra insulation (there will only be space for
50mm
of insulation between the rafters - I've just measured it).

I'm sure they won't be, but insulation products such as this damned well
ought to be VAT zero rated.

But isn't this to create a "computer facility" for your servers?

A reasonable business expense, I think.

Now that is damned good thinking! I'll run it by my (very cautious)
accountant. Just as long as it couldn't have any business-rates
implications (it shouldn't have - the loft remains very much shared use, as
do all other rooms in the house).

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

RichardS wrote:

Of course I haven't got around to pricing this lot up yet, so plans may well
change!!

Although everyone talks about Kingspan and Celotex, you will often find
if you look for other less well known brands (and seconds rather than A1
sheets for that matter) you can reduce the price to under a third.

At Jewson prices for Celotex, I was looking at 2 to 2.5k for the
insulation for my loft conversion. A local firm did Ecotherm sheets to
the same spec for 700 all in.

--
Cheers,

John.

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

"John Rumm" wrote in message
...
RichardS wrote:

Of course I haven't got around to pricing this lot up yet, so plans may
well
change!!

Although everyone talks about Kingspan and Celotex, you will often find
if you look for other less well known brands (and seconds rather than A1
sheets for that matter) you can reduce the price to under a third.

At Jewson prices for Celotex, I was looking at 2 to 2.5k for the
insulation for my loft conversion. A local firm did Ecotherm sheets to
the same spec for 700 all in.



Yes, in fact I was only talking about Kingspan as a well-known brand - would
have investigated Celotex et al and almost certainly the seconds merchants
before buying the stuff.

I'll look up Ecotherm, though. Thanks.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

Christian McArdle wrote:

hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over all
the rafters) - the kind that is reinforced with an internal mesh.


Yes. It is this stuff (which would not be original) that prevents you fully
filling. That's unless you can read the make and it happens to be a
breathable membrane.


There's no requirement for BCO involvement in this is there?


Probably not. I just mean that there might be some difference in opinion on
whether soffit ventilation is sufficient for an apex roof. It may be
particularly troublesome if there is a rear "extension" with a valley join,
as is common on Victorian houses, as there will be no through ventilation on
those sections, particularly on the rear apex section between valley and
ridge.

BCO insisted on it on my roof, and impermeable membrane sarking.

Makes it bloody draughty up there I can tell you - way overkill IMHO.




Christian.

RichardS wrote:

"RichardS" wrote in message
...

"Christian McArdle" wrote in message
. net...

Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the

roof)?

If there is plenty of soffit ventilation, I think you may just get away

with

it, although I suspect some BCOs might want to see ridge vents.

Shame you've got sarking, though! Without it, you could fully fill the
rafters and just put in breathable membrane next time the tiles/slates

need

changing.



hmm, I may have completely the wrong term for this - I can't see the
underside of tiles, there's a plastic membrane underneath them (& over all
the rafters) - the kind that is reinforced with an internal mesh.

There's no requirement for BCO involvement in this is there? It isn't a
loft conversion, just a boarded loft. Well, at the moment, but if it does
get converted that'll obviously require the whole Building Control
enchilada.



Actually, I've just had another thought.

I'd been wondering how I would hold the insulation between the rafters.

Cut it a mill oversize, wedge or use nails, and cover the rafters and
the kingpsan with aluminium tape that the kingspan supplier will sell
you for this very purpose. Obnec bioarded it can't fall down anyway.

You may car3 to fill any small gapos with an acrylic style sealer as well.

It
strikes me that if I get another lot of kingspan/celotex of about 20mm
thickness (if the cost doesnt prove prohibitive), then I can install that
over the top of the rafters (well, on the underside - ie on the loft-space
side) and that would hold the between-rafter stuff in place. As well as
giving me a nice ledge near the apex that the top horizontal insulation can
sit on & a nice smooth internal finish to the whole loft. Are there any
vapour-condensation issues for cold roof rafters so-covered?

The kingspan is foil coated.

That'd also give me 40% extra insulation (there will only be space for 50mm
of insulation between the rafters - I've just measured it).
Do it.

I'm sure they won't be, but insulation products such as this damned well
ought to be VAT zero rated.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

"RichardS" wrote in message
...

Well, I'm running a sadistic hardware experiment at the moment, running 2
pcs and an ultrasparc in the loft. Despite my long-standing must-do job
of
putting insulation in the loft it remains unstarted, so I think now is as
good a time as any. (If I have a burst of energy tonight I will probably
cave in and bring the poor machines back down into the office).

It's a victorian terraced house with standard roof construction (the name
escapes me at the moment, but they're not trusses).

My plan is to install as thick kingspan or celotex between the rafters as
I
can get away with, whilst leaving a ventilation gap of 50mm between the
insulation and the sarking/tiles. At the apex I will sacrifice a little
headroom and fix some insulation horizontally so that there is a
ventilation
route connecting both sides and all gaps betwen the rafters. At the edges
I'll leave a small gap & install vertical insulation so that there is no
airgap underneath & into the loft, but ventilation is maintained from any
gaps in the soffits up to the rafter ventilation space. Everything will
be
sealed as far as is possible.

There are 2 air vents per roof face, about 1m from the apex.

Does anyone see any fault with this plan, and do I need to install any
additional vents (if so, how - I really don't fancy climbing on the roof)?

The best way is to install vent ridge stiles at the apex. About 4 of them.
Install Kingspan in the space between the rafters leaving a 25mm minimum gap
from insulation and the underside of the tiles. Put insulation over the
rafters, then boarding over the insulation right down to the ceiling of the
bedrooms. Seal all this up, so it is air tight. Inside put a small flat
ceiling at the apex about 12" wide with insulation on top of this.

What you have is an air vent from the eves to the ridge tiles. The void at
the apex will allow air between rafters that have no ridge tile above to
flow into the space and out the nearest ridge tile.

Lay a vapour barrier on the loft floor, to prevent water vapour getting to
the loft. At least put a vapour barrier over the wet rooms. Make sure the
hatch is sealed. And have as much insulation on the loft floor as you can.
Board over.

You now have an air tight vented roof, with warm loft.

"RichardS" wrote in message
...
"Andy Hall" wrote in message
...
On Tue, 21 Jun 2005 16:07:58 +0100, "RichardS"
wrote:

snip

I'm sure they won't be, but insulation products such as this damned well
ought to be VAT zero rated.

But isn't this to create a "computer facility" for your servers?

A reasonable business expense, I think.

Now that is damned good thinking! I'll run it by my (very cautious)
accountant. Just as long as it couldn't have any business-rates
implications (it shouldn't have - the loft remains very much shared use,
as
do all other rooms in the house).


Be sure to ask your accountant about the implications of capital-gains-
tax on the (future) sale of a building that's not just only your
principal (sole-use) residence! Remember that accountants tend to
provide an answer to the question you ask - not to the question
you should have asked. Gordon now controls both the Customs (VAT)
but the Revenue (income, and Capital Gains tax (plus others too
numerous to mention).

--

Brian

RichardS wrote:

Yes, in fact I was only talking about Kingspan as a well-known brand - would
have investigated Celotex et al and almost certainly the seconds merchants
before buying the stuff.

I'll look up Ecotherm, though. Thanks.

Do a search through yell.com for insulation wholesalers or simmilar.

I was able to get A1 45mm Cellotex for only £3 / sheet more than
"seconds" from the well known on-line supplier and that included free
delivery.

I bought enough to cover 65m Sq which was about £500 all in IIRC.

GymRatZ wrote:

Do a search through yell.com for insulation wholesalers or simmilar.

I was able to get A1 45mm Cellotex for only £3 / sheet more than
"seconds" from the well known on-line supplier and that included free
delivery.

When I got mine they did not have any seconds available for 50mm sheets,
but the new price was 2 quid extra. However at 14 quid a sheet it was
less than half the celotex price at Jewson.

--
Cheers,

John.

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

John Rumm wrote:

When I got mine they did not have any seconds available for 50mm sheets,
but the new price was 2 quid extra. However at 14 quid a sheet it was
less than half the celotex price at Jewson.

That's because they didn't take of the 45% trade discount or whatever it is.

Around £15 a sheet is what I paid from the local cellotex distributor.
(but they only took cash or cheque)


--
http://gymratz.co.uk - Best Gym Equipment & Bodybuilding Supplements UK.
http://trade-price-supplements.co.uk - TRADE PRICED SUPPLEMENTS for ALL!
http://fitness-equipment-uk.com - UK's No.1 Fitness Equipment Suppliers.
http://gymratz.co.uk/hot-seat.htm - Live web-cam! (sometimes)