fixing "naked" celotex to loft rafters to create storage space
David Robinson
layer), and a few bits of hardboard thrown up there for crawling /
limited storage. Well, it did have - most of the glass fibre is pushed
to one end after re-wiring.
I intend to board the whole lot (2400 x 600 22mm T+G chipboard sounds
about right?), keep whatever glass fibre will fit without squashing
under those boards, and attach 50mm celotex to the rafters. I'm not
going for "habitable", but I have a lot of junk, no garage, and soon
no spare room! So I want a not-too-cold / not-too-warm dry storage
area, and I want to keep the main house well insulated overall.
What can I use to fix the celotex to the rafters? (Can't put it
between the rafters - they're only 70mm deep!!!) I've seen long screws
+ washers suggested - what kind of size works and won't crush the
celotex?
I was worried about ventilation, but having been up there, the soffits
let plenty of air through, and it's a windy location. My wonderful
architect suggested lap vents, but he's been wrong about everything
else, so I'm now minded to ignore this suggestion too. Can I just
stick the celotex up and see what happens? There will probably be more
ventilation after I've finished because the glass fibre is/was stuffed
right down at the edges, blocking the (accidental) ventilation at the
soffits. If there are any problems I'll add some vents in the soffits
later.
I'm trying to figure out how to let the air blow across the ridge from
one pitch/elevation to the other - just butting the celotex up to the
ridge will block that air flow. Head height is already a bit limited,
so dropping the celotex below the ridge wouldn't be ideal. I'm not
going to drill holes in the ridge woodwork though - it looks like (and
may well be) the dimensions of a floorboard. Might stick a pipe into
the celotex between each rafter to let the wind blow from one side to
the other without entering the loft. Can anyone think of a less mad
solution?
Cheers,
David.
![george [dicegeorge]'s profile photo](http://lh3.googleusercontent.com/a-/ALV-UjVy3egmWxdo6kgdNwXDn-6EE54MDMuR9kO5wF-DhVhewlzxjNY=s40-c)
george [dicegeorge]
Either the loft is in the heated envelope or it isnt.
I dont think it is in your plan, so it will be very hot in august and
very cold in the winter.
But what of condensation as moist air percolates through the ceilings
below, through the glass fibre, and reaches dewpoint.
Your vapour barrier is on top of this in the celotex, it should be at
the warm side, underneath. Would painting the ceilings with oil paint,
or covering them with vinyl solve this? You wouldnt know the timbers are
getting damp and rotting with condensation because it would be hidden.
Today I glued a kingspan board to the underneath of a plasterboard
ceiling, silver side down. To cover with plasterboard next week perhaps.
[g]
fred
<f31649ac-fbcb-43fd...@j9g2000vbl.googlegroups.com>,
David Robinson <davidr...@postmaster.co.uk> writes
>
>What can I use to fix the celotex to the rafters? (Can't put it
>between the rafters - they're only 70mm deep!!!) I've seen long screws
>+ washers suggested - what kind of size works and won't crush the
>celotex?
>
light washers under the heads and I'm happy with the results. I
tightened them enough to get the screw heads flush but this didn't break
the foil. I bought penny washers in case I wanted to spread the load a
bit more but it turned out not to be necessary.
On the other points it sounds like you have taken a common sense
approach, as you suggest, try it and see. If you want to seal any gaps
then expanding foam dispensed from a proper trade foam gun is ideal, far
more controlled than the disposable cans. Toolstation do one for a
tenner.
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks
Tabby
wrote:
> Currently the loft has about 1ft of glass fibre (old layer + new
> layer), and a few bits of hardboard thrown up there for crawling /
> limited storage. Well, it did have - most of the glass fibre is pushed
> to one end after re-wiring.
>
> I intend to board the whole lot (2400 x 600 22mm T+G chipboard sounds
> about right?),
sounds a bit OTT, half inch is good for a loft.
NT
harry
In the recentish past there has been lots of debate in the
construction world about condensation/ventilation of roof spaces. The
danger is that condensation in the roof space causes rot. Most of it
kicked off with impermeable "felt" being put under roofing tiles/
slates.
So what you have to do is:-
a Prevent warm moist air from getting into your roof spacevoid
adjecent to rafters.
b Provide some ventilation to evaporate any condensation if it does.
There are various ideas on how this might be acheived revovling around
permiable roofing felts, vapour barriers and warm and cold roofs,
special ridge and eves ventilation devices, ventilation tiles. You
really need to get a book from the library & get read up on the
various sytems. theories. (Which change constantly)
I fix my insulation up with a few temporary nails between the rafters.
I leave biggish gaps and fill up with canned foam. It's virtually
impossible to cut this stuff to be a good fit. If there are any air
leaks it just negates thm.
geraldthehamster
wrote:
>
> - Show quoted text -
It seems like an odd plan, if the OP doesn't mind my saying so -
either the loft is a cold space, with insulation between the joists,
or it's a warm space, with insulation between/over the rafters. You
wouldn't normally have both, as there's not a lot of point.
Cheers
Richard
John Rumm
> Currently the loft has about 1ft of glass fibre (old layer + new
> layer), and a few bits of hardboard thrown up there for crawling /
> limited storage. Well, it did have - most of the glass fibre is pushed
> to one end after re-wiring.
>
> I intend to board the whole lot (2400 x 600 22mm T+G chipboard sounds
> about right?), keep whatever glass fibre will fit without squashing
> under those boards, and attach 50mm celotex to the rafters. I'm not
> going for "habitable", but I have a lot of junk, no garage, and soon
> no spare room! So I want a not-too-cold / not-too-warm dry storage
> area, and I want to keep the main house well insulated overall.
>
> What can I use to fix the celotex to the rafters? (Can't put it
> between the rafters - they're only 70mm deep!!!) I've seen long screws
> + washers suggested - what kind of size works and won't crush the
> celotex?
Easiest solution I found, cut 1" wide strips off the end of a sheet of
12mm ply, slap under the foam in line with a rafter and stick a few long
slim screws through the lot.
> I was worried about ventilation, but having been up there, the soffits
> let plenty of air through, and it's a windy location. My wonderful
> architect suggested lap vents, but he's been wrong about everything
> else, so I'm now minded to ignore this suggestion too. Can I just
> stick the celotex up and see what happens? There will probably be more
> ventilation after I've finished because the glass fibre is/was stuffed
> right down at the edges, blocking the (accidental) ventilation at the
> soffits. If there are any problems I'll add some vents in the soffits
> later.
As long as air can get to the timbers behind the insulation you should
be ok. If there is no felt or a breathable felt you are fine. If not
using soffit ventilation and removing a strip of felt near the ridge
should do the trick.
> I'm trying to figure out how to let the air blow across the ridge from
> one pitch/elevation to the other - just butting the celotex up to the
> ridge will block that air flow. Head height is already a bit limited,
> so dropping the celotex below the ridge wouldn't be ideal. I'm not
> going to drill holes in the ridge woodwork though - it looks like (and
> may well be) the dimensions of a floorboard. Might stick a pipe into
> the celotex between each rafter to let the wind blow from one side to
> the other without entering the loft. Can anyone think of a less mad
> solution?
vent each side separately... see above, or add some vent tiles.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Jim K
> It seems like an odd plan, if the OP doesn't mind my saying so -
> either the loft is a cold space, with insulation between the joists,
> or it's a warm space, with insulation between/over the rafters. You
> wouldn't normally have both, as there's not a lot of point.
think of it as an "airlock" between two differing temperature
zones....
Jim K
geraldthehamster
An adequate amount of insulation material *is* an "airlock" between
two differing temperature zones.
Cheers
Richard
David Robinson
> wrote:
> > On 17/11/10 22:33, David Robinson wrote:
>
> > > I intend to board the whole lot (2400 x 600 22mm T+G chipboard sounds
> > > about right?), keep whatever glass fibre will fit without squashing
> > > under those boards, and attach 50mm celotex to the rafters.
> > Either the loft is in the heated envelope or it isnt.
> > I dont think it is in your plan, so it will be very hot in august and
> > very cold in the winter.
> It seems like an odd plan, if the OP doesn't mind my saying so -
No, not at all - I'm posting to get better ideas!
> either the loft is a cold space, with insulation between the joists,
> or it's a warm space, with insulation between/over the rafters. You
> wouldn't normally have both, as there's not a lot of point.
I suppose I don't want all the heat from the house to get up to the
loft and then sit there (it seems a waste, and might make it the
warmest part of the house!), neither do I want none of the heat from
the house to get up there.
In my fuzzy thinking (and maybe someone can think this through
clearly) I want heat from the house to get into the loft at a fairly
slow rate, and the celotex to keep it in there pretty well. Sounds
like it could work during winter, if the relative amounts of
insulation were right.
In summer I'm worried it could all go wrong - i.e. the celotex lets
heat in but then it can't get out. To be fair though, a normal loft
gets pretty hot in summer too. I suppose at the moment some of it
blows out again.
Thinking through the hot / cold areas, and possible condensation, I
was hoping(!) that the loft would be a similar temperature to the main
house (100mm glass fibre below, 50mm celotex above), so avoiding
condensation in the loft itself. The celotex forms a vapour barrier,
and the air above it is very cold, but the moisture from the house
can't get to it.
A very good question is where the moisture that gets into the loft
_goes_ in this scenario. Still, even in the normal scenario of just
celotex on the rafters, where does the moisture from the warm roof go?
Vents in windows in a loft conversion I suppose. How can I vent (a
little!) from the loftm without sending the moisture straight into the
cold roof space, or chilling the loft so it condenses there?
Cheers,
David.
David Robinson
> As long as air can get to the timbers behind the insulation you should
> be ok. If there is no felt or a breathable felt you are fine. If not
> using soffit ventilation and removing a strip of felt near the ridge
> should do the trick.
Standard 1970s felt - presumably not breathable.
I'm worried that if I remove a strip of felt I'll just get things
living/nesting in the space above the celotex. Ridge tiles would be
serious cost and hassle. I see people sell things to poke between
overlapping bits of felt to create ventilation, but doesn't this
encourage pests/insects as well?
Cheers,
David.
David Robinson
harry, I don't have a book, but (on previous advice here) I've read
through all the celotex information which discusses warm and cold
roofs. I'm not taking the tiles off so obviously it'll be a cold roof.
The problem with all the examples I've seen is that I'm not trying
save maximum energy by creating a cold loft, but I'm not trying to
create a habitable space - so don't want to actively heat it, and
won't put windows in.
As you say, theories seem to change constantly, and sometimes be
driven by people trying to sell you things (so I suppose I should get
a source independent from celotex!).
I might take a trip to the library.
Cheers,
David.
David Robinson
wrote:
> Your vapour barrier is on top of this in the celotex, it should be at
> the warm side, underneath.
I'm hoping the loft will be warm-ish too (see other replies).
> Would painting the ceilings with oil paint,
> or covering them with vinyl solve this?
Don't know - sounds like quite a good (but ugly?) idea. Most of the
ceilings are a bit rubbish anyway, though I was hoping to just fill
them rather than replaster.
> You wouldnt know the timbers are
> getting damp and rotting with condensation because it would be hidden.
I'd take a look, both in the summer and winter.
The plasterboard above the bathroom is already foil backed. Not the en
suite though - must do something about that.
> Today I glued a kingspan board to the underneath of a plasterboard
> ceiling, silver side down. To cover with plasterboard next week perhaps.
That's a useful idea, thanks, though the ceilings aren't high as it
is. Wouldn't need much celotex though. Adds extra cost of plastering :-
(
Cheers,
David.
geraldthehamster
wrote:
> I suppose I don't want all the heat from the house to get up to the
> loft and then sit there (it seems a waste, and might make it the
> warmest part of the house!), neither do I want none of the heat from
> the house to get up there.
>
> In my fuzzy thinking (and maybe someone can think this through
> clearly) I want heat from the house to get into the loft at a fairly
> slow rate, and the celotex to keep it in there pretty well. Sounds
> like it could work during winter, if the relative amounts of
> insulation were right.
>
> Thinking through the hot / cold areas, and possible condensation, I
> was hoping(!) that the loft would be a similar temperature to the main
> house (100mm glass fibre below, 50mm celotex above), so avoiding
> condensation in the loft itself. The celotex forms a vapour barrier,
> and the air above it is very cold, but the moisture from the house
> can't get to it.
The above is a little inconsistent - you want some but not all of the
heat from the house to get into the loft, but you want the loft to be
a similar temperature to the main house.
If you want heat to get into the loft, then don't insulate the
ceiling. Some but not all of the heat from the house will get into the
loft, which will still be colder than the house, unless you have
heating installed in the loft. Then I would insulate the rafters with
Celotex or Kingspan, which can be placed between the rafters and also
over them. Use foil-backed and tape any joins. You'll then keep any
moist air in the warmer space of the loft. You'd need to leave ideally
50mm of space between the Celotex and the roofing felt, and ensure
that air could circulate in that gap from the eaves, and idealy also
at the ridge. But I wouldn't do it that way...
>
> A very good question is where the moisture that gets into the loft
> _goes_ in this scenario. Still, even in the normal scenario of just
> celotex on the rafters, where does the moisture from the warm roof go?
> Vents in windows in a loft conversion I suppose. How can I vent (a
> little!) from the loftm without sending the moisture straight into the
> cold roof space, or chilling the loft so it condenses there?
It's not usual to have a warm space that's not habitable, which
usually means it has a window or other vents. In fact there is a
requirement for a habitable space to be ventilated.
In your position, using the loft for storage, I would have my roll
insulation over the ceiling, where you have it now, and keep the loft
a cold space. Most lofts have sufficient draughts that damp shouldn't
be a problem, and I wouldn't have thought cold would damage your
stored items.
Another benefit of this simpler plan is that you will save a lot of
money on Celotex or Kingspan, which isn't cheap.
Cheers
Richard
John Rumm
Insects etc don't really seem to be a problem on Victorian places with
no felt at all.
David Robinson
I appreciate your help, and I can follow your logic - but I've been
into my neighbours house. He's converted the loft into a habitable
space. There's no heating up there. It's consistently the warmest room
of the house, summer or winter. I must remember to ask him if he left
any insulation in. I think it did, but could be wrong.
> Then I would insulate the rafters with
> Celotex or Kingspan, which can be placed between the rafters and also
> over them. Use foil-backed and tape any joins. You'll then keep any
> moist air in the warmer space of the loft. You'd need to leave ideally
> 50mm of space between the Celotex and the roofing felt, and ensure
> that air could circulate in that gap from the eaves, and idealy also
> at the ridge. But I wouldn't do it that way...
It does sound like that could work. The problem is, if it doesn't,
I've got to rip the boards up to put back the insulation I've removed.
Which is tripply painful.
> > A very good question is where the moisture that gets into the loft
> > _goes_ in this scenario. Still, even in the normal scenario of just
> > celotex on the rafters, where does the moisture from the warm roof go?
> > Vents in windows in a loft conversion I suppose. How can I vent (a
> > little!) from the loftm without sending the moisture straight into the
> > cold roof space, or chilling the loft so it condenses there?
>
> It's not usual to have a warm space that's not habitable, which
> usually means it has a window or other vents. In fact there is a
> requirement for a habitable space to be ventilated.
>
> In your position, using the loft for storage, I would have my roll
> insulation over the ceiling, where you have it now, and keep the loft
> a cold space. Most lofts have sufficient draughts that damp shouldn't
> be a problem, and I wouldn't have thought cold would damage your
> stored items.
>
> Another benefit of this simpler plan is that you will save a lot of
> money on Celotex or Kingspan, which isn't cheap.
I'm all for cheaper and simpler. One problem with this is that the
joists are pretty small. Boarding them means knocking the insulation
back to ~100mm from the ~300mm it is now, so the house will be
noticeably colder (and/or more expensive to heat).
The other problem is that plenty of things don't respond well to heat
cycling, or freezing, or summer loft temperatures, or insects nesting.
I don't want to have to think "will this survive being in the loft?"
or "do I need to pack this carefully?" - I want to put things up there
just as I'd put them in a cupboard.
Cheers,
David.
Jim K
er.. yes... so why do you say "there's not a lot of point" then?
Jim K
george [dicegeorge]
> On 18/11/2010 14:14, David Robinson wrote:
>> On Nov 18, 10:55 am, John Rumm<see.my.signat...@nowhere.null> wrote:
>>
>>> As long as air can get to the timbers behind the insulation you should
>>> be ok. If there is no felt or a breathable felt you are fine. If not
>>> using soffit ventilation and removing a strip of felt near the ridge
>>> should do the trick.
>>
>> Standard 1970s felt - presumably not breathable.
>>
>> I'm worried that if I remove a strip of felt I'll just get things
>> living/nesting in the space above the celotex. Ridge tiles would be
>> serious cost and hassle. I see people sell things to poke between
>> overlapping bits of felt to create ventilation, but doesn't this
>> encourage pests/insects as well?
>
> Insects etc don't really seem to be a problem on Victorian places with
> no felt at all.
>
>
You've got to decide where the insulation envelope boundary is,
in three dimensions, I'm putting mine under andor above the ceilings,
There's less area than the slopy roof, and its easier,
and I can check in the loft for leaks.
The loft will be uncomfortably cold for a few months in winter
and hot a few months in summer, but so what?
The book i'm studying is:
Insulate & Weatherize (Taunton's Build Like a Pro) [Paperback]
[g]
george [dicegeorge]
Moist warm air will permeate through the plasterboard ceiling
and fibe glass wool,
and at its dewpoint shed water in the wool.
The ventilation above may dry it, unless there's a layer of celotex on top.
That's the theory, dont know how bad it is in practice.
there should be something about this at
http://wiki.diyfaq.org.uk/index.php?title=Insulation#Insulation_that_doesn.27t_insulate
but i cant find it!
[g]
geraldthehamster
>
> - Show quoted text -
Because you don't need the entire loft to be an "airlock" between two
differing temperature zones, which is what I took you to be saying.
Cheers
Richard
geraldthehamster
wrote:
> On Nov 18, 2:38 pm, geraldthehamster <diy....@hotmail.co.uk> wrote:
> I appreciate your help, and I can follow your logic - but I've been
> into my neighbours house. He's converted the loft into a habitable
> space. There's no heating up there. It's consistently the warmest room
> of the house, summer or winter. I must remember to ask him if he left
> any insulation in. I think it did, but could be wrong.
If it's the warmest room in the house, then there's probably no
insulation between it and the rest of the house.
> > Then I would insulate the rafters with
> > Celotex or Kingspan, which can be placed between the rafters and also
> > over them. Use foil-backed and tape any joins. You'll then keep any
> > moist air in the warmer space of the loft. You'd need to leave ideally
> > 50mm of space between the Celotex and the roofing felt, and ensure
> > that air could circulate in that gap from the eaves, and idealy also
> > at the ridge. But I wouldn't do it that way...
>
> It does sound like that could work. The problem is, if it doesn't,
> I've got to rip the boards up to put back the insulation I've removed.
> Which is tripply painful.
There's no doubt that it would work, it's the standard way of
insulating a loft conversion. The only issue is that ideally you'd
have some way to ventilate the warm loft space, by means of a window,
as you yourself recognised earlier.
> I'm all for cheaper and simpler. One problem with this is that the
> joists are pretty small. Boarding them means knocking the insulation
> back to ~100mm from the ~300mm it is now, so the house will be
> noticeably colder (and/or more expensive to heat).
The usual way to deal with that is to insulate between your joists,
then cross batten and insulate again between the battens. Boarding on
top. That won't give you a structural floor but should be OK for
storage. Alternatively you could use Celotex between the joists
instead of roll stuff, but you're into expense again then.
> The other problem is that plenty of things don't respond well to heat
> cycling, or freezing, or summer loft temperatures, or insects nesting.
> I don't want to have to think "will this survive being in the loft?"
> or "do I need to pack this carefully?" - I want to put things up there
> just as I'd put them in a cupboard.
I've never had trouble storing anything from books to furniture in a
cold ventilated loft for years on end - what is it you want to store?
Anyway, do it whichever way you want - my main point was that you have
a warm loft or a cold loft - you insulate either the rafters or the
joists. if you insulate both, one is redundant.
Cheers
Richard
Jim K
one may not ordinarily "need" it...but it seems the OP wants a "warmer
than average but not as cold as outside" loft area - seems to me he's
on the right track... you seem to be suggesting he's on a wild goose
chase....
Jim K
geraldthehamster
If he wants it warm, it wants to be insulated on the outside (rafters)
and not insulated from the house (joists). That way warm air will rise
into it from the house. But I think that's an expensive option and
unnecessary for storage.
Cheers
Richard
Jim K
and if he wants it somewhere in the middle betwixt house and sky - he
should insulate under the loft floor and under the rafters! ;>)
what's your "either/or" detail based on?
Jim K
David Robinson
> On 18/11/2010 14:14, David Robinson wrote:
>
> > On Nov 18, 10:55 am, John Rumm<see.my.signat...@nowhere.null> wrote:
>
> >> As long as air can get to the timbers behind the insulation you should
> >> be ok. If there is no felt or a breathable felt you are fine. If not
> >> using soffit ventilation and removing a strip of felt near the ridge
> >> should do the trick.
>
> > Standard 1970s felt - presumably not breathable.
>
> > I'm worried that if I remove a strip of felt I'll just get things
> > living/nesting in the space above the celotex. Ridge tiles would be
> > serious cost and hassle. I see people sell things to poke between
> > overlapping bits of felt to create ventilation, but doesn't this
> > encourage pests/insects as well?
>
> Insects etc don't really seem to be a problem on Victorian places with
> no felt at all.
Yes, our previous (1940s) place had no felt, and nothing living in the
loft at all.
This new place (1970s) has felt. Not much in there either. However, in
the 1990s extension (where the felt is more carefully fitted and
overlapped more) there are spiders and a (very small) old wasps nest.
It seems the less air movement there is, the more attracted insects
are. Make me wonder why we have roof felt at all. Just for wind driven
rain/snow I suppose?
Cheers,
David.
Jim K
wrote:
nah it's
1) to allow crap builders to get paid before their crap workmanship
shows up in later years.....
or
2) allow them to choose when to fix the proper roof covering in
reasonable weather having first "waterproofed" the building with
felt...
IME both are equally valid ;>))
Jim K
geraldthehamster
Generally you have a warm living space ventilated by windows and
vents, above which is a vapour barrier and insulation. This ensures
that warm air is kept in the warm space, and any moisture in it is
vented by the above means, and not allowed to condense in the
insulation or timbers above. So if you think about it, it makes little
sense to start stacking insulated warm spaces one above the other.
Instead you usually have a warm zone and a cold zone, completely
separated. An unconverted loft is usually part of the cold zone; a
converted loft is part of the warm zone, and the cold zone is then the
outside.
My points in relation to David's question are these:
1. If the loft is well-ventilated, as most are, cold should not be an
issue affecting storage, so insulate above the rafters.
2. However, if he specifically wants the loft to be warmer, include it
in the warm zone and insulate the rafters, as for a loft conversion.
In neither case is any benefit to be gained by the time and expense of
insulating both.
If I were going for Option 2., I'd want some means of ventilating the
loft, as I think there might otherwise be an issue with mildew on
items stored, especially if the family takes a lot of baths with the
bathroom door open! I'd be tempted to a discreet roof light, on the
back of the roof (you don't want to attract the Council's attention,
as once they start seeing windows appear they might consider you were
getting into the realms of a loft conversion, with attendant Building
Regs requirements).
David, have you considered going the whole hog and converting the loft
to a habitable room? The main requirement beyond insulation would be
bigger floor joists, which aren't hard to DIY. And a staircase, also
DIY-able. You don't say what type of house, or how big the loft, but
it doesn't have to cost the earth if you do a lot yourself, and would
add value to your house. You'd need to put in a Building Notice.
In my last, terraced house, I paid someone to convert the loft before
we moved, specifically to add value. A side benefit, apart from the
extra amenity, was the Velux window at the head of the new staircase,
which brought bright natural sunlight right into an otherwise dark
first floor landing. Took lots of photos and asked questions, then
when I moved to a chalet (now dormer) bungalow, I was confident in
stripping it all out, insulating and plasterboarding myself, leaving
only the dormer construction to a builder, and the plastering to a
plasterer. And put in a new staircase, with a bit of help from a
neighbour who had done it before.
Cheers
Richard
geraldthehamster
>
> - Show quoted text -
A builder told me another reason is to make the house weatherproof
quickly, before the tiles are laid.
Cheers
Richard
David Robinson
> Generally you have a warm living space ventilated by windows and
> vents, above which is a vapour barrier and insulation. This ensures
> that warm air is kept in the warm space, and any moisture in it is
> vented by the above means, and not allowed to condense in the
> insulation or timbers above. So if you think about it, it makes little
> sense to start stacking insulated warm spaces one above the other.
True, but people do in flats, and other areas where they want to keep
sound in or out - because most (not all) kinds of sound insulation
inevitably insulate some heat too.
> Instead you usually have a warm zone and a cold zone, completely
> separated. An unconverted loft is usually part of the cold zone; a
> converted loft is part of the warm zone, and the cold zone is then the
> outside.
>
> My points in relation to David's question are these:
>
> 1. If the loft is well-ventilated, as most are, cold should not be an
> issue affecting storage, so insulate above the rafters.
> 2. However, if he specifically wants the loft to be warmer, include it
> in the warm zone and insulate the rafters, as for a loft conversion.
>
> In neither case is any benefit to be gained by the time and expense of
> insulating both.
>
> If I were going for Option 2., I'd want some means of ventilating the
> loft, as I think there might otherwise be an issue with mildew on
> items stored, especially if the family takes a lot of baths with the
> bathroom door open! I'd be tempted to a discreet roof light, on the
> back of the roof (you don't want to attract the Council's attention,
> as once they start seeing windows appear they might consider you were
> getting into the realms of a loft conversion, with attendant Building
> Regs requirements).
Yes. I think some kind of ventilation to outside (not just to the cold
roof space), designed to keep insects out, would be ideal. Not too
much of course - no point insulating otherwise. I wonder what kind of
thing is available?
It's strange - in all these things we strike a balance - keep heat in
and draughts out - but then let some draughts back in for ventilation.
Old houses seems to have enough ventilation naturally to not worry
about it, while everything we do to new houses makes this a huge
problem! Obviously a loft with carefully taped-up celotex is like a
new house - but doing it carelessly (like an old house) will vent to
the cold roof space, not outside, so cause more problems.
> David, have you considered going the whole hog and converting the loft
> to a habitable room?
Yes, I looked into that - very carefully, since the neighbour did it
somewhat "successfully" (by "cheating" on everything, I suspect). But
the headroom is insufficient already, the joists (at least in the
original house) are pitiful, and adding a staircase would remove a
room. Fundamentally the roof pitch is too shallow to make it work.
I've been through all this ;-)
Cheers,
David.
David Robinson
> quickly, before the tiles are laid.
Yes, yours and Jim's replies make sense. Problem is, I'm sure I've
read some roofing expert say they find people punching/cutting holes
in perfectly good felt to be cringe-worthy - whereas it may be the
obvious thing to do here.
It seems to me that if it's really draughty and cold then insects
aren't so attracted to the space.
Cheers,
David.
Jim K
> vents, above which is a vapour barrier and insulation. This ensures
> that warm air is kept in the warm space, and any moisture in it is
> vented by the above means, and not allowed to condense in the
> insulation or timbers above. So if you think about it, it makes little
> sense to start stacking insulated warm spaces one above the other.
> Instead you usually have a warm zone and a cold zone, completely
> separated. An unconverted loft is usually part of the cold zone; a
> converted loft is part of the warm zone, and the cold zone is then the
> outside.
"generally" maybe
but I still don't see what the issue is with the OP wanting a slightly
warmer loft, and a warmer still house below it?
(ventilation of the roofspace has already been spotted and discussed
earlier in the thread)
> My points in relation to David's question are these:
>
> 1. If the loft is well-ventilated, as most are, cold should not be an
> issue affecting storage, so insulate above the rafters.
do you mean ceiling joists?
> 2. However, if he specifically wants the loft to be warmer, include it
> in the warm zone and insulate the rafters, as for a loft conversion.
>
> In neither case is any benefit to be gained by the time and expense of
> insulating both.
except that the (low ridge) loft would be a bit warmer than it is now
and the heating bill for the house below would not be as big as if (as
you advocate) he ripped all the ceiling joist insulation out as
well ?
Jim K
geraldthehamster
wrote:
> Yes. I think some kind of ventilation to outside (not just to the cold
> roof space), designed to keep insects out, would be ideal. Not too
> much of course - no point insulating otherwise. I wonder what kind of
> thing is available?
>
> It's strange - in all these things we strike a balance - keep heat in
> and draughts out - but then let some draughts back in for ventilation.
I think they key thing is that we do it in a controlled manner. The
first floor space of my dormer bungalow is equivalent to a converted
loft in a two storey house - it's completely insulated and vapour-
barriered all round, with a cold crawl space above the insulated
ceiling.
The cold space is ventilated by vent tiles along the ridge, and by
being continuous with the 50mm air gap between Kingspan and tiles down
the slope of the roof, going down to vents in the soffits.
The ventilation for the rooms below is provided variously by the
trickle vents on the Velux windows on the sloping front room, hit-and-
miss vents in the gable wall, and of course when it's warm we can open
both the Velux windows, and the casement windows in the dormers. But
during a cold night we don't open anything at all.
So the ventilation for the warm habitable space below, and the cold
crawl space above, are completely separate systems.
If you don't want a window, Google for "vent tile" and you might find
something you could replace one or more tiles with. If you're
insulating between/over the rafters, you'd need to leave a gap for the
tile, which I imagine you'd put some kind of frame under, though this
is outside my experience.
How deep are your rafters?
Cheers
Richard
David Robinson
> How deep are your rafters?
70mm (yes, really!) in the original roof, something sensible (about
150mm I think) in the extension.
Cheers,
David.
geraldthehamster
wrote:
Oh, I believe you. Mine were 3x2 inches, so I battened them all out to
6 inches (by screwing more 3x2 on top) to get the requisite amount of
Kingspan in, while leaving an air gap, to satisfy Building Control. 4
inches between and one inch over.
Cheers
Richard
Jim K
of course if the OP really wants a naked finsh - 1" kingspan in
between the 3X2s you had and 4" clean over the top would save a lot of
time (if not expense)?
Jim K
geraldthehamster
>
> - Show quoted text -
Depends how tall he is.
Cheers
Richard
David Robinson
I was just going to put 50mm on the underside.
Cheers,
David.
Jim K
wrote:
> On Nov 20, 7:31 pm, Jim K <jk989...@gmail.com> wrote:
>
>
>
> > On Nov 20, 4:40 pm, geraldthehamster <diy....@hotmail.co.uk> wrote:
>
> > > On Nov 19, 4:32 pm, David Robinson <davidrobin...@postmaster.co.uk>
> > > wrote:
>
> > > > On Nov 19, 1:51 pm, geraldthehamster <diy....@hotmail.co.uk> wrote:
>
> > > > > How deep are your rafters?
>
> > > > 70mm (yes, really!) in the original roof, something sensible (about
> > > > 150mm I think) in the extension.
>
> > > > Cheers,
> > > > David.
>
> > > Oh, I believe you. Mine were 3x2 inches, so I battened them all out to
> > > 6 inches (by screwing more 3x2 on top) to get the requisite amount of
> > > Kingspan in, while leaving an air gap, to satisfy Building Control. 4
> > > inches between and one inch over.
>
> > of course if the OP really wants a naked finsh - 1" kingspan in
> > between the 3X2s you had and 4" clean over the top would save a lot of
> > time (if not expense)?
>
> I was just going to put 50mm on the underside.
>
aye I know ;>)
Jim K
geraldthehamster
wrote:
> On Nov 20, 7:31 pm, Jim K <jk989...@gmail.com> wrote:
>
>
>
>
>
> > On Nov 20, 4:40 pm, geraldthehamster <diy....@hotmail.co.uk> wrote:
>
> > > On Nov 19, 4:32 pm, David Robinson <davidrobin...@postmaster.co.uk>
> > > wrote:
>
> > > > On Nov 19, 1:51 pm, geraldthehamster <diy....@hotmail.co.uk> wrote:
>
> > > > > How deep are your rafters?
>
> > > > 70mm (yes, really!) in the original roof, something sensible (about
> > > > 150mm I think) in the extension.
>
> > > > Cheers,
> > > > David.
>
> > > Oh, I believe you. Mine were 3x2 inches, so I battened them all out to
> > > 6 inches (by screwing more 3x2 on top) to get the requisite amount of
> > > Kingspan in, while leaving an air gap, to satisfy Building Control. 4
> > > inches between and one inch over.
>
> > of course if the OP really wants a naked finsh - 1" kingspan in
> > between the 3X2s you had and 4" clean over the top would save a lot of
> > time (if not expense)?
>
> I was just going to put 50mm on the underside.
>
> Cheers,
>
> - Show quoted text -
I think that'd be quite effective. I only put in as much as I did
because it was a full blown job, inserting dormers and so forth, on a
Building Notice, and the regs required it. Well, that and I was going
to be sleeping there so wanted it as warm as possible.
Regards
Richard
Jim K
how much "over and above Regs" did you put in then?
Jiim K
geraldthehamster
>
> - Show quoted text -
I didn't say I did. I put in the 5 inches that Building Control asked
me to. That was on the dormer cheecks and roofs, and the sloping part
of the wall/ceiling. The flat part of the ceiling with the cold space
overhead got about 18 inches of fibreglass roll insulation, which is
more than required but I had it in the garage.
This was on a BN submitted in 2008. Did someone say here recently that
the required amount of insulation increased again last year?
Cheers
Richard
Jim K
OK! - I only asked as I didn't need 5" Kingspan in my pitched ceiling
as part of a full regs application (2008 ISTR)
> This was on a BN submitted in 2008. Did someone say here recently that
> the required amount of insulation increased again last year?
ISTR they do every year - not that it will bother the OP tho....
Jim K