Loft insulation thickness re joist height
AL_z
Good day,
I am ready to insulate the loft in my 1850-built cottage.The joists in the
loft are about 4" (100mm) deep. I may want to partially board out the loft
at some point in the future. Should I therefore buy loft insulation that is
only 100mm thick? I imagine I could use 150mm thick rockwool, and it would
compress down if necessary, but would there be any point?
The other option (in the interest of maximum insulation) is to forget about
boarding out the loft, and use 100mm or 150mm rockwool between the joists,
then lay large space blankets over the lot. But then, I guess I'd have to
kiss goodbye to any ideas of walking around in the loft, e.g., to use it
for storing stuff, yes?
The loft is very drafty. Is there an easy way to cut down on drafts coming
in between the felt? Or should I not worry about that?
Anyone know if grants are available for loft insulation, and if so, where
to apply?
Many thanks,
Al
![george [dicegeorge]'s profile photo](http://lh3.googleusercontent.com/a-/ALV-UjVy3egmWxdo6kgdNwXDn-6EE54MDMuR9kO5wF-DhVhewlzxjNY=s40-c)
george [dicegeorge]
they will remove any water from leaks or condensation
so your timbers wont rot and your ceiling wont fall in!
There's been lots of discussion of this in the past,
i thinkt hey will advise putting the boards higher
with some kind of spacers so you can have thicker insulation.
energy companies have to save energy, they do this by giving away
insulation cheap.
http://www.moneysavingexpert.com/family/grant-grabbing
[g]
cynic
wrote:
>
> - Show quoted text -
Good advice but if you don't want to add to the height of the joists
you will still gain dramatically over no insulation by adding 4". You
can lay 4" as fill and run another layer crosswise above both base
layer and joists. A different higher performance insulation under the
boarded area might be a way to go
Chris J Dixon
>Good advice but if you don't want to add to the height of the joists
>you will still gain dramatically over no insulation by adding 4". You
>can lay 4" as fill and run another layer crosswise above both base
>layer and joists. A different higher performance insulation under the
>boarded area might be a way to go
I'm planning to top up my already substantial loft insulation
before next winter. The central section is crudely boarded, for
storage, and it was suggested to me that, as the simplest
solution, I could simply get some seconds of Celotex/ Kingspan,
put this on top of the existing boarding, and it would be durable
enough on its own.
Is this likely to be so, I've never walked on any. Any particular
source recommended for a small quantity of cheap insulation
board?
Chris
--
Chris J Dixon Nottingham UK
ch...@cdixon.me.uk
Have dancing shoes, will ceilidh.
NT
2 good options
1. 4" of insulation, boards, then lay down more insulation
2. add more timber to deepen the joists, rather more work.
NT
John Rumm
> cynic wrote:
>
>> Good advice but if you don't want to add to the height of the joists
>> you will still gain dramatically over no insulation by adding 4". You
>> can lay 4" as fill and run another layer crosswise above both base
>> layer and joists. A different higher performance insulation under the
>> boarded area might be a way to go
>
> I'm planning to top up my already substantial loft insulation
> before next winter. The central section is crudely boarded, for
> storage, and it was suggested to me that, as the simplest
> solution, I could simply get some seconds of Celotex/ Kingspan,
> put this on top of the existing boarding, and it would be durable
> enough on its own.
You would be better laying the insulation over the joists[1] and putting
the flooring over that. You can screw the boards down through the
insulation so the whole lot stays in place, and the insulation does not
compress much.
[1] obviously you can have rockwool or similar in the gaps between the
joists.
> Is this likely to be so, I've never walked on any. Any particular
> source recommended for a small quantity of cheap insulation
> board?
You can walk on it - but repeated traffic may scuff the foil finish.
Also any pint loads would push into it if not protected with a layer of
wood over. (even 1/4" ply would be adequate protection in this application)
Where are you in the country?
There is a place near us (SE Essex) that does seconds etc at quite
reasonable prices (you could probably do a whole loft in 2" thick boards
for a couple of hundred)
--
Cheers,
John.
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Chris J Dixon
>On 14/07/2010 19:11, Chris J Dixon wrote:
>> I'm planning to top up my already substantial loft insulation
>> before next winter. The central section is crudely boarded, for
>> storage, and it was suggested to me that, as the simplest
>> solution, I could simply get some seconds of Celotex/ Kingspan,
>> put this on top of the existing boarding, and it would be durable
>> enough on its own.
>
>You would be better laying the insulation over the joists[1] and putting
>the flooring over that. You can screw the boards down through the
>insulation so the whole lot stays in place, and the insulation does not
>compress much.
>
>[1] obviously you can have rockwool or similar in the gaps between the
>joists.
I already have the original glass fibre between the joists, under
the boarding. I was hoping not to have to disturb this.
>
>> Is this likely to be so, I've never walked on any. Any particular
>> source recommended for a small quantity of cheap insulation
>> board?
>
>You can walk on it - but repeated traffic may scuff the foil finish.
>Also any pint loads would push into it if not protected with a layer of
>wood over. (even 1/4" ply would be adequate protection in this application)
>
>Where are you in the country?
>
See my sig.
harry
I have put down two layers of ridgid insulation boards, one between
the joists and another layer on top. I have some chipboard on top to
make a walkway down the centre.
It's quite hard to fit the stuff between the joists as they are often
not parallel and warped too.
I cut the panels an inch too small and filled the gaps with canned
foam. I put the second layer on immediately and weighed it down with
concrete blcks to stop the foam from lifting it. More foam in the
second layer joints afterwards. That way, the foam expanding up from
the first layer joints sticks to the top layer.
I got seconds insulation. They are mostly seconds because they have
large voids in the insulation but the canned foam fills these up real
good. Just poke through the foil & blast way.
I have some brick partition walls poke up through the ceils. I used
off-cuts to carry vertically up these walls a short way to eliminate
the thermal bridge.
This gives the equivalent of 600mm of mineral wool so heat losses tend
to the zero! I have even greater thickness in my outside walls.
harry
>
> I have put down two layers of ridgid insulation boards, one between
> the joists and another layer on top. I have some chipboard on top to
> make a walkway down the centre.
> It's quite hard to fit the stuff between the joists as they are often
> not parallel and warped too.
> I cut the panels an inch too small and filled the gaps with canned
> foam. I put the second layer on immediately and weighed it down with
> concrete blcks to stop the foam from lifting it. More foam in the
> second layer joints afterwards. That way, the foam expanding up from
> the first layer joints sticks to the top layer.
> I got seconds insulation. They are mostly seconds because they have
> large voids in the insulation but the canned foam fills these up real
> good. Just poke through the foil & blast way.
> I have some brick partition walls poke up through the ceils. I used
> off-cuts to carry vertically up these walls a short way to eliminate
> the thermal bridge.
> This gives the equivalent of 600mm of mineral wool so heat losses tend
>
> - Show quoted text -
Oh! Canned foam, you need lots. Cheapest place is "Screwfix" No-
nonsense foam. Even cheaper if you get the bulk packs. I must have
used about 60 or 70 cans.
Andy Burns
> Canned foam, you need lots. I must have used about 60 or 70 cans.
That's several canoes full.
robgraham
Rather than use more timber make up composite beams from OSB and
timber the *width* of your ceiling joists.
I did this recently for a friend. The ceiling timbers were 36mm wide
- the composite beams were 200mm high and the were made so that they
slotted over the existing joists. I used 9mm OSB and in this case the
2 joining timbers were 36 x 30. The flooring was then screwed to the
top of these beams which made it all very stiff - easy to install,
easy on the pocket, easy to make.
I don't think it would be necessary, but you could fill the inside of
the beams with rockwool when making them up.
Rob
george [dicegeorge]
>>
>> You can walk on it - but repeated traffic may scuff the foil finish.
>> Also any pint loads would push into it if not protected with a layer of
>> wood over. (even 1/4" ply would be adequate protection in this application)
>>
or cheaper hardboard, or old carpet.
[g]
george [dicegeorge]
> I have put down two layers of ridgid insulation boards, one between
> the joists and another layer on top. I have some chipboard on top to
> make a walkway down the centre.
> It's quite hard to fit the stuff between the joists as they are often
> not parallel and warped too.
> I cut the panels an inch too small and filled the gaps with canned
> foam. I put the second layer on immediately and weighed it down with
> concrete blcks to stop the foam from lifting it. More foam in the
> second layer joints afterwards. That way, the foam expanding up from
> the first layer joints sticks to the top layer.
> I got seconds insulation. They are mostly seconds because they have
> large voids in the insulation but the canned foam fills these up real
> I have some brick partition walls poke up through the ceils. I used
> off-cuts to carry vertically up these walls a short way to eliminate
> the thermal bridge.
> This gives the equivalent of 600mm of mineral wool so heat losses tend
> to the zero! I have even greater thickness in my outside walls.
>
Isnt there a problem with condensation?
Water vaour percolating through the kingspan then meeting a dewpoint?
They say put a vapour barrier on the warm side,
Would waterproof paint on the ceiling underneath do this?
Or am I worrying unnecessarily?
[g]
george [dicegeorge]
>
> Rather than use more timber make up composite beams from OSB and
> timber the *width* of your ceiling joists.
>
> I did this recently for a friend. The ceiling timbers were 36mm wide
> - the composite beams were 200mm high and the were made so that they
> slotted over the existing joists. I used 9mm OSB and in this case the
> 2 joining timbers were 36 x 30. The flooring was then screwed to the
> top of these beams which made it all very stiff - easy to install,
> easy on the pocket, easy to make.
>
> I don't think it would be necessary, but you could fill the inside of
> the beams with rockwool when making them up.
>
> Rob
sounds good but i dont understand how this saves timber
(maybe cos im a bit slow)
photo or ascii art please?
[g]
NT
wrote:
I'm guessing Rob means that each old joist has added to it 2x OSB
sides, which are fixed together at the top with a strip of 36x30mm
timber. Sounds like a lot more work. If you wanted to simplify that
one could presumably do that on every odd joist, with the even joists
just getting a single sheet of OSB on one side and nothing else.
NT
george [dicegeorge]
original joists?
harry
Yep. I am Screwfix's best customer for canned foam. Volume depends
whether it's released in free space or in a crack/crevice. Use
straight away, the gas leaks out & you get less expansion. I can tell
you everything you need to know about canned foam.
An important one is don't get it on your hands. Sticks like shit to a
blanket. :-)
harry
wrote:
>
> - Show quoted text -
The ridgid foam is closed cell structure so water vapour can't get
in. It can have a foil finish anyway.
george [dicegeorge]
> On 15 July, 08:44, Andy Burns<usenet.aug2...@adslpipe.co.uk> wrote:
>> harry wrote:
>>> Canned foam, you need lots. I must have used about 60 or 70 cans.
>>
>> That's several canoes full.
>
> Yep. I am Screwfix's best customer for canned foam. Volume depends
> whether it's released in free space or in a crack/crevice. Use
> you everything you need to know about canned foam.
> An important one is don't get it on your hands. Sticks like shit to a
> blanket. :-)
its easy to clean shit off a blanket.
[g]
The Natural Philosopher
Foam is spawn of the devil.
Shit is merely distasteful.
NT
wrote:
Indeed... that's true of both versions of course. The whole osb idea
isnt really a bodge that appeals to me, but it should work. You could
add glue fwiw.
NT
george [dicegeorge]
I think kingspan IS permeable,
that's why they have the foil and taping.
Am I right?
Standard cans of foam definitely are open celled,
the closed cell foam is very expensive and hard to find.
[g]
The Natural Philosopher
No. It never got soggy when left outside.I am not sure why its
foiled.Probably to make it easier to tape up.
> Standard cans of foam definitely are open celled,
> the closed cell foam is very expensive and hard to find.
>
Mots foam seems to form an impermeable skin. even if the interior is
relatively open. They do use it in canoes, after all ;-)
> [g]
>
>
harry
wrote:
The foil is part of the isulation thing and also to make it
mechanically stronger. It is very weak without it.
There is an alternative covering that looks like paper (but I don't
think it is). You can plaster straight onto this, it has a rough
finish to key it on.You can also get the slabs with stepped edges. I
find them less usefull.
The canned foam doesn't fill with water even if you submerge it even
for long periods.
m...@privacy.net
harry <harol...@aol.com> wrote:
> An important one is don't get it on your hands. Sticks like shit to a
> blanket. :-)
I've found that cellulose thinner works well to get uncured foam off skin.
This followed an incident where a part used can was dropped, and the can
leaked through the valve after the handle had been knocked off. It could have
been much worse! SWMBO never found out.
--
B Thumbs
Change lycos to yahoo to reply
m...@privacy.net
> No. It never got soggy when left outside.I am not sure why its
> foiled.Probably to make it easier to tape up.
>
Some I had left outside got *very* soggy. you could tell by its weight. Dried
out ok after several months in the garage, but warped. (Foil/paper faced, the
paper shrunk, the foil didn't).
John Rumm
Its worth buying a can of the foam cleaner (basically acetone IIUC).
That removes uncured foam easily with little risk to most surfaces.
robgraham
NT - could you explain why you think this is a 'bodge'. Composite
beams of this type are frequently used in building construction, as
they are light, inexpensive, easy to make, and being a box structure,
incredibly stiff. My gut feeling is that you regard the use of OSB as
the bodge - OK use ply if you must but the industry is quite happy
with OSB for this.
____
II____II
II II
II II
II II
II____II
II____II
IIxxxxII xxxx is existing beam
IIxxxxII
IIxxxxII
terry
The uninsulated attic should be thoroughly ventilated to prevent the
build up of moisture, rot or mould. that doesn't mean that it can't be
used for cold storage.
The code here for example calls for 3 sq feet of attic venting for
each 1000 square feet of area (0.3%) and that it be distributed so as
to permit 'cross ventilation'.
By the same token a 'vapour barrier' is necessary to prevent or
restrict warm moist house air from penetrating into the insulation and
then condensing there making the insulation wet and useless as well as
also causing rot and/or mould.
Suggest some checking on vapour barriers, insulation values, permeable
and impermeable air barriers.
Compressing batts can reduce their insulation value. Extra (2 inch?)
strapping added to the ceiling joists could increase depth for the
insulation, to avoid pounding and nailing of the ceiling the strapping
could be screwed down onto the ceiling joists using a cordless
drill?
NT
If I've understood your diagram right you're using 2 strips of 36x30,
I thought you were just using one along the top. It does seem a lot
more work than solid timber.
NT
robgraham
> > NT - could you explain why you think this is a 'bodge'. Composite
> > beams of this type are frequently used in building construction, as
> > they are light, inexpensive, easy to make, and being a box structure,
> > incredibly stiff. My gut feeling is that you regard the use of OSB as
> > the bodge - OK use ply if you must but the industry is quite happy
> > with OSB for this.
> > ____
> > II____II
> > II II
> > II II
> > II II
> > II____II
> > II____II
> > IIxxxxII xxxx is existing beam
> > IIxxxxII
> > IIxxxxII
>
> If I've understood your diagram right you're using 2 strips of 36x30,
> I thought you were just using one along the top. It does seem a lot
> more work than solid timber.
>
> NT
More work maybe, but how are you going to attach the solid timber ?
The bonus I found was the lightness of this beam and the ease of just
dropping them over the existing timbers, and screwing through.
More preparation work, but dead easy installation.
Rob
NT
> > > NT - could you explain why you think this is a 'bodge'. Composite
> > > beams of this type are frequently used in building construction, as
> > > they are light, inexpensive, easy to make, and being a box structure,
> > > incredibly stiff. My gut feeling is that you regard the use of OSB as
> > > the bodge - OK use ply if you must but the industry is quite happy
> > > with OSB for this.
> > > ____
> > > II____II
> > > II II
> > > II II
> > > II II
> > > II____II
> > > II____II
> > > IIxxxxII xxxx is existing beam
> > > IIxxxxII
> > > IIxxxxII
>
> > If I've understood your diagram right you're using 2 strips of 36x30,
> > I thought you were just using one along the top. It does seem a lot
> > more work than solid timber.
>
> > NT
>
> More work maybe, but how are you going to attach the solid timber ?
glue & screw
> The bonus I found was the lightness of this beam and the ease of just
> dropping them over the existing timbers, and screwing through.
>
> More preparation work, but dead easy installation.
>
> Rob
right
NT
Mike Jones
>
> There is a place near us (SE Essex) that does seconds etc at quite
> reasonable prices (you could probably do a whole loft in 2" thick boards
> for a couple of hundred)
>
Could you say which company this is please John? I'm in that area.
Thanks
Mike
John Rumm
"APCO Wholesale" is the name I have, but not sure how well they
publicise[1] the name as such - but they have a large yard stuffed full
of insulation! New and seconds, and a wide range of sizes. Price for
8x4" sheet of foil faced 50mm board is normally about £12 to £14
(depending on if new/second etc). (seconds are pretty decent to be
fair). They deliver locally or you can go an pickup. Discounts available
for quantity (a LWB hitop van load was about £300 ish last time I ordered).
They are on the A13 in Benfleet, about half way between the bottom of
Bread and Cheese hill and Tarpots. Run by a chap called Andy and his
wife. Number is 07977 914855.
[1] In fact Google would suggest they do these days ;-) :
http://www.apinsulation.co.uk/index.html
Mike Jones
>
> "APCO Wholesale" is the name I have, but not sure how well they
> publicise[1] the name as such - but they have a large yard stuffed full
> of insulation! New and seconds, and a wide range of sizes. Price for
> 8x4" sheet of foil faced 50mm board is normally about £12 to £14
> (depending on if new/second etc). (seconds are pretty decent to be
> fair). They deliver locally or you can go an pickup. Discounts available
> for quantity (a LWB hitop van load was about £300 ish last time I ordered).
>
> They are on the A13 in Benfleet, about half way between the bottom of
> Bread and Cheese hill and Tarpots. Run by a chap called Andy and his
> wife. Number is 07977 914855.
>
>
> [1] In fact Google would suggest they do these days ;-) :
>
> http://www.apinsulation.co.uk/index.html
>
Excellent
Thank You.
geraldthehamster
wrote:
> Standard cans of foam definitely are open celled,
> the closed cell foam is very expensive and hard to find.
Standard expanding foam is open celled. On the other hand, the low
expansion foam for fixing doors and windows is billed as waterproof,
so is, presumably, closed cell. It's not hard to find.
Cheers
Richard