I recently decided to re-insulate my loft, and and I found that there
was already approx 100mm width of existing insulation between the
ceiling joists. The existing insulation looked quite old, and the
joists were completely boarded over.

As the loft space isn't paticularly useable for storage (it is quite
pokey and the access hatch is tiny), and partly due to laziness, I
decided to lay new insulation (170mm width) over the top of the boards.

My question is:
Should I add another layer of insulation (100mm width) over top of the
170mm layer to bring it up to the recommended width of 270mm, or is
this unecessary due to the presence of the old insulation beneath the
boards, i.e. do layers of insulation need to laid directly on top of
each other for them to be effective?

Cheers,
Rick

The message .com
from contains these words:

My question is:
Should I add another layer of insulation (100mm width) over top of the
170mm layer to bring it up to the recommended width of 270mm

Do layers of insulation need to laid directly on top of
each other for them to be effective?

Yes, and no, in that order.

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

wrote:
I recently decided to re-insulate my loft, and and I found that there
was already approx 100mm width of existing insulation between the
ceiling joists. The existing insulation looked quite old, and the
joists were completely boarded over.

As the loft space isn't paticularly useable for storage (it is quite
pokey and the access hatch is tiny), and partly due to laziness, I
decided to lay new insulation (170mm width) over the top of the boards.

My question is:
Should I add another layer of insulation (100mm width) over top of the
170mm layer to bring it up to the recommended width of 270mm, or is
this unecessary due to the presence of the old insulation beneath the
boards, i.e. do layers of insulation need to laid directly on top of
each other for them to be effective?

Cheers,
Rick

I assume you mean should I add another layer of insulation (170mm thickness)
over the top of the 100mm layer to bring it up to the recommended thickness
of 270mm. I would say yes, and leave the boards where they are.

Sorry, my message was a bit confusing.

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

Should I make it:
270mm (by adding 100mm to 170mm)
Boards
100mm

or is this pointless?

Codswallop wrote:
wrote:
I recently decided to re-insulate my loft, and and I found that there
was already approx 100mm width of existing insulation between the
ceiling joists. The existing insulation looked quite old, and the
joists were completely boarded over.

As the loft space isn't paticularly useable for storage (it is quite
pokey and the access hatch is tiny), and partly due to laziness, I
decided to lay new insulation (170mm width) over the top of the boards.

My question is:
Should I add another layer of insulation (100mm width) over top of the
170mm layer to bring it up to the recommended width of 270mm, or is
this unecessary due to the presence of the old insulation beneath the
boards, i.e. do layers of insulation need to laid directly on top of
each other for them to be effective?

Cheers,
Rick

I assume you mean should I add another layer of insulation (170mm thickness)
over the top of the 100mm layer to bring it up to the recommended thickness
of 270mm. I would say yes, and leave the boards where they are.

wrote:
Sorry, my message was a bit confusing.

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

Should I make it:
270mm (by adding 100mm to 170mm)
Boards
100mm

or is this pointless?

I make that 370mm thickness of insulation. The recommended thickness is
about 250mm, boards or no boards. I don't know whether it is worth having
370mm in the UK.

On 20 Oct 2006 03:45:09 -0700, wrote:

Sorry, my message was a bit confusing.

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

Should I make it:
270mm (by adding 100mm to 170mm)
Boards
100mm

or is this pointless?


Probably. Someone did some nice calculations in here ages ago
illustrating the diminishing returns on more and more insulation.

But to be practical, the stuff is almost given away to the DIYer, and
so, what harm can shoving another layer in cause? It will make you
happy and might cover a deficiency in the existing layers missed so
far.

On 20 Oct 2006 03:45:09 -0700, wrote:

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

270mm of insulation plus the thermal resistance of the boards. No more
insulation is required.

How ever is there a gap between the top of the lower 100mm and the bottom
of the boards? That isn't a good idea as it'll allow air flow and thus
removal of heat. Rather than add another layer of insulation make sure
there is no gap.

--
Cheers
Dave. pam is missing e-mail

In message om, Dave
Liquorice writes
On 20 Oct 2006 03:45:09 -0700, wrote:

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

270mm of insulation plus the thermal resistance of the boards. No more
insulation is required.

How ever is there a gap between the top of the lower 100mm and the bottom
of the boards? That isn't a good idea as it'll allow air flow and thus
removal of heat. Rather than add another layer of insulation make sure
there is no gap.


This is all very well, however I only have room for 100mm of insulation
in the gap between the loft boards and the ceiling. I can't put
insulation on the top of the boards as it's used for storage. So I'm a
bit stuffed as far as the 270mm recommendation goes. I suppose I could
get the inside of the roof sprayed with insulation material, but that
would take too long to pay back.

--
Mike Buckley
RD350LC2 GPZ750 Turbo
http://www.toastyhamster.org
BONY#38

mike. buckley wrote:
In message om, Dave
Liquorice writes
On 20 Oct 2006 03:45:09 -0700, wrote:

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

270mm of insulation plus the thermal resistance of the boards. No more
insulation is required.

How ever is there a gap between the top of the lower 100mm and the bottom
of the boards? That isn't a good idea as it'll allow air flow and thus
removal of heat. Rather than add another layer of insulation make sure
there is no gap.


This is all very well, however I only have room for 100mm of insulation
in the gap between the loft boards and the ceiling. I can't put
insulation on the top of the boards as it's used for storage. So I'm a
bit stuffed as far as the 270mm recommendation goes. I suppose I could
get the inside of the roof sprayed with insulation material, but that
would take too long to pay back.


wont work on a vented roof anyway.

several options

1/. use 100mm of kingspan etc under boards. Best although the joists
will bridge it.

2/. remove borads and lay some 170mm joists across existing, fill with
more rockwool amd reboard..

3/. Lay polystyrene floor slabs (or celotex) over the boards and put
storage on top of that.

The Natural Philosopher wrote:
mike. buckley wrote:
In message om, Dave
Liquorice writes
On 20 Oct 2006 03:45:09 -0700, wrote:

I have already added 170mm on top of the boards.
So the current situation in terms of layers is (from top to bottom):

170mm
Boards
100mm

270mm of insulation plus the thermal resistance of the boards. No more
insulation is required.

How ever is there a gap between the top of the lower 100mm and the bottom
of the boards? That isn't a good idea as it'll allow air flow and thus
removal of heat. Rather than add another layer of insulation make sure
there is no gap.


This is all very well, however I only have room for 100mm of insulation
in the gap between the loft boards and the ceiling. I can't put
insulation on the top of the boards as it's used for storage. So I'm a
bit stuffed as far as the 270mm recommendation goes. I suppose I could
get the inside of the roof sprayed with insulation material, but that
would take too long to pay back.


wont work on a vented roof anyway.

several options

1/. use 100mm of kingspan etc under boards. Best although the joists
will bridge it.

2/. remove borads and lay some 170mm joists across existing, fill with
more rockwool amd reboard..

3/. Lay polystyrene floor slabs (or celotex) over the boards and put
storage on top of that.

And failing that........

We're getting extra Rockwool laid over the existing rockwool and
joists. (Free! due to my daughter getting disability living
allowance).

They want the loft emptied and the boards removed before they start.

The salesman's suggestion with regard to storage was to put some
lengths of 2x2 or 3x2 crossways over the joists on top of the new
insulation, and then put the boards down on top of them.

What does the team thnk of this idea?

The message om
from contains these words:

The salesman's suggestion with regard to storage was to put some
lengths of 2x2 or 3x2 crossways over the joists on top of the new
insulation, and then put the boards down on top of them.

What does the team thnk of this idea?

It's exctly what I did in the same situation. Only I used 4x2 'cos that
was the lift I needed.

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

The message
from Guy King contains these words:

The salesman's suggestion with regard to storage was to put some
lengths of 2x2 or 3x2 crossways over the joists on top of the new
insulation, and then put the boards down on top of them.

What does the team thnk of this idea?

It's exctly what I did in the same situation. Only I used 4x2 'cos that
was the lift I needed.

New timbers on top of the insulation? Or on top of the original joists
with the insulation between the new timbers?

--
Roger Chapman

The message
from Roger contains these words:

New timbers on top of the insulation? Or on top of the original joists
with the insulation between the new timbers?

Right angles to the old timbers. I had to split the new insulation to
make space for them but in most cases it conicided (not surprisingly!)
with an existing split.

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

On 20 Oct 2006 08:14:08 -0700, wrote:

The salesman's suggestion with regard to storage was to put some
lengths of 2x2 or 3x2 crossways over the joists on top of the new
insulation, and then put the boards down on top of them.

What does the team thnk of this idea?

Not a good one. The crossways timbers will compress the new insulation
not only at the intersects with the ceiling joists but in the spaces as
well. Remove the boards put in the crossways timbers, have the freebie
insulation fitted then board over the top. The height of the crossways
needs to be the same as the nominal thickness of the new insulation.

The fitters will like it if you ensure that the spacing of your crossways
timbers is the same as the width of their insulation rolls.

--
Cheers
Dave. pam is missing e-mail

On 20 Oct 2006 08:14:08 -0700, wrote:

And failing that........

We're getting extra Rockwool laid over the existing rockwool and
joists. (Free! due to my daughter getting disability living
allowance).

They want the loft emptied and the boards removed before they start.

The salesman's suggestion with regard to storage was to put some
lengths of 2x2 or 3x2 crossways over the joists on top of the new
insulation, and then put the boards down on top of them.

What does the team thnk of this idea?

The new insulation shouldn't be squashed down by the boards or
'crossways' or you wont get the insulation you should be.

Guy King wrote:
The message om
from contains these words:

The salesman's suggestion with regard to storage was to put some
lengths of 2x2 or 3x2 crossways over the joists on top of the new
insulation, and then put the boards down on top of them.

What does the team thnk of this idea?

It's exctly what I did in the same situation. Only I used 4x2 'cos that
was the lift I needed.

In the first instance I went for a bit of leteral thinking.............

Layed some insulation batts (rockwool??) 2 or three deep over one of
the other lofts

Mr Collins' voice on
"For he has many"
Mr Collins' voice off
And put boards down on them. Feels a bit like i'm at see when I walk
on them, but they don't seem to compress too much. I managed to get
most of the rarely accessed stuff up there, and managed to haggle with
SWMBO to keep more of my wood pile :=))

I am now wondering whether to do the same sort of thing on a section of
the main loft for the other storage requirements. ie lay batts down
and put the boards on them rather than put down timber bearers to sit
the wood on. Either putting this on top of what the contractors lay,
or moving theirs to the side to make some areas of the loft
ridiculously well insulated and putting it down instead

What does the team think of the merits/demerits of each scheme?

Anyone got any Kingspan/Cellotex that's surplus to requirements??

I'd be after enouth to cover about 64 square foot.

Bad form to reply to my own post I know, but there you are....

Latest update!

The insulation people are coming this afternoon, I have just managed to
get the last of the existing boards down from the loft after emptying
it, and my daughter (she who is in receipt of the disability living
allowance had a fall yesterday and broke her femur :=((((((

House of course was/is in complete chaos due to the contents of the
loft being spread across every horizontal surface.

I think it's going to be a question of getting the insulation put down,
putting the boards down on top of that and putting the junk back
temporarily, and adding some Kingspan type stuff either under or over
over the boards at a later date.

wrote:

Bad form to reply to my own post I know, but there you are....

Latest update!

Just in case anyone is still reading/interested.......

The cowboys - sorry, contacters came at around 5 yesterday and covered
the loft in stiffish rockwool.

Not as firm as the insulation batts I used in the other loft, but
certainly much firmer than the candy floss type stuff i've seen on
rolls before.

They then kindly lifted the boards back up for me and laid them on the
top of the rockwool.

Not ideal, but it will do for now, and I can start the joyous task of
getting the bags of clothes and "special things" boxes back up there a
little later and hopefully restore some order before my daughter gets
back from hospital (if they ever find her a bed!!)