If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

The Medway Handyman wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what
happens if you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?


Does 18mm chipboard have much insulating ability?
Well I remembered reading at
http://wiki.diyfaq.org.uk/index.php?title=Insulation "that if 6" of
insulation is compressed to 4", it has the insulation value of 4" of
material. In practice the change in size of the trapped air bubbles
means that the value is affected slightly less than this." Seems
plausible but I could well be wrong.
--
R

"The Medway Handyman" wrote in message
m...
If you have a loft with 4" deep joists & 6" deep insulation, what happens
if you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

At a guess the 6” insulation compressed to 4” will be significantly worse
than the 4” alone. The thermal conductivity of glass is around 1 W/mK and
that of air is around 0.025 W/mK, about 40X lower. When you compress the 6”
insulation down to 4” you’ll have 50% more glass and less air than in the
uncompressed 4”. Since the heat is flowing much more in the glass than in
the air – poorer insulation. Insulation is all about having as much air as
possible and as little solid matter, whilst keeping the air still so you don’t
get convection.



Wood has a conductivity of around 0.1 W/mK so you’ll get some insulation,
but it’s not thick enough to contribute a lot.

Norman Billingham wrote:
"The Medway Handyman" wrote in
message m...
If you have a loft with 4" deep joists & 6" deep insulation, what
happens if you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

At a guess the 6" insulation compressed to 4" will be significantly
worse than the 4" alone. The thermal conductivity of glass is around
1 W/mK and that of air is around 0.025 W/mK, about 40X lower. When
you compress the 6" insulation down to 4" you'll have 50% more glass
and less air than in the uncompressed 4". Since the heat is flowing
much more in the glass than in the air - poorer insulation. Insulation is
all about having as much air as possible and as little
solid matter, whilst keeping the air still so you don't get
convection.


Wood has a conductivity of around 0.1 W/mK so you'll get some
insulation, but it's not thick enough to contribute a lot.

Regarding compression of the insulation, I have the same view. Sadly, I
don't know to what extent. How significant do you think significant is!

On Jan 9, 10:24*am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises so you need the most insulation above your heated area.

On Sat, 9 Jan 2010 14:23:14 -0800 (PST), ransley wrote:

On Jan 9, 10:24*am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises so you need the most insulation above your heated area.

Doesn't the fact that the circulation of the heated air is very restricted
by the chipboard on top have any effect? ISTR something in this group about
that.
I know that a v. thin, windproof shell over clothing, even when there's
hardly any wind, makes a lot of difference.
Also, for a small but noticeable difference, a sheet over a duvet is my way
of making a small adjustment without much weight (or effort!) - virtually
no insulating properties but, being fine-weave, slows down the convection.
--
Peter.
2x4 - thick plank; 4x4 - two of 'em.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "The Medway Handyman"
saying something like:

If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Like 4" or less - if it's compressed a lot of the air space out, it's
going to be less useful than 'real' 4".

On Jan 10, 3:02*am, PeterC wrote:
On Sat, 9 Jan 2010 14:23:14 -0800 (PST), ransley wrote:
On Jan 9, 10:24*am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises so you need the most insulation above your heated area.

Doesn't the fact that the circulation of the heated air is very restricted
by the chipboard on top have any effect? ISTR something in this group about
that.
I know that a v. thin, windproof shell over clothing, even when there's
hardly any wind, makes a lot of difference.
Also, for a small but noticeable difference, a sheet over a duvet is my way
of making a small adjustment without much weight (or effort!) - virtually
no insulating properties but, being fine-weave, slows down the convection..
--
Peter.
2x4 - thick plank; 4x4 - two of 'em.- Hide quoted text -

- Show quoted text -

Most everything has been tested for "R" - "U" value, the insulating
value. Here in the US chipboard is wood, google wood insulation
values, I believe depending on type of wood its near the same as
fiberglass per inch. Did you know the colder it gets the less
fiberglasses insulating value is, and air movement can kill it like in
a open breezy attic.

"ransley" wrote in message
...
On Jan 9, 10:24 am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what happens
if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises


Heat does not rise, hot air does.

On Sun, 10 Jan 2010 04:23:58 -0800 (PST), ransley wrote:

On Jan 10, 3:02*am, PeterC wrote:
On Sat, 9 Jan 2010 14:23:14 -0800 (PST), ransley wrote:
On Jan 9, 10:24*am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises so you need the most insulation above your heated area.

Doesn't the fact that the circulation of the heated air is very restricted
by the chipboard on top have any effect? ISTR something in this group about
that.
I know that a v. thin, windproof shell over clothing, even when there's
hardly any wind, makes a lot of difference.
Also, for a small but noticeable difference, a sheet over a duvet is my way
of making a small adjustment without much weight (or effort!) - virtually
no insulating properties but, being fine-weave, slows down the convection.
--
Peter.
2x4 - thick plank; 4x4 - two of 'em.- Hide quoted text -

- Show quoted text -

Most everything has been tested for "R" - "U" value, the insulating
value. Here in the US chipboard is wood, google wood insulation
values, I believe depending on type of wood its near the same as
fiberglass per inch. Did you know the colder it gets the less
fiberglasses insulating value is, and air movement can kill it like in
a open breezy attic.

Well, most lofts are like that. I wondered if keeping that breeze away from
the insulation would make up for the compression.
--
Peter.
2x4 - thick plank; 4x4 - two of 'em.

"PeterC" wrote in message
...
On Sun, 10 Jan 2010 04:23:58 -0800 (PST), ransley wrote:

On Jan 10, 3:02 am, PeterC wrote:
On Sat, 9 Jan 2010 14:23:14 -0800 (PST), ransley wrote:
On Jan 9, 10:24 am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what
happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises so you need the most insulation above your heated area.

Doesn't the fact that the circulation of the heated air is very
restricted
by the chipboard on top have any effect? ISTR something in this group
about
that.
I know that a v. thin, windproof shell over clothing, even when there's
hardly any wind, makes a lot of difference.
Also, for a small but noticeable difference, a sheet over a duvet is my
way
of making a small adjustment without much weight (or effort!) -
virtually
no insulating properties but, being fine-weave, slows down the
convection.
--
Peter.
2x4 - thick plank; 4x4 - two of 'em.- Hide quoted text -

- Show quoted text -

Most everything has been tested for "R" - "U" value, the insulating
value. Here in the US chipboard is wood, google wood insulation
values, I believe depending on type of wood its near the same as
fiberglass per inch. Did you know the colder it gets the less
fiberglasses insulating value is, and air movement can kill it like in
a open breezy attic.

Well, most lofts are like that. I wondered if keeping that breeze away
from
the insulation would make up for the compression.

Having chipboard over the joists will make a difference. Just because it
keeps moving cold air from the insulation. Have rigid foam over the joists
and chipboard over. The cold bridge of the joists is eliminated.

In article ,
PeterC writes:
On Sat, 9 Jan 2010 14:23:14 -0800 (PST), ransley wrote:

On Jan 9, 10:24*am, "The Medway Handyman"
wrote:
If you have a loft with 4" deep joists & 6" deep insulation, what happens if
you board the loft & therefore compress the 6" down to 4"?

Does it still insulate as well as 6" or does it insulate like 4"?

Does 18mm chipboard have much insulating ability?

--
Dave - The Medway Handymanwww.medwayhandyman.co.uk

As others said 6 will be about like 4". But even 6" is only about R
15, im in the US where R 40 is common and R 60 near optimal, Chipboard
might be R 1, not very much at all. Heat loss is mostly up as heat
rises so you need the most insulation above your heated area.

Doesn't the fact that the circulation of the heated air is very restricted
by the chipboard on top have any effect? ISTR something in this group about
that.

You shouldn't put anything impermeable on the top of the fibre-glass
unless there's a moisture barrier under the insulation. It relies on
being ventilated on top to remove the moisture which slowly comes up
through it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]