Measuring the TOG value of a duvet
pete
to replace the old one than the cost of getting it cleaned.
Anyway, right out of the bag the new duvet didn't appear as good
as the old one. They were both rated at 13.5 TOF, but the new
one was obviously thinner. It wasn't as warm either (even taking
the colder weather into account) and we needed an extra blanket
on top.
Fast forward to this week and we got another cheapo duvet - this
time from Sainsburys, which again is rated at 13.5 TOG and is much
better then the last one we bought (compares well to the original
one). So purely out of interest, I'd like to test if the TOG rating
of the various duvets measures up - has anyone else tried this?
From a DIY perspective, I'm planning on measuring the temp. under
the duvet, while warming the bed with an electric blanket (and having
the room temperature more-or-less constant). The idea is that the
greater the thermal insulation, the higher the under-duvet temperature
will be. The tricky bit will e converting this temperature to a heat-
loss figure and then to a thermal resistance figure.
Any pointers on how to do the sums would be appreciated.
Stuart Noble
Quite fancy a bit of tog testing myself
Gareth
A relative measurement would be quite straight forward, i.e. it will be
easy to compare the two duvets you have bought and see if the
sainsbury's one is better. Doing an accurate measurement will be hard.
A tog is 0.1 m^2K/W. In other words, the thermal resistance in togs is
equal to ten times the temperature difference (in �C) between the two
surfaces of a material, when the flow of heat is equal to one watt per
square metre.
When the temperature under the duvet reaches equilibrium (stops rising)
the heat loss will be equal to the power of the electric blanket, which
I assume you know?. You can easily measure the length and width to work
out the area and you can measure the temperature difference between the
room and under the duvet. What you don't know is how much heat is being
lost through the duvet and how much through the mattress.
You could probably make measurements with one mattress, then the other
and then both and assume the heat loss through the mattress is the same
in all three cases then solve as a set of simultaneous equations to
eliminate the heat loss through the mattress, but I don't suppose you
are really that interested?
--
-----------------------------------------------------------------------
To reply to me directly:
Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris
GB
> Any pointers on how to do the sums would be appreciated.
There are two ways to do this. One is a steady state approach. Wrap a small
(very small) heater in a duvet, wait for the temperature to stabilise, and
measure the temperature drop between the inside and the outside. You need to
measure the voltage drop and amperage of the heater, as well as the surface
area. All rather difficult to do, especially making sure there are no folds
in the duvet around the heater, etc. You'll need a fan to keep the room air
circulating briskly.
Marginally easier is just to wrap a known weight of warm water in a duvet
and plot the temperature drop.
I doubt that you'll get closer than around 50% without cutting the duvet up,
which rather defeats the purpose.
--
Electric cars are very healthy - when the battery runs out you have to
walk home.
Gareth
On 30/01/2010 12:40, Gareth wrote:
>
> On 30/01/2010 10:57, pete wrote:
>> Before xmas we bought a new (cheapo) duvet, as it was cheaper
> You could probably make measurements with one mattress, then the other
> and then both and assume the heat loss through the mattress is the same
> in all three cases then solve as a set of simultaneous equations to
> eliminate the heat loss through the mattress, but I don't suppose you
> are really that interested?
Sorry I meant with one mattress, one duvet, then the same mattress and
the other duvet, then the same mattress and both duvets.
>
Gio
"Gareth" <m...@privacy.net> wrote in message
news:ioGdnc95kchLtfnW...@brightview.com...
>
> On 30/01/2010 10:57, pete wrote:
>> Before xmas we bought a new (cheapo) duvet, as it was cheaper
>> to replace the old one than the cost of getting it cleaned.
>> Anyway, right out of the bag the new duvet didn't appear as good
>> as the old one. They were both rated at 13.5 TOF, but the new
>> one was obviously thinner. It wasn't as warm either (even taking
>> the colder weather into account) and we needed an extra blanket
>> on top.
>> Fast forward to this week and we got another cheapo duvet - this
>> time from Sainsburys, which again is rated at 13.5 TOG and is much
>> better then the last one we bought (compares well to the original
>> one). So purely out of interest, I'd like to test if the TOG rating
>> of the various duvets measures up - has anyone else tried this?
>>
>> Any pointers on how to do the sums would be appreciated.
>
> A relative measurement would be quite straight forward, i.e. it will be
> easy to compare the two duvets you have bought and see if the
> sainsbury's one is better. Doing an accurate measurement will be hard.
>
> A tog is 0.1 m^2K/W. In other words, the thermal resistance in togs is
> equal to ten times the temperature difference (in �C) between the two
> surfaces of a material, when the flow of heat is equal to one watt per
> square metre.
>
> When the temperature under the duvet reaches equilibrium (stops rising)
> the heat loss will be equal to the power of the electric blanket, which
> I assume you know?. You can easily measure the length and width to work
> out the area and you can measure the temperature difference between the
> room and under the duvet. What you don't know is how much heat is being
> lost through the duvet and how much through the mattress.
>
> You could probably make measurements with one mattress, then the other
> and then both and assume the heat loss through the mattress is the same
> in all three cases then solve as a set of simultaneous equations to
> eliminate the heat loss through the mattress, but I don't suppose you
> are really that interested?
>
>
>
>
This will be quite interesting if the OP posts his findings later because it
is something we have often thought about when buying quilt. As the original
poster says there are differences in heat retention between makes offering
the same TOG rating. Alas we have just dismissed the issue in the past when
by rights I suppose we should have directed it towards Trading Standards ?
Gio
geoff
writes
See which the cat prefers
or .. get a life
--
geoff
Owain
> See which the cat prefers
Would the cat prefer the warmer duvet for better self-insulation, or
the cooler duvet because it lets out more human heat?
Owain
geoff
<19947af3-e405-4622...@r19g2000yqb.googlegroups.com>,
Owain <spuorg...@gowanhill.com> writes
--
geoff
Fredxx
"pete" <no-...@unknown.com> wrote in message
news:slrnhm8447...@corv.local...
A way I'd suggest is similar to Gareth's but I think should be more accurate
and should give a direct comparison.
Use an electric blanket on a mattress with the two duvets on top of each
other. It might be an idea to use a third thin duvet or blanket on top to
trap the top temperature probe. Use 3 temperature probes, one on the
electric blanket - 1st duvet interface, second in between the two duvets,
and a third on top the top duvet. You'd have to zero, or correct the
probes, but the temperature across each duvet should be in proportion to the
TOG number. It would be prudent to swap the duvets round and average the
results.
Good luck!
pete
between the duvet and the electric blanket, which was under a sheet:
Old duvet, no duvet cover. Reached equilibrium after 90 minutes at 38.5°C
with cover 49.0
New duvet uncovered 51°C
with cover 56.5
measurements taken in roughly the centre of the electric blanket, with
minimal disturbance, sticking my arm in to take the measurements :-)
The outer surface temp of the old duvet was 23.5°C uncovered,
24.5 covered
For the new duvet uncovered 23.5°C
with duvet cover 22.0
measurements taken with one of the £7 eBay non-contact thermometers from
earlier discussions. (BTW, I bought 2, they both read the same values)
So the big thing is delta-T, which comes out at 15, 24.5, 27.5, 34.5
respectively. The room temperature varied between 18 and 19 degrees during
this time. I'm ignoring this as I reckon it's compensated for by the
measurements of the duvet's outside cover measurements.
I'm also assuming that the transmissivity of the white duvet surface and the
darker duvet cover (for the IR thermometer to make accurate measureemnts) is
roughly constant, too.
The electric blanket measured 125 x 116 cm (1.46m²) and I measured it's
power consumption at 61 Watts. So I'm using a figure of 41.8 Watt/m²
Using the formula from Wiki of TOGS = 10 * delta-T / Watts/m² results in
a TOG rating for the old duvet (sold as 13.5TOG) of 3.6 without a cover
and 5.9 when it's inside a duvet cover. The new one measures at 6.6 and
8.3 respectively.
Now although these numbers appear grossly low, I expect that a lot of the
heat from the electric blanket was dissipated in the matress, so I'm willing
to allow an uncertainty of +100% on that basis - which puts the new duvet
in the right sort of value. However the old one is nowhere near it's advertised
value.
Usenet Nutter
Could it be done with one of those remote thermometers mentioned in
here a few days ago. .a Fiver on Ebay ....could you put the duvet(s)
in turn on top of the mattress with the electric blanket on and point
the thermometer at the duvet(s) and see what the difference in temp
was for each one .
PeterC
As a bit of an aside, I've a 4.5 TOG that's better than a cheap 9 TOG - the
major difference seems to be that the 4 TOG is Hollofill fibre.
I recently bought a 7.5+3.5 TOG combo from Ikea and paid the bit extra for
Hollofill. The 7.5 part is lighter than my old 4.5 and just a bit warmer
(about 15 years between purchases, to 'newer' material?).
--
Peter.
2x4 - thick plank; 4x4 - two of 'em.
John
"PeterC" <giraffe...@homecall.co.uk> wrote in message
news:2j3bex8uvobn$.1dkg95zp8fec0$.dlg@40tude.net...
Do you think the weight and flexibility of the duvet has an effect? If it
moulds itself to your sleeping form it may give the impression of being
warmer than one which leaves gaps down your sides.
Owain
> >Would the cat prefer the warmer duvet for better self-insulation, or
> >the cooler duvet because it lets out more human heat?
> Have you ever met a cat which prefers "cold" ?
No, but which is warmer - wrapping yourself in a blanket or sitting on
top of a radiator? And most cats don't like being *under* duvets.
Owain
Usenet Nutter
But that last bit is probably instinct for self preservation so they
don't feel trapped and can make a swift getaway .I had a cat that used
to burrow under a duvet but only when I was in the bed so presumably
it felt safe enough in that situation.
geoff
<61f61710-b085-4466...@u26g2000yqm.googlegroups.com>,
Owain <spuorg...@gowanhill.com> writes
--
geoff
Dave
Strange animals are cats. A bit like women ;-)
I've got me coat and I'm off.
Dave
PeterC
>> As a bit of an aside, I've a 4.5 TOG that's better than a cheap 9 TOG -
>> the
>> major difference seems to be that the 4 TOG is Hollofill fibre.
>>
>> I recently bought a 7.5+3.5 TOG combo from Ikea and paid the bit extra for
>> Hollofill. The 7.5 part is lighter than my old 4.5 and just a bit warmer
>> (about 15 years between purchases, to 'newer' material?).
>> --
>> Peter.
>> 2x4 - thick plank; 4x4 - two of 'em.
>
> Do you think the weight and flexibility of the duvet has an effect? If it
> moulds itself to your sleeping form it may give the impression of being
> warmer than one which leaves gaps down your sides.
Yes. I have a top sheet (saves on washing a bit) and have to pull in the
bedding (room temperature at ~14C) but did try just the duvet with cover
and it didn't have the cold edges.
Dave
We used to have three different tog value quilts and when we were
heading into winter, would change to a heavier one depending on if Betty
swollocks left the bed and lightened them in the same way when the
weather warmed up in the spring.
Dave
Dave
It makes a tremendous difference. Wife can make a tunnel between us
under the quilt and drag in very cold air when she changes position in
bed. I get round this by hiking up my side of the quilt and dropping it
down between us. When I run out of quilt on my side, I drag some over
from her side and start again.
Dave
Frank Erskine
wrote:
>Strange animals are cats.
I've got a strange animal, but it's a dog...
--
Frank Erskine
Sunderland
Dave
> On Sun, 31 Jan 2010 16:55:58 +0000, Dave <dave...@btopenworld.com>
> wrote:
>
>
>> Strange animals are cats.
>
> I've got a strange animal, but it's a dog...
I can quite happily live with dogs, if my wife could. She hates them,
but I have had a dog around me until I married at the age of 25. And a
few months later, when my father had to go into hospital and left his
dog with us.
Dave
Halmyre
> John wrote:
> > "PeterC" <giraffenos....@homecall.co.uk> wrote in message
Thus provoking shrieks of outrage as you drag cold bits of duvet over
her...
--
Halmyre
ARWadsworth
"geoff" <ra...@kateda.org> wrote in message
news:gMKtyYmu...@demon.co.uk...
Maybe
I fostered a cat for a few months that was resued from a house where the
owners had done a runner and left the cat home alone. The thing was
petrified of soft things such as cushions, duvets, setees etc. It used to
sleep on my bedside cabinet at night.
Adam
Grimly Curmudgeon
drugs began to take hold. I remember Dave <dave...@btopenworld.com>
saying something like:
>It makes a tremendous difference. Wife can make a tunnel between us
>under the quilt and drag in very cold air when she changes position in
>bed. I get round this by hiking up my side of the quilt and dropping it
>down between us. When I run out of quilt on my side, I drag some over
>from her side and start again.
A case for an extra-wide duvet, methinks.
Frank Erskine
Or seperate beds ;-)
--
Frank Erskine
Rod
<>
>
> Separate duvets, certainly, which is the solution we adopted years ago
> due to my wife's habit of rolling the duvet round herself and leaving me
> out in the cold.
>
>
Agreed. And very nice for both of us. (After experience of exactly that
in a hotel in Riga where it seemed to work very well.) But the
difference between down and polyester (of whatever type) is also huge.
Down duvets drape so much better and, somehow, seem to work well across
a much wider range of bedroom temperatures.
--
Rod
Mike Barnes
>But the difference between down and polyester (of whatever type) is
>also huge. Down duvets drape so much better and, somehow, seem to work
>well across a much wider range of bedroom temperatures.
We have a silk-filled duvet, which, although not cheap, seems to combine
the best properties of down and polyester.
--
Mike Barnes
Rod
Bought from China (ebay, I think) - partner used 'make an offer' and got
them at a very much lower price than UK retail - around �40 including
postage for a single.
--
Rod
Thomas Prufer
<grimly...@REMOVEgmail.com> wrote:
>A case for an extra-wide duvet, methinks.
Much better to have an endless duvet that wraps around the bottom of the bed?
Thomas Prufer