I've just done a heatloss calculation for a small terraced house (3.8m wide
x 7.4m deep x 2.4m each storey with 2.5m x 4m back addition, mix of carpeted
wooden and solid floors, mostly single glazed, 50mm insulation in the roof)
and get just over 6.5kW, which seems very low. I've done the calcs on a
spreadsheet but cross-checked with the Myson calculator for the floor and
air changes of one room, to sanity check.

Does this seem right? I could put it all through the Myson to completely
cross-check it but it's a lot of extra work ...

tia

--
John Stumbles
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-+

On Mon, 5 Jan 2004 19:50:40 -0000, "John Stumbles"
] wrote:

I've just done a heatloss calculation for a small terraced house (3.8m wide
x 7.4m deep x 2.4m each storey with 2.5m x 4m back addition, mix of carpeted
wooden and solid floors, mostly single glazed, 50mm insulation in the roof)
and get just over 6.5kW, which seems very low. I've done the calcs on a
spreadsheet but cross-checked with the Myson calculator for the floor and
air changes of one room, to sanity check.

Does this seem right? I could put it all through the Myson to completely
cross-check it but it's a lot of extra work ...

tia

This seems low to me as well.

Presumably this is an older property with solid walls..??

I would expect the extension to have a fairly large heat loss because
of the external wall area.

How have you treated the party walls?

..


..andy

To email, substitute .nospam with .gl

On Mon, 05 Jan 2004 20:04:34 +0000, Andy Hall wrote:

On Mon, 5 Jan 2004 19:50:40 -0000, "John Stumbles"
] wrote:

I've just done a heatloss calculation for a small terraced house (3.8m wide
x 7.4m deep x 2.4m each storey with 2.5m x 4m back addition, mix of carpeted
wooden and solid floors, mostly single glazed, 50mm insulation in the roof)
and get just over 6.5kW, which seems very low. I've done the calcs on a
spreadsheet but cross-checked with the Myson calculator for the floor and
air changes of one room, to sanity check.

Does this seem right? I could put it all through the Myson to completely
cross-check it but it's a lot of extra work ...

tia

This seems low to me as well.

Presumably this is an older property with solid walls..??

I would expect the extension to have a fairly large heat loss because
of the external wall area.

How have you treated the party walls?

Have you allowed for the air changes?

I'd go high on those to allow for the sash windows.

Anyone know of a small output condensing model?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"Andy Hall" wrote in message
...
On Mon, 5 Jan 2004 19:50:40 -0000, "John Stumbles"
] wrote:

I've just done a heatloss calculation for a small terraced house (3.8m
wide
x 7.4m deep x 2.4m each storey with 2.5m x 4m back addition, mix of
carpeted
wooden and solid floors, mostly single glazed, 50mm insulation in the
roof)
and get just over 6.5kW, which seems very low. I've done the calcs on a
spreadsheet but cross-checked with the Myson calculator for the floor and
air changes of one room, to sanity check.

Does this seem right? I could put it all through the Myson to completely
cross-check it but it's a lot of extra work ...

tia

This seems low to me as well.

Presumably this is an older property with solid walls..??

I've assumed 220mm brick + 13mm plaster, U=2.0 (from BS5449 - I see Myson
use a figure of 1.8 for this construction).

I would expect the extension to have a fairly large heat loss because
of the external wall area.

(The extension shares a party wall with next door.)
I make its loss though external walls 712W. (Actually that includes a new 2m
extension to the ground floor at the back, which has insulated cavity
walls.)

How have you treated the party walls?

I've assumed next door temperatures of 15 downstairs, 10 upstairs (more
pessimistic than the usual 18 up and down, I know).

So for example my big main room (through lounge) has a party wall area of 2
(party walls) * 7.4m (width) * 2.4m (height) = 35.52m^2, and therefore a
heat loss of 35.52 * 2.0 (U value) * 6 (21C - 15C temp diff) = 426 Watts



--
John Stumbles
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-+

"Ed Sirett" wrote in message
news
On Mon, 05 Jan 2004 20:04:34 +0000, Andy Hall wrote:

On Mon, 5 Jan 2004 19:50:40 -0000, "John Stumbles"
] wrote:

I've just done a heatloss calculation for a small terraced house (3.8m
wide
x 7.4m deep x 2.4m each storey with 2.5m x 4m back addition, mix of
carpeted
wooden and solid floors, mostly single glazed, 50mm insulation in the
roof)
and get just over 6.5kW, which seems very low. I've done the calcs on a
spreadsheet but cross-checked with the Myson calculator for the floor
and
air changes of one room, to sanity check.

Does this seem right? I could put it all through the Myson to completely
cross-check it but it's a lot of extra work ...

tia

This seems low to me as well.

Presumably this is an older property with solid walls..??

I would expect the extension to have a fairly large heat loss because
of the external wall area.

How have you treated the party walls?

Have you allowed for the air changes?

Yup, 1.5 for the main room, 2 for kit & bath, 1 for bedrooms.

I'd go high on those to allow for the sash windows.

Fortunately (from an energy conservation rather than architectural
conservation standpoint :-) they're not sashes. However the front door opens
into the main room so I'll probably go for 2 changes there, though that
still only gives me a total of a bit under 7kW.



Anyone know of a small output condensing model?

I had one of those Isars in the back of my van the other day... :-)


--
John Stumbles
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-+
I read a book on improving your memory but I've forgotten what it was
called

On Mon, 5 Jan 2004 20:45:48 -0000, "John Stumbles"
] wrote:



I've assumed 220mm brick + 13mm plaster, U=2.0 (from BS5449 - I see Myson
use a figure of 1.8 for this construction).

I would expect the extension to have a fairly large heat loss because
of the external wall area.

(The extension shares a party wall with next door.)
I make its loss though external walls 712W. (Actually that includes a new 2m
extension to the ground floor at the back, which has insulated cavity
walls.)

OK, so that takes out a fair chunk of outside wall area down to a much
lower heat loss.



How have you treated the party walls?

I've assumed next door temperatures of 15 downstairs, 10 upstairs (more
pessimistic than the usual 18 up and down, I know).

Seems reasonably conservative.



So for example my big main room (through lounge) has a party wall area of 2
(party walls) * 7.4m (width) * 2.4m (height) = 35.52m^2, and therefore a
heat loss of 35.52 * 2.0 (U value) * 6 (21C - 15C temp diff) = 426 Watts


In the very first house that we had where I installed heating, it was
also a terrace, although quite a bit larger than this one - probably
about 1.5m wider and quite a bit deeper, with an original 2 storey
extension. There was also a fourth bedroom in the loft - basically
in the apex area of the main part of the house.

The design was done when it was customary to allow 3kW for the HW
cylinder. I can remember that the total heat load, worst case, with
10% allowance came to 20kW and I used a legendary Potterton Netaheat
16-22 wound up to full power. This would have meant that the house
peak requirement was probably around 14kW. I did design assuming no
heating in neighbouring properties though.



..andy

To email, substitute .nospam with .gl

On Mon, 5 Jan 2004 20:56:48 -0000, "John Stumbles"
] wrote:



Fortunately (from an energy conservation rather than architectural
conservation standpoint :-) they're not sashes. However the front door opens
into the main room so I'll probably go for 2 changes there, though that
still only gives me a total of a bit under 7kW.


Also don't forget the heat loss of the door. This is going to have
something of an effect since it is opening directly into the living
room, especially if it has glass panels.




Anyone know of a small output condensing model?

I had one of those Isars in the back of my van the other day... :-)

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 5 Jan 2004 20:45:48 -0000, "John Stumbles"

I've assumed 220mm brick + 13mm plaster, U=2.0 (from BS5449 - I see Myson
use a figure of 1.8 for this construction).

I would expect the extension to have a fairly large heat loss because
of the external wall area.

(The extension shares a party wall with next door.)
I make its loss though external walls 712W. (Actually that includes a new
2m
extension to the ground floor at the back, which has insulated cavity
walls.)

OK, so that takes out a fair chunk of outside wall area down to a much
lower heat loss.



How have you treated the party walls?

I've assumed next door temperatures of 15 downstairs, 10 upstairs (more
pessimistic than the usual 18 up and down, I know).

Seems reasonably conservative.



So for example my big main room (through lounge) has a party wall area of
2
(party walls) * 7.4m (width) * 2.4m (height) = 35.52m^2, and therefore a
heat loss of 35.52 * 2.0 (U value) * 6 (21C - 15C temp diff) = 426 Watts


In the very first house that we had where I installed heating, it was
also a terrace, although quite a bit larger than this one - probably
about 1.5m wider and quite a bit deeper, with an original 2 storey
extension. There was also a fourth bedroom in the loft - basically
in the apex area of the main part of the house.

The design was done when it was customary to allow 3kW for the HW
cylinder. I can remember that the total heat load, worst case, with
10% allowance came to 20kW and I used a legendary Potterton Netaheat
16-22 wound up to full power. This would have meant that the house
peak requirement was probably around 14kW. I did design assuming no
heating in neighbouring properties though.

My first house was similar to the one you describe and I remember when I did
the calcs it wanted a bit more than a 55K BTUs back-boiler would have given.

However the house in question is heated by night storage and it's generally
as warm as toast (during the day, when I've been working there) in the big
main room which has only one storage heater, which can't be chucking out
more than a couple of kW. From that point of view the figures seem
reasonable ... but I'm still not happy with it. :-(


--
John Stumbles
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-+
Pessimists are never disappointed

On Mon, 5 Jan 2004 20:45:48 -0000, "John Stumbles"
] wrote:


and get just over 6.5kW, which seems very low. I've done the calcs on a
spreadsheet but cross-checked with the Myson calculator for the floor and
air changes of one room, to sanity check.

Does this seem right? I could put it all through the Myson to completely
cross-check it but it's a lot of extra work ...

It seems pretty reasonable to me. Most of your wall area is shared
with the neighbours (assuming it is mid terrace) and if you have good
loft insulation the heat loss would be quite small.

Looking at the heat loss calculations that I did for my house before I
renovated it I got values ranging from 15Kw if I installed no
insulation to 8kw if I installed as much insulation as was feasible.
These included 3.6Kw for air changes. This is for a detached house
about 10M square on 3 floors so it should need a lot more heat than a
terraced house.

Experience has shown that the calculations were pretty accurate.

Bill T

wrote in message
...

Looking at the heat loss calculations that I did for my house before I
renovated it I got values ranging from 15Kw if I installed no
insulation to 8kw if I installed as much insulation as was feasible.
These included 3.6Kw for air changes. This is for a detached house
about 10M square on 3 floors so it should need a lot more heat than a
terraced house.

Unless I'm completely wrong about calculating vent losses, then your air
change figure sounds extremely low. Even at one change an hour (very low
as an average for the house), a three storey 10x10 house is going to need
something like 10*10*7 [height, guess] * 1 * .33 * 24 [tempDrop] = 5.5kW.

How did you do the air-change loss?

Will