22 Jan
2013
22 Jan
'13
3:10 p.m.
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
My thoughts went something like this
1/ If one knows the air temperature , humidity, wind velocity,
distance to, and composition and dryness of surrounding bush .
2/ Can't one calculate the radiant heat in KW/m2 impacting on the
building ?; and
3/ the likely duration in the event of a bush-fire ?
4/ Can't one then calculate the minimum spray flow in litres / sec and
the total volume
of water required ?
5/ Can't one then make an informed decision about,
whether such a system is physically and financially practical in
a particular situation?
Because such systems don't seem to receive much attention from media or
insurance companies ;
I assumed the answer must be that they are usually not practical.
So I was somewhat surprised on reading :
http://en.wikipedia.org/wiki/External_water_spray_system
to find: "Issues
There is a lack of scientific research regarding
EWSS..........."
I am contacting the CSIRO because I seem to recall they did something on
this years ago;
but would be interested in actual research if anyone has come across it ;
regards Rohan McLeod
22 Jan
22 Jan
3:41 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/2013 3:10 PM, Rohan McLeod wrote:
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
My thoughts went something like this
1/ If one knows the air temperature, humidity, wind velocity,
distance to, and composition and dryness of surrounding bush.
Some of those would be quite variable but might be possible.
2/ Can't one calculate the radiant heat in KW/m2
impacting on the
building ?; and
3/ the likely duration in the event of a bush-fire ?
4/ Can't one then calculate the minimum spray flow in litres / sec and the total
volume
of water required ?
5/ Can't one then make an informed decision about,
whether such a system is physically and financially practical in
a particular situation?
That all seems reasonable.
There was an item in a doco a while ago (I think it included the CSIRO)
and they seemed to be interested in using water absorbent crystals
(sodium polyacrylate I guess). Used less water and lasted longer. Their
demo looked quite impressive. I have no idea how it would be "sprayed"
on to a home in practise though.
Cheers,
Mike
3:57 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Mike Mitchell wrote:
On 22/01/2013 3:10 PM, Rohan McLeod wrote:
There seem to be quite a few commercial systems; but I guess I was
wondering about their underlying theoretical basis ?
regards Rohan McLeod
..................snip e then make an informed
decision about,
whether such a system is physically and financially practical in
a particular situation?
That all seems reasonable.
There was an item in a doco a while ago (I think it included the
CSIRO) and they seemed to be interested in using water absorbent
crystals (sodium polyacrylate I guess). Used less water and lasted
longer. Their demo looked quite impressive. I have no idea how it
would be "sprayed" on to a home in practise though. 
4:03 p.m.
On Tue, 22 Jan 2013, Rohan McLeod <rhn(a)jeack.com.au> wrote:
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
My thoughts went something like this
1/ If one knows the air temperature , humidity, wind velocity,
distance to, and composition and dryness of surrounding bush .
2/ Can't one calculate the radiant heat in KW/m2 impacting on the
building ?; and
I don't think it's the heat on the overall building that matters. It's the
heat coming through the windows, to leaves in the gutters, to exposed wooden
parts of the building, etc.
After bushfires you see chimneys still standing, so it's obviously possible to
make bricks that won't be significantly damaged by fire. Are regular brick
walls sufficient? If not how much more does it cost to use fire bricks?
Will a fire make a galvanised iron roof hot enough to bend or to set fire to
wooden beams in the ceiling? If the former then a water spray would help, but
I suspect that the latter would be the only problem in which case iron roof
beams would be the solution.
It seems to me that if a building was constructed to be heat resistant and had
solid shutters on all the windows (EG hard wood shutters with gaps too small
for embers with a sheet of galvanised iron on the outside) then you probably
wouldn't need external water.
But if the building has gaps that allow embers in (EG a typical tile root),
has wooden window frames, has big windows with flammable curtains, or many
other features of typical homes then even a water spray won't necessarily
solve the problem.
3/ the likely duration in the event of a bush-fire ?
The radiant heat will be of very small duration. Wind-blown embers will last
for a much longer time.
Because such systems don't seem to receive much
attention from media or
insurance companies ;
I assumed the answer must be that they are usually not practical.
So I was somewhat surprised on reading :
http://en.wikipedia.org/wiki/External_water_spray_system
If I was living in an area that's at risk of bush fire then I'd get have an
entirely concrete house built with solid shutters on the windows.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
4:35 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Russell Coker wrote:
..............snip
So I was somewhat surprised on reading :
http://en.wikipedia.org/wiki/External_water_spray_system
If I was living in an area that's at risk of bush fire then I'd get have an
entirely concrete house built with solid shutters on the windows.
Well here in
Pasco Vale in a solid brick block of flats, the bush-fire
risk is fairly minimal;
really just idle curiosity to see why such spray systems aren't more common;
thanks for your interest though;
regards
Rohan McLeod
4:43 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 4:03 PM, Russell Coker wrote:
I don't think it's the heat on the overall
building that matters. It's
the heat coming through the windows, to leaves in the gutters, to
exposed wooden parts of the building, etc. After bushfires you see
chimneys still standing, so it's obviously possible to make bricks
that won't be significantly damaged by fire. Are regular
There are two main
issues with buildings - radiant heat directly
affecting flammable materials, and ember attack (direct flame contact
can be prevented with a good garden design).
Radiant heat needs to be blocked by physical barriers (e.g. brick walls,
window shutters, water sprays). Ember attacks are probably best
prevented by a building design that doesn't give embers an opportunity
to lodge near flammable material (open eaves and under floor spaces are
bad news), because ember attacks can last a considerable time before the
main fire arrives (some embers can be blown over 30km ahead of the main
fire on a bad day).
Of course, maintenance such as cleaning gutters (or having a decent
gutter guard) and keeping litter and debris away from the house will help!
--
73 de Tony VK3JED
http://vkradio.com
4:36 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 3:10 PM, Rohan McLeod wrote:
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
My thoughts went something like this
1/ If one knows the air temperature , humidity, wind velocity,
distance to, and composition and dryness of surrounding bush .
2/ Can't one calculate the radiant heat in KW/m2 impacting on the
building ?; and
3/ the likely duration in the event of a bush-fire ?
4/ Can't one then calculate the minimum spray flow in litres / sec and
the total volume
of water required ?
5/ Can't one then make an informed decision about,
whether such a system is physically and financially practical in
a particular situation?
I can only comment on the system I know, which is the
protection system
used on a typical tanker (a lot smaller area to protect than a house!).
For that space, the water usage is 150 litres/minute, and additional
passive shielding is added, such as the vehicle body and reflective
curtains for the windows, as well as individual protective clothing.
I suspect that a house would require considerably more water. Having
some means to cover windows (e.g. shutters) would help reduce the total
radiant heat load. Also, as a house is not mobile and covers greater
length, the time of exposure would be potentially greater. However, you
can use additional protection such as appropriate garden plantings (e.g.
succulent plants are highly fire resistant, due to the high water
content in their leaves/stems).
The CFA have information on planting for fire prone areas that might
help with the garden planning side of things.
The bottom line is "defence in depth", a bit like network security -
having multiple defences which work together to achieve the desired
level of protection.
I think it is feasible to build an active protection system, but it
would be most effective (in both performance and cost) as part of an
overall fire resistant house and garden design.
And no, I don't have any papers to quote on this... yet!
Of course, YMMV, and consult someone with more knowledge before going
down this road.
--
73 de Tony VK3JED
http://vkradio.com
4:57 p.m.
On Tue, 22 Jan 2013, Tony Langdon <vk3jed(a)gmail.com> wrote:
I can only comment on the system I know, which is the
protection system
used on a typical tanker (a lot smaller area to protect than a house!).
For that space, the water usage is 150 litres/minute, and additional
passive shielding is added, such as the vehicle body and reflective
curtains for the windows, as well as individual protective clothing.
By "tanker" do you mean fire truck? If so then presumably the truck is
designed to go into unsafe situations while a sensible person would cut down
trees that are too close to their house and take other measures to reduce the
risk.
I think it is feasible to build an active protection
system, but it
would be most effective (in both performance and cost) as part of an
overall fire resistant house and garden design.
If you had a house made of solid relatively airtight concrete including a
concrete roof with solid shutters then it doesn't seem that you would need any
water protection system. If you had a house of a typical suburban design then
it seems that no reasonable amount of water would save it unless you also have
water inside the roof cavity to stop embers that get through gaps in the
tiles.
It doesn't seem like adding water will be guaranteed to save a house that
wasn't already fairly safe without the water.
Do bushfires get hot enough to ignite aluminium? A quick google suggests that
aluminium ignites at about 2000C which combined with being a great reflector of
light and even better for infra-red means that it's probably going to resist
anything a bushfire can do from a distance. So aluminium shutters should do.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
5:04 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On Tue, 22 Jan 2013, Russell Coker wrote:
If you had a house made of solid relatively airtight
concrete including a
concrete roof with solid shutters then it doesn't seem that you would need any
water protection system.
Earth houses can be useful too:
http://en.wikipedia.org/wiki/Earth_house
Fire protection
Compared to other building materials, such as wood, earth houses feature
efficient fire protection owing both to the use of concrete and the
insulation provided by the roof.
Regards
Peter
5:10 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 5:04 PM, Peter Ross wrote:
On Tue, 22 Jan 2013, Russell Coker wrote:
That looks like an interesting architectural style
that has a lot of
practical benefits. Wombats knew what they were doing all along. ;)
-- 73 de Tony VK3JED http://vkradio.com
If you had a house made of solid relatively
airtight concrete including a
concrete roof with solid shutters then it doesn't seem that you would need any
water protection system.
Earth houses can be useful too:
http://en.wikipedia.org/wiki/Earth_house
Fire protection
Compared to other building materials, such as wood, earth houses feature
efficient fire protection owing both to the use of concrete and the
insulation provided by the roof.
23 Jan
23 Jan
11:28 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On Tue, 22 Jan 2013, Tony Langdon wrote:
On 22/01/13 5:04 PM, Peter Ross wrote:
I wonder why most Australian houses do not seem to have basements.
Any particular reasons?
Regards
Peter
On Tue, 22 Jan 2013, Russell Coker wrote:
That looks like an interesting architectural
style that has a lot of
practical benefits. Wombats knew what they were doing all along. ;) If you had a house made of solid relatively
airtight concrete including a
concrete roof with solid shutters then it doesn't seem that you would need any
water protection system.
Earth houses can be useful too:
http://en.wikipedia.org/wiki/Earth_house
Fire protection
Compared to other building materials, such as wood, earth houses feature
efficient fire protection owing both to the use of concrete and the
insulation provided by the roof.
12:23 p.m.
On Wed, 23 Jan 2013, Peter Ross <Peter.Ross(a)bogen.in-berlin.de> wrote:
Expense is the reason I've seen cited, that combined with the fact that it's
not fashionable. In an Australian summer a basement is a really good thing,
you install your favourite entertainment things and spend the hottest part of
the day avoiding the heat.
Expense is also the reason that houses aren't designed to be fire-proof. In
addition to the things we have already discussed there's no reason why a home
couldn't have sprinklers in every room in the way that hotels are required to.
Hotels have a higher risk of fire due to idiots and due to people getting
confused when not in their own home. But the risk of a house fire is still
there and sprinklers would work well.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
That looks
like an interesting architectural style that has a lot of
practical benefits. Wombats knew what they were doing all along. ;)
I wonder why most Australian houses do not seem to have basements.
Any particular reasons? 
1:25 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 23/01/13 12:23, Russell Coker wrote:
On Wed, 23 Jan 2013, Peter Ross
<Peter.Ross(a)bogen.in-berlin.de> wrote:
Expense is the reason I've seen cited, that combined with the fact that it's
not fashionable. In an Australian summer a basement is a really good thing,
you install your favourite entertainment things and spend the hottest part of
the day avoiding the heat.
Expense is also the reason that houses aren't designed to be fire-proof. In
addition to the things we have already discussed there's no reason why a home
couldn't have sprinklers in every room in the way that hotels are required to.
Hotels have a higher risk of fire due to idiots and due to people getting
confused when not in their own home. But the risk of a house fire is still
there and sprinklers would work well.
Functioning smoke detectors are much more cost effective.
I dread the thought of sprinklers in every house - the commercial ones
get broken enough as it is, and the false alarms from them are a pain as
well.
That
looks like an interesting architectural style that has a lot of
practical benefits. Wombats knew what they were doing all along. ;)
I wonder why most Australian houses do not seem to have basements.
Any particular reasons?
5:29 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Allan Duncan wrote:
On 23/01/13 12:23, Russell Coker wrote:
> On Wed, 23 Jan 2013, Peter Ross <Peter.Ross(a)bogen.in-berlin.de> wrote:
> I dread the thought of sprinklers in every house - the commercial
> ones get broken enough as it is, and the false alarms from them are a
> pain as well. ___
Not to mention apparently horrendously expensive to reset.
I have a one tonne van , 2.1m at the roof-rack which I need to drive in
underground car parks,
often with a height limit of 2.1m. I was truly terrified when I
discovered that,
hitting and setting off the sprinkler system system could cost me
thousands of dollars !
Not even clear whether it is an insurable risk;
regards Rohan McLeod
24 Jan
24 Jan
9:11 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On Wed, 23 Jan 2013, Russell Coker wrote:
On Wed, 23 Jan 2013, Peter Ross
<Peter.Ross(a)bogen.in-berlin.de> wrote:
Expense is the reason I've seen cited, that combined with the fact that it's
not fashionable. In an Australian summer a basement is a really good thing,
you install your favourite entertainment things and spend the hottest part of
the day avoiding the heat.
I wonder how save it is to hide if you are surrounded by a fire.
Basically whether it becomes too hot or you are running out of oxygene
inside. Or other risks I did not think of..
Regards
Peter
That
looks like an interesting architectural style that has a lot of
practical benefits. Wombats knew what they were doing all along. ;)
I wonder why most Australian houses do not seem to have basements.
Any particular reasons?
9:38 a.m.
On Thu, 24 Jan 2013, Peter Ross <Peter.Ross(a)bogen.in-berlin.de> wrote:
Oxygen is the issue.
I've heard reports of people going back to their hotel room for their luggage
and dying from smoke inhalation while their luggage survives...
There's no reason why you can't have a basement with an external door, that's
not an uncommon design. One of my friends has such a basement, I think that
he needed to have a separate exit to have it considered as a separate office
(rather than part of his home) for tax benefits at the time. With such a
design you could hide in your basement while the main fire passes and then if
your home catches on fire you could escape.
--
My Main Blog http://etbe.coker.com.au/
My Documents Blog http://doc.coker.com.au/
Expense is the
reason I've seen cited, that combined with the fact that
it's not fashionable. In an Australian summer a basement is a really
good thing, you install your favourite entertainment things and spend
the hottest part of the day avoiding the heat.
I wonder how save it is to hide if you are surrounded by a fire.
Basically whether it becomes too hot or you are running out of oxygene
inside. Or other risks I did not think of.. 
10:14 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On Thu, Jan 24, 2013 at 9:38 AM, Russell Coker <russell(a)coker.com.au> wrote:
On Thu, 24 Jan 2013, Peter Ross
<Peter.Ross(a)bogen.in-berlin.de> wrote:
Oxygen is the issue.
I've heard reports of people going back to their hotel room for their
luggage
and dying from smoke inhalation while their luggage survives...
There's no reason why you can't have a basement with an external door,
that's
not an uncommon design. One of my friends has such a basement, I think
that
he needed to have a separate exit to have it considered as a separate
office
(rather than part of his home) for tax benefits at the time. With such a
design you could hide in your basement while the main fire passes and then
if
your home catches on fire you could escape.
I have just read a book *Disasters That Changed Australia* by historian
Richard Evans. In his book he talks of the Black Sunday fire of 1932 and
how 6 mill workers were killed in the high country. I quote....
*"After six mill workers were killed in the 1932 fires, the Victorian
Forests Commission began to urge mill owners to establish a safe refuge fo
their workers, in the form of a dugout. This was to built in a cleared area
and topped with a thick layer of earth..." page 107*
*
*
*"The men, woman and children of the little mill settlements sheltered in
dugouts -- where dugouts had been built. There, people were reasonably
safe..." page 108*
He goes on to say that the dugouts had risks but like a lot of wildlife
that sheltered in dugouts or burrows it was the safest option from a fire,
he talks of men being boiled alive in water tanks and others burying
themselves in sawdust piles at the mills to try and get away from the heat.
Richard Evans has a PhD in history from Monash and is a research fellow at
Swinbourne, he is very passionate about Australia's history with fire so
has researched it a great deal. The book *"Disasters That Changed
Australia" *is published by Victory Books, Melbourne University Publishing.
ISBN 978-0-522-85649-1
It is a good book and covers many natural and man made disasters that
shaped Australia, I really enjoyed reading it even f it was in dead tree
format and I had to get used to turning pages as it didnt have turn buttons
on the side :)
--
Mark "Pockets" Clohesy
Mob Phone: (+61) 406 417 877
Email: hiddensoul(a)twistedsouls.com
G-Talk: mark.clohesy(a)gmail.com
GNU/Linux..Linux Counter #457297
-
"I would love to change the world, but they won't give me the source code"
"Linux is user friendly...its just selective about who its friends are"
Expense
is the reason I've seen cited, that combined with the fact that
it's not fashionable. In an Australian summer a basement is a really
good thing, you install your favourite entertainment things and spend
the hottest part of the day avoiding the heat.
I wonder how save it is to hide if you are surrounded by a fire.
Basically whether it becomes too hot or you are running out of oxygene
inside. Or other risks I did not think of..
22 Jan
22 Jan
5:08 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 4:57 PM, Russell Coker wrote:
By "tanker" do you mean fire truck? If so
then presumably the truck is
designed to go into unsafe situations while a sensible person would cut down
trees that are too close to their house and take other measures to reduce the
risk.
Yep, and I did say garden design would be part of making a house fire
resistant, which would cover cutting down trees, etc.
If you had a house made of solid relatively airtight
concrete including a
concrete roof with solid shutters then it doesn't seem that you would need any
water protection system. If you had a house of a typical suburban design then
it seems that no reasonable amount of water would save it unless you also have
water inside the roof cavity to stop embers that get through gaps in the
tiles.
The water would limit damage to the concrete or other structural
materials, but the use of such materials would minimise any extra
protection needed.
It doesn't seem like adding water will be guaranteed to save a house that
wasn't already fairly safe without the water.
Do bushfires get hot enough to ignite aluminium? A quick google suggests that
aluminium ignites at about 2000C which combined with being a great reflector of
light and even better for infra-red means that it's probably going to resist
anything a bushfire can do from a distance. So aluminium shutters should do.
They certainly get hot enough to _melt_ aluminium. A school friend had
a "souvenir" from being burnt out during Ash Wednesday. It looked like
a bit of modern sculpture, like something poured out and painted
silver. What it was, in fact, was the remains of the engine block from
their lawnmower. The heat from the fire had turned the engine block
into a pool of molten metal.
--
73 de Tony VK3JED
http://vkradio.com
5:21 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 01/22/2013 04:57 PM, Russell Coker wrote:
On Tue, 22 Jan 2013, Tony Langdon
<vk3jed(a)gmail.com> wrote:
> I can only comment on the system I know, which is the protection system
> used on a typical tanker (a lot smaller area to protect than a house!).
> For that space, the water usage is 150 litres/minute, and additional
> passive shielding is added, such as the vehicle body and reflective
> curtains for the windows, as well as individual protective clothing.
an Australian Standard fire hydrant is to supply for 300 litres/minute
at 700kPa and should be supplied from a system 4 hours supply with
positive feed.
Do bushfires get hot enough to ignite aluminium?
Melting is a bigger problem as Al melts below 650C depending on the
other elements in the alloy, as pure Al is almost never used, so 550C
and cooler is found.
Steve
previously worked in the fire protection industry
6:59 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Steve Roylance wrote:
On 01/22/2013 04:57 PM, Russell Coker wrote:
Please correct me if I am reading this incorrectly;
street fire hydrants are intended to supply 300 litres/ minute at a
pressure of 700kPa ?
presumably with a much higher pressure with no flow ?
Further the supply to such a hydrant must be sufficient in volume, for
4 hours flow at this rate ;
that is 720,000 litres or 720 m^3 ?;
where an Olympic swimming pool say contains 50 x 25 x 1 m^3 = 1250 m^3 ?
thanks Rohan
McLeod
On Tue, 22 Jan 2013, Tony Langdon
<vk3jed(a)gmail.com> wrote:
> I can only comment on the system I know, which is the protection system
> used on a typical tanker (a lot smaller area to protect than a house!).
> For that space, the water usage is 150 litres/minute, and additional
> passive shielding is added, such as the vehicle body and reflective
> curtains for the windows, as well as individual protective clothing.
an
Australian Standard fire hydrant is to supply for 300 litres/minute
at 700kPa and should be supplied from a system 4 hours supply with
positive feed.
7:34 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 01/22/2013 06:59 PM, Rohan McLeod wrote:
Steve Roylance wrote:
AS-2419 which I am quoting is about in building hydrants, and AS-2118
for sprinklers.
this is about right, if the mains cannot supply the pressure then a
booster pump is needed and if it cannot do the volume then a tank is needed.
Cannot get exact clause quotes as all is behind a paywall, even as they
are required by govt. regulations.
Steve
On 01/22/2013 04:57 PM, Russell Coker wrote:
Please correct me if I am reading this incorrectly;
street fire hydrants are intended to supply 300 litres/ minute at a
pressure of 700kPa ?
presumably with a much higher pressure with no flow ?
Further the supply to such a hydrant must be sufficient in volume, for
4 hours flow at this rate ;
that is 720,000 litres or 720 m^3 ?;
where an Olympic swimming pool say contains 50 x 25 x 1 m^3 = 1250 m^3 ? On Tue, 22 Jan 2013, Tony Langdon
<vk3jed(a)gmail.com> wrote:
> I can only comment on the system I know, which is the protection system
> used on a typical tanker (a lot smaller area to protect than a house!).
> For that space, the water usage is 150 litres/minute, and additional
> passive shielding is added, such as the vehicle body and reflective
> curtains for the windows, as well as individual protective clothing.
an
Australian Standard fire hydrant is to supply for 300 litres/minute
at 700kPa and should be supplied from a system 4 hours supply with
positive feed. 
7:33 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22 January 2013 16:57, Russell Coker <russell(a)coker.com.au> wrote:
If you had a house made of solid relatively airtight
concrete including a
concrete roof with solid shutters then it doesn't seem that you would need
any
water protection system. If you had a house of a typical suburban design
then
it seems that no reasonable amount of water would save it unless you also
have
water inside the roof cavity to stop embers that get through gaps in the
tiles.
It doesn't seem like adding water will be guaranteed to save a house that
wasn't already fairly safe without the water.
Don't forgot that most houses burn down after the fire front has passed. If
the house survives or not depends on if there is somebody around (risking
their necks) to put out the small spot fires before they result in the
house burning down.
Of course exceptions exist. Have heard that one house had its roof blown
away, after which there was no saving it.
The other problematic area in the Marysville's fire was the gas cylinder
venting valves pointing at other houses, and resulting damage, including
broken windows which embers could enter.
I see a number of problems with the sprinkler system:
* Relying on mains water pressure or mains electricity is a big no no,
there probably won't be any. That fire truck up the road will be using all
the water pressure, and a tree will be down across the power lines.
* If it is a petrol/diesel pump, somebody has to be able to start it. Plus
it may not start when required.
* The system would be very exposed as the main fire front passes.
* If you start it before the fire front, you use up all your water before
it is needed (after the front passes).
* If you start it as the fire front is passing through you get burnt. Plus
the water will evaporate and has no affect whatsoever.
* Ideal is to start it after fire front has passed, but you have to be
around (and exposing yourself to danger) to do so.
* After fire passes there is no guarantee that you will get water where it
is needed (to put out the spot fires).
So a sprinkler system that gets its supply from tanks and has diesel/petrol
powered pump, that somehow can be activated after the main fire front has
passed might be a good thing. Although not as good as being there to put
out spot fires with a wet mop (yes, I have heard stories of people saving
their houses with nothing more then mops and a bath previously filled with
water). The problem is with activating the sprinklers at the appropriate
time. And obviously you can't rely on mains power, telephone, ADSL, 3G,
etc, which you normally would use for remote control applications.
--
Brian May <brian(a)microcomaustralia.com.au>
7:45 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/2013 7:33 PM, Brian May wrote:
I see a number of problems with the sprinkler system:
* Relying on mains water pressure or mains electricity is a big no no,
there probably won't be any. That fire truck up the road will be using
all the water pressure, and a tree will be down across the power lines.
An appropriate header tank would take care of that but may not be of use
with your other concerns.
Cheers,
Mike
8:16 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Brian May wrote:
On 22 January 2013 16:57, Russell Coker
<russell(a)coker.com.au
<mailto:russell@coker.com.au>> wrote:
If you had a house made of solid relatively airtight concrete
including a
concrete roof with solid shutters then it doesn't seem that you
would need any
water protection system. If you had a house of a typical suburban
design then
it seems that no reasonable amount of water would save it unless
you also have
water inside the roof cavity to stop embers that get through gaps
in the
tiles.
It doesn't seem like adding water will be guaranteed to save a
house that
wasn't already fairly safe without the water.
Don't forgot that most houses burn down after the fire front has
passed. If the house survives or not depends on if there is somebody
around (risking their necks) to put out the small spot fires before
they result in the house burning down.
Of course exceptions exist. Have heard that one house had its roof
blown away, after which there was no saving it.
The other problematic area in the Marysville's fire was the gas
cylinder venting valves pointing at other houses, and resulting
damage, including broken windows which embers could enter.
I see a number of problems with the sprinkler system:
* Relying on mains water pressure or mains electricity is a big no no,
there probably won't be any. That fire truck up the road will be using
all the water pressure, and a tree will be down across the power lines.
* If it is a petrol/diesel pump, somebody has to be able to start it.
Plus it may not start when required.
* The system would be very exposed as the main fire front passes.
* If you start it before the fire front, you use up all your water
before it is needed (after the front passes).
..............snip
It may be that it is only practical ( physically achievable and
cost
effective) in certain situations.
Which was why I was interested in the fundamental research.
Consider an all weather-board house I visited in Belgrave ( in the
middle of winter);
which had state-forest with 30m gums and heavy undergrowth within 10m
of the back of the house;
I suspect the radiant flux from a crown-fire there would heat the air
inside so rapidly it would almost explode !;
regards Rohan McLeod
8:29 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22 January 2013 20:16, Rohan McLeod <rhn(a)jeack.com.au> wrote:
It may be that it is only practical ( physically
achievable and cost
effective) in certain situations.
Which was why I was interested in the fundamental research.
Consider an all weather-board house I visited in Belgrave ( in the
middle of winter);
which had state-forest with 30m gums and heavy undergrowth within 10m
of the back of the house;
I suspect the radiant flux from a crown-fire there would heat the air
inside so rapidly it would almost explode !;
Yes, very important to consider your own set of circumstances before
deciding to risk your own neck and stay and protect your property.
If there is a large build up of leaves, etc, next to the weatherboard you
could be in trouble. In fact, have heard weatherboard is a problem anyway.
There is a free evaluation system offered by the government to have
somebody inspect your property and rate it for fire danger. Not sure if
this applies to properties you are considering buying. I haven't seen the
details.
Also you probably shouldn't even consider staying if you are looking after
kids (for example).
--
Brian May <brian(a)microcomaustralia.com.au>
10:55 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 19:33, Brian May wrote:
On 22 January 2013 16:57, Russell Coker
<russell(a)coker.com.au
<mailto:russell@coker.com.au>> wrote:
If you had a house made of solid relatively airtight concrete
including a
concrete roof with solid shutters then it doesn't seem that you
would need any
water protection system. If you had a house of a typical suburban
design then
it seems that no reasonable amount of water would save it unless you
also have
water inside the roof cavity to stop embers that get through gaps in the
tiles.
It doesn't seem like adding water will be guaranteed to save a house
that
wasn't already fairly safe without the water.
Don't forgot that most houses burn down after the fire front has passed.
If the house survives or not depends on if there is somebody around
(risking their necks) to put out the small spot fires before they result
in the house burning down.
Of course exceptions exist. Have heard that one house had its roof blown
away, after which there was no saving it.
The other problematic area in the Marysville's fire was the gas cylinder
venting valves pointing at other houses, and resulting damage, including
broken windows which embers could enter.
I see a number of problems with the sprinkler system:
* Relying on mains water pressure or mains electricity is a big no no,
there probably won't be any. That fire truck up the road will be using
all the water pressure, and a tree will be down across the power lines.
* If it is a petrol/diesel pump, somebody has to be able to start it.
Plus it may not start when required.
* The system would be very exposed as the main fire front passes.
* If you start it before the fire front, you use up all your water
before it is needed (after the front passes).
* If you start it as the fire front is passing through you get burnt.
Plus the water will evaporate and has no affect whatsoever.
* Ideal is to start it after fire front has passed, but you have to be
around (and exposing yourself to danger) to do so.
* After fire passes there is no guarantee that you will get water where
it is needed (to put out the spot fires).
So a sprinkler system that gets its supply from tanks and has
diesel/petrol powered pump, that somehow can be activated after the main
fire front has passed might be a good thing. Although not as good as
being there to put out spot fires with a wet mop (yes, I have heard
stories of people saving their houses with nothing more then mops and a
bath previously filled with water). The problem is with activating the
sprinklers at the appropriate time. And obviously you can't rely on
mains power, telephone, ADSL, 3G, etc, which you normally would use for
remote control applications.
The usual way is to use thermal sensors, and of course it needs to
auto-start the pump that uses local storage.
23 Jan
23 Jan
11:08 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On Tue, 22 Jan 2013, Russell Coker wrote:
On Tue, 22 Jan 2013, Tony Langdon
<vk3jed(a)gmail.com> wrote:
Most of the buildings on Siding Spring are 1960/70's era, brick, tin
roof. Following the 2003 Mt Stromlo fires, they were all retrofitted with
fire screens over the windows, clearing of the trees around any building
and not much else (this was cost effective enough).
The fires last week took out the lodge, which was still quite close to
trees and right on the ridge, but little else (it's ironic that that part
of the mountain is now off limits because much asbestos has been spread
around. The fire proof asbestos didn't do its job properly and has now
spread over half of NSW!). The ember screens did their job as expected.
The external temperature according to the met station was observed at 104
degrees for less than a minute as the fire went overhead (may have of
course peaked higher). That wouldn't be measuring radiant heat (the
sensor is inside a stevenson screen), but most house fires are from ember
attack through broken windows. My memory is that the trees are quite
close to the met tower.
I think it is feasible to build an active
protection system, but it
would be most effective (in both performance and cost) as part of an
overall fire resistant house and garden design.
If you had a house made of solid relatively airtight concrete including a
concrete roof with solid shutters then it doesn't seem that you would need any
water protection system. If you had a house of a typical suburban design then
it seems that no reasonable amount of water would save it unless you also have
water inside the roof cavity to stop embers that get through gaps in the
tiles.
It doesn't seem like adding water will be guaranteed to save a house that
wasn't already fairly safe without the water. Do bushfires get hot enough to ignite aluminium? A
quick google suggests that
aluminium ignites at about 2000C which combined with being a great reflector of
light and even better for infra-red means that it's probably going to resist
anything a bushfire can do from a distance. So aluminium shutters should do.
I've got a spluttered piece of aluminium dome as souvenir from one of the
Mt Stromlo domes, obtained 2 weeks after the fire went through. Melting
point is more relevant than ignition point. That was a *freakin* hot
fire. Having seen timelapse footage of the #SSO fires, I don't think it
was quite so ferocious.
Incidentally, this is my ex-bosses house:
https://twitter.com/702sydney/status/293641215155523584/photo/1
According to my other ex-boss, a coworker in the RFS was driving the
tanker back into town after the fire had already been fought, and they
noticed in the nick of time that it had flared up again.
--
Tim Connors
24 Jan
24 Jan
4:12 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Do bushfires get hot enough to ignite aluminium? A
quick google
suggests that aluminium ignites at about 2000C which combined with
being a great reflector of light and even better for infra-red means
that it's probably going to resist anything a bushfire can do from a
distance. So aluminium shutters should do.
Ignites, maybe not.. melts tho @ 660.32°C
10:34 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 01/24/2013 04:12 AM, Anthony Hogan wrote:
hi
that is for pure Al, which is unusual, as a alloy 577°C or lower, would
be more likely as adding other elements makes it easier for the casting
& machining.
Steve
Do bushfires
get hot enough to ignite aluminium? A quick google
suggests that aluminium ignites at about 2000C which combined with
being a great reflector of light and even better for infra-red means
that it's probably going to resist anything a bushfire can do from a
distance. So aluminium shutters should do.
Ignites, maybe not.. melts tho @ 660.32°C
22 Jan
22 Jan
10:35 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 15:10, Rohan McLeod wrote:
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
[...]
The term "bushfire protection" needs to be better defined before you can
move on to numbers on a page.
If there is heavy vegetation right up to the house, then radiant heat
and flame impact is the operating mode, and the figures for burn-over
protection of a fire truck applies (mentioned by another reply).
If you have done a proper preparation and the house is more than three
times the tree height away from the bush, then the operating mode is
ember attack. CSIRO recommended (years ago) that the house was painted
white if timber, had all sub-floor areas fully boxed in, and
eaves/roofing was gap filled.
Even then there is a good chance of embers getting in, and this is where
a water spray can help. Its function is to damp down all surfaces and
cracks to extinguish embers that contact the structure, and it must do
that in winds that easily exceed 50Kph. This means that any sprays must
generate large droplet sizes, and direct the flow parallel and close to
the surface to be protected.
Sprinklers on the roof are largely a waste of water - if you must have
them, then use a supply pipe along the ridge with the sprays under it so
the spray pattern is close to the roofing. Roof spray water can be
collected, filtered and recirculated to extend the running time IF you
can design a system and filter that won't get clogged by all the flying
debris. Its main use is filling the gutters to extinguish said flying
debris since the gutters were spotless before the fire started, weren't
they?
10:48 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 22:35, Allan Duncan wrote:
On 22/01/13 15:10, Rohan McLeod wrote:
I forgot one use of roof sprays - tile roof. Most houses around here
are steel roofed, so it slipped by me. Tiles without a fire blanket are
a bad idea - on Ash Wednesday I saw a two story place with 30m of green
grass and a 2m brick front fence between it and the fire front catch
fire in the roof an hour after the front had passed either side. Just a
small trickle of smoke from the end of the ridge, would have been an
easy save except no ladder and there were other houses under threat from
the flank of the fire. When we came back past there was just a heap of
rubble.
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
[...]
The term "bushfire protection" needs to be better defined before you can
move on to numbers on a page.
If there is heavy vegetation right up to the house, then radiant heat
and flame impact is the operating mode, and the figures for burn-over
protection of a fire truck applies (mentioned by another reply).
If you have done a proper preparation and the house is more than three
times the tree height away from the bush, then the operating mode is
ember attack. CSIRO recommended (years ago) that the house was painted
white if timber, had all sub-floor areas fully boxed in, and
eaves/roofing was gap filled.
Even then there is a good chance of embers getting in, and this is where
a water spray can help. Its function is to damp down all surfaces and
cracks to extinguish embers that contact the structure, and it must do
that in winds that easily exceed 50Kph. This means that any sprays must
generate large droplet sizes, and direct the flow parallel and close to
the surface to be protected.
Sprinklers on the roof are largely a waste of water - if you must have
them, then use a supply pipe along the ridge with the sprays under it so
the spray pattern is close to the roofing. Roof spray water can be
collected, filtered and recirculated to extend the running time IF you
can design a system and filter that won't get clogged by all the flying
debris. Its main use is filling the gutters to extinguish said flying
debris since the gutters were spotless before the fire started, weren't
they? 
10:56 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
Allan Duncan wrote:
On 22/01/13 15:10, Rohan McLeod wrote:
Many thanks for the practical advice;
my interest as mentioned is more idle curiosity though and
the theoretical limits of spray systems.
As far as 'bush-fire protection' goes;
I am thinking specifically of avoiding fire damage during the actual
bush-fire;
as far as 'bush-fire' goes I would prefer some kind of continuum definition;
that is a function of height, distance, intensity and duration;
don't know if that helps,
regards Rohan McLeod
Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the practicability
of protecting buildings ,
using external water-spray systems.
[...]
The term "bushfire protection" needs to be better defined before you can
move on to numbers on a page.
11:20 p.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 22:56, Rohan McLeod wrote:
Allan Duncan wrote:
The biggest risk to my house is the neighbouring house to the north,
which is open underneath the floor.
It's called Exposure in the firefighting business:
Rescue
Exposure
Confinement
Extinguishment
Overhaul
On 22/01/13 15:10, Rohan McLeod wrote:
Many thanks for the practical advice;
my interest as mentioned is more idle curiosity though and
the theoretical limits of spray systems.
As far as 'bush-fire protection' goes;
I am thinking specifically of avoiding fire damage during the actual
bush-fire;
as far as 'bush-fire' goes I would prefer some kind of continuum
definition;
that is a function of height, distance, intensity and duration;
don't know if that helps, Assembled cognoscenti;
it being the bush-fire season my thoughts turned to the
practicability
of protecting buildings ,
using external water-spray systems.
[...]
The term "bushfire protection" needs to be better defined before you can
move on to numbers on a page.
23 Jan
23 Jan
7:51 a.m.
New subject: Bush-fire protection of buildings using external water-spray systems
On 22/01/13 11:20 PM, Allan Duncan wrote:
The biggest risk to my house is the neighbouring house
to the north,
which is open underneath the floor.
It's called Exposure in the firefighting business:
Rescue
Exposure
Confinement
Extinguishment
Overhaul
Yep, know that one well. :)
--
73 de Tony VK3JED
http://vkradio.com
3719
days inactive
3720
days old
33 comments
12 participants
participants (12)
-
Allan Duncan -
Anthony Hogan -
Brian May -
Hiddensoul (Mark Clohesy) -
Mike Mitchell -
Peter Ross -
Rohan McLeod -
Rohan McLeod -
Russell Coker -
Steve Roylance -
Tim Connors -
Tony Langdon