D.I.Y. Double glazing.

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Re: D.I.Y. Double glazing.

Postby Tracker » Thu Oct 04, 2012 5:09 pm

Cherokee Solar wrote: I can't recommend crimsafe shutters over windows highly enough.

That crimsafe stuff would likely block out 80% of radiation.. I would have been VERY surprised if it did not have a tremendous impact on cooling.
Well fitted, I would imagine they would near fire-proof a brick home, if you could guarantee the roof and eves.
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Re: D.I.Y. Double glazing.

Postby Cherokee Solar » Thu Oct 04, 2012 10:11 pm

Hey Tracker,

Brick houses are not as good in a fire as you'd think. Double brick is much better than a brick veneer. A well maintained weatherboard will always outperform a brick veneer in these circumstances.

In a brick veneer construction, the bricks heat up from an external fire, then transfer that heat to the steel brick ties and from there onto a very dry timber pine frame. As you quite rightly point out, as well as this they are not very well sealed around the roof (tiles are a disaster) and they also have weep holes which can allow embers and dry material to enter (and also build up in) near the slab where a grass fire may run to. All up not good and the bricks themselves take a very long time to cool down and can store and radiate that heat. Interestingly too, the mortar can shrink and crack also allowing radiant heat and embers to get in.

If you are interested in the latest tech with regards to fire rated roofs have a look at:
http://www.timber.net.au/images/downloads/fire/4-1-roof-data-sheet-1811_09.pdf

This was the system that I constructed (page 4 shows the design cross section and materials), it is pretty interesting stuff. The materials were very hard to obtain as they are commercial and no supplier wanted to supply a domestic volume. I'm sure I was ripped off, but had no choice in the matter as the building code was final. :shock:

Fire resistant houses are best designed like an onion with lots of layers. The front of a bushfire moves through in minutes, so having fall back layers is the trick. Think about how difficult it is to burn a telephone book and you'll get the gist of it. ;)

Chris
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Re: D.I.Y. Double glazing.

Postby Tracker » Fri Oct 05, 2012 9:15 am

Cherokee Solar wrote:The front of a bushfire moves through in minutes,

Whilst the phone book analogy is good, I would wonder why a properly designed home in single brick or timber, would be any different.
With the brick holes, they can be filled or stuffed with stainless pot scourer.
Either home has the same roof.
I just don't accept that a front that passes in minutes could ever heat a brick to the point of the heat transferring to the timber. So, if the roof is the same with the same fire rating , then I question any difference. I have previously understood that most brick home destruction is caused by fire entry to the roof or eves, or more commonly, glass shattering..
I would have thought that radiant heat would have been the big initial killer, setting fire to curtains. The crimsafe shields would act like a miner's lamp, blocking that heat and flame.

IMHO
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Re: D.I.Y. Double glazing.

Postby zzsstt » Fri Oct 05, 2012 5:39 pm

A properly designed home doesn't have any significant exposure to heat - it has either (preferably) gravel or at worst short mown green grass for many meters on all sides, so there is no long term exposure to heat. Those houses built in the middle of a forest and surrounded by flammable materials will always suffer, almost regardless of their construction. Under these circumstances, resistance to blown embers becomes the main criteria.

I tend to agree with Tracker, exposure to heat that is severe enough for bricks to heat sufficiently to ignite whatever is inside them will also incinerate weatherboard, so in both cases the next layer of defense becomes important.
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Re: D.I.Y. Double glazing.

Postby Cherokee Solar » Mon Oct 08, 2012 8:09 pm

Tracker wrote:why a properly designed home in single brick or timber, would be any different


zzsstt wrote:A properly designed home doesn't have any significant exposure to heat


Mmmm, it is one thing to say "properly designed home", and another to actually go about designing, building and maintaining one. Or finding the time or energy to retrofit your existing one or modify your landscape to reduce your risk. The very first Grand Designs Australia episode was about a bushfire resistant house and it had huge expanses of glass which would allow for the transmission of radiant heat into the building. :shock: It also had trees overhanging the building which also increases the radiant heat load on the building should they ignite during a bushfire. Poorly designed and built outbuildings do exactly the same.

Tracker wrote:With the brick holes, they can be filled or stuffed with stainless pot scourer.


Yup, this is a possibility, but I am unaware of anyone who actually does this. Blocking the down pipes and filling the gutters with water may also help before an emergency. Cleaning gutters is not a high priority for most people though.

Tracker wrote:I just don't accept that a front that passes in minutes could ever heat a brick to the point of the heat transferring to the timber.


Don't take this the wrong way, but I recommend that you try not to confuse opinion and fact. Bushfire fronts are driven by the winds and they do in fact move very quickly in extreme scenarios. Once the front has passed however, you are still left with the super heated air and whatever fuel is burning around the house so it can be very difficult to tell when a front has actually passed. For your info a house can burn to the ground - once ignited - in under 4 minutes which is why people think houses explode. They don’t, they just burn really quickly. The trick to survival is slowing the rate of combustion through a strategy of layers and fuel reduction.

Tracker wrote: I have previously understood that most brick home destruction is caused by fire entry to the roof or eves, or more commonly, glass shattering..


Correct. Steel roofs are more bushfire resistant than tiled roofs. If you have a tiled roof then as an experiment, I suggest you climb into the roof cavity on a windy day and you will feel the air moving through the cavity. Burning embers will follow the wind. Tiles keep the rain off, but not the wind out. Steel may lift, but is vulnerable all around the edges which is why the roof system in the previous post has 15mm plywood and a fire blanket over the entire surface and also steel and mineral wool around the edges and openings. During a bushfire, it is not just embers, but also ignited branches that may be flung around by the wind - these often break tiles. These burning objects can be hurled from forests and grasslands well into the surrounding outlying suburban areas too.

Tracker wrote:radiant heat would have been the big initial killer, setting fire to curtains


Yup, modern homes have huge amounts of synthetic materials which are very combustible. Try natural materials like wool carpets and leather, cotton or hardwood timber furniture instead. Better still have woollen blankets to chuck over the top of stuff if there is ever a bushfire. Even crappy homemade zinc alum window shutters will help, but if your roof catches, it is pretty much all over.

zzsstt wrote:it has either (preferably) gravel or at worst short mown green grass for many meters on all sides, so there is no long term exposure to heat.


Grass fires are much more common than forest fires and they are also much faster, but cooler. Flame heights are generally 1.5x the highest point of the elevated fuel so distance from the house differs depending on situations and fuel loads. A couple of metres of non-combustible materials around a house won't make much difference if you have eucalypts hanging over the house and guttering full of dry leaves.

zzsstt wrote:Those houses built in the middle of a forest and surrounded by flammable materials will always suffer, almost regardless of their construction.


This is pure speculation on your part. I'd rather be in a well designed and built house in a clearing in the forest, than the average poorly maintained house surrounded by flammable grasslands. FYI, more houses and commercial premises burn in urban locations annually than in bushfires.

zzsstt wrote:exposure to heat that is severe enough for bricks to heat sufficiently to ignite whatever is inside them will also incinerate weatherboard


Perhaps. Mortar holds a lot of water. In a bushfire, the intense heat causes the water in the mortar to expand which then causes the mortar to crack and fail. If the mortar fails, then the internal walls are exposed and the brick veneer walls fail. Despite their appearances brick veneer walls are not strong. It is the pine framing via the brick ties which gives the wall its appearance of strength and rigidity. They are mostly not even very well sealed. Well maintained weatherboards will generally char, but in doing so, do not lose their structural rigidity. There are also many commercial products such as 16mm fire rated plaster which can sit under timber or fibrocement weatherboards which provide outstanding fire protection.

It may surprise you to learn that poly water tanks are actually not too bad in a bush fire as they melt to their water line but generally don't fail beyond this point so can still be used as a water source. Steel water tanks are a little more vulnerable because the plastic liners can melt and they are generally held only at the top point of the steel work. Concrete water tanks tend to fail for the same reasons that the mortar in the brick veneer wall may fail because the water heats and cracks and then the overall structure breaks. This is counter intuitive, but is how things work in the real world.

Stuff for you two to think about. Remember to try not to confuse opinion with fact as this is a common problem in our society and this topic is serious enough to not muck around with.

Chris
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Re: D.I.Y. Double glazing.

Postby Tracker » Tue Oct 09, 2012 10:22 am

Cherokee Solar wrote:Remember to try not to confuse opinion with fact .....

I would have thought that my comments would suggest total agreement..

I find it interesting that I have seen just SOOOooo many images after bush fires, where the only thing standing after a fire, is the BRICK WALLS.
Cherokee Solar wrote:Perhaps. Mortar holds a lot of water....the intense heat causes the water in the mortar to expand which then causes the mortar to crack and fail.....


Perhaps this is also an opinion, that does not reflect in those images of the brick walls, being the only remaining component of the home.. Were the owners remiss in not plugging the holes..?

Perhaps we should be forgetting the brick walls and the tiles and talking about just how you completely stop heat and ember ingress.. That does not sound like rocket science.. It simply means NO GAPS - NO WHERE...!
So if doors and windows were tightly covered with security mesh and if roofs were made of steel, with insulation under, and if sofits were tight and fire-proof, and if there were NO holes in the walls, and metal gutter-guard was used to prevent leaf buildup, then how would you rate the chances of that home, in surviving a fire-storm..
Then, if you were really trying, you would have shut off valves on down pipes and sprinklers on the roof, powered by batteries and with a generator as back up..
..
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Re: D.I.Y. Double glazing.

Postby bpratt » Tue Oct 09, 2012 9:46 pm

I think you'll find that the difference between a brick house versus a 'timber' house burning down isn't so much about what it was built out of, but other local conditions.

People let nature takeover their property, and let fuel build up near and around the house. Do that and the brick house burns, where the timber house with plenty of clearance around the house does not.
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Re: D.I.Y. Double glazing.

Postby Tracker » Wed Oct 10, 2012 7:41 am

.
That is largely what I was questioning.
I just can't accept that in identical settings of clearance, etc. That a single brick home would be less safe than another design.
Your fire readiness is largely what you make it, and claims that brick is bad is just dumb.. especially if it is qualified by talking about how bad holes are.... there should be no holes, either in brick or timber ..
If fire and embers can't get in, then time is on your side.
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Re: D.I.Y. Double glazing.

Postby Cherokee Solar » Fri Oct 19, 2012 4:15 pm

Tracker wrote:I find it interesting that I have seen just SOOOooo many images after bush fires, where the only thing standing after a fire, is the BRICK WALLS.


Tracker,

A brick wall standing after the rest of the house has incinerated is kind of pointless! ;)

Surely you can't be seriously suggesting that a brick veneer house burning down leaving a brick wall standing is a good thing or a good example of fire resistant building techniques?

The other thing about single skin brick veneer walls standing after a fire has incinerated the house is that it is usually only the corners of the buildings brick work that remains. The centre of those walls tends to fall in as they are no longer supported by the timber framework. Brick veneer walls look strong, but are actually quite weak and fall over if unsupported. Before you continue disagreeing, how about supplying some photos to back up your opinions?

Tracker wrote:there should be no holes, either in brick or timber ..


Unfortunately, brick veneer walls have loads of gaps. Weep holes, expansion gaps, it is really hard to seal around windows, doors, roofs etc. How about under eaves where they use fibro linig boards (4mm from memory) and join them with plastic strips (how long would they last in a fire)? Not to mention tile roofs. What about evaporative coolers (paper elements on top of roofs). Man, the list goes on.

Look, in theory what you are suggesting is possible, but in the real world it does not happen which is why embers get in to very dry roofs and frames.

Very few houses are well sealed. Talking about good design is one thing, but the average project house is just not good design. Transfer of heat is a real problem with the average house design in Australia, otherwise why would about 70%-75% of houses have air conditioning systems?
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Re: D.I.Y. Double glazing.

Postby Andrew_electrix » Fri Oct 19, 2012 10:59 pm

BAL-FZ (flame zone) requirements are very difficult to meet, the range of materials that are allowed to be used is very limited - brick veneer wall do not comply.

We live in the adelaide hills which is a fire prone area, our neighbour built a new house across the valley it's of rammed earth and steel frame construction, has double glazing, roller shutters, a flat roof without any ridges, it has an integral strong room, fire sprinklers and so it goes on...

The lengths that have been taken to make it ember proof and fire resistant is quite extraordinary, the average brick veneer suburban dwelling is not even on the same planet!

Our house on the other hand was built in the 60's when such requirements did exist, it does have a few things going for it - flat roof without any ridges or angles.
But the main problem is that it's up on steel poles due to the slope of the ground and the under house area is totally exposed to the weather, leaves can just blow in under the house and that's just bad.
My main focus at the moment is to close in the under floor area, I've built a low brick wall and on top of that will be light steel framing with flat cement sheeting and weather board cement cladding over the top of that.
The rainwater tanks will then be closed under the house with the diesel fire pump (i need to pipe the exhaust outside through) forming an integral protection system.

With bushfires it's about two things:

FUEL

As chris has correctly pointed out it's no good having a fire resistant building if it's sitting in the middle of a bonfire and there plenty of houses in the adelaide hills where people seem to be living in some kind of dream land...

THE CONDITIONS

Not every brushfire is as bad as black saturday with 50 degree temps and 100km/h winds.
A grass fire on a warmish day with a light breeze can still burn unprotected houses, but in these conditions, with the right preparations it's quite possible to defend your house in these conditions.
Recognizing the conditions and responding to them appropriately is part of living in a fire prone area, but a lot of people havn't a clue.

The classic is: i'll stay but then still jump in the car and go when it gets bad if I can see the fire threatening...

WRONG ANSWER

If the conditions are bad enough that you wouldn't want to be there if there was a fire, then the time to go is

BEFORE THE FIRE STARTS

If that's your plan, which of course has been well though out and rehearsed...

Haha

Regards

Andrew
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