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Rebuilding after the bush-fire holocaust

mike's picture

As you can imagine, as a building designer, even a retired one, I've been thinking about this a lot. All the talk of rebuilding at any cost, a kneejerk reaction I believe to make things look like we are all right behind those poor buggers who've lost everything (and we are, don't get me wrong) is not a good idea.

An opportunity not to be lost

This disaster is, in my opinion, an opportunity not to be lost. I would be extremely surprised if 99% of all the homes lost in the Victorian Bush were not totally inappropriate for the conditions. What I see on TV tells me those places were built for life STYLE, not life REALITY.

Take all those fireplaces left standing, ghostly reminders of what used to be. Notwithstanding the fact that it probably gets very cold there in winter, those fireplaces were built for LOOKS. They are probably viewed as 'pre-requisites' by tree changers building their 'dream home', when in fact they are appallingly inefficient in both heating a house in winter (most of the heat goes straight up the chimney) and keeping a house cool in summer when cool internal air is drawn up the chimney by convection, sucking in hot air from outside. The solution to that of course is to turn on the aircon. When energy rating a home, introducing a chimney immediately removes a whole star (sometimes more) from that rating.

In fact, I am fast starting to think that all the things that make a house energy inefficient also make it more prone to bush fire destruction.

How well insulated were all those homes? How large were all their windows? Were they built out of bricks? How many were built off the ground?

Chimneys would, I think, cause a draft from the outside into the house, possibly even bringing embers into the house, particularly through gaps in eaves etc. If a possum can get into your roof, just imagine how many embers could get in!

Now also imagine how hot bricks and tiles would get in a fire ball. Well over 200 degrees I would guess. That heat, radiated inwards, could easily set the frame on fire unless incredibly well insulated
(well beyond what is required to control regular heat flows on a day to day basis).

I'm also wondering how many of these houses might have been built with steel frames to avoid termite problems. Steel frames conduct heat from the outside of the envelope to the inside very effectively. I have experienced this first hand when a friend built a house I designed out of steel, and then complained, when I expressly told him this would happen, that the studs could easily be identified through the walls as bars of heat... That was the western sun, making maybe 30 degree heat. Now convert that to 200 degree radiant heat.....

It is also a long lasting fad to have huge glazing in modern houses to bring the inside to the outside, especially in places with views such as the Victorian forests would offer. Glass has virtually zero insulation rating, and allows radiant heat unobstructed entry. It's not outside the realms of possibility that when the fires struck, inside temperatures could have reached the dizzy heights required for some things to combust instantaneously, burning the rest of the building in the process.

And finally, quite a few of these homes were built on posts, allowing heat and flames even, to gain entry under floors. No prizes for guessing the result of this surmising.

Solutions

Solutions? Well there are in fact quite a few. Like building within the earth itself, or with thick rammed earth, limiting glazing to no more than 10% of the floor area, heating with combustion heaters instead of
open chimneys, heavy insulation, and I think heavily insulated metal barriers for windows in emergencies. These could even be used in extreme weather like when it snows, or temperatures reaching nearly 50 degrees, something likely to happen more and more as Climate Change starts to bite.

These solutions would not only save homes, they would also save lives.

Mike

Mike Stasse is a retired Energy Efficiency and Sustainability Consultant, and is a qualified Building Energy Rating Assessor. www.greenhousedesign.green.net.au damnthematrix.wordpress.com

See also: "Fire bunkers could have helped in the Victorian fires" of 10 Feb 09

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Comments

The sprawl of suburban style allotments spread through the bush is also a huge factor. There's zero focal purpose at work to define the shape and extent of the total housing footprint.

A genuine village structure provides a perimeter within and around which zones for production and fire protection can be arranged. Thus the bush can be kept healthy, accessible but separate to the living and property envelope.

Last week's catastrophe was yet another holocaust erupting out of the abysmal greed and stupidity of the 'free' market. Villages, by definition, present limits. The 'free' market abhors limits, as it abhors physical reality in general.

Hi,

The notion of a fire bunker is a common sense one. As we've seen, fire bunkers were at one time a commonly used safety measure in rural districts, especially around logging camps. They came about as a result of the understanding that at the worst moment there must be a fire-proof location for the period that it takes a fire to rage past.

Just one simple idea. A two metre by two metre diameter cement tank, sunk to 2.5 metres. A cement floor, cement roof covered by soil. A cement access tube with ember resistant ventilation.

This is the critical point. A fire of the ferocity we've witnessed in Victoria will only be present for a limited time - perhaps an hour. The application of common sense reveals that a subterranean space, large enough for 4 or 5 people, equipped with water, will serve to save lives. Whether this is beneath the house or immediately adjacent may not matter. It is a fascinating and odd fact that in a country where fire has killed so many the idea of a "basement" is still somehow seen as something they only do in other countries! Think of it as life insurance.

With thoughts to all those suffering in this terrible time.

Dan

Mike,

I wish to pick you up on a few points in regards to your comments.
Steel Framing is in fact, NON combustible, and hence is the perfect framing material for bush fire resistance.
Bushfires burn down houses in the 60 minutes after a flame front, or fire ball has passed. Embers make it into the roof space and wall space, ignite the timber framing, and hence burn the house down structurally from inside the walls.
Find photos of the Horsham golf club and you will see steel stuf frames, which have in fact kept the building up. Yes, the cladding on the outside has burnt, but the structure is still safe.

Bricks heating to 200 degrees would not create a fire. Even timber will not ignite at this temperature. The bricks only get this hot during a fully fledged fire, not during the inital fire ball. Also, interior plastics and synthetics require considerably higher temperatures to spontaneously combust.

The way to stop fires getting into a house relate very closely to making a house energy efficient.
Double glazing, Aluminium window frames well sealed into the cladding, Steel door frames with good sealing properties, sarked roof and walls and proper thermal breaks between frame and cladding.

Your mention of a steel framed house creating walls that were hot means that the house was not built with the required thermal break between cladding material and frame, and without proper insulation in the walls. Put this down to the builder, not the materials.

New cladding materials such as sandwich panels (steel on the inside and outside surface with Polystyrene, Poly Urethane or Compressed Straw (OSSB) panels) are all fire retartdant and also emormously well insulating, think R5-7 just from a board. An Esky keeps ice as ice for many days with sealed to the outside air, and panels like these are just as efficient at keeping temperautres as you want them. These panels can be made to look like normal steel roofing and walling but provide incredible insulation.

Bricks are a 50/50 solution. They take a long time to heat up, but also take a long time to cool down, often transferring the heat into the house at night. However, because they take so long to heat up, they are also a good insulator against the fireball, allowing people to stay in a well protected house during the fire ball, and then exit the house to extinguish the spot fires and the material around the house. It's these fire that are left after the fire ball that do all the damage.

My solutions to fire retartdant homes are not dissimiler to yours, I only wish to correct you on a few points.

Kind Regards

Peter Blythe

mike's picture

"Steel Framing is in fact, NON combustible, and hence is the perfect framing material for bush fire resistance."

Of course, but you're wrong... steel frames do not combust, but they buckle and melt. Once buckled, the roof will come down, whereas a burning wooden frame, whilst weakened, will remain upright, and it's not until the studs are fully burnt that the roof would collapse. A friend of mine who works for the Bushfire Brigade here in QLD was told during training that a steel framed house will collapse twice as fast as a wooden framed one, and that they should never enter a steel framed house on fire.

Plus, the point I was making is that steel frames conducts heat so effectively, they can set the INNER linings on fire, even if the walls and roof are insulated, because the insulation is inserted between the frame sticks. I agree that thermal breaks would work, but in fact I've never seen this in practice. Polystyrene can burn if heated sufficiently.... and the fumes are toxic, maybe not your worst problem if your house is alight, but fumes might kill you if you're trying to save your house.

"Embers make it into the roof space and wall space, ignite the timber framing, and hence burn the house down structurally from inside the walls."

Only if the house is poorly sealed. A well sealed steel framed house would ignite the interior as described above. Pine WILL ignite at 220 degrees, info from plantation timber book I have here... can't find web link, sorry.

As far as bricks are concerned, I would only have double brick. All the brick veneer houses I've seen on TV (I'm in QLD) all fell down.... end of story as far as I'm concerned. BTW, aluminium window frames MELTED in the recent fires. Again, I would prefer timber frames., but shutters would be imperative I think.

Mike

Mike - I agree with what you say and very interested in your ideas for window and glass door SHUTTERS. We would like to make our own lightweight fire shutters - I was thinking a frame with some highly R rated insulation in it that we could fix over our double glazed windows etc on TFB threatening days. It will make it very dark and we would leave couple of doors/windows uncovered for light etc until necessary. comments please??

Carole

Steel does not melt or buckle in a house fire until the fire reaches a consistant 700 degrees of transferred heat.
It would be a rare occurance that a steel framed house would have enough timber and combustible material inside it to be able to transfer that level of heat.

After speaking to many MFB and CFA people in Melbourne, they are of the opinion that a steel framed house is considerably safer than a timber framed house in this situation.
One of the reasons is that during the last 15 year or so, many more houses with timber frames have the trusses manufactured using "Gang Nails" which are the plates with many small (10mm long) 'nails' punched out of them, which in a fire are extremely dangerous, and they are pine.
The old method of 'pitching' a roof, and normally in Hard Wood, was to make the trusses on site using long nails and correct techniques, but these days 'pitching' is almost non-existant. The Gang Nail connection fails because the little nails heat, and bend/melt/seperate much quicker than the old thick nails and the roof collapses insted of slowly burning out. MFB wont go into a burning house in a new estate for that very reason, they are simply too dangerous.

Your stating that the house wont collapse until the studs fail is also incorrect, as the roof trusses, carrying 60kg/m of clay tiles fail long before the timber studs have burnt out, thus collapsing the roof into the house.

Sealing the house and proteting it from the ember attack is the most important thing. The Aluminium winder frames only melted because they were subject to the heat of a house burning to the ground, not just the fireball.

Most of the houses that burnt in the recent fires were not built for fire safety, which is the reason we are having this discussion. I've seen many images of single brick and double brick construction, some standing, more not. The single bricks normally fall over because the brick is only vaneer and when the rest collapses, so do the bricks. If the frame doesn't collapse then the bricks don't either.

There was also a brief interview with a family who had a conder block shed that they hid in whilst the fire ball came through and they exited afterwards and saved their house from the fires that remained. This is the key. Endure the fireball in a safe location, fight the fire that will burn down your house.

Pete.

mike's picture

"Most of the houses that burnt in the recent fires were not built for fire safety, which is the reason we are having this discussion. I've seen many images of single brick and double brick construction, some standing, more not. The single bricks normally fall over because the brick is only vaneer and when the rest collapses, so do the bricks. If the frame doesn't collapse then the bricks don't either."

The only brick walls I've seen still standing were double bricks, and I'm afraid you are wrong about the bricks falling down after the frame burns, it's the other way around. I've seen this in ordinary fires, let alone the much hotter bushfires. It's the mortar that fails, literally exploding in the heat. The bricks then just collapse.

Mike

A pessimist is a well informed optimist

Why so much focus on building and with so many restrictions eg. window size.

Most of the housing in the bush is existing so new standards are irrelevent to them. It doesn't seemt o matter a huge hill of beans whether you have wood or steel frames, they both tend to burn down anyway. Double brick may be a bit better but is more expensive, not currently offered by volume builders and not going to help in existing homes.

Seems to me that a few modifications to existing homes will give far more bang for your buck. Eg. I went out and brought $300 worth of cement board and some dynabolt hooks. This allowed me to cover my windows. This will not stop all the heat reaching the windows but may reduce the radiant heat getting into the house. Spray and misting systems while not perfect, are potentially relatively cheap way of reducing spotting on the outside while cooling the structure somewhat.

I would like to see a ceiling space intrusion detection system linked to a fire suppressant system (foam or CO2 (tho CO2 would need to be deactivated in non fire danger periods for safety)). Fire fighting hoses and pumps together with protective clothing would complete this picture.

Finally an underground fire shelter as a last line of protection could be standard and easily retrofitted especially if a decent sized rebate was available from the government. Bunker buried under 65cm of soil with an access tube would provide assurance that the hatch can be opened even with fallen trees across the opening. Fire proof rated door in the bunker and a piece of cement board that can be dragged across the top opening to reduce radiant heat on the fire proof door. Shelter should be sealed and compressed air and CO2 scrubbing unit just in case exit is delayed or larger number of occupants than planned. Basics like water, radia, light, burns, EPIRB etc ket in shelter. Shelter would be lockable from outside but overideable from inside.

Use of something like Barricade ( http://www.barricade.com.au/1250250/barricade-fire-blocking-gel-home.htm ) on nearby foilage would also have the potential to reduce or eliminate the amount of heat directed at the home.

With all these defenses and a bit of common sense, we can have homes with less compromise and still be safe. Reducing window sizes and cutting down trees is a primitive reaction and ill thought out given that most people live in the bush to be able to have large beautiful views and magnificent trees nearby. We are clearly not out of options to retrofit existing homes and keep the benefits of bush living.

I think your idea of the hooks and cement sheeting to protect the windows is a GREAT idea!
For existing dwellings, this sort of logical thinking it what we need.

I remember when we had that gas shortage a few years ago, everyone came up with clever little ideas for having a hot shower.

We should be thinking along the same ways with fire safety.

However, we have been discussing the ways to RE-build houses that have been destroyed.

I'm sold on a bunker/basement also.

I don't agree with the "mortar exploding" argument. As a son of a brick layer I know a brick wall can sustain very high temperatures. A brick fire place for instance sustains very high temperatures for hours let alone the 15 to 30 minutes of the initial passing of the fire front. Most destroyed brick houses are caused by the fire burning the internal structure of the house first. In a bush fire this is caused by embers gaining access. I do agree with Peter with building materials, the house only needs to resist the extreme heat for no longer than 30 minutes.

I heard from a builder that the best fire-proof building material is adobe bricks. However, it's too easy to make and not profit-making enough, so this material is not being promoted as it should. Can anyone confirm this?

The CSIRO tend to agree with me in this regard also.

Please note, this has been taken from the NASH buyers guide to steel framing.

"
FIRE SAFETY
• Building materials for a high fire-resistant home
• Steel frames top CSIRO recommended list
• Design and floor plan suggestions
• Tips to prevent accidents and limit damage

No home can be completely fire safe but there are a number of steps you can take to plan for a house which has a high resistance to fire.

Your choice of building materials is one way to improve your chances of establishing a fire-resistant home. This can influence how quickly and how seriously your house is affected by a fire, and whether your home could be repaired or would need to be completely rebuilt.

CSIRO, Division of Building Research, Victoria, produced a paper1 outlining the features of a high fireresistant house. Major considerations include:

• steel wall frames, with gypsum board linings* for further protection;
• concrete slab floor;
• the elimination of timber** in the roof;
• brick veneer external cladding.

*Although steel is not combustible, it will eventually lose strength at temperatures in the 400-500 degrees Celsius range. Gypsum linings with reliable resistance to fire will protect the steel frame.

**The elimination of timber in the roof is a most important feature because, when a roof catches fire, the burning rafters fall down the space between the walls, which acts as a chimney, producing an intense local fire. (White pine ignites at 280°C)

In the event of an external fire threatening the house, a bushfire for example, the main focus is to prevent sparks from gaining access to the building, principally through the space above the ceiling and from the space below the floor.

A steel roof (Corrugated Iron) simply cannot burn. In addition, the long lengths and tight overlaps prevent the entry of fire even when burning embers fall on the roof. Coverplates or closure strips seal off the small openings at the end of steel roofing profiles.

The space below the floor can be eliminated by building on a slab of concrete laid directly on the ground.

mike's picture

• steel wall frames, with gypsum board linings* for further protection;
• concrete slab floor;
• the elimination of timber** in the roof;
• brick veneer external cladding.

REALLY? How old is this information? I agree with the slab floor and eliminating timber in roofs (ESPECIALLY the gang nailed trusses), but brick veneer? Are they SERIOUS? Every brick veneer house I saw on TV had just fallen down.... The mortar explodes, and the bricks colla[se, after which it doesn't matter what your frame's made of, you can kiss your house (and your life) goodbye.

If I had my way, I would BAN tile roofs altogether and close all the factories down, as they are totally and absolutely inappropriate for Australian conditions. Thermally, for bushfire protection, in cyclones, in hail storms, you name it, they are a disaster. I once observed a really serious storm at my parents' place and the ONLY roofs to blow away were tiled, and each tile turns into a deadly missile.

If I were to build in Victoria, it would have to be bermed construction, or Hebel with steel roof. There is no way I would build a conventional house anywhere near a bushfire prone area.

A pessimist is a well informed optimist

This comment was posted through the contact form - JS

In the rebuilding effort has any suggestion been made to introduce the
German Passivhaus building standard into the new building requirements?

This standard, rapidly gaining momentum across Europe and the US would be ideal for consideration here and now.