# Polystrene and heatmats



## Musclynerd (Nov 3, 2011)

Hi ive now got some polystrene and which is 1cm thick and ive placed it underneath my exo terria terrarium. under my heat mat which is stuck underneath the terrarium. Im just wanting to know if this is safe, ive also been told that you can use polystrene to touch the heat mat and push it up to touch the glass directly. But ive also read that you need to leave air gaps otherwise it can be dangerious Im not sure what to do.


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## RepTech (Aug 3, 2011)

It is also partly depending on what type of substrate (and how thick a layer) you use and if the heat mat is connected to a thermostat.

If the heat mat is on 24/7 and you have an insulating layer of substrate in the viv you will need an air gap below your heat mat. Putting polytrene sheet below it will otherwise cause a great fire hazard. 

Please do not underestimate the risk! A (standard black type) heat mat of most brands will reach a temp of around 40°C on itself. This core temperature shoots up when the heat mat is insulated. Just putting it between 2 sheets of 4mm glass (which are poor insulators) will cause the core temperature to go up to 65°C+. Putting it between wood (often similar to adding a thick layer of substrate) is even worse and temperatures will go well over 120°C if no thermostat is used. Beyond this point it will start melting, causing short circuits and eventually fire.

I am not trying to scare you, I use heat mats on all my vivs. I just want to help you use them in a correct manner. In combination with a thermostat (sensor should be placed above the heat mat) the risk is already much lower. When the heat mat is used correctly and an air gap is provided the risk is as good as gone. 

Hope this helps


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## Musclynerd (Nov 3, 2011)

RepTech said:


> It is also partly depending on what type of substrate (and how thick a layer) you use and if the heat mat is connected to a thermostat.
> 
> If the heat mat is on 24/7 and you have an insulating layer of substrate in the viv you will need an air gap below your heat mat. Putting polytrene sheet below it will otherwise cause a great fire hazard.
> 
> ...


Well the problem ive been having is my ground temperature is only getting to 86-88f at max and I want it to be at at least 92, and its not even winter so if it struggles now then I thought its quite bad and best use something to help heat it up which ive read polystrene does.

I will definitly be using a thermostat when I get my leopard geckos but at the time being Im just trying to find a safe way of actually getting it to be able to get above 92f. Im only using a thin layer of vinyl flooring above the glass


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## Musclynerd (Nov 3, 2011)

Does any1 know what temperature the glass terrariums can get to before the glass would start to crack?


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## RepTech (Aug 3, 2011)

Well if you are trying to get the temperature to go up there are several things you can do. Using an insulating material is 1 of them, but this will increase the chance of something going wrong.

If the heat mat you are using is indeed a standard heat mat (which I suspect it is if the hot spot only reaches 31°C) there are few possibilities. 

First of all, heat rises. An exo terra terrarium has an all mesh top which holds no heat. It helps if you have a light top on there which will cover half. If not you can use a strip of cardboard to cover part of the top to see what difference it makes.

If you already have a lighting cover or someting like that on top covering about 50 to 70% of the top thats fine. Don't cover any more because it will ruin the ventilation.

A standard heat mat gives heat equaly on both sides. Knowing this will lead to possibility number 2  Use a reflective material (often aluminum foil will do the trick) and place under the heat mat. You can use a thin piece of cardboard as a backing for the refelctive foil so it is easier to place. This will force much more of the heat upward instead of downward where it has no use, yet it ensures that the heat mat is not over insulated.

Hope this gives you some other options


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## Musclynerd (Nov 3, 2011)

RepTech said:


> Well if you are trying to get the temperature to go up there are several things you can do. Using an insulating material is 1 of them, but this will increase the chance of something going wrong.
> 
> If the heat mat you are using is indeed a standard heat mat (which I suspect it is if the hot spot only reaches 31°C) there are few possibilities.
> 
> ...


Thanks for your advice, ive already got the light attachment thing on top that covers about 50% and then another reflective lamp that covers about another 15%, Im currently testing with this 1cm thick polystrene as we speak and ive noticed the heat is raising at a much faster rate then without. Im curious to see how high itll get.

But I am concerned about the potential fire hazard, I dont know why the manual has mentioned to use 6mm thick underneath if it can be potentially dangerious. And yes im using a standard 20w heatmat.

Also do you know how high the gap with the exo terriaum is of the ground?


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## RepTech (Aug 3, 2011)

Musclynerd said:


> Does any1 know what temperature the glass terrariums can get to before the glass would start to crack?


 
This does not happen at a certain temperature. It is highly dependant on how large the piece of glass is (and how thick). Glass does not transport heat well. Below an experiment I did e few years back.

Take a meter long sheet of glass and place a heat mat under half of it, place the entire thing on a piece of wood. The glass over the heat mat will go well over 55°C. There is a transition area of about 10cm and then the rest of the glass remains around room temperature.

Temperature differances as in the above experiment cause the glass to break. It is all do to tension within the sheet of glass. If you warm the entire piece of glass to 60°C (or even much higher) there are no issues with breaking. So it all depends on heat mat placement, heat distribution, size of the glass etc etc.


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## Musclynerd (Nov 3, 2011)

RepTech said:


> This does not happen at a certain temperature. It is highly dependant on how large the piece of glass is (and how thick). Glass does not transport heat well. Below an experiment I did e few years back.
> 
> Take a meter long sheet of glass and place a heat mat under half of it, place the entire thing on a piece of wood. The glass over the heat mat will go well over 55°C. There is a transition area of about 10cm and then the rest of the glass remains around room temperature.
> 
> Temperature differances as in the above experiment cause the glass to break. It is all do to tension within the sheet of glass. If you warm the entire piece of glass to 60°C (or even much higher) there are no issues with breaking. So it all depends on heat mat placement, heat distribution, size of the glass etc etc.


Oh right im basically using the 36" long exo terra terrarium. and im using a 17" by 11" heat mat.


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## RepTech (Aug 3, 2011)

Musclynerd said:


> But I am concerned about the potential fire hazard, I dont know why the manual has mentioned to use 6mm thick underneath if it can be potentially dangerious. And yes im using a standard 20w heatmat.
> 
> Also do you know how high the gap with the exo terriaum is of the ground?


 
I'm not sure how large the gap is below an exo terra viv, so can't help you there.

As for the user manual supplied with the heat mat: Perhaps the producer makes these to a different spec than I am used to? If the manufacturer states that it is OK to use insulating material on both sides I guess it should be OK. 

I have my own brand of products, including heat mats, on mainland Europe. Due to all the testing I've done I am very carefull to give an ok for insulating a heat mat. If you have a brand that makes mats that run "cooler" than perhaps it is possible. 

What are you using to measure the temperature? And how long was the set up running before you concluded a max temperature of 88°F?


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## Musclynerd (Nov 3, 2011)

RepTech said:


> I'm not sure how large the gap is below an exo terra viv, so can't help you there.
> 
> As for the user manual supplied with the heat mat: Perhaps the producer makes these to a different spec than I am used to? If the manufacturer states that it is OK to use insulating material on both sides I guess it should be OK.
> 
> ...


I left it for about 6 hours to get to about 86.5. 

As we speak its already got to 88 and its not even been on for a hour with the polsyrtene underneath. Im measuring the heat by using a digital thermometre ontop of the vinyle flooring.


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## RepTech (Aug 3, 2011)

As long as you keep an eye on it you can leave it on and see where it goes. If it goes too high I suggest the reflective foil method I mentioned earlier as it has a much lower risk.


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## Musclynerd (Nov 3, 2011)

RepTech said:


> As long as you keep an eye on it you can leave it on and see where it goes. If it goes too high I suggest the reflective foil method I mentioned earlier as it has a much lower risk.


Im already abit nervious its almost at 90 already. I am using 4mm thicker polystrene then I should be. There might not be much air space. Should I see if I can some how cut the polystrene down to liek 4mm and use tin foil on it? Even though the polsyrtene prob crumble to bits lol


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## RepTech (Aug 3, 2011)

Cutting it down won't work haha. It will crumble, so besides just frustrating yourself you will also have a great mess to clean up.

Just see where this goes in another hour or 2. If you think it is getting too hot just use the foil and cardboard method. Saves you some cleaning and should have a similar end result as using the poly sheet but at a lower fire risk.


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## Meko (Apr 29, 2007)

Musclynerd said:


> Im already abit nervious its almost at 90 already. I am using 4mm thicker polystrene then I should be. There might not be much air space. Should I see if I can some how cut the polystrene down to liek 4mm and use tin foil on it? Even though the polsyrtene prob crumble to bits lol



90f isn't even as warm as holding something in your hand. I've never had a problem with a heat mat on polystyrene


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## Musclynerd (Nov 3, 2011)

RepTech said:


> Cutting it down won't work haha. It will crumble, so besides just frustrating yourself you will also have a great mess to clean up.
> 
> Just see where this goes in another hour or 2. If you think it is getting too hot just use the foil and cardboard method. Saves you some cleaning and should have a similar end result as using the poly sheet but at a lower fire risk.


Its been nearly 3 hours and it got to 97 so if I left it all the time I wouldnt be surprised if it could reach above 105 which is quite dangerious?

And by using cardboard do you mean just regular cardboard because id of thought thats abit dangerious to even know you have the foil wrapped around it?


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## Musclynerd (Nov 3, 2011)

Meko said:


> 90f isn't even as warm as holding something in your hand. I've never had a problem with a heat mat on polystyrene


Yeah but it didnt take it long to get to that temp thats what I was getting at...


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## Wolflore (Mar 3, 2010)

Why not use a ceramic in a reflector on the top? Much safer!


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## RepTech (Aug 3, 2011)

Just regular cardboard  Because of the foil you force heat up (and away) from the cardboard. It also doesn't hold heat as much as the polystrene board.

A thin piece of cardboard will do, it just needs to be thick/stiff enough to hold the foil and keep its shape.






Musclynerd said:


> Its been nearly 3 hours and it got to 97 so if I left it all the time I wouldnt be surprised if it could reach above 105 which is quite dangerious?
> 
> And by using cardboard do you mean just regular cardboard because id of thought thats abit dangerious to even know you have the foil wrapped around it?


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## scottology (Aug 8, 2008)

sorry to hijack, but I'm sure I read somewhere to use thin sheets of polystyrene to send all the heat upwards into the viv so none is wasted?

I'm looking at getting a wooden vivexotic (after payday this month) with heatmat placed inside the viv on top of a thin piece of polystyrene, obviously using a stat. (Slightly different to the glass exo-terra) and ideally will be looking to use natural "sandy" coloured slate tiles as a substrate.

Would what you are saying above, be equally as dangerous (i was looking at the same spec heatmat) or do the tiles spread the heat better so it wont get as hot? Should I not bother with a layer of polystyrene?


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## RepTech (Aug 3, 2011)

A thin sheet is already better than a thick sheet  

I've done extensive testing and I get a lot of feedback from customers/stores when things go wrong.... (such as broken glass)

I've tested standard black heat mats between two pieces of 18mm plywood. This seemed ok but after a few weeks (yes it can take a long time to build up the heat) it got too hot. After adding a layer of substrate it went wrong and caused a fire.

Running heat mats between 2 herptek terrariums without a thermostat worked fine. When I added a piece of wood (MDF in the Netherlands) (many people do this between layers of herptek terrariums as a stabalizer) it causes the heat to be forced upwards and the wood itself will get hot as well. With a layer of substrate in the herptek it caused the herptek to melt resulting in what would eventually be a fire.

Running heat mats with insulation at the bottom end forcing all the heat up under glass can cause issues with glass breaking. When there is water in the viv (or e very wet substrate) heat will be distributed and the problem is less likely to occur. 

When working with a wooden viv it is best to place a heat mat on the inside. Wood itself is a good insulator and you will not need additional polystyrene sheets. Placing a thin piece of slate on top of the heat mat will be sufficient. Try not to add a thick layer of substrate over the slate as it may overheat the mat.

All of the above situations are not an issue when using thermostats! A thermostat (when the sensor is correctly placed) will turn of a heat mat when the desired temperature is reached. 

Also when the tests were repeated with a small air gap (3mm) at one side of the heat mat, there were no issues. Even when using them without a thermostat. 

There are many people that use heat mats in a manner that I would clasify as incorrect use but they have no issues at all. However they are probably working on the edge of "safe" use and something as simple as a warm summer day or forgetting to keep humidity up may be enough to cause a failure. 

Please remember that heat mats do not raise air temperature in the viv all that much. The infrared radiation heats only mass that is on eiter side of the heat mat. It makes for an ideal night heat source, back up heat source or hotspot heat source but is not suitable for heating larger vivariums by itself. It can be used as a main heat source if the room is heated. I have a reptile room that is heated to 25°C, I use heat mats as a heat source for all the vivs in this room as they only need to create a hot spot.

They are also very well suited for use in rack systems though because of the low height of the living space.


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## Hashcake (Nov 23, 2011)

I have 3 strips of polystyrene between the stand and heat mat to help keep the heat mat flush as tape alone wasn't doing the trick.
I use roofing slates for substrate which, I'm sure is thicker than the lino you are using and the surface on the warm side temperature is a constant 31C.

When I first set it up, if I remember correctly, while I was waiting for the thermostat to be delivered, I couldn't get the correct temperature and it was too low.
Don't quote me on this but I remember thinking it was strange at the time as I expected the mat on it's own to reach a decent temperature (I always intended on using a thermostat regardless).


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## Dan Trafford (Mar 10, 2011)

I did exactly this, polystyrene under my mat then under the tank. I had no problems. But get a stat.


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## Musclynerd (Nov 3, 2011)

RepTech said:


> A thin sheet is already better than a thick sheet
> 
> I've done extensive testing and I get a lot of feedback from customers/stores when things go wrong.... (such as broken glass)
> 
> ...


Im testing now with a thin layer of cardboard wrapped in kitchen foil. It seems to just barely manage to get it hot enough but it is struggling slightly ill give it some more time though.


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## Musclynerd (Nov 3, 2011)

It isnt going above 92f, which I know with a thermostat it shouldnt anyway but I want to know it can easily go above it for when its winter.


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