Suspended floor insulation,Kingspan or Celotex, help wanted?

[getcarter]

I have a Victorian property with suspended floors. I want to insulate the floors and have found out about Kingspan and Celotex rigid insulation. My query is: Does anyone have any experience of these products in terms of which make, which product, fitting, etc etc.

Any help on this subject would be gratefully recieved.

Thanks

 

[Penners]

I have no direct experience of either, but both products seem to be well regarded. Surely your choice should be based on the best insulation values for the money laid out.

 

[middi]

Rigid isulation sheets come in a variety of thickness and extremely easy to cut ro size, use either a long bladed stanley knife or, better still, any wood saw.

For it to be fully effective once a tight fit is effected between the joists either use aluminium tape to seal the edges against the joists or use foam insulation spray as a " bead seal".

Buy the thickest size that will fit between the joists, the thickness is commensurate with insulation value.

 

[Mark]

and they both have similar properties. their k value being half that of rockwool making them much better as insulation.

A tip - depending on where you are - a friend of mine lives in Hereford and says that the kingspan factory sells seconds at very very cheap prices (he's even seen it being given away free). I think you have to take it by the pallet load, apparently they advertise this in the local paper.

 

[Penners]

Click here

(I've never done business with them myself).

 

[getcarter]

Thanks for all your tips and help on this guys.

 

[arthurw3]

A much better more cost effective material is expanded polystyrene. e.g. Jablite. Also you do need to do a cost benefit analysis before putting loads of insulation in. I suspect that you will find that 50mm is the most cost effective. Do remember that the temperature under the floor is going to be higher than external and that your room temperature at floor level is going to be lower than the overall room temperature, thus reducing considerably the temperature differential between inside and outside at that point and making insulation less cost effective here.

 

[MdB]

Anybody know what the flammability of Kingspan / Celotex is like? I know expanded polystyrene is terrible in fires, is Kingspan / Celotex as bad?

Also you don't want expanded polystyrene coming into contact with any wiring as it can cause the insulation to fail and possibly start a fire.

 

[middi]

Polystyrene is lethal anywere near fire. Celotex is fire retardant and when eventually catches fire it does not burn like the ferocity of polystyrene. ( I tested them side by side on a bonfire ! ).

 

[Penners]

you don't want expanded polystyrene coming into contact with any wiring as it can cause the insulation to fail and possibly start a fire.

Really?? Is there some sort of chemical reaction between the expanded polystyrene and the cable insulation? If so, I'm surprised this isn't given more publicity.

 

[MdB]

A quote I found on the web:

the common plasticisers used in PVC tend to be more soluble in polystyrene and polyurethane insulating materials and as a result, where there is a continuous direct contact between the two materials, plasticiser migration will occur. This causes the PVC on the cable to become harder and more brittle.

 

[MdB]

Polystyrene is lethal anywere near fire. Celotex is fire retardant and when eventually catches fire it does not burn like the ferocity of polystyrene. ( I tested them side by side on a bonfire ! ).

That's useful to know. Thanks.

Basic rule - Don't use Polystyrene for insulation.

 

[Mark]

tbh I thought that polystyrene was only used under screed these days. The idea of using it elsewhere is mad for all the reasons given above.

The thing about electric cables is well known to electricians. Polystyrene is also used for retrofit cavity wall fill - and the installers ought to check for cable in the void before installation.

 

[arthurw3]

Both polystyrene and polyurathene give off toxic fumes when heated. Sticking them on a bonfire is NOT a scientific test. Why is your underfloor insulation likely to catch fire more easily than say your nice nylon carpets, which will also give off toxic fumes. As far as not having PVC cables in contact with polystyrene insulation the rule is that you should have all PVC cables in conduit when taken through styrofoam insulation. Also any cables taken through insulation will likely need derating to allow for an increased build up of heat. Polystyrene insulation is regularly used for floor, roof and wall insulation without any problems.

 

[Mark]

Under screed isnt likely to catch fire, but between floors or as internal wall insulation it is.

There is a massive difference in flamibility between polystyrene and kingspan/celotex. Yes they will both give off fumes when heated, but if they are exposed to flame there is a big difference. Jablite has retardents added but is still more flamable I think. Hence the handling advice to avoid storing with anything flamable.

Also of course the thermal conductivity isn't very good - its on a par with rockwool.

 

[middi]

I agree with Mark.

I did not need to evaluate the scientific aspect between the two products when " tested" on a bonfire, the plystyrene nearly exploded after a few seconds. I am sure that the toxic fumes will kill you from both products, the argument here is which one will give you a chance to walk out of the house.