Green Building Forum - Polystyrene Beads - Timber Suspended Floors

Polystyrene Beads - Timber Suspended Floors

Victorianeco — Thu, 16 Jul 2015 17:55:40 +0100

A company we use to remove old EPS beads from cavities in problematic houses has said I can have the extracted beads free of charge.

I was thinking of using these to insulate my timber suspended floor prior to UFH pipes going in.

My question is if these beads are damp prior to fitting where will all that moisture go?

Or am I better off buying new beads?

Ideally the free factor along with recycling appeals to me greatly as I think it will save me ~Â£500

Thanks

Polystyrene Beads - Timber Suspended Floors

Mike George — Thu, 16 Jul 2015 18:07:42 +0100

The moisture will condense on any surface which is at Dew point. Where that is or may be is pure conjecture without a full (destructive) survey of what's there. A Condensation Risk Analysis is not reliable. Neither is a WUFI Simulation. Others will disagree though - Loads on here - an old skeleton that's been well and truly picked over.... :)

Polystyrene Beads - Timber Suspended Floors

fostertom — Thu, 16 Jul 2015 19:24:19 +0100

Wouldn't it be safe to say that once the beads are packed in, the timber floor/joists will be the very last things within the void to get to dewpont temp? They'll always be warmer than whatever is the coldest surface within the void, where any condensation will happen. Condensing-out on that 'condensing plate' will surely put a limit on how much water vapour there is within the void.

I'd say it's a fine way to keep the floor timbers much drier than they would be if facing into an empty void, whether through-ventilated or not.

BTW, can't imagine how 1D WUFI would model this very 3D (or 2D slice) situation.

Polystyrene Beads - Timber Suspended Floors

Mike George — Thu, 16 Jul 2015 20:03:25 +0100

Posted By: fostertomWouldn't it be safe to say that once the beads are packed in, the timber floor/joists will be the very last things within the void to get to dewpont temp?

But not where the timber joists are embedded in an external wall with a steep temperature gradient to the outside..............Also where wooden wall plates are sat on colder masonry stub walls (though I agree this is less likely)

Polystyrene Beads - Timber Suspended Floors

fostertom — Thu, 16 Jul 2015 20:31:20 +0100

Posted By: Mike GeorgeBut not where the timber joists are embedded in an external wall with a steep temperature gradient to the outside

True, but these days I think of EWI carried down in trench to bottom of founds, becoming a french drain.

On one recent uprate-extg job we did that, but left the u/floor void empty, blocked the through-ventilation. The Bldg Insp accepted the principles - "my husband is a physics teacher"! It meant that the whole ground floor, carpets, kitchen etc could remain undisturbed, inside the 'coffer dam' of downstand perimeter EWI. I reckon an effective whole-floor U value of 0.35, legal under L2 and much-more-than compensated by near-PH standard everywhere else.

On another job we surrounded the new shallow timber ground floor structure in Leca just deep enough to encase the timbers, no through ventilation, no other u/floor insulation other than the surrounding downstand 'coffer dam' of u/ground EWI extended downward in slit trench. The Bldg Insp accepted the argument I presented - I'll send the sheet pdf to anyone if interested.

Both have the effect of coupling the thermal mass of the subsoil within the 'coffer dam', to the interior, a massive stable temperature-moderator, its upper layers nearly up to room temp in winter and slightly cooling in summer. It takes a year of so for that mass to 'fill up' with heat, both from the winter heating system and from summer solar gain through windows.

Polystyrene Beads - Timber Suspended Floors

Mike George — Thu, 16 Jul 2015 20:55:26 +0100

Yes, I can see EWI will make a big difference to the dynamic in your scenarios. Though insulating the void at all then seems to become a low (if any) gain exercise? My only concern would be if the timbers were already degraded... say with wet rot

Polystyrene Beads - Timber Suspended Floors

tony — Thu, 16 Jul 2015 21:30:36 +0100

I would have no hesitation about using damp or wet beads, they will dry out and the moisture will move from warmer to cooler, into the ground.

Do it, I will even help,and I want the contact number for the beads too please

Polystyrene Beads - Timber Suspended Floors

EasyBuilder — Thu, 16 Jul 2015 22:23:46 +0100

Don't think I could do this to my house as polystyrene is supposed to rot electricity cable sheathing.

Polystyrene Beads - Timber Suspended Floors

Victorianeco — Fri, 17 Jul 2015 09:41:36 +0100

I think I'll do this, so a few questions...

1. What do I cover the cable in?
2. If I block up the floor vents, do I just use a similar brick and cement it in?
3. As I intend to use UFH, shall I just make a 1&amp;quot; biscuit mix straight on to an Osb board between joists to be on the safe side? Or not bother and just run the ufh pipe clipped to sides and one in between joists?
4. No need for a vapour barrier? If the vents are sealed up?

Thanks

Polystyrene Beads - Timber Suspended Floors

Saint — Fri, 17 Jul 2015 18:09:54 +0100

Posted By: tonyI would have no hesitation about using damp or wet beads, they will dry out and the moisture will move from warmer to cooler, into the ground.

Do it, I will even help,and I want the contact number for the beads too please

Not at all sure. What mechanism will assist them to dry out? The reason they've been removed surely, albeit from a smaller space, is because they didn't dry out. Wet insulation doesn't insulate and it will certainly stop water vapour passing through it.
Why not just buy bags of dry beads and give yourself a good chance? They're about Â£70 per cubic metre (retail)

Polystyrene Beads - Timber Suspended Floors

willie.macleod — Fri, 17 Jul 2015 19:36:04 +0100

Would expect these beads to be bonded together? Are they really loose fill?

Polystyrene Beads - Timber Suspended Floors

fostertom — Fri, 17 Jul 2015 20:49:26 +0100

Posted By: SaintWhat mechanism will assist them to dry out?

Diffusion in warmer, drier conditions, no more rain wetting.

Posted By: SaintThe reason they've been removed surely, albeit from a smaller space, is because they didn't dry out

when continually re-wetted by rain penetrating the cavity.

Posted By: SaintWet insulation doesn't insulate

does, quite well.

Posted By: SaintWet insulation ... will certainly stop water vapour passing through it

Why should it? (not saturated with standing water).

Posted By: willie.macleodWould expect these beads to be bonded together? Are they really loose fill?

Even if a bit clumpy, still good almost-free insulation.

Polystyrene Beads - Timber Suspended Floors

Ed Davies — Fri, 17 Jul 2015 20:49:57 +0100

Posted By: SaintThe reason they've been removed surely, albeit from a smaller space, is because they didn't dry out.

But surely that's a matter of the space: either it allows insulation to dry (on balance) or it doesn't? If it does then putting them in wet shouldn't do any harm in the long run. I'd be surprised if it did in the short run, either, unless they were really soaking.

Polystyrene Beads - Timber Suspended Floors

tony — Fri, 17 Jul 2015 20:53:53 +0100

Eps beads can't absorb water into the beads, only wet the surface or spaces between them.

Polystyrene Beads - Timber Suspended Floors

Viking House — Fri, 17 Jul 2015 21:59:19 +0100

Posted By: EasyBuilderDon't think I could do this to my house as polystyrene is supposed to rot electricity cable sheathing.

I removed beads from beneath a timber floor that were installed 4 years earlier, there was no sign of brittleness in the cables beneath the floor. I viewed them up close and bent them about 20 times. There was a rising damp issue before we pumped the floor but it was bone dry when we removed the beads.

Polystyrene Beads - Timber Suspended Floors

Viking House — Fri, 17 Jul 2015 22:06:24 +0100

Posted By: VictorianecoI think I'll do this, so a few questions...

1. What do I cover the cable in?
2. If I block up the floor vents, do I just use a similar brick and cement it in?
3. As I intend to use UFH, shall I just make a 1&quot; biscuit mix straight on to an Osb board between joists to be on the safe side? Or not bother and just run the ufh pipe clipped to sides and one in between joists?
4. No need for a vapour barrier? If the vents are sealed up?
Thanks

1. My own house is pumped and there's nothing covering the cables.
2. Yes.
3. You could use those metal trays that UF heating pipe clips into.
4. No need for a vapour barrier.

Polystyrene Beads - Timber Suspended Floors

Viking House — Fri, 17 Jul 2015 22:11:30 +0100

Posted By: Mike GeorgeBut not where the timber joists are embedded in an external wall with a steep temperature gradient to the outside..............Also where wooden wall plates are sat on colder masonry stub walls (though I agree this is less likely)

When you pump the floor with beads the joist ends buried in the wall are 5 degrees warmer than in an uninsulated ventilated floor. The joist ends are colder in a floor when the insulation is put between the joists and they don't rot.

Polystyrene Beads - Timber Suspended Floors

Viking House — Fri, 17 Jul 2015 22:15:05 +0100

Posted By: willie.macleodWould expect these beads to be bonded together? Are they really loose fill?

Spray some watery PVA glue on the loose beads as you install them.

Polystyrene Beads - Timber Suspended Floors

Saint — Fri, 17 Jul 2015 23:47:29 +0100

Posted By: fostertom
Posted By: SaintWhat mechanism will assist them to dry out?
Diffusion in warmer, drier conditions, no more rain wetting. How do we know that?
Posted By: SaintThe reason they've been removed surely, albeit from a smaller space, is because they didn't dry out
when continually re-wetted by rain penetrating the cavity. Wetting of CWI is not only due to rain penetration
Posted By: SaintWet insulation doesn't insulate
does, quite well. Really?
Posted By: SaintWet insulation ... will certainly stop water vapour passing through it
Why should it? (not saturated with standing water). The water vapour will just add to the wetness in the beads

Posted By: willie.macleodWould expect these beads to be bonded together? Are they really loose fill?
Even if a bit clumpy, still good almost-free insulation.

Polystyrene Beads - Timber Suspended Floors

Saint — Fri, 17 Jul 2015 23:48:31 +0100

OK I give up. Can't quote on multiple items.......

Polystyrene Beads - Timber Suspended Floors

fostertom — Sat, 18 Jul 2015 08:22:38 +0100

Posted By: Viking HouseWhen you pump the floor with beads the joist ends buried in the wall are 5 degrees warmer than in an uninsulated ventilated floor

Only true in case 3) below. Compare:

1) joist ends built into a solid or cavity wall, ventilated u/floor void -
joist ends are as cold as outside air temp.

2) joist ends built into a solid non-EWI'd wall or a cavity non-EWI'd non-CWI'd wall, u/floor void filled with beads -
at least the outermost bit of joist ends are still as cold as outside air temp (I'd agree with Mike here - asking for trouble).

3) joist ends built into a solid EWI'd wall or a cavity EWI'd or CWI'd wall, u/floor void filled with beads -
joist ends are much warmer (agree with VH here).

Polystyrene Beads - Timber Suspended Floors

fostertom — Sat, 18 Jul 2015 08:38:16 +0100

Posted By: SaintOK I give up. Can't quote on multiple items.......

Yeah, tricky.

Posted By: SaintHow do we know that?

Assuming the u/floor's subj to no more rain wetting, and assuming case 3) above, that's how it is.

Posted By: SaintWetting of CWI is not only due to rain penetration

Maybe, in the beads' previous life - but now in their new life, what source of wetting? Should be none.

Posted By: SaintReally?

Yes, with beads

Posted By: tonyEps beads can't absorb water into the beads, only wet the surface or spaces between them.

Posted By: SaintThe water vapour will just add to the wetness in the beads

Too simplistic to say that - if the following mechanism holds good, then both existing and any new moisture/vapour will disperse, at least from the region of the timbers:

Posted By: fostertomonce the beads are packed in, the timber floor/joists will be the very last things within the void to get to dewpont temp. They'll always be warmer than whatever is the coldest surface within the void, where any condensation will happen. Condensing-out on that 'condensing plate' will surely put a limit on how much water vapour there is within the void.

Polystyrene Beads - Timber Suspended Floors

Mike George — Sat, 18 Jul 2015 16:56:23 +0100

Posted By: Viking House
Posted By: Mike GeorgeBut not where the timber joists are embedded in an external wall with a steep temperature gradient to the outside..............Also where wooden wall plates are sat on colder masonry stub walls (though I agree this is less likely)
When you pump the floor with beads the joist ends buried in the wall are 5 degrees warmer than in an uninsulated ventilated floor. The joist ends are colder in a floor when the insulation is put between the joists and they don't rot.

Sorry but it is completely ridiculous to put any figures on a scenario you have no data for - The 5 degree figure you've invented is complete garbage - you clearly have no understanding of how a temperature gradient reduces between (and is dependent upon) inside and outside temperature .

It's just the usual Viking baiting I suspect..... to which I a have responded comprehensively to on many other threads. So unless you have something new?

Polystyrene Beads - Timber Suspended Floors

Victorianeco — Sun, 19 Jul 2015 12:26:16 +0100

Posted By: Viking House
Posted By: VictorianecoI think I'll do this, so a few questions...

1. What do I cover the cable in?
2. If I block up the floor vents, do I just use a similar brick and cement it in?
3. As I intend to use UFH, shall I just make a 1" biscuit mix straight on to an Osb board between joists to be on the safe side? Or not bother and just run the ufh pipe clipped to sides and one in between joists?
4. No need for a vapour barrier? If the vents are sealed up?
Thanks
1. My own house is pumped and there's nothing covering the cables.
2. Yes.
3. You could use those metal trays that UF heating pipe clips into.
4. No need for a vapour barrier.

3. Not sure I'd even need them? Wouldn't heat rise anyway from the pipes? Do they really need a screed or spreader plates for heat to emit?

Polystyrene Beads - Timber Suspended Floors

tony — Sun, 19 Jul 2015 16:24:28 +0100

1. Anything, polythene,mnylun, geotextile, slit oval conduit
2. Yes
3. No biscuit mix for me, clip pipes to top of insulation or battens over it, with air gap sealed to room and outside
4. I would use a vapour barrier as it can double as air tightness barrier, many don't.

Polystyrene Beads - Timber Suspended Floors

Viking House — Tue, 21 Jul 2015 00:53:37 +0100

Posted By: Mike GeorgeThe 5 degree figure you've invented is complete garbage - you clearly have no understanding of how a temperature gradient reduces between (and is dependent upon) inside and outside temperature .

Actually I have a very good understanding of temperature gradients, I had an Engineering student on work experience in the office in 2007 who spent 5 months drawing up details and putting them through Therm. At the end of his term I could accurately guess the U-value of a wall build-up and the psi leakage of a particular junction detail.
In a house where the void under the floor was pumped I drilled holes at a 45 degree angle into the middle of the joists where they sat in the wall and placed thermocouples into the holes and checked the temperature a few times.
I also discussed this process many times with Andy Lundberg from http://www.passivate.ie/ who lectures on 3D Thermal Bridge Analysis and PHPP in the Dublin Institute of Technology.
By insulating a wall and floor the heat-loss from an uninsulated junction increases making the joist ends warmer than previously. If you cut a section through the joist in the wall, the temperature gradients bellies around the joist end because its the least conductive element in the wall.
Anyway if the joist ends ever did reach dew-point there's no water vapour present circulating around the joist ends in the wall to condense because the sub floor vents are blocked up.
But most importantly I have something that you don't have and that's experience of over 50 projects where we pumped the floor void. Nobody came back to me with rotten floor joists and the oldest project is now 8 years old.

Polystyrene Beads - Timber Suspended Floors

Viking House — Tue, 21 Jul 2015 01:08:16 +0100

Posted By: Victorianeco3. Not sure I'd even need them? Wouldn't heat rise anyway from the pipes? Do they really need a screed or spreader plates for heat to emit?

I tried it without spreader plates or screed in my front room and left an air gap between the pipes and the timber floor. Its not half as effective as the UF heating in a screed in the middle room.

Polystyrene Beads - Timber Suspended Floors

Mike George — Tue, 21 Jul 2015 11:48:56 +0100

Posted By: Viking House
Posted By: Mike GeorgeThe 5 degree figure you've invented is complete garbage - you clearly have no understanding of how a temperature gradient reduces between (and is dependent upon) inside and outside temperature .
Actually I have a very good understanding of temperature gradients, I had an Engineering student on work experience in the office in 2007 who spent 5 months drawing up details and putting them through Therm. At the end of his term I could accurately guess the U-value of a wall build-up and the psi leakage of a particular junction detail.
In a house where the void under the floor was pumped I drilled holes at a 45 degree angle into the middle of the joists where they sat in the wall and placed thermocouples into the holes and checked the temperature a few times.
I also discussed this process many times with Andy Lundberg from http://www.passivate.ie/ who lectures on 3D Thermal Bridge Analysis and PHPP in the Dublin Institute of Technology.
By insulating a wall and floor the heat-loss from an uninsulated junction increases making the joist ends warmer than previously. If you cut a section through the joist in the wall, the temperature gradients bellies around the joist end because its the least conductive element in the wall.
Anyway if the joist ends ever did reach dew-point there's no water vapour present circulating around the joist ends in the wall to condense because the sub floor vents are blocked up.
But most importantly I have something that you don't have and that's experience of over 50 projects where we pumped the floor void. Nobody came back to me with rotten floor joists and the oldest project is now 8 years old.

So you got he 5 deg figure in THIS case how? Presumably by calculation.... Can you share your calculations please so we can all understand the justification for your claims. While you are at it can you also provide authoritative justification for your calculation method please? How about ONE single reference to an authoritative study of beads in a floor void ANYWHERE in the world?

My experience doesn't matter here -anyone who has done a simple temperature gradient calculation can see a hole the size of a bus in your argument. . I'm not the one making wild claims and giving advice contrary to Building regulations and Best Practice - presumably the writers of such documents have sufficient experience to know what they are talking about....

With regards to THERM it cannot predict the unique and multi directional heat and vapour movement through a joist end any more than WUFI or TAS can.....You need real life observation and study for that(and I don't mean 'I've done 70 houses so it must be okay for everyone to do the same') - even then the limited conclusions you would get from a PROPER SCIENTIFIC study would only apply to a single scenario.

Polystyrene Beads - Timber Suspended Floors

fostertom — Tue, 21 Jul 2015 15:06:54 +0100

WUFI 2D can - but takes overnight to run the calcs!

Polystyrene Beads - Timber Suspended Floors

Mike George — Tue, 21 Jul 2015 18:42:34 +0100

Don't think so Tom, not multi-directional (360 degrees) through multiple different materials at the same time - which is what happens in reality.

You have to choose a single direction through homogeneous *layers* of materials don't you? This was one of the problem I ultimately came across when looking at heat loss through solid floors with TAS - and a valid criticism of my results (though to a limited extent I believe) It simply cannot model such dynamic situations - and probably never will be able to