Floor insulation

Dtp1979

I’ll soon be pulling out suspended floors in a 1970’s bungalow. I have 400mm to fill up. I have the option of using 100mm or 150mm insulation. Is there really much difference or advantage in using 150mm over 100mm? I’ll be getting the walls pumped and attic well insulated too, but floors first

Gumbo

Dtp1979 wrote: »

I’ll soon be pulling out suspended floors in a 1970’s bungalow. I have 400mm to fill up. I have the option of using 100mm or 150mm insulation. Is there really much difference or advantage in using 150mm over 100mm? I’ll be getting the walls pumped and attic well insulated too, but floors first

Yes. Go big or go home in this instance.

Calahonda52

Are you replacing it with concrete?
if so cad é an scéal le radón?

Dtp1979

Calahonda52 wrote: »

Are you replacing it with concrete?
if so cad é an scéal le radón?

When I pull out the suspended floors I have 400mm to fill from old concrete subfloor to finished floor level. I was curious if the extra 50mm really made that much difference. I’m installing underfloor heating. Is it possible to install radon barrier in an old house? How would I vent it to outside and how would I seal it inside to the wall??

Also, I was going to use that liquid fast floor screed stuff. I haven’t priced against concrete or sand/cement mix yet though. Any idea on pricing on that?

Bullocks

Dtp1979 wrote: »

When I pull out the suspended floors I have 400mm to fill from old concrete subfloor to finished floor level. I was curious if the extra 50mm really made that much difference. I’m installing underfloor heating. Is it possible to install radon barrier in an old house? How would I vent it to outside and how would I seal it inside to the wall??

Also, I was going to use that liquid fast floor screed stuff. I haven’t priced against concrete or sand/cement mix yet though. Any idea on pricing on that?

We did up a house 2 years ago. We had to bring it up 350mm. The engineer called for a radon sump in almost every room piped out to the footpaths. He let us join a few of the pipes so we ended up with 5 radon caps outside.
Then it was 125mm of 804,
50mm sand with radon barrier taped onto the walls with barrier tape. 100mm kingspan, 1000gauge polythene, underfloor heating pipes and 75mm screed (dry we used).

Might have been a better job to use 125mm of concrete instead of 804 because the floor was a touch hollow but that was what we had priced for and they didn't want to pay the difference in price for the concrete

BryanF

Dtp1979 wrote: »

When I pull out the suspended floors I have 400mm to fill from old concrete subfloor to finished floor level. I was curious if the extra 50mm really made that much difference. I’m installing underfloor heating. Is it possible to install radon barrier in an old house? How would I vent it to outside and how would I seal it inside to the wall??

Also, I was going to use that liquid fast floor screed stuff. I haven’t priced against concrete or sand/cement mix yet though. Any idea on pricing on that?

I have 300mm of polystyrene in mine. No ufh, but every time I walk on it without shoes I’m glad of every bit of the insulation. 150mm PIR insulation would be minimum for new build with ufh

Dtp1979

Is Radon barrier an absolute essential? Is it expensive? Would it be worth getting the area tested to see if radon gas is present?

BryanF

Radon barrier is relatively cheap a roll will set you back maybe 100€. You’ll need tape also. It’s the same thing as ‘DPM’ (damp proof membrane) it normally goes above the sand layer, below the insulation layer.

Dtp1979

BryanF wrote: »

Radon barrier is relatively cheap a roll will set you back maybe 100€. You’ll need tape also. It’s the same thing as ‘DPM’ (damp proof membrane) it normally goes above the sand layer, below the insulation layer.

How large an area does a roll cover? And is the tape expensive?

Dudda

Dtp1979 wrote: »

How large an area does a roll cover? And is the tape expensive?

Think they are 4m wide and 20 or 25 meters long. A roll of tape maybe €10 each or something like that but you'll need a few rolls. A radon test will probably work out more expensive and remember these radon barriers also stop moisture and rising damp. You'll need some type of plastic barrier to stop the moisture and could spend €35 on a roll of that and another €40 on tapes. Almost half way to the cost of the radon barrier.

Whatever the total cost of the radon barrier it's tiny in the grand scheme and you'd be an massive idiot (harsh but true) to omit it.

Dtp1979

Dudda wrote: »

Think they are 4m wide and 20 or 25 meters long. A roll of tape maybe €10 each or something like that but you'll need a few rolls. A radon test will probably work out more expensive and remember these radon barriers also stop moisture and rising damp. You'll need some type of plastic barrier to stop the moisture and could spend €35 on a roll of that and another €40 on tapes. Almost half way to the cost of the radon barrier.

Whatever the total cost of the radon barrier it's tiny in the grand scheme and you'd be an massive idiot (harsh but true) to omit it.

Does the 1000 gauge polyethylene not act as damp course?
I’d rather have the peace of mind having the radon installed

Dudda

Dtp1979 wrote: »

Does the 1000 gauge polyethylene not act as damp course?
I’d rather have the peace of mind having the radon installed

Ya the 1000 gauge polyethylene is the plastic barrier I was referring to. It's about €35 a roll although that could be the heavier 1200 guage which is harder for the builders to rip. Either way it's not a big jump to the €100 for the roll of radon.

Calahonda52

Will be tough shot to get it installed at all, not to mind correctly as a retro, with existing internal and external walls in place

Dtp1979

Calahonda52 wrote: »

Will be tough shot to get it installed at all, not to mind correctly as a retro, with existing internal and external walls in place

All you can do is seal to the existing block I’d imagine?

Calahonda52

Dtp1979 wrote: »

All you can do is seal to the existing block I’d imagine?

Sump? ducting?

Dtp1979

Calahonda52 wrote: »

Sump? ducting?

Ah yes of course

Metric Tensor

You've 400mm to fill up?

If you give us the build up starting at the sub floor and ending at the finished floor level it would allow us to comment on each level ...

Is it something like:

Existing concrete
175mm gas permeable aggregate (T2 Perm)
Radon Barrier
150mm PIR insulation
Polythene
75mm screed
Floor finish

Dtp1979

Why do you need both radon barrier and polyethylene?

Looking at radon testing, it doesn’t look that expensive. Would it not be worth checking if radon is present?
I imagine covering 230sqm of an old house, using several sumps and piping to outside it’d add up to a costly figure? Radon testing doesn’t look that expensive.

Metric Tensor

Radon testing takes 6 months and you have to be living in the house. Also there's no point testing it with a ventilated sub floor now because that will have no bearing on the radon that will be in the house when you remove that ventilated sub floor.

The reason they put radon barriers in new houses is that it can't be sorted afterwards without spending tens of thousands. It will be the same cost for you to retrofit.

You don't necessarily need a sump in each room if there is a path for gas to move through the rising walls.

P.S. Regardless of what you do you should test for radon after you move in. Everyone should do that. Costs less than 200 quid and if your levels are high you just whack a fan on the extract pipe (that you've already installed) and away you go.

Metric Tensor

The polythene is to stop your liquid screed from pissing all over the place when you pour it out like water. - Not essential but I think pretty messy without.

The radon barrier is a combined barrier to radon gas and barrier to any rising moisture.

Bullocks

Dtp1979 wrote: »

Why do you need both radon barrier and polyethylene?

Looking at radon testing, it doesn’t look that expensive. Would it not be worth checking if radon is present?
I imagine covering 230sqm of an old house, using several sumps and piping to outside it’d add up to a costly figure? Radon testing doesn’t look that expensive.

I'm no expert but I think radon levels can change over time .You would probably get away with just the radon barrier instead of two layers . I think our plumber that wanted the polythene between the insulation and underfloor heating pipes .

Dtp1979

Metric Tensor wrote: »

Radon testing takes 6 months and you have to be living in the house. Also there's no point testing it with a ventilated sub floor now because that will have no bearing on the radon that will be in the house when you remove that ventilated sub floor.

The reason they put radon barriers in new houses is that it can't be sorted afterwards without spending tens of thousands. It will be the same cost for you to retrofit.

You don't necessarily need a sump in each room if there is a path for gas to move through the rising walls.

P.S. Regardless of what you do you should test for radon after you move in. Everyone should do that. Costs less than 200 quid and if your levels are high you just whack a fan on the extract pipe (that you've already installed) and away you go.

As far as I know, it only takes 3 months. The house is vacant and i have the keys but no work will commence for at least 3/4 months. There’s 2 rooms, opposite ends of the house that are sand/cement where I was going to place the radon sensors.
Regarding sumps, the layout of the house would make it hard for radon gas to move freely through rising walls as all internal walls are concrete.

Calahonda52

Dtp1979 wrote: »

As far as I know, it only takes 3 months. The house is vacant and i have the keys but no work will commence for at least 3/4 months. There’s 2 rooms, opposite ends of the house that are sand/cement where I was going to place the radon sensors.
Regarding sumps, the layout of the house would make it hard for radon gas to move freely through rising walls as all internal walls are concrete.

Look like 3 from epa
https://www.epa.ie/radiation/meas/radon/services/

Metric Tensor

Apologies. 3 months it is. Was going from memory with the six. Still pretty pointless testing a house with a mainly ventilated sub floor and then blocking all that ventilation even if bits of it have some of the ventilation blocked already.

It seems like you are looking for someone to tell you that it's ok to avoid doing things the right way so as to save a few quid.

Radon causes cancer. It's good practice to do everything you can to avoid having it in the house your family is going to live in. There's not many here who are going to tell you that's it's a good idea to just take the risk.

Dtp1979

Metric Tensor wrote: »

Apologies. 3 months it is. Was going from memory with the six. Still pretty pointless testing a house with a mainly ventilated sub floor and then blocking all that ventilation even if bits of it have some of the ventilation blocked already.

It seems like you are looking for someone to tell you that it's ok to avoid doing things the right way so as to save a few quid.

Radon causes cancer. It's good practice to do everything you can to avoid having it in the house your family is going to live in. There's not many here who are going to tell you that's it's a good idea to just take the risk.

I’m not trying to cut corners at all but I’m also not trying to throw money away. I don’t see why I should put in radon barrier if I have no radon gas! Radon isn’t in every house in Ireland!

sydthebeat

Dtp1979 wrote: »

I’m not trying to cut corners at all but I’m also not trying to throw money away. I don’t see why I should put in radon barrier if I have no radon gas! Radon isn’t in every house in Ireland!

in the grand scheme of things the cost difference between installing a radon membrane compared to a 1200 gauge DPM is negligible.

1200 gauge DPM costs about €50 per roll for 55 sq m

visqueen radon membrane costs €50 for 80 sq m

the work involved in retrofitting both is practically the same.

personally its a no brainer to me in a retrofit, considering the extra protection. who knows what kinds of land the house was originally built on.

Dtp1979

Ok ok I’ll fit the radon barrier.

The Mighty Quinn

Dtp1979 wrote: »

I’m not trying to cut corners at all but I’m also not trying to throw money away. I don’t see why I should put in radon barrier if I have no radon gas! Radon isn’t in every house in Ireland!

I'd argue it probably is in every home in Ireland.... just not at a level that is considered harmful.

But either way, you won't know what your radon concentration levels are until you've a test done on your house, which you won't be able to do until you've the works completed with the solid floor instead of suspended, at which point it'll be too late to do anything about it.

TheChizler

sydthebeat wrote: »

in the grand scheme of things the cost difference between installing a radon membrane compared to a 1200 gauge DPM is negligible.

1200 gauge DPM costs about €50 per roll for 55 sq m

visqueen radon membrane costs €50 for 80 sq m

the work involved in retrofitting both is practically the same.

personally its a no brainer to me in a retrofit, considering the extra protection. who knows what kinds of land the house was originally built on.

I thought you had to have a specialist install it and sign of and that was where the big cost came in? A colleague was caught for €1k recently to put it down in a new sunroom, engineer wouldn't sign off unless it was done professionally. Couldn't see the point as the rest of the house had none and was draughty.

sydthebeat

TheChizler wrote: »

I thought you had to have a specialist install it and sign of and that was where the big cost came in? A colleague was caught for €1k recently to put it down in a new sunroom, engineer wouldn't sign off unless it was done professionally. Couldn't see the point as the rest of the house had none and was draughty.

ive never heard before that you need to be trained specialist to install a radon membrane.

the NSAI certification for these types of product does not refer to any certified installer, and the certs themselves are basically a "how to install" guide

Metric Tensor

There's no rule that says it has to be done by a "certified" installer.

However, I have seen on a couple of big jobs recently where certain manufacturers will only offer certain types of guarantee if you use one of their suggested installers. A bit like you sometimes see with flat roof membranes and such like.

In a case like the OPs - if I was signing off on the work I'd probably be ok with him doing it himself provided he followed the manufacturer's guidelines and didn't rush off to cover it up before I inspected it!

Dtp1979

I’ll be doing 100% of the work myself so I won’t need it signed off. I will follow the manufacturers instructions to a Tee

Calahonda52

so now that we have got to agreeing the membrane goes in, whats the ducting plan?

Dtp1979

Calahonda52 wrote: »

so now that we have got to agreeing the membrane goes in, whats the ducting plan?

This is wrecking my ducting head .
All advice welcome. Ideally maybe the 4 corners and one from the centre of the house?

chooseusername

Calahonda52 wrote: »

so now that we have got to agreeing the membrane goes in, whats the ducting plan?

And the ventilation, and airtightness and.....and.......

Calahonda52

Dtp1979 wrote: »

This is wrecking my ducting head .
All advice welcome. Ideally maybe the 4 corners and one from the centre of the house?

Did you read and understand post 17 above?

Dtp1979

Calahonda52 wrote: »

Did you read and understand post 17 above?

I did yea. I was thinking of 50/60 mm of that fast floor screed, or 70/100mm concrete or sand/cement mix, below that will be 150mm insulation and whatever remains will be 804 and sand with radon barrier. Is that what you mean?

Metric Tensor

Order a material called T2 not 804.

You're not allowed put 804 under floors anymore because it hasn't enough testing done on it for pyrite. (And other deleterious materials!)

T1 is the equivalent of 804 for under floors but you want T2 because it allows the radon gas to move to your sump. No point putting in the radon stuff and then not put a gas permeable fill around it.

The sand you need is T3 - it's just blinding sand but has been tested for pyrite.

Dtp1979

Metric Tensor wrote: »

Order a material called T2 not 804.

You're not allowed put 804 under floors anymore because it hasn't enough testing done on it for pyrite. (And other deleterious materials!)

T1 is the equivalent of 804 for under floors but you want T2 because it allows the radon gas to move to your sump. No point putting in the radon stuff and then not put a gas permeable fill around it.

The sand you need is T3 - it's just blinding sand but has been tested for pyrite.

Great info. Thank you. You can come give me a day with the wheelbarrow too if you free

Metric Tensor

Dtp1979 wrote: »

Great info. Thank you. You can come give me a day with the wheelbarrow too if you free

Haha. I worked very hard to become the soft handed pencil pusher I am today! ;-) I'll hold the clipboard for you!

Calahonda52

Dtp1979 wrote: »

I did yea. I was thinking of 50/60 mm of that fast floor screed, or 70/100mm concrete or sand/cement mix, below that will be 150mm insulation and whatever remains will be 804 and sand with radon barrier. Is that what you mean?

Not 804

Dtp1979

Electrican has suggested that underfloor wiring would be the best option too.
If anyone else has any other ideas/suggestions feel free to throw them out there

Dtp1979

Thinking about it, if I tape the radon onto all internal blocks, what’s to stop the radon gas rising up and out through the block into the room?

Bullocks

Dtp1979 wrote: »

Thinking about it, if I tape the radon onto all internal blocks, what’s to stop the radon gas rising up and out through the block into the room?

There isn't much more you can do retrospectively but as someone mentioned by using the right fill let the radon travel through it into the sumps it might travel easier through that rather than travelling through the concrete blocks.
You will sure be reducing the area it can travel through with the barrier if it's just down to the area of the blocks anyhow
Will you have to alter any door heights or windows when you bring up the floor? Could be something to think of aswell and a plumber to rise the rads

chooseusername

Dtp1979 wrote: »

Thinking about it, if I tape the radon onto all internal blocks, what’s to stop the radon gas rising up and out through the block into the room?

Good, positive ventilation ,won't stop the radon but will dilute it to harmless levels and disperse it
Important if you go for airtightness.

Dtp1979

Bullocks wrote: »

There isn't much more you can do retrospectively but as someone mentioned by using the right fill let the radon travel through it into the sumps it might travel easier through that rather than travelling through the concrete blocks.
You will sure be reducing the area it can travel through with the barrier if it's just down to the area of the blocks anyhow
Will you have to alter any door heights or windows when you bring up the floor? Could be something to think of aswell and a plumber to rise the rads

I’m a plumber myself so I’ll be installing underfloor heating. No door heights to be altered or windows.

Dtp1979

chooseusername wrote: »

Good, positive ventilation ,won't stop the radon but will dilute it to harmless levels and disperse it
Important if you go for airtightness.

Is that your opinion or is it fact do you know?

chooseusername

Dtp1979 wrote: »

Is that your opinion or is it fact do you know?

An opinion based on engineers advice during a renovation, but others on here may be more qualified to advise.
This is Public Health UK. website,
but radon is radon.

https://www.ukradon.org/cms/assets/gfx/content/resource_3574cs1b9f38268c.pdf

Metric Tensor

Dtp1979 wrote: »

Is that your opinion or is it fact do you know?

Radon is dangerous when its concentration in the air you breathe is too high. Unless your house is built inside a uranium mine there's almost no possibility the outside air will have a higher concentration of radon than what's inside your house. Hence every radon mitigation measure involves ventilation of some type.

I don't know enough about reci rules to know about sub floor electrics but if you have the opportunity to build in a couple of conduits and pull chords now I would personally do it for future proofing. Almost no-one ever does though!

Dtp1979

Metric Tensor wrote: »

I don't know enough about reci rules to know about sub floor electrics but if you have the opportunity to build in a couple of conduits and pull chords now I would personally do it for future proofing. Almost no-one ever does though!

I will. I’ll have ducting to nearly every room and probably a spare 6” duct to the shed, all ran back to the hotpress.