Insulation

Dtp1979

In my house I have the old suspended floors. I’m looking to insulate. Apart from the sheer awkwardness of doing such a job, is it allowed to be insulated underneath? What’s the best way of doing it?

Outkast_IRE

Dtp1979 wrote: »

In my house I have the old suspended floors. I’m looking to insulate. Apart from the sheer awkwardness of doing such a job, is it allowed to be insulated underneath? What’s the best way of doing it?

I was watching the deep retrofit episode of ecoeye and didnt particularly fancy the way they were doing it with the kingspan insulation and expanding foam .

Of it was my own house I think I would prefer to put 2x1 lats on the underside and use rockwool flexislab as the insulation , I have worked with it before and find it a good product. Others may have advice on air tightness membranes but I think this goes in as the top layer just under the floor

Lumen

Skirting off, floors up, blowerproof paint or plaster on external walls below skirting level, properly line sub-floor ventilation holes through external walls, pipe insulation on hot water pipes, windproof membrane over joists, insulation over membrane between joists, optional vapour permeable airtight membrane over insulation, acoustic joists strips on joists, T&G OSB glued and screwed to joists, airtight tape membrane or OSB to walls, skirting back on before carpets or after wooden floor.

Dtp1979

Lumen wrote: »

Skirting off, floors up, blowerproof paint or plaster on external walls below skirting level, properly line sub-floor ventilation holes through external walls, pipe insulation on hot water pipes, windproof membrane over joists, insulation over membrane between joists, optional vapour permeable airtight membrane over insulation, acoustic joists strips on joists, T&G OSB glued and screwed to joists, airtight tape membrane or OSB to walls, skirting back on before carpets or after wooden floor.

Although that’s probably as good a job as can be done, I don’t want to go to such rounds. Something simple that will help. It won’t be a problem if I put Rockwool between the joists so? I was afraid it might affect air circulation or something

Lumen

Dtp1979 wrote: »

Although that’s probably as good a job as can be done, I don’t want to go to such rounds. Something simple that will help.

What do you have in mind?

Dtp1979 wrote: »

It won’t be a problem if I put Rockwool between the joists so? I was afraid it might affect air circulation or something

No, it's completely normal.

Dtp1979

Lumen wrote: »

What do you have in mind?


No, it's completely normal.

I don’t plann on taking up floors. Maybe an access hole or 2, get in and pack rockwool up between the joists. As long as it’s not going to cause moisture build up or similar. I’m a plumber by trade and have to rise a lot of floors, and I never see insulation under old suspended floors, so I always wondered why. Now that I have a house with them, I think it’s foolish not to insulate down there

Dakotabigone

Blow the boards and joices out of it, put down dpm, insulation, sort out your pipes and pour a screed.
What you are wanting to do is only Mickey Mouse.

Dtp1979

Dakotabigone wrote: »

Blow the boards and joices out of it, put down dpm, insulation, sort out your pipes and pour a screed.
What you are wanting to do is only Mickey Mouse.

Mickey Mouse will have to do for now seeing as I’ve just bought a house and only looking to do small changes for now

Kevin Finnerty

Dakotabigone wrote: »

Blow the boards and joices out of it, put down dpm, insulation, sort out your pipes and pour a screed.
What you are wanting to do is only Mickey Mouse.

Finances might play a role.

No expert here but at least line the external walls otherwise damp might play it's part..

Dakotabigone

He wants to insulate it, if he can’t afford it he should go to Dunnes and buy some more clothes.

Lumen

Dtp1979 wrote: »

I don’t plann on taking up floors. Maybe an access hole or 2, get in and pack rockwool up between the joists. As long as it’s not going to cause moisture build up or similar. I’m a plumber by trade and have to rise a lot of floors, and I never see insulation under old suspended floors, so I always wondered why. Now that I have a house with them, I think it’s foolish not to insulate down there

If you have room to crawl around underneath you can do that, but in my case I only had less than a foot under the joists and there were several sleeper walls (is that the right term?) going across which would have blocked access. Also, unless you're using the most expensive high density rockwool (metac?) or crampable semi-rigid wood fibre you'll need to hold the insulation up with something, and without the air tightness you can get cold air pulled through and around the insulation like it's not there.

Sleeper12

Dtp1979 wrote:

Although that’s probably as good a job as can be done, I don’t want to go to such rounds. Something simple that will help. It won’t be a problem if I put Rockwool between the joists so? I was afraid it might affect air circulation or something

I had an extention built 10 years ago. Builder placed plastic over the joists with a dip in the middle & placed rock wool in the dip. Sheets of ply went on top of this. I don't know if this is standard but it sounds like what you have in mind. My extention is comfortable & holds the heat well.

Rows Grower

Dakotabigone wrote: »

He wants to insulate it, if he can’t afford it he should go to Dunnes and buy some more clothes.

Are you a financial adviser yourself by any chance?

You come across as a very successful person.

Dakotabigone

Sleeper12 wrote: »

I had an extention built 10 years ago. Builder placed plastic over the joists with a dip in the middle & placed rock wool in the dip. Sheets of ply went on top of this. I don't know if this is standard but it sounds like what you have in mind. My extention is comfortable & holds the heat well.

Wow did he turn up riding a horse? What engineer passed that?

Sleeper12

Dakotabigone wrote:

Wow did he turn up riding a horse? What engineer passed that?

Jasus your on the high horse tonight. Careful it's a long way down

Dakotabigone

Sleeper12 wrote: »

Jasus your on the high horse tonight. Careful it's a long way down

What was done by your builder was cow boy stuff. Facts are facts. I’m sorry to inform you of that.

Sleeper12

An engineer on site for a small extension? You are stuck in the celtic tiger era.

Edit: it's the same job Lumin described in an earlier post

Lumen

This is all covered under section 9 of SR54.

http://www.ili.co.uk/en/S.R.54-2014.pdf

Lumen

Sleeper12 wrote: »

An engineer on site for a small extension? You are stuck in the celtic tiger era.

Edit: it's the same job Lumin described in an earlier post

True but I doubt any new construction is done this way, it's all insulation under screed now I think.

The engineer I consulted about my retrofit also recommended ripping and filling the suspended floor but my budget is needed elsewhere.

Dakotabigone

Lumen wrote: »

True but I doubt any new construction is done this way, it's all insulation under screed now I think.

The engineer I consulted about my retrofit also recommended ripping and filling the suspended floor but my budget is needed elsewhere.

You know your stuff.

Sleeper12

Lumen wrote:

The engineer I consulted about my retrofit also recommended ripping and filling the suspended floor but my budget is needed elsewhere.

From my point of view its pointless going to the expense of this for a small extension when the rest of the house has no floor insulation being built in 1964.

I have retro fitted 100mm foam insulation on all the walls throughout the house. My entire ground floor is tile and hardwood. I'll be long dead by the time all of that gets pulled up

alan1963

Hi
You can insulate under suspended floors if you have enough room to work by cutting kingspan strips with a saw to fit tight between joists, then stapling some netting underneath to stop it falling out (gardeners type netting).

A cheaper alternative to kingspan is rockwool type loft insulation but not as good u value.

dathi

https://www.q-bot.co/
a uk company that got EU funding to develop underfloor insulation

Dtp1979

alan1963 wrote: »

Hi
You can insulate under suspended floors if you have enough room to work by cutting kingspan strips with a saw to fit tight between joists, then stapling some netting underneath to stop it falling out (gardeners type netting).

A cheaper alternative to kingspan is rockwool type loft insulation but not as good u value.

Getting underneath to work would be a nightmare though.
I wonder would pumping in insulation be an option? Although filling up to 20” would be hugely expensive I’d say

Calibos

I thought you said you already had or would knock through access to the underfloor area?

Lumen

Dtp1979 wrote: »

I wonder would pumping in insulation be an option? Although filling up to 20” would be hugely expensive I’d say

It's worth considering why the suspended wooden floors are required to be ventilated to the outside.

This is because they contain wooden structural components that are outside (at best) or worse, part-inside-and-part-outside the heated envelope of the property and therefore susceptible to condensation and decay.

If you entirely fill the underfloor void with insulation, and prevent infiltration of air by blocking up the sub-floor vents, then in theory the joists will be kept warm and dry as they're inside the heated space, and are no more likely to rot than your kitchen table.

But AFAIK nobody actually does that, probably because if you used (relatively cheap) beads you'd still have convection losses coming up from the ground, and if you used foam it'd probably be cheaper to just rip the floors up and do a proper insulated concrete job.

Dtp1979

Calibos wrote: »

I thought you said you already had or would knock through access to the underfloor area?

I would knock a hole. It’s easy to create access down there. It’s a whole other ballgame trying to work down there though. I’d say taking up floors, insulating, sealing and re laying is my best bet

Call me Al

We have insulated most of our suspended floors. As we renovate each room we are lifting the floorboards completely though. We have replaced in some rooms.
And yes you need to maintain ventilation down there as otherwise your timber will rot.

Dtp1979

What has better u values, 4” kingspan rigid, or rockwool, between the joists?

GreeBo

Lumen wrote: »

Skirting off, floors up, blowerproof paint or plaster on external walls below skirting level, properly line sub-floor ventilation holes through external walls, pipe insulation on hot water pipes, windproof membrane over joists, insulation over membrane between joists, optional vapour permeable airtight membrane over insulation, acoustic joists strips on joists, T&G OSB glued and screwed to joists, airtight tape membrane or OSB to walls, skirting back on before carpets or after wooden floor.

Would the vapour permeable membrane not be underneath the insulation to allow any moisture within the wood to get out to the ventilated space?

This is the way I've seen it done (from a vertical POV)

Flooring
Airtight/windproof barrier
Insulation/joists
Vapour Permeable Barrier
Air gap/vents
Soil/debris(!)

Lumen

GreeBo wrote: »

Would the vapour permeable membrane not be underneath the insulation to allow any moisture within the wood to get out to the ventilated space?

This is the way I've seen it done (from a vertical POV)

Flooring
Airtight/windproof barrier
Insulation/joists
Vapour Permeable Barrier
Air gap/vents
Soil/debris(!)

I think you're mixing up air tightness and windproofing.

Airtightness is always on the warm side, windproofing on the cold side.

The purpose of air tightness is to prevent heat loss and moisture movement through leakage of air at high pressure and humidity differentials

The purpose of the windproofing is to prevent heat loss by bulk air movement at low pressure differentials through fibre insulation.

To use a human analogy, airtightness = skin, insulation = woolly jumper, windproofing = jacket.

Vegeta

Lumen is what you are calling wind proofing commonly referred to as a vapour barrier?

To allow moisture to leave the house the vapour barrier is usually on the cold side. So in your analogy it is a gore-tex type jacket, allowing moisture/sweat generated by the house/body to leave.

Lumen

Vegeta wrote: »

Lumen is what you are calling wind proofing commonly referred to as a vapour barrier?

No, because a vapour barrier is on the warm (in) side, and you don't get wind inside your house.

This explains it all from the perspective of one manufacturer:

https://proclima.com/building-physics

Vegeta wrote: »

To allow moisture to leave the house the vapour barrier is usually on the cold side. So in your analogy it is a gore-tex type jacket, allowing moisture/sweat generated by the house/body to leave.

If the vapour barrier is on the cold (out) side of the insulation, it will be cold, and warm moist air will move through the insulation and condense on it. That would be bad, right?

GreeBo

Lumen wrote: »

If the vapour barrier is on the cold (out) side of the insulation, it will be cold, and warm moist air will move through the insulation and condense on it. That would be bad, right?

Vapour barrier or Vapour Permeable Barrier ?

Using my example above, how is the warm moist air getting through the airtight barrier that is above the insulation?

Vegeta

Lumen from your link above when describing the windproof layer:

Roof and façade mem­branes must meet high tight­ness re­quire­ments for pro­tec­tion from driv­en rain and wa­ter. At the same time, they should also be highly per­meable to al­low mois­ture to dry and evap­or­ate quickly and re­li­ably from the struc­tur­al com­pon­ent to the out­side.

So yeah the windproof layer is what is commonly referred to as a vapour barrier (or vapour permeable barrier)

Lumen

GreeBo wrote: »

Vapour barrier or Vapour Permeable Barrier ?

Which do you mean? I haven't used either of those terms (except in reference to your post) as they're complicated by humidity-variable diffusion resistance where the product is designed to be vapour closed in the winter and vapour open in the summer.

Using the term "vapour barrier" for the outside windproofing (as I think you've done) seems weird to me, because the primary job of that barrier is not to be a barrier to water vapour, it's to stop wind blowing through the insulation.

GreeBo wrote: »

Using my example above, how is the warm moist air getting through the airtight barrier that is above the insulation?

It can't in theory but can in practice, due to penetrations, staples, nails, rips, whatever in either of the two layers, which is why the ability to dry to the outside is important. Which is also why I wouldn't use the term "vapour barrier" for the outside layer, since you don't want the outside layer to be a barrier to vapour, you want it to be a barrier to wind (and rain, if it is exposed).

Lumen

Vegeta wrote: »

So yeah the windproof layer is what is commonly referred to as a vapour barrier (or vapour permeable barrier)

I find the mixing of those two terms confusing for the reasons stated above.

GreeBo

Vegeta wrote: »

So yeah the windproof layer is what is commonly referred to as a vapour barrier (or vapour permeable barrier)

I would see "vapour barrier" and "vapour permeable barrier" as two totally different (and contrary) things, I dont think you can use them interchangeably?

A vapour permeable barrier, to me at least, is equivalent in most cases, to a windproof barrier. It stops the wind but allows moisture to escape, which is why it would be used on the cold side in my example above.

GreeBo

Lumen wrote: »

Using the term "vapour barrier" for the outside windproofing (as I think you've done) seems weird to me, because the primary job of that barrier is not to be a barrier to water vapour, it's to stop wind blowing through the insulation.

Im specifically using vapour *permeable" barrier for outside windproofing, stops unwanted airflow but allows unwanted moisture to escape to the ventilated underfloor space.

Lumen

GreeBo wrote: »

Im specifically using vapour *permeable" barrier for outside windproofing, stops unwanted airflow but allows unwanted moisture to escape to the ventilated underfloor space.

Ah right OK.

I think though in your description of layers it makes more sense to call the outer layer "windproofing" and the inner layer "air tightness" (as pro clima do), rather than focusing on vapour permeability, since both of them may be vapour permeable under certain conditions depending on product choice.

Vegeta

GreeBo wrote: »

Im specifically using vapour *permeable" barrier for outside windproofing, stops unwanted airflow but allows unwanted moisture to escape to the ventilated underfloor space.

Apologies you are correct, vapour permeable barrier is what I should have been saying.

Vegeta

Semantics out of the way we're all in agreement that insulation without these extra steps really is a very limited option for the op.

OP comparing u-values of rockwool versus kingspan thermafloor is great and all but cool air will just blow in and around gaps in the insulation if it isn't "sealed*" in some way.

So from this thread my takeaway would be:

Yes insulation can be put under floating floors

Insulation on it's own is a limited solution

Putting in a little more effort with specific barriers/membranes will increase the performance of your endeavour

*sealed is the wrong word because it implies nothing can get out, when you really do want moisture to travel outwards, but you know what I mean

tro90

https://www.superfoil.co.uk/vapour-control-multi-foil-insulation/


I used this recently on my suspended flooring and it seems to have done a good job.

GreeBo

Lumen wrote: »

Ah right OK.

I think though in your description of layers it makes more sense to call the outer layer "windproofing" and the inner layer "air tightness" (as pro clima do), rather than focusing on vapour permeability, since both of them may be vapour permeable under certain conditions depending on product choice.

True, but I think the layer closest to the coldzone/ground must be vapour permeable or you are goosed with rot. If its not windproof you risk draughts alright, but I'd rather let the other layers handle drafts (esp since there is a top layer of vapour barrier) than risk rot.

So its a vapour permeable windproof membrane!

We are "lucky" that we rarely have to worry about keeping it colder inside than out, (which flips the problems and is where your "certain conditions" comes in) unlike lots of other countries.

GreeBo

tro90 wrote: »

https://www.superfoil.co.uk/vapour-control-multi-foil-insulation/


I used this recently on my suspended flooring and it seems to have done a good job.

Adding this in Irish homes with suspended timber flooring typically makes a huge difference due to preventing drafts rather than any additional insulation. (As Vegeta says above)

GreeBo

Vegeta wrote: »

Semantics out of the way we're all in agreement that insulation without these extra steps really is a very limited option for the op.

OP comparing u-values of rockwool versus kingspan thermafloor is great and all but cool air will just blow in and around gaps in the insulation if it isn't "sealed*" in some way.

So from this thread my takeaway would be:

Yes insulation can be put under floating floors

Insulation on it's own is a limited solution

Putting in a little more effort with specific barriers/membranes will increase the performance of your endeavour

*sealed is the wrong word because it implies nothing can get out, when you really do want moisture to travel outwards, but you know what I mean

If you just lifted the carpet/flooring (leaving the original timbers) and wrapped the floor in a vapour permeable windproof membrane (wrapped meaning up under the skirting and sealed it to the walls) and then relaid the carpet or ideally a floating wooden floor then you would probably get the most bang for the least buck.

You will still be losing heat through the floor, but your house wont be drafty like it probably is today. Arguably the windproof part is the most important part of the retro fit in our old homes.

grounderfill

Suspended floors in my house.
Ten years ago I cut open the floor, small trap door size, and went down underneathe with chicken wire. Nailed on chicken wire to outer joist and insulated with fibreglass wool. Use a mask and eye protection. The difference is phenomenal.

Lumen

grounderfill wrote: »

Suspended floors in my house.
Ten years ago I cut open the floor, small trap door size, and went down underneathe with chicken wire. Nailed on chicken wire to outer joist and insulated with fibreglass wool. Use a mask and eye protection. The difference is phenomenal.

S'

Would spraying between the joists underneath with open cell spray foam be a solution?
I know of a lot of contractors doing this recently

I am considering my options at the moment.
I have a suspeneded ground floor 4.5ft high. Half concrete (ufh), half timber.

GreeBo

S' wrote: »

Would spraying between the joists underneath with open cell spray foam be a solution?
I know of a lot of contractors doing this recently

I am considering my options at the moment.
I have a suspeneded ground floor 4.5ft high. Half concrete (ufh), half timber.

You are already insulated?

S'

GreeBo wrote: »

You are already insulated?

Yes, insulated some what but to a now poor standard.
There is a big air gap between the insulation and the floor. There is no insulation between the timber joists.