EWI and suspended floor?

andy125

I have a semi d 3 bed house cavity block walls that I have been thinking of getting EWI installed, the house has has new triple glazed windows and A rated doors fitted.

The house was gutted when we moved in and all floorboards were replaced, while the the floorboards were up new wiring and piping was layed and the suspended floor was insulated with netting and Rockwool and then covered with dpm and taped at joints.

What I should have done is covered the wiring in conduit and filled the suspended floor with beads but that is not an option now.

So my question is what effect would installing EWI have on the suspended floor if I didn't go to the foundation and left it ventilated ?

Would I get mould and damp where the wall passes the sub floor and enters the house, so say around the skirting board area due to the 2 different temperatures?

BryanF

When I did my suspended floor, I foam fixed PIR boards around the perimeter of the inside walls to reduce this risk. Haven’t got to the ewi yet. To answer your questions:

Take the ewi to foundation. But you need to vent sub-floor.
It’s not really damp.. you may have a cold bridge that may cause surface condensation leading to mould.

andy125

BryanF wrote: »

When I did my suspended floor, I foam fixed PIR boards around the perimeter of the inside walls to reduce this risk. Haven’t got to the ewi yet. To answer your questions:

Take the ewi to foundation. But you need to vent sub-floor.
It’s not really damp.. you may have a cold bridge that may cause surface condensation leading to mould.

Would it make much differnce going to the foundation if the subfloor is cold vented, it would in your situation as you have that added protection in insulation of the inner wall where I would have bare block

BryanF

In my experience, Do what you can, when you can. And Don’t revisit. If your willing to do a bit of the paths (I got a jackhammer for ~150 from aldi, have used to loads and it’s still going) when I can afford to do the front of house, I’ll be doing the concrete/digging. Extra insulation boards/fixings will be V little.

andy125

BryanF wrote: »

In my experience, Do what you can, when you can. And Don’t revisit. If your willing to do a bit of the paths (I got a jackhammer for ~150 from aldi, have used to loads and it’s still going) when I can afford to do the front of house, I’ll be doing the concrete/digging. Extra insulation boards/fixings will be V little.

Yea i have the same jackhammer, they are a beast. I suppose it wouldn't do any harm to go deep to the foundation just annoyed that i didn't research properly while i had the floor up, cheers for the advice.

rob w

Hi lads,

Just some questions on the above, I am a newbie to this stuff so might be silly questions. Planning on doing similar work myself soon!

BryanF - when you say you 'foam fixed PIR boards around the perimeter of the inside walls' do you mean along the inside of the external walls below the suspended floor? Do you have any pics or sketch of this or similar?

Also, how would there be a temp difference on wall as it passes through subfloor if you didn't insulate to the ground?

I hope that question is clear!?


Thanks

listermint

Dig up the foundation. There's no point defeating your good ewi by having its trousers pulled down around it's ankles.

Rent a consaw cut the path and use breaker. That's what I did. Had over 100 meters to do on my boundary though.... Not alot of crack that.

BryanF

rob w wrote: »

Hi lads,

Just some questions on the above, I am a newbie to this stuff so might be silly questions. Planning on doing similar work myself soon!

BryanF - when you say you 'foam fixed PIR boards around the perimeter of the inside walls' do you mean along the inside of the external walls below the suspended floor? Do you have any pics or sketch of this or similar?

Also, how would there be a temp difference on wall as it passes through subfloor if you didn't insulate to the ground?

I hope that question is clear!?


Thanks

Yes
No
Question is not really clear. Perhaps Research thermal bridging/ cold bridging

andy125

listermint wrote: »

Dig up the foundation. There's no point defeating your good ewi by having its trousers pulled down around it's ankles.

Rent a consaw cut the path and use breaker. That's what I did. Had over 100 meters to do on my boundary though.... Not alot of crack that.

How did you get around water mains, ESB cables etc without doing any damage?

listermint

andy125 wrote: »

How did you get around water mains, ESB cables etc without doing any damage?

I'm not sure about your water or ESB but they are legally supposed to be 750mm minimum below the ground.
Easily avoided but unsure about such things as that then Id advise getting professionals in

StephenS147

It's not required per se but perfectly safe to take it to the found but a lot of extra work. There would need to be a DPC installed at the same level as the existing in the EWI install to prevent moisture travelling up it along with the standard drip detail and the existing vents extended out.

See attached similar detail from kore website for retrofit. Link here, just click the retrofit pdf link towards the bottom. https://www.kore-system.com/koreproduct/kore-external-wall-insulation/

Architectural technician by trade speaking.

Edit. If this was new build you would install it to the found along with a row of thermal blocks where the level of floor insulation is. Zero cold bridging that way.

IMO this is the best way to build a house. EWI all the way.

Lumen

StephenS147 wrote: »

It's not required per se but perfectly safe to take it to the found but a lot of extra work. There would need to be a DPC installed at the same level as the existing in the EWI install to prevent moisture travelling up it along with the standard drip detail and the existing vents extended out.

See attached similar detail from kore website for retrofit. Link here, just click the retrofit pdf link towards the bottom. https://www.kore-system.com/koreproduct/kore-external-wall-insulation/

Architectural technician by trade speaking.

Edit. If this was new build you would install it to the found along with a row of thermal blocks where the level of floor insulation is. Zero cold bridging that way.

IMO this is the best way to build a house. EWI all the way.

That's interesting. I would have thought you'd need to go lower than that on the outside, but I guess not.

StephenS147

Lumen wrote: »

That's interesting. I would have thought you'd need to go lower than that on the outside, but I guess not.

Not necessary for retrofit. The biggest cold bridge will be up the 2 block leafs. This is where a row of thermal blocks would work wonders.

You could go one course below GL but any deeper and it would be a pain in the backside for minimal returns.

Give the guys at Kore a bell and ask then if they have a detail for your specific scenario. But the only difference would be to maintain the ventilation on your suspended floor.

In an ideal world of course. (pun indended) with blocks laid on their flat making a 215mm solid leaf. No cavity with 200mm EWI. Simple construction that can lead to an A rated dwelling.

listermint

This sounds very salespersony. Typical of the stuff that comes out of irish fitters.


1. the EWI you use on the bottom of an installation should be denser type which prevents wicking of water upwards. The KORE system even recommends this.

2. the EWI for the rest of the wall sits atop aluminium or stainless steel trays where the existing DPC sits. So you dont need to install additional DPC at all, it comes part of the install.

If you have a poured concrete floor it would be advisable to go below ground as it will conduct external cold from paths / driveways outside underneath your expensive EWI installation

My mother used to work in the industry and she would often come out with system specific sales speak.

A joy to watch.

BoardsMember

If the situation was suspended floor with no insulation and no airtightness, doing a big refurb with new flooring, and considering EWI....would it be worth cutting out the joists and backfilling the void, rather than doing the work to insulate and draught proofing? Half of existing suspended floor would be half of new extension.