Energy Company Obligation survey

[Radian]

So it turns out SWMBO has organised a visit by a surveyor for the local Housing Authority after finding that our household is eligible for an ECO grant.😵

 

I guess it's some consolation for getting old but It seems odd for someone to show up at our sprawling 4-bed detached property and size us up for a hand-out.

I'm right in the middle of the process of adding  loft insulation, which does not meet standards as it happens. I'm just taking my time and some areas are just 100mm or less deep, but I think I'd rather finish the job so I'm wondering if to point towards our empty cavity walls instead...

 

The main house has a two lightweight block leafs with the outer one clad in sandstone. The cavity between the blockwork is only around 50mm wide and we're in zone 1 where penetrating rain is an issue. I know the stonework sometimes gets thoroughly saturated but have no idea what happens inside the cavity. All I know is that we've had no damp issues inside. I want to know what questions I should be asking about this as the nightmare scenario is becoming yet another victim of Inappropriately installed Cavity Wall Insulation 

 

The other concerns I've voiced before about CWI for our property are that the water table is very high such that there is sometimes water coming up to around one block below the DPC on two sides of the house. I remember peering down at it when the house was at beam and block stage. There's nothing to stop a cavity fill dipping down into this as far as I can see - so wicking would be a problem with some materials.

 

EPS beads are supposed to be a safer bet but then we also have a location where all the house electric cables cross through the cavity from one wing to another and there are well known issues about PVC and PS getting jiggy - so I'm not sure if that should rule it out or not. I'm starting to dread the visit now.

[Radian]

I've been reading again through the House of Commons debate on cavity wall insulation that took place in 2015. I'm starting to think there's another potential issue in addition to the obvious problems posed by rain penetration. Could the build-up of mould and damp on interior walls people are experiencing following installation of CWI be due to the loss of air circulation in the cavity? I'm always complaining about the draughty dry lining that issues cold air around light switches and sockets but this is also indicating an air exchange that will be transferring moisture from inside air, via the cavity and ventilated attic, to the outside.

 

If CWI effectively stops this then other measures will be required to control moisture levels such as MV or better still  MVHR. If it's just down to opening more windows does it not defeat the purpose of the insulation?

[ToughButterCup]

25 minutes ago, Radian said:

..

Could the build-up of mould and damp on interior walls people are experiencing following installation of CWI be due to the loss of air circulation in the cavity

...

 

I'm almost sure - without definitive evidence - that this is exactly what happened in our old cottage.

 

The guy fitting the CWI mentioned the need to keep the cavity wall 'breather' brick open, but then promptly blocked it up by putting CWI  inside  the cavity.

He tried to convince me how impossible it was (?) to ensure the airway was left open. I suggested that the sector must have a standard procedure for making sure that CWI didn't block the wall.

 

You can't make this next bit up......

 

I had to leave for work, so nobody other than him was on site. He put a cowl  on the outside of the  one wall which had CWI in it (the others were solid - a meter or so thick) : it masked the fact that there was no breather grill behind it.  And promptly left the site. I rang to complain.

 

Was dealt with politely. And nothing happened.  Except the growth of mould on the inside the wall treated with CWI.

So I put a small bookcase in front of it.

(If our car engine makes an unexpected noise I promise I don't turn the radio up louder to mask the noise.)

 

Job's a good'un

Edited May 31, 2022 by ToughButterCup

[Radian]

So it seems that retrofit CWI should also be done along with updgrades to ventilation otherwise the original ventilation may well be insufficient to prevent condensation. Seems counterintuitive because the CWI is done to reduce heat loss through walls (hence make them warmer) but they're still going to be one of the first interior surfaces to fall below the dew-point. It seems to make the whole thing a nonsense.

[Ferdinand]

Is this not more likely due to below standard install of CWI eg air bricks not being protected by tubes? Which allows the CWI to block up the ventilation system.

 

Just CWI in the cavity alone would not do that surely, since there are still all the other leak routes in a traditional leaky house.

 

IMO if CWI is done with a proper install it should be fine.

 

But of course ventilation must always be considered.

 

My council even had to revisit dozens of houses in an EWI project because no one had thought about ventilation properly.

[Radian]

1 hour ago, Ferdinand said:

Is this not more likely due to below standard install of CWI eg air bricks not being protected by tubes? Which allows the CWI to block up the ventilation system.

Yes, this seems to happen all too often. However, our house has no 'air bricks' so the only 'officially built-in ventilation' is the trickle vents in the windows. Like they're not firmly kept shut in the winter. 🙄

 

These CWI firms make me laugh. This is the second time I've had to explain to one of their reps that a DPC doesn't always close the cavity. On both occasions I had asked what was to stop the CWI wicking up water from below DPC and they said the DPC spans the cavity so the fill stops above DPC. I don't think I was being believed when I told them otherwise.

 

I don't know how often cavities are closed off at the bottom with angled tray (or stepped DPC) + weeps but I do know that our house has a separate run of plastic on both leafs. And there's no deliberate drainage off the top of our foundation strips either, so water can accumulate down there quite a bit.

[Radian]

So, we've been "measured up" for Evobead (AKA Climabead) EPS in the cavities. Given the build date of our house (1997) the surveyor wouldn't believe me that our cavities were empty until he got out his SDS drill and borescope. I've run the build-up through Ubakus and it seems filling the 55mm cavity would take us from 0.675 W/(m²K) down to 0.262 W/(m²K)

 

 

😱

 

 

Not brilliant but a whole lot better. 0.413 W/(m²K) saving over 160m² and 20C difference amounts to 1.3kW less heat input needed during the coldest sort of days we get here. Working out an annual saving is a bit more difficult.

 

I guess around half of this for 6 months might be a ballpark ~ 2800 kWh or £170 ish.

 

I bet the cost makes this more than a 10 year payback.

[SteamyTea]

3 minutes ago, Radian said:

Working out an annual saving is a bit more difficult.

Why, it is just a temperature distribution, which is close enough to a normal distribution to not have to worry.

[Radian]

I do have the monthly gas consumption for the last couple of years and if I take the months where heating was off as the baseline for DHW and subtract that from each month, then I suppose I could apply the U-Value ratio between insulated and uninsulated build-ups? All seems a bit too easy. E.g. Last year:

 

J 3060 + F 2191 + M 1672 + A 1311 + M 1041 + O 1049 + N 1559 + D 2326
= 14209 kWh * 0.262/0.675 = 5515 kWh

Which is a saving of 8684 kWh, or £695 at 8p/kWh

 

Oh, that can't be right can it?

[Radian]

Perhaps someone who's got bonded EPS can answer a question about how much air movement I can expect from bead filled cavities? As there's an open structure in the spaces between beads obviously it's not entirely draft proof but would it have any effect on the drafts we get behind the dot & dab plasterboard? I'm thinking the howling gale we get around switches and sockets is due to the empty cavities which reach up to the ventilated roof space and have poor airtightness (complete lack of) around first floor joists and ground floor block and beam.

[Radian]

Well, the beads are in and I have now had a graphic demonstration of the amount of air leakage from the cavity into the interior of the house. We had to evacuate during the filling process as the high pressure air forced an extremely fine 'mist' of choking dust into all the rooms. There were no particular areas, just a general haze throughout every room. No doubt, the combined effects of air leaks though minute cracks around window frames, electrical outlets, skirtings etc.

 

Of course this will be no surprise to anyone who's laboured over getting air-tightness into their new build but it's disappointing for me. I've spent most of this year draft proofing and going on search and destroy missions to fill gaps around pipework and junctions around the house. But the minute particle size as evidenced by the haze has taken me quite by surprise.

[ProDave]

43 minutes ago, Radian said:

We had to evacuate during the filling process as the high pressure air forced an extremely fine 'mist' of choking dust into all the rooms. There were no particular areas, just a general haze throughout every room.

Were you warned this might happen?  I guess you now have a fine layer of dust on every surface to clean up now?

[Radian]

13 minutes ago, ProDave said:

Were you warned this might happen?  I guess you now have a fine layer of dust on every surface to clean up now?

No warning, I had already been hectoring the installation team about small things (like don't try filling the cavities that are already insulated!) so I did the "it's me again" intro and casually mentioned that the family had just vacated the house and he said it was quite normal for clouds of dust to appear - and apologised for not giving prior warning. I actually think they did a very tidy job though, the outside was left in good order. Just a great deal of hoovering and dusting to do indoors and lots of bedsheets to put though the wash. 😝