Cavity wall insulation

[FlouncingBabooshka]

Does anyone know how to establish if a house has cavity wall insulation?

We have a detached bungalow built in 1931. The current EPC rates it as an F, though the surveyor expressed an off the record opinion that this had been incorrectly assessed. We have triple glazing at the back of the house and he thought this had been counted as double and that the secondary glazing at the front hadn’t been accounted for at all. I’m not sure how much of a difference this would make.

The EPC assumed no cavity wall insulation. However, I’ve recently discovered some paperwork, commissioned by a previous owner in 2008, which relates to recommended energy saving measures. This lists measures already undertaken and these include cavity wall insulation. There’s no proof of this - it appears to have been based purely on information given by the owner and no actual inspection has taken place. The house is fully rendered so there are no obvious holes where insulation would have been put in.

I’ve aways felt the house doesn’t perform as badly as would be expected with such a poor rating (thankfully!). It warms up well and the temperature doesn’t plummet as soon as the heating is off. We also have an unusual layout here which means most of the rooms have three external walls so I’ve been pleasantly surprised both by how warm it is and by the cost. Whilst our bills are quite high I don’t think they are outrageous compared to our last home, which was semi-detached and C rated.

All of this is making me think perhaps we do have cavity insulation after all. This would make quite a difference to the EPC which would be very helpful if and when we come to sell.

Any idea what we need to do to find out?

Did you give the paperwork to the EPC assessor? They assume it isn’t there unless it can be shown otherwise.

To add, it’s unlikely that you have a cavity wall if your house was built in 1930, it’s more likely solid. If it is an early cavity wall it would be inadvisable to add cavity wall insulation. Cavity wall insulation in old properties is asking for damp issues.

first, measure the thickness of your walls, at a window or door opening.

If it is aboy nine inches, plus plaster and render, it is solid. If about 13 inches, pretty sure to be cavity.

Then, go up into the loft with a good torch. At the eaves, the tops of the walls will most likely be exposed and you can peer into them. Do you see anyhthing?

IME, when you look at gappy brickwork, for example under the sink where drilled for pipes, or in the loft or some cupboards that are unplastered, or under the floor when running pipes, or making holes for an extractor fan or cooker hood, you will find CWI that has come through the gaps, if the walls have been filled after build.

That’s not true about cavity walls from 1930s - we have a house built in 1937, big standard and thousands of them round here. All have cavities

bog standard

You can also look for signs of filling on the outside - small filled holes about 1 or 1.5m apart in the mortar. That’s where they blow it in.

Btw houses from 1920s onwards tend to have cavities

Thanks for the replies.

@elbea I’m afraid I don’t know what the assessor was given as I didn’t commission the EPC, it was done by the previous owners. The paperwork found just confirms a previous owner indicated there was cavity insulation but there’s no paperwork to prove that. Both EPC assessor and surveyor have said it is cavity wall.

@Leftbutcameback - thank you but unfortunately we can’t see any mortar as it’s completely rendered. May I ask, are your cavity walls filled? I hear a lot of contradictory advice re 30s houses and insulation so I’m interested in the experiences of others.

@PigletJohn thank you. Walls are just over 13 inches. No unplastered areas anywhere to check. I’ll have to try to get into the loft. Are there any other ways to check? We’re having some windows replaced next spring - I assume it will be obvious once the old ones are taken out? Or would a cavity wall insulation company be able to check if they do an inspection to ascertain suitability for insulation?

Thanks again everyone.

when you take the windows out of an old house, the CWI, if present, can be seen. Sometimes it falls out.

If you have window boards, you will probably see into the cavity if you take one out.

Modern houses will have cavity closers of some kind built into the wall.

A CWI surveyor will often drill into a wall and look into the cavity. I don't know if they always do that.

@flouncingbabooshka ours aren't filled as far as I know. Certainly the house doesn't feel well insulated at all. I was seriously considering it last winter but worried about the stories of damp you hear. I had found a good contractor who I would have been happy to use but they said they weren't doing any cavity wall insulation at the moment.

The biggest issue we have is a thin wall at the front which doesn't have a cavity - often known as tile hung although ours is rendered instead.

Thanks @PigletJohn and @Leftbutcameback. How strange about the contractor you found. I wonder why they aren’t doing cavity wall insulation now?

I guessed maybe it was because of the government scheme (they weren't part of it so maybe the business was going elsewhere) and also a fair few claims re:damp