Cavity Wall Insulation - not all walls?

[Rosie]

Hello,

I've got a conservatory on one side of my house (1960's council-build semi-detached).

A company has looked at the house and said that it isn't possible to do the cavity wall insulation without scaffolding. Furthermore, it isn't possible to insulate only two walls of the house because condensation will develop in the third, uninsulated wall. We aren't prepared to pay for scaffolding.

This is the back of my house:

/ roof | /__________________________| | | | | | | | | | | | | ----- ---- ---- | |-----------------------------------| NEXT DOOR _____| | flat | | roof | conservatory | utility | | room | |

------------------------------------------

1) Why isn't it possible to insulate 2 walls? How can condensation be a problem with insulating two walls, and yet it is possible to insulate half of a semi-detached house?

2) Why can't the installers just drill through the interior wall of the back bedrooms to install the cavity wall insulation? We've not got wallpaper or anything difficult to re-decorate.

I've got another surveyor coming round next week to talk about it, but I wanted some info before I hassled him.

Thanks in advance for help! ROSIE

[Andy Hall]

If you insulate two exterior walls, have a party wall and an uninsulated exterior wall, the last of these is likely to be the coolest assuming your neighbour heats their property.

So, if there is moisture in the air, it is going to tend to condense on the windows and on the uninsulated wall.

Whether it does, will partly depend on insulation.

It would be better to insulate all the walls, but is not the end of the world if you can't.

I see no reason why not, but can understand that they wouldn't want to climb on the conservatory without scaffolding.

.andy

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[Christian McArdle]

When doing half a semi, the missing wall is a warm interior one. If you miss off a cold exterior wall, you'll get mould and condensation on it.

They can, but probably didn't think of it because most people would be terrified at the prospect of their horrible floral wallpaper being damaged.

Christian.

[Set Square]

I suppose that if *all* the walls are cold, any moisture in the room condenses all round in a very thin layer and isn't too much of a problem. But if you just have *one* cold wall, it *all* condenses on that wall.

I've never heard of it being done from the *inside* - but can see no compelling reason why it shouldn't be. I suppose that the contractor may be a bit wary about drilling through buried cables etc. - which wouldn't be a problem when done from the outside. Most likely they drill from the outside "because it is the way we always do it"!

[Peter Crosland]

If scaffolding is required to do the job safely then you have little choice under the current Health and Safety rules. Certainly it would be required above the conservatory. Doing the work from within avoids any potential problems with hidden pipes or wiring within the inner wall or plaster.

gee six jay en [e-mail]

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[Set Square]

Are you sure that's what you *meant* to say?

[Ian Middleton]

A friend of mine, when he had cavity wall insulation installed, removed the relevant panes of glass from his conservatory roof first, to save on the cost of scaffolding (£500 I think). Meant the installers just used ladders. Put glass units back afterward, job done.

[Peter Crosland]

Mea culpa! Of course I meant the opposite. Thank you for correcting me.

[Peter Crosland]

However, it may well be that the rest of the job is too high to do without scaffolding these days. But of course the OP knows better than the people who quoted.

[N. Thornton]

whys that? The interior temp and RH will be the same as before, and the temps on the uninsulated wall will be the same as before.

Regards, NT

[Set Square]

My guess is (see my earlier post) that with just one cold wall, all the moisture in the room will condense on the same wall - rather than being evenly distributed - making it much wetter than it would otherwise be.

[Rosie]

Was that meant to sound bitchy? I don't know anything about it, I just don't have the money to pay for scaffolding.

ROSIE

[N. Thornton]

I've not lived in a house yet where condensation happens on the walls, so I still dont see it making a difference. If one had running walls already I guess it would make things worse.

[Peter Crosland]

Not really, but your original post sounded as though you felt scaffolding was unnecessary even though the company quoting did. It is not unusual to find people have a quite unrealistic view of what may be required. If the company is professional then they presumably feel the job requires scaffolding to do the job safely. By all means get other quotes but don't be too surprised if they say the same.

[Set Square]

I've not witnessed excessive condensation myself - but I assume that it *is* a problem in some cases - otherwise the current building regs about ventilation are a waste of time!

[Peter Scott]

I had a house foamed from the inside once. It was a new house and I was planning to redecorate. The reason? The outside was smooth stucco. When I asked the contractor whether I would be able to see the holes on the outside he said not. I was suspicious. Then I saw another house he had done. Yes- lots of obvious filling.

Rule one? Never believe what you are told by someone after your money. (that applies to poiticians as well!)

Peter Scott

[N. Thornton]

Ah yes. Why would one spend time effort and money draughtproofing AND spend time effort and money installing little fixed vents AS WELL.

NT

[The Natural Philosopher]

Try a single brick bathroom extension with almost no heating in winter.

Water cascades off the walls over the bath :D

[Christian McArdle]

The RH is higher, as before, there were an additional 2 walls permeable to water. The insulation saw to those.

Christian.