Cavity wall insulation done .. wot a difference !

[mike]

We have just had our 1930's semi, cavity wall insulation done on the government scheme. It cost us £150 up here in chilly North Yorkshire.

The difference in house temperature is remarkable. Well ... not just the temperature. The house holds the heat for ages before the combi kicks in to keep the temp at 20deg. I was pretty sceptical about it all at first, but at £150 I thought it was worth it. It was :)

There have been a couple of threads on here re these schemes, where posters have asked if it was a good thing to do, so I thought I would just pass on my observations :)

[Rod]

Been meaning to ask - when "they" do an installation, do they fill the cavity between semis or terraced houses?

[Mary Fisher]

We're in Leeds, Yorkshire.

We had our cavities (walls, not teeth) filled donkeys' years ago and the difference was instant. I'm sure the financial savings have more than paid for it too.

Mary

[Phil L]

No...although some may go down there accidentally, it's not purposely filled, only exterior walls are filled and walls between properties are not exposed to the elements. There's another reason why it is bad practice and that is the potential for blocking flues which may be on this wall, and the added problem of neghbours who may be absent / unwilling and whose flues cannot be checked.

[BRG]

Rod,

When they cavity fill a single house in a semi or terrace, they fit a flexible 'brush' in the cavity between the properties to stop the overspill.

BRG

[Phil L]

He means in the party wall

[Rod]

Thanks. Behind our stack pipe in the downstairs toilet there had been a series of gaps at the ends of the lightweight blocks. Although boxed in, the wind that came in there was phenomenal. I have attacked that properly but it left me thinking that there would still be that gale between the leaves of the wall between the houses. Hence the question.

[Rod]

I did. I do. But thanks.

In our case the next door house is stepped from ours so the insulant would not fall along the way into the neighbour's cavity. However, that makes me realise that the stepped bit *is* external wall and would need insulation.

[BRG]

Phil L,

Many party walls are *not* cavities, especially in older properties. They are usually 9" or 13" solid brickwork - although there are the exceptions.

BRG

[Rod]

Because of the stagger between us and next door, the front and back of the house would have to have a stretch of full cavity wall along the party wall. To reduce that to 9" on the part that is common would cause there to be a step in the wall. There does not appear to be such a step but I shall re-check tomorrow in case it is not obvious. For now, I assume full cavity right the way through. Hence the original question.

That in turn raises the question of what happens if we get CWI done. Do we need permission from the neighbours? Should they contribute to any costs (on the basis of mutual advantage)?

Oh - no flues or anything else I can think of that would complicate this technically.

[BRG]

Rod,

If there is a cavity between in the party wall, then to fill this would require drilling holes in an internal wall with the correseponding costs of redecoration etc.

It is also possible that if this party wall is in fact a cavity, then the contractors would have fitted a cavity brush as close a possibe to the "stagger" between the buidings to prevent the cavity fill from 'slumping' into the void due to a lack of support.

In theory, to drill and fill a party wall, you would need to comply with the Party Wall Act in giving notice to the neighbours - with all the corresponding paperwork and possible appointment of Party Wall inspectors.

With regards to costs, you would not be able to 'force' the neighnours into paying a share - but you would be liable for any damage caused to their property by vibration etc.

BRG

[Rod]

Thank you. I have now checked - the interior party wall is precisely lined up with the "stagger" so the wall (and I am sure it is the same on the neighbour's side as well) must have a cavity.

How far can they "reach" from a hole along a cavity wall? Is it just the immediate vicinity of the hole or can they feed a pipe in and fill it some distance away? (I was more aware of the details back in the days of polyurethane foam!)

[Peter Scott]

When you look at the cost of installing cavity insulation, and increasing loft insulation, it's amazing that more people don't do them. Especially loft insulation which is dirt cheap. As you say the cost is repaid in a very short time, perhaps months at present in a larger house. I just spent 40 pounds increasing my loft from 10 to 20 cm and the difference was noticeable on oil consumption. Just in time too! And yet people are persuaded to spend many thousands on double glazing, when their window frames are fine, which takes decades to pay back unless the windows are huge.

If you are willing to spend a bit you can shake off the puritanical demands to put on outdoor clothes indoors and turn down the thermostats to red-nose levels. There's no need for that, nor for pensioners to be cold.

Peter Scott

[Mary Fisher]

Effective insulation is vital for comfort as well as for saving money and fuel.

We're anything but puritanical and we are pensioners.

There's no need to put on outdoor clothes indoors but an extra layer of indoor clothing (a jumper for instance) is personal insulation and makes a lot of sense. A 12 yo grand daughter has just been this weekend and was complaining about being cold. She was wearing a very thin floaty dress and wouldn't put on another layer because it wasn't 'cool'. So she stayed cold while everyone else (including her sister) was warm.

Our roomstat is set at 10c and we never have red noses. Nor do we have colds.

I agree that there's no need for anyone to be cold but wasting resources is stupid when donning a sweatshirt would keep one warm.

By the way, because of our insulation (including self installed double glazing which did NOT cost thousands) our winter heating grant pays for more than half of our annual gas consuption and that includes cooking.

Mary

[Keith2.0]

For 10c, yes a swearshirt, but also gloves a ski mask and seal skin parker. Arn't you worried that their memories of you will be "that lady with the freezing house"?

[Mary Fisher]

Not at all. You're displaying an ignorance of a thermostat. Remember that the roomstat doesn't determine the heat of the house - it means that the ch boiler doesn't fire unless the temperature gets down to 10C.

There are enough other sources of heat in the very well insulated house that the temperature very rarely gets down to 10C.

People usually take off their jumpers, jackets or sweatshirts when they come into our house. I have had complaints that the house is too warm.

Mary

[Doctor Drivel]

£150 is the cost of an overcoat you would wear in he house.