Cavity Wall Insulation in Internal walls !!!

[mpooley]

Hi all
I have been furtling round in my loft today making sure insulation was all in place etc as my wife constantly complains of a cold Kitchen.

Our house is L shaped with the kitchen and utility room being single story and connecting to the garage. The rest of the house is two story and the whole house has Pitched roofs.

so While I was up there i noticed a huge draft (it is very windy) coming from the join with the two roofs and !!! the cavity wall in between the main part of the house and the kitchen!!
The house is a barn conversion and was all built in one go so I cant understand why there is a cavity wall there.

anyway the cavity is empty and on further examination I found that the wall between kitchen and the utility room is also a cavity wall and the wall between the utility and the garage too!  all empty and all draughty!

Is this unusual? I certainly cant see the point except the one to the garage of course.

Although I can get to the tops of the cavities i cant get to much of their length.
So this begs the question of what I should do about it as these walls are acting as single block exterior walls really! the heat is being lost into these cold cavities.

I could possibly poke enough glass fibre or rockwool into the tops of them to block them off and to my mind that would be enough as the heat would no longer escape upwards?

the other solution would be an injected fill?

or I could try and pour perlite down them which, where i can access them, would be easy but I'm not sure if it would flow enough sideways to fill them completely.
Oh they are not very clean cavities BTY lots of snots and rubbish!

If anyone has any suggestions I would appreciate them.

thanks

Mike

[Baz]

Sounds a bit odd but it might have been due to single storey extensions having to be built with the assumption they will be extended to 2 eventually, or some kind of fire barrier.
Have you determined where the wind is getting in and is it required as the only ventillation for the loft?
What are the floors? Suspended or solid. Reason being if you pour in loose fill it might find a hole into space under the floor and you'd be filling forever. Where one wall is utility or garage I should drill holes to allow filling all along as redecoration is less of an issue, and in the kitchen you might be able to take down a cabinet to drill or just cover the hole with a kiddies painting as per normal kitchen wall clutter.

[biff]

whoa mike,
          this furtling will have to stop,now if you were just futtering ,that would be ok but furtling is a fugitive type of futtering and can lead to all kinds of diversions.
     meanwhile you want to get rid of the draught,so i would recommend you use sausages, fiberglass lengths wrapped in plastic or foil1200mm long and 150sq. just stuff the lengths along the top of the cavity making sure the draughts are blocked.
  might not be a good idea to fill the cavity, but sealing the top will make a massive improvment.
                                                      cheers,,,,biff

[wookey]

This called thermal bypass and has been found to be a huge heat-problem in modern semis (they put an uninsulated cavity wall between them for noise reasons), and houses that have had extensions added beyond cavity walls.

Putting fluff in the top will be a dramatic improvement, but if the bricks rise up into the loft space then you still have a big thermal bridge, and the air will circulate freely inside the cavity, efficiently moving heat up to the cold brick at the top.

Pouring insulation in would fix that, but may well not be the best solution. That would isolate (thermally) the utility from kitchen and both from rest of house. You probably want those to remain within the thermal boundary of the building.

A better thing to do would be to fill the cavity with something that has thermal mass - e.g gravel, weak concrete. This will add thermal mass to the house, which is generally a good thing, especially if the building is used during the day. If you later improve the external wall insulation (which you almost certainly should be) this mass will help the building keep a stable temperature.

See many posting by Foster Tom on GBF about this subject.

[KLD]

Is the cavity in the dividing walls connected to the one in the outside walls? If so, then blocking off the top might not help that much as you'd be left with the wind going through horizontally.

Klaus

[mpooley]

Is the cavity in the dividing walls connected to the one in the outside walls? If so, then blocking off the top might not help that much as you'd be left with the wind going through horizontally.

Klaus

at the moment I don't know the answer to that.

the external cavity is insulated I know (with bats)

The idea of poring gravel down them seems all wrong lol but I do see your point.
On the other hand as the tops of the wall will still not be insulated won't that soak up the heat and transmit it up the wall?

I dont see much of a problem with isolating the kitchen thermally to be honest.

Why is nothing simple lol


Mike

[mpooley]

Is there any product I could just pour into the cavity from the top?

thanks

[JohnS]

Yes,  Silvpor by William Sinclair.  The basic product is vermiculite and the silvapor version is treated with a hydroscopic coating making it the most suitable for cavity walls and filling old chimneys.

William Sinclair delivered 14 bags, 100 litres each, to me £10.25+VAT inc delivery from near Doncaster to London.  £7.26 ex delivery + VAT.

John

[Iain]

Hi

Is there any product I could just pour into the cavity from the top?

Yes,  Silvpor by William Sinclair.  The basic product is vermiculite and the silvapor version is treated with a hydroscopic coating making it the most suitable for cavity walls and filling old chimneys.

William Sinclair delivered 14 bags, 100 litres each, to me £10.25+VAT inc delivery from near Doncaster to London.  £7.26 ex delivery + VAT.

The only problem I can see with this is that you will have to block up all the holes/air ingress points lower down the walls otherwise all the silvpor will just find all the holes and find a way out.
Iain

[mpooley]

I worked out the cost of silvapor to be over £200 smackers 
I  had a guy quote me £285 to fill the cavities 

so I went back up the loft and had a good hard look at just filling the top foot or so of the cavity with insulation.
and I dont think I can do it!
I would need at least an 8 foot pole with a rectangle on the end to be able to push it right up into the eaves and there are so many wall ties in the way i dont have any confidence it can be done. also I have a restricted opening and the longest stick i could get into the cavity was 3ft !

I can't see that the silvapor is worth the cost as I would have to do all the work myself so it looks like I will get the cavity filled at £285.00 .

don't know if i'll get financial payback just hope that we feel the difference . or at least the wife does 

Mike