cavity wall insulation

[billybuntus]

Does anyone have any experience with injecting insulation into a cavity wall?

I have a downstairs bathroom which suffers terribly with condensation on the external facing walls (2 walls).

No matter how much I leave the windows open (also have a large air vent fitted) we cannot shift the condensation and painting the room is a constant battle to keep it looking clean and tidy.

The external facing walls are the problematic walls the internal partition wall does not suffer condensation.

The room is a very cold room (probably due to the air vent and a concrete slab floor which is tiled).

My theory being that the room is a relativley modern edition (added in the 70's ish) to our old house and as such would have little cavity insulation fitted. If these injection people could increase the internal temp of the wall through extra insulation then I may well be on my way to a damp free bathroom! The room is also a flat roof and I may well remove the ceiling to insulate that also.

The next step after this (if its not very effective) would be to look at internal insulation which I am loathed to do just yet.

An idea of cost would also be good, the room is approx 9 square metres and the external walls are easily accessible.

any ideas?

thanks,

 

[MikeG.]

Damp walls and condensation issues are generally best assessed by a site visit, and quite difficult to be specific about from a distance. In general terms, your first moves should be to check that there is nothing causing any problems on the outside of the wall (.......overflowing gutters, burst drains, raised soil levels etc.) and then to check on the construction of the wall. Is there a cavity? What are the skins on the wall made of? What is dimension of any cavity? Is there any insulation in there at the moment?

One of the best ways to access the wall to find out the answers to these questions is to remove a window board (you will know it as a window cill or window ledge). Otherwise, you will probably have to drill a couple of biggish holes....one for a torch, the other for your eye and/ or a tape measure.

Is your building a bungalow, or a two storey house?

Mike

 

[yetloh]

Rockwool injection (it is blown in) is widely available, relatively inexpensive and highly effective as a means of improving thermal performance. If your problem is purely condensation due to cold walls, it should certainly help.

Jim

 

[eoinsgaff]

This may be a bit premature but if you do go with the injected insulation I'd strongly recommend getting a copy of the relevant BS (British Standards, not... you know what I mean). There's a clear drawing in it of the recommended drilling pattern.

Its very important around windows and doors as cavities in the insulation are easily left if not done right. You'll be paying the same anyhow.

I'll try to locate a copy of the drawing if you wish...

 

[wobblycogs]

We got cavity wall insulation (blown rock wool) put into our last house. The difference was amazing, all the cold spots in the house vanished almost immediately. The only downside I have heard people mention is that it can cause damp because it bridges the gap between the two walls. It wasn't a problem for us but it's worth finding out about.

 

[billybuntus]

Damp walls and condensation issues are generally best assessed by a site visit, and quite difficult to be specific about from a distance. In general terms, your first moves should be to check that there is nothing causing any problems on the outside of the wall (.......overflowing gutters, burst drains, raised soil levels etc.) and then to check on the construction of the wall. Is there a cavity? What are the skins on the wall made of? What is dimension of any cavity? Is there any insulation in there at the moment?

One of the best ways to access the wall to find out the answers to these questions is to remove a window board (you will know it as a window cill or window ledge). Otherwise, you will probably have to drill a couple of biggish holes....one for a torch, the other for your eye and/ or a tape measure.

Is your building a bungalow, or a two storey house?

Mike

Hi Mike,

The guttering a facia's are in good nick and I regularly maintain them (if anything there looking a big scruffy and I will be replacing them in the summer).

The wall has no soil surrounding it, (concrete yard with excellent drainage channels).

The hole that has been made through the wall to fit the air vent makes me believe theres a cavity, I'll take the facia off to check how deep the cavity is.

The cill is tiled so I'll use the air vent to check.

The main house is a two storey, the extension is single with a flat roof. Before you mention it theres no leaks on the roof as its been covered in a plastic sheet which has done an excellent job for the past 15 years...

thanks

 

[billybuntus]

We got cavity wall insulation (blown rock wool) put into our last house. The difference was amazing, all the cold spots in the house vanished almost immediately. The only downside I have heard people mention is that it can cause damp because it bridges the gap between the two walls. It wasn't a problem for us but it's worth finding out about.

Roger that, thanks for the info

 

[billybuntus]

This may be a bit premature but if you do go with the injected insulation I'd strongly recommend getting a copy of the relevant BS (British Standards, not... you know what I mean). There's a clear drawing in it of the recommended drilling pattern.

Its very important around windows and doors as cavities in the insulation are easily left if not done right. You'll be paying the same anyhow.

I'll try to locate a copy of the drawing if you wish...

Yes please

 

[MikeG.]

OK, that clears up the obvious......so just find out if you have any insulation in the cavity, and if not, get some blown in. You might do well to check around the rest of your house at the same time. I don't believe it is an expensive process, although I have no experience.

If that doesn't cure it, then you might consider a humistat to control an independant (ie not on a timer switch) extractor.

If in doubt, the answer is almost always insulation and ventilation!!!

Mike

 

[billybuntus]

OK, that clears up the obvious......so just find out if you have any insulation in the cavity, and if not, get some blown in. You might do well to check around the rest of your house at the same time. I don't believe it is an expensive process, although I have no experience.

If that doesn't cure it, then you might consider a humistat to control an independant (ie not on a timer switch) extractor.

If in doubt, the answer is almost always insulation and ventilation!!!

Mike

Thanks mike.

Thats part of my wider plans, first up insulate to see if I can go some way to curing the problem.

The air vent serves its purpose at the moment but as you say an extractor would be the idle solution teamed with a humidistat I think.

And the major work will come from insulating the floor slab, I'm planning to rip up the tiles and put the insulating mat down then electric underfloor heating and tile on top, the floor level isn't a major issue as the 'lobby' outside of the bathroom is tiled then the house steps down so that level could also be changed without any major dramas.

thanks

 

[cambournepete]

OK, that clears up the obvious......so just find out if you have any insulation in the cavity, and if not, get some blown in. You might do well to check around the rest of your house at the same time. I don't believe it is an expensive process, although I have no experience.

Got my 4 bed detached done last october (?) for the pricely sum of £99
There are often offers around - I didn't even have to apply for a grant, the company doing the work did all that behind the scenes.

 

[billybuntus]

OK, that clears up the obvious......so just find out if you have any insulation in the cavity, and if not, get some blown in. You might do well to check around the rest of your house at the same time. I don't believe it is an expensive process, although I have no experience.

Got my 4 bed detached done last october (?) for the pricely sum of £99
There are often offers around - I didn't even have to apply for a grant, the company doing the work did all that behind the scenes.

Was that through a national company? talk about a bargain.

 

[Tierney]

I'm looking into the same thing for my house. I've been scratching my head as to how to find out if my walls have cavities; but, after reading this have realised that I can remove a vent in the bathroom and check.

My local free newspaper had an article saying you could get it done for £149 after a grant and gave the following link (I haven't looked at it yet)

www.easterncri.org

Does anyone know when they started putting cavities in walls; my house is 1940s/50s?

DT

 

[Digit]

They became common in the building boom before WW2. The time taken to build was significantly less as there was much less brick cutting involved.
Strange, at the time it was considered as 'Jerry Building'. The two types of construction ran side by side for years. Later you weren't permitted to put anything into cavities! Cavities became mandatory in 1940s ish!
You can usually tell the difference DT by looking at the brick bond.

Roy.

 

[would not]

6" humidistat extractor fan. They basically run all the time -very slow when not damp and fast when damp, fitted one to a customers house that had very damp walls in a kitchen that had been built on to house. They had water running down the walls and mould everywhere, fitted the fan and the water vanished within a few hours and when the black mould had been treated and painted over it never came back.
They are about £100 for a decent one but will work. They have back draft flaps built in so it won't make the room cold or drafty unlike air vents etc.

 

[yetloh]

It can be surprising how old a house can be and still have cavity wall construction - my daughter had a 1910 house which was built in this way and it even has galvanised wall ties.

Just to expand on the brick bond point, if the bricks on the outer face alternate between long face and end face, then it is a solid 9 inch wall.

Jim

 

[Digit]

then it is a solid 9 inch wall.

Yep! Till you have a house like my last one Jim. It was built as a coaching inn for stop overs and for people of lower status visiting the local industrial complex.
It was built in 1792, the front elevation was Flemish Bond, the bricks had been carefully selected to use the burnt ends to emphasize the pattern. The rest of the place was English Bond, till you got to a later extension that had been built on at the rear. That was solid 9 inch English Bond with a 2 inch cavity and a Stretcher built single leaf inner wall!

Roy.

 

[MikeG.]

Just to expand on the brick bond point, if the bricks on the outer face alternate between long face and end face, then it is a solid 9 inch wall. Jim

Generally true, Jim, but not foolproof. I often replicate old walls by specifying a cavity wall with outer leaf of Flemish bond, say, made with snapped headers.

Mike

 

[Digit]

Gawd that must be expensive Mike?

Roy.

 

[MikeG.]

No idea Roy!