# Cavity wall insulation



## Davos87 (25 Nov 2019)

Be interested to hear of anyone's experiences good or bad.
I live in a 4 bedroom 1930 property out in the sticks., quite exposed and and the house gets battered at times by strong winds coming off the Hambleton Hills that I live opposite. My hallway is particularly cold despite a radiator and friend saying getting it insulated really is a no brainer. The rooms coldest run adjacent to the large expanse of external wall at the side of my property alongside my drive and thats the prime candidate for the cavity insulation. The brickwork is in sound condition to my untrained eye. However, I'm naturally cautious and have read some troubling stories of damp, increased condensation problems and reluctance from some companies to rectify faults should they arise after installation etc?
Friend of mine had the blown bead insulation installed a few years a go and says its made a significant difference to the ' feel' of his property although his house is relatively modern compared to mine.
He got a free survey and subsequent free installation with a supposed 30 year guarantee but he has mislaid all the details of the company he used. How can I find out if I might qualify for this and source reputable installers? How is it done for free? Do the companies claim back costs from government green energy efficiency schemes for example? I have had a cursory look online and there seems to be companies falling over themselves to come out and give you a survey and advise whether its appropriate for your property but still have reservations. What have I got to lose unless the good folk on here know otherwise? 
Thanks in anticipation of any advice.


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## Beebo (25 Nov 2019)

Do you definitely have a cavity wall. My house is 1936 and has a solid wall. The external walls get very cold.


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## numbnuts (25 Nov 2019)

We had it when I was living with my parents in the winter the whole house was so warmer and in the summer a lot cooler, I'm living in a flat now which also has wall insulation and the heating is hardly on during the day even when it is bitterly cold outside and again a lot cooler in the summer months too.


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## Ajax Bay (25 Nov 2019)

My house was built in '36 (relatively exposed to southwesterlies). We had CWI done a few years ago. The installation was trouble free and I don't think I paid, but had to pay for scaffolding - about the same as the saving in the first year: it did reduce the heating bills. I think you need to employ your Yahoo-fu to find out more.


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## midlife (25 Nov 2019)

Just moved to a 1933 house, had to do a bit of work in the front room and the CWI was patchy at best so went for insulated plasterboard on the external walls,


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## Archie_tect (25 Nov 2019)

The Green Initiative ended in disgrace some years ago...

How wide is the cavity? Less than 75mm [3 inches min ideally, but probably 2" if 1930's cavity] won't provide significant benefits as the wall ties act as a cold bridge. There will be a saving which should save the cost of installation in 3-5 years depending on the cavity width.

The cavity needs to be inspected by CCTV to check the condition of the wall ties and the bottom of the cavity for mortar 'snots;' bridging the cavity which is allow water to cross if fully filled in such an exposed location. Have a look at Sheffield Insulation Group [used them for 25 years] https://www.sigretrofit.co.uk

Polystyrene beads stick together but can leave voids which again allow water to build up and cross the cavity leading to damp if the installation isn't thorough.

The better alternative is to insulate with min 3" of closed cell insulation board such as Xtratherm and render/ ship-lap board [horizontal rot-proof composite boards or larch/western red cedar if you prefer wood] the external walls which adds another weatherproof layer and increases the internal thermal mass of the house on the 'warm side'.

Insulating the inside is OK if the rooms are large and square.

Don't forget to insulate the floors if you have underfloor vented void under timber floors, and put 450mm 'Earthwool' [rockwool] quit;t in the ceiling voids [leaving a 50mm gap to the underside of the sarking felt below the rood battens for cross ventilation]- not forgetting to insulate and weatherstrip the roof hatch..


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## BoldonLad (25 Nov 2019)

Not directly comparable to your situation, but, for what it is worth:

- Detached House, built in 1985
- Urban Environment, so, not particularly "exposed"

We had cavity wall insulation installed, and, loft insulation increased to then current standard (in about 2003) when a grant was offered via Government or Local Authority, I forget which.

We have not had any adverse effects (ie no condensation, damp etc), but, neither have we had any noticeable positive effects. Heating bill not reduced by any noticeable degree, and, wife still permanently "cold".


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## Slick (25 Nov 2019)

The cavity is there for a reason, don't fill it.


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## screenman (25 Nov 2019)

Slick said:


> The cavity is there for a reason, don't fill it.



You try building a house without filling them now, building standards would have a field day.


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## Slick (25 Nov 2019)

screenman said:


> You try building a house without filling them now, building standards would have a field day.


Not up here, new build still have a cavity and the insulation is on both external and internal leafs. Mostly timber frame up here now though for house bashing.


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## screenman (25 Nov 2019)

Slick said:


> Not up here, new build still have a cavity and the insulation is on both external and internal leafs. Mostly timber frame up here now though for house bashing.




Times have changed then , I built this one 10 years ago and had to stuff them.


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## Globalti (25 Nov 2019)

Far far better to clad the house with Kingspan and a timber cladding so that the walls become a heat sink, or dry-line the entire house with Kingspan and foam-backed plaster board. 

Or demolish and rebuild.


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## Archie_tect (25 Nov 2019)

If I were to built my own house now I would definitely use a timber frame/ insulated SIP panel system using 144 reg x 38 timber studs faced with building breather membrane on 9mm OSB board with 120mm Kingspan/ Xtratherm insulation between the studs to provide a 25mm service zone faced with plasterboard. The service zone avoids having to upsize the electric cables which overheat when buried in insulation. A slightly better way is to use a insulated multiple foil blanket layer with 38x25 battens to create the service zone which provides the serviced zone inside the insulated vapour check layer to the stud wall - reducing the U-value to about 0.08 but with the additional cost of the extra layers.

On the outer face you can batten and clad with anything you like as a rainscreen or build a cavity brick/block outer leaf with a 100mm cavity partially filled with 50mm closed cell insulation [again Kingspan or Xtratherm backing onto the OSB board to eliminate the cold bridge of the timber studs. This would give a U-value of about 0.11 W/sqm.DegC which with 450 quilt insulation in the loft [0.1 U-value] and 150mm Xtratherm in the floor [0.12 U-value] means you get as close to thermal perfection as you can get without spending an unreasonably stupid amount of money!

One day... when our children reproduce and we move south to live near them so we can be involved grandparents!


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## Grant Fondo (25 Nov 2019)

The Tories race to the bottom has resulted in house improvement grants, photovolaic and next ground source heat pump grants vanishing next year. I get that the recession intervened, but where is all this heading?


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## Slick (25 Nov 2019)

screenman said:


> Times have changed then , I built this one 10 years ago and had to stuff them.


I renovated a block of flats about the same time and as part of the renovation the cotton wool (as I call it) cavity fill was hoovered out but it was sodding and when I told the council I didn't want my cavity refilled with anything they insisted on using the glued polystyrene balls and I could leave it out of the renovation but they wouldn't be financing the project. So I have been forced to use it, but thankfully it's not in every project.


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## Archie_tect (25 Nov 2019)

Grant Fondo said:


> The Tories race to the bottom has resulted in house improvement grants, photovolaic and next ground source heat pump grants vanishing next year. I get that the recession intervened, but where is all this heading?


They went before April last year... unless your region has not spent its quota?

Research money and support for PV and solar HW schemes disappeared here in 2017.... small businesses went overnight.


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## Grant Fondo (25 Nov 2019)

Archie_tect said:


> They went before April last year... unless your region has not spent its quota?
> 
> Research money and support for PV and solar HW schemes disappeared here in 2017.... small businesses went overnight.


I understand the renewable heat incentive ends next year for all UK.


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## Archie_tect (25 Nov 2019)

The last one we did had to be registered before end of March.

Got one coming through which would benefit so I'll check tomorrow! Thanks, GF!


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## Grant Fondo (25 Nov 2019)

Archie_tect said:


> The last one we did had to be registered before end of March.
> 
> Got one coming through which would benefit so I'll check tomorrow! Thanks, GF!


My mistake its the following year:

The *RHI* is due to *end* on 31 March 2021. The Government has not announced how it will encourage low carbon heating after 31 March 2021, or the supply chains on which it relies


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## Rusty Nails (25 Nov 2019)

I live in a 1920s house and called in BG for a quote for cwi but they surveyed the house and said the wouldn't do it because the house has had damp problems in the past and I've had new dpc put in.

I felt vaguely reassured that they turned down the money because they could foresee problems, rather than just going ahead regardless.


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## Slick (25 Nov 2019)

Rusty Nails said:


> I live in a 1920s house and called in BG for a quote for cwi but they surveyed the house and said the wouldn't do it because the house has had damp problems in the past and I've had new dpc put in.
> 
> I felt vaguely reassured that they turned down the money because they could foresee problems, rather than just going ahead regardless.


Good for them. Too many cowboys would have just done the job but that's what you get when you speak to real professionals.


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## Chris S (26 Nov 2019)

Slick said:


> The cavity is there for a reason, don't fill it.


I thought cavity walls were just introduced to save on bricks?


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## Levo-Lon (26 Nov 2019)

Chris S said:


> I thought cavity walls were just introduced to save on bricks?




A 9" wall uses about the same amount as a cavity wall, you still have inner and outer skin. 

This changes with modern builds as you often have just an outer brick with timber and plaster board ect


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## Drago (26 Nov 2019)

Got it at Chez Drago. Brick built bungalow, c.1960. It was there when we bought the house so I cant give a before and after. However, bungalows can be difficult to heat as they have a large external surface area in relation to their volume, and it seems pretty heat efficient. I can whack the heating off and it takes a goodly while for the air temperature to drop 1°C


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## johnblack (26 Nov 2019)

Our house is old so no cavities to fill, we used to have a real damp problem but about 15 years ago had a loft air vent fitted, we no longer have condensation, great bit of kit.


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## oldwheels (26 Nov 2019)

I live in a 1030’s flat in a block of four. I am bottom left and exposed to any wind from a south or east direction. Under some scheme which cost us nothing all the flats had the “ cotton wool” type insulation installed. Total disaster and following vociferous complaints it was removed and replaced with polystyrene beads and some sort of binder. Shower of cowboys but the job seems to be ok and again some Scottish Government scheme paid for it. A neighbouring local authority (or social housing ) house has just had the polystyrene fill installed and in addition there is an external cladding about 5 or 6 inches thick being fitted. We await results but since the tenants are respectable local people we should get an accurate assessment.


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## presta (26 Nov 2019)

I had a quote for cavity insulation years ago. Before taking the plunge I did some digging around, and found that the Cavity Insulation Guarantee Assoc (CIGA) have a well-earned repuitation for being a load of shysters who don't honour the guarantees. There was a debate in parlaiment about it not that long ago. The amount I stand to save on gas pales into insignificance against the potential cost of any remedial work, so I wouldn't touch the stuff with a barge pole.

(AIUI, the big no no for CWI is houses in exposed locations subjected to driving rain)


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## Slick (26 Nov 2019)

Chris S said:


> I thought cavity walls were just introduced to save on bricks?


So do most insulators.


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## Davos87 (26 Nov 2019)

Thanks you so much for all the input, advice and suggestions. Some very technical information too. On balance I’ve been more or less convinced not to proceed with it. House might be a bit nippy in certain parts but have no damp problems etc so will use the money I might save giving it a miss.... to buy a thicker coat. 😂 Cheers.


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