Can cavity wall insulation cause damp in the house?

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I used to have a problem with damp in my house, but after someone drilled an airvent in the wall, this problem disappeared. I am now considering cavity wall insulation to save on heating bills but read somewhere that " cavity walls came in mainly because the gap between the bricks (cavity) prevent damp".

Does this mean that closing the gap with the cavity wall insulation could cause me to have damp issues again?

Thanks in advance
 
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If a vent solved the probelm, then the probelm was condensation, and insualtion will help this and not make it worse.
 
I used to have a problem with damp in my house, but after someone drilled an airvent in the wall, this problem disappeared. I am now considering cavity wall insulation to save on heating bills but read somewhere that " cavity walls came in mainly because the gap between the bricks (cavity) prevent damp".

Does this mean that closing the gap with the cavity wall insulation could cause me to have damp issues again?

Thanks in advance
Having been a cavity wall surveyor for some years let me put your mind at ease.
In years Gone by cavity wall where filled with foam but most companies now use rockwool which allows your wall to breathe but aslo stops water entering through the exterior wall I have done thousands of properties and not one has had a problem. The saving from having proper Insulationin the roof (ideally 12") and cavity wall insulation is around 40% of your annual exsisting fuelbill.For peace of mind only only use a BBA registered company recommended by the government
Hope this helps
 
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Cavity wall insulation should not cause damp but it can exacerbate an existing damp problem. Killersharky is technically wrong in saying that it stops water entering through an external wall - the bricks and mortar do that. What I think he meant is that the mineral wool will not act like a sponge and draw moisture across from the outside to the inside. However it will allow moisture to move vertically ( downwards ) due to the effect of gravity. As the moisture decends it will ultimately spread out and could ( as in my case ) act as a conduit between the outside and inside walls.
I have recently removed bags and bags of sodden mineral wool insulation from my house which caused an major damp problem in one of my walls. The origin was cracked render and poor brick pointing but without the cavity insulation there would have been no way for the moisture to migrate from the outer wall to the inner wall.
The key to retaining the efficiency of the insulation is therefore to ensure that your outside walls are sound, with good brick pointing and no leaking gutters etc.
I am of the opinion that the cavity wall insulation company should have spotted these issues with the outside wall and made the previous owner aware when carrying out their survey or prior to starting work but I suppose that it was not in their economic interest to do so.

ps. I have the receipt of the company that installed the insulation and YES they are an approved installer. Possibly as useful as an NHBC guarantee then.

HRH
 
Filling a cavity with anything is a breach of the UK Building Regulations. However, from a technical perspective, I would just like to mention that the purpose of the external skin of brickwork is to act as a shield and provide a level of protection from penetrating rainwater; worst affected are the South Westerly and North Easterly elevations as these are the prevailing wind directions in the UK, and the wind pressure acting on the wall of a building in stormy conditions assists the rainwater in penetrating the brickwork - in highly exposed locations the rainwater penetration into the cavity can be quite severe and cause the penetrating rainwater to enter the internal envelop of the building.

There are several areas of concern with installing cavity wall insulation - in some situations it can aggravate an existing condition by providing a path by which rainwater may more easily enter the building.
If a full cavity fill fibre insulation is installed the insulation will (not 'may' depending on the severity of the exposure) either become damp (at best) or saturated (at worst) either of which will adversely affect the performance of the insulation material, also because the cavity can no longer effectively breathe mould growth will be encouraged which will bring with it its own set of problems.

Comment should be made on urethane insulation, which is usually injected into the cavity - this is a very good system, as urethane has the intrinsic quality of providing a vapour proof barrier and is not be affected by rainwater penetration.
One of the major complaints with urethane is the fumes that are given off during curing, which drift into the interior of the building and can be quiet over-powering and offensive to some occupiers.

There is no doubt in my mind that cavity wall insulation can provide long term benefits by providing a warmer home with reduced winter fuel costs (which directly equate to reduced carbon dioxide emissions), but cavity wall insulation is definitely not a 'cure for all ills' and its use in post occupancy cavity wall insulation needs to be considered carefully.
 
Filling a cavity with anything is a breach of the UK Building Regulations.

Where does that come from? :eek:

Also, the extent of rain penetration to an external wall has less to do with exposed conditions, but more to do with the quality of construction, the absorption capacity of the bricks and quality of the pointing.

Wind pressure is not a factor, but duration and severity of driven rain is.

Interestingly, a more absorptive brick is less likely to experience rain penetration than a dense brick,so again its less to do with the actual weather

Rainwater will tend to run down the rear face of the external skin once saturated. Whilst it can go horizontally if a route allows, gravity, time, evaporation, heat (from the inside) and suction (from the outside) are all acting against it.

The health issues and allergic reactions to urea-formaldehyde foam should not be underestimated. Once this is used, if the occupier does suffer a reaction, then the only recourse is to move out

Basically, there are few issues with retrospective cavity insulation. But it may highlight and heighten existing problems with the wall construction

Many installation companies will try and make up for a poor survey with a myriad of get out clauses within the contract
 
A wall built with a less porous brick such as an engineering brick can let in more water if there are cracks in the bed joints. This is because even in a light shower all the water runs down the face and into the crack. With a more porous brick the water is absorbed evenly throughout the wall and doesn't always penetrate the interior. It can then evaporate out.
However if all the joints are watertight then the engineering bricks should be OK but because they are usually built with a strong mortar there is a tendency for the joints to crack.
 
illersharky";p="1146645"]
I used to have a problem with damp in my house, but after someone drilled an airvent in the wall, this problem disappeared. I am now considering cavity wall insulation to save on heating bills but read somewhere that " cavity walls came in mainly because the gap between the bricks (cavity) prevent damp".

Does this mean that closing the gap with the cavity wall insulation could cause me to have damp issues again?

Thanks in advance
Having been a cavity wall surveyor for some years let me put your mind at ease.
In years Gone by cavity wall where filled with foam but most companies now use rockwool which allows your wall to breathe but aslo stops water entering through the exterior wall I have done thousands of properties and not one has had a problem. The saving from having proper Insulationin the roof (ideally 12") and cavity wall insulation is around 40% of your annual exsisting fuelbill.For peace of mind only only use a BBA registered company recommended by the government
Hope this helps[/quote]
 
Here are some important things to be taken into account when having cavity wall insulation installed, otherwise it could result in the insulation needing to be removed/extracted.
Survey ;
Are there gutter problems or finlock gutters? Property exposed to wind driven rain? Condition of the render and brickwork; all fuel appliances inc. fossil fuel, gas, oil and type of flue. Open flue fossil flues and oil over fifth required vent - open flue gas fuels over 7kw requires a vent. All flueless appliances and backboilers require a vent, but balance flues generally do not. This is only a rough guide.
Make sure there is good access around the property for ladder, also getting over conservatories / sheds could these pose a problem? Gables however can be drilled and filled from inside the loft if necessary. Check sash windows are boxed in. Check every elevation for rubble and debris in the cavity and that it's not already profiled. Check air bricks to see if they are sleeved and how many need to be repaired. If a barrier needs to be fitted because your neighbour has not had their insulation done, ie semi or mid terraced houses.
Unfortunately, surveyors are mostly salesmen and are commission based, they will probably complete a survey in just 10 minutes.

Installation ; the installers should be checking everything the surveyor has previously checked. Change and sleeve subfloor vents for wooden floors, the same with room vents, especially kitchen and bathroom vents, as these are the rooms which produce a lot of moisture. Check the appliances for ventilation requirements, most fires and boilers have a plaque on them with the fire/boiler ratings. This also applies to appliances on an inside or a outside wall, as when you have cavity wall insulation installed, the air flow will change around your property. An appliance on an outside wall will require a smoke check, or flue test - before and after installation so not to fill up the flues.
Barriers to be fitted if needed (by drilling a hole at the top and a hole at the bottom) dropping a long chain to hook out of the bottom hole to allow a large brush to follow, staying in the walls so the insulation doesn't fall into the next door neighbours property!
Some mispractices can include;

Stopping the insulation machine too early - causing voids, not having the machine set up right - blowing material in too fast. A box test or flow rate check (depending on the material used) must be carried out before every job, recording the time and weight. Not changing the subfloor vents for wooden floors - they may put a brush over them or blow air brought them, this is not acceptable. Not fitting a cavity brush. Incorrect drilling pattern. Not smoke checking appliances before and after (outside wall appliances) THIS IS PARAMOUNT. Check inside your loft for any overspill, check they have stapled a flue test certificate in the loft. Nobody should be installing the insulation below where someone is above them drilling holes, as drilling will cause shards of brick/debris to fall on the insulation in the cavity - causing it to bridge and cause you problems.
 

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