Cavity Wall Insulation - will it cause dampness or any problems?

anotherdollar

i've got a pre-1900 house (end of terrace). I'm thinking about having wall insulation, but I am worried about causing internal dampness or other problems. Should I be worried?

tony6403

Have had polybead insulation for many years with no problems.

har0ld

No. most modern cavity wall products will not bridge the cavity.

anotherbaldrick

har0ld wrote: »

No. most modern cavity wall products will not bridge the cavity.

It can cause dampness if there is morter droppings on the wall ties. Without cavity filling the air movement in the void will evaporate moisture and stop dampness crossing. With cavity fill the air circulation is greatly reduced and the moisture then will not be evaporated and can cross on a mortar covered wall tie and cause a patch on the inside wall. This happened on our last house.

MX5huggy

Pre 1900, are you sure you have cavity walls?

tony6403

anotherbaldrick wrote: »

. Without cavity filling the air movement in the void will evaporate moisture and stop dampness crossing. With cavity fill the air circulation is greatly reduced and the moisture then will not be evaporated and can cross on a mortar covered wall tie and cause a patch on the inside wall. This happened on our last house.

In your scenario where is the air circulation coming from ??

anotherbaldrick

tony6403 wrote: »

In your scenario where is the air circulation coming from ??

In an unfilled uninsulated cavity wall void the air does not remain static, if it did, you would not be thinking of wall insulation as static air is a good insulation material. The air circulates in the void by convection , by picking up heat from the face of the inside wall and rising and loosing heat to the face of the outside wall leaf. Grade 1 Pysics. That is the purpose or cavity fill , to hold the air static between the voids of the fill, that is how insulation works but for the reasons I stated it can cause damp to the inside if the wall ties are not clean of mortar . A reputable insulation contractor will check the wall ties before filling the void, not many do !
A house location where it is exposed to wind driven rain should probably avoid retro-fit cavity insulation -- REFER TO BUILDING REGULATIONS

travellerboy

anotherbaldrick wrote: »

................. Grade 1 Pysics.

Firstly the OP is highly unlikely to have a cavity wall, so no decision or dampness worries.

Air has a high conductivity Value and is a good heat transfer medium. I think you meant a Vacuum which has a high insulating value.

How do the Reputable Installers check for contaminated wall-ties? Intrascopes, demolition or what?
Existing dampness is the test for contaminated wall ties.

Anyone considering Cavity Wall Insulation should seek expert advise from a Chartered Surveyor before hand and not listen to the Installers or the Energy Trust.

anotherbaldrick

travellerboy wrote: »

1)Air has a high conductivity Value and is a good heat transfer medium. I think you meant a Vacuum which has a high insulating value.

2)How do the Reputable Installers check for contaminated wall-ties? Intrascopes, demolition or what?

3)Existing dampness is the test for contaminated wall ties.

Anyone considering Cavity Wall Insulation should seek expert advise from a Chartered Surveyor before hand and not listen to the Installers or the Energy Trust

1) Go To :-
http://www.ucar.edu/learn/1_1_2_6t.htm

Some solids, such as metals, are good heat conductors, while others, such as wood, are poor conductors. Air and water are relatively poor conductors and thus are called insulators.

2) They check by removing a brick to inspect or use a scope .( I did say not many bother)

3) Evaporation of moisture by air circulation in the void can prevent a contaminated wall tie from causing dampness UNTIL THE VOID IS FILLED. Then it shows up !

PS. I hope you are not a Chartered Surveyor because if you are you should have known the above !

UncleZen

har0ld wrote: »

No. most modern cavity wall products will not bridge the cavity.

Thats exactly what they do.
Explain to me how a cavity full of poly beads, or blown fibre, avoid touching the sides of the cavity.

In *new* builds a cavity is maintained.

fenwick458

if your house is pre 1900, you won't have an open cavity. it will be back filled with rubble most likely.

so if you want insulation, you would need to stud the walls out and stick some sheets of insulation inside the stud, then plasterboard and skim. unless it's freezing cold and costs a fortune to heat i wouldn't bother