Penetrating Damp and Parex with insulation

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blackbirdxx

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I have an 1890’s house made from solid brick (no cavity) with upstairs walls which are rough cast rendered with S&C. Some of the upstairs exposed walls are suffering from penetrating damp which is getting trapped behind the render. I have discussed this issue before on this forum and decided to remove all of the roughcast render and replace with a throughcolour breatheable render such as Parex. I have found a recommended renderer experienced in the use of Parex who has now suggested I consider the use of external insulation fixed directly to the brickwork once the render is removed. Despite this being appx 40mm thick once rendered it can be accommodated as I have a brick drip running around the house standing proud from the wall half way up. My question is, should I go with this suggested course of action or stick with the Parex option without the insulation allowing the walls to breath dispersing any trapped damp. Bear in mind that my main problem is penetrating damp.
Thanks in advance for any assistance…
 
Fix the penetrating damp problem. Simple.

Should the house be clad with Ewi correctly then there should be no way of ingress for penetration. Its that simple.
Ewi will prevent the condensating damp that solid wall suffers from also.

Only thing is if you are paying for Ewi you should try for more than 40mm thickness.
 
your going to want 90mm eps or 70mm of phenolic insulation to get it to building regs of 0.30 if theres no cavity.
40mm only gives it around 0.46 u value
 
Ewi is not the only way to solve this problem,although a good option it will cost you.
Look into other options as there are a few.
 
Thanks for the responses guys.

The problem with having more than 40mm of insulation on my house is that it will stand too proud of the wall, bearing in mind that this is proposed for upstairs only. I do have a brick drip running around the house half way up the wall which will accommodate a 40mm thickness. I do take your points re ‘u’ values etc but I’m concerned that anything greater than 40mm will make the property look strange.
 
IMO 40mm of insulation is a waste of money, either go the full hog or don't bother with insulation at all.
 
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