to fill or not to fill...

[Packman]

I'm about to start renovating a 1950s house, uninsulated cavity wall brick and block construction.

 

I was planning on wrapping the house in EWI and finishing it with brick slips on the ground floor and render on the 1st floor. I am getting mixed reviews as to whether or not to fill the cavities, so would love your thoughts...

 

Some are saying to do a full fill on the cavity - the EWI will ensure the wall is watertight so no issues of damp etc by filling the cavity, and they say that if I left the cavity empty it would just allow all the heat from inside the house to escape up the empty cavity and would mean the EWI would be pointless. 

 

However others are saying to leave the cavity empty and just seal it at the top and around the windows etc, as the air in the cavity will act as an insulator anyway, and they say that the EWI will be more than sufficient and the house needs the air in the cavity to help it breathe and filling it with insulation would not be a good idea. 

 

What are your thoughts?

 

 

 

 

 

Edited January 24, 2021 by Packman

[nod]

I would leave the cavity open 

The EWI is an excellent insulator 

I recently rendered a house for a friend who had a similar dilemma 

[Mr Punter]

Either will be fine but it is vital that the cavity is sealed and no air from the cavity can escape to outside.  The top of the wall at loft level is the most vulnerable.

[Packman]

thanks @nod and @Mr Punter.

 

What are the pros / cons of doing a full fill vs leaving empty, when adding EWI?

 

[nod]

As P has pointed out Sealing the inside is the most important 

Pro and cons Just cost 

If you have it in the budget You could do both My mate was on a tight budget and hasn’t got round to paying me for the render He did say he’d take me for a pint 

Still waiting ?