Cavity wall insulation and window replacement

[minilathe22]

We are currently living in an ongoing "doer upper" house and at some point in the future we are planning to replace all the windows and doors, and to have cavity wall insulation installed. I am wondering if it is better to do one before the other? My current thinking is that we should replace the windows first, and then the cavity wall insulation after, so that the insulation does not get disturbed by replacing windows.

Is there anything else I should consider? As I understand it cavity wall insulation is not recommended where you get alot of driving/sideways rain, but we are in the south east and I don't think that should affect us.

 

[Ollie78]

Windows first I would say, I just put some window boards in a house with some kind of blown in cotton fibre insulation in the cavity and it was trying to escape a bit and float about.
Think hard about cavity wall insulation, it may not be appropriate. I know a few properties where it caused problems and they had it removed.
You may be better insulating inside the envelope or even outside, depending on the building type. And leave the cavity to do its job.
Do your research.


Ollie

 

[novocaine]

get the walls checked by someone with no vested interest in installing cavity wall insulation. this comes from experience of having to pay 5k to have it removed after the previous owner had it installed in a property with a gable end that faces the prevailing weather and has a porous warrington brick on a raft.

 

[Woody2Shoes]

We are currently living in an ongoing "doer upper" house and at some point in the future we are planning to replace all the windows and doors, and to have cavity wall insulation installed. I am wondering if it is better to do one before the other? My current thinking is that we should replace the windows first, and then the cavity wall insulation after, so that the insulation does not get disturbed by replacing windows.

Is there anything else I should consider? As I understand it cavity wall insulation is not recommended where you get alot of driving/sideways rain, but we are in the south east and I don't think that should affect us.

What vintage is the house?
I'm sure you know that replacing windows is covered under Building Regs - e.g. on thermal (U value, trickle ventilation, also cold bridging) and structural (some window frames help to hold the wall up), and possibly security aspects.

In an ideal world it shouldn't matter which order you do it in. I agree with the earlier posts suggesting caution re. retro-fitting cavity wall insulation. Even in SE England, if you're in an exposed location - or the "rain-screen" effect of your outer skin of masonry is poor - then wind-driven rain can cause real problems. Tell us more about the construction details of the walls (upstairs and downstairs).

 

[minilathe22]

To my untrained eye its a double skin wall, one brick wide with a cavity. Very ordinary looking red bricks. It is a semi detached house, probably 1950s build, with a conservatory and car port on the lower level which means the walls in those areas don't get any rain at all. Upper storey does get some of course.

 

[Woody2Shoes]

So all the externally visible brickwork upstairs and downstairs is in 'stretcher bond'?

Do you have any clues (e.g. from drilling holes in the past) what the inner skin of masonry might consist of and what ties exist between the two "leaves"?

https://www.forterra.co.uk/technical/brickwork-specification-choices/

 

[minilathe22]

Yes Stretcher bond style, and "textured" according to that website.

I can see wire joiners across the two walls.

 

[minilathe22]

I can see online "cork spray" which is 6mm of cork on the inside of the walls, instead of filling the cavity. I wonder how this compares efficiency-wise with a few inches of insulation in the wall cavity.