Retrofit airtightness - new windows

[SLABdan]

Hi all, 

 

Long time lurker here!

 

We're approaching the end of our retrofit of a 1960s house. Full IWI, membraned, battened, taped, MVHR, the whole lot. However, we didnt have enough funds for new windows at this phase so an exec decision was taken to progress and a few years down the line swap them out. Now I have a dilema (a nice one), our financial position has changed so we're in a position to replace, the only problem is that the old windows are taped in, insulated reveals and now skimmed 😅

Besides slicing the airtight tape tight to the old window and splodging in a tonne of airtight sealant during installation (masking my nicely skimmed reveals) does anyone have any other ideas. I'd prefer not to reskim every reveal (my plasterer - family friend will kill me). Other option I was thinking about was a timber lining to each?

Any pearls of wisdom amongst you clever folk?

[SLABdan]

This is the window section. Hatched areas are PIR. Green lines are airtight tape. Blue are concrete fixings. Cavity wall insulation also in there currently.

[TommoUK]

..get a cross section of your new windows and work out where it needs to sit. bear in mind the the best placement for thermal bridging (look at an accredited construction detail).  you may need to cut out some plasterboard and move the window back. personally I think it look better with a reveal rather than flush fit

[Dave Jones]

the issue with not fitting the windows in line with the cavity insulation means you need to insulate the reveals all the way round. 

 

Better to buy a pre insulated cavity closer, fit it then use airtighness tape to seal it to the inside blockwork. Fit and seal window as normal.

[SLABdan]

8 hours ago, Dave Jones said:

the issue with not fitting the windows in line with the cavity insulation means you need to insulate the reveals all the way round. 

 

Better to buy a pre insulated cavity closer, fit it then use airtighness tape to seal it to the inside blockwork. Fit and seal window as normal.

Reveals already insulated all the way around, everything is finished besides the old windows!

[Mike]

For airtightness I'd either use Iibruck FM330 foam or a bead or two of Orcon F adhesive in the joint, with a mastic or timber bead to hide the joint.

[SLABdan]

13 hours ago, Mike said:

For airtightness I'd either use Iibruck FM330 foam or a bead or two of Orcon F adhesive in the joint, with a mastic or timber bead to hide the joint.

Thank you Mike, will check those all out

[LowCarbonLiving]

Hi There,

 

Very new to the forums so a warm hello to all. My question is, are the current windows PVC casement with double glazing units ? I work in the Retrofit Industry, and we tend to rarely recommend window replacements, as the energy performance improvement rarely justifies it. If you are able to just replace the individual glass units (assuming they are faulty double glazed units), this would be a cost effective/environmentally friendly option. You can order units online to size that use low e glass , meaning you would end up with high performance windows with minimum cost (higher cost= higher CO2 footprint).

 

Hope this comment is not off topic as you may already have firmly decided to replace the windows (not liking them can be a strong and valid reason).

[SLABdan]

On 23/08/2024 at 23:04, LowCarbonLiving said:

Hi There,

 

Very new to the forums so a warm hello to all. My question is, are the current windows PVC casement with double glazing units ? I work in the Retrofit Industry, and we tend to rarely recommend window replacements, as the energy performance improvement rarely justifies it. If you are able to just replace the individual glass units (assuming they are faulty double glazed units), this would be a cost effective/environmentally friendly option. You can order units online to size that use low e glass , meaning you would end up with high performance windows with minimum cost (higher cost= higher CO2 footprint).

 

Hope this comment is not off topic as you may already have firmly decided to replace the windows (not liking them can be a strong and valid reason).

Thank you for the reply. The windows are uPVC, around 30 years old and have lots of issues; screw holes through frames (for blinds), some not sealing brilliantly and to be honest they look terrible also. If I’m honest I care less about co2 footprint and more about performance long term comfort that triple glazing will give me.