Church Sash Windows - Advice Needed

[Lynx]

We paid just under £14k to have four large sash windows replaced in an 1800s church conversion in the Scottish Highlands. The goal was to reduce heat loss in our home. As far as I can tell, the joiner did a nice job in recreating the exact form of the originals, including their curves and details, despite incorporating double-glazed heritage glass panels for improved thermal insulation. The lower sashes slide up and down relative to fixed upper sashes.

Originally the joiner used staff beads without any brush seals and unfortunately the windows were rather difficult to open - requiring initial wedging from the outside to open - and there were air leaks in places. After we raised this issue, the joiner replaced the staff beads with smaller staff beads that incorporate brush seals. He used a nail gun to secure them in place.

But whilst the windows certainly slide more easily now, there are many air leaks in places where the brush seals fail to make contact and also between the staff beads and the frames to which they are attached. By air leaks, I mean feeling cold air pressing into your hand when it is cold outside. Misalignment in respect of the staff beads is also apparent because there are visible gaps between the lower sashes and parting beads when viewed from the outside, and if I press on the relevant corners from the inside, there is significant movement of the lower sashes. Also, when looking from above, one can see uneven gaps between the lower and upper sashes, particularly in one of the sash windows.

My gut is that the staff beading needs to be sized a little larger with a larger brush (or alternative seal?), better aligned against the lower sashes and more tightly pressed against them.

But actually I am also wondering whether to give up on the sash functionality altogether and simply fix the lower sashes in place and ensure air tightness all around. Given the size of these windows, slight leaks add up over large areas and tend to result in significant heat loss.

With these large windows spanning two floors, to what extent is achieving reasonable air tightness whilst ensuring ease of opening from the inside actually feasible?

I tried contacting various sash window experts, but they all seem booked up for about one year and unwilling to work on anything other than complete replacements.

I'd really value any thoughts or suggestions on the work undertaken and next steps going forward. We are on good terms with the original joiner and I can always ask him to come back, but I need to know whether to persist in trying to maintain the sash functionality or simply opt for fixing the lower sashes in place.

I enclose images below and here is a short video clip: https://photos.app.goo.gl/dqhfK44rgZm3acXn7

 

[fernicarry]

The sashes themselves look well enough fitted. Can't really tell from the pictures where the uneven gaps are. Don't give up on having them operative just yet. We do occasionally get a few warm days where ventilation from working windows is useful!

The baton rods (which is what we call staff beads in Scotland although I'll admit I always call them staff beads...) are a bit rough and out of proportion so I'd say you need another iteration on those with your joiner. Do you have a before picture to show how they were originally fitted and how they meet the curved piece? I guess he started off custom making them to the right size but without the brush carrier and now he's switched to off the shelf ones which are too small for your application.

Has the join between the staff bead and the frame been sealed with mastic? If it isn't then air will leak round the back of it bypassing the brush. Do the parting beads also have an inward facing brush? Is there any sort of seal at the meeting rails?

I struggle with a few of my windows because of quite an uneven and wide gap between sash and frame so they can run off the brush strip. The carrier on the staff bead is sometimes offset to one side so be sure its been fitted with the larger gap towards the frame to get the brush to overlap the sash as much as possible.

The brushes themselves do come in different lengths which can help with tolerance where the sash is winged.

 

[Lynx]

Thank you for the reply!

Do you have a before picture to show how they were originally fitted and how they meet the curved piece?

Nice idea to look at the original photographs if that is what you meant. Comparing against those, the situation has been clearly improved a great deal.







Looks like the original staff beads were rather better proportioned and aligned:



Here is another view:

I guess he started off custom making them to the right size but without the brush carrier and now he's switched to off the shelf ones which are too small for your application.

This is my thinking too. So that makes me wonder now: to what extent is it possible to make custom staff beads that can receive brush seals?

Has the join between the staff bead and the frame been sealed with mastic? If it isn't then air will leak round the back of it bypassing the brush.

Not yet. And I also figured this would help to a great extent with the air leakage. Is mastic the right stuff to use mindful of the desire to paint over and thermal expansion? Of course in our case the staff beads first need to be replaced it seems.

Do the parting beads also have an inward facing brush? Is there any sort of seal at the meeting rails?

No they don't. Should they? Here is a view of the parting beads:



My feeling is that these are true vertical, but I can't be certain. There is certainly misalignment between the lower sashes and these given gaps at the top (a gap between parting bead and lower sash can be seen in both photographs above - the parting bead and lower sashes are well-aligned lower down, but then travelling upwards from the bottom, towards the top of the lower sash a gap emerges). I believe this is caused by the inside staff beads not being well-aligned and not pressing the lower sashes hard and/or uniformly enough against the parting beads. I think this because if I press the lower sash upper corners there is some movement, which I think results from slack caused by lack of pressure from the inside staff beads. Of course both could be out of alignment, and this would make the whole situation more complicated to deal with, right?

I also have a general question about brush seals. Are they the way forward? There are other kinds of seals too I believe, and I really want to try my best to ensure we get this right this time round.

Is there any sort of seal at the meeting rails?

Yes there seems to be a well-crafted seal between the movable lower sashes and upper sashes. They even manage to seal a huge gap between the sashes on the third window from the left, which gap I think results from the misaligned staff beads.

The brushes themselves do come in different lengths which can help with tolerance where the sash is winged.

Yes so larger, better proportioned custom staff beads and larger brushes to be fitted thereto, right? Or is it more a question of better alignment, since if the brushes are too large won't that also cause a problem?

Admittedly I have the feeling getting the alignment right with this sizing is rather tough because of the lengths involved. Larger brushes will allow for more tolerance but then I imagine one wants the staff beads pretty tightly pressed in, and hence this might distort the brushes if too long(?).

Would going brushless as the joiner had originally intended work in this situation? Is there a way to try without brushes, but then add brushes later with a different kind of brush seal that is not integrated with the staff bead?

When we bought the house the lower sashes were fixed in place. I don't know if there would have been brushes originally or not. I presume there were no brushes back in 1850 or so when these were originally made.

 

[fernicarry]

o what extent is it possible to make custom staff beads that can receive brush seals?

Should be no problem for a joiner with a workshop. I'll probably make them myself for the next window when I get around to it.

Looks like they were originally flush with the front of the reveal but it also looks like the original sash was sitting a bit more inwards. Hard to tell scale from the photos. The new sashes themselves may well be thinner although with DG units they can't be that much thinner, or he might have used a thinner parting bead. In Scotland it should be 14mm thick, but in RoUK its more like 9mm. Yours don't look that thin though.

Not yet. And I also figured this would help to a great extent with the air leakage. Is mastic the right stuff to use mindful of the desire to paint over and thermal expansion? Of

With no brushes on the parting beads and no seal to the back of the staff bead that explains why you are feeling such a draft as there is basically nothing stopping air coming in around the side of the sash. Getting both of those sorted should help considerably. Getting the parting bead back out now that the cases are fitted could be a bit of a faff and won't do the nice spray finish any favours unfortunately.

Decorator's caulk should do the job or you might want to use something like Acryrub SWS that claims to be more airtight, its just not as pleasant to use. The mastic should deal with any seasonal movement. Have to admit none of my overhauled windows have the staff beads permanently fixed in place yet! Give me a few more years and I might be confident enough that I'm done with tinkering to do that...

if I press the lower sash upper corners there is some movement

They are tall windows so a bit of unevenness is to be expected. I wouldn't expect you to have to push hard on a new sash to get it to line up though. If you have a long spirit level (or something you know is dead straight) put it over the face of the window in various orientations to check that they are indeed flat. The brushes on the beads can only exert so much force before it becomes difficult to move the sash so you are relying on things being quite well lined up to get them to operate smoothly whilst remaining sealed. It could be the staff beads themselves just haven't been fitted straight. Being so slim they will bend quite easily.

Would going brushless as the joiner had originally intended always tend to fail here? Is there a way to try without brushes but then add brushes later with a different kind of brush seal that is not integrated with the staff bead?

I'm surprised that a joiner in this day and age would make replacement sash and cases without some provision for weather seals but that seems to be what has happened. Of course originally there wouldn't have been any seals which is why sliding sashes get a reputation for being drafty and not operating terribly smoothly. The brushes fix both those problems. The staff and parting beads are really the only places to put the seals because you have the cord running up the edge of the sash itself.