Advice on draughty sash windows

Hello, I wondered if anyone can help. My partner and I have recently bought our first home together on the Forest Hill/Sydenham border. Over the winter our new flat was freezing even with the heating on full blast. We have 6 very draughty single glazed sash windows, including a large bay window at the front of the property.

My question is… do you think we should replace the windows entirely with new double glazed windows, or can we make it warm by renovating the existing sash windows? We don’t have loads of money. It would be great to hear from other locals living in period properties and find out how you have dealt with this issue.

Thanks

I have 4 large single-glazed sash windows in my flat which were very draughty. If the wind was in the west, I could see my curtains flutter in the breeze.

I chose to get mine renovated but be warned, it’s not cheap. Admittedly, I had a couple of really dodgy frames, one of which had the bottom sash remade. I also got them draught proofed and it made a huge difference. The expanse of glass can still be chilly so some lined curtains also make a difference. I can’t recall exactly how much it was - but I think it was around £2k. I was recommended the Sash Guy via the East Dulwich Forum and he was very good.

Bear in mind that you can’t simply change existing sash windows into double-glazed ones. Because sash windows are balanced with their weights, double glazed ones would be too heavy for the current weights so you’d also have to pay for new weights. I seem to recall that entirely refitting them to double glazing was going to be 2-3 times the price.

I also seem to recall that renovating existing ones doesn’t require building control whereas replacement ones might? Double glazing ones can be easier to open/clean but might also depend on what your neighbours have and whether you need them for noise reduction as well as heat retention.

I have installed the storm guard brush seals that are brush seals and allow the sash windows to slide. This is the cheapest option and does help with some of the draught but you will still get the cold transfer through the glass. We have painted our sash windows shut on the ground floor that also is a security measure and sorts the drafts - we would never open them anyway as we have enough air circulation from open floorboards. The double glazed pvc sash windows with run through horns and heritage features are now really good and hard to tell the difference from a distance and given the maintenance savings this is our plan in a few years - they are expensive. I have taken out the sash windows and refurbished them on the first floor that is not too difficult but time consuming as you need to put them back in between coats etc. However it does mean that you can paint them and the frames without a ladder as once the sash parts are out it gives great access to paint the outside frames from within. We have installed shutters inside and it does keep it slightly warmer when closed but again not cheap. Planning is always required for a flat to change windows as no permitted development rights exception and a house depends on whether it is in a conservation area but best to check with Lewisham planning.

The previous owners of our house installed internal secondary glazing. Ugly buy very effective. Also surprisingly effective is the plastic film where you tape over the window frame and use a hair dryer to make it shrink to fit. We did this a few times on windows we knew we wouldn’t need to open. But you have to make sure there is other ventilation.

When we came sort out the windows, we did a mix of refurb and replacement. We also used The Sash Guy from East Dulwich and would recommend him. We only refurbed and brush sealed windows that were in reasonably good nick. With the replacement ones we didn’t need any building control because we were replacing the sash unit inside the window frame and didn’t remove or replace the frames themselves. We put in double-glazed unit and as noted about, the new lead weights add a lot to the cost of these.

I used to live in a very similar house in FH and had the same issues. I used secondary glazing plastic film, available form Homebase, B&Q etc. Was amazed at the difference for the sake of around £16. Once on you barely register it is their. Also reduced outside noise quite a bit.

Hello @Julia_Minnear , are you located within the Forest Hill Conservation Area?
https://www.lewisham.gov.uk/myservices/planning/conservation/conservation-areas/Documents/ForestHillCAExtensionsOSA3Jan2011.pdf

If you are, unfortunately, the Council’s attitude towards UPVC replacement windows is completely backward, given that there are some very good manufacturers who make sash windows with the correct proportions and through-horns etc and which are waaaaaaaay cheaper than wooden replacements - or refurbishment of old originals.

To give you some example - even though you won’t see the horns, which are external -

This window is 3 units joined together so it was priced accordingly, however, the centre unit is 7 feet tall and 3 feet wide and it cost £380. It has 25mm argon-filled double-glazing and the sashes are tilt and slide. Importantly, the lower sash has a deep bottom rail, which is critical in terms of aesthetics.

So, if you’re outside the Consevation Area - BINGO!

Hi, interesting to know what company supplied and fitted your sash windows as under £400 is cheap.

Hi John

Do you happen to have a link to Lewisham’s specifications for windows in the conservation area?

Hi @Chipcity

The guy is on eBay, but don’t be put off by that because I’ve used him a few times and the service has been spot-on every time.

The window in this link doesn’t have the deeper bottom rail but you can specify that on the order form. https://www.ebay.co.uk/itm/UPVC-Sash-Windows-Run-Through-Horns-Sliding-Sash-Any-Size-329-Inc-VAT/272104885897?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

I’d be happy to help you understand any of the jargon or features if you want.

Sorry @DevonishForester , I’ve had a good look on Lewisham’s planning pages but I can’t find it. I’m sure it used to be on there. I’ll have a dig through my old paperwork to see if I’ve still got a hard copy that I printed-off a few years ago.

Lewisham’s rigid wooden-over-UPVC argument was, I’m sure, based upon seeing some poor attempts at replicating the essential look and aesthetics of an old window but all UPVC sliding sash windows are not the same!

I think he might be the same person as colinssashwindows.co.uk. I spoke to him on the phone and his prices are great. The windows are synseal evolve. My builder recently fitted 4 for me, purchased from fascia place, but I intend to buy more from this chap.

There’s some great advice and recommendations here. @moderators can these become a category in recommendations?

Yep, Colin’s the man!
And the EU lady who I’ve dealt with on the phone is so helpful.
Great firm.

Good idea. Perhaps we could add a heading to the recommendations page for general “neighbourly advice” topics like this.

You should be technically able to edit the recommendations page yourself (it’s a wiki topic) and I’d encourage established members to do so. Only condition is that the topics listed there are for general recommendation lists, as opposed to recommendations for individual companies.

Yes, there are some excellent UPVC sash replacements. I would be interested to hear from anyone in the conservation area who has navigated this with Lewisham Planning.

Historic Windows Guidance.pdf (193.7 KB)

This is a few years old, but was sent to us when we were looking to replace rotten windows.

Perhaps the insistence on wooden sash replacement should be assisted with a grant?
As modern sash windows are excellent replicas, coupled with ease of cleaning and sound and heat insulation. Difficult but surely conservation of energy trumps draughts and maintenance and without a trained eye no apparent difference.

I should add that some changes are ridiculous with outward openings and ‘georgian’ panels and certainly see a point of view where totally incongruous windows are fitted. Maybe the planners should have a recommended design/supplier?

I agree with you @Wynell .
On the planning part, at least their guidelines should stipulate minimum ‘heritage’ design features such as ovolo glazing bars, deep bottom rails and run-through horns?

Thank you @Sandinista, this document is the one I was looking for - but it really winds me up!
Yes, in an ideal world (where slow-grown softwood and craftsmanship cost the same, relatively speaking, as it did back in the early-1900s) people would all be able to afford to do like-for-like replacements - but they can’t. So, as preserving the look and the character of an area can essentially be achieved by using a modern, less-expensive material and manufacturing process, I find it really annoying that many local authorities are still digging their heels in on this.

Since this topic has evolved into a slightly more general discussion of windows and seems as good a place as any to ask, can anyone advise on “soundproof” windows? The recent re-introduction of fast Thameslink services (I live near the rail line) has me contemplating trying to improve soundproofing but having looked online I’m not quite clear whether you need specialist windows or whether decent double-glazing should do the job. Is there a rating system for sound-proofing and is there a stage where you are paying significantly more for only marginal gains - i.e. what is the sweet spot in terms of cost to significant (but not necessarily complete) sound-proofing?

Any thoughts, experience or recommendations appreciated.

We used Magnaglaze for our sash windows. They supply precut polycarbonate panels with magnetic stripes on the edges. You offer up the panels to the frame and the result is that you really can’t see the secondary glazing and the sound and heat insulation are excellent. They also make a version for people who want to open their sash windows.

Our builder told us that the heat loss through the cracks in floor boards greatly exceeds heat loss through draft y windows
We had insulation installed under the floor boards and it made a huge difference to temperature and comfort.

Real soundproofing costs a packet, I believe the recommendation for glazing is a 75-100mm air gap. Which due to thermal activity then reduces the effectiveness of heat insulation.
There is laminated glass which is a sandwich where the inner section is a plastic film vibration reducing feature.

Basically its cost v benefit

Hi, thank you for details and it looks good especially his feedback on eBay.

May I ask, did you replace or repair? It would be helpful to hear from someone in the conservation area who secured permission to replace timber with UPVC.

The Historic Windows Guidance sounds rigid:

“If the original window does need to be replaced, it should be in the original style and material. It should be replaced exactly ‘like for like’”

Strangely the document also says --" Depending on age and style of the building, the glazed area of the sashes can be subdivided with glazing bars into smaller panes." Surely subdividing the the window into smaller panes would make greater visible change than good quality UPVC sash replacement?

Exactly!
Another thing is, I’ve seen some pretty amateurish-looking wooden replacement sash windows that aren’t as good as these UPVC ones.
I have a feeling that the existing guidance is old and, due to the advent of these sympathetically-designed UPVC replacements, needs to be updated .

Hi there - we replaced our windows, as they were in pretty bad nick and we wanted to double glaze. They’re not actually sash windows though - we have quite large casement windows with Georgian bars, so it was a big (and expensive) job. Ours are timber.

Try this: https://www.gapseal.co.uk/ It worked for my sashes and you can take out in the summer and re-use in the winter. Cheap as well. But depends on how bad yours are, obviously.

Also, if you have any cracks or rotten timber in the sashes, definitely look at https://www.repair-care.co.uk/product/dry-flex-4-3/

I had bad timber decay in two of mine and thought I was looking at new sashes or at least a major repair, but was put on to this by a sash specialist I rang, but who was too busy to help. Worked perfectly and saved me hundreds.

My advice is shop around. The main company in this area, which I won’t name, is grossly over priced in my opinion. But they have a waiting list / a lot of business so I guess they are doing something right.

But as someone said above, we thought it was the windows, but in reality most of the coldness was actually coming from the floorboards. But you need to have airflow under the house to prevent damp etc. So it’s a balance.

You don’t need to have the coldness entering the room (through the floorboards) to prevent damp though.