Double Glazing or not?

[mikej460]

Thanks for the reply I think that's effectively what I'm trying to achieve to have a well designed window to remove my concerns of the double glazed units that can break down. I agree with he thermal problems with the single glazing but know I can make these well.

I really like the idea of double glazing by virtue of 2 casements effectively I would see this as not really different to secondary glazing with then the option to close shutters for further gains. I suppose really I like making things that last my virtue of good design and well executed joints and good standards of materials and workmanship.

I may have misunderstood what you are saying here Kieran but just to re-iterate that if you are fitting new frames you can't fit single glazing. Unless you are Fensa registered you must notify Building Control. I would advise against not doing this as a nosey neighbour could dob you in (I speak from bitter and ultimately expensive experience here) the rules are explained here Building Regulations | Doors and windows | Planning Portal

Our 19th century community pub (owned by the village) needs new front windows and the local company we have asked in to quote are recommending replacing the frames with Accoya Wooden windows, external wooden doors, timber windows, window frames (accoya.com) fitted with 12mm DG heritage glass. The existing frames are softwood and despite shelling out for rot to be replaced over the years they now need replacing; also the singe glazing causes really bad condensation in winter.

 

[Doug71]

The weight of the gas dictates the best size of the cavity in double glazing, as Robin says if the cavity is too big you get the convection current effect.

According to the charts from my supplier (using planitherm total glass) the optimum cavity for air is 16mm or 18mm, the U value actually increases once you get a 20mm cavity.

Using Argon the U value doesn't improve once you get above a 14mm cavity.

It doesn't list Krypton but I believe you need a thinner cavity for that as it's heavier.

 

[Doug71]

Talking air circulating by convection I have 17 Heritage style rooflights in my house and almost every dg pane has blown in them.

I think the problem is that the sash part is metal and there is no thermal break in it, you can feel it gets really cold. There are two rooflights over my bed, at first I thought there was a draught coming through them but have realised it is just the heavier cold air (caused by the cold metal) falling on to me which feels like a draught.

Don't know why anyone would want single glazing these days, I remember ice on the inside of my bedroom window when I was a kid

 

[Jacob]

.....

Don't know why anyone would want single glazing these days, I remember ice on the inside of my bedroom window when I was a kid

You've said it yourself - 17 blown DG panes. It's common. Everybody thinks they are just an isolated unlucky incident but it is widespread, DG is not cost effective.

 

[Doug71]

You've said it yourself - 17 blown DG panes. It's common. Everybody thinks they are just an isolated unlucky incident but it is widespread, DG is not cost effective.

Actually closer to 34 blown panes as there are two in each rooflight

I would say the problem is the bad design of the rooflights, I made all the windows and doors for my house which went in at the same time as the rooflights (about 15 years ago) and none of the units in those have failed yet.

 

[Jacob]

Actually closer to 34 blown panes as there are two in each rooflight

I would say the problem is the bad design of the rooflights, I made all the windows and doors for my house which went in at the same time as the rooflights (about 15 years ago) and none of the units in those have failed yet.

Have had Velux skylights in the past. They were good. Still occasionally got condensation and even ice in a very cold weather but very well designed to drain off condensation. "Heritage" version - paint the outside frame installation black?

 

[ian33a]

Talking air circulating by convection I have 17 Heritage style rooflights in my house and almost every dg pane has blown in them.

I think the problem is that the sash part is metal and there is no thermal break in it, you can feel it gets really cold. There are two rooflights over my bed, at first I thought there was a draught coming through them but have realised it is just the heavier cold air (caused by the cold metal) falling on to me which feels like a draught.

Don't know why anyone would want single glazing these days, I remember ice on the inside of my bedroom window when I was a kid

if these panes are angled toward direct sunlight they will suffer more thermal and uv stress than units which face away. Repeated heating and cooling of the units causes a breakdown in the primary and secondary seals around the unit edges and once there is a hole, even a small one, the two panes in the DGU act like a bellows, drawing moist air in during the winter months and causing misting and dry air in during the summer months often causing the units to appear to have fixed themselves. But they haven’t.

as a rule of thumb, units facing toward direct sunlight, on average, will fail within 12 years. Units which never see sunlight can last a lot longer. I’ve seen units which are approaching 40 years of age. all of this assumes that the units were correctly installed in the first place. Before I retired we changed, on average, about 1500 failed glazing units per year. Even so, I still would not have single glazing in my house!

 

[mikej460]

You've said it yourself - 17 blown DG panes. It's common. Everybody thinks they are just an isolated unlucky incident but it is widespread, DG is not cost effective.

I'm thinking no science or clear advantages of DG will ever convince you Jacob, but we had all the rotten SG windows replaced with uPVC DG units in our house in 2008. The front is south facing with 6 windows, a lot of the other windows facing east so also get the heat of the sun for a large part of the day. Before we did this our oil bill was scary and yet the house was only just bearable in winter. Since then not one pane has failed and our heating bill has reduced substantially; the whole house is comfortable and quieter. My only regret is not replacing them with wooden frames as uPVC was considerably cheaper at the time when we had other costly projects to do, but despite having cottage style panes it just doesn't look right to me. My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers.

 

[Phil Pascoe]

My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers ...

It doesn't actually. If you speak to estate agents they'll tell D/G adds nothing because people expect it, but single glazing on the other hand does devalue it.

 

[johnnyb]

that's a bit false as the most attractive (and expensive) houses nearly always have single glazing. I work at a beautiful huge victorian house and every single window( 40 or more) is now plastic. the devaluation must be enormous. just imagine the cost to reinstate the sash windows as the boxes will have been decorated over.

 

[johnnyb]

what I will say is upvc windows in modern house have little variety maybe a colour comes in and another fades.white seems universal though.
but the frames and the details are the same. I had an "architect" do me drawings and I wanted a dwarf wall with stone cill with sliding sashes. he couldn't do it because his drawing package only had sliding sash with a panel below(??). the endless variety of wooden windows and the minds that designed them is now just a fantasy.
I'm neither pro nor anti dg but I fail to see why this is a matter of legislation when some one can go and buy a huge gas guzzler if they want and can afford to feed it.

 

[mikej460]

My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers ...

It doesn't actually. If you speak to estate agents they'll tell D/G adds nothing because people expect it, but single glazing on the other hand does devalue it.

That was my point, just unclearly stated...

 

[mikej460]

that's a bit false as the most attractive (and expensive) houses nearly always have single glazing. I work at a beautiful huge victorian house and every single window( 40 or more) is now plastic. the devaluation must be enormous. just imagine the cost to reinstate the sash windows as the boxes will have been decorated over.

I agree with you but it does depend on what a prospective buyer really values, some people think uPVC is attractive or at least more functional, less maintenance etc.

 

[mikej460]

I've noticed that painting uPVC is possible now and diy sheds are now selling uPVC paint. Just out of interest has anyone tried it?

 

[johnnyb]

I'm a member of a Facebook group called spraying makes sense. most of those make there living spraying upvc. the best paint is seemingly 2k. zinnser make a single pack all surface paint that's OK.the biggest job is removing the silicone.

 

[mikej460]

I'm a member of a Facebook group called spraying makes sense. most of those make there living spraying upvc. the best paint is seemingly 2k. zinnser make a single pack all surface paint that's OK.the biggest job is removing the silicone.

So roughly how much does it cost to have say a 4ft x 3ft double opener spray painted?

 

[Jacob]

I spent a good deal of time doing nothing but repairing/restoring sash windows and other period joinery. However doubtful the client by the end of the job they were always really pleased. They add enormous value to a period property - even quite ordinary Victorian terraces.
Nothing more tedious than streets with house after house with all the class removed and crude plastic windows all around.

 

[Jacob]

My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers ...

It doesn't actually. If you speak to estate agents they'll tell D/G adds nothing because people expect it, but single glazing on the other hand does devalue it.

A lot of buyers are looking for period quality. It's increasingly valuable. You don't know what you've got til it's gone

 

[Jacob]

..... My only other point that no-one else has raised is the value it adds to your house, single glazing only devalues your house and makes it less attractive to buyers.

To some buyers maybe but certainly not all. Especially if you are looking at 15 year old plastic or dismal brown DG hardwood past its best.

 

[mikej460]

To some buyers maybe but certainly not all. Especially if you are looking at 15 year old plastic or dismal brown DG hardwood past its best.

I agree as the old conservatory on our house was one such dismal brown monstrosity and to add to its horror a polycarbonate roof. It was the first thing we changed after we bought it...yet I still got £100 for it on eBay!