Why you can't use insulated glass on historic windows. 

I agree with the 15-20 year life span on insulated glass - I'm a contractor in upstate NY and have replaced dozens of windows that the seal has broken and the windows fog up on the inside and/ or the vinyl has warped and broken in windows that are less than 20 years old. I'm not impressed with them at all after seeing what sunlight (uv rays) do to vinyl. I just wished more people would realize it and opt to fix original windows versus just replacing them. Thanks for the videos Brent 🍻

Years ago we replaced single pane glass with double pane on some historic windows. It worked fine, the trick was to use super thin glass with krypton, which allows a 2-3mm gap (instead of 11mm), which results in a much thinner window, eg 5-6mm or a little less than 1/4" in SAE. But this was also in Europe where they make a specific insulated glass for historic windows.

I am impressed with the production of your videos. I can tell that you love what you do and love sharing your wealth of knowledge. I have gained so much knowledge between your videos and finish carpentry videos. I am a plumber by trade, but have always been interested in wood working and architecture. I live in buffalo, and there are some incredible houses and buildings here that I have had the pleasure of working in. After watching your videos I can actually pick some things out and appreciate them a little more now, knowing what used to go into crafting these mansions. Impressive stuff.

GREAT info. Storms and screens work very well. I have some on my 1927 house.

I retrofit vacuum glazing into all my 1917 original fir double-hungs. It was a lot of work, but the improvement in energy efficiency and comfort near the windows made it well worth it.

I love you preservation and common sense mindset when tackling modern day issues. New is not always better. I will keep my 107 yr old sash windows in tip top as long as I can. Appreciate your work.

Great video. Historic windows just can’t be beat. The authentic character they add to a home is priceless.

Brett, I found your channel last summer after we moved into our old Shotgun house. I was looking for instruction on restoring the windows. I was concerned that going into winter this old house would be impossible to heat with aaalll these windows. It turned out our finances didn't allow us to redo any windows. ...and even though we had below freezing temperatures quite a bit here in Deep East Texas, we heated this house quite well with our small, soapstone,wood heater! We were thrilled! Yes sir, it's still on my "To Do" list, for sure, but not as high a priority as I originally thought. I continue to love learning from you! Sooo many ideas and plans come from your instruction!

I love your videos and the love you feel for this very much shows. I mostly hear you give us dont’s, don’t insulate cavities, don’t insulate windows. You do say to insulate roof decks and basements. Have you considered a series where an historic house was significantly improved. I do agree though with the 100 year trade off. I live in an area where about half the buildings are 100yo. As a community we want both preservation and efficiency and don’t seem to be able to reconcile the two.

This does help. Thank you!

This is great information. Thank you. My 1931 house (unfortunately) has 1970s metal windows, most of which are double-pane. 90% of them leak, with moisture between the panes, and water getting in at the corners of the tracks. I hate them. Older homes (1920s-1950s) here in Southern California are often retrofitted with cheap, white vinyl windows that ruin the look. I will be researching current replacement windows with a historic look, so this was helpful. All of our window openings have bullnose plaster on the inside and bullnose stucco on the exterior. It's going to be a challenge. I restored all of the original windows in my prior 1931 Spanish house, but this is a different kind of problem.

It’s been a pet peeve of mine for some time that double paned windows were deceptively marketed for years as lasting just as long as regular windows. Customers did actually ask that question when the product first started becoming widely available. Windows were then a lifetime component of the house. Double-paned windows were so expensive that no one would have bought them except as a one time upgrade. The early windows had a reputation for failure but the manufacturers assured us that was fixed now. Fast forward several decades and everyone has double paned windows on both older homes and new builds. Now the window sellers come around and refer to your windows as replacement items and let you know it’s time for that “replacement” as though you were putting new tires on you car. Except these tires cost several thousand dollars for every one of the 20 or 30 windows on your house.

With our experience of windows on very old buildings, I agree that you have to make a decision. For most people, it is either authentic-looking windows (either original or new) that have a relatively low RV value or modern windows that will have a different aesthetic and where the double glazed units (as we call what you call insulated glass) has a finite life span. If we take a listed building (one regarded as having historic value and there are thousands here in the UK), the local planning authority should insist upon keeping the original aesthetic but I’ve experienced permissions which have allowed double glazed units to be used. I feel sorry for homeowners who are not experts in this field and are not made aware of the trade offs. The local planning authorities are rightly focussed upon raising insulation values in buildings and tell people to get better insulated roofs or lofts, windows, doors, floors etc. of course, if you ask any homeowners as to whether they would like to reduce their energy bill, then everyone will say yes. So, the builder/developer/window maker pushed double or even triple glazed windows. The inevitable breakdown of the unit is rarely mentioned and, if it were, I would guess that many will decide that they may not own that houses when the units need replacing. The bottom is line is trade-off. Old building=poor insulation= higher energy bill. New building=better insulation=lower energy bill but long term maintenance cost

Big fan of keeping the original sashes and just upgrading to laminated 1/4". When a large picture window broke, it was the safer choice, and really did cut down noise transmission by a noticeable amount. But when it comes to window insulation values, this 1901 built house still has great white shark size larger fish to fry. It'll never be perfect, but insulated windows would never pay off if it were.

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Sir: let’s make sure that the cameraman points well at your drawings , if possible . Thank you for sharing !

Repairing some sash in the following weeks on some 9/6 historic windows we are putting in the home we just bought.

Hi Brent. Thank you so much for the informative content. I do have a question about building windows and would love you thoughts. I'm building a more modern window with tilt and turn hardware. The sash and frames are stave core with a doug fir interior and sapele exterior - 3" thick. I'm using 3-pane IGUs with warm edge spacers. All that is simple enough. My question is, would it be crazy to try to incorporate true divided lites into the design. These are a modern style window, so I'm ok with the square edge muntins being thicker and wider than a what would be common in a historic window. My main question is how to size the muntins to support the added weight of a 3-pane IGU. Say in a 4-lite sash, Would some of the weight of an upper lite be carried by the lite below it?

Brent, have you ever heard of new, “production” windows being made with single-pane glass? For those of us that can’t afford the awesome 100-year windows but also don’t want to deal with replacing glass every 15-20 years, it seems like that would be the best option.

What do you think about interior storm windows? I've considered exterior ones but it alters the look of the house and since they often open from the bottom, they'd impede airflow out the top of a double-hung window ... so you'd have to remove them in summer, which is kind of a pain on the 2nd floor of a house. Great video by the way ... I could never put double-pane windows on my house knowing those seals fail in 10-20 years. At least with a storm you get the air gap while being able to replace each pane. No manufactured, unserviceable seal.

Just thinking, what about using insulated glass and increasing the thickness of the sash?

Can you use non-insulated glass in coastal areas? I’m not sure if they make hurricane rated windows that aren’t insulated. I won’t forget when you said that non-insulated glass is a 1000 year product.

The key comes at 0:35 .... insulated glass "that we would get in America". The US has some of the best and brightest minds as well as world class craftsmen. There is no reason we shouldn't have cutting edge material

I don’t think my 2nd floor windows are accessible by ladder, which explains why they have old permanent (but failing) aluminum storm windows screwed onto them.

I wonder how many laymen like me were unaware of this issue. My guess ---- pretty much everyone.

"insulated glass" no, it's Double Glazing, it is in no way insulated haha

sounds very much like a unjustified bias