The Home Envelope | Insulation, Air Sealing and More
Sep 27, 2026 · 25 min · 9 segments
Your house is still drafty after new windows, and the glass is rarely to blame. Here's where the cold air is really getting in.Learn why the chill across your ankles is often a fake draft off cold…
The first thing we need to understand is the physics of why those expensive new windows are getting a bad rap in the first place.
Well, to do that, we have to isolate how heat actually moves because there is a fundamental difference in physics between conductive heat loss and convective heat loss.
They are two entirely different thermodynamic mechanisms.
And, you know, homeowners mix them up constantly.
I mean, I definitely do.
I always see like R-value plastered on window stickers and insulation at the hardware store.
Does that tie into one of those mechanisms?
Yes, exactly.
Conductive heat loss is it's thermal energy transferring directly through a solid material.
OK, so the glass itself.
Right.
So when you see a high R value on a product, it simply means that material has a high resistance to conductive heat transfer.
So when you buy a modern triple pane window filled with argon gas, you're buying a product that is heavily engineered to stop conduction.
Oh, I see.
The multiple layers of glass and that dense gas in between them, they physically resist the heat from your living room, transferring outward through the solid pane.
Okay, so the window is actually doing its job perfectly then.
It's just a shield against conduction.
It is.
It's doing exactly what you paid for.
Convective heat loss, on the other hand, is the physical mass movement of air.
Like actual wind?
Yes, the air itself carrying heat away through gaps, cracks, and structural interfaces.
And what's fascinating here is that the draft you feel sitting next to your brand new window often isn't an exterior leak at all.
Wait, really?
Yeah, it is an entirely internal phenomenon.
The first thing we need to understand is the physics of why those expensive new windows are getting a bad rap in the first place.
Well, to do that, we have to isolate how heat actually moves because there is a fundamental difference in physics between conductive heat loss and convective heat loss.
They are two entirely different thermodynamic mechanisms.
And, you know, homeowners mix them up constantly.
I mean, I definitely do.
I always see like R-value plastered on window stickers and insulation at the hardware store.
Does that tie into one of those mechanisms?
Yes, exactly.
Conductive heat loss is it's thermal energy transferring directly through a solid material.
OK, so the glass itself.
Right.
So when you see a high R value on a product, it simply means that material has a high resistance to conductive heat transfer.
So when you buy a modern triple pane window filled with argon gas, you're buying a product that is heavily engineered to stop conduction.
Oh, I see.
The multiple layers of glass and that dense gas in between them, they physically resist the heat from your living room, transferring outward through the solid pane.
Okay, so the window is actually doing its job perfectly then.
It's just a shield against conduction.
It is.
It's doing exactly what you paid for.
Convective heat loss, on the other hand, is the physical mass movement of air.
Like actual wind?
Yes, the air itself carrying heat away through gaps, cracks, and structural interfaces.
And what's fascinating here is that the draft you feel sitting next to your brand new window often isn't an exterior leak at all.
Wait, really?
Yeah, it is an entirely internal phenomenon.
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