What to expect from this page.
1 – High level overview “in a nutshell” what window isolation means and how it can benefit your home.
2 – Explanations about important information when improving windows.
3 – How much can you save
4 – Future ambition – A custom calculator that can be used to calculate the businesscase for window isolation.
In a Nutshell:
Windows are listed in categories identifying the way how glass is build-up. Classifying the different layers of glass and the actual glass used. Naming like HR, HR+++ or vacuum glass are newly listed. The glass isolation value is presented as heat loss (Ug) value (in contrary to Roof/Wall Isolation where the value represents Heat resistance).
Complexity to resolve between 4/5 (just glass).
Money saving possibilities – up to 4/5
With single and double glazing, it is often interesting to review the possibilities to renew. For anything below a U value of 2 (see types of glass below) it is unlikely to make a solid businesscase.
While the glass usually is the key driver for window isolation, the frame can be of great importance too. It will determine the (im)possibilities for new window placement. Also in some situations glass cannot be replaced because of historic reasons. However, options to place “in front” or behind windows (basically placing 2 layers of glass) can be allowed.
Steps to take when you want to replace the windows & Glass:
The first step is to see what type of glass you currently have. This can be written on the inside of a window if the window is modern. (If there is no inside of the window and you suspect this to be old, then you can safely assume this is single glazing).
Types of Glazing:
| Glazing Type | Description | Typical U-Value (W/m².K) |
|---|---|---|
| Single Glazing | A single pane of clear glass. No insulating cavity. | 5.0-6.0 |
| Double Glazing | Two panes separated by an air gap (often ~12-16 mm). Basic insulation via trapped air. | 2.8-3.5 |
| Gas-filled Double | Like standard double glazing, but with argon or krypton in the cavity for better resistance to conduction. | 1.8-2.6 |
| Low-E Double (HR++) | Double glazing with a low-emissivity (“Low-E”) coating on one pane plus argon fill. The coating reflects long-wave (infrared) heat back inside. | 1.1-1.4 |
| High-Performance Double (HR+++) | An enhanced Low-E double glazing with thicker spacers, better edge seals, often krypton fill, and/or multiple coatings for maximal insulation. | 0.7-1.1 |
| Triple Glazing | Three panes, usually with two insulating cavities (argon or krypton). Often combined with Low-E coatings on one or more surfaces. | 0.6-1.2 |
| Vacuum Glazing | Two very thin glass panes separated by a vacuum gap (<0.2 mm). Eliminates convective and conductive losses across the gap. | 0.5-0.8 |