HR++ glass is currently one of the most popular types of insulating glass for homes. It insulates much better than single glazing and old double glazing, often fits in existing window frames and in many cases is eligible for a subsidy. The brief explanation is simple: HR++ glass consists of two glass plates with an insulating cavity in between, usually filled with noble gas. There is a special coating on the inside that reflects heat back into the home. This keeps your house warmer and you lose less energy through the windows.
In this article we explain what HR++ glass is exactly, when to choose it, what the difference is with double glazing, triple glazing and vacuum glass, and what you should pay attention to before ordering.
What is HR++ glass?
HR++ glass is high-efficiency glass with an extra good insulating effect. It consists of two glass plates with a space between them: the cavity. That cavity usually contains argon gas. That insulates better than normal air. In addition, HR++ glass has a thin, invisible coating that reflects heat.
This combination ensures that heat escapes less quickly in winter. This makes it feel more comfortable in the house, especially near windows where you normally feel cold.
HR++ glass is widely used for:
- replacement of single glazing
- replacement of old double glazing
- renovation of homes
- sustainability
- bedrooms, living rooms and kitchens
- existing wooden, plastic or aluminum frames
What does HR++ stand for?
HR stands for high efficiency. The plus signs indicate how well the glass insulates.
| Type of glass | Meaning |
|---|---|
| HR glass | Basic high-efficiency glass |
| HR+ glass | Better insulating than HR glass |
| HR++ glass | Very well insulating double glazing |
| HR+++ glass | Triple glass with three glass panes |
HR++ is therefore not a brand name, but a designation for insulating glass with a high insulation value.
How does HR++ glass work?
HR++ glass works in three ways:
- Two panes of glass — there are two layers of glass between the inside and outside. This creates an insulating space.
- Noble gas in the cavity — the space between the glass plates is often filled with argon gas. This gas conducts heat less well than normal air.
- Heat-reflecting coating — there is a special coating on one of the glass layers that largely allows sunlight to pass through, but reflects heat from the home back in.
The result is a window that insulates much better than single glazing or old double glazing.
HR++ glass compared to other glass types
What is the difference between HR++ glass and regular double glazing?
Ordinary double glazing consists of two panes of glass with air between them. HR++ glass also has two panes of glass, but the cavity is better insulated and the glass has a coating.
| Attribute | Old double glazing | HR++ glass |
|---|---|---|
| Number of glass plates | 2 | 2 |
| Cavity filling | Mostly air | Often argon gas |
| Coating | Usually no | Yes |
| Insulation | Moderate | Good |
| Comfort | Better than single glass | Much better |
| Energy loss | Relatively high | Lower |
| Subsidy possible | Usually not | Often yes |
Old double glazing used to be a big improvement over single glazing. But compared to HR++ glass, the insulating capacity is often much lower.
What is the difference between HR++ glass and triple glass?
Triple glazing consists of three glass plates and two cavities. This means it insulates better than HR++ glass, but it is also thicker, heavier and more expensive.
| Attribute | HR++ glass | Triple glass |
|---|---|---|
| Glass plates | 2 | 3 |
| Thickness | Often 24-28 mm | Often 36-42 mm |
| Weight | Lower | Higher |
| Insulation | Good | Very good |
| Fits in existing frame | Often yes | Often not |
| Price | Lower | Higher |
| Best Application | Renovation | New construction or new window frames |
For existing homes, HR++ glass is often the best balance between insulation, price and applicability. Are you in doubt? Then read when triple glazing is or is not worthwhile, or immediately assemble triple glazing if you install new window frames.
What is the difference between HR++ glass and vacuum glass?
Vacuum glass is thinner than HR++ glass and can still insulate very well. It does not work with a wide cavity filled with gas, but with a thin vacuum space.
| Attribute | HR++ glass | Vacuum glass |
|---|---|---|
| Thickness | Often 24-28 mm | Often 8-12 mm |
| Insulation | Good | Very good |
| Fits in narrow window frames | Sometimes difficult | Often yes |
| Price | Lower | Higher |
| Suitable for monuments | Sometimes | Often |
| Technical visibility | Hardly | Sometimes micro spacers |
Choose HR++ glass if you have enough space in your frame and are looking for good value for money. Choose vacuum glass if you have little space, for example with old or monumental window frames.
When do you choose HR++ glass?
HR++ glass is a good choice if you want to better insulate your home without immediately replacing all the window frames. You mainly choose HR++ glass for:
- replacement of single glazing
- leaky double glazing
- old houses with reasonable window frames
- sustainability and lower energy costs
- more living comfort, less draft and cold
- grant applications
- renovation projects
For many existing homes, HR++ glass is the most practical step towards better insulation.
When is HR++ glass less suitable?
It may be less suitable when:
- your rabbet is too shallow
- the frame is in poor condition
- the window is too weak for extra weight
- you want maximum insulation with new window frames
- you have a monumental frame with little space
- you want to fully preserve the old appearance
- triple glass or vacuum glass better suits your project
Vacuum glass can sometimes be smarter for narrow old frames. In completely new construction, triple glazing is often more interesting.
Does HR++ glass fit in my existing frame?
Often yes, but not always. HR++ glass is thicker than single glazing and many old double glazing. That's why you have to check whether the rebate is deep enough. NB:
- total glass thickness
- rebate depth
- space for glazing tape
- space for glazing beads
- kit room
- condition of the wood
- weight of the window
- hinges on rotating windows
Does HR++ glass just not fit? Then top slats or nose slats can sometimes help. This creates extra space without having to replace the entire frame. You can read more about this in will thicker glass fit in my existing frame?.
How thick is HR++ glass?
HR++ glass is often about 24 to 28 mm thick. The exact thickness depends on the structure. A glass structure, for example, consists of an outer pane, cavity and inner pane. Examples of construction are 4-15-5 or 5-15-4. In the insulating glass configurator you can put together the structure yourself and immediately see the corresponding thickness.
Therefore, do not only measure the width and height of the glass, but also always check whether the thickness fits in your frame.
How heavy is HR++ glass?
Glass weighs on average approximately 2.5 kilos per square meter per millimeter of glass thickness. When it comes to insulating glass, you mainly count the glass plates. A HR++ pane with two panes of glass made of 10 mm glass weighs approximately 10 × 2.5 = 25 kg per m². A large window can therefore become quite heavy.
This is usually not a problem for fixed windows. With rotating windows, doors or sliding windows you must pay extra attention to:
- hinges
- locks
- frame strength
- operation
- risk of subsidence
With old windows it may be necessary to strengthen fittings or use an extra hinge.
What is the U-value of HR++ glass?
The U-value indicates how much heat is lost through the glass. The lower, the better. HR++ glass usually has a U-value of approximately 1.0 to 1.2 W/m²K.
| Type of glass | Average insulation |
|---|---|
| Single glazing | Bad |
| Old double glazing | Moderate |
| HR++ glass | Good |
| Triple glass | Very good |
| Vacuum glass | Very good |
A lower U-value means less heat loss and more comfort. Do you want to calculate the U-value for your accrual? Then use the U-value calculator.
Is HR++ glass eligible for a subsidy?
In many cases yes. HR++ glass can be covered by the ISDE subsidy if it meets the conditions, such as the correct U-value, minimum surface area and professional installation. Important points to note:
- the glass must meet the insulation requirements
- you must replace sufficient square meters
- installation must be carried out professionally
- you need an invoice and proof of payment
- a reporting code is often required
- you usually only apply for a subsidy after implementation
Always check the current subsidy conditions before ordering. Subsidy amounts and rules may change. All details can be found in ISDE subsidy for insulating glass.
Moisture, condensation and ventilation
Does HR++ glass reduce condensation?
HR++ glass can reduce condensation on the inside. The inner glass plate remains warmer than with single glazing or old double glazing. This means that moisture is less likely to settle on the window.
But HR++ glass does not solve every moisture problem. Condensation on the inside can continue to occur due to:
- too high humidity
- too little ventilation
- cooking, showering and washing
- cold bridges
- poorly heated rooms
Condensation on the outside can actually occur more often with HR++ glass. That's usually a good sign: it means that the heat stays inside and the outer glass plate remains cold. Condensation between the glass plates is not normal — then the insulating glass is probably leaking. You can find more information in condensation on windows: inside, outside or between the glass.
Do you need ventilation grilles with HR++ glass?
Sometimes yes. If you replace old glass with HR++ glass, your home will be better sealed. That is good for insulation, but moisture must still be able to escape. Ventilation grilles help with:
- healthy air circulation
- fewer moisture problems
- less condensation on the inside
- better air quality
- constant supply of fresh air
A ventilation grille can be wise, especially in bedrooms, living rooms and kitchens. Are you having new HR++ glass installed? Then that is a good time to immediately determine whether you want to add ventilation grilles.
HR++ glass and safety
HR++ glass is insulating glass, not automatic safety glass. Standard HR++ glass insulates well, but is not necessarily injury-proof.
This is often forgotten. In high-risk areas you should therefore opt for HR++ glass with a safety structure. Consider:
- laminated HR++ glass on low windows
- safety glass next to doors
- laminated insulating glass in case of risk of falling through
- tempered glass where extra impact resistance is required
Use safety glass on windows that start low, glass in doors, sidelights and other places where someone could fall into. You can read the difference between the structures in tempered or laminated glass.
How do you measure HR++ glass?
For HR++ glass, measure the tight rebate size of the frame, just like with other glass. Always measure:
- width top, middle and bottom
- height left, middle and right
- the smallest size as a starting point
- rebate depth
- glass thickness that fits
- any space for a ventilation grille
With standard glass in a frame you often subtract 8 mm from width and height. With HR++ glass it is extra important to also check the thickness. A diamond can be perfect in terms of width and height, but still not fit if it is too thick. The complete step-by-step plan can be found in measure glass.
Common mistakes with HR++ glass
- Thinking that HR++ always fits — HR++ glass is thicker than single glass; always check the rebate depth.
- Do not consider weight — large HR++ panes can be heavy; check rotating windows and hinges.
- Do not regulate ventilation — better insulation without ventilation can cause moisture problems.
- Confuse HR++ with safety glass — HR++ is insulating glass; safety glass must be selected separately if necessary.
- Measure the old window — always measure the frame, not just the old window.
- Do not check subsidy conditions — do you want a subsidy? Then check the current rules in advance and have the glass professionally installed.
- Using the wrong sealant — use suitable glazing sealant for insulating glass; Incorrect sealant can affect the seal. See which kit do you use for what.
HR++ glass selection aid
| Situation | Is HR++ glass suitable? |
|---|---|
| Replace single glass | Yes, often very suitable |
| Replacing old double glazing | Yes |
| Existing frame with enough space | Yes |
| Narrow monumental frame | Sometimes, vacuum glass is often better |
| Installing new window frames | Possible, but also consider triple glazing |
| Maximum insulation desired | Consider triple or vacuum glass |
| Limited budget | HR++ often best choice |
| Low windows or doors | Only with safety glass structure |
| Poor ventilation in the house | Combine HR++ with ventilation |
Checklist before ordering HR++ glass
- What is the width and height of the rebate?
- Have you measured in multiple places?
- Have you applied the correct deduction?
- Is the rebate deep enough?
- Does the total glass thickness fit?
- Are the glazing beads suitable?
- Is the frame in good condition?
- Can the window support the weight?
- Is safety glass necessary?
- Do you want ventilation grilles?
- Do you want to apply for a subsidy?
- Is it professionally installed?
- Are you using the correct sealant and glazing tape?
Conclusion
HR++ glass is the best choice for many homes when replacing single glazing or old double glazing. It insulates well, increases living comfort and often fits into existing window frames. In many cases you can also receive a subsidy if the glass is professionally installed and meets the conditions.
Pay attention to the thickness, weight and condition of the frame. HR++ glass does not automatically fit into every old window. Also check whether safety glass is required and whether ventilation needs to be arranged.
Do you want to make your home more sustainable without immediately replacing all the window frames? Then HR++ glass is often the most practical and affordable step.
Want to know more or get started right away?