Do orangeries get too hot in the summer?

A question that we hear all the time, do Orangeries and conservatories get too hot during the summer months? The simple answer is, not always. But not all orangeries and conservatories are made equal.

Orangeries can be incredibly warm and welcoming spaces over the winter, and still feel comfortably cool during the summer months. But there are several crucial factors to enabling their year-round comfort.

Many people worry that orangeries and conservatories may feel too hot during the summer. This concern stems from the poor reputation of old-fashioned glazed extensions that would be unusable for 6 months of the year. But over the last 30 years we’ve seen great advancements in glazing technology, access to superior materials, and clever design features have enabled glazed extensions to maintain a consistent temperature all year round.

Some of the ways orangeries and conservatories stay cool over the summer


It goes without saying, if you want to keep as much of the warm air outside your home as possible, you will need insulation. Orangeries in particular feature brick built, insulated walls and a flat roof, all of which help to reduce warm air from entering your home. In addition, high performing weather seals should be used across all doors and windows to prevent the air from outside entering your home.

Thermally efficient windows and doors

With a large portion of an orangery or conservatory being glazed, it’s important to also minimise the heat transference through the glazed panes when temperatures begin to soar. That’s where an understanding of U-values comes in. U-values are calculated by finding the sum of thermal resistance, the lower the U-value the better your glass will perform throughout the year as the glass allows a low amount of heat transference. The same principles can also be applied during the winter, with less cold air being transferred into your home.

How important are U-values for glass to ensure your orangeries or conservatories are not too hot in the summer?

The first thing to note is that not all glazing is tested the same for its thermal performance. Each and every door or window from our orangeries or conservatories are independently tested for their U-value in their entirety. To give the most accurate performance results possible for the whole product. Glazing and frame combined.

Comparatively some companies prefer to only test the centre pane. Which, we believe, can produce misleading results. This is down to how glass transfers heat. The centre of the pane is the most thermally efficient area of the entire glazed unit. Gradually decreasing around the edges where all glass will experience some loss/gain, until you reach the surrounding framework where there will likely be heat loss/gain. If the U-value of a window is only tested on the centre or the glass pane, your windows and doors could experience a great deal more heat gain than you may have expected over the summer.

Once you understand these different methods of measuring the U-values, they can provide a useful tool into judging how well your dream orangery or conservatory will fair over the summer months. Under current regulations*, new buildings require a maximum U-value of 1.4. However, when tested by an independent body, our U-values went as low as 1.1 for our triple glazing. Ensuring every orangery or conservatory will stay cool and comfortable over the summer.

*Time of writing 02/08/22

Thermally efficient roof lanterns and glazed rooves

Lanterns are brilliant to not only bring in a great deal of natural light, but they are also thermally efficient. We use toughened, argon filled, 4-16-4 units with warm edge spacer bars as standard. What does all that mean exactly? It means that each toughened pane experiences minimal heat gain throughout the summer. We also recommend the use of our Westbury Sunguard on our roof lanterns.

It is a very neutral glass, allowing in a very high level of natural light whilst also reflecting 65% of the solar heat away, which helps to prevent over heating. It can also also be used on our windows and doors, particularly those belonging to South-facing rooms that experience longer durations of direct sunlight.

In winter Westbury Sunguard will also help keep your home warm as it reflects the heat back into the room helping to keep down energy bills.

Automatic thermostatic roof ventilation

An option we also offer is the addition of automatic thermostatic roof vents, fitted into the roof lantern. They are highly effective at encouraging cross ventilation in the room by drawing the warmer air up and out, without having to open any doors and windows. These vents can be operated remotely with thermostatic and rain controls that allow the ventilators to close up in the event of an unexpected shower while nobody is at home.