The Impact of the Sun on Your Window Selection

By on 19th February in Home Inspiration

You may not know, but just picking the most thermally efficient window doesn’t mean you are maximising your home’s energy efficiency potential. Having the right windows for the right place in your home can ensure you get the most benefit from your double or triple glazing.

Anglian Home Improvements have just launched their most thermally efficient window ever, but they believe you should pair this up in your home with their A or A+ rated double glazed casement windows.

Before we dive in the technical part, it’s good to understand what Window Energy Ratings are. In short, they’re a rating given to measure the amount of energy gained through the glass, the amount of heat escaping through the glass and the air tightness, which gives an overall rating.

This rating is acquired in test conditions with a fixed orientation. This isn’t the case in real life as our windows will have a different orientation and are subject to different amounts of sunlight.


Windows on the North sides of your home won’t be bathed in as much sunlight as those on the south side. It is this simple reason that Anglian believe you should pair A++ triple glazed windows with A or A+ double glazing.

A++ triple glazed windows are ideal for the North facing side of your home, as triple will retain more precious heat that’s already in your home.

Kitchen window with blinds

A+ double however works very well at retaining heat, but has much better heat gaining abilities. The 2 Low E glass panes allow more of the Sun’s heat to pass through it, trapping it within your home thanks to it’s reflective microscopic layer of precious metals.

The more free heat you gain from the Sun, the less your heating has to be on and the more money you will save.

How to Work Out Sun Orientation (North, East, South, West)

The obvious route would be a compass, but I can’t imagine everyone having one of these at home. If you have a smart phone, there are free apps you can download, which will show you.

If you’re in the UK, a simple way would be to go outside on a clear day at 12pm. As the Sun rises in the east and sets in the west (a great way to find out the Sun’s orientation in conjunction to your home), due to our location in the northern hemisphere, if you face in the direction of the Sun, you are facing south.

Alternatively, you can see where the Sun will rise and set with SunCalc an online tool which uses Google maps – you can see exactly which windows in your home will be saturated in light and those that won’t.

How Where You Live Effects Your Window Decision

This is possibly a little more obvious – the more North you are in the UK, the slightly less sunlight and warmth your home will get. Due to the Earth’s curvature, sunlight has a larger area of atmosphere to pass through, reducing the amount of sunlight hours and therefore warmth. This is known as Latitude.

With this in mind, you may want to consider which windows you go for – if you’re on the South Coast where temperatures, on average, are warmer than those in Manchester, you may want to consider just having A++ triple glazed windows installed as they will bring and keep in more than enough warmth.

Whereas in Manchester, you may want to consider a mix to get maximum warmth into your home. On the south facing side of your home have A+ double glazing and triple glazing on the northern side of your home to make sure the warmth coming in, doesn’t go anywhere!

Know Your Rooms

Now, although the above is true, we don’t know if each room in your house has a tendency to be too cold or too hot. For example, if you had a south facing window in your living room and it was always too hot in the summer, we wouldn’t recommend fitting A+ double glazing – it will only make the room hotter and less comfortable to be in.


The final thing that may change your mind on which type of window you choose is shading from trees or neighbouring buildings. If these are going to prevent the Sun’s warmth getting into your home, stick with A++ to keep any heat you generate within the 4 walls of your home.

The matrix below should help you decipher which window is best for your room based on how easy or hard it is to heat.

I Need New Windows and My Room is…
Comfortable all year round Prone to
overheating in summer
Hard to heat in
winter &/or it has a cold spot next to the window
Hard to heat in
winter &/or has cold spots and is prone to overheating
The room
receives lots of sunlight & is south facing
Our A rated windows will provide a great all
round performance
Our A rated windows will provide great all round

Consider how
ventilation options may help make things more comfortable in the warmest

A+ will maximise the energy your window harvests
from the Sun to help heat your room.
Our A++ product can limit the impact of the
warmest & coldest weather to create a more stable, ambient

how ventilation options may help make things more comfortable in the warmest

The room receives an average amount of sunlight
The room receives little sunlight We
recommend A++ to benefit from our lowest possible U value.


So, if you’re ever told that triple glazing throughout your whole house is the best option, mention this little bit of science and make sure you get the most out of your windows.