When it comes to window shutters to keep the heat out there are a couple of things that will make a difference.
Firstly the material the shutters are made from will have an impact on on keeping the heat out in the summer and retaining the heat in the winter.
There are generally 4 different materials your shutters can be made from Wood, MDF (wood composite) , Faux Wood (PVC) and Vinyl.
All will be pretty good at keeping the heat out as they are built into frames and have very little gaps for the heat to come through.
There is one material that better when it comes to window shutters to keep the heat out and that is Vinyl Shutters.
Vinyl shutters are the only ones that have a hollow slat, all of the others have solid slats, and the big advantage with having a hollow slat is that it works like your double glazing trapping a layer of air inside the slat.
This increases the insulation properties of your shutters, so works very well in the summer and also in the winter, and will have an impact on both your heating and cooling bills.
If your home has a real issue with over heating then there is an even better option that will make a huge difference when compared to most window shutters.
By far the best option when it comes window shutters that keep the heat out is combining your shutter with the best insulating blind on the market.
The Shutter / shade option has a special frame so from inside your room it will look like a traditional shutter with the blind hidden inside the frame behind the shutter slats..
The blind is a honeycomb blind that is by far the best blind available for keeping your rooms cooler in the summer and stopping the heat escaping in the winter.
So with this combination your are combining the 2 best window coverings at keeping the heat out.
Another added bonus of the shutter / shade combination is for shutters in your bedroom. A standard window shutter is pretty good at blocking the light out, but the shutter / shade allows far less light in the than a shutter alone.
Compare the photo above which has the shutter completely closed but light still comes through.
This picture has the shutter slats completely open with the blind part way down to show how effective it is.
I hope the information helps.