Can a plantation shutter, something with large gaps between louvers really add any R-value to your windows to make any difference?

Let’s get right to the answer and the answer of course is no. 

What exactly is R-Value?

R= resistance. It is the way to measure how much resistance something has to heat flow per inch of thickness. The higher the R-value, the more resistance and the better the material is at insulating. Attic insulation is typically desired in the R30 to R60 range.

A plantation shutter has louvers that you open or close for light control.  So how do you get R-value from something that is open letting light into your room and has space between the louvers?

Well, you don’t. 

What if I close the louvers of my plantation shutters?

So logically you think, what if I close the louvers of my plantation shutters is that how I get R-value from shutters that others keep saying they have?

Okay, so now you’re in a dark room, so maybe at night this wouldn’t be a bad thing, but here is the problem. A louver on a shutter panel is only about 3/8″ thick, which means you have to stack four of them on top of each other to get one inch of thickness. How much insulating R-value is there in something 3/8″ thick? Essentially, none.

But what about how they have told me that my new shutters could give me an R2 to R3 increase in R-value to my windows?

I would like to see the actual science to be frank about it. I think it’s wrong and based on something that people keep regurgitating over and over again in the shutter industry.

The value of plantation shutters helping with cold or heat actually has nothing to do with R-Values

There are a couple of ways that heat and cold affect your home through the windows. The first is conduction the second is convection and the third is radiation. 

Where most of the confusion comes from in the ability of plantation shutters to help with heat and cold transfer is the type of transfer, R-value is all about conduction.

It is the transfer of temperature from something cold to something warm as in the case of the cold outside your house trying to transfer to the warmth inside your house, when you place something in between this slows down and blocks the transfer, this is the infatuation with R-value and shutters.

Which we have discussed really adds nothing to the blocking of conduction transfer of heat or cold due to the thin nature of the product and it’s a product that you open and has space between the louvers blocking nothing.

Conduction through the window, cold outside transferring through the window

Heat transfer via convection is where plantation shutters actually help keep your house warmer

Convextion and radiation is the second and third combination that temperature transfers and is really how plantation shutters help.

Since hot air rises and cold air falls when there is a cold surface such as a window the air in front of it is being cooled via conduction from the cold surface and the air falls in front of it and then hits the warm air of the room and rises, creating a looping convection current of cold air mixing and cooling the warm air of the room.

Convextion heat loss

The plantation shutter panels break the convection cycle

The shutter panels act as a break and block the convection cycle from running down the cold window pane. This stops the continual mixing of colder air in front of the window with the rest of the room which in turn stops the air temperature in the room from cooling. The works best with the louvers closed, but there is still quite a bit of effectiveness with the louvers open.

So is it really R-value?

No, it’s not and this seems to be where all this confusion comes from. People can feel the difference and somehow this has gotten misconstrued as R-value since that is the most popular and most familiar label for measuring how something helps insulate.

How about heat gain in the summer is R-value responsible?

No, once again there is still so very little insulating properties of a 1/4″ thickness of louvers that R-value really plays no part. What is happening is the shutters, especially if they are white, are reflecting the solar radiation back outside.

So is there any R-value at all to shutters. Some, but it’s tiny and it’s not really why they help keep your house a little warmer or a little cooler. So now you know.

• Plantation Shutters, like blinds, are better at preventing heat from coming into the house than keeping heat inside during colder seasons.   
• Keeping them open during the day can also bring in heat and light, minimizing the need for air conditioners and artificial lights.