Green construction means more than just putting insulation in your loft. It means safeguarding the house against losing energy. Your aim is to reduce the amount of energy lost by as much as possible so that the house is as efficient as possible. Imagine a fridge that let cold air out of the bottom, or a diesel tank with a hole in. This article offers brief explanations of thermal conductivity R-Values, K-Values and U-Values, so that you may better judge the types of insulation you use when you make your house more energy efficient whether you are building a new home or upgrading an existing building.
What is a K Value?
The K-Value of a material is its thermal conductivity. If it has a low K Value, then that means it has low thermal conductivity. This means it takes longer for cold air on one side to reach hot air on the other, and visa-versa.
Lower K values means better insulators because it takes longer for heat to transfer from inside to outside your house. On the other hand, if you had a frying pan, you would want a higher K Value because you want the heat to transfer from the burner to your food in the pan quickly.
What is the U Value?
R-Value measures the thermal transmittance of materials as the rate of transfer of heat through matter. In other words, how long it takes for heat to get all the way through the insulation. A lower U Value means it takes longer for heat to get through. Ergo, a lower U Value is better.
On the other hand, if you had a frying pan, you would want a fairly high U Value because you do not want to be waiting all day for your frying pan to heat. However, you wouldn’t want a super high U Value because if the heat goes through the pan too quickly, then it would be like cooking your food on an open flame.
What is the R Value?
R-Value measures the thermal resistance of insulation against the conductive flow of heat. This means a higher R Value is better.
Let’s take two pieces of insulation. One is made of PIR foam and another of compressed feathers. Both pieces of insulation have the same R value, but the compressed feathers insulation is 2-feet thick, whereas the PIR foam is one inch thick. If both panels were the same thickness, the PIR foam panel would have the higher R Value.
With a frying pan, you want to transfer heat, so you want a lower thermal resistance. You would want your frying pan to have a lower R Value because you want the heat to transfer from your burner to the food in your pan.
More About The U Value of Your Walls
When referring to building insulation, the U Value of your walls/ceilings takes into account the sum of all the thermal resistances that make up a layer. If the U Value is lower, then the insulation is better.
Let’s say you have a brick wall, then a tiny gap, then insulation, then a plaster wall on the interior. The U Value is supposed to take all layers into account, including the layer of air in the gap between the layers.
Double walls are becoming popular because they avoid common problems with home insulation. They allow for things like air sealing, which helps lower U Values.
Where Does the U Value Become a Headache?
The U Value becomes frustrating when insulators do a bad job. A good insulation company will apply a good quality insulation, and they will do it correctly. When they do not do it correctly, then there is a problem.
For example, there was a company that applied expensive insulation in lofts but didn’t separately insulate the roof beams that went all the way outside. In the winter, the roof beams transmitted the cold into the house, which appeared as patches of moisture on the ceiling. Being winter, condensation from the heated house accumulated, and after a while there were patches of black mold on the ceiling.
In reality, whatever U Value the builders claimed was false due to the way the insulation was installed, and there were probably several building standards/regulations that were broken too.
Final Summary
Let’s say you have a panel of thermal insulation in your hands that you intend to put into your wall. You want it to have a low K Value, a low U value, and a high R Value.
A low K Value so that heat has a harder time getting through it. A Low U value so that heat takes longer to get through it, and a high R Value so that the insulation doesn’t have to be super thick to do its job.
