I have known for years that decks can become very hot during the summer heat. Nothing shocking here! Which during our cold winters, we all long for summer warmth. But during the heat of summer, it can become too much. Now asking, how can I cool my deck down?
There are four ways to cool your deck during the heat of summer. Shade, Water, Air Movement and Decking Paint each having its own advantage in addressing one of the three means of heat transfer. Shade is best for Raditian heat, Water and Air movement for Conduction heat and Decking Paint for Convection heat.
Let’s think through these possibilities of cooling down your deck, together discovering which will be most effective in cooling your deck, increasing enjoyment. Determining how your deck is becoming too hot will help decide which solution will work best.
Cooling your deck from the sun’s heat.
Now this one is obvious; shade is cooler. Getting all scientific here, Shade is best to shelter your deck from Radiant heat. The heat energy from the sun’s rays radiant onto your deck.
A shaded deck will be a cooler deck, but I was surprised when I read
“The sun is king. It makes deck temperature 34° to 76 ° [7-15° C] hotter than ambient air. When passing clouds hide the sun for several minutes, deck temperatures drop 6° to 8° [1-2°C] on most decking, and as much as 24°[5°C] on one deck board. And a corollary to the sun’s supremacy is the time of day. The shallow angle of sunlight at 4 pm lowers temps over 20°[4°C] from 1 pm highs”Jim Finlay founder and owner of Archadeck of Suburban Boston
That passing cloud, hiding the sun, lowering the heat a few degrees. Transforming your deck from unbearable to comforting. That’s what we are doing shading our decks, bringing the effect of the cloud in the sky to your deck. By blocking the sun cooling your deck.
You can block the sun in one of two ways, either overhead or from the side. Overhead shade can be created by a
- Patio Umbrella
Overhead shading helps to lower the actual temperature of
the air, by a few degrees.
The decks atmosphere directly affect by how much you block the sun. Awnings and Umbrellas are great for this — the awning canopy extending out providing tempory shelter from the sun’s heat as required. A Pergola is a more permanent shelter but only partial shelter you from the sun’s rays. Partially blocking the sun, removing the extremes but reaming year around.
Adjustability is one the advantages of an awning is you can retract it when you wish to enjoy a few more of the sun’s rays. But on those hot days extending it out providing relief from its heat. A Pergola is a much more classic and permeant shade for your deck. Unfortunately, with little adjustability. Whatever the number of purlins blocking the sun’s heat in July will be cooling also in October. The sun’s angle may change a little between the summer heat and October but marginally in its effect on the purlins blocking the sun.
Another thing to keep in mind is the sun’s angle. With the sun shining at an angle often, a good deal of your decking will still be hot as the sun sneaks under the awning or pergola heating up the decking. Often they will only shade half the deck as the sun creeps under the rafters.
A well placed vertical shade structure either in combination or alone will help to screen the sun. Either on the deck its self, like Screens or Lattice walls. Or keeping the deck open with shade trees casting their shadows over the deck from your yard.
Screens can be retractable, rolled out in the heat of the day and then retracted as the evening cools, providing a fuller view. Vertical shading structures need to be permeable, allowing air movement on the deck. Otherwise, the gain in shading will be lost by trapping hot air on your deck. This is why I recommend Screens or lattice walls and not solid panels preventing air movement. Screens being porous allow enough air movement to cool your deck but still screen you from the heat of the sun. Lattice working similar to a pergola creates partial shade while allowing air movement along with a partial view through its many holes.
A deck with a pergola shielding you from the overhead sun’s rays, shade can also be increased by hanging plants from the rafter. Either vining up a lattice wall unto the purlins increasing shade in the summer both above and the side. Or by hanging flowering pots from the rafters along the edge of the deck, shading the deck, while increasing its beauty.
Another thing to keep in mind is when will you most need shade on your deck. If its the middle of the day, you will want the vertical shade on the south side of the deck, screening your deck from the mid-day sun. If it’s later afternoon, early evening blocking some of the sun’s glare. The wall needing to be placed on the west side between the sun and your deck.
Shade takes the edge off the burning sun, but sometimes a greater cooling effect is needed to reduce the actual temperature of the air. Water is natures natural air conditioning.
Using Water in Cooling Your Deck
Back to science, water is of useful in cooling Conduction heat. The heat, energy that is in the air making your deck unbearable hot. Water helps to lower the temperature of the air by increasing the amount of energy required to warm the air. Wow, that’s complex but for us, all we need to know is adding water to the air will have a cooling effect on our deck.
There are two ways to increase water in the air, misting or plants. A simple misting system set up on your deck will lower the air temperature. You don’t want water spraying all over you or your deck but just small misting cooling the air.
A waterfall feature on your deck can have the same effect but with the added tranquillity of the sound of running water. But the waterfall by splashing will add moisture to the air, having a cooling effect.
Humidity is a double-edged sword. Adding humidity will decrease the temperature of the air but will decrease the ability of your body to cool itself as your sweat will not evaporate as quickly. You want enough moisture to take the edge of the heat but not so much that it feels like a rain forest on your deck. Play around with the amount of water. It is often better to err on the side of not enough water than too much.
A natural way to add moisture is with plants. Who naturally, through Photosynthesis, transfer water from the ground and release it into the air. With the advantage being that the water is not being sprayed, but slowing being released by the plants as required. Unfortunately, you have no control over the rate of release. Sorry, the plants are looking out for themselves, not you, but as a by-product, they will cool down your deck.
Cooling Your Deck from the Heat with Water
Either naturally or mechanically. For starter design, your deck with open sides allowing the breeze to cool your deck. Walls providing shade should be permeable to allow air movement.
If nature is not doing enough, adding fans can be helpful. Setting up fans near the edge of the deck blowing cooler air from off the lawn. Remember plants naturally cool the air.
Another option is a ceiling fan attached to the pergola’s rafter to move the air around on the deck. Moving air is cool air. In the winter, we call this wind chill but in summer, we call this relief.
A word of caution always check that the ceiling fan is safe for exterior use. You may only be using it on sunny days but it will still be out there on rainy days. The motor’s housing needs to be sealed and all electrical connections. If you don’t know how to do this, hire an electrician.
Deck Paint that Cools Wood Decking
On a sunny day, the hottest part of your deck is going to be the decking. Stepping on the decking in the summer heat will send you into the most entertaining dance, your feet burning from the heat. I cannot explain the science but decking especially wood, has a fast heat transfer rate. The decking’s actual temperature may not be that hot but the speed in which it transfers to your feet is.
I am just learning about these products for decking to reduce heat transfer, but I feel they need to be mention. Dura Deck makes a product called Deck & Dock with Cool Feel™ Technology (5400) designed to reduce the surface temperature of wood decking. COOL-TEC™ another painting option is designed to reflect the suns heat reducing the decking temperature
I need to learn more about the use and application of deck painting to reduce decking heat but it looks promising. It would be a great way to reduce Convection decking heat without additional structures on the deck. That being said, this is limited to wood decking which is rapidly being replaced with composite decking which is an entirely different material that should not be painted.
Selecting Decking Material That is Cooler
Again I have learned much from Jim Finlay about material selection affecting the temperature of your decking. You may want to read his more complete study, here is the link. Here is a quick summary.
- Wood decking is cooler than synthetic (composite)
- Lighter colours of both wood and composite are cooler than darker colours
- Cap stock composite is cooler than all PVC decking
- The density of decking does not correlate with the warmth of decking. This one is a puzzle but patio brick are cooler then pressure-treated wood but PVC is hotter than wood decking.
If you are in the building stage of your deck and you know it’s a hot part of your yard, some research could be of value. A simple selection of decking may make all the difference in the level of enjoyment of your deck on those beautiful hot summer days.
In summary, I hope these ideas help you to enjoy your deck more. Decks are for enjoying the summer, but staying cool may be required as decks naturally are hotter. Get out there, enjoy the sun.