More and more homeowners have turned their attention to saunas. So, if you're planning to purchase or have recently bought an outdoor sauna, you might need to do a bit of research when it comes to insulation.
Do you need a drain, or will you install additional insulation? How much electricity is needed? You must understand when you require insulation and when you do not and how to install it. This guide will look at everything you need to know about your small outdoor sauna and whether or not it needs insulation.
The Science Behind Outdoor Sauna insulation
As per the second law of thermodynamics, heat usually flows naturally from a higher-temperature region or object to a lower-temperature area or object. When it comes to saunas, if the heat in your small outdoor sauna can escape to a cooler region, it will. Insulation helps prevent heat from escaping your small outdoor sauna.
Moreover, if the warm air comes up against cooler walls, condensation occurs, which could damage the stunning wood of your sauna. Even if you reside in warm climate regions, the outdoor temperature is not likely as warm as your outdoor sauna's interior.
For instance, if you set your sauna even in a low-temperature range of 110-120 degrees Fahrenheit, it's not feasible that your setting will be that warm throughout. Most sauna users fancy sauna temperatures of around 150 degrees Fahrenheit or higher; condensation and heat escape is unavoidable without proper insulation. So, insulation offers resistance to heat flow.
Benefits of Using Sauna Insulation
Authentic Sauna Feel
Your small outdoor sauna feels more solid with a vapor barrier with the correct insulation and sealing. It provides a more realistic experience as stated by many traditional outdoor sauna fans.
Moisture Will Not Leak
Insulation helps keep your small outdoor sauna from tracking moisture and prevents corrosion which can damage the interior wood. Keeping your sauna dry also helps prevent mildew, mold, and rust that accumulate when your sauna isn't insulated correctly.
Moreover, preventing moisture leaks helps keep the heat inside as well. Therefore, the more insulated your sauna is, the less energy it will require to heat up or cool down if using an electric model.
Holds Heat Inside
Insulation helps hold the heat inside your small outdoor sauna. Insulation can be made using various materials such as cedar shavings, wood chips, sand and rocks, reflective foil, foam panels, or bubble wrap.
Insulation also helps protect the wood from moisture damage. It keeps the wood warm and dry by preventing heat loss via the convection currents generated when air flows through the construction gaps. Therefore, the more insulation in your sauna, the more heat retention instead of heat loss through radiation or conduction.
Do You Need Sauna Insulation?
If you've already purchased a pre-built sauna or a sauna kit, you must wonder if insulation is included. You might have come across many manufacturers touting the "heat-insulating properties" of the wood used, such as cedar.
Some sauna types, such as barrel sauna or thermally modified saunas are built for the outdoors and do not need insulation for ideal performance. More details about each sauna type are below.
Barrel saunas have several features that allow them to maximize and retain heat without insulation. These include:
Shape: The circular design of barrel saunas causes the warm air to rise continuously and cool air to fall. This implies that the air is constantly moving and being reheated, allowing it to maintain internal temperatures more effectively. Besides, snow and rain do not accumulate due to the rounded roof, making the roof cold.
Area: Even with the same outdoor dimensions, barrel saunas have around 23% less internal area to heat compared to cabin-style or shed saunas.
Wooden Staves: The long wooden planks encircling the cylindrical front and back walls offer some insulation on their own. This is because they're specially designed to fit together more tightly compared to cabin-style saunas.
The process of thermal modification means the wood has been heated to greater than ~356°F (or, 180°C), which releases moisture and then its chemical composition is completely transformed. This induces chemical and structural changes provide endless benefits to your sauna, such as:
increased strength and durability
better stability by lowering the wood’s absorbency capacity
strengthens bio-resistance to protect it from pests and microorganisms
increases heat efficiency
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As the name suggests, pod saunas have a raindrop shape, flat on the bottom and rounded on the top. It is crucial to insulate your pod sauna because it is not as effectively designed as barrel saunas. Although they're somewhat similar to barrel saunas due to their rounded roofs that allow snow and rain to slide off, reducing the cold outdoor temperature, they lack the perks of a fully circular shape. As a result, they lack the best conventional heating. Moreover, they have interior regions similar to the cabin-style saunas.
Cabin saunas usually are rectangular or square and require venting or fans sometimes for the best air circulation patterns for convection. Cabin saunas aren't designed for heat retention despite the construction material used and should be insulated for optimal performance. The staves of a shed sauna aren't as closely fitted as in rounded saunas, with their flat roofs allowing rain and slow accumulation in the winter weather.
Luna saunas are rectangular or square but with rounded corners for aesthetic appeal. They're similar to cabin saunas and require insulation to help retain heat and prevent the formation of condensation.
What Does the R-value Mean for Sauna Insulation?
Now that you know you require insulation, how do you determine the best type of insulation, and what is R-value? R-value measures thermal resistance, or how well a material prevents heat from passing through. A higher R-value implies superior insulation; for an outdoor sauna, the ideal R-values are R26 for ceiling insulation and R19 for walls.
These acclaimed values prevent the warm air from escaping, preventing condensation from forming on your small outdoor sauna walls, and destroying the beautiful wood. Several insulation types are available, but only a few might work for your small outdoor sauna.
Types of Sauna insulation
Numerous insulation types are available at any hardware store, but only a few can work in an outdoor sauna. If you're wondering what insulation type you want to use in your small outdoor sauna, read on for some pros and cons to help you make the ideal choice. Read on!
Paper-backed Fiberglass Rolls
You might be familiar with the puffy pink fiberglass sauna insulation. This is because of their low price point and an R-value of 2.9-3.8 per inch. While it's ideal for heat retention, fiberglass has several disadvantages:
It sheds glass splinters that can damage your lungs and skin. As a result, you must wear protective gear and work with it carefully.
It comes with a paper backing that encourages moisture retention, which is counterproductive to insulating your small outdoor sauna.
If you choose this option, ensure you purchase it "naked" without the paper backing and wear protective equipment.
Insulation boards made of extruded polystyrene foam, polystyrene foam, or polyisocyanurate have high R-values. They are easier to install than cotton or fiberglass insulation. It is advisable not to use expanded polystyrene foam because they contain air bubbles that retain moisture and cause problems.
On the other hand, polyiso boards have R-values between 7.0-8.0 per inch of thickness. They have reflective foils on sides, providing water resistance and heat reflection.
Recycled cotton insulation is made from recycled textiles, mostly jeans explaining its blue coloring. This option is more expensive compared to fiberglass. Still, there is no risk of handling the material or paper. The recycled-cotton insulation has an R-value of 3.0-3.7 per inch, slightly higher than that of fiberglass, which explains the extra cost.
The vapor barriers used in most homes are often made of plastic. However, this wouldn't work in your small outdoor sauna due to the high moisture and temperatures. The best insulation for a sauna is an aluminum foil vapor barrier. It prevents moisture from reaching your wall studs and insulation. It comes with the added advantage of reflecting heat into your sauna.
Applying the vapor barrier over insulation is essential, and it is a crucial step that you shouldn't overlook.
How to insulate a sauna
Your outdoor sauna's ceiling, floor, and walls may require various insulation types and installation methods. So, if unsure, it's best to consult a sauna service professional or manufacturer for further assistance.
If you decide to go the DIY way, read for some specific tips to add insulation to your small outdoor sauna.
It's important to be thorough when insulating your outdoor sauna. But do you need to insulate the floor? It's not always mandatory to insulate your outdoor sauna's floor. Scientifically, warm air rises while cool air falls to the ground.
Thus, the heat won't escape from the floor, but condensation may occur there. However, since your floor isn't made of wood, floor condensation isn't a call for alarm in terms of damaging the sauna.
In most instances, the subfloor is made of concrete, and the ideal flooring option includes non-slip floor mats and tiles.
Much of the heat in a ceiling is lost through the ceiling because warm air rises. This worsens if a layer of snow or cold rain accumulates on the sauna roof. Therefore, your outdoor sauna's ceiling should be insulated to an R-value of 26R and further sheltered by a vapor barrier. It's, therefore, essential to use polyiso boards with a high R-value to meet the 26R requirement.
Don't substitute a vapor barrier with a polyiso, although it has a reflective foil. So, if you decide to use it, it's important to cover it with a foil vapor barrier required for outdoor sauna use.
Although most of the heat is lost via the ceiling, a substantial amount is also lost through the uninsulated sauna walls. As a result, your sauna walls should be insulated to an R-value of 19R, which again calls for polyiso boards. However, you can use recycled cotton batt insulation if you want something more affordable. Remember to cover it with a foil sauna vapor barrier.
In Conclusion, Most Pre-Built Models Will Not Need Sauna Insulation
Insulation is really only necessary if you are building a DIY sauna from scratch, which will make the heat inside more stable, and will prevent moisture from leaking.