This is the fourth post delving into the various systems in a tiny house. For the others, please see the links at the bottom of the introductory post, here. For those that have been waiting for this post for over a year, I apologize, but sometimes life gets in the way, especially when it involves the birth and first few months of life of a perfect baby girl! Regardless, I hope you enjoy!
Here in the United States, winter is nigh upon us. There is an El Niño that is expected to bring cooler and wetter temperatures to the lower half of the country, and warmer temperatures (relatively) for the upper tier of the country. As I try to wrap this post up, there is a massive blizzard walloping the Mid-Atlantic coast, expected to dump 2 + feet of snow in the Northern Virginia and DC area.
Luckily, a well built tiny house provides a cozy, comfortable shelter from the elements, and is extremely cheap to heat. Unlike McMansions, where you can have central heat and air units equivalent in capacity to those needed for a mid-rise office building, tiny houses by virtue of their smallness, need less fuel, and thus less money, to keep warm.
In this post, I will do my best to help you figure out your own path to staying warm in your tiny house.
The number one factor in reducing your heating bill is to make sure your abode is well insulated! Don Hynek, writing in Home Energy Magazine, covers the pitfalls of uninsulated roofs very well. Rather than trying to cover the same information (and probably not as well) I will link to his article instead. (link will open in a new window or tab)
For those that don’t feel like following the link, I will briefly summarize: Snowy conditions do a great job of showing which houses have poor insulation in their roofs. If a house has a solid, even blanket of snow, it is well insulated. If on the other hand, it has bare spots or even looks like the image above, that is a clear indication that there is little to no roof insulation present, and all of the heat in the house is escaping through the roof. The snow and ice at the edges of the roof are ice dams, which is where the melted snow refreezes once it hits a portion of the roof that is not over the uninsulated living / attic space, whichh will ruin your roof, and pose a hazard to people walking below if some of the ice breaks loose and falls.
Aside from the aesthetics (looks) of a tiny house, insulation is one of the factors that sets a tiny house apart from RVs.
A typical RV wall looks like the one to the left. From the outside skin to the inside, you have an outside skin made of aluminum panels, 3/4″ insulation (either spray or foil faced cellular), and an inside plastic interior panel. Total R value of around R5 to R6, if you are lucky. Rather than worry too much about how well insulated the RV is, the manufacturers try to minimize weight and expect the heating and / or air conditioning system to be over-sized to compensate.
A typical tiny house wall is built and insulated like a normal wood construction house wall. From the outside in, you have Siding, building wrap, sheathing, insulation, then drywall or paneling. The depth of the insulation is typically 3 1/2″ inches, and the Total R value ends up being between R15 and R20 when using 2 x 4 lumber. Higher values can be achieved with use of more advanced building systems such as Structurally Insulated Panels (SIPS) and the like, but regardless, normal wood frame construction is at least 3 to 4 times more insulated than typical RV construction.
So, to recap the above, ensure that your tiny home is properly insulated, to include the roof. This is the first step in ensuring that your home is warm and cozy during the cold winter months.
Active versus Passive Heating
There are two broad categories of methods that can be used to heat your tiny house. Active and Passive.
Active heating is what the majority of us are used to: a heating source that uses fuel of some sort that is consumed to generate heat. This can be a wood stove, an electric heater,a gas heater, or even a boiler of some sort providing hot water to a radiator.
Passive heating is a heating source that uses the warmth of the sun to heat your abode. It can range from just having windows that face the sun, to some sort of solar collector that captures the energy from the sun and converts it into heat used to heat water which is then piped into and used to heat the house using either radiators or under floor hydronic radiant heating, or a simple heat exchanger with a fan used to heat the air. The defining characteristic is that the heat used to heat the house is captured from the sun.
I will not delve into how to design a passive heating system with this post, but if you want to find out more, I recommend “Solar Water Heating–Revised & Expanded Edition: A Comprehensive Guide to Solar Water and Space Heating Systems” by Bob Ramlow. It delves into how the systems work and how to maximize the sun’s energy to heat water and your home.
Active heating systems are what most people think of when you start talking heating. I will further subdivide the category into what I will call “Direct” and “Indirect” systems.
Direct Active Systems
A Direct Active System is one where the heating of the house occurs as a direct result of burning fuel of some sort (or in the case of an electric heater, heating up an element). This can be a wood stove, a propane heater, or an electric space heater.
Wood stoves are what many people think of when they think “rustic cabin heat”. Whether it is a box style cook stove or a pot belly stove, these are American classics. Unfortunately, they tend to be polluting, as they do not burn the wood completely.
Modern stoves include a catalytic converter, similar to what your car has, that
helps to ensure that the fuel combusts fully. Aside from polluting less, it also makes the stove more fuel efficient, producing more heat with less fuel. This is not that important at the beginning of winter, when you have a full store of firewood laid aside, but will gain increasing importance as the heating season wears on, and your wood pile dwindles. The key is to look for an EPA certified stove.
Of course, if you are contemplating using a wood stove in a tiny home, you will appreciate multiple functions. In addition to heating, the stove to the right is a cook stove and includes a small oven. There is even an optional water heater attachment available for the stove.
Other options include pellet stoves. These are wood stoves that use compressed sawdust pellets for fuel as opposed to wood logs. Rather than hand loading split logs into the firebox, a wood pellet stove stores the pellets in a storage hopper and has an automatic feeder
that meters the pellets into the firebox at an optimum rate for maximum efficiency. A full hopper load can often last for up to a day or more of continuous burning time. The drawback to pellet stoves however is that they will only use wood pellets, so if you run out, you have to purchase more pellets. Cutting down a tree to feed it is not an option.
Just like with larger houses, gas heat is a good option, especially if you plan to use gas to cook as well. There are two forms commonly available, natural gas and propane.
Natural gas is the gas provided by your utility through a buried hard line. To connect to the system, you have to of course set up an account with the gas company, and have any connection to their system made in accordance with the National Gas Code by a licensed tradesman, and the connection will be inspected by the gas company prior to their approving the connection.
The more common option for tiny houses is Propane. This is because of the portable nature of it, as it is supplied in refillable bottles, ranging from the 15 or 20 pound bottles used for your gas barbeque grill, to 200+ pound tanks set up semi permanently by the gas company.
The smallest and least efficient version of a gas heater is the common camp heater. These small, portable heaters are designed to be hooked up to a camp bottle of propane, but can be easily adapted to hook into a larger bottle or tank.
Many people opt for heating technology used by the boating community.
Manufacturers such as Dickenson Marine have been making high quality, stainless steel heaters and appliances for the marine market since the 1930’s. These are extremely high quality, designed for mobile applications, and for tougher environments than most tiny houses will ever see.
Another option is the blue flame, vent-less propane wall heaters that are common (at least in the South) in rural areas. These work by the flame heating up a ceramic brick, which actually provides the heat radiantly to the space. These are an valid option, but be aware that they release water vapor into the living space, which may not be a good option for a tiny house, especially since most tiny houses are very air tight. This can cause condensation issues inside the house, and ultimately could cause rot.
Electric heat is an option for many tiny houses, especially if they do not plan to use gas for cooking. Options range from the inefficient resistant radiant heaters, to more efficient ceramic heaters, to the most efficient quartz infrared heaters. However, be aware that electric heat is typically the most inefficient option available.
Electric coil heaters work essentially by running an electric current through a thick wire, which heats up due to resistance. A reflector placed behind the heating elements helps to reflect the heat out into the space. They are rated by the number of Watts they require to operate, and are typically used as personal space heaters, due to the power requirements.
Ceramic style electric heaters work similarly, except that the heat generated heats up a ceramic element, while a built-in fan blows air across the element heating the space. Again, the size is typically limited by the power draw of the heater.
Infrared heaters work by heating an element that gives off infrared rays rather than just heat. You probably have encountered them at the entrance to big box stores, where all of a sudden you feel warms on your skin, despite the coolness of the surrounding air. These work by heating the surfaces that the infrared rays hit, not by heating the air itself, which makes them more of a spot heater than an area heater. However, you could aim the heater at a stone or ceramic surface, such as a counter top. This would heat up the surface, which would then heat the air in the space.
There are cabinet style and table top style infrared heaters available as well, which look a bit more subdued, but work the same way.
Another option is to use a kerosene heater. Kerosene is an oil distillate, similar in its heat of combustion to diesel fuel. It is one of the oldest forms of oil product used for heat and light, having been written about by the Persians in the 9th Century. It can be derived from crude oil or coal, but ultimately, it is useful as a heating fuel that can do double duty as a light source if you have a kerosene lantern, albeit a dangerous one: In 1880, close to 40% of all fires in New York City were due to faulty kerosene lanterns, not to mention, a kerosene lantern is THE way to start a barn fire if movies and TV are to be believed.
As a result of the safety issues, many states and jurisdictions have banned the use of kerosene heaters for residential use. However, with proper care in the storage of the fuel, in refueling the heater, the care and maintenance of the heater, and in the operation of the heater, a kerosene heater is definitely a viable heat source, where available, that can do double duty as a stove in a pinch by heating food in a pot placed atop the safety cage (though the manufacturers advise against such use).
Indirect Active Systems
An Indirect Active System is one where the heating of the house occurs through an indirect method, where the heat from the burning of the fuel is captured in some fashion and sent to the living space via a transport medium of some sort such as refrigerant, water, or even air, where the heat is then pulled out of the transport medium and used to heat a space.
Electric Oil Filled Radiator
Many would consider this type of heater to be a direct active system, as you plug it in, it heats up, and you have heat for your room, all from one relatively compact unit. However, this heater is definitely an Indirect heater, as I will explain.
An electric oil filled radiator consists of a metal container filled with some sort of oil (usually mineral oil) with an electric heating element immersed in the oil. It works by the heating element heating the oil up which then releases the heat through the metal container to heat the air. These heaters are actually more efficient than the smaller electric space heaters, as they do not require a fan to blow air across the heating element. Instead, they rely on the natural convection of air in a space, along with the heat retention capacity of the oil to get by with a smaller heating element for the same effective BTUs.
A mini-spit system is a heat pump sized for a single room or small house. These were covered in my tiny house cooling systems post, but I mention them here because, like the heat pump system in a larger house, they can be essentially run in reverse to dump heat into a space as opposed to pulling it out of a space. This double function from one unit is very appealing in a tiny house, as it keeps you from having to buy a separate heating and cooling solution.
Window Unit with Heat Option
Again, window units were covered in my tiny house cooling systems post, however I mention them here as some versions do have a heat option on them. the lower end versions essentially have an electric heating element in them making them just a glorified electric heater, while the higher end versions are heat pumps and can be reversed to pump heat into a space rather than pulling it out. Honestly, I recommend against the version with the electric heating element, as for the price, you can get a better air conditioner and a better electric heater. But the shown heat pump version is decent.
Hot Water (Hydronic) Heating
One option that many tiny housers have not considered is the use of hot water to heat their houses. Traditionally, these were used in large houses and buildings that had a boiler in the basement. The boiler heated up the water, typically turning it into steam, which it then distributed to radiators throughout the building. The radiators transferred heat from the steam into the rooms, and in the process condensed the steam back into water, which was routed back to the boiler to start the process all over again. This system can also be modified to use hot water instead of steam.
A form of this concept has been used in the modern era for radiant floor heating. The water is heated by a boiler, and mixed with the cooled return water before being sent through loops of tubing beneath the floor of a house. Unlike a forced air heating system, which heats air (which is a poor medium for transferring heat) and then blows it into the space, a hydronic system heats the floor surfaces in the space, which then radiate the heat outward, heating the space and occupants. This also keeps the heat down where it is needed, as opposed to fighting against the natural propensity for hot air to rise.
Either of these systems can be adapted to a tiny house, with a little out of the box thinking. If you are using a tank style water heater, you can use that in lieu of the boiler in either of the systems above. This is only possible because tiny houses are, well, tiny. The boiler based systems are sized to heat an entire house or building, whereas the heating requirements of a tiny house can typically be handled by a small hot water heater. It is especially efficient if rather than using electricity or gas to heat the water, you use a hot water solar collector to heat the water, as a the sun can provide all of the heat you need, and then some. Consult a professional with experience with sizing hydronic heating systems for more information.
From experience, I know that having some form of backup heat available is always good to have. You may run out of fuel for your heater, or the electricity may go out from where a limb fell on a line somewhere. As such, I always recommend that people have some sort of alternative heat available to them. It doesn’t need to be capable of replacing your primary source of heat BTU for BTU, rather it merely needs to be capable of keeping your plumbing (and you) from freezing on the coldest night of the year. As such, I recommend that people figure out what sort of alternative heat source meets their needs, both heat wise and storage space wise. Ultimately, you do not want to have to resort to turning your oven / stove burners on to provide emergency heat. It is dangerous, wasteful, and quite honestly only marginally effective.
I hope the above discussion has provided the needed fuel to power your decision as to what sort of heat you will use in your tiny house, and above all, serves to keep you cozy and warm.